Simosaurus gaillardoti Meyer, 1842

Cabezuelo-Hernández, Alberto, Chaves, Carlos De Miguel, Ortega, Francisco & Pérez-García, Adán, 2024, Postcranial anatomy of the Spanish Upper Triassic sauropterygian Paludidraco multidentatus (Simosauridae), Palaeontologia Electronica (a 40) 19 (2), pp. 1-54 : 6-7

Simosaurus gaillardoti Meyer, 1842

Neotype. MNHN AC.9028, an almost complete skull (figure 50 in Rieppel , 2000; figures 1b, 2b in de Miguel Chaves et al., 2018b).

Locality and horizon. Réhainvillers, Lunéville, France; Upper Muschelkalk, Ladinian (Middle Triassic) (Hagdorn and Rieppel, 1999).

Distribution. Ladinian (Middle Triassic) levels outcropping in an area including northeastern France and southwestern Germany (Rieppel, 1994; de Miguel Chaves et al., 2018b).

Emended diagnosis (modified from de Miguel Chaves et al., 2020a). Member of Simosauridae differing from Paludidraco multidentatus by the following characters: relatively short snout; anteriorly positioned external nares; wide and oval upper temporal fenestra; oval pineal foramen, slightly displaced posteriorly; supraoccipital located below the occipital-parietal exposure; supraoccipital exposed more or less vertically on the occiput; relatively robust jaw; splenial located in the lingual surface of the jaw; teeth located dorsally in the jaw; big, conical, and blunt teeth, anchored in deep sockets (thecodont implantation); five premaxillary teeth; less than 35 dorsal vertebrae; platycoelous centra (except the most anterior cervicals); as high as long cervical to sacral centra; markedly deep neural canal of the vertebral centra (except in the anterior cervicals, unknown for the sacral and caudal vertebrae); strongly constricted dorsal centra (in ventral view); not pachyostotic sensu stricto dorsal vertebrae; transverse processes of the dorsal vertebrae with a ventral notch, and not contacting the articular surface of the centra; short zygantral wedge (from the dorsal to the sacral vertebrae, but absent in the cervicals); vertebral arches without neural keel; laterally expanded postzygapophyses of dorsal vertebrae; absence of infrapre- and infrapostzygapophyes in the cervical vertebrae; bifurcated zygosphene, with a marked ventral indentation; not pachyostotic sensu stricto dorsal ribs; absence of a marked distal expansion of the dorsal ribs; straight or slightly convex distal margin of the dorsal ribs; expanded distal region of the sacral ribs (in cranio-caudal direction); absence of clavicular foramina; T-shaped interclavicle; well-developed coracoid foramen; straight posteromedial margin of the coracoid; postacetabular process not exceeding the posterior margin of the ilium; closed obturator foramen of the pubis; notched pubis; pubis with a prepubic process; slim humerus relative to the femur; deltopectoral scar less than one fifth of the humerus total length; presence of ectepicondylar groove; not reduced spinal width of sacral vertebrae.

PALUDIDRACO de Miguel Chaves, Ortega and Pérez-García, 2018a

Paludidraco multidentatus de Miguel Chaves, Ortega and Pérez-García, 2018a

( Figures 1-15 )

Type material. Holotype, MUPA-ATZ0101 , a relatively complete and partially articulated skeleton, including the skull, both incomplete mandibular rami, most of the dorsal vertebrae and ribs, the sacral and some caudal vertebrae, and elements of the girdles and the appendicular regions ( Figures 1-15 in this study; figures 1a, 2a-e in de Miguel Chaves et al., 2018a) . Paratype, MUPA-ATZ0102 , a skull and most of the left lower jaw (figure 2f-I in de Miguel Chaves et al., 2018a) .

Type locality and horizon. El Atance fossil site (Sigüenza, Guadalajara, Central Spain). Keuper Facies. Basal Julian, Carnian (Late Triassic) (García-Ávila et al., 2021).

Distribution. Exclusively known in its type locality (de Miguel Chaves et al., 2018a).

Emended diagnosis (modified from de Miguel Chaves et al., 2020a). Member of Simosauridae differing from Simosaurus gaillardoti by the following characters: relatively elongated snout; retracted external nares; narrow upper temporal fenestra; elongated pineal foramen, close to the middle area of the skull table; horizontal exposition of the supraoccipital at the posterior end of the parietal table; supraoccipital horizontally sutured with the parietal; very slender and fragile jaw; splenial located dorsally to the dentary; teeth inserted in pleurodont implantation; numerous small, recurved, and mesiodistally compressed teeth; more than 15 premaxillary teeth; teeth situated laterally in the jaw; at least 40 dorsal vertebrae; amphicoelous centra; higher than long cervical to sacral centra; moderately deep neural canal of the vertebral centra; not strongly constricted dorsal centra (in ventral view); highly pachyostotic sensu stricto dorsal vertebrae; high transverse processes of the dorsal vertebrae, without ventral notch, contacting the articular surface of the centra; elongated zygantral wedge (at least in the posterior dorsal and the sacral vertebrae, unknown for the cervical, the anterior and the middle dorsal, and the caudal vertebrae); vertebral arches with neural keel; not laterally expanded postzygapophyses of dorsal vertebrae; presence of infrapre- and infrapostzygapophyes in the cervical vertebrae; not bifurcated zygosphene, with a slight ventral indentation; pachyostotic dorsal ribs sensu stricto; strong distal expansion of the dorsal ribs; unevenly convex distal margin of the dorsal ribs; not expanded distal region of the sacral ribs (in cranio-caudal direction); presence of two symmetrical clavicular foramina; semi-lunate interclavicle; reduced or absent coracoid foramen; angled posteromedial margin of the coracoid; postacetabular process exceeding the posterior margin of the ilium; open obturator foramen of the pubis; not notched pubis; pubis without prepubic process; massive humerus relative to the femur; deltopectoral scar one third of the humerus total length; absence of ectepicondylar groove; spinal width of sacral vertebrae notably reduced.

Figures

FIGURE 1. Postcranial skeleton of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain). Larger block, containing elements from the posterior cervical to the posterior dorsal region in: A-A’, dorsal (bottom field); B-B’, ventral (top field) view. C-I, detailed close-up of some anatomical characters discussed in the text (e.g., the prespinal lamina, the foramina on the centrum, the neural keel, and the non-bifurcated zygosphene). Dashed lines and areas represent broken bones. Scale bars represent: 100 mm (A-B’); 20 mm (C); 10 mm (D-H); 5 mm (I).

FIGURE 2. Postcranial skeleton of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain). Smaller block, containing elements from the posterior dorsal to the proximal caudal region in dorsal view (bottom field view) in: A-A’, the initial; B-B’, a more advanced stage of preparation. Dashed lines and areas represent broken bones and grey areas represent sediment. Scale bar represents 50 mm.

FIGURE 3. Isolated cervical elements of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for precise position of the elements in the field). Cervical elements shown in: A-A’, D-D’, I-I’, cranial; F-F’, J-J’, caudal; B-B’, E-E’, G-G’, L-L’, ventral; K-K’, dorsal; C-C’, H-H’, M-M’, lateral view. Arrows point to cranial direction and purple line indicates the neurocentral suture. Dashed lines and areas represent broken bones. Scale bars represent 20 mm.

FIGURE 4. Articulated cervical string of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for disarticulated elements of the specimen). Articulated cervical vertebrae shown in: A-A’, cranial; B-B’, left lateral; C-C’, caudal; D-D’, right lateral; E-E’, dorsal view. Red asterisks indicate prezygapophyses, blue asterisks indicate postzygapophyses, and purple lines indicate the neurocentral sutures. Dashed lines and areas represent broken bones and grey areas represent sediment. Scale bar represents 50 mm.

FIGURE 5. Posterior middle dorsal neural arches of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for disarticulated elements of the specimen): A-F, da#34?; G-L, da#36; M-R, da#35. Neural arches shown in: A-A’, M-M’, G-G’, cranial; B-B’, I, O, dorsal; C-C’, J-J’, N-N’, caudal; D-D’, F, K-K’, L, Q-Q’, R, ventral; E-E’, H-H’, P-P’, lateral view. Dashed lines and areas represent broken bones. Scale bars represent: 20 mm (A-E’, G-H, J-K, M-N, P-Q); 10 mm (F. I, O); 5 mm (L, R).

FIGURE 6. Posterior dorsal neural arches of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for disarticulated elements of the specimen): A-D’, da#37; E-H’, da#38; I-L’, da#39. The neural arches are shown in: A-A’, E-E’, I-I’, cranial; B-B’, F-F’, J-J’, caudal; C-C’, G-G’, K-K’, lateral; D-D’, H-H’, L-L’, ventral view. Dashed lines and areas represent broken bones. Scale bar represents 20 mm.

FIGURE 7. Posteriormost dorsal neural arches of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for disarticulated elements of the specimen): A-D’, da#40; E-H’, da#41. The neural arches are shown in: A-A’, E-E’, cranial; B-B’, F-F’, caudal; C-C’, G-G’, lateral; D-D’, H-H’, ventral views Dashed lines and areas represent broken bones and grey areas represent sediment. Scale bar represents 20 mm.

FIGURE 8. Posterior middle to posteriormost dorsal centra of the holotype of Paludidraco multidentatus (MUPA- ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for disarticulated elements of the specimen): A-D, centrum #1; E-H, #2; I-L, #3; M-P, #4; Q-T, #5; U-X, #6; Y-AB, #7; AC-AF, #8; AG-AJ, #9. The centra are shown in: A, E, I, M, U, Q, Y, AC, AG, cranial or caudal; B, F, J, N, R, V, Z, AD, AH, lateral; C, G, K, O, S, W, AA, AE, AI, dorsal; D, H, L, P, T, X, AB, AF, AJ, ventral view. Scale bar represents 20 mm.

FIGURE 9. Sacral vertebrae of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for disarticulated elements of the specimen): A-E’, sa1 and sa2; F-I, sc1; J-M, sc2. The neural arches are shown in: A-A’, cranial; B-B’, caudal; C-C’, dorsal; D-D’, ventral; E-E’, right lateral view; and the centra are shown in: F, J, cranial or caudal; G, K, dorsal; H, L, ventral; I, M, lateral view. Purple line indicates the neurocentral sutures. Dashed lines and areas represent broken bones and grey areas represent sediment. Scale bar represents 20 mm.

FIGURE 10. Last sacral vertebra and caudal vertebrae of the holotype of Paludidraco multidentatus (MUPA- ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for disarticulated elements of the specimen): A-E’, S3 and ca1; F-I, cac#1. The neural arches are shown in: A-A’, cranial; B-B’, caudal; C-C’, left lateral; D-D’, right lateral; E-E’, dorsal view; and the centrum is shown in: F, cranial or caudal; G, lateral; H, dorsal; I, ventral view. Purple line indicates the neurocentral suture. Dashed lines and areas represent broken bones and grey areas represent sediment. Scale bar represents 20 mm.

FIGURE 11. Selection of ribs of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for disarticulated elements of the specimen): A-B, rib #1; C, #2; D, #3; E, #4; F, #5; G, #6; H, #7; I, #8; J, #9; K, sr#1; L, sr#2; M, sr#3; N, #10; O, #11. Scale bar represents 20 mm.

FIGURE 12. Pectoral girdle elements of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for disarticulated elements of the specimen): A-A’, B-B’, left and right clavicles, plus interclavicula; C-C’, D-D’, left and right coracoids; E- G’, left scapula; H-J’, right scapula. The girdle elements are shown in: A-A’, C-C’, E-E’, H-H’, dorsal; B-B’, D-D’, ventral; E-E’, H-H’, lateral; G-G’, J-J’, medial view. Arrows point to the autapomorphic angled posterior border of the coracoid of P. multidentatus. Dashed lines and areas represent broken bones. Scale bar represents 50 mm.

FIGURE 13. Pelvic girdle elements of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for disarticulated elements of the specimen): A-E’, right ilium; F-G’, left ilium; H-J, left pubis; K-M, left ischium. The pelvic elements are shown in: A-A’, G-G’, H-H’, L-L’, lateral; B-B’, F-F’, I-J, L-M, medial; C-C’, posterolateral; D-D’, dorsal; E-E’, ventral view. Dashed lines and areas represent broken bones. Scale bars represent: 20 mm (A-I’, K-L’); 10 mm (J, M).

FIGURE 14. Forelimb elements of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for disarticulated elements of the specimen): A-E’, left humerus; F-K’, right humerus. The forelimb elements are shown in: A-A’, F-F’, proximal; B- B’, G-G’, dorsal; C-C’, I-I’, preaxial; D-D’, J-J’, ventral; E-E’, K-K’, postaxial; H-H’, distal view. Dashed lines and areas represent broken bones. Scale bar represents 50 mm.

FIGURE 15. Hindlimb elements of the holotype of Paludidraco multidentatus (MUPA-ATZ0101), from the Carnian (Late Triassic) of El Atance (Guadalajara, Central Spain) (see Figure S1 in the Appendix 1 for disarticulated elements of the specimen): A-E’, left femur; F-K’, right femur. The hindlimb elements are shown in: A-A’, F-F’, dorsal; B-B’, G-G’, proximal; C-C’, H-H’, preaxial; D-D’, J-J’, ventral; E-E’, K-K’, postaxial; I-I’, distal view. Dashed lines and areas represent broken bones. Scale bar represents 50 mm.