Mesosaur

Not to be confused with mosasaurs, marine reptiles of the Late Cretaceous.

Mesosaurs
Temporal range: Cisuralian, 299–270.6 Ma
Mesosaurus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: †Parareptilia
Order: †Mesosauria
Seeley, 1892
Family: †Mesosauridae
Baur, 1889
Genera

Mesosaurs ("middle lizards") were a group of small aquatic reptiles that lived during the early Permian period (Cisuralian), roughly 299 to 270 million years ago. Mesosaurs were the first known aquatic reptiles, having apparently returned to an aquatic lifestyle from more terrestrial ancestors. It is uncertain which and how many terrestrial traits these ancestors displayed; recent research cannot establish with confidence if the first amniotes were fully terrestrial, or only amphibious.[1] Most authors consider mesosaurs to have been aquatic,[1][2] although adult animals may have been amphibious, rather than completely aquatic, as indicated by their moderate skeletal adaptations to a semiaquatic lifestyle.[3][4] Similarly, their affinities are uncertain; they may have been among the most basal sauropsids[5][6] or among the most basal parareptiles (in the case of which parareptiles were basal sauropsids).[7][8]

  1. ^ a b Cite error: The named reference AC&ML10 was invoked but never defined (see the help page).
  2. ^ Cite error: The named reference SM06 was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference GP08 was invoked but never defined (see the help page).
  4. ^ Pablo Nuñez Demarco et al. Was Mesosaurus a Fully Aquatic Reptile? Front. Ecol. Evol, published online July 27, 2018; doi: 10.3389/fevo.2018.00109
  5. ^ Cite error: The named reference ML&RR95 was invoked but never defined (see the help page).
  6. ^ Laurin, Michel; Piñeiro, Graciela H. (2017). "A Reassessment of the Taxonomic Position of Mesosaurs, and a Surprising Phylogeny of Early Amniotes". Frontiers in Earth Science. 5: 88. Bibcode:2017FrEaS...5...88L. doi:10.3389/feart.2017.00088. hdl:20.500.12008/33548.
  7. ^ Cite error: The named reference MSP99 was invoked but never defined (see the help page).
  8. ^ MacDougall, M.J.; Modesto, S.P.; Brocklehurst,N.; Verriere, A.; Reisz, R.R.; Fröbisch, J. (2018). "Response: A Reassessment of the Taxonomic Position of Mesosaurs, and a Surprising Phylogeny of Early Amniotes". Front. Earth Sci. 6:99 doi: 10.3389/feart.2018.00099