Pachypleurosauria

Pachypleurosaurs Temporal range: Induan-Carnian,
Keichousaurus
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	†Sauropterygia
Clade:	†Eosauropterygia
Suborder:	†Pachypleurosauria Nopcsa, 1928
Genera
†Diandongosaurus †Hanosaurus †Honghesaurus †Majiashanosaurus †Qianxisaurus †Wumengosaurus †Keichousauridae †Dianopachysaurus †Keichousaurus †Pachypleurosauridae †Anarosaurus †Dactylosaurus †Luopingosaurus †Neusticosaurus †Odoiporosaurus †Prosantosaurus †Serpianosaurus

Pachypleurosaurus

Pachypleurosauria is an extinct clade of primitive sauropterygian reptiles that vaguely resembled aquatic lizards, and were limited to the Triassic period. They were elongate animals, ranging in size from 0.2–1 metre (0.66–3.28 ft), with small heads, long necks, paddle-like limbs, and long, deep tails. The limb girdles are greatly reduced, so it is unlikely these animals could move about on land. The widely spaced peg-like teeth project at the front of the jaws, indicating that these animals fed on fish. In the species Prosantosaurus, it was observed that they fed on small fishes and crustaceans which they devoured entirely and that its teeth regrew after they broke off. This was the first observation of tooth replacement in a European pachypleurosaur, the only other discovery of such an event was made in China.

Classification

Pachypleurosaurs were originally and are often still included within the Nothosauroidea (Carroll 1988, Benton 2004). In some more recent cladistic classifications, however, (Rieppel 2000), they are considered the sister group to the Eosauropterygia, the clade that includes the nothosaurs and plesiosaurs. In the 2023 description of Luopingosaurus, Xu et al. found support for a similar hypothesis, recovering Pachypleurosauroidea as the sister taxon to the Eusauropterygia, a clade which contains both Nothosauroidea and Pistosauroidea. The results of their phylogenetic analyses are shown in the cladogram below:

Sauropterygia	Placodontia Hanosaurus Eosauropterygia Pachypleurosauroidea Majiashanosaurus Diandongosaurus Dianmeisaurus Dawazisaurus Panzhousaurus Keichousauridae Dianopachysaurus Keichousaurus Pachypleurosauridae Dactylosaurus Anarosaurus Odoiporosaurus Serpianosaurus Neusticosaurus Prosantosaurus Qianxisaurus Wumengosaurus Luopingosaurus Honghesaurus Eusauropterygia Nothosauroidea Pistosauroidea

Sources

• Benton, M. J. (2004), Vertebrate Paleontology, 3rd ed. Blackwell Science Ltd
• Carroll, R.L. (1988), Vertebrate Paleontology and Evolution, WH Freeman & Co.
• Rieppel, O., (2000), Sauropterygia I, placodontia, pachypleurosauria, nothosauroidea, pistosauroidea: In: Handbuch der Palaoherpetologie, part 12A, 134pp. Verlag Dr. Friedrich Pfeil Table of contents

External links

• Lepidosauromorpha: Pachypleurosauridae - Palaeos