taxonID	type	description	language	source
7F4D879C7579FF9FFAA4FAFDD793FD0A.taxon	description	No ossification has occurred. The trabecula communis extends under the eyes, but not far rostral to them resulting in a very short prenasal process. The process is slightly flexed ventrally. Meckel’s cartilage is in articulation with the quadrate cartilage, but is short as the beak is only weakly developed. The quadrate cartilage itself is triradiate. The infrapolar process is small, and is located dorsal to the quadrate cartilage. The pars canaliculi of the auditory capsule are round in shape and fully chondrified. The ceratohyal and hypohyal are fused to form a curved element directly posterior to the quadrate cartilage. Stage 32 There is no ossification present in the skull. The prenasal process exceeds Meckel’s cartilage in length, and remains triangular in lateral view. It remains slightly flexed ventrally. The parietotectal cartilage is RM, Redpath Museum. Asterisk denotes elements that ossify variably with respect to stage. growing posteriorly over the nasal capsule, and is dorsoventrally flattened. The postorbital cartilage has formed behind the orbit. The pars canaliculi of the auditory capsule are dorsally elongated, becoming more ovoid than in the previous stage. Anteroventrally, they are in close contact with the quadrate cartilage. The columella is situated posterior to the quadrate cartilage. Meckel’s cartilage is considerably more elongate than in the previous stage, and has developed a retroarticular process. The basibranchial portion of the hyoid apparatus is approximately equal to the retroarticular cartilage in posterior extent. Stage 33 The skull remains unossified. The prenasal process has straightened and forms a distinct angle with the posterior nasal septum, although outgrowth of the beak has been limited. Meckel’s cartilage remains considerably shorter than the prenasal process. The infrapolar process has increased in prominence. The foramen for the ophthalmic artery is oval, with its long axis parallel to the long axis of the skull. Stage 34 The prenasal process is slightly more elongate than in the previous stage, but the greatest amount of growth has been in the lower jaw, which is now almost equal to the prenasal process in anterior extent. The two rami of Meckel’s cartilage share a broad contact. The area between the parietotectal cartilage and the prenasal process is not well chondrified. The external narial opening cuts a trough in the underlying trabecula, but does not form a discrete perforation in the nasal septum because of weak chondrification. The angular is ossifying. Later in this stage (Fig. 1 A), the squamosal ossifies around the quadrate articulation. The palatine, pterygoid, jugal, and quadratojugal are also ossifying. In the lower jaw, the dentary and supra-angular ossify. The ossification of the jugal is variable, as it is absent in some stage 35 individuals (RM 8021, RM 8053). Stage 35 The jugal process of the premaxilla is present. The angle between the prenasal process and the nasal capsule has decreased relative to stage 34. The base of the interorbital cartilage curves ventrally to a point just rostral to the external nares before it flattens out to form the prenasal process. The external narial opening is slit-like, with its long axis parallel to the prenasal process. The perforation in the underlying cartilage corresponding to the narial opening is complete. Later in this stage, the parasphenoid rostrum, palatal and frontal processes of the premaxilla, the vomer, and lacrimal are ossifying. The jugal and frontal processes of the premaxilla ossify from separate centres, as do the dorsal and ventral portions of the orbital process of the lacrimal. The dorsal ossification centre of the orbital process of the lacrimal Dromaius novae- D. novaehollandiae Rhea Struthio Eudromia Element hollandiae (RM) (YPM) americana camelus elegans Skull Basioccipital 14 – 21 8 8 14 – 15 5 Exoccipital 14 7 8 16 7 Supraoccipital 18 7 6 14 7 Parasphenoid rostrum 6 3 3 5 4 Parasphenoid ala 12 7 6 16 7 Parasphenoid lamina 14 4 4 16 4 Basisphenoid 10 – 12 4 – 7 6 8 – 10 4 – 6 Laterosphenoid 13 – 18 10 8 16 7 Prootic 25 19 8 17 7 Opisthotic 22 12 8 18 7 Epiotic 21 13 8 18 8 Squamosal 3 2 – 4 2 4 3 Parietal 12 6 6 7 4 Frontal 11 6 6 8 4 Lacrimal 6 4 2 6 4 Mesethmoid 18 8 8 14 7 Trabeculae 22 – 24 23 Nasal 8 3 4 6 3 Premaxilla 4 2 2 5 2 Maxilla 7 3 2 4 3 Palatine 3 3 2 5 3 Pterygoid 3 3 2 3 – 5 3 – 4 Vomer 5 3 2 6 3 Jugal 3 – 5 3 2 5 3 Quadratojugal 2 1 – 3 2 4 2 Quadrate 11 6 5 11 4 Ectethmoid Dentary 2 1 4 3 3 Supra-angular 2 1 2 4 3 Angular 1 3 2 4 3 Splenial 7 4 4 5 3 Prearticular 9 5 4 10 4 – 6 Articular 23 13 – 18 9 19 Mandibular Entoglossal Basihyal Urohyal Ceratobranchial 13 6 5 9 – 11 4 Epibranchial Postcranial axial skeleton Cervical centra 15 7 5 13 7 Thoracic centra 15 7 4 11 4 – 6 Synsacral centra 16 7 7 11 4 – 6 Caudal centra 19 – 24 11 – 13 16 – 18 Pygostyle 27 – 29 21 20 Cervical neural arch 17 9 8 14 7 Thoracic neural arch 20 9 – 11 9 14 8 Synsacral transverse processes 27 15 – 16 10 19 Caudal transverse processes 17 20 – 22 Synsacral arch 19 – 21 11 21 Cervical ribs 17 7 7 14 8 Dorsal ribs 3 – 7 4 5 7 4 Sternal ribs 15 7 9 22 – 23 Uncinate processes 11 RM, Redpath Museum; YPM, Peabody Museum. If an element is unnumbered, it was unossified in all specimens examined. If two numbers are given, these represent the range of ranks over which a variable element can ossify. forms slightly before the ventral centre. The orbital process forms in contact with a cartilaginous lateral extension of the ectethmoid. The vomer is ossifying from paired centres. The lacrimal, parasphenoid rostrum, and frontal process of the premaxilla ossify variably, as they are occasionally unossified in early stage 36 individuals (RM 8022). Stage 36 The beak has outgrown to the point where the angle between the cartilaginous prenasal process and the nasal septum has been eliminated. The splenial is ossifying along the medial margin of the lower jaw. The jugal and palatal processes of the maxilla are ossifying. The jugal and frontal processes of the premaxilla retain separate ossification centres. This is followed by the ossification of the nasal from a single centre lying along the roof of the nasal capsule. The prearticular ossifies along the posterior medial margin of the lower jaw. The squamosal is long and thin, forming a spur paralleling the otic process of the quadrate cartilage and also forming an arch around the external auditory meatus. The dentary is ossifying from multiple centres along the anterior portion of the lower jaw. The hyoid apparatus remains short and stout. Late in this stage, the basisphenoid ossifies. The two ossification centres of the lacrimal remain unfused, as do the two ossification centres of the premaxilla. Stage 37 (Fig. 2 E) The frontal is ossifying along the dorsal margin of the orbit. The body of the quadrate is ossified. The ossification centres of the lacrimal have fused, as have the premaxillary ossification centres. Later in this stage, the parietal and the parasphenoid alae ossify. The parasphenoid alae form a plate of bone ventral to the postorbital cartilage; this cartilage remains unossified. Stage 38 (Fig. 1 B) The premaxilla has completely surrounded the cartilaginous prenasal process. The frontal has expanded its ossified area ventrally into the orbit. The ceratobranchials are ossifying. The laterosphenoid is also ossifying from its ventrolateral corner. This is followed by the ossification of the exoccipitals and parasphenoid lamina. The parasphenoid lamina ossifies from right and left paired ossification centres located posterior to the parasphenoid rostrum and basisphenoid. Otoliths are calcified. The laterosphenoid is variable in its timing of ossification, as it is cartilaginous in some stage 40 + individuals (RM 8047). Stage 39 The lacrimal has a large foramen on the anterior surface of the descending process. The supraoccipital is ossifying from a single centre; this appears to be variable as two centres on either side of the cranial midline were observed in some individuals. The laterosphenoid is ossified along its entire ventral edge. The mesethmoid is ossifying from two centres – one on the anteroventral edge of the interorbital septum, the second located in the lamina dorsalis representing the ossification of the parietotectal cartilage. The lamina dorsalis has extensive dorsal exposure in D. novaehollandiae, first as cartilage and later as bone. It is bordered rostrally by the frontal process of the premaxilla (which does not contact the frontal), laterally by the nasals and frontals and in later stages, posteriorly by the frontals. The supraoccipital and mesethmoid are variable in their timing of ossification, remaining unossified in some stage 40 + individuals (RM 8047). Stage 40 + Day 36: The basioccipital is ossifying as a single linear ossification centre on the cranial midline. The ossified area of the laterosphenoid has expanded to include the entire lateral edge. The epiotic is beginning to ossify from the medial margin of the supraoccipital. It does not yet have lateral exposure. The ossified portion of the parietal has expanded to reach the posterior wall of the orbit. There is an extra medial ossification centre of the parasphenoid lamina, located between the two principal wings of that element. Day 38: The basioccipital is elongate and diamondshaped, broadening posteriorly. The laterosphenoid is entirely ossified. The opisthotic ossifies separately from the exoccipital, and is exposed along the lateral wall of the braincase. The ossified portion of the lamina dorsalis of the mesethmoid contacts the frontals posteriorly, but is not overlapped by any elements. The interorbital septum is ossified over the anterior third of the element. The articular is ossified, beginning from the centre of the jaw joint. There also appears to be some bony ossicles in the jaw joint that are separate from the articular, and may represent sesamoid elements termed ossicula articularia (Jollie, 1957). Day 43 (Fig. 1 C): The opisthotic contacts the squamosal, forming the posterior border of the external auditory meatus. · Day 45: The prootic ossifies medial to the squamosal. It is not visible in lateral view.	en	Maxwell, Erin E. (2009): Comparative ossification and development of the skull in palaeognathous birds (Aves: Palaeognathae). Zoological Journal of the Linnean Society 156 (1): 184-200, DOI: 10.1111/j.1096-3642.2009.00533.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2009.00533.x
7F4D879C757FFF9FF857FD5BD2C9FA86.taxon	description	No ossification is present at this stage. The prenasal process is slightly swollen at its tip, and is only slightly longer than Meckel’s cartilage. The roof of the nasal tectum has grown posteriorly, dorsal to the orbits. The pars canaliculi of the auditory capsule is prominent, encompassing the entire lateral posterior margin of the skull. The contact between the two rami of Meckel’s cartilage is relatively narrow. Stage 35 The contact between the two rami of Meckel’s cartilage becomes broader in this stage. The squamosal, palatine, vomer, pterygoid, jugal, and quadratojugal are ossifying. The lacrimal is ossifying, beginning from its orbital process. The frontal process of the premaxilla is ossifying, as is the jugal process of the maxilla. The supra-angular and angular are ossified in the lower jaw. This is followed by the ossification of the parasphenoid rostrum. Stage 37 (Fig. 2 C) The nasal is ossifying, as are the splenial, prearticular, and dentary. The jugal process of the premaxilla is ossified, but is not fused with the frontal process. The maxilla is triradiate. There are two independent, parallel ossification centres posterior to the parasphenoid rostrum; these represent the initiation of ossification of the parasphenoid lamina. The squamosal forms a process that parallels the otic process of the quadrate. Stage 38 (late) The parietal and frontal are ossifying, as are the quadrate and the ceratobranchials. Stage 40 + Day 22: The supraoccipital is ossifying from a single centre. The parasphenoid alae are ossifying, as is the basisphenoid. The lacrimal is triradiate. Although the nasal lacks a descending process, the ascending process of the maxilla in R. americana is much better developed than in D. novaehollandiae. There is a hole located in the middle of the squamosal, perhaps because of osteological restructuring caused by muscle development, as hypothesized for Meleagris gallopavo (Maxwell, 2008 a). Day 26 (Fig. 1 J): The basioccipital, exoccipital, laterosphenoid, prootic, opisthotic, epiotic, and mesethmoid are ossifying. The lamina dorsalis of the mesethmoid is ossifying from paired ossification centres, rather than from a single median centre. The prearticular has developed a second ossification centre, located along the posterior edge of the articular cartilage. Day 28: The facial region of the skull has become extremely elongate. The articular is ossifying, and the dermal bones of the skull roof are in contact. Day 30: The opisthotic and epiotic have developed large lateral exposures (Fig. 2 D).	en	Maxwell, Erin E. (2009): Comparative ossification and development of the skull in palaeognathous birds (Aves: Palaeognathae). Zoological Journal of the Linnean Society 156 (1): 184-200, DOI: 10.1111/j.1096-3642.2009.00533.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2009.00533.x
7F4D879C757FFF91FAEFFAB7D2EDFF71.taxon	description	Day 15 (Fig. 1 F): There is no ossification in the skull. The prenasal process is straight and narrow. The roof of the nasal capsule is chondrified. It widens posteriorly, and contacts the orbits laterally. There is an angle formed between the nasal capsule and the prenasal process. The contact between these two structures occurs near the proximal end of the prenasal · process. The cartilages of both the upper and lower jaw are elongate; the upper jaw extends further anteriorly than the lower jaw. The lower jaw is y-shaped, with the two rami contacting each other medially along a broad contact. The retroarticular process of Meckel’s cartilage extends posterior to the quadrate articulation. The pars canaliculi retain their ovoid morphology, and do not contact each other posteriorly. There is a dorsally directed chondrification originating from the anteroventral margin of the pars canaliculi, ventral to the external auditory meatus. This represents the metotic cartilage. The definitive occipital arch is ventral and medial to the pars canaliculi, and is distinct from this element. The quadrate cartilage and stapes are present. Day 16: The beak is slightly longer than in the younger embryo. The prenasal process is slightly hooked at the tip, and is also wider. The pterygoid is ossifying. The dentary is also ossifying from the ventral surface of the mandibular symphysis. The timing of onset of ossification is variable, with some day 17 embryos lacking ossified skull elements (YPM 112440). Day 17: The maxilla is weakly ossified near the base of the ascending process. The squamosal is ossifying around the quadrate articulation. The quadratojugal, supra-angular, and angular are also ossifying. Day 19: The parasphenoid rostrum, parietal, lacrimal, nasal, premaxilla, palatine, vomer, jugal, and splenial are ossifying. The lacrimal, parietal, nasal, and vomer are variable in their timing of ossification, being absent in some day 21 embryos (YPM 112444). Day 21: The hyoid apparatus is more elongate, extending posterior to the external auditory meatus. There is a process of the metotic cartilage overlying the quadrate articulation. The squamosal is anterior to this. The prenasal process is not completely enveloped by the premaxilla. Its anterior tip has a spatulate morphology. The frontal is ossifying, as is the ceratobranchial. The ceratobranchials are variable in the timing of ossification, remaining cartilaginous in some day 22 embryos (YPM 112446, YPM 112447). Day 22: The basisphenoid and prearticular are ossified. The premaxilla completely covers the prenasal process. The basisphenoid is variable in its timing of ossification, being absent from some day 23 to day 25 embryos (YPM 112448, YPM 112450). Day 23 (Fig. 1 G): The quadrate is ossifying (Fig. 2 A); this is variable as it is cartilaginous in some day 24 embryos (YPM 112449). The maxilla lacks a distinct ascending process, although it is triangular at its midpoint. The nasal lacks a descending process. Day 26: The basioccipital is ossifying from paired linear ossification centres along the cranial midline. The parasphenoid alae and lamina are now ossified. Day 28: The two ossification centres of the basioccipital have fused into a single oblong element (Fig. 2 B). The supraoccipital is ossifying, as are the laterosphenoid, exoccipital, and prootic. Both the lamina dorsalis and interorbital septum of the mesethmoid are ossified. The prearticular extends along the medial surface of the lower jaw, and posteriorly along the anterior portion of the medial process. The nasal has an ossified descending process. The ossification of the prootic and the lamina dorsalis of the mesethmoid are variable in timing of occurrence, and remain cartilaginous in some day 30 – 32 embryos (YPM 112454, YPM 112455, YPM 112458). Day 30: There is a large patch of reduced ossification in the centre of the squamosal, corresponding to changes in bone architecture. This is similar to what was seen in stage 40 + (day 22) R. americana, and stage 39 M. gallopavo (Maxwell, 2008 a). Day 31: The stapes is ossified. This is followed by the ossification of the opisthotic and epiotic. The epiotic ossifies from the anterolateral margin of the supraoccipital. The calvarium is very heavily ossified, with all dermal roofing elements contacting each other (Fig. 1 H). Day 36: The nasal trabeculae are ossifying, but this event is very variable in timing and they remain cartilaginous in some day 37 – 38 individuals (YPM 112462, YPM 112464, YPM 112465). Day 38: The articular is ossifying from the dorsal surface of the medial process.	en	Maxwell, Erin E. (2009): Comparative ossification and development of the skull in palaeognathous birds (Aves: Palaeognathae). Zoological Journal of the Linnean Society 156 (1): 184-200, DOI: 10.1111/j.1096-3642.2009.00533.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2009.00533.x
7F4D879C7571FF91FAECFEC0D5FCFA29.taxon	description	Day 10: The prenasal process is curved ventrally, as is the area of the lower jaw where the rami of Meckel’s cartilage are in contact. Dorsal outgrowth of the trabecula communis in the area of the nasal capsule initiates the formation of the parietotectal cartilage and the preoptic root of the orbital cartilage. The jugal and frontal processes of the premaxilla are ossified, as is the quadratojugal. Day 11 (Fig. 1 D): The prenasal process is straighter than in younger embryos, and only a slight terminal hook remains. The squamosal, premaxillary process of the nasal, maxilla, palatine, vomer, and jugal are ossifying, as are the dentary, supra-angular, angular, and splenial. This is followed by the ossification of the parasphenoid rostrum and lamina, the basisphenoid, parietal, frontal, lacrimal, pterygoid, quadrate, prearticular, and ceratobranchials. The ossification of the quadrate is variable, as it does not always ossify before day 12 (YPM 112522). The premaxilla completely covers the prenasal process. The maxillary process of the nasal does not contact the nasal process of the maxilla. The beak forms a rigid ossified framework, but the calvarium is not well ossified. Day 12: The basioccipital is ossifying. Day 14: The exoccipital, laterosphenoid, prootic, opisthotic, epiotic, and mesethmoid are ossifying (Figs 1 E, 2 F). The supraoccipital is ossifying from a single centre. The mesethmoid lacks a broad dorsal exposure.	en	Maxwell, Erin E. (2009): Comparative ossification and development of the skull in palaeognathous birds (Aves: Palaeognathae). Zoological Journal of the Linnean Society 156 (1): 184-200, DOI: 10.1111/j.1096-3642.2009.00533.x, URL: https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/j.1096-3642.2009.00533.x
