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FIGURE 10. Chinlechelys tenertesta NMMNH P-16697-15 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 10. Chinlechelys tenertesta NMMNH P-16697-15, Neural plates and thoracic vertebrae 1-3 in 1, anterior; 2, right lateral; 3, posterior views; and 4, a close up of the anterior process of the right rib 3.

FIGURE 26 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 26. Phylogeny resulting from our initial analysis with Eunotosaurus and two caseids included. Bremer support values above one are listed above nodes and bootstrap values above 50% are listed below nodes.

FIGURE 21 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 21. Chinlechelys tenertesta innominates: 1. Holotype innominate (P-16697-11) in distal view. 2. Proximal view. 3. Referred innominate (P-16621) distal view. 4. proximal view. Sutures are marked at the free edges of the innominate with a "s."

FIGURE 6 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 6. Outline drawing of Proganochelys quenstedti showing as shaded areas the approximate preserved portions of the shell and skull of Chinlechelys tenertesta. Numbers correspond to the suffix added to the specimen numbers in the text to identify specific fragments.

FIGURE 13. Chinlechelys tenertesta costal, NMMNH P-16697-1 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 13. Chinlechelys tenertesta costal, NMMNH P-16697-1 in 1, Dorsal and 2, ventral views; 3-5, Costals and ribs P-16697-3: 3, Ventral view and 4, line drawing; 5, Close up of dorsal side of rib in F where the costal plate has been broken away; and 6, Lateral view. Abbreviations: r, rib and c, costal.

FIGURE 1 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 1. Cladograms showing the various proposed placements of turtles (Testudines) relative to other amniotes. 1. Eunotosaurus as the ancestor of turtles (Watson, 1914). 2. Turtles as the sister group to the Dicynodontia Gardiner (1982). 3. Turtles as the sister group to the Captorhinidae (Gauthier et al., 1988). 4. Turtles as the sister group to Owenetta (Reisz and Laurin, 1991). 5. Turtles as the sister group to the Pareiasauridae (Lee, 1997). 6. Turtles as the sister group to the Sauropterygia (Rieppel and Reisz, 1999). 7. Turtles as a sister group to archosaurs (Hugal et al., 2007; Crawford et al., 2012; and Chiari et al., 2012).

FIGURE 7 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 7. Part of skull of Chinlechelys tenertesta, NMMNH P-16697-12: 1, stereograph of the left posterior portion of Chinlechelys skull in dorsal view; 2, dorsal view of same with labels. Abbreviations: po, jugal; qj, quadratojugal; ri, ridge (a and b indicate the two separate ridges referred to in the text); sq, squamosal; te, temporal emargination.

FIGURE 9. Chinlechelys tenertesta NMMNH P-16697-8,15,16 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 9. Chinlechelys tenertesta NMMNH P-16697-8,15,16, Neural plates and thoracic vertebrae 1-8 in 1, dorsal; and 2, ventral views.

FIGURE 24 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 24. Phylogeny resulting from our cladistic analysis, excluding Eunotosaurus, adding in the two autapomorphies of the Pareiasauridae and testing the position of Testudines within the Reptilia. This was based on the modified version of the Szczygielski matrix presented in this paper and run through the program TNT with multistate characters ordered. Bremer support values above one are listed above nodes, and bootstrap values above 50% are listed below nodes.

FIGURE 20. Chinlechelys tenertesta, NMMNH P-16697-14 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 20. Chinlechelys tenertesta, NMMNH P-16697-14, Hypoplastron in dorsal (1) and ventral (3) views. Line drawings of dorsal view (2) and ventral views (4). Note the suture to the pelvis in the lower right of the dorsal view and the longitudinal sulcus crossing the hypoplastron in the ventral view near the edge of the bone. Abbreviation: in, inguinal scute.

FIGURE 29 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 29. Plot showing the forelimb proportions of several putative basal turtles and the synapsid Edaphosaurus as a comparison relative to a variety of extant turtles. 1. comparison relative to various turtle taxa; and 2. comparison to different habitats of extant turtles. Figure is based on Joyce and Gauthier (2004).

FIGURE 27 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 27. Side-by-side comparison of left lateral views of the skulls of: 1. Casea. 2. Eunotosaurus. 3. Milleretta. Not to scale. Casea based on Lee (1993), Eunotosaurus based on Keysler and Gow (1981), and Milleretta based on Romer (1956).

FIGURE 15 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 15. Carapace fragments of Chinlechelys tenertesta: 1-2, NMMNH P-16697-2 costal bones in dorsal view; 3- 4, NMMNH P-16697-6, costal fragment in dorsal and ventral views; 5, NMMNH P-16697-7, costal fragment in dorsal view; and 6-7, NMMNH P-16697-5 costal fragment in dorsal view. Abbreviations: pr, dorsal process; r, rib; and s, suture.

FIGURE 18. Chinlechelys tenertesta, NMMNH P-16697- 13 in Chinlechelys from the Upper Triassic of New Mexico, USA, and the origin of turtles

FIGURE 18. Chinlechelys tenertesta, NMMNH P-16697- 13, hyoplastron and mesoplastron in 1, external view; 2, external view line drawing; and 3, internal view. 4, left axillary notch in dorsal view. Short dashes indicate sutures and longer dashes sulci and raised surface structures.

Figure 8 in Ontogenetic development of the European basal aquatic turtle Pleurosternon bullockii (Paracryptodira, Pleurosternidae)

Figure 8. Shape differences of the entoplastron of Pleurosternon bullockii (Paracryptodira, Pleurosternidae), taking into account specimens from both the Tithonian (Late Jurassic) and Berriasian (Early Cretaceous) of England. (a) Principal component analysis (PCA). Wireframes indicate the main shape changes in each PC; the light blue concerns the average shape, whereas the dark blue is the shape variance related to the extreme of variation along the axis. (b) Transformation grids to visualize shape deformation relative to the first three principal components. Abbreviations: C, CAMSM; D, DORCM; N, NHMUK.

Figure 7 in Ontogenetic development of the European basal aquatic turtle Pleurosternon bullockii (Paracryptodira, Pleurosternidae)

Figure 7. Shape differences of the anterior plastral lobe of Pleurosternon bullockii (Paracryptodira, Pleurosternidae), taking into account specimens from the Berriasian (Early Cretaceous) of Swanage (Dorset, England). (a) Principal component analysis (PCA). Wireframes indicate the main shape changes in each PC; the light blue concerns the average shape, whereas the dark blue is the shape variance related to the extreme of variation along the axis. (b) Transformation grids to visualize shape deformation relative to the first three principal components. Abbreviation: N, NHMUK.

Figure 1 in Ontogenetic development of the European basal aquatic turtle Pleurosternon bullockii (Paracryptodira, Pleurosternidae)

Figure 1. Shells of juvenile specimens of Pleurosternon bullockii (Paracryptodira, Pleurosternidae), from the Berriasian (Early Cretaceous) of Swanage (Dorset, England) (a, b, f), and detail of the carapace ornamentation of juvenile (c, e) and adult (d) individuals. (a–c) NHMUK 48262, shell in dorsal (a) and ventral (b) views, as well as detail of the ornamentation of the nuchal (c). (d) Detail of the ornamentation of the nuchal of NHMUK OR 28618 (see fig. 3B in Guerrero and PØrez-García, 2021). (e) Detail of the ornamentation of the central area of the carapace of NHMUK 48263a (see Fig. 2a). (f) NHMUK 48345, in dorsal view. Scale bars equal 2 cm in (a), (b) and (f) and 1 cm in (c)–(e).

Figure 3 in Ontogenetic development of the European basal aquatic turtle Pleurosternon bullockii (Paracryptodira, Pleurosternidae)

Figure 3. Partial shells and isolated plates of juvenile specimens of Pleurosternon bullockii (Paracryptodira, Pleurosternidae), from the Berriasian (Early Cretaceous) of Swanage (Dorset, England). (a) NHMUK 48354, in dorsal (carapace) and ventral (plastron) views. (b– c) NHMUK 48264, in dorsal (b) and ventral (c) views. (d) NHMUK 48355, in ventral view. (e) NHMUK 48352, costal plates in dorsal view. (f) NHMUK 48346, hyoplastron in dorsal view. Scale bars equal 2 cm.

Figure 5 in Ontogenetic development of the European basal aquatic turtle Pleurosternon bullockii (Paracryptodira, Pleurosternidae)

Figure 5. Shape differences of the nuchal of Pleurosternon bullockii (Paracryptodira, Pleurosternidae), taking into account specimens from the Berriasian (Early Cretaceous) of Swanage (Dorset, England). (a–b) Principal component analysis (PCA). Wireframes indicate the main shape changes in each PC; the light blue concerns the average shape, whereas the dark blue is the shape variance related to the extreme of variation along the axis. (c) Transformation grids to visualize shape deformation relative to the first three principal components. Abbreviations: C, CAMSM; D, DORCM; N, NHMUK.