Sauropterygia

Cyamodus, copyright Ghedoghedo.

Belongs within: Lepidosauromorpha.
Contains: Eusauropterygia.

The Sauropterygia are a Mesozoic clade of marine reptiles including the plesiosaurs, placodonts and related taxa.

Synapomorphies (from Schoch & Sues 2015): Premaxilla large, forming most of the snout; lacrimal restricted to orbit or absent; palate akinetic; angle of transverse flange of pterygoid less than 45° from sagittal plane; cervical ribs with anterior process; three or more sacrals present; femur with deep groove on the posterior face of the distal end; coracoid foramen between coracoid and scapula; metatarsal V short with broad base; length of metatarsal I less than 50% that of metatarsal IV.

<==Sauropterygia
    |--Eosauropterygia H02
    |    |--Eusauropterygia H02
    |    `--Pachypleurosauridae [Pachypleurosauria] H02
    |         |--Keichousaurus hui Young 1958 H02, CWJ04
    |         `--+--Hanosaurus H02
    |            `--+--+--Dactylosaurus Gurich 1884 H02, D07
    |               |  |    `--D. gracilis [incl. D. schroederi] CWJ04
    |               |  `--Anarosaurus H02
    |               |       |--A. heterodontus H02
    |               |       `--A. pumilo H02
    |               `--+--Serpianosaurus mirigiolensis H02
    |                  `--Neusticosaurus H02 [incl. Pachypleurosaurus Cornalia 1854 D07]
    |                       |--N. edwardsi [=Pachypleurosaurus edwardsi] CWJ04
    |                       |--N. peyeri H02
    |                       `--N. pusillus H02
    `--+--Sinosaurosphargis SS15
       `--Placodontia [Placodontoidea] H02
            |--Paraplacodus Peyer 1931 H02, D07 [Paraplacodontidae]
            |    `--P. broilii H02
            `--+--Placodus Agassiz 1833 H02, D07
               |    `--P. gigas H02
               `--Cyamodontoidea H02
                    |  i. s.: Sinocyamodus xinpuensis Li 2000 H02
                    |         Psephochelys Li & Rieppel 2002 H02
                    |           `--P. polyosteoderma Li & Rieppel 2002 H02
                    |         Psephosauriscus Rieppel 2002 H02
                    |           |--P. mosis (Brotzen 1957) H02
                    |           |--P. ramonensis Rieppel 2002 H02
                    |           |--P. rhombifer [=Psephosaurus rhombifer] H02
                    |           `--P. sinaiticus H02
                    |--Cyamodontida H02
                    |    |--Psephosaurus suevicus H02
                    |    |--Henodus Huene 1936 H02, D07
                    |    |    `--H. chelyops H02
                    |    `--Cyamodus Meyer 1863 [Cyamodontidae] D07
                    |         |--C. hildegardis H02
                    |         |--C. kuhnschnyderi H02
                    |         |--C. muensteri H02
                    |         |--C. rostratus H02
                    |         `--C. tarnowitzensis H02
                    `--Placochelyida H02
                         |--Macroplacus [Macroplacidae] H02
                         |    `--M. raeticus H02
                         `--+--Protenodontosaurus [Protenodontosauridae] H02
                            |    `--P. italicus Pinna 1990 DV06
                            `--+--Placochelys [Placochelyidae] H02
                               |    `--P. placodonta H02
                               `--Psephoderma H02
                                    |--P. alpinum H02
                                    `--P. sculptata Rieppel 2002 H02

Inorganic: Placochelys placoconta minilorientalis Okamura 1987 O87

*Type species of generic name indicated

REFERENCES

[CWJ04] Cheng, Y.-N., X.-C. Wu & Q. Ji. 2004. Triassic marine reptiles gave birth to live young. Nature 432: 383–386.

[DV06] Dalla Vecchia, F. M. 2006. A new sauropterygian reptile with plesiosaurian affinity from the Late Triassic of Italy. Rivista Italiana di Paleontologia e Stratigrafia 112 (2): 207–225.

[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.

[H02] Haubold, H. 2002. Literaturbericht: Ichthyosaurier und Sauropterygier. Zbl. Geol. Paläont. Teil II 5-6: 367–403.

[O87] Okamura, C. 1987. New facts: Homo and all Vertebrata were born simultaneously in the former Paleozoic in Japan. Original Report of the Okamura Fossil Laboratory 15: 347–573.

[SS15] Schoch, R. R., & H.-D. Sues. 2015. A Middle Triassic stem-turtle and the evolution of the turtle body plan. Nature 523: 584–587.