Palaeopleurosaurus

Palaeopleurosaurus is an extinct genus of diapsid reptiles belonging to the group Sphenodontia.[1]

Fossil
Model

Palaeopleurosaurus
Temporal range: Toarcian, 183 Ma
↓
Fossil specimen
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Rhynchocephalia
Family: †Pleurosauridae
Genus: †Palaeopleurosaurus
Carroll, 1985
Species:
†P. posidoniae
Binomial name
†Palaeopleurosaurus posidoniae
Carroll, 1985

Palaeopleurosaurus fossils were discovered in Bavaria, Germany from Toarcian (Early Jurassic) deposits,[2] dated to about 183 million years ago.[3] Palaeopleurosaurus evidences that there was an slightly skeletal specialization for an aquatic lifestyle, achieved trougth the Jurassic gradually on pleurosaurs, a lifestyle supported by increased bone density in its gastralia.[4] It has similities with other marine reptiles, such with members of Sauropterygia the presence of a defined suture between the centrum and the neural arch, along with reducted sternum.[5] However, the lack of increase in rib and femur bone density suggests that the lineage of Palaeopleurosaurus became gradually adapted to aquatic lifestyles, not as adapted as Pleurosaurus, as show limited morphological evidence of adaptation to a complete aquatic lifestyle, defined by no Osteosclerosis and the lack of Pachyostosis, except for a thicker shaft region in the humerus, that is as narrow as in terrestrial rhynchocephalians, such as the terrestrial Clevosaurus.[5] Palaeopleurosaurus probably was still able to walk on land, for example for Oviposition.[5] Recent studies suggest a shorter lifespan than modern Tuatara, based on irregular spacing of growth marks.[1] Histology shows that the number of growth rings in Palaeopleurosaurus was smaller than the living tuatara, possibly indicating a shorter lifespan.[4]

References
  1. Dupret, V. (2004). The pleurosaurs: anatomy and phylogeny. Revue de Paléobiologie, 9: 61-80.
  2. R. L. Carroll, R. L. (1985). A pleurosaur from the Lower Jurassic and the taxonomic position of the Sphenodontida. Palaeontographica Abteilung A, 1985. Volume 189. Pages 1-28.
  3. Paleobiology Database. Retrieved 10 June 2012.
  4. Klein, N.; Scheyer, T.M. (2017). "Microanatomy and life history in Palaeopleurosaurus (Rhynchocephalia: Pleurosauridae) from the Early Jurassic of Germany". The Science of Nature. 104 (4): 4. doi:10.1007/s00114-016-1427-3. PMID 28005148.
  5. Carroll RL, Wild R (1994) Marine members of the Sphenodontia. In: Fraser N, Sues H-D (eds) In the shadow of the dinosaurs—early Mesozoic tetrapods. Cambridge University Press, Cambridge, pp. 70–83


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