Sauropterygia

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 [Nothosauriformes]
    |--+--LargocephalosaurusLF18
    |  `--SinosaurosphargisLF18
    `--+--EosauropterygiaH02
       |    |--EusauropterygiaH02
       |    `--Pachypleurosauridae [Pachypleurosauria]H02
       |         |  i. s.: Psilotrachelosaurus toeplitschi Nopcsa 1928B93
       |         |--KeichousaurusH02
       |         |    |--K. hui Young 1958CWJ04
       |         |    `--K. yuanensis Young 1965B93
       |         `--+--HanosaurusH02
       |            `--+--+--Serpianosaurus mirigiolensisH02
       |               |  `--NeusticosaurusH02 [incl. Pachypleurosaurus Cornalia 1854D07]
       |               |       |--N. edwardsi [=Pachypleurosaurus edwardsi]CWJ04
       |               |       |--N. peyeriH02
       |               |       `--N. pusillus (Fraas 1881)B93
       |               `--+--Dactylosaurus Gurich 1884H02, D07
       |                  |    `--D. gracilis Gürich 1884B93 [incl. D. schroederiCWJ04]
       |                  `--AnarosaurusH02
       |                       |--A. heterodontusH02
       |                       |--A. multidentatus Huene 1958B93
       |                       `--A. pumiloH02
       `--Placodontia [Placodontoidea]H02
            |--Paraplacodus Peyer 1931H02, D07 [Paraplacodontidae]
            |    `--P. broiliiH02
            `--+--Placodus Agassiz 1833H02, D07 [Placodontidae]
               |    |--P. gigas Agassiz 1833B93
               |    `--P. impressus Agassiz 1839B93
               `--CyamodontoideaH02
                    |  i. s.: Sinocyamodus xinpuensis Li 2000H02
                    |         Psephochelys Li & Rieppel 2002H02
                    |           `--P. polyosteoderma Li & Rieppel 2002H02
                    |         Psephosauriscus Rieppel 2002H02
                    |           |--P. mosis (Brotzen 1957)H02
                    |           |--P. ramonensis Rieppel 2002H02
                    |           |--P. rhombifer [=Psephosaurus rhombifer]H02
                    |           `--P. sinaiticusH02
                    |--CyamodontidaH02
                    |    |--Psephosaurus suevicusH02
                    |    |--Henodus Huene 1936H02, D07 [Henodontidae]
                    |    |    `--H. chelyops Huene 1936B93
                    |    `--Cyamodus Meyer 1863 [Cyamodontidae]D07
                    |         |--C. hildegardisH02
                    |         |--C. kuhnschnyderiH02
                    |         |--C. muensteriH02
                    |         |--C. rostratus (Münster 1830)B93
                    |         `--C. tarnowitzensis Gürich 1884B93
                    `--PlacochelyidaH02
                         |--Macroplacus [Macroplacidae]H02
                         |    `--M. raeticusH02
                         `--+--Protenodontosaurus [Protenodontosauridae]H02
                            |    `--P. italicus Pinna 1990DV06
                            `--PlacochelyidaeB93
                                 |--Placochelys placodontaH02
                                 |--Saurosphargis volzi Frech 1903B93
                                 `--PsephodermaB93
                                      |--P. alpinum Meyer 1858B93
                                      |--P. anglicum Meyer 1867B93
                                      |--P. raeticum (Schubert-Klempnauer 1975)B93
                                      `--P. sculptata Rieppel 2002H02
Inorganic: Placochelys placoconta minilorientalis Okamura 1987O87

*Type species of generic name indicated

References

[B93] Benton, M. J. 1993. Reptilia. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 681–715. Chapman & Hall: London.

[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.

[LF18] Li, C., N. C. Fraser, O. Rieppel & X.-C. Wu. 2018. A Triassic stem turtle with an edentulous beak. Nature 560: 476–479.

[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.