Not to be confused with mosasaurs, marine reptiles of the Late Cretaceous.
Mesosaurs
Temporal range: Cisuralian, 299–270.6 Ma
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Mesosaurus
Scientific classification
Domain:
Eukaryota
Kingdom:
Animalia
Phylum:
Chordata
Class:
Reptilia
Clade:
†Parareptilia
Order:
†Mesosauria Seeley, 1892
Family:
†Mesosauridae Baur, 1889
Genera
†Brazilosaurus
†Mesosaurus
†Stereosternum
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]
^ abCite error: The named reference AC&ML10 was invoked but never defined (see the help page).
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^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
^Cite error: The named reference ML&RR95 was invoked but never defined (see the help page).
^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.
^Cite error: The named reference MSP99 was invoked but never defined (see the help page).
^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
Mesosaurs ("middle lizards") were a group of small aquatic reptiles that lived during the early Permian period (Cisuralian), roughly 299 to 270 million...
within Diapsida as the sister group to Neodiapsida. However, this excludes mesosaurs, who were found to be basal among the sauropsids. Below is a cladogram...
reptiles. These include the first reptiles to return to marine ecosystems (mesosaurs), the first bipedal reptiles (bolosaurids such as Eudibamus), the first...
Brazilosaurus is an extinct genus of mesosaur which lived during the early Permian (Artinskian stage) of what is now Brazil. It is known from specimen...
restricted crown group encompassing diapsids and parareptiles (apart from mesosaurs, which he considered to be the most basal branch of sauropsids). Sauropsida...
bolosaurids, some nycteroleterids, some procolophonoids and at least some mesosaurs made it more ambiguous and it's currently uncertain whether the ancestral...
extinct genus of mesosaur marine reptile from the Early Permian of Brazil and also the Great Karoo Basin of South Africa. The taxon mesosaur is a monophyletic...
Following is a list of marine reptiles, reptiles which are adapted to life in marine or brackish environments. The following marine reptiles are species...
Graciela H. (2017-11-02). "A Reassessment of the Taxonomic Position of Mesosaurs, and a Surprising Phylogeny of Early Amniotes". Frontiers in Earth Science...
Jörg (2018). "Commentary: A Reassessment of the Taxonomic Position of Mesosaurs, and a Surprising Phylogeny of Early Amniotes". Frontiers in Earth Science...
are known for their unusual downturned snouts and crushing dentition. Mesosaurs were quite possibly the first fully aquatic reptilian animals and the...
Friedrich von Huene in 1931. Brasileosaurus is not to be confused with the mesosaur Brazilosaurus. Although originally classified as a coelurosaur in the original...
araeoscelidans, mesosaurs, squamates, pleurosaurids, weigeltisaurids, protorosaurs, and trilophosaurs. With the exception of mesosaurs, which only have...
the Triassic. A study on the microanatomy and replacement of teeth in mesosaurs is published by Carlisbino et al. (2024). New information on the anatomy...
the globe, the geographic distribution of some fossils (including the mesosaurs) on various continents, and the jigsaw puzzle shape of the landmasses...
fully adapted animals may take to mating and birthing in water or ice. Mesosaurs were a group of small aquatic reptiles that lived during the early Permian...
retraction of the external nares (unlike other reptilian groups such as mesosaurs, phytosaurs, thalattosaurians, saurosphargids, ichthyosauriforms, sauropterygians...
bolosaurids, some nycteroleterids, some procolophonoids and at least some mesosaurs made it more ambiguous and it is currently uncertain whether the ancestral...
bolosaurids, some nycteroleterids, some procolophonoids and at least some mesosaurs. The presence of temporal openings in the skulls of these taxa makes it...
Jörg (2018). "Commentary: A Reassessment of the Taxonomic Position of Mesosaurs, and a Surprising Phylogeny of Early Amniotes". Frontiers in Earth Science...
correlated formations of Irati and Whitehill, it is known for its abundant mesosaur fossils. It also contains the oldest known Konservat-Lagerstätte in South...
1908. The formation is particularly famous for the occurrences of the mesosaurs Mesosaurus tenuidiens, and Stereosternum tumidum. Other fossils found...
Name Novelty Status Authors Age Unit Location Notes Images Brazilosaurus Gen. et sp. Valid Shikama & Ozaki Artinskian Irati Formation Brazil A mesosaur....
of secondarily marine animals like whales, ichthyosaurs, plesiosaurs, mesosaurs and the Jurassic metriorhynchoids, distant cousins of crocodilians. However...
Olson also included distantly related groups such as protorosaurs and mesosaurs. New specimens have been discovered in the United States state of Oklahoma...
clades, such as Temnospondyli, Synapsida, and Sauropsida. In his work on mesosaurs, Huene indicated that a lower temporal fenestra was present (as in synapsids)...
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