taxonID	type	description	language	source
F171B72AFFD0456FFCAAFCF54390FB7F.taxon	etymology	Etymology The generic name was defined by Bonaparte et al. (2006) in honour of Italian philanthropist Dr Giancarlo Ligabue, with the Greek suffix - σαῦρος (sauros), lizard or reptile.	en	Bellardini, Flavio, Coria, Rodolfo A, Pino, Diego A, Windholz, Guillermo J, Baiano, Mattia A, Martinelli, Augustin G (2022): Osteology and phylogenetic relationships of Ligabuesaurus leanzai (Dinosauria: Sauropoda) from the Early Cretaceous of the Neuquén Basin, Patagonia, Argentina. Zoological Journal of the Linnean Society 196 (4): 1333-1393, DOI: 10.1093/zoolinnean/zlac003, URL: https://academic.oup.com/zoolinnean/article/196/4/1333/6553819
F171B72AFFD0456FFCAAFCF54390FB7F.taxon	diagnosis	Diagnosis As for the species.	en	Bellardini, Flavio, Coria, Rodolfo A, Pino, Diego A, Windholz, Guillermo J, Baiano, Mattia A, Martinelli, Augustin G (2022): Osteology and phylogenetic relationships of Ligabuesaurus leanzai (Dinosauria: Sauropoda) from the Early Cretaceous of the Neuquén Basin, Patagonia, Argentina. Zoological Journal of the Linnean Society 196 (4): 1333-1393, DOI: 10.1093/zoolinnean/zlac003, URL: https://academic.oup.com/zoolinnean/article/196/4/1333/6553819
F171B72AFFD04546FCAFFB1E4417FD21.taxon	etymology	Type species and etymology The name of the type species was erected in honour of geologist Dr Héctor Leanza, who reported about the presence of fossils at Cerro de los Leones, Picún Leufú, Neuquén Province, Argentina.	en	Bellardini, Flavio, Coria, Rodolfo A, Pino, Diego A, Windholz, Guillermo J, Baiano, Mattia A, Martinelli, Augustin G (2022): Osteology and phylogenetic relationships of Ligabuesaurus leanzai (Dinosauria: Sauropoda) from the Early Cretaceous of the Neuquén Basin, Patagonia, Argentina. Zoological Journal of the Linnean Society 196 (4): 1333-1393, DOI: 10.1093/zoolinnean/zlac003, URL: https://academic.oup.com/zoolinnean/article/196/4/1333/6553819
F171B72AFFD04546FCAFFB1E4417FD21.taxon	materials_examined	Holotype MCF-PVPH- 233 (Fig. 4 A): a single, large-sized, incomplete and disarticulated sauropod specimen represented by ten maxillary teeth (MCF-PVPH- 233 / 01), a posterior cervical vertebra (MCF-PVPH- 233 / 02), an anterior dorsal vertebra (MCF-PVPH- 233 / 03), two articulated midposterior dorsal vertebrae (MCF-PVPH- 233 / 04 and MCF-PVPH- 233 / 05), two articulated posterior dorsal vertebrae (MCF-PVPH- 233 / 06 and MCF-PVPH- 233 / 07), both scapulae (MCF-PVPH- 233 / 08 and MCF-PVPH- 233 / 09), a left humerus (MCF-PVPH- 233 / 10), a proximal and distal epiphysis of the right humerus (MCF-PVPH- 233 / 11 and MCF-PVPH- 233 / 12), a right metacarpal II (MCF-PVPH- 233 / 13), a right metacarpal III (MCF-PVPH- 233 / 14), a distal epiphysis of the left metacarpal II (MCF-PVPH- 233 / 15), a distal epiphysis of the left metacarpal IV (MCF-PVPH- 233 / 16), a right femur (MCF-PVPH- 233 / 17), a right tibia (MCF-PVPH- 233 / 18), a right fibula (MCF-PVPH- 233 / 19), a right astragalus (MCF-PVPH- 233 / 20) and a nearly complete and articulated right pes, with five metatarsals and three phalanges (MCF-PVPH- 233 / 21 – MCF-PVPH- 233 / 28). Referred specimens MCF-PVPH- 261 (Fig. 4 A): several postcranial elements from the type quarry no. 4 of Ligabuesaurus, consisting of a mid-cervical vertebra (MCF-PVPH- 261 / 16), two posterior cervical vertebrae (MCF-PVPH- 261 / 01 and MCF-PVPH- 261 / 02), an anterior caudal vertebra (MCF-PVPH- 261 / 15), an incomplete dorsal rib (MCF-PVPH- 261 / 17), both coracoids (MCF-PVPH- 261 / 05 and MCF-PVPH- 261 / 06), a distal half of left radius (?) (MCF-PVPH- 261 / 07), a partial left ilium (MCF-PVPH- 261 / 08), both pubes (MCF-PVPH- 261 / 09 – MCF-PVPH- 261 / 11), a left femur (MCF-PVPH- 261 / 12), a proximal epiphysis of the left tibia (MCF-PVPH- 261 / 13) and a proximal epiphysis of the left fibula (MCF-PVPH- 261 / 14). MCF-PVPH- 228 and MCF-PVPH- 908 (Fig. 4 B), a single, large-sized and incomplete sauropod specimen from quarry no. 3, represented by the following associated bones: two articulated posterior cervical vertebrae (MCF-PVPH- 228 / 01 and MCF-PVPH- 261 / 02), an anterior dorsal vertebra (MCF-PVPH- 908), two articulated mid-posterior dorsal vertebrae (MCF-PVPH- 228 / 03 and MCF-PVPH- 228 / 04), six incomplete dorsal ribs (MCF-PVPH- 228 / 05 – MCF-PVPH- 261 / 10) and a right scapula (MCF-PVPH- 228 / 11). MCF-PVPH- 744 (Fig. 4 B), one isolated, almost complete tooth. See the Supporting Information (Table S 1 and Section 1.1.2 ‘ Comments on referred specimens of Ligabuesaurus ’) for considerations about the composition of the type material of Ligabuesaurus.	en	Bellardini, Flavio, Coria, Rodolfo A, Pino, Diego A, Windholz, Guillermo J, Baiano, Mattia A, Martinelli, Augustin G (2022): Osteology and phylogenetic relationships of Ligabuesaurus leanzai (Dinosauria: Sauropoda) from the Early Cretaceous of the Neuquén Basin, Patagonia, Argentina. Zoological Journal of the Linnean Society 196 (4): 1333-1393, DOI: 10.1093/zoolinnean/zlac003, URL: https://academic.oup.com/zoolinnean/article/196/4/1333/6553819
F171B72AFFD04546FCAFFB1E4417FD21.taxon	distribution	Locality and horizon The fossil remains of Ligabuesaurus come from the Cerro de los Leones locality, a hill located ~ 10 km to the southwest of Picún Leufú city, southern Neuquén Province, Patagonia, Argentina (Fig. 1 A, B). The fluvial deposits outcropping in this area were referred to the lower section of the Cullin Grande Member (Martinelli et al., 2007), the upper member of the Lohan Cura Formation (Bajada del Agrio Group, Lower Cretaceous, Albian). The type quarry (no. 4) was opened in the fossiliferous level no. 2 (sensu Martinelli et al., 2007) in the southern flank of the Cerro de los Leones (Fig. 1 C) and 40 m to the east of quarry no. 3, where part of the referred specimen was found (Supporting Information, Table S 1). The sauropod remains were found in laminate mudstones with interbedded fine- to very fine-grained sandstones. These fluvial deposits were dated as Albian and are considered to have been formed in a distal floodplain in semi-arid climatic conditions (Martinelli et al., 2007).	en	Bellardini, Flavio, Coria, Rodolfo A, Pino, Diego A, Windholz, Guillermo J, Baiano, Mattia A, Martinelli, Augustin G (2022): Osteology and phylogenetic relationships of Ligabuesaurus leanzai (Dinosauria: Sauropoda) from the Early Cretaceous of the Neuquén Basin, Patagonia, Argentina. Zoological Journal of the Linnean Society 196 (4): 1333-1393, DOI: 10.1093/zoolinnean/zlac003, URL: https://academic.oup.com/zoolinnean/article/196/4/1333/6553819
F171B72AFFD04546FCAFFB1E4417FD21.taxon	discussion	Comments on original diagnosis In the original description of Ligabuesaurus, Bonaparte et al. (2006) identified four autapomorphies. The first three are listed below with the numbers (1), (2) and (3). The fourth autapomorphy, listed by Bonaparte et al. (2006) as (4) rudimentary prespinal lamina (prsl) on the posterior cervical and anterior dorsal vertebrae, is not used here for the following reasons: in the posterior cervical vertebra MCF-PVPH- 233 / 02 the prsl is not present (Fig. 5 L), whereas in the anterior dorsal vertebra MCF-PVPH- 233 / 03 there is a reduced lamina on the dorsalmost portion of the anterior face of the neural spine (Fig. 5 M). However, in the anterior dorsal vertebra MCF-PVPH- 908 the prsl is not rudimentary but represented by a narrow and prominent lamina, well developed from the base to the apex of the neural spine (Fig. 5 N). Therefore, we consider that the rudimentary prsl on the posterior cervical and anterior dorsal vertebrae is not a pertinent autapomorphy for Ligabuesaurus and exclude it from the diagnosis.	en	Bellardini, Flavio, Coria, Rodolfo A, Pino, Diego A, Windholz, Guillermo J, Baiano, Mattia A, Martinelli, Augustin G (2022): Osteology and phylogenetic relationships of Ligabuesaurus leanzai (Dinosauria: Sauropoda) from the Early Cretaceous of the Neuquén Basin, Patagonia, Argentina. Zoological Journal of the Linnean Society 196 (4): 1333-1393, DOI: 10.1093/zoolinnean/zlac003, URL: https://academic.oup.com/zoolinnean/article/196/4/1333/6553819
F171B72AFFD04546FCAFFB1E4417FD21.taxon	diagnosis	Revised diagnosis Ligabuesaurus leanzai is characterized by the following autapomorphies: (1) laminar and anteroposteriorly compressed neural spines on posterior cervical and anterior dorsal vertebrae that are rhomboid in shape and wider than the vertebral centra; (2) spinoprezygapophyseal laminae in posterior cervical vertebrae forked to form two pairs of laminae: the medial pair unites them towards the top of the neural spine, and the lateral pair form the lateral border of the neural spine; (3) posterior cervical and anterior dorsal vertebrae with low neural arch pedicels, less than onethird of the height of the anterior articular surface; (4) humeral head expanded posteriorly (D’Emic, 2012); (5) quadrangular ventral half of the coracoid in lateral view (Fig. 5 A); (6) fossae on proximoventral faces of metatarsals II and III (D’Emic, 2012); and (7) deep pit on ventrodistal face of pedal phalanx II- 1 (modified from D’Emic, 2012). With regard to (4), (6) and (7), in the extended contribution on the early evolution of Titanosauriformes, D’Emic (2012; appendix 4) also provided a diagnosis for Ligabuesaurus, identifying five autapomorphies, some of which are not included in the diagnosis to represent morphological features with a wide distribution within Sauropoda. In this sense, the distal scapular blade with rounded dorsal expansion (autapomorphy 1; D’Emic, 2012) is a condition that Ligabuesaurus shares with several Titanosauriformes (e. g. Brachiosaurus Riggs, 1903, Brontomerus Taylor, Wedel & Cifelli, 2011, Euhelopus Romer, 1956, Giraffatitan Paul, 1988, Rukwatitan Gorscak et al., 2014), hence it is excluded from the diagnosis. Likewise, the gracile humerus of Ligabuesaurus (autapomorphy 3; D’Emic, 2012) is a plesiomorphic condition that is also present in several sauropods, such as Alamosaurus Gilmore, 1922, Chubutisaurus Del Corro, 1975, Europasaurus Mateus et al. in Sander et al., 2006, Giraffatitan, Patagosaurus Bonaparte, 1979, Rinconsaurus Calvo & González Riga, 2003 and Wintonotitan Hocknull et al., 2009. In contrast, we agree with D’Emic that the deep pit on the ventrodistal face of the pedal phalanx represents an autapomorphy of Ligabuesaurus (autapomorphy 5; D’Emic, 2012), but we have reconsidered the pedal element (MCF-PVPH- 233 / 28) as a phalanx II- 1 and not a I- 1 (contra D’Emic, 2012). However, also in the phalanx I- 1 (MCF-PVPH- 233 / 26) there is a ventrodistal vascular foramen, but it is small and poorly preserved, hence it is not included in the present diagnosis.	en	Bellardini, Flavio, Coria, Rodolfo A, Pino, Diego A, Windholz, Guillermo J, Baiano, Mattia A, Martinelli, Augustin G (2022): Osteology and phylogenetic relationships of Ligabuesaurus leanzai (Dinosauria: Sauropoda) from the Early Cretaceous of the Neuquén Basin, Patagonia, Argentina. Zoological Journal of the Linnean Society 196 (4): 1333-1393, DOI: 10.1093/zoolinnean/zlac003, URL: https://academic.oup.com/zoolinnean/article/196/4/1333/6553819
F171B72AFFD04546FCAFFB1E4417FD21.taxon	description	Minimum number of individuals In Bonaparte’s fieldbook notes, he mentioned the presence of size differences among some fossil remains from quarry no. 4 (Supporting Information, Fig. S 2 B; ‘ los fémures parecieron ser de distinto tamaño / femora seemed to be of different size’), arguing that more than one sauropod individual would be buried in it (J. F. Bonaparte pers. comm., 2014). In order to estimate the minimum number of individuals from quarry no. 4, we consider the repetition of same-size elements and the presence of repeated elements with different sizes, with a special focus on the long bones (e. g. femora and humeri). In this context, the right femur MCF-PVPH- 233 / 17 is incomplete, lacking the proximal epiphysis, and exhibits strong anteroposterior compression for plastic diagenetic alterations. In contrast, the slightly shorter but almost complete left femur MCF-PVPH- 261 / 12 is well preserved and not compressed like the right femur. Therefore, the small difference in size between the femora is more likely to be attributable to preservational conditions than to the presence of multiple individuals at the site. Furthermore, the left femur was found partly articulated with the almost complete pelvis (Fig. 3) and the proximal epiphysis of the left tibia and fibula (MCF-PVPH- 261 / 13 - 14), which show better preservational conditions than the complete but strongly altered and fractured right fibula and tibia (MCF-PVPH- 233 / 18 and MCF-PVPH- 233 / 19). Likewise, most of the cervical and dorsal vertebrae are almost complete, but show some deformations, especially on the centra (e. g. MCF-PVPH- 233 / 04 and MCF-PVPH- 233 / 05), whereas others are poorly preserved or exhibit strong transverse compression (e. g. MCF-PVPH- 233 / 06 and MCF-PVPH- 233 / 07). These conditions suggest that different taphonomic events would have altered the sauropod fossil bones of quarry no. 4. In this sense, the left humerus MCF-PVPH- 233 / 10 is almost complete but greatly altered by fractures and compressions, whereas the proximal (MCF-PVPH- 233 / 11) and distal (MCF-PVPH- 233 / 12) ends of the right humerus are well preserved, with the result that it is slightly bigger than the left humerus. In the same way, there are small size and morphological discrepancies between both coracoids, both scapulae and both pubes that are here imputed to the different preservational conditions rather than to the occurrence of multiple individuals. Regarding the taphonomic context at site no. 4, the arrangement of the bones was reconstructed, in part, on the basis of the original pictures, notes and sketches by Bonaparte and collaborators (Supporting Information, Fig. S 2). The reconstructed map shows that most of the bones referred to the anterior part of the skeleton (e. g. coracoids, scapulae and humeri) were found in the eastern sector of the site, whereas the pelvis, caudal vertebrae and some hindlimb elements came from the western sector (Fig. 3). This scenario, with the absence of repeated elements, congruent size-ratio values amongst elements and taphonomic arrangement of the bones would suggest that the bone assemblage from quarry no. 4 corresponds to a single sauropod individual. In this sense, further preparation of Ligabuesaurus material and the revision of the complete set of collected bones allowed us to consider that a single sauropod carcass suffered poor preburial transport and disarticulation in the site. Body mass estimation Sauropod dinosaurs were the dominant mega herbivores during the greater part of Mesozoic, being the principal modellers of the terrestrial ecosystem, at least in terms of biomass, until the global extinction of the end of the Cretaceous (e. g. Upchurch et al., 2004; Sander et al., 2011; Carballido et al., 2017). In order to reconstruct different palaeobiological aspects of sauropods and of other extinct terrestrial quadrupeds, the estimation of body mass represents a principal measure of body size to analyse palaeoecological implications of the faunal composition of ancient ecosystems (Campione & Evans, 2012). In recent years, different palaeontological studies have focused on developing alternative methodologies to approximate the body mass of extinct vertebrates, including gigantic theropod and sauropod dinosaurs (Campione & Evans, 2012; Sellers et al., 2012; Bates et al., 2015, 2016). In particular, Campione & Evans (2012) suggested a new scaling method to relate stylopodial circumferences with body mass (BM), using the humeral and femoral circumferences (CH and F, respectively) of different quadrupedal taxa. Thus, applying that scaling equation (i. e. logBM = 2.754 × logCH + F − 1.097) for Ligabuesaurus recovers a body mass of 23 tonnes (± 5.9 tonnes, considering the mean percentage prediction error calculated by Campione & Evans, 2012), which is an estimate similar to other giant neosauropods (Benson et al., 2014), such as Antarctosaurus von Huene, 1929 (23 tonnes), Diamantinasaurus Hocknull et al., 2009 (23 tonnes), Apatosaurus parvus Peterson & Gilmore, 1902 (24 tonnes) and Opisthocoelicaudia Borsuk-Białynicka, 1977 (25 tonnes). Moreover, the new estimation results in 3000 kg more than (> 15 %) the body mass value given by Benson et al. (2014), which is based on the deformed, and thus smaller, right femur MCF-PVPH- 233 / 17. In contrast, the new estimate of body mass is much lower than the colossal lognkosaurian Patagotitan Carballido et al., 2017 (69 tonnes), the derived titanosaurian Dreadnoughtus Lacovara et al., 2014 (59 tonnes) or the basal lognkosaurian Futalognkosaurus Calvo et al., 2007 (38 tonnes), but significantly much larger than other Patagonian taxa, such as the basal titanosaurian Epachthosaurus Powell, 1990 (13 tonnes), the rebbachisaurids Comahuesaurus Carballido et al., 2012 and Limaysaurus Salgado et al., 2004 (12 tonnes) or the derived lithostrotians Neuquensaurus Powell, 1992 (6.1 tonnes) and Saltasaurus Bonaparte & Powell, 1980 (5.8 tonnes). In contrast, the estimate recovered by Carballido et al. (2017) for Chubutisaurus (29 tonnes), suggests that different large-sized somphospondylans lived in different basins of south-western Gondwana, at least during the latest Early Cretaceous. E, Opisthocoelicaudia ZPAL-MgD-I / 48; F, Dreadnoughtus MPM-PV- 1156; G, Tapuiasaurus MZSP-PV- 807; H, Uberabatitan CPP- 1109 - UrHo; I, Suuwassea ANS 21122; J, Patagotitan MPEF-PV- 3400 / 24; K, Zby ML 368. L – N, line drawings of the posterior cervical vertebra MCF-PVPH- 233 / 02 (L) and anterior dorsal vertebrae MCF-PVPH- 233 / 03 (M) and MCF-PVPH- 908 (N), showing the development of the prespinal lamina on the anterior surface of the neural spine (green triangle). B – K modified from González Riga et al. (2019). Not to scale. Scale bar: 10 cm in L – N. Campione (2017) proposed a new quadratic model to mitigate the overestimation of body mass (between 10 and 20 %) that occurs when the scaling models are applied, especially to very large extinct vertebrates, such as giant sauropods. Three-dimensional skeletal reconstructions are now also widely used to approximate the body volume of different sauropod taxa (Sellers et al., 2012; Bates et al., 2015, 2016; Carballido et al., 2017), representing an alternative model to the scaling and quadratic approaches when the femoral and humeral circumferences are not available. However, volumetric analyses are clearly subject to different uncertainties related to the amount of reconstructed soft tissue (Campione & Evans, 2012; Carballido et al., 2017), and large discrepancies from the scaling model have been detected for several sauropod body mass estimations (Bates et al., 2015; Carballido et al., 2017). It is important to account for the limitations of each chosen model, especially when the resulting body mass is used to reconstruct palaeobiological properties or make comparisons amongst different taxa to analyse palaeoecological implications. Although an exhaustive body mass estimation of Ligabuesaurus was not the aim of the present contribution, the new material here described allows a more accurate body mass approximation to be made than previously possible, providing new data on the sauropod faunal composition of the Cerro de los Leones ecosystem during the Albian. Description and comparisons Teeth (Figs 6, 7): The only cranial elements referred to Ligabuesaurus are represented by teeth, including one block with a set of ten elements partly included in the matrix (MCF-PVPH- 233 / 01) and one isolated but nearly complete tooth (MCF-PVPH- 744). With respect to MCF-PVPH- 233 / 01 (Fig. 6 A), this element was considered as a poorly preserved right maxilla in the original description (Bonaparte et al., 2006). However, we consider MCF-PVPH- 233 / 01 as new evidence of isolated tooth rows (sensu Wiersma & Sander, 2016), an exceptional preservation condition of tooth sets recorded in some dinosaur specimens, especially sauropods. Following Wiersma & Sander (2016), this condition is likely to be related to the presence of a sort of connective tissue that allows preservation of several teeth in anatomical arrangement in spite of loss of mandibular or dentary bone tissue during the diagenetic process, as seen in Europasaurus, Giraffatitan and Phuwiangosaurus (Buffetaut & Suteethorn, 1999; Sander et al., 2006; Kosch et al., 2014). MCF-PVPH- 233 / 01 includes ten functional teeth, many of which preserve parts of roots and crowns in lingual view, and a few indeterminate fragments that probably represent remains of other teeth (Fig. 6 A). However, owing to the poor preservational conditions, it is difficult to discern whether these fragments belong to other functional teeth or replacement teeth. For descriptive purposes, the teeth are numbered from one through ten, from left (anterior) to right (posterior) in lingual view. The teeth are almost equally spaced and in a parallel arrangement, and the apical portions of teeth 3, 5, 6 and 7 are exposed in both lingual and labial views (Fig. 6 A). In contrast, the isolated tooth MCF-PVPH- 744 is almost complete and well preserved, although it lacks much of the root and part of the enamel surface on most of the labial face (Fig. 6 B – F). Comparisons with complete and well-preserved tooth rows of other neosauropods (e. g. Camarasaurus Cope, 1877 and Giraffatitan; Cope, 1877; Janensch, 1914; Wiersma & Sander, 2016), where the wear facet is on the lingual facet (i. e. the concave surface) and a lingual groove is located mesially (Smith & Dodson, 2003), we tentatively consider MCF-PVPH- 233 / 01 as right maxillary teeth and MCF-PVPH- 744 as a left maxillary tooth. In Ligabuesaurus, the teeth are broad crowned and of the brachiosaurid type (sensu Barrett & Upchurch, 2005), as in several Titanosauriformes (e. g. Euhelopus, Fukuititan Azuma & Shibata, 2010, Giraffatitan and Sauroposeidon Wedel, Cifelli & Sanders, 2000; Janensch, 1914; Rose, 2007; Wilson & Upchurch, 2009; Azuma & Shibata, 2010). The root is elliptical in cross-section and slightly compressed labiolingually, whereas the crown is ‘ cone-chisel-like’ (sensu Calvo, 1994). Furthermore, the crown is D-shaped in crosssection, whereby the labial surface is mesiodistally convex and the lingual face is straight to slightly concave in distal view, as in most of Titanosauriformes (Wilson & Sereno, 1998; Upchurch et al., 2004). In labial view, the mesial and distal margins of the root are straight and parallel, without a mesiodistal expansion to the cervix (Smith & Dodson, 2003), whereas the mesial margin of the crown is inclined distally, resulting in the the apex being directed slightly anterior (see tooth 3 in Fig. 6 A). In the lingual face of MCF-PCPV- 744, a smooth cingular cusp (cc; Fig. 6 F) is present at the base of the distal margin of the crown. This bulbous prominence is similar to the cingular cusps seen in Yongjinglong (Li et al., 2014), some mamenchisaurids (Moore et al., 2020), ‘ Asiatosaurus ’ (nomen dubium; Osborn, 1924) and Euhelopus (Wilson & Upchurch, 2009), and in some sauropods from La Cantalera and Galve in Spain and from the Yixian Formation in China (Canudo et al., 2002; Barrett & Wang, 2007). The amount, morphology and position of the cingular cusps varies among these forms and is likely to depend on the ontogenetic stage of the specimen (Barrett & Wang, 2007). Consequently, the presence of the cingular cusp on the lingual surface of the maxillary tooth MCF-PVPH- 744, but not in MCF-PVPH- 233 / 01, depends on the poorly preserved conditions of the maxillary teeth or on different ontogenetic stages amongst Ligabuesaurus specimens. On the lingual face of tooth 4 and in MCF-PVPH- 744, an apicobasally directed mesial groove is well marked along the apical half of the crown (Fig. 6 B). The mesial groove is slightly deeper apicomesially and is bounded apically by the wear facet. In contrast, labial grooves, lingual ridges and carinae are not present in Ligabuesaurus. The enamel surface is rough and wrinkled, with several small grooves and ridges, often oriented parallel to the main axis of the tooth. These grooves and ridges are more clearly marked on the labial and lingual faces, where there are no signs of wear. Contrary to Bonaparte et al. (2006: 367), pseudodenticles and apical wear facets are not observed in MCF-PVPH- 233 / 01. In MCF-PVPH- 744, two wear facets are present: an apical teardrop-shaped wear facet and a marginal wear facet on the mesial margin of the tooth (Fig. 6 B, E). The apical wear facet is composed of a wide, rounded distal portion and a labiolingually compressed and commalike segment on the mesial margin of the apex. In the mesiodistal view, the apical wear facet is lingually inclined, forming an angle> 45 ° to the long axis of the tooth (Fig. 6 E, F). The tooth was worn down apically, hence the dentine is widely exposed in the apical wear facet. Furthermore, the enamel presents a differential thickness in apical view, being slightly thicker in the labial and lingual faces than in the distal margin (Fig. 6 C). In the apical portion of MCF-PVPH- 744, scanning electron microscopy images of the microwear surface show that both enamel and dentine surfaces are altered by several pits, fine scars and coarse grooves (Fig. 7). The pits are represented by small and rounded perforations that are mostly distributed in the distal portion of the apical wear facet (Fig. 7 α). In contrast, the fine scars are widely cross-linked and recorded in the major part of the apical surface of the tooth, whereas the coarse grooves are represented by deeper and elongated scars, which are more abundant on the distal portion of the apical wear facet (Fig. 7 α, β). The coarse grooves are oriented mesiodistally in the lingual portion, whereas they are shorter, deeper and directed labiolingually in the labial half of the apical wear facet. The microwear pattern of MCF-PVPH- 744 is consistent with that known in other Titanosauriformes with ‘ cone-chisel-like’ teeth (e. g. cf. Euhelopus, Giraffatitan and Sauroposeidon; Janensch, 1914; Barrett & Wang, 2007; Rose, 2007), where a ‘ tooth-to-food’ attrition and a combination of ortal and propalinal jaw movements would have caused the teardrop-shaped apical wear facet and the cross-linked scars and grooves (Whitlock, 2007). A smooth and apicobasally oriented marginal wear facet is present on the mesial margin of the lingual surface of the crown (mwf; Fig. 6 E, F). In mesial view, a gently prominent step divides the wider apical half of the mesial wear facet from the slightly deeper basal half. In the marginal wear facet, the enamel surface is smooth, with no dentine exposed. Considering its basal position, the marginal wear facet is here considered as a result of ‘ tooth-to-tooth’ attrition between teeth of opposite jaws (e. g. García & Cerda, 2010; Gallina & Apesteguía, 2011; Díez Díaz et al., 2012 a, b, 2013 b, 2014). This condition suggests some degree of tooth row overlapping in Ligabuesaurus, as in sauropods with only one of either the mesial or distal facet extending along the margin of the crown (oblique facet tooth, sensu Buffetaut & Suteethorn, 2004; or tooth type 3 sensu Saegusa & Tomida, 2011), such as in Amygdalodon Cabrera, 1947 (Carballido & Pol, 2010), Camarasaurus (McIntosh et al., 1996; Wiersma & Sander, 2016), Europasaurus (Marpmann et al., 2015), most nontitanosaurian Titanosauriformes (e. g. Giraffatitan, Phuwiangosaurus and Sauroposeidon; Janensch, 1914, Martin et al., 1994, Rose, 2007; Suteethorn et al., 2009) and some titanosaurians (e. g. Lirainosaurus Sanz et al., 1999; Díez Díaz et al., 2012 b). Axial skeleton Cervical vertebrae (Fig. 8 – 11): The preserved cervical series of Ligabuesaurus includes three almost complete elements and three cervical centra (Supporting Information, Table S 1). Middle cervical vertebra Cv- 07? (Fig. 8): This vertebra (MCF-PVPH- 261 / 16) preserves most of the centrum, part of the right parapophysis and both diapophyses and prezygapophyses. On the basis of the anteroventral position of the parapophyses on the centrum, the high length-to-height ratio of the centrum, the low and lateral positions of the prezygapophyses and diapophyses, and the comparisons with articulated cervical series of different neosauropod taxa (e. g. Brachiosaurus, Erketu Ksepka & Norell, 2006, Haplocanthosaurus Hatcher, 1903, Qiaowanlong You & Li, 2009, Sauroposeidon and Yunmenglong Lü et al., 2013; Hatcher, 1903; Janensch, 1950; Wedel et al., 2000 a, b; Ksepka & Norell, 2006, 2010; You & Li, 2009; Lü et al., 2013), we tentatively consider MCF-PVPH- 261 / 16 as the seventh cervical vertebra of Ligabuesaurus. The centrum is opisthocoelous and slightly wider than tall in anterior and posterior views, as in Futalognkosaurus, Mendozasaurus González Riga, 2003 and Puertasaurus Novas et al., 2005 (González Riga, 2003; Novas et al., 2005; Calvo et al., 2007). In ventral view, the lateral margins of the centrum are anteroposteriorly concave, hence the centrum is hourglass shaped (Fig. 8 A, B). The centrum is relatively long, as reflected by the elongation index (EI = 5.25; sensu Wedel et al., 2000), which is one of the highest among Sauropoda (e. g. Apatosaurus Marsh, 1877 EI = 3.7, Brachytrachelopan Rauhut et al., 2005 EI <1, Camarasaurus EI = 2.9, Diplodocus Marsh, 1878 EI = 4.9, Euhelopus EI = 4.0 and Mamenchisaurus Young, 1954 EI = 2.9; McIntosh et al., 1996; Wedel et al., 2000; Whitlock, 2011; Taylor & Wedel, 2013), being lower only than Barosaurus Marsh, 1890 (EI = 5.4), Giraffatitan (EI = 5.4), Erketu (EI = 7.0) and Sauroposeidon (EI = 6.1) (Janensch, 1914; Wedel et al., 2000; McIntosh, 2005; Ksepka & Norell, 2006). However, the value of the average elongation index (aEI, asssessed as the centrum length, excluding the anterior articular ball, divided by the mean average value of the posterior articular surface width and height; sensu Chure et al., 2010) observed in MCF-PVPH- 261 / 16 is relatively low (aEI = 2.4), as in many turiasaurians, dicraeosaurids, some rebbachisaurids and derived titanosaurians considered as short-necked sauropods (Mannion et al., 2019 a), which contrasts with the EI signal. This incongruence between the EI and aEI values would depend on some types of diagenetic deformations of MCF-PVPH- 261 / 16, which would have altered the cross-sectional shape of the vertebra. In this sense, the cervical centrum is strongly elongated and low in MCF-PVPH- 261 / 16, suggesting an overestimation of the EI value, although minimal, owing to compressive lithostatic alterations. Taking into account the total length of that vertebra, we consider MCF-PVPH- 261 / 16 to be more suitable for a long-necked than a short-necked sauropod. In MCF-PVPH- 261 / 16, the ventral surface of the centrum is concave both anteroposteriorly and transversely, as in several turiasaurians, diplodocoids and Titanosauriformes (Upchurch, 1998; Upchurch et al., 2004). However, the concavity on the anterior half of the ventral surface is slightly deeper than on the posterior half. Furthermore, a pair of thin, parallel but poorly preserved ridges run anteroposteriorly on the posterior part of the centrum (pvr; Fig. 8 B), as in Brasilotitan Machado et al., 2013, Overosaurus Coria et al., 2013 and Yunmenglong (Coria et al., 2013; Lü et al., 2013; Machado et al., 2013). In lateral view (Fig. 8 C), on the anterior half of the centrum, an inclined and thick bone septum divides the large and deep lateral pleurocoel from a low and shallow anterior accessory pneumatic opening, as in several Neosauropoda (Wilson & Sereno, 1998). The anterior accessory fossa is slightly compressed dorsoventrally owing to the presence of the parapophyses, which are preserved in part and placed ventrally on the anterolateral margins of the centrum. There are fragments of the neural arch pedicels above the anterodorsal surface of the centrum and neural canal (Fig. 8 A). Dorsal to the neural canal, a fragment of bone is tentatively referred to a ventral portion of the intraprezygapophyseal lamina (tprl; Fig. 8 A). The diapophyses are well preserved, being laterally projected and wider than the centrum in anterior view. In lateral view, they are located above the middle of the centrum and dorsally to the prezygapophysis (Fig. 8 C). In cross-section, the diapophyses are rectangular, being slightly compressed dorsoventrally and extended anteroposteriorly. Ventrally (Fig. 8 B), the diapophysis connects with the centrum through a robust anterior centrodiapophyseal lamina (acdl) and a shorter posterior centrodiapophyseal lamina (pcdl). A long spinodiapophyseal lamina (spdl) runs medially towards the neural spine region from the posterodorsal margin of the diapophysis, whereas a robust prezygodiapophyseal lamina (prdl) links the diapophysis with the prezygapophysis (Fig. 8 A). In anterior view, the prezygapophyses are at the level of the dorsal margin of the condyle and are projected dorsolaterally, whereas in dorsal view they exceed the anterior surface of the centrum. The prezygapophyses are oval in cross-section, expanded transversally and slightly compressed dorsoventrally. The articular surfaces are oval and laterally concave. A spinoprezygapophyseal lamina (sprl) that runs towards the missing neural spine arises from the dorsal face of the prezygapophyses. In ventral view, the centroprezygapophyseal laminae (cprl) connect the prezygapophyses with the anterodorsal margin of the centrum (Fig. 8 B). MCF-PVPH- 261 / 16 lacks most of the neural arch, including the neural spine. However, part of the basal neural arch is preserved, fused to the centrum. The sprl and centropostzygapophyseal lamina (cpol) are arranged in ‘ X’ when seen in dorsal view (Fig. 8 A), as in some derived titanosaurians, such as Alamosaurus, Rapetosaurus Curry Rogers & Forster, 2001 and Uberabatitan Salgado & Carvalho, 2008 (Gilmore, 1922; Lehman & Coulson, 2002; Salgado & Carvalho, 2008; Curry Rogers, 2009; Silva Junior et al., 2021). Posterior cervical vertebra Cv- 09? (Fig. 9): This incomplete axial element (MCF-PVPH- 261 / 01) preserves the major part of the centrum, part of both parapophyses and the basal portion of the left prezygapophysis. Morphological comparisons with well-preserved sauropod cervical series (e. g. Brachiosaurus, Euhelopus, Haplocanthosaurus and Rapetosaurus; Hatcher, 1903; Janensch, 1950; Curry Rogers, 2009; Wilson & Upchurch, 2009) allow us to consider MCF-PVPH- 261 / 01 as a posterior cervical vertebra, probably the ninth, especially taking into account the anteroventral position of the parapophyses, the anterolaterally directed prezygapophyses that do not exceed the anterior articular surface of the centrum and the low length-to-height ratio of the centrum. The centrum is opisthocoelous, with both anterior and posterior articular surfaces extended transversally and slightly compressed dorsoventrally in anterior and posterior views (Fig. 9 A, B). The ventral surface of the centrum is shallow and anteroposteriorly concave, without a central keel or lateral ridges. In lateral view, an elongated and dorsoventrally compressed pneumatic fossa opens in the lateral surface of the centrum (Fig. 9 C); owing to the poor preservational conditions, a septum seems to be absent. However, a bone fragment divides a narrow posterior portion and a wider and deeper anterior fossa. The parapophyses are placed in the anteroventral margin of the centrum, close to the anterior articular surface. Furthermore, they are directed laterally in anterior view and are oval in cross-section (Fig. 9 A). In MCF-PVPH- 261 / 01, the anterior opening of the neural canal is narrow and quadrangular, delimited laterally by basal portions of neural pedicels that are preserved only in the anterodorsal margin of the bone. Posterior cervical vertebra Cv- 10? (Fig. 10): This element (MCF-PVPH- 261 / 02) is represented by an incomplete cervical centrum and part of the neural arch, including the left prezygapophysis and the basal portion of the right prezygapophysis and diapophysis. Considering the relative position of the parapophysis in the anterolateral centrum, the anterodorsal orientation of the prezygapophysis in lateral view and the general proportions of the centrum, MCF-PVPH- 261 / 02 is considered as a posterior cervical vertebra, tentatively the tenth of the series. The anterior articular surface is convex and slightly more dorsally prominent in lateral view (Fig. 10 C), whereas it is wider than tall in anterior view (Fig. 10 A), as in the posterior cervical vertebrae of several Titanosauriformes (e. g. Rapetosaurus, Sauroposeidon, Sibirotitan Averianov et al., 2017 and Uberabatitan; Rose, 2007; Salgado & Carvalho, 2008; Curry Rogers, 2009; Averianov et al., 2018; Silva Junior et al., 2021). In lateral view, the basal portion of the right parapophysis is present in the ventrolateral margin of the centrum (Fig. 10 C). Dorsally to the parapophysis open two pneumatic fossae, a small and oval anterior fossa and an anteroposterior enlarged posterior fossa. The latter fossa is slightly deeper anteriorly and is compressed dorsoventrally in its posterior half (Fig. 10 C). The posterior articular surface is concave, compressed dorsoventrally in posterior view and slightly more ventrally prominent in lateral view (Fig. 10 B, C). The neural canal is evident only in anterior view, being low and triangular in shape (Fig. 10 A). In anterior view, the prezygapophyses are long and dorsolaterally directed, whereas they are inclined in a slightly dorsal direction in lateral view (Fig. 10 C), exceeding the anterior articular surface of the centrum. In anterior view, part of the intraprezygapophyseal lamina (tprl) and left centroprezygapophyseal lamina (cprl) are preserved. The basal portion of the diapophysis is present on the right lateral side, which is extended anteroposteriorly and slightly inclined dorsolaterally. Posterior cervical vertebrae Cv- 12? and Cv- 13? (Fig. 11): Among the new postcranial elements referred to Ligabuesaurus that came from quarry no. 3, there are two articulated and almost complete posterior cervical vertebrae (MCF-PVPH- 228 / 01 and MCF-PVPH- 261 / 02), which lack part of the ventral surfaces and the neural spines. These vertebrae are tentatively considered as the 12 th and 13 th cervical vertebrae, showing the parapophyses in the anterolateral margins of the centra, long and laterally directed diapophyses and anteriorly directed prezygapophyses, as seen in posterior cervical vertebrae of other Titanosauriformes (Euhelopus, Overosaurus and Trigonosaurus Campos et al., 2005; Campos et al., 2005; Wilson & Upchurch, 2009; Coria et al., 2013). Considering that the anterior articular surface of MCF-PVPH- 228 / 01 is convex and the posterior one of MCF-PVPH- 228 / 02 is concave, both cervical centra are interpreted as opisthocoelous. In lateral view, the centra are longer than high, whereas they are longer than wide in dorsal view. Both anterior and posterior articular surfaces are slightly wider than high, being compressed dorsoventrally and oval in shape. The parapophyses are incomplete, but their basal portions are preserved in the anterolateral margins of the centra and are oval in shape and laterally directed. In MCF-PVPH- 228 / 02, the parapophyses are slightly more dorsally positioned than in the preceding vertebra, MCF-PVPH- 228 / 01. The anterior opening of the neural canal is small and oval, being slightly compressed dorsoventrally and delimited laterally by low neural pedicels. In lateral view, the prezygapophyses are projected anterodorsally, but do not exceed the anterior border of the articular surface of the centra. In MCF-PVPH- 228 / 01, the prezygapophyses bear wide and flat articular surfaces, which are rectangular in shape and inclined in a slightly medial direction in anterior view (Fig. 11). Both prezygapophyses are linked by a prominent and robust intraprezygapophyseal lamina, which roofs the entrance of the neural canal. In both cervical vertebrae, a prezygadiapophyseal lamina (prdl) runs posteriorly from the ventrolateral margin of prezygapophyses to the dorsal surface of the diapophyses (Fig. 11). Only the basal portions of the spinoprezygapophyseal laminae (sprl) are preserved dorsally to the prezygapophyses. The neural spines are not preserved. The postzygapophyses are tall and directed posterolaterally in dorsal view. In lateral view, a thin postzygodiapophyseal lamina (podl) links the ventrolateral margin of the postzygapophysis with the dorsal surface of the diapophysis. Ventral to the postzygapophyses, the low and robust cpol delimits the neural canal laterally, constituting part of the neural pedicels of the vertebra (Fig. 11). The diapophyses are long and directed dorsolaterally, being longer than the centrum width in anterior and posterior views. However, in MCF-PVPH- 228 / 02 the diapophyses are slightly shorter, dorsally inclined and proximally narrower than the preceding element (MCF-PVPH- 228 / 01). A short spinodiapophyseal lamina runs dorsally from the diapophyses to the lateral portion of the neural arch. Two robust laminae link the diapophyses with the centrum: the acdl and the pcdl. The acdl is prominent, as in several Sauropoda (Wilson, 1999), and runs ventrally towards the anterodorsal margin of the centrum, whereas the pcdl is long and reaches the posterior half of the centrum. Posterior cervical vertebra Cv- 14? (Fig. 12; Supporting Information, Fig. S 3): Considering that the cervical vertebra of Ligabuesaurus (MCF-PVPH- 233 / 02) was extensively described and figured by Bonaparte et al. (2006), only its general morphology and most remarkable features, especially concerning the neural fossae, are described below. MCF-PVPH- 233 / 02 shares different morphological conditions with the last cervical vertebrae of other neosaurops (e. g. Euhelopus, Haplocanthosaurus, Overosaurus and Trigonosaurus; Hatcher, 1903; Campos et al., 2005; Wilson & Upchurch, 2009; Coria et al., 2013), such as a prominent parapophysis on the anteroventral portion of the centum, low prezygapophyses close to the dorsal margin of the centrum, tall and dorsolaterally directed postzygapophyses, and a tall and anteroposteriorly compressed neural spine. Therefore, we consider MCF-PVPH- 233 / 02 as the last vertebra, probably 14 th, of the cervical series of Ligabuesaurus. In MCF-PVPH- 233 / 02, the centrum is incomplete posteriorly. In anterior view, it is wider than tall (Fig. 12 A), where the articular surface is convex and dorsoventrally compressed. The ventral surface is anteroposteriorly concave and smooth, without lateral crests or a medial keel. On the right lateral surface opens an elongated pleurocoel, which is divided by a septum into a triangular and deep anterior subfossa and a slightly wider but shallower posterior subfossa (Fig. 12 C). In the anterior subfossa, an accessory septum divides a short dorsal chamber from a deeper ventral one. The parapophyses are in the anteroventral margin of the centrum and project laterally in dorsal view. In anterior view, the neural pedicels are dorsoventrally low, less than one-third of the height of the anterior articular surface (Fig. 12 A). The anterior opening of the neural canal is oval and compressed dorsoventrally. The prezygapophyses are projected anterolaterally, exceeding the lateral margins of the centrum and the anterior articular surface in dorsal view. The diapophyses are long, oval in cross-section and directed laterally, exceeding the prezygapophyses in anterior view. In posterior view, the postzygapophyses are projected lateroventrally and positioned more dorsally than diapophyses, exceeding the lateral surface of the centrum (Fig. 12 B). In MCF-PVPH- 233 / 02, the neural spine is on the posterior half of the centrum, with a gentle posterior inclination in lateral view (Fig. 12 C), as in some titanosaurians (e. g. Futalognkosaurus, Quetecsaurus González Riga & Ortiz David, 2014 and Rapetosaurus; Calvo et al., 2007; Curry Rogers, 2009; González Riga & Ortiz David, 2014). The spine is tall, more than two times the height of the centrum, transversally wide, exceeding the lateral surface of the centrum and rhomboidal in anterior view, as in Bonitasaura Apesteguía, 2004, Futalognkosaurus and Mendozasaurus (González Riga, 2003; Calvo et al., 2007; Gallina & Apesteguía, 2015; González Riga et al., 2018). The neural spine did not preserve a prespinal lamina, but there is an incomplete and low postspinal lamina (posl), at least up to the proximal half of the posterior neural spine (Fig. 12 B). In the anterior half of the centrum, a triangular and shallow prezygocentrodiapophyseal fossa (prcdf) opens between the acdl and the cprl (Supporting Information, Fig. S 3 A), as in several neosauropods (Wilson et al., 2011). Posteriorly, there is a deeper and longer centrodiapophyseal fossa (cdf) framed by the acdl and pcdl, as in several neosauropods (Wilson et al., 2011). On the anterior surface of the neural spine, the medial spinoprezygapophyseal lamina (med. sprl) delimits a triangular, dorsoventrally high and proximally wide spinoprezygapophyseal fossa (sprf) (Supporting Information, Fig. S 3 B). The spinoprezygapophyseal lamina fossa (sprl-f) is reduced and triangular in outline (Supporting Information, Fig. S 3 A), placed between the medial and lateral spinoprezygapophyseal laminae (med. sprl and lat. sprl). The pcdl, podl and cpol frame a wide and deep postzygocentrodiapophyseal fossa (pocdf) on the posterior half of the vertebra (Supporting Information, Fig. S 3 A); a similar fossa, but not as wide as in Ligabuesaurus, is present in several neosauropods, such as Brachiosaurus, Brasilotitan, Erketu, Euhelopus, Huabeisaurus Pang & Cheng, 2000, Leinkupal Gallina et al., 2014, Overosaurus, Phuwiangosaurus, Qiaowanlong, Rapetosaurus and Yunmenglong (Wiman, 1929; Janensch, 1950; Martin et al., 1994; Pang & Cheng, 2000; Wedel et al., 2000; Curry Rogers & Forster, 2001; Ksepka & Norell, 2006; Rose, 2007; Curry Rogers, 2009; Suteethorn et al., 2009; Wilson & Upchurch, 2009; You & Li, 2009; Coria et al., 2013; D’Emic et al., 2013; Lü et al., 2013; Machado et al., 2013; Gallina et al., 2014). In MCF-PVPH- 233 / 02, the pocdf is internally divided into several small subfossae by a set of thin accessory laminae, as in Brachiosaurus and Sauroposeidon (Janensch, 1950; Wedel et al., 2000). Dorsal to the zygodiapophyseal table (zdt; sensu Wilson et al., 2011), there is a rectangular and anteroposteriorly extended postzygospinodiapophyseal fossa (posdf), which is delimited ventrally by the podl, dorsally by the lat. sprl and posteriorly by the spol (Supporting Information, Fig. S 3 A), as in several Titanosauriformes (e. g. Brachiosaurus, Euhelopus, Overosaurus, Phuwiangosaurus, Rapetosaurus and Sauroposeidon; Janensch, 1950; Martin et al., 1994; Curry Rogers & Forster, 2001; Rose, 2007; Curry Rogers, 2009; Suteethorn et al., 2009; Wilson & Upchurch, 2009). However, unlike those forms, in Ligabuesaurus the posdf is delimited dorsally by the lat. sprl and not by a single sprl. On the posterior surface of the neural spine, the spol marks the lateral margins of a triangular, ventrally deep and transversely wide spinopostzygapophyseal fossa (spof). Dorsal vertebrae (Figs 13 – 17): Originally, Bonaparte et al. (2006) included five dorsal vertebrae in the holotype specimen of Ligabuesaurus (Supporting Information, Table S 1): one anterior dorsal vertebra (MCF-PVPH- 233 / 03), which was extensively described and figured in anterior and lateral views, and four posterior dorsal vertebrae (MCF-PVPH- 233 / 04 – MCF-PVPH- 233 / 07), of which only the most posterior element (MCF-PVPH- 233 / 07) was briefly described and figured in anterior view. In the following subsections, we present the new anterior dorsal vertebra MCF-PVPH- 908 and the articulated middle-posterior vertebrae MCF-PVPH- 228 / 03 – MCF-PVPH- 233 / 04. We also redescribe the remaining dorsal elements from the Ligabuesaurus type quarry (MCF-PVPH- 233 / 04 – MCF-PVPH- 233 / 07). Anterior dorsal vertebrae Dv- 03? (Figs 13, 14; Supporting Information, Fig. S 4): The new anterior dorsal vertebra MCF-PVPH- 908 is almost complete and preserves the centrum and the major part of the neural arch, lacking only part of the left diapophysis and the right distal margin of the neural spine. Taking into account that MCF-PVPH- 908 overlaps the anterior dorsal vertebra MCF-PVPH- 233 / 03 (Fig. 13), which was described and figured, in part, by Bonaparte et al. (2006), only the most remarkable features of MCF-PVPH- 908 (Fig. 14) are described below. The general morphology and proportions of MCF-PVPH- 908 are similar to the holotypic anterior dorsal vertebra MCF-PVPH- 233 / 03, with which it shares the diagnostic conditions of the short, wide and rhomboidshaped neural spines and dorsoventrally low neural pedicels. Owing to the anterodorsal position of the parapophyses on the centrum and the orientation of the diapophyses and prezygapophyses on the neural arch, we tentatively consider both elements as third anterior dorsal vertebrae of Ligabuesaurus. In MCF-PVPH- 908, the centrum is dorsoventrally low, with oval and prominent parapophyses placed on the anterodorsal margin of the lateral surface. The neural arch is on the posterior half of the centrum, with a tall and anteriorly directed neural spine in lateral view. In anterior view, the neural spine is rhomboidal and wider than the centrum (Fig. 14), with robust lateral margins and divided by the sprl into medial and lateral branches. The centrum is opisthocoelous, wider than high in anterior view (Fig. 14) and square in lateral view. The ventral surface is concave in lateral view (Fig. 13 C) and slightly convex in anterior view, with the presence of a medial low crest. In ventral view, close to the anterior margin, the ventral surface is slightly concave, whereas posteriorly it is slightly convex. There is a small and oval pleurocoel on the anterodorsal margin of the lateral surface, which is anteriorly delimited by a prominent lateral rim of the articular surface and posteriorly enclosed by the parapophyses. The parapophyses are in the anterodorsal margin of the lateral surface of the centrum, close to neurocentral suture. They are represented by oval processes that are laterally prominent and directed slightly to the posterior. In MCF-PVPH- 908, the neural arch is long and wide, occupying almost the entire dorsal surface of the centrum, and slopes in a slightly anterior direction in lateral view. The anterior opening of the neural canal is oval and higher than wide in anterior view (Fig. 14), whereas it is rhomboidal in posterior view. The prezygapophyses are positioned anterodorsally with respect to the diapophyses, but they do not overlap the anterior articular surface in lateral view. The articular surfaces of the prezygapophyses are almost flat, oval (slightly wider than long) and inclined in an angle of 25 ° with respect to the horizontal plane. A thin and prominent intraprezygapophyseal lamina linksthe prezygapophyses medioventrally, forming a slightly concave laminar structure in front of the opening of the neural canal (Fig. 14). Two robust and slightly medially inclined centroprezygapophyseal laminae run ventrally from the prezygapophyses to the anterodorsal margins of the centrum (Figs 13 A, B, 14). In MCF-PVPH- 908, a bifid spinoprezygapophyseal lamina runs dorsally towards the neural spine, formed by the med. sprl and the lat. sprl. The med. sprl is mediodorsally directed towards the distal third of the neural spine and is prominent, proximally wide and distally reduced where it converges with the prespinal lamina. Conversely, the lat. sprl runs dorsally towards the anterolateral margin of the base of neural spine and is short and smooth distally. In lateral view, a robust and slightly dorsally inclined prezygodiapophyseal lamina connects the posterolateral portion of the prezygapophysis with the anterior margin of the diapophysis. The diapophyses are long, laterally directed and with a slightly anterior inclination. They are on the posterior half of the centrum and below the zygapophyses in lateral view (Fig. 13 C). The diapophyses are rectangular in cross-section, being compressed anteroposteriorly and extended dorsoventrally. The acdl is inclined anteroventrally and intercepts the cprl close to the neurocentral suture, whereas the pcdl is directed more ventrally and links the diapophyses with the posterior half of the centrum (Fig. 13 C). Both laminae delimit a wide and triangular centrodiapophyseal fossa, which is slightly deeper anterodorsally (Supporting Information, Fig. S 4 A, C), as in several titanosaurians (e. g. Argentinosaurus Bonaparte & Coria, 1993, Elaltitan Mannion & Otero, 2012, Neuquensaurus and Paludititan Bonaparte & Coria, 1993; Salgado et al., 2005; Csiki et al., 2010; Otero, 2010; Mannion & Otero, 2012). Dorsal to the diapophyses, thin and prominent spinodiapophyseal laminae (spdl) are directed towards the lateral margin of the base of the neural spine, where they run in parallel to the lat. sprl (Fig. 13 B, C). In lateral view, between the prezygapophyses and the diapophyses, there is a deep and triangular centroprezygapophyseal fossa (cprf), which is delimited dorsally by the prdl, ventrally by the acdl and medially by the cprl (Supporting Information, Fig. S 4 A). The postzygapophyses have slightly concave and poorly dorsally inclined articular surfaces, with an angle of 8 ° with respect to the horizontal plane. A wide and shallow spinopostzygapophyseal fossa is present (Supporting Information, Fig. S 4 B). Ventral to the postzygapophyses, a robust cpol runs vertically towards the posterodorsal margin of the centrum, whereas the spinopostzygapophyseal lamina (spol) is directed dorsally, forming a prominent process on the distal third of the spine (Fig. 13 B, C). The neural spine is dorsoventrally tall, more than two times the height of the centrum, anteroposteriorly compressed and with a slightly anterior inclination in lateral view (Fig. 13 C). In anterior view, the spine is rhomboidal, as in Eucamerotus Hulke, 1872, Yunmenglong and the titanosaurian from Bor-Guvé (Blows, 1995; Ksepka & Norell 2010; Lü et al., 2013), and transversely expanded (Figs 13 A, 14). The lateral margins are rounded, exceeding the lateral margins of the centrum, a condition considered an autapomorphic feature of Ligabuesaurus. In MCF-PVPH- 233 / 03 and MCF-PVPH- 908, part of the lateral expansion of the spine is enhanced by the prominence of the spdl, unlike the posterior cervical vertebra MCF-PVPH- 233 / 02, in which the lat. sprl runs dorsally through the lateral margins of the spine. The anterior surface of the spine is slightly concave in lateral view, with the lateral and dorsal margins of the apex particularly thick owing to the prominence of sprl and prsl, respectively (Fig. 13 C). Medially, a laminar complex is composed by the med. sprl, which merges with the prsl, at least close to the distal portion of the spine (Figs 13 A, 14). In MCF-PVPH- 908, the prsl runs from the base to the apex of the neural spine, being more prominent medially (Fig. 14), whereas in MCF-PVPH- 233 / 03 the prsl is short and reduced to the apex of the spine (Figs 5 M, N, 13 A). The spinoprezygapophyseal fossa is slightly deeper and wider in MCF-PVPH- 908 than in MCF-PVPH- 233 / 03 (Fig. 14), but the different extensions of the prsl between MCF-PVPH- 908 and MCF-PVPH- 233 / 02 would depend either on the poor preserved condition of the anterior dorsal vertebra of the holotype or on the different ontogenetic stages of the specimens (Wilson, 1999, 2012; Wedel & Taylor, 2013; Carballido & Sander, 2013), or a combination of both conditions. The posterior surface of the neural spine is transversely convex, with a medial laminar complex that consists of spol and posl. In both MCF-PVPH- 908 and MCF-PVPH- 233 / 02 anterior dorsal vertebrae, the posl is low and reduced to the distal third of the spine (Fig. 13 B). Middle dorsal vertebra Dv- 05? (Fig. 15; Supporting Information, Fig. S 5): This almost complete dorsal vertebra (MCF-PVPH- 233 / 04) is articulated with the next element and preserves the centrum and most of the neural arch. However, the vertebra is deformed transversely, and only the anterior and right lateral surfaces have been prepared. Considering the morphology of the ventral surface of the centrum, the relative position of the parapophysis on the neural arch and with respect to the diapophysis and the posterior inclination of the neural spine, MCF-PVPH- 233 / 04 is here reinterpreted as a middle dorsal vertebra and not as a posterior one (contra Bonaparte et al., 2006). Considering that the anterior articular surface of MCF-PVPH- 233 / 04 is convex and the posterior articular surface of MCF-PVPH- 233 / 05 is concave, both dorsal vertebrae are recorded as opisthocoelous. In anterior view, the centrum of MCF-PVPH- 233 / 04 is squared, wider than high and longer than tall in lateral view. The ventral surface is convex transversely and concave anteroposteriorly, with no ventrolateral crests, medial keel or longitudinal carinae. Laterally, most of the dorsal half of the centrum is occupied by a large and oval pleurocoel, which has an anterior rounded margin and tapers posteriorly (Fig. 15). A bone septum divides the pleurocoel into a wide and deeper anterior subfossa and a shallow and oval posterior subfossa. The neural arch occupies almost all of the dorsal surface of the centrum and is slightly anteriorly directed in lateral view, whereas the neural spine is strongly projected backward (Fig. 15), as in Andesaurus, Brachiosaurus, Daxiatitan You et al., 2008, Huabeisaurus, Opisthocoelicaudia, Ruyangosaurus Lü et al., 2009 and Saltasaurus (Janensch, 1950; Borsuk-Białynicka, 1977; Powell, 2003; You et al., 2008; Lü et al., 2009, 2014; Mannion & Calvo, 2011; D’Emic et al., 2013). The parapophysis is on the anterolateral portion of the neural arch and located dorsally to the anterior articular surface of the centrum and anteroventrally to the diapophysis. The articular surface of the parapophysis is subcircular in cross-section and with a slightly anterodorsal inclination. Ventrally, there is a short and robust anterior centroparapophyseal lamina (acpl) and a longer but thinner posterior centroparapophyseal lamina (pcpl). The acpl is bifid proximally, whereas it is robust distally and runs vertically towards the anterodorsal margin of the centrum. Conversely, the pcpl is inclined posteroventrally and intercepts the anterior centrodiapophyseal lamina around half of the centrum. The parapophysis and diapophysis are linked by a prominent and posterodorsally inclined paradiapophyseal lamina (ppdl). In MCF-PVPH- 233 / 04, the prezygapophysis is oval in cross-section and transversely extended. In lateral view, the prezygoparapophyseal lamina (prpl) is incomplete, whereas the prezygodiapophyseal lamina is robust and posteriorly projected (Fig. 15). Medial to the prezygapophysis, there is a long and prominent sprl. The centroprezygapophyseal lamina is fragmented and represented by a distal portion in the anterodorsal margin of the centrum. In anterior view, the ventral margin of the prezygapophysis is prominent and triangular, framing the laterodorsal edge of a diagenetically deformed hypantrum. The diapophysis is poorly preserved and located posterodorsally to the parapophysis, on the posterior third of the centrum. It is oval in cross-section, dorsoventrally compressed and dorsoposteriorly inclined. A prominent spinodiapophyseal lamina originates on the dorsal margin of the diapophysis, which runs dorsally towards the neural spine and limits posteriorly a wide prezygospinodiapophyseal fossa (prsdf) on the anterodorsal portion of the neural arch (Supporting Information, Fig. S 5 A). The diapophysis connects to the centrum via an anterior centrodiapophyseal lamina and a posterior centrodiapophyseal lamina. The acdl intercepts the pcpl distally, whereas the pcdl intercepts the cpol posteriorly, close to the dorsal surface of the centrum (Fig. 15). In lateral view, the parapophyseal centrodiapophyseal fossa (pacdf) is triangular and deep, whereas the centroparapophyseal fossa (cpaf) is shallow and rhomboidal (Supporting Information, Fig. S 5 A). In MCF-PVPH- 233 / 04, the postzygapophyses are hidden by the prezygapophyses of the following dorsal vertebra. However, part of a wide and triangular hyposphene and a robust cpol are evident. In lateral view, the cpol is short and robust, forming the posterior edge of a wide and deep postzygocentrodiapophyseal fossa, which is delimited anteroventrally by the pcdl (Fig. 15; Supporting Information, Fig. S 5 A). The neural spine is incomplete and represented by a wide and transversely convex basal portion, but the neural spine seems to have been taller than the height of the centrum and posteriorly inclined. Middle dorsal vertebra Dv- 06? (Fig. 15; Supporting Information, Fig. S 5): This vertebra (MCF-PVPH- 233 / 05) preserves most of the centrum and the neural arch, with the basal portion of the neural spine. Only the left lateral and posterior sides are visible because it is articulated with the preceding vertebra and there is still part of the field plaster jacket hiding part of the bone. The general morphology of this vertebra resembles the previous element. The centrum is slightly longer than tall in lateral view (Fig. 15) and bears a concave posterior articular surface that is oval and compressed dorsoventrally in posterior view. The ventral surface is transversely convex but more anteroposteriorly concave in lateral view than the previous vertebra, a condition that is enhanced by the prominent ventral margin of the posterior articular surface. In MCF-PVPH- 233 / 05, the parapophyses and diapophyses are slightly more dorsally positioned than in the previous vertebra, but connected in a similar manner with centrum through the acpl, pcpl, acdl and pcdl. The centroparapophyseal laminae are slightly longer but less posteriorly inclined than in MCF-PVPH- 233 / 04, whereas the pcdl is more anteriorly inclined in MCF-PVPH- 233 / 05 (Fig. 15). Ventrally, the cdf is triangular and anteroposteriorly extended, whereas the pocdf is oval (Supporting Information, Fig. S 5 A). Both fossae are slightly shorter than in the preceding dorsal vertebra. A posteroventrally directed pcpl divides an oval pacdf from a shorter and shallower triangular cpaf (Supporting Information, Fig. S 5 A). The postzygapophyses are oval, transversely wide and slightly reduced anteroposteriorly. They are linked with the neural spine by a long and prominent spinopostzygapophyseal lamina. In lateral view, the neural spine slopes posteriorly, slightly more than in MCF-PVPH- 233 / 04, exceeding the posterior articular surface of the centrum (Fig. 15). Posterior dorsal vertebra Dv- 07? (Fig. 16; Supporting Information, Fig. S 6): The specimen (MCF-PVPH- 228 / 03) is articulated with the next element and comprises the centrum and most of the neural arch. It lacks the neural spine and shows signs of diagenetic deformations caused by transversal plastic compressions on the right side. By comparing with most complete sauropod dorsal series (e. g. Brachiosaurus, Euhelopus, Haplocanthosaurus and Overosaurus; Hatcher, 1903; Janensch, 1950; Wilson & Upchurch, 2009; Coria et al., 2013), MCF-PVPH- 228 / 03 is here considered as a posterior dorsal vertebra, probably the seventh, to show a relative short centrum and a tall neural arch, with the parapophysis well above the anterior articular surface of the centum but anterodorsally displaced with respect to the diapophysis. In lateral view, the centrum is slightly longer than tall, with a convex anterior articular surface and an anteroposteriorly concave ventral surface (Fig. 16 A). On the anterodorsal margin of the lateral side there is a deep and oval pleurocoel, which is divided by a septum into a wide and deep anterior subfossa and a shorter and shallower posterior one. In turn, an accessory septum in the anterior subfossa of the right lateral side of the centrum delimits an oval and shorter ventral subfossa and a deep dorsal subfossa, which shows several accessory septa and internal chambers. An artefactual fracture on the left lateral side shows a somphospondylan internal structure of the centrum (Wedel et al., 2000), suggesting a high pneumatization in the presacral vertebrae of Ligabuesaurus, which is a synapomorphy shared with several derived Titanosauriformes (Upchurch et al., 2004). The neural arch occupies almost the entire dorsal surface of the centrum and exhibits a gentle anterior inclination (Fig. 16 A). The parapophyses are oval, anterolaterally directed and surpass the anterior articular surface of the centrum in lateral view. Ventrally, they link with the centum via a subvertical acpl (Fig. 16 A, B) and a longer and posteriorly inclined pcpl (Fig. 16 A, C). The pcpl delimits the pleurocoel dorsally. A poorly preserved lamina runs from the posterodorsal margin of the parapophysis towards the diapophysis, forming a short and thin ppdl (Fig. 16 A, B). The diapophysis is incomplete and represented by the oval basal portion, which is placed in a posterodorsal position with respect to the parapophysis in lateral view. The acdl is prominent and slopes in a gentle anteroventral direction (Fig. 16 A), whereas the pcdl is slightly longer and almost vertical, merging with the pcpl around half of the dorsal surface of the centrum (Fig. 16 A). In lateral view, the ppdl, acdl and pcpl enclose dorsally, posteriorly and ventrally a wide and deep pacdf in the anterolateral side of the neural arch (Supporting Information, Fig. S 6 A), whereas a smaller and triangular cdf opens between the acdl, pcdl and pcpl beyond the pleurocoel. In anterior view, the prezygapophyses are strongly deformed, and only the oval basal portion of the left prezygapophysis can be observed (Fig. 16 B). Posterior dorsal vertebra Dv- 08? (Fig. 16; Supporting Information, Fig. S 6): The specimen MCF-PVPH- 228 / 04 is represented by a well-preserved centrum and a deformed neural arch, which includes part of the basal portion of the neural spine. The general morphology of this posterior dorsal vertebra resembles the preceding element. The centrum is quadrangular in lateral view, slightly longer than tall, but strongly deformed transversely in posterior view (Fig. 16 C). The pleurocoel is wide and oval, with well-defined anterior and posterior margins (Fig. 16 A). The parapophysis and diapophysis are taller than in the previous vertebra, but they are poorly preserved in both lateral sides of the neural arch. The centroparapophyseal laminae and the pcdl are long and posteroventrally inclined, whereas the acdl is not preserved. In lateral view, the centroparapophyseal laminae delimit posteriorly a deep and dorsoventrally tall prcdf, whereas together with pcdl and pcpl they enclose a tall pacdf (Supporting Information, Fig. S 6 A). In posterior view, the postzygapophyses are incomplete and transversely deformed, although parts of robust cpol are preserved (Fig. 16 C). MCF-PVPH- 228 / 04 preserves the basal portion of the neural spine, which is dorsoposteriorly inclined (Fig. 16 A). Posterior dorsal vertebra Dv- 09? (Fig. 17): Bonaparte et al. (2006) briefly described two articulated posterior dorsal vertebrae from quarry no. 4, but figured only the most anterior element of the block in anterior view (MCF-PVPH- 233 / 06). Both elements exhibit strong diagenetic deformation and are partly overlapping, but we consider MCF-PVPH- 233 / 06 and MCF-PVPH- 233 / 07 as posterior dorsal vertebrae, probably ninth and tenth, to preserve tall and dorsally directed neural spines, in addition to high and jointed postzygapophyses. Thecentrumof MCF-PVPH- 233 / 06 isopisthocoelous, dorsoventrally compressed and wider than tall. There is an oval and deep pleurocoel on the anterodorsal margin of the lateral surface that slopes gently in an anteroventral direction. The anterior opening of the neural canal is wide and triangular, whereas the posterior one is shorter and rather oval. In anterior view, the prezygapophyses are almost flat and with a slight medial inclination (Fig. 17 A). A robust and rather vertical cprl runs distally from the ventral surface of the prezygapophyses, which form tall neural arch pedicels. The prezygapophyses are linked medially by a prominent and slightly concave tprl, which delimits dorsally the neural canal on the anterior surface of the vertebra. A short and thin sprl goes from the dorsal surface of the prezygapophyses towards the basal portion of the neural spine with a slight medial inclination, where it connects with a low and short prsl (Fig. 17 A). The diapophyses are incomplete, laterally directed and oval in cross-section, being tall and with strong anteroposterior compression in lateral view. Dorsally, the spdl is long and prominent, forming the lateral margin of the neural spine, whereas a posteroventrally directed pcdl links the diapophysis with the posterior half of the centrum (Fig. 17 B). Two robust and tall cpol are preserved on the posterior surface of the neural arch. In the specimen MCF-PVPH- 233 / 06, the hyposphene is wide, posteriorly prominent and ventrally bifid, with infrahyposphenial crests (Fig. 17 B), as in several Titanosauriformes (e. g. Giraffatitan, Brachiosaurus, Sonorasaurus Ratkevich, 1998 and Phuwiangosaurus; Riggs, 1903; Janensch, 1914, 1950; Martin et al., 1994; Ratkevich, 1998; Suteethorn et al., 2009; Taylor, 2009; D’Emic et al., 2016) and the basal titanosaurian Andesaurus (Calvo & Bonaparte, 1991). The neural spine is tall, more than two times the height of the centrum, and anteroposteriorly short, with a gentle anterior inclination in lateral view. In anterior view, the spine is almost rectangular, with the lateral margin being straight and slightly divergent distally (Fig. 17 A). On the distal third of the spine, two accessory spinodiapophyseal laminae (acc. spdl) run medially from the lateral margin of the spine to connect with the sprl, forming a ‘ cross-shape’ complex (Fig. 17 A), as in Barrosasaurus Salgado & Coria, 2009, Brachiosaurus and Sauroposeidon (Janensch, 1950; Rose, 2007; Salgado & Coria, 2009). The anterior surface of neural spine is transversely concave, although a prominent prsl is present medially through the preserved portion of the neural spine, especially where it connects with acc. spdl; these laminae, together with the spdl, delimit a short, crescent-shaped and ventrally deep fossa. Posterior dorsal vertebra Dv- 10? (Fig. 17): This vertebra preserves most of the neural arch; however, only the left prezygapophysis, the basal portions of diapophyses, the anteroventral half of the neural spine and the posterior side of the neural arch are exposed. In the specimen MCF-PVPH- 233 / 07, the diapophyses are tall and anteroposteriorly compressed in lateral view, whereas they are laterally directed and with a slight ventral inclination in anterior view (Fig. 17 A). A simple and long spdl runs upwards from the dorsal margin of the diapophysis, forming part of the lateral margin of the neural spine (Fig. 17 A, B). There is a vertical accessory spdl that runs parallel to a thin prsl (Fig. 17 A). The postzygapophyses bear wide and flat articular surfaces, with a slight lateroventral inclination in posterior view. A prominent cpol with a gentle lateroventral inclination goes towards the centrum, whereas there are robust and wide spol running towards the distal half of the neural spine (Fig. 17 B). Between the postzygapophyses, a prominent and wide process forms the accessory articular complex of the hyposphene, as in MCF-PVPH- 233 / 06. The hyposphene is ventrally bifid, bearing infrahyposphenal crests (Apesteguía, 2005), as in several Titanosauriformes (e. g. Andesaurus, Brachiosaurus, Giraffatitan, Phuwiangosaurus and Sonorasaurus; Riggs, 1903; Janensch, 1914; Martin et al., 1994; Suteethorn et al., 2009; Mannion & Calvo, 2011; D’Emic et al., 2016). In the specimen MCF-PVPH- 233 / 07, the neural spine is rectangular, with almost vertical lateral margins, which exhibit only gentle divergence distally in anterior and posterior views (Fig. 17 A, B). In lateral view, it is dorsally directed and exhibits strong anteroposterior compression. The posl is prominent in the basal portion of the neural spine, becoming thin longitudinally as short grooves more distally (Fig. 17 B). Anterior caudal vertebra Ca- 02? (Fig. 18 A – E): The new specimen MCF-PVPH- 261 / 15 preserves most of the centrum, lacking part of the lateral side of the anterior surface, the proximal portions of the transverse processes and part of the neural arch. MCF-PVPH- 261 / 15 was founded close to the sacrum of Ligabuesaurus in the type quarry no. 4 (Fig. 3) and is therefore considered to be an anterior caudal vertebra, probably the second, showing a short and tall centrum and well-developed transverse processes on the dorsolateral margin of the centrum, as in other anterior caudal elements of titanosauriformes (e. g. Andesaurus, Brachiosaurus, Chubutisaurus and Padillasaurus Carballido et al., 2015; Janensch, 1950; Mannion & Calvo, 2011; Carballido et al., 2011, 2015). In lateral view, the centrum is rectangular, anteroposteriorly short and dorsventrally tall (Fig. 18 C), as in Chubutisaurus, Huabeisaurus, Sauroposeidon and Tastavinsaurus Canudo et al., 2008 (Rose, 2007; Canudo et al., 2008; Carballido et al., 2011; D’Emic et al., 2013). The ventral border is flat in lateral view but transversely convex in anterior view (Fig. 18 A), lacking chevron articular surfaces, a medial keel or ventrolateral crests. In anterior view, the anterior articular surface is oval, slightly taller than wide and gently concave close to the lateral margins, being rather flat in the central area (Fig. 18 A). The posterior articular surface is almost rounded, with both dorsal and ventral surfaces almost flat (Fig. 18 B), whereas it is slightly convex in lateral view. MCF-PVPH- 261 / 15 is considered slightly procoelous, a condition that Ligabuesaurus shares with some derived Eusauropoda (e. g. Losillasaurus Casanovas et al., 2001 and Turiasaurus Royo Torres et al., 2006), several flagellicaudatans (Apatosaurus, Barosaurus, Dicraeosaurus Janensch, 1929, Diplodocus and Leinkupal; Marsh, 1877, 1890; Hatcher, 1901; Janensch, 1929; Gallina et al., 2014) and the basal titanosaurian Andesaurus (Mannion & Calvo, 2011). The lateral surfaces of the centrum are gently concave anteroposteriorly, but no pleurocoel or pneumatic fossa is observed. However, several short and oval vascular foramina open on the lateral surfaces of the centrum (Fig. 18 C), as in some diplodocoids (Apatosaurus and Suuwassea Harris & Dodson, 2004), Giraffatitan (Janensch, 1914), Yunmenglong (Lü et al., 2013) and several titanosaurians (Alamosaurus, Andesaurus, Epachthosaurus, Dreadnoughtus, Lusotitan Antunes & Mateus, 2003, Malawisaurus Jacobs et al., 1993 and Saltasaurus; Gilmore, 1922; Haughton, 1928; de Lapparent & Zbyszewski, 1957; Bonaparte & Powell, 1980; Powell, 2003; Martínez et al., 2004; Mannion & Calvo, 2011; Mannion et al., 2013; Lacovara et al., 2014). The transverse processes are located on the anterodorsal portion of the centrum and directed anterolaterally in dorsal view (Fig. 18 D). The neural arch occupies the anterior two-thirds of the dorsal surface of the centrum and gently slopes in an anterior direction in lateral view (Fig. 18 C), at least with its basal portion. In anterior view, the opening of the neural canal is oval, transversely wide and dorsoventrally compressed. However, it is partly filled by the matrix posteriorly and seems to have a quadrangular outline (Fig. 18 B). Dorsal ribs (Fig. 1 8 F, G): The axial skeleton of Ligabuesaurus includes the dorsal rib MCF-PVPH- 261 / 17 from the type quarry no. 4 and six almost complete dorsal ribs from quarry no. 3 (Supporting Information, Table S 1). The proximal portions of the ribs are oval in cross-section, without crests, fossae or foramina. In MCF-PVPH- 228 / 07, there is a depressed surface between the tuberculum and capitulum (Fig. 18 F) as in Tastavinsaurus (Canudo et al., 2008; RoyoTorres et al., 2012), Venenosaurus Tidwell et al., 2001 and other Titanosauriformes (Wilson & Sereno, 1998; Wilson, 2002). When preserved, the capitula and tubercula are long and oval, diverging in an angle> 90 ° in anterior view. The tuberculum is usually longer than the capitulum, but more robust in most of the ribs. In MCF-PVPH- 228 / 10, the external surface of the bone is weathered, showing the internal structure of the proximal portion of the rib, which is composed of small camellae of different shape and size divided by thin septa (Wedel et al., 2000; Wedel, 2003 a, b, 2005). This condition is widely distributed among Titanosauriformes (Wilson, 2002) and usually in the anterior dorsal ribs (Mannion & Calvo, 2011). The proximal portion of the shaft is wide anteroposteriorly and elliptical in cross-section, with a flat lateral side and a slightly convex medial surface. Distally, the preserved shafts are almost straight, with a gentle medial slope in anteroposterior view, and the general morphology being plank-like, as in several titanosauriforms (Upchurch et al., 2004). Appendicular skeleton Scapula (Fig. 19 A, B): In addition to the left and right scapulae (MCF-PVPH- 233 / 08 and MCF-PVPH- 233 / 09) extensively described by Bonaparte et al. (2006), we present a new right element (MCF-PVPH- 228 / 11) belonging to the individual from quarry no. 3, which we referred to Ligabuesaurus. This specimen is fragmented, lacking most of the acromial portion and the posterior half of the shaft, which were broadly restored artificially. Furthermore, considering that only the right scapula was drawn in lateral view by Bonaparte et al. (2006), we also figure the left scapula MCF-PVPH- 233 / 08. For descriptive means, the bone is oriented with the long axis of the scapular lamina held horizontally. The acromial region is dorsally extended. It is two times wider than the scapular shaft. A robust acromial crest divides the supracoracoidal fossa into two areas, with the anterior area being wider than the posterior one (Fig. 19 A). The posterior margin of the acromion is almost flat, with a gentle posterodorsal slope, and forms an angle of 120 ° with the dorsal margin, as in Euhelopus, Giraffatitan and Phuwiangosaurus (Janensch, 1914; Wiman, 1929; Martin et al., 1994, 1999). The dorsal margin is convex, anteroposteriorly extended and slightly broader in its posterior half. In anterior view, the coracoid articular surface is convex and posterodorsally inclined, forming an angle of 40 ° with respect to the long axis of the bone, as in Angolatitan Mateus et al., 2011, Huabeisaurus (D’Emic et al., 2013) and some titanosaurians (e. g. Antarctosaurus, Elaltitan, Neuquensaurus, Rapetosaurus and Saltasaurus; Lyddeker, 1893; von Huene, 1929; Bonaparte & Powell, 1980; Powell, 2003; Curry Rogers, 2009; Otero, 2010). The coracoid articular surface is rough, slightly more robust anteroventrally, and separated from the glenoid by a low step in lateral view (Fig. 19 A). The glenoid is oval and dorsoventrally expanded, with a convex medial surface. The articular surface is rough, slightly concave and medially directed in posterior view. In Ligabuesaurus, the ventral surface of the scapula and the glenoid form a pointed and anteroventrally directed process (Fig. 19 A, B), as in different sauropods (e. g. Camarasaurus, Giraffatitan, Mamenchisaurus, Phuwiangosaurus and Rapetosaurus; Janensch, 1914; Osborn & Mook, 1921; Young & Zhao, 1972; Curry Rogers, 2009; Martín et al., 1999). In lateral view, the ventral surface of the scapula is anteroposteriorly concave but bears a gently prominent medioventral process on the proximal third of the bone (Fig. 19 A, B). This process is triangular and laminar, as in Cetiosaurus Owen, 1841 (Upchurch & Martin, 2003), Mamenchisaurus (Young, 1954), Supersaurus Jensen, 1985 and several Titanosauriformes (e. g. Alamosaurus, Angolatitan, Chubutisaurus, Dreadnoughtus, Giraffatitan, Mendozasaurus, Patagotitan, Phuwiangosaurus, Ruyangosaurus and Wintonotitan; Janensch, 1914; Gilmore, 1922; Martin et al., 1994, 1999; González Riga, 2003; Taylor, 2009; Hocknull et al., 2009; Lü et al., 2009, 2014; Carballido et al., 2011; Mateus et al., 2011; Lacovara et al., 2014; Poropat et al., 2015 a; Ullmann & Lacovara, 2016; Carballido et al., 2017; González Riga et al., 2018). The scapular shaft is transversely compressed and with a slightly medial inclination in dorsal view, showing a convex lateral side and an almost concave medial surface. The scapular lamina is ‘ D-shaped’ in cross-section, wider ventrally than dorsally, as in Jobaria Sereno et al., 1999 (Sereno et al., 1999), most Neosauropoda and some derived titanosaurians (Carballido et al., 2011). Posteriorly, the dorsal margin of the shaft (Fig. 19 A, B) bears an elongated and rough surface for the insertion of the muscle levator scapulae (BorsukBiałynicka, 1977). The dorsal and ventral surfaces of the lamina are almost straight and gently diverge posteriorly, without forming the prominent processes seen in Rebbachisauridae (Mannion, 2009; Carballido et al., 2010), Camarasaurus, Cetiosaurus and Haplocanthosaurus (Hatcher, 1903; Osborn & Mook, 1921; Jensen, 1985; Upchurch & Martin, 2003). The posterior distal margin of the shaft is convex and rough, being transversely expanded in dorsal view. The shape of the scapular lamina of Ligabuesaurus resembles that of Apatosaurus, Rukwatitan, Euhelopus and Huabeisaurus (Wiman, 1929; Jensen, 1985; D’Emic et al., 2013; Gorscak et al., 2014) and is unlike the more distally expanded laminae seen in some basal camarasauromorphs and Rebbachisauridae (Mannion, 2009; Carballido et al., 2010). Coracoids (Fig. 19 C – H): New left and right almost complete coracoids (MCF-PVPH- 261 / 05 and MCF-PVPH- 261 / 06) from the type quarry no. 4 are described below. In lateral view, the bone is crescentic, slightly more extended dorsoventrally than anteroposteriorly, and with the dorsal half sloping posteriorly (Fig. 19 C), as in Cedarosaurus Tidwell et al., 1999, Euhelopus, Giraffatitan and Uberabatitan (Janensch, 1914; Wiman, 1929; Tidwell et al., 1999; Salgado & Carvalho, 2008; Taylor, 2009; Silva Junior et al., 2021). This condition differs from the rounded or oval-shaped coracoids seen in several basal sauropods (Upchurch & Martin, 2003) and from the subrectangular coracoids of most of the derived titanosaurians (e. g. Opisthocoelicaudia and Saltasaurus; Borsuk-Białynicka, 1977; Bonaparte & Powell, 1980; Powell, 2003) (Fig. 5 B – K). In Ligabuesaurus, the coracoid is dorsoventrally shorter than the proximal surface of the scapula. Thus, when articulated, a concave and V-shaped surface divides the dorsal surfaces of both the scapula and coracoid in lateral view, as in several Sauropoda (Upchurch et al., 2004). In contrast, most Titanosauria (e. g. Neuquensaurus, Opisthocoelicaudia, Alamosaurus and Patagotitan; Borsuk-Białynicka, 1977; Tang et al., 2001; Lehman & Coulson, 2002; Powell, 2003; Otero, 2010; Carballido et al., 2017) share the plesiomorphic condition of a coracoid transversely wide, such that its dorsal surface is at the same level or beyond the dorsal surface of the scapula. In MCF-PVPH- 261 / 05 and MCF-PVPH- 261 / 06, the anterior surface is convex and posterodorsally inclined, whereas the posterior surface is sinusoidal, being dorsally concave and ventrally prominent (Fig. 19 C, H), as in several somphospondylans (Wilson, 2002). The ventral half of the bone is quadrangular in lateral view, because the anterior and posterior margins of the coracoid are aligned roughly at right angles to the ventral surface, as in Tapuiasaurus Zaher et al., 2011. However, in the latter taxon only the anterior surface of the coracoid forms an angle of 90 ° with the ventral surface. The anteroventral surface of the coracoid is rough and medially prominent, representing the articular surface with the sternal plate (Wilhite, 2003, 2005); in contrast, there is a gentle and short ridge for the attachment of the muscle biceps brachii on the laterodorsal margin (br; Fig. 19 C, H), as in several sauropods (Otero, 2018). The lateral surface of the coracoid shows, in turn, several subtle ventral rugosities that would represent the insertion of the muscle coracobrachialis brevis (cbb; Fig. 19 C, H), as seen in Opisthocoelicaudia (Borsuk-Białynicka, 1977). Throughout the posterior surface, there are two wide, rough and medially bevelled articular surfaces of the glenoid and the scapulocoracoid. The glenoid region is quadrangular in posteroventral view (Fig. 19 D, G) and slightly concave transversely, being laterally delimited by a prominent and bevelled edge (Fig. 19 C, H). The articular surface of the glenoid is rough and slightly longer than wide in posterior view, with the lateral margin dorsolaterally prominent and rather steeper than the medial one. Thus, part of the glenoid articular surface can be seen in lateral view, a derived condition that Ligabuesaurus shares with most of neosauropods (Poropat et al., 2016). Posteriorly, a prominent and wide process divides the glenoid from the scapulocoracoid articular surface, whereas a well-marked infraglenoid groove opens between the anteroventral margin of the coracoid and the glenoid. The infraglenoid groove is shallow, anteroposteriorly concave, and delimited posteriorly by the prominent, lateroventrally directed and rounded margin of the glenoid, as in Cetiosaurus, Haplocanthosaurus and Huanghetitan You et al., 2006 (Hatcher, 1903; Upchurch & Martin, 2003; D’Emic et al., 2013). Anteriorly, the ventral margin is rectangular, without an infraglenoid lip. Conversely, the scapulocoracoid articular surface is straight in posterior view, being dorsally thin and transversely wide and robust in its ventral margin, where the surface is slightly concave. On the posterior half of both coracoids there is an oval coracoid foramen, which is slightly dorsoventrally directed in lateral view (Fig. 19 C, H) and completely enclosed by the anterior margin of the bone. In this sense, the degree of ossification of the anterior margin of coracoid foramen suggests a postjuvenile ontogenetic stage for the specimens MCF-PVPH- 261 / 05 and MCF-PVPH- 261 / 06 (sensu Upchurch et al., 2004). Humerus (Fig. 20 A – F): Although Bonaparte et al. (2006) mentioned a complete left humerus (MCF-PVPH- 233 / 10) and the proximal (MCF-PVPH- 233 / 11) and distal portions (MCF-PVPH- 233 / 11) of the right one, they briefly described and drew in anterior view only the complete specimen. Therefore, we only remark the general morphology of Ligabuesaurus humeri, paying particular attention to some morphological features of the distal half of the right humerus (MCF-PVPH- 233 / 12), which is preserved in better condition than the left one. In Ligabuesaurus, the humerus is an almost straight bone, with both epiphyses transversely more expanded with respect to the diaphysis in anterior view (Fig. 20 A). The robustness index (RI; sensu Wilson & Upchurch, 2003) of MCF-PVPH- 233 / 10 (RI = 0.24) suggests that the humerus is a slender bone, as in several nontitanosaurian Titanosauriformes (e. g. Cedarosaurus, RI = 0.21; Chubutisaurus, RI = 0.25; Giraffatitan, RI = 0.22; Phuwiangosaurus, RI = 0.25; Sauroposeidon, RI = 0.23; Carballido et al., 2019). Unlike Bonaparte et al. (2006), who consider the incomplete and strongly deformed right femur (MCF-PVPH- 233 / 17), the ratio of the length of the humerus to the length of the femur is here calculated on the basis of the new left complete femur MCF-PVPH- 261 / 12, resulting in a value of 0.79, as in most non-brachiosaurid sauropods (Upchurch et al., 2004). The proximal epiphysis is medially projected in anterior view (Fig. 20 A), as in Chubutisaurus, Diamantinasaurus, Lusotitan, Rapetosaurus and Sauroposeidon (Rose, 2007; Curry Rogers, 2009; Hocknull et al., 2009; Carballido et al., 2011; Mannion et al., 2013; Poropat et al., 2015 b). The proximolateral margin is straight, forming an angle of 95 ° with the proximal articular surface, as in some Titanosauriformes (Upchurch et al., 2004). In MCF-PVPH- 233 / 11, both dorsomedial and dorsolateral margins are rough, representing the attachment surfaces for the muscles supracoracoideus and pectoralis, respectively (Borsuk-Białynicka, 1977; Giménez, 1992; Upchurch, 1998). In dorsal view, the proximal end is triangular, with concave anterior and posterolateral margins (Fig. 20 B). The articular head is rounded, posteromedially directed and highly prominent, to a greater extent than in Angolatitan, Bellusaurus Dong, 1990, Bonatitan Martinelli & Forasiepi, 2004, Giraffatitan, Qingxiusaurus Mo et al., 2008, Rapetosaurus and Rukwatitan (Janensch, 1914; Dong, 1990; Mo et al., 2008; Curry Rogers, 2009; Taylor, 2009; Mateus et al., 2011; Mo, 2013; Gorscak et al., 2014; Salgado et al., 2015), in which the articular heads are slightly more prominent with respect to the rest of sauropods. The condition of a prominent humeral head is considered as an autapomorphic feature of Ligabuesaurus. On the posterior side of the humerus, the articular head is rough and oval, extending distally to form a ventrolaterally inclined and short neck (Fig. 20 D). At the sides of this neck, the bone surfaces are transversely concave and slightly rough (i. e. medial and lateral triceps fossae, sensu Upchurch et al., 2015), representing the attachment surfaces for the muscle triceps of the humeral articular head (BorsukBiałynicka, 1977). In anterior view, the proximal articular surface is gently convex medially owing to the presence of the articular head. In Ligabuesaurus, the transverse width of proximal epiphysis is convergent with Brachiosauridae, representing ~ 30 % of the total length of the humerus (Wilson & Sereno, 1998; Upchurch et al., 2004). Anteriorly, a wide and deep deltopectoral fossa occupies most of the proximal half of the humerus (Fig. 20 A). The fossa is triangular, proximally wider and distally extended, being delimited laterally by a prominent and longitudinal deltopectoral crest. Proximally, this crest is straight and anteriorly prominent, whereas it is wider and medially inclined close to the mid-shaft, as in titanosauriforms more derived than Brachiosaurus (Wilson & Sereno, 1998). In MCF-PVPH- 233 / 12, the distal epiphysis is transversely expanded with respect to the diaphysis in anterior view (Fig. 20 E), with an almost flat ventral articular surface. In distal view, the distal articular surface is rectangular, wider than long, with both ulnar and radial condyles slightly prominent anteriorly (Fig. 20 F). In MCF-PVPH- 233 / 10, the distal surface is poorly preserved, showing a pointed ulnar condyle and a rounded radial condyle, both of which are equally prominent (Fig. 20 C), as in Bonatitan, Camarasaurus and Giraffatitan (Cope, 1877; Janensch, 1914; Taylor, 2009; Salgado et al., 2015). In MCF-PVPH- 233 / 12, the ulnar condyle is rounded and with a slight anteromedial inclination in distal view, whereas the radial condyle is shorter and shallower. Anteriorly, the radial condyle is divided into two robust, medially convergent and anteriorly prominent processes (Fig. 20 C, F), as in several sauropods (D’Emic, 2012; D’Emic et al., 2016; Ren et al., 2020), excluding titanosaurians and some somphospondylans (e. g. Chubutisaurus and Sauroposeidon; Rose, 2007; Carballido et al., 2011), in which the radial condyle is undivided. On the posterior surface of distal epiphysis there are two dorsally convergent crests that delimit a wide and deep anconeal fossa (Fig. 20 C, D, F), a synapomorphic condition of Somphospondyli (Upchurch et al., 2004). Radius (Fig. 20 G – I): This new element (MCF-PVPH- 261 / 07) comes from the same quarry as the holotype specimen and is composed of the distal extremity of a left radius. The diaphysis is triangular in crosssection, with a slightly convex anterior surface and an almost flat posterior surface (Fig. 20 I), which represents the articular surface with the ulna. In lateral view, the distal end is expanded with respect to the diaphysis, especially through the prominent posterodistal edge (Fig. 20 G). The distal articular surface is convex in anterior view, with most of the lateral portion being slightly bevelled, whereas it is trapezoidal in ventral view, with a straight lateral margin that forms a right angle with the posterior side (Fig. 20 H). Metacarpals (Fig. 21): The four metacarpal specimens known for Ligabuesaurus were briefly described but not figured by Bonaparte et al. (2006). The holotype of Ligabuesaurus includes two metacarpals II (Fig. 21 A – E): an almost complete right metacarpal (MCF-PVPH- 233 / 13) and the distal end of a left metacarpal (MCF-PVPH- 233 / 15). MCF-PVPH- 233 / 13 is a long and slender bone (RI = 0.43), as in some titanosauriforms (e. g. Angolatitan, Giraffatitan and Venenosaurus; Janensch, 1914; Tidwell et al., 2001; Taylor, 2009; Mateus et al., 2011; Poropat et al., 2015 a) and titanosaurians (Laplatasaurus von Huene, 1929; Gallina & Otero, 2015). The ratio of the total length to proximal width of MCF-PVPH- 233 / 13 (4.4) is comparable to that of several brachiosaurids, such as Brachiosaurus, Sonorasaurus, Venenosaurus and OMNH- 01138 (Riggs, 1903; Ratkevich, 1998; Tidwell et al., 2001; Bonnan & Wedel, 2004), but higher with respect to most neosauropods (Bonnan & Wedel, 2004). The proximal articular surface is triangular in proximal view (Fig. 21 B), as in several Neosauropoda (Apesteguía, 2005), with a convex medial margin and a straight lateral margin. The articular surface is rough, laterally convex, and with a slight anteroventral inclination in lateral view (Fig. 21 A). The diaphysis is bowed in lateral and medial views, proximally straight and anteromedially inclined (Fig. 21 A, D), as in Antarctosaurus (von Huene, 1929) but unlike most neosauropods. Following Apesteguía (2005), the bowed condition of the first metacarpals would be associated with the presence of a well-developed ungual phalanx, suggesting that, at least in some derived titanosauriforms (e. g. Antarctosaurus and Ligabuesaurus), such a phalanx would be present on the first two fingers of the hand, as in several diplodocoids. Two longitudinal crests run ventrally from the posterolateral margin of the proximal end to the posterolateral margin of the distal end (vlr; Fig. 21 D). Thus, the diaphysis is triangular proximally and almost square in crosssection distally. The distal surface is quadrangular in distal view and longer than wide (Fig. 21 C, E). The anterior and medial margins are convex, whereas the posterior and lateral ones are slightly concave. The articular surface is rough and medially concave in anterior view, for a shallow intercondylar groove, as in most Titanosauriformes (Bonnan & Wedel, 2004; Apesteguía, 2005). The right metacarpal III of Ligabuesaurus (MCF-PVPH- 233 / 14; Fig. 21 F – I) is straight and slender (RI = 0.43), as in Laplatasaurus (RI = 0.4), Sauroposeidon (RI = 0.42) and Venenosaurus (RI = 0.4) (von Huene, 1929; Tidwell et al., 2001; Rose, 2007; Gallina & Otero, 2015). In dorsal view (Fig. 20 G), the proximal surface is rough and triangular, with almost straight margins, whereas it is slightly convex in lateral view (Fig. 21 F). The diaphysis is elliptical in cross-section, and slightly longer than wide. On the posterior surface there is a robust and longitudinal crest, slightly medioventrally directed, but well preserved only on the proximal third of the diaphysis. The distal surface is rough and rectangular in ventral view (Fig. 21 H), being wider than long. The anterior surface is convex, whereas the posterior surface is slightly concave, resulting in a shallower intercondylar groove than in metacarpal II. The metacarpal IV of Ligabuesaurus (Fig. 21 J) is represented by a left distal end (MCF-PVPH- 233 / 16), with a rough and rectangular articular surface in ventral view. The medial margin is convex, whereas the lateral margin is straight and dorsally rough for the articulation with the metacarpal V. In posterior view, a low intercondylar groove divides the rounded medial half of the distal surface from the more prominent lateral half, as in Brachiosaurus (Riggs, 1903; Janensch, 1950), Venenosaurus (Tidwell et al., 2001) and the previous metacarpals of Ligabuesaurus. However, in MCF-PVPH- 233 / 16 the intercondylar groove does not extend dorsally throughout the posterodistal margin of the epiphysis. Ilium (Fig. 22 A): An incomplete left ilium (MCF-PVPH- 261 / 08) that was found articulated with the sacrum and left femur in the same quarry as the holotype specimen is described below. The bone preserves both pubic and ischiatic peduncles, in addition to part of the preacetabular and postacetabular processes. However, most of the anterodorsal portion of iliac expansion is lost. In lateral view, the ilium is dorsoventrally low and anteroposteriorly expanded, with a long and anteroventrally directed pubic peduncle on the ventral half and a rounded and low ischiatic peduncle on the distal third (Fig. 22 A). The preacetabular process is concave laterally and gently slopes anterolaterally in anterior view, being slightly longer than the postacetabular process in lateral view, as in most Neosauropoda (Wilson & Sereno, 1998; Wilson, 2011; Iijima & Kobayashi, 2014). In lateral view, the anterior margin of the preacetabular process is convex, bearing robust and prominent lateral margins (Fig. 22 A), as in several Titanosauriformes (e. g. Astrophocaudia D’Emic, 2012, Epachthosaurus, Giraffatitan, Phuwiangosaurus, Qiaowanlong and Sauroposeidon; Janensch, 1914, 1961; Martin et al., 1994, 1999; Martínez et al., 2004; Rose, 2007; Taylor, 2009; You & Li, 2009; D’Emic, 2013). Although it is poorly preserved, the iliac blade is transversely compressed and laterally inclined, as in most neosauropods (Wilson & Sereno, 1998). The pubic peduncle is crescent shaped and with a slight medial inclination in anterior view, as in Brachiosaurus, Giraffatitan, Camarasaurus, Phuwiangosaurus and Tastavinsaurus (Hatcher, 1903; Janensch, 1914, 1961; Osborn & Mook, 1921; Martin et al., 1994, 1999; Canudo et al., 2008; Taylor, 2009). The lateral margin is more robust and ventrally prominent than the medial one. Proximally, the pubic peduncle is oval in cross-section, being wider than long, whereas the distal half is more robust and posterolaterally expanded. The anterior surface of the pubic peduncle is straight in lateral view and transversely convex, whereas the posterior one is concave both dorsoventrally and transversely. The acetabulum is wide, with the anterodorsal apex closer to the pubic peduncle, as in Camarasaurus (Osborn & Mook, 1921), Cetiosaurus (Upchurch & Martin, 2003) and several Brachiosauridae (Salgado et al., 1997). Posteriorly, the ischiatic peduncle is oval, wider than long and posteroventrally directed in lateral view. Posteriorly, the postacetabular process is almost complete and lobe shaped in lateral view, with convex dorsal and posterior surfaces (Fig. 22 A) as in Brachiosaurus, Giraffatitan and Qiaowanlong (Janensch, 1914, 1950, 1961; Taylor, 2009; You & Li, 2009). The lateral surface is dorsoventrally concave and dorsolaterally inclined in posterior view. The posteroventral margin of the ilium is separated from the ischiatic peduncle by a low and anteriorly directed narrowconcavity, asseenin Giraffatitan, Huabeisaurus, Qiaowanlong and Tastavinsaurus (Janensch, 1914, 1961; Canudo et al., 2008; You & Li, 2009; D’Emic et al., 2013). Analysing its several fractures, the internal structure of MCF-PVPH- 261 / 08 seems to be compact, or at least without evident pneumatic chambers. This condition is considered to be a plesiomorphic feature within Sauropoda, with highly pneumatized ilia only found in Euhelopus and several Titanosauria (Mannion et al., 2013; Poropat et al., 2015 b). Pubes (Fig. 22 B – J): We describe three new specimens, represented by an incomplete left pubis (MCF-PVPH- 261 / 09) and the proximal (MCF-PVPH- 261 / 10) and distal (MCF-PVPH- 261 / 09 – MCF-PVPH- 261 / 11) halves of the right one. These specimens came from the same quarry as the holotype specimen. The left pubis preserves the proximal half and part of the pubic expansion, but is partly included in the field jacket on the lateral surface, whereas the right elements are well preserved, lacking only the mid-shaft of the bone. In Ligabuesaurus, the pubis is transversely compressed and proximodistally long, which gently slopes medially on its distal half (Fig. 22 G, H). In dorsal view, the proximal surface is crescent, longer than wide, and with a convex medial surface and a slightly concave lateral one (Fig. 22 C, F). The iliac peduncle is long and transversely compressed, but medially wider, as in Tastavinsaurus (Canudo et al., 2008), and not transversely compressed as in some titanosaurians (Andesaurus, Huabeisaurus and Sonidosaurus Xu et al., 2006; Calvo & Bonaparte, 1991; Pang & Cheng, 2000; Xu et al., 2006). The articular surface of the iliac peduncle is rough and convex in lateral view (Fig. 22 D, E), especially anteriorly, as in Phuwiangosaurus, Sauroposeidon and Tangvayosaurus Allain et al., 1999 (Martin et al., 1994, 1999; Allain et al., 1999; Rose, 2007). The anterodorsal surface of the pubis is rough and anteriorly extended in lateral view and bears the insertions for the musce ambiens. In Ligabuesaurus, the anterior margin does not form a prominent ambiens process, as seen in Janenschia Wild, 1991 (Bonaparte et al., 2000), some brachiosaurids (Giraffatitan and Vouivria Mannion, Allain & Moine, 2017; Janensch, 1961; Mannion et al., 2017) and several flagellicaudantans (Apatosaurus, Dicraeosaurus and Diplodocus; Marsh, 1877; Hatcher, 1901; Janensch, 1929). Posteriorly, a low step divides the iliac peduncle from the acetabular region, which is posteromedially inclined and slightly narrower than the anterior half of the proximal pubis (Fig. 22 C), as in Camarasaurus, Tangvayosaurus and Tastavinsaurus (McIntosh et al., 1996; Allain et al., 1999; Canudo et al., 2008). In the posterodorsal margin of the pubis there is an oval, dorsoventrally higher and posteroventrally oriented obturator foramen (Fig. 22 B, D, E). The shape of the obturator foramen of Ligabuesaurus resembles that of Cetiosaurus (Upchurch & Martin, 2003), several Titanosauriformes (e. g. Huabeisaurus, Tangvayosaurus and Tastavinsaurus; Allain et al., 1999; Canudo et al., 2008; Royo-Torres et al., 2012; D’Emic et al., 2013) and some basal titanosaurians (Andesaurus and Epachthosaurus; Martínez et al., 2004; Mannion & Calvo, 2011). The obturator foramen is completely enclosed in both specimens of Ligabuesaurus (MCF-PVPH- 261 / 09 and MCF-PVPH- 261 / 10), but the bone posterior to the foramen is thin and concave with respect to the rest of the bone, as in Huabeisaurus and Tangvayosaurus (Allain et al., 1999; D’Emic et al., 2013). Considering that posterodorsally open obturator foramina are recorded in juvenile sauropod specimens (Upchurch et al., 2004; Wilhite, 2005), the condition of Ligabuesaurus pubes would suggest an incomplete ossification of foramina, hence an intermediate ontogenetic stage between the juvenile and the adult, for them. In posterior view, the ischiatic peduncle is represented by a sigmoidal and transversely compressed surface that is medially inclined proximally and more robust distally, as in most Macronaria (Wilson & Sereno, 1998). Proximally, the pubic blade is teardrop shaped in cross-section. The distal surface is posteriorly convex in lateral view (Fig. 22 H) and elliptical ventrally (Fig. 22 J), being longer than wide, with an almost straight medial surface and a convex lateral side, as in Futalognkosaurus, Haplocanthosaurus and Tastavinsaurus (Hatcher, 1903; Calvo et al., 2007; Canudo et al., 2008). The distal surface is rough and extends, in part, throughout the distal margin of the medial, anterior and posterior surfaces. In anterior view, the pubic blade is triangular (Fig. 22), with the distal end medially expanded, as in Andesaurus and Dongbeititan Wang et al., 2007 (Mannion & Calvo, 2011). In Ligabuesaurus, the lateral surface of the pubic shaft is shallow, lacking any evidence of the lateral ridge present in different titanosaurians, such as Aeolosaurus Powell, 1987, Isisaurus Wilson & Upchurch, 2003, Neuquensaurus, Opisthocoelicaudia, Saltasaurus, Savannasaurus Poropat et al., 2016 and Uberabatitan (Borsuk-Białynicka, 1977; Salgado & Coria, 1993; Jain & Bandyopadhyay, 1997; Powell, 2003; Salgado & Carvalho, 2008; Otero, 2010; Poropat et al., 2016, 2020). In lateral view, the anterior margin of distal surface is pointed and more anterodorsally prominent than the posterior one, a condition that Ligabuesaurus shares with several neosauropods, such as Apatosaurus, Camarasaurus, Dongbeititan, Epachthosaurus, Fusuisaurus Mo et al., 2006, Rapetosaurus and Tastavinsaurus (Gilmore, 1936; McIntosh et al., 1996; Martínez et al., 2004; Mo et al., 2006; Wang et al., 2007; Canudo et al., 2008; Curry Rogers, 2009; Royo-Torres et al., 2012). Femur (Fig. 23): A new, almost complete and wellpreserved left femur (MCF-PVPH- 261 / 12) is presented here. The specimen was found in articulation with the left ilium (MCF-PVPH- 261 / 08) and associated with the proximal ends of the left tibia and fibula (MCF-PVPH- 261 / 13 and MCF-PVPH- 261 / 14) in the type quarry no. 4. Considering that the incomplete right femur (MCF-PVPH- 233 / 17) was extensively described by Bonaparte et al. (2006), only the general morphology and most remarkable features of MCF-PVPH- 261 / 12, especially about the proximal epiphysis, are described below. The femur of Ligabuesaurus is almost straight and slender (RI = 7.3), with the proximal third medially inclined, as in most Titanosauriformes (e. g. Wilson & Carrano, 1999; Carrano, 2005), and the distal end slightly expanded transversely in anterior view (Fig. 23 A, D). The proximolateral margin of the femur is convex, forming a prominent lateral bulge, as in other titanosauriforms (Salgado et al., 1997; Wilson & Sereno, 1998). The width of the femoral shaft at the level of the lateral bulge is 50 % greater than the minimum width at mid-shaft, as in several Titanosauriformes (e. g. Bonatitan, Chubutisaurus, Giraffatitan, Ruyangosaurus, Sauroposeidon, Tangvayosaurus and Yunmenglong; Janensch, 1914; Allain et al., 1999; Rose, 2007; Lü et al., 2009, 2013, 2014; Taylor, 2009; Carballido et al., 2011; Salgado et al., 2015). Dorsal to the lateral bulge, a rough and wide surface represents the greater trochanter, which in MCF-PVPH- 261 / 12 is particularly extended posterodorsally (Fig. 23 D). The greater trochanter is not divided distally for the lateral bulge by a trochanteric crest, unlike most titanosaurians (Mannion et al., 2013). In anterior view, the femoral head is rounded and dorsomedially directed, rising well above the level of the greater trochanter, as in most Somphospondyli (Curry Rogers, 2009; Poropat et al., 2016; Carballido et al., 2017). Posteriorly, a wide and concave surface separates the femoral head from the greater trochanter, forming an angle of ~ 120 ° with the lateral margin of the femur (Fig. 23 F), as in Bonatitan, Daxiatitan, Dongbeititan, Huabeisaurus, Paralititan Smith et al., 2001 and Yunmenglong (Pang & Cheng, 2000; Smith et al., 2001; Martinelli & Forasiepi, 2004; Wang et al., 2007; You et al., 2008; Lü et al., 2013). The femoral shaft is elliptical in cross-section, being strongly compressed anteroposteriorly and extended transversely. The minimum width is at the distal third of the bone, as in most sauropods. On the anterior surface of the shaft, a longitudinal and low crest runs ventrally from the greater trochanter to the distal third throughout the medial margin of the bone (lic; Fig. 23 D), identified as the linea intermuscularis cranialis (Otero & Vizcaino, 2008), as as in Bellusaurus (Dong, 1990) and several titanosaurians (e. g. Saltasaurus, Bonatitan, Neuquensaurus and Rocasaurus Salgado & Azpilicueta, 2000; Lyddeker, 1893; Bonaparte & Powell, 1980; Martinelli & Forasiepi, 2004). The fourth trochanter is on the posteromedial margin of the bone, slightly above the mid-shaft (Fig. 23 C, F, G), and is represented by a low and proximodistally extended surface, which is delimited posteriorly by prominent and short crests. The distal end slightly exceeds the width of the shaft in anterior view, with the lateral surface being more prominent than the medial one, whereas the ventral rim is rather sinusoidal (Fig. 23 A, D). The lateral bevelling condition of the distal femur of Ligabuesaurus is shared by several sauropods and differs from the medial bevelling seen in Dongbeititan (Wang et al., 2007), Yunmenglong (Lü et al., 2013) and different derived titanosaurians (Mannion et al., 2013; Poropat et al., 2015 b). The condyles are rounded and distally divergent in anterior view, with the tibial condyle more distally prominent than the fibular one. Anteriorly, a wide and concave anterior intercondylar groove (femoral trochlea) separates the tibial and fibular condyles (Fig. 23 A, B, D, E), whereas a narrower but deeper posterior intercondylar fossa opens between the condyles on the posterior surface (Fig. 23 B, C, E, F). In posterior view, the tibial condyle is rectangular, proximodistally longer than wide and with a slight lateral inclination (Fig. 23 C, E), as in Daxiatitan, Ferganasaurus Alifanov & Averianov, 2003, Sauroposeidon and Tastavinsaurus (Alifanov & Averianov, 2003; Rose, 2007; Canudo et al., 2008; You et al., 2008). In turn, the fibular condyle is rounded and transversely wider than long, with a narrow intracondylar groove dividing a short lateral subcondyle (epicondyle) from a triangular and wider posterior subcondyle (Fig. 23 B, C, E, F). In distal view, both condyles are oval, but the fibular condyle is slightly wider and more posteromedially inclined than tibial condyle (Fig. 23 B, E). The distal articular surface is rough, excluding the femoral trochlea and the intercondylar fossa, which is rather smooth and slightly extends dorsally, especially on the posterodistal margin of the bone. Tibia (Fig. 24 A – I): We describe a new proximal end of a left tibia (MCF-PVPH- 261 / 13) that was found in articulation with the left fibula in type quarry no. 4. Considering that the almost complete right tibia MCF-PVPH- 233 / 18 was briefly mentioned and figured in posterior view by Bonaparte et al. (2006), only the most remarkable features of the tibia of Ligabuesaurus are described below. The proximal end of the tibia is subcircular and exhibits slight transverse compression in proximal view (Fig. 24 D, F), as in most non-rebbachisaurid neosauropods, with convex anterior and medial rims and almost flat posterior and lateral rims. The articular surface is flat in lateral view (Fig. 24 B, H) and is slightly concave on its posterodorsal margin where it articulates with the tibial condyle of femur. On the anterodorsal edge, there is a robust and laterally prominent cnemial crest that delimits anteriorly a wide and deep cnemial fossa (Fig. 24 A, B, D, F, H), as in most eusauropods (Wilson & Sereno, 1998), but not as wide as in several Titanosauria (e. g. Atsinganosaurus Garcia et al., 2010, Laplatasaurus, Lirainosaurus, Neuquensaurus and Rapetosaurus; Curry Rogers, 2009; Otero, 2010; Díez Díaz et al., 2013 a, 2018; Gallina & Otero, 2015). The cnemial crest runs vertically throughout the lateral surface of the proximal end and is convex and rounded in anterior view (Fig. 24 A, H), as in Bonatitan, Chubutisaurus, Giraffatitan and Huabeisaurus (Janensch, 1914, 1961; Carballido et al., 2011; D’Emic et al., 2013; Salgado et al., 2015). On the inner surface of the cnemial crest opens a proximodistally elongated cnemial fossa where the anterior crest of the fibula articulates, whereas no evidence of a second cnemial crest or tuberculum fibularis is recorded. The external surface of the cnemial crest is rough for the insertion of the muscles femorotibialis, ambiens and iliotibialis (Borsuk-Białynicka, 1977). Posteriorly, the cnemial fossa is anteroposteriorly concave and proximodistally extended, showing a smooth surface for contact with the anterior crest of the fibula, as in several Titanosauriformes (e. g. Erketu, Euhelopus, Gobititan You, Tang & Luo, 2003, Magyarosaurus von Huene, 1932, Tangvayosaurus and Uberabatitan; Nopcsa, 1915; Weishampel et al., 1991; Allain et al., 1999; Ksepka & Norell, 2006; You et al., 2003; Salgado & Carvalho, 2008; Wilson & Upchurch, 2009). On the lateral surface of the proximal epiphysis there are low and longitudinal crests across a rough and triangular surface that indicate the insertion of the fibular ligament. In MCF-PVPH- 233 / 18, the diaphysis is straight, with both proximal and distal ends slightly prominent laterally in anterior view (Fig. 24 A). In Ligabuesaurus, the tibia is slender (RI = 0.21), as in Camarasaurus (Ostrom & McIntosh, 1966) and Cedarosaurus (Tidwell et al., 1999), and about half the length of the femur (length of tibia / length of femur = 0.56), which is a widespread plesiomorphic condition within Sauropoda (Upchurch et al., 2004; D’Emic et al., 2013). The diaphysis is triangular in cross-section, with the lateral and anterior rims slightly concave, especially on the distal third. The minimum shaft circumference is approximately at the mid-shaft of the bone. The distal end is exhibits a slight lateral twist with respect to the proximal end in ventral view, as in most Titanosauriformes (Salgado et al., 1997). The articular surface is rough and rectangular, being wider than long (Fig. 24 E). A deep intermalleolar groove (ascending process articular surface; Fig. 24 C, E) divides an oval lateral malleolus (anterior process) from a quadrangular and wider medial malleolus (posterior process), as in most Eusauropoda (Wilson & Sereno, 1998). The lateral malleolus is more dorsally positioned than the medial malleolus, being step-like and gently sloping medioventrally in posterior view (Fig. 24 C), as in most eusauropods (Upchurch et al., 2004). The intermalleolar groove is represented by a concave and anteroposteriorly extended surface, slightly deeper on its posterior half. Fibula (Fig. 24 J – O): The complete right fibula MCF-PVPH- 233 / 19 and the proximal end of the left fibula MCF-PVPH- 261 / 14 are included in the type material of Ligabuesaurus. Considering that the right fibula was briefly described and figured in posterior view by Bonaparte et al. (2006), only the general morphology of the fibula of Ligabuesaurus is described below. In proximal view, the proximal articular surface is rough and oval, with the medial side slightly concave and the lateral one almost convex (Fig. 24 L, N). Both anterior and posterior edges are convex, and the latter gently slopes medially. In lateral view, the dorsal surface is convex and bears a prominent posterior process (Fig. 24 J, O), as in Bonatitan, Epachthosaurus, Mendozasaurus, Rapetosaurus and Sauroposeidon (González Riga, 2003; Martínez et al., 2004; Rose, 2007; Curry Rogers, 2009; Salgado et al., 2015; González Riga et al., 2018). On the anteromedial margin of the bone there is a prominent and slender anterior fibular crest (Fig. 24 J, L, N, O), as in most Somphospondyli (Upchurch et al., 2004; Gallina & Otero, 2015). It is slightly anteriorly directed and broader distally in dorsal view, whereas it is rather ventrally directed in anterior view. Posterior to the crest, there is a wide and triangular surface that delimits the insertion area for the tibial ligament (tas; Fig. 24 J, L, N, O), a synapomorphic condition of Barapasaurus Jain et al., 1975 (Bandyopadhyay et al., 2010), Omeisaurus Young, 1939 and all neosauropods (Wilson & Sereno, 1998). Two narrow but deep ligamentous foveae open on the proximomedial margin of the fibula, as in Opisthocoelicaudia (Borsuk-Białynicka, 1977). On the posterior surface there is the muscular insertion surface for the muscle iliofibularis, which is oval and transversely concave, extending partly on the lateral and medial surfaces of the bone. In Ligabuesaurus, the fibula is straight in anterior and lateral views, with both articular ends slightly expanded, the proximal end anteroposteriorly and the distal one mediolaterally (Fig. 24 J, K), as in most Sauropoda (Upchurch & Martin, 2003). It is a slender bone (RI = 0.16), as in Huabeisaurus (RI = 0.12), Epachthosaurus (RI = 0.15) and Camarasaurus (RI = 0.17) (Ostrom & McIntosh, 1966; Martínez et al., 2004; D’Emic et al., 2013). The diaphysis is D-shaped in cross-section, with the lateral surface slightly convex and the medial one rather flat, as in Cedarosaurus (Tidwell et al., 1999). On the lateral surface of the mid-shaft there is a rough and gently prominent lateral trochanter (Fig. 24 K), which represents the surface for the insertion of the muscle flexor digitorum longus, as in most Eusauropoda (Borsuk-Białynicka, 1977; Wilson & Sereno, 1998). This lateral trochanter is proximodistally extended, with a gentle posterior inclination, and composed of two proximal crests, with the posterior crest being slightly more robust than the anterior one, as in several neosauropods (Upchurch et al., 2004; Gallina & Otero, 2015). On the proximal third of the anteromedial surface there is a short but prominent anterior trochanter (Fig. 24 K), which in MCF-PVPH- 233 / 19 is represented by a longitudinal and rough surface, as in Camarasaurus (Wilhite, 2005). The minimum shaft circumference is approximately at the distal third of the bone. The distal articular surface is triangular, showing a medially prominent astragal process in anterior view (asp; Fig. 24 J, K). Astragalus (Fig. 25): We describe and figure the right astragalus of Ligabuesaurus (MCF-PVPH- 233 / 20) that was mentioned only briefly by Bonaparte et al. (2006). The bone is pentagonal in outline in proximal view, with the anterior surface wider than the posterior one and the lateral surface longer than the medial one (Fig. 25 B), as in most sauropods (Wilson & Sereno, 1998). Furthermore, the medial margin is rounded and forms an almost right angle with the anterior surface, as in the astragalus of Euhelopus (Wiman, 1929; Wilson & Upchurch, 2009), whereas the lateral side is rather quadrangular and approaches 120 ° with the anterior side. In anterior view, the astragalus is triangular, with a prominent ascending process in lateral position and a dorsoventrally compressed medial half (Fig. 25 A), as in derived Eusauropoda and most neosauropods (Wilson & Sereno, 1998). The ascending process (pretibial process sensu Christiansen, 1997) is rectangular and posteriorly inclined in dorsal view, extending to the posterior margin of the bone, as in several neosauropods (Wilson & Sereno, 1998). The posterior surface of that process is dorsally concave and smooth, showing a posterior fossa (Fig. 25 B, D, F), as seen in other Neosauropoda (Wilson & Sereno, 1998). The posterior fossa is medially delimited by a low, wide and posteromedially directed crest that forms a tongue-like process on the posterior surface of the bone (Fig. 25 D), as in several Eusauropoda but unlike most Titanosauriformes (Mannion et al., 2013). The ascending process divides a wide and concave medial surface from a shorter and almost vertical lateral surface for the articulation of the distal ends of the tibia and fibula, respectively (Fig. 25 A, D). On the posteromedial margin of the ascending process opens a deep and oval fossa with two small foramina, of which the dorsal foramen is rounded and the ventral one is oval. No foramina or fossae are present on the anterior surface of the astragalus, a condition that Ligabuesaurus shares with all sauropods more derived than Vulcanodon Raath, 1972 (Wilson & Sereno, 1998). In MCF-PVPH- 233 / 20, the lateral surface of the astragalus is concave and smooth, without any fossae or foramina, as in most Titanosauriformes (Mannion et al., 2013). The ventral surface is medially concave in anterior view, as in Erketu, Gobititan and Mamenchisaurus (Young, 1954; Young & Zhao, 1972; You et al., 2003; Ksepka & Norell, 2006), and it is particularly rough on its anterior half, where it articulates with metatarsals I, III and IV. On the posterior margin, there is a deep and narrow groove, indicating the insertion area for the intertarsal ligament (ilg; Fig. 25 D, E), as in Mamenchisaurus (Young, 1954; Young & Zhao, 1972). Pes (Fig. 26): Considering that the right pes of Ligabuesaurus (MCF-PVPH - 233 / 21 – MCF - PVPH- 233 / 28) was only briefly described and partly figured by Bonaparte et al. (2006), we here describe the general morphology and most relevant features of all pedal elements. The pes comprises five articulated metatarsals and three phalanges that were found partly articulated with metatarsals I and II. Currently, most of the pes is still included in the matrix on its anterior surface. Metatarsus: In Ligabuesaurus, metatarsal I is the shortest element and the metatarsal III the longest, as in most Titanosauriformes (Gallup, 1989; González Riga et al., 2016). The proximal articular surface of metatarsal I (MCF-PVPH- 233 / 21) is rough, especially on its lateral half, and triangular in dorsal view, being anteriorly pointed and posteriorly wide (Fig. 26 B), as in most Sauropoda (Upchurch et al., 2004). In posterior view, the articular surface is slightly convex and ventrolaterally inclined (Fig. 26 A). The lateral margin of the proximal surface is triangular and ventrally directed, being more prominent and broader than the medial one, as in Dongbeititan (Wang et al., 2007). The diaphysis is triangular in crosssection, longer than wide, with both lateral and medial surfaces proximodistally concave in posterior view (Fig. 26 A). Lateral to the medial distal condyle there is a posterior tubercle, slightly more prominent than in Dongbeititan (Wang et al., 2007). The distal epiphysis is rectangular in ventral view and transversely extended (Fig. 26 C), exceeding the width of the diaphysis in posterior view. It is laterally twisted with respect to the proximal end and exhibits a slight ventrolateral inclination in posterior view. Thus, the lateral edge is more ventrally projected than the medial one, as in Omeisaurus, Shunosaurus Dong et al., 1983 and several Brachiosauridae (He et al., 1988; Zhang, 1988; Upchurch, 1998). The posterior surface is concave, with a wide intercondylar groove that separates a narrow and posteriorly prominent medial condyle from a wider and rounded lateral condyle. Metatarsal II (MCF-PVPH- 233 / 22) is longer than metatarsal I, shorter than metatarsal III and as long as metatarsal V (Supporting Information, Table S 4.9), as in Cedarosaurus and Epachthosaurus (Tidwell et al., 1999; Martínez et al., 2004). In dorsal view, the proximal articular surface is D-shaped and anterolaterally directed (Fig. 26 E), with both medial and lateral surfaces slightly concave posteriorly for articulation with metatarsals I and III, respectively. The articular surface is rough, especially in the posterolateral portion, and convex in posterior view (Fig. 26 D). The posterior border is concave, with prominent ends, of which the posteromedial edge is broad and dorsoventrally long, whereas the posterolateral one is rounded and laterally directed. The diaphysis is triangular in cross-section, with medial and lateral surfaces concave and convergent ventrally and with the distal third being narrower than the proximal one. A low and longitudinal crest runs from the ventral portion of the proximolateral edge to the distal third of the diaphysis, where it slopes medially. In contrast, close to the mediodistal condyle there is a rounded tubercle (Fig. 26 D), which is slightly more ventral but less prominent than in metatarsal I. The distal end exhibits a slight lateral twist with respect to the proximal end and is ventrolaterally inclined in posterior view, but less than in metatarsal I. In ventral view, the distal surface is rectangular and transversely extended, with a convex anterior surface and a concave intercondylar groove on the posterior surface (Fig. 26 F). The intercondylar groove divides a broad and rounded medial condyle from a more ventrally prominent lateral one. Metatarsal III (MCF-PVPH- 233 / 23) is the longest of the metatarsus, as in most Titanosauriformes. Moreover, this metatarsal is 60 % longer than metatarsal I, as in Antarctosaurus (von Huene, 1929; González Riga et al., 2016). The proximal articular surface is rectangular, transversely compressed and anterolaterally directed in dorsal view (Fig. 26 H). The medial border is convex posteriorly, whereas the lateral border is strongly concave for the articulation with metatarsals II and IV, respectively. The proximal articular surface is anterolaterally rough and almost flat, with a ventrolateral inclination in posterior view (Fig. 26 G). A low and longitudinal crest runs from the proximomedial margin towards the distal third of the diaphysis, where it gently slopes laterally. The diaphysis is slender and transversely compressed, especially at the mid-shaft, with medial and lateral borders dorsoventrally concave in posterior view. Dorsal to the mediodistal condyle there is a low tubercle (Fig. 26 G), which is shallower and in a more lateral position than in metatarsals I and II. The distal end exhibits a strong lateroventral inclination in posterior view. The articular surface is quadrangular, being slightly wider than long, with a convex anterior surface and a low posterior intercondylar groove, which is slightly deeper ventrally than posteriorly (Fig. 26 I). The condyles are poorly prominent and rounded, with the lateral condyle being more ventrally projected than the medial one. Metatarsal IV (MCF-PVPH- 233 / 24) is slightly shorter than metatarsal III, but longer than the rest of the elements, as in Tastavinsaurus (Canudo et al., 2008). In dorsal view, the proximal surface is trapezoidal, with a convex medial border and a strongly concave lateral border for the articulation with metatarsal V (Fig. 26 K). The proximal articular surface is rough and slightly convex in posterior view (Fig. 26 J). The diaphysis is oval in cross-section and transversely compressed on its distal third. No longitudinal crest or tubercle is recorded on the posterior surface. Distally, the intercondylar groove is shallow, and the condyles are reduced. Metatarsal V (MCF-PVPH- 233 / 25) is fan shaped in posterior view, decreasing distally from a wide and triangular proximal end (Fig. 26 L). The proximal articular surface is rough and triangular in dorsal view, being anteroposteriorly compressed and transversely extended (Fig. 26 M). The anterior border is concave, whereas the medial and posterior margins are straight and converging posteromedially in a right angle. The proximal articular surface is convex in lateral view, sloping ventrally with its lateral half (Fig. 26 L). The expanded proximal epiphysis with respect to the shaft is a condition that Ligabuesaurus shares with most sauropods, whereas it differs from the compressed proximal ends seen in Alamosaurus, Tastavinsaurus and Saltasaurus (Poropat et al., 2016). The diaphysis is oval in cross-section and straight in posterior view, with a wide proximal fossa on the posterior surface that indicates the insertion surface for the flexor muscle fibres (Borsuk-Byalinicka, 1977). The posterior surface of the diaphysis is convex distally in lateral view. The distal end is slightly expanded with respect to the diaphysis but convex ventrally. The distal articular surface is rough and posteriorly divided by a narrow and shallow groove. Phalanges: The phalangeal formula is unknown for Ligabuesaurus at present. However, the proximal and ungual phalanges of metatarsal I and the proximal phalanx of metatarsal II are preserved. Phalanx I- 1 (MCF-PVPH- 233 / 26) was found partly articulated with metatarsal I and displaced in a slightly medial direction. The proximal articular surface is rough and concave in lateral view, whereas the dorsal surface is wider than long and wedge shaped. The phalanx is oval in posterior view, showing a smooth and transversely concave surface, which is delimited dorsally by a posteriorly prominent and robust crest (Fig. 26 N). On the posterior surface, two small concavities are divided medially by a longitudinal and low crest. Distally, the articular surface is rather smooth and slightly convex. The ungual phalanx I- 2 (MCF-PVPH- 233 / 27) was found ventral to metatarsal I and anterolaterally displaced with respect to phalanx I- 1. The bone is hook shaped in lateral view, tapering distally from the proximal region (Fig. 26 O). The phalanx exhibits strong transverse compression and ventral inclination, as in most Eusauropoda (Upchurch et al., 2004). The proximal articular surface is elliptical and transversely convex, with a gentle lateral inclination in dorsal view. Close to the proximomedial margin there is a prominent and rounded process for the insertion of the muscle flexor digitorum communis brevis, which is related to partial ungual rotation during locomotion (Borsuk-Byałinicka, 1977). In dorsal view, the medial margin is slightly convex and crossed by shallow and longitudinal grooves, which are likely to represent the insertion of an unmineralized ungual cover. The proximal phalanx II- 1 (MCF-PVPH- 233 / 28) was found ventrally, but medially displaced with respect to metatarsal II. The proximal articular surface of the phalanx is rectangular, slightly wider than long, and with convex medial and lateral margins. In posterior view, this articular surface is rough and transversely concave. The proximomedial margin is posteriorly prominent and more robust than the proximolateral one in lateral view. On the distal surface, the lateral condyle is low and separated from the medial one by a wide and posteriorly extended medial groove (Fig. 26 P). Dorsal to this groove, there is a deep and almost circular excavation, which has well-defined edges but is partly filled with matrix.	en	Bellardini, Flavio, Coria, Rodolfo A, Pino, Diego A, Windholz, Guillermo J, Baiano, Mattia A, Martinelli, Augustin G (2022): Osteology and phylogenetic relationships of Ligabuesaurus leanzai (Dinosauria: Sauropoda) from the Early Cretaceous of the Neuquén Basin, Patagonia, Argentina. Zoological Journal of the Linnean Society 196 (4): 1333-1393, DOI: 10.1093/zoolinnean/zlac003, URL: https://academic.oup.com/zoolinnean/article/196/4/1333/6553819
