taxonID	type	description	language	source
038E0354FFE5FFB37F38F909FBD1FB49.taxon	type_taxon	Type species Oistodus forceps Lindström, 1955, subsequently designated by Lindström (1971).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE5FFB37F38F909FBD1FB49.taxon	discussion	Remarks Drepanoistodus is here interpreted as quinquemembrate and comprises four nongeniculate coniform elements and one geniculate coniform element that collectively make a curvature-transition series from erect to recurved element types (e. g., Stouge & Bagnoli 1990; Rasmussen 1991). The nongeniculate elements comprise a suberectiform element associated with drepanodontiform type-l, type- 2 and type- 3 elements. In general, Middle Ordovician nongeniculate Drepanoistodus elements from Baltica can be described as follows: the suberectiform element is characterised by a straight, erect cusp. The drepanodontiform type- 1 element has a strongly recurved cusp, which is keeled both anteriorly and posteriorly. The anterior keel is twisted strongly inwards. An extension, sometimes triangular in outline, may occur at the anterobasal corner. The drepanodontiform type- 2 element has a recurved cusp which is keeled. It is separated from the drepanodontiform type-l element by the straight or only weakly twisted anterior margin, and by the consistent presence of an anterobasal flare, commonly with a triangular outline. The drepanodontiform type- 3 element is typified by a slightly recurved cusp, which is anteriorly and posteriorly keeled and not twisted. As opposed to the drepanodontiform type- 1 and type- 2 elements, it lacks the anterior triangular flare. For a more comprehensive description, see Rasmussen (1991). Many coniform conodont apparatuses are not easily placed in the locational PMS notation scheme favoured by Sweet (1981, 1988), or the more biologically correct terminology advocated by Purnell et al. (2000), because it is very difficult or even impossible to identify locational homologues with the ozarkodinid notation (Smith et al. 2005). This is primarily a consequence of the lack of natural assemblages in many conodont genera and families, including Drepanoistodus. In most cases, it is extremely difficult to distinguish between individual Middle Ordovician Drepanoistodus species based on the largely homeomorphic nongeniculate elements (van Wamel 1974; Dzik 1983; Stouge 1984; Rasmussen 2001), and this is indeed also the case with respect to the species studied herein. Because our material includes nothing but isolated conodont elements (as opposed to articulated clusters or natural multi-element assemblages), the identification of Drepanoistodus at the species level is solely based on the geniculate element, which are described below. The stratigraphical distribution of the studied specimens of Drepanoistodus is shown in Table 3.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE2FFB27F00FACDFE7FF950.taxon	description	Fig. 6 A – D	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE2FFB27F00FACDFE7FF950.taxon	diagnosis	Original diagnosis (translated from Sergeeva, 1963 [in Russian]) Inclined conodonts, almost symmetrical, with a wide shortened base, the edge of which is rounded.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE2FFB27F00FACDFE7FF950.taxon	materials_examined	Material examined 33 geniculate elements including 24 from the Lynna section.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE2FFB27F00FACDFE7FF950.taxon	description	Original description, slightly shortened (translated from Sergeeva, 1963 [in Russian]) Medium-sized conodonts (0.52 – 0.92 mm), inclined; the degree of inclination of the cusp is 45 – 60 °, sometimes up to 80 °. Base high, not very long, elongated along the CD; base length 2.5 – 3 times its height (comment by the authors: “ we find the meaning of the latter measure ambiguous ”). Base wall slightly transparent near the edge, rounded. The angle between the sides AC is more than 90 °; angle between AD 40 – 45 °; corners are smoothly obtuse. Transverse in cross section, the base is oval, elongated along CD and compressed along L 1 L 2. From the C side, the base is compressed, sometimes with a thin keel near the tip, with a small keel on side D. The sides of the base L 1 and L 2 are smooth and flat. Basal cavity is not always visible, it is wide, but not deep, without visible tops. The cusp is long, straight or slightly curved towards L 1, sharply tapering towards the tip; compressed. The sides of the cusp are almost flat, with a welldeveloped longitudinal, wide carina on L 1 and less developed carina on the side L 2. The carinae usually run from the base to the tip of the cusp. Thin keels occur on the lower (D) and upper (C) parts of the cusp.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE2FFB27F00FACDFE7FF950.taxon	discussion	Remarks In her original diagnosis, Sergeeva (1963) only included geniculate elements with a rounded basal margin in “ Oistodus ” basiovalis, which is also evident from the species epithet: basiovalis (meaning oval base). This interpretation of the geniculate element in Drepanoistodus basiovalis is followed here. Additional typical characters that may be added to the original species description include: anterior margin and upper anterior corner rounded or weakly rounded; cusp usually straight; a median or median to lower, longitudinal carina present on the inner (sometimes slightly concave) side of the element. Carina is more distinct in Darriwilian specimens than in Dapingian ones. Whereas angle A (Fig. 3) between the cusp and the upper margin is 29.6 ° with a standard deviation at 5.6, the mean ratio between the length of the free upper margin and free cusp (b / c ratio) reaches 0.40 with a standard deviation of 0.1 (Fig. 5 B).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE2FFB27F00FACDFE7FF950.taxon	distribution	Occurrence Drepanoistodus basiovalis occurs from the L. antivariabilis Zone (sample LY 12 - 9) to the interzone (“ uncertain interval ”) between the L. variabilis Zone and the Y. crassus Zone sensu Lindskog et al. (2020) in the Lynna River section (sample LY 12 - 21 b; between LY 12 - 21 and LY 12 - 22). In addition, D. basiovalis has been reported from several other localities in Baltoscandia and Poland, and also outside the Baltica palaeocontinent, e. g., New Brunswick, Argentina, Australia and China (for references, see the synonymy list above).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE3FFB17F48F8FBFD86F87B.taxon	description	urn: lsid: zoobank. org: act: 0 E 2832 F 5 - 672 E- 4 FAE-B 5 A 5 - CBA 5 DE 1 A 4824 Fig. 6 E – H	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE3FFB17F48F8FBFD86F87B.taxon	diagnosis	Diagnosis A Drepanoistodus species characterised by a geniculate element with distinct keels on the cusp and upper margin of the base; a straight basal margin; a straight to weakly rounded (convex) anterior margin and cusp which is approximately twice the length of the upper margin of the base.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE3FFB17F48F8FBFD86F87B.taxon	etymology	Etymology Named in honour of legendary guitarist Tony Iommi, founding member of heavy metal band Black Sabbath.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE3FFB17F48F8FBFD86F87B.taxon	materials_examined	Material examined Ten geniculate elements including eight from the Lynna section. Holotype, geniculate element (Fig. 6 E – F); LO 12479 T. Type locality River bank near the mouth of Lynna River, village of Kolchanovo, St. Petersburg region, Russia (60 ° 00 ′ 39 ″ N, 32 ° 33 ′ 49 ″ E). Type stratum Approximately 10 cm above the local base of the Lynna Formation, sample LY 12 - 16. Lower part of the Lenodus variabilis Zone.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE3FFB17F48F8FBFD86F87B.taxon	description	Description Cusp reclined and straight with distinct keels developed on the anterior (upper) and posterior (lower) margins. A median, longitudinal carina is developed on both sides of the cusp, but it is especially distinct on the inner side. Base is characterised by a straight or almost straight basal margin and a distinct keel on the upper margin. Whereas this keel is slightly convex, the upper margin below the keel is straight. Anterior margin is usually straight or weakly rounded (convex), but occasionally, it is strongly rounded. Angle A between the cusp and upper margin of the base is ca 30 ° (mean) with a standard deviation at 4.2 (Fig. 5 B), and the mean ratio between length of the free upper margin (b) and the free cusp (c) is 0.54 (standard deviation 0.10).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE3FFB17F48F8FBFD86F87B.taxon	discussion	Remarks In the PCA plot (Fig. 4), the population of D. iommii sp. nov. is situated in the upper right corner, separated from the D. basiovalis population as well as the other two new species populations described herein. The vectors in the biplot demonstrate that this is mainly due to the straight basal margin, the relatively long upper margin (high b / c values), and the usually straight anterior margin in D. iommii sp. nov., which is in accordance with the characters diagnosed above. The hypothesis that the population of D. iommii sp. nov. is morphologically different from the D. basiovalis population is supported by the PERMANOVA test (Fig. 5 A), which shows that the probability that the two populations are the same is exceedingly low (p (same) = 1.00 E- 04).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFE3FFB17F48F8FBFD86F87B.taxon	distribution	Occurrence The L. antivariabilis Zone (sample LY 12 - 9) to the L. variabilis Zone (sample LY 12 - 21 b). Outside the St. Petersburg region, D. iommii sp. nov. has been recorded from the L. variabilis Zone at the Hällekis quarry in Västergötland, Sweden (Mellgren & Eriksson 2010; referred to as D. aff. basiovalis) and from the L. pseudoplanus Zone or E. suecicus Zone of the island Osmussaar, Estonia (Mellgren et al. 2012; reported as D. cf. basiovalis).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFEFFAE7F74FEFEFAE7FCF2.taxon	description	urn: lsid: zoobank. org: act: 0921 F 27 A-ECF 6 - 498 C- 8943 - 4 DEB 96 CFBB 38 Fig. 6 I – L	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFEFFAE7F74FEFEFAE7FCF2.taxon	diagnosis	Diagnosis A Drepanoistodus species characterised by a geniculate element with a recurved cusp and distinct keels on both the cusp and the upper margin of the base. Weakly curved but distinct carinas are developed on both sides of the cusp, especially well developed on the inner side.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFEFFAE7F74FEFEFAE7FCF2.taxon	etymology	Etymology Named after the Danish palaeontologist and conodont specialist Svend S. Stouge, Natural History Museum of Denmark, University of Copenhagen.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFEFFAE7F74FEFEFAE7FCF2.taxon	materials_examined	Material examined Five geniculate elements including three from the Lynna section. Holotype, geniculate element (Fig. 6 J – K); LO 12483 T. Type locality River bank near the mouth of Lynna River, village of Kolchanovo, St. Petersburg region, Russia (60 ° 00 ′ 39 ″ N, 32 ° 33 ′ 49 ″ E). Type stratum Approximately 40 cm below the local top of the Volkhov Formation, sample LY 12 - 14, ca 20 cm above the base of the Lenodus variabilis Zone sensu Lindskog et al. (2020).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFEFFAE7F74FEFEFAE7FCF2.taxon	description	Description Cusp is recurved (bent weakly downward), with distinct keels developed along the anterior (upper) and posterior (lower) margins. A median, longitudinal, weakly curved carina is developed on both sides of the cusp, most distinct on the inner side of the cusp. Cusp is almost twice as long as the upper margin of the cusp; the mean ratio between the length of the free upper margin and the free cusp (Fig. 3) is ca 0.55 with a standard deviation of 0.13. Basal margin varies from rounded (convex) to almost straight. A distinct keel is developed on the upper margin. Anterior margin is rounded or weakly rounded (convex). Angle A (Fig. 3) between the cusp and upper margin of the base varies considerable with a mean of 24 ° and standard deviation of 6.9 (Fig. 5 B). Zone. L. Same specimen as I in outer view. M – O. Drepanoistodus viirae sp. nov. M. LO 12484 T, holotype, inner view, sample LY 12 - 31, interzone (“ uncertain interval ”) between the Lenodus variabilis Zone and the Yangtzeplacognathus crassus Zone sensu Lindskog et al. (2020). N. Same specimen as M in outer view. O. LO 12485 t, inner view, sample LY 12 - 31, interzone (“ uncertain interval ”) between the Lenodus variabilis Zone and the Yangtzeplacognathus crassus Zone sensu Lindskog et al. (2020). P – Q. Drepanoistodus aff. basiovalis (Sergeeva, 1963), LO 12486 t, inner and outer view, respectively, sample LY 12 - 9, L. antivariabilis Zone. R – S. Drepanoistodus stougei Rasmussen, 1991, LO 12487 t, inner and outer view, respectively, sample LY 12 - 13, L. variabilis Zone. T. Drepanoistodus cf. suberectus (Branson & Mehl, 1933), LO 12488 t, inner view, sample LY 14 - 2, Y. crassus Zone. Scale bar = 200 μm (all specimens illustrated at same scale).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFEFFAE7F74FEFEFAE7FCF2.taxon	discussion	Remarks Drepanoistodus svendi sp. nov. is distinguished from all the other Drepanoistodus species in the present study by the recurved cusp and the curved carina on each side of the cusp. Like D. iommii sp. nov., it is characterised by a clearly longer upper margin of the base compared to the cusp length than in D. basiovalis. The D. svendi sp. nov. population is located in the lower, right quadrangle of the PCA plot, far from any other species of Drepanoistodus, and the biplot vectors representing the recurved cusp and the curved carina point in this direction (Fig. 4). The PERMANOVA test on the first seven PCA axis shows that the probability that the D. basiovalis and D. svendi sp. nov. populations are the same, is exceedingly low (p (same) = 1.00 E- 04).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFEFFAE7F74FEFEFAE7FCF2.taxon	distribution	Occurrence The lower part of the L. variabilis Zone (samples LY 12 - 13, LY 12 - 14). Moreover, D. svendi sp. nov. has been recorded from Steinsodden, Norway, from the top of the B. norrlandicus – D. stougei Zone and the base of the overlying B. medius – H. holodentata Zone, which correlate with the middle part of the L. variabilis Zone (as D. aff. basiovalis sensu Rasmussen 2001), and from the L. pseudoplanus Zone or E. suecicus Zone at the island Osmussaar, Estonia (Mellgren et al. 2012; reported as D. aff. basiovalis).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFFFFAD7F70FC9DFCB2F8A3.taxon	description	urn: lsid: zoobank. org: act: AD 10 D 9 B 3 - 9802 - 4 DAC- 97 C 0 - B 44 EB 8 DE 195 D Fig. 6 M – O	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFFFFAD7F70FC9DFCB2F8A3.taxon	diagnosis	Diagnosis A Drepanoistodus species characterised by a geniculate element with a wide, straight, compressed cusp and a very short base, where the free cusp typically is ca 4 times longer than the upper margin of the base.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFFFFAD7F70FC9DFCB2F8A3.taxon	etymology	Etymology Named after the Estonian palaeontologist and conodont specialist Viive Viira, Tallinn University of Technology, Estonia.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFFFFAD7F70FC9DFCB2F8A3.taxon	materials_examined	Material examined Nine geniculate elements including five from the Lynna section. Holotype, geniculate element (Fig. 6 M – N); LO 12484 T. Type locality River bank near the mouth of Lynna River, village of Kolchanovo, St. Petersburg region, Russia (60 ° 00 ′ 39 ″ N, 32 ° 33 ′ 49 ″ E). Type stratum Approximately 15 cm above the local base of the Sillaoru Formation, sample LY 12 - 31. Lower part of the 90 cm thick interzone (“ uncertain interval ”) between the Lenodus variabilis Zone and the Yangtzeplacognathus crassus Zone sensu Lindskog et al. (2020).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFFFFAD7F70FC9DFCB2F8A3.taxon	description	Description Cusp is reclined, wide (from upper to lower margin) and straight, with keels developed along the anterior (upper) and posterior (lower) margins. A weak, median, longitudinal carina is developed on the inner side of the cusp. Occasionally, the carina may be distinct. Basal margin is weakly rounded or straight. A distinct keel is developed on the upper margin. Anterior margin is rounded or weakly rounded (convex). Angle A (Fig. 3) between the cusp and upper margin of the base is ca 30 ° (mean) with a standard deviation of 4.3 (Fig. 5 B), and mean ratio between length of the free upper margin and the free cusp is ca 0.25 with a standard deviation of 0.05.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFFFFAD7F70FC9DFCB2F8A3.taxon	discussion	Remarks Drepanoistodus viirae sp. nov. is situated in the lower left quadrangle of the PCA plot (Fig. 4). Like D. basiovalis, it is clearly separated from D. iommii sp. nov. and D. svendi sp. nov., whereas it partly overlaps with the D. basiovalis population, when only the PC 1 (x) and PC 2 (y) axis is plotted. The vectors in the biplot reinforce that D. viirae sp. nov. is characterised by a convex basal margin, a weakly developed carina and a short upper margin on the base (= low b / c value), the latter because it is situated in the opposite direction of the b / c vector, as seen in Fig. 4. The partial overlap with D. basiovalis occurs because the two species share some characters. A significant difference, however, is that D. viirae sp. nov. has a relatively shorter upper margin of the base, where the mean b / c ratio is 0.40 in D. basiovalis but only 0.25 in D. viirae sp. nov. (Fig. 5 B). Moreover, D. viirae sp. nov. is characterised by a wider cusp when viewed from the side and, typically, a less developed carina on the cusp. The hypothesis that the D. viirae sp. nov. population is morphologically separate from the D. basiovalis population is supported by the PERMANOVA test (Fig. 5 A), which shows that the probability that the two populations are the same is low (p (same) = 8.00 E- 03). Drepanoistodus viirae sp. nov. is distinguished from the stratigraphically older Drepanoistodus contractus on the relatively wider and more compressed cusp and the usually less distinct longitudinal carina, and from D. cf. suberectus on the markedly smaller angle between the cusp and the upper margin of the base (mean angle = 46 ° in D. cf. suberectus, 30 ° in D. viirae sp. nov.).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFFFFAD7F70FC9DFCB2F8A3.taxon	distribution	Occurrence The lower part of the L. variabilis Zone (sample LY 12 - 13) to the lower part of the interzone (“ uncertain interval ”) between the L. variabilis Zone and the Y. crassus Zone (sample LY 12 - 31) sensu Lindskog et al. (2020). In addition, D. viirae sp. nov. has been recorded from the B. norrlandicus and basal Y. crassus zones at Gillberga, Sweden (Löfgren 2000 b, 2003); the uppermost part of the P. rectus – M. parva Zone at Steinsodden, Norway, which correlates with the uppermost P. originalis Zone (as D. cf. stougei sensu Rasmussen 2001); the lower part of the B. medius – H. holodentata Zone at Andersön, Sweden, correlating with the uppermost part of the L. variabilis Zone (as D. cf. basiovalis sensu Rasmussen 2001), and the L. variabilis Zone at Hällekis, Sweden (as D. aff. suberectus sensu Mellgren & Eriksson 2010). Moreover, it shares some characteristics with the geniculate element from strata correlated with the L. pseudoplanus Zone of the Canning Basin, Australia, which was included in D. basiovalis (Zhen 2020: fig. 7 b), but this identification is questionable.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFCFFAB7CE8F89FFB0EFB7D.taxon	description	Fig. 6 P – Q	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFCFFAB7CE8F89FFB0EFB7D.taxon	materials_examined	Material examined Seven geniculate elements including five from the Lynna section.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFCFFAB7CE8F89FFB0EFB7D.taxon	discussion	Remarks The specimens assigned to Drepanoistodus aff. basiovalis herein share some characters with D. basiovalis, D. iommii sp. nov. and D. stougei, but do not meet the full criteria of any of these species. The most significant character is an extended upper keel anteriorly, which may be angular (see Fig. 6 P – Q) or rounded. Cusp is reclined and straight with distinct carinas on both sides of the cusp. Anterior margin varies from almost straight to rounded (convex). The upper anterior corner is angular or weakly rounded. The basal margin is usually slightly convex. The cusp is often nearly twice as long as the upper margin of the base, but it varies considerably (b / c ratio mean = 0.46, standard deviation 0.14). Similarly, angle A is very variable with a mean near 28 ° and standard deviation at 6.55 (Fig. 5 B). Specimens with a rounded anterior edge share similarity with Drepanoistodus stougei Rasmussen, 1991 but are distinguished by the extended upper keel anteriorly, and a more narrow and distinct carina. More material and analyses are needed to assess if this taxon represents a separate species. Thus, for the time being, these specimens are left under open nomenclature.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFCFFAB7CE8F89FFB0EFB7D.taxon	distribution	Occurrence The L. antivariabilis Zone (sample LY 12 - 9) to the basal part of the L. variabilis Zone (sample LY 12 - 14). Moreover, it has been recorded from the B. norrlandicus Zone at Gillberga, Sweden (Löfgren 2000 a, as D. cf. basiovalis); the L. variabilis Zone at Hällekis, Sweden (Mellgren & Eriksson 2010); and also from the L. pseudoplanus Zone of the Argentine Precordillera (Serra et al. 2019, as D. basiovalis) and Histiodella kristinae Zone of Zhejiang, China (Wu et al. 2020, as D. basiovalis).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFAFFAB7F35FB06FDC1F869.taxon	description	Fig. 6 R – S	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFAFFAB7F35FB06FDC1F869.taxon	materials_examined	Material examined 22 geniculate elements including 17 from the Lynna section.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFAFFAB7F35FB06FDC1F869.taxon	discussion	Remarks Drepanoistodus stougei was first described by Rasmussen (1991) and further morphological details for all the four element types were subsequently added by Rasmussen (2001). The most distinct features are the rounded anterior margin and the relatively long upper margin on the base. In the material at hand, the b / c ratio (see Fig. 3) mean is 0.50 and angle A has a mean of 27.4 °. In some cases, D. svendi sp. nov. is characterized by a similarly rounded anterior margin but is distinguished by its (weakly) curved cusp and carina. Drepanoistodus aff. basiovalis morphotypes with a rounded anterior margin are separated from D. stougei by the characteristically extended keel in the upper anterior corner of the former taxon. Because D. stougei is included here just for comparison with the new species described, synonymy or further descriptive details have not been incorporated, but can be found in Rasmussen (1991, 2001).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFAFFAB7F35FB06FDC1F869.taxon	distribution	Occurrence From the Lenodus antivariabilis Zone (sample LY 12 - 5) to the basal part of the interzone (“ uncertain interval ”; sample LY 12 - 29) between the L. variabilis Zone and the Y. crassus Zone sensu Lindskog et al. (2020) in the Lynna River section.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFBFFAA7CDBFEFEFDE7F9AD.taxon	description	Fig. 6 T	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFBFFAA7CDBFEFEFDE7F9AD.taxon	materials_examined	Material examined Four geniculate elements including three from the Lynna section.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFBFFAA7CDBFEFEFDE7F9AD.taxon	discussion	Remarks Drepanoistodus cf. suberectus is included in the present work because it superficially resembles Drepanoistodus viirae sp. nov. Originally, D. suberectus was described as Oistodus suberectus from the Upper Ordovician strata of Missouri, USA, by Branson & Mehl (1933), but it was not until 1966 that conodont specialists included the geniculate element in the apparatus (see Bergström & Sweet 1966 and Webers 1966, for details). The D. suberectus type locality near Ozora, Missouri, was located and restudied by Bergström & Leslie (2010) who documented the conodont fauna and illustrated three different elements of D. suberectus, including the geniculate element. The Upper Ordovician geniculate D. suberectus elements (e. g., Stauffer 1935; Nowlan 2002; Bergström & Leslie 2010) are generally more rounded anteriorly and carry more pronounced keels on the cusp than the three geniculate elements at hand, thus leading us to leave the Lynna River specimens in open nomenclature. Drepanoistodus cf. suberectus occurs only sporadically in the Lynna River section samples. It is characterised by a short upper margin of the base compared to the free cusp (b / c ratio near 0.20 in the three specimens found). Angle A between the upper margin of the cusp and the carina on the cusp (see Fig. 3) varies considerably (41 – 52 °) but it is wider than that of the other Drepanoistodus species described here. Moreover, it is typified by a convex basal margin; weakly rounded anterior margin, and a weakly developed carina on the straight cusp, which is located on the lower half part of the cusp. Superficially, D. cf. suberectus resembles D. viirae sp. nov. because of the relatively short base, but the latter species is distinguished by a narrower angle A (see Fig. 3); wider sides anteriorly on the cusp; laterally compressed cusp with distinct keels, and a median, as opposed to a lower, carina.	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
038E0354FFFBFFAA7CDBFEFEFDE7F9AD.taxon	distribution	Occurrence The Yangtzeplacognathus crassus Zone at Lynna River (samples LY 12 - 34, LY 14 - 2 and LY 14 - 5). Drepanoistodus cf. suberectus has also been documented from the L. variabilis Zone of Hällekis, Sweden (Mellgren & Eriksson 2010).	en	Rasmussen, Jan Audun, Eriksson, Mats E., Lindskog, Anders (2021): Middle Ordovician Drepanoistodus (Vertebrata, Conodonta) from Baltica, with description of three new species. European Journal of Taxonomy 774: 106-134, DOI: https://doi.org/10.5852/ejt.2021.774.1533, URL: http://dx.doi.org/10.5852/ejt.2021.774.1533
