Eothyrididae is an extinct family of very primitive,

insectivorous A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores were ...

synapsid Synapsids + (, 'arch') > () "having a fused arch"; synonymous with ''theropsids'' (Greek, "beast-face") are one of the two major groups of animals that evolved from basal amniotes, the other being the sauropsids, the group that includes reptil ...

s. Only three genera are known, ''

Eothyris ''Eothyris'' is a genus of extinct synapsid in the family Eothyrididae from the early Permian. It was a carnivorous insectivorous animal, closely related to '' Oedaleops''. Only the skull of ''Eothyris'', first described in 1937, is known. It ...

'', ''

Vaughnictis ''Vaughnictis'' is an extinct genus of synapsid from the Early Permian of Colorado in the family Eothyrididae. It is known from a partial skull, hindlimb, and a few ribs. It is closely related to ''Eothyris ''Eothyris'' is a genus of extinct sy ...

'' and ''

Oedaleops ''Oedaleops'' is an extinct genus of caseasaur synapsids from the Early Permian of the southwestern United States. Fossils have been found in the Cutler Formation in New Mexico, which dates back to the Wolfcampian stage of the Early Permian. All ...

'', all from the early

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz ...

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. Their main distinguishing feature is the large

caniniform In mammalian oral anatomy, the canine teeth, also called cuspids, dog teeth, or (in the context of the upper jaw) fangs, eye teeth, vampire teeth, or vampire fangs, are the relatively long, pointed teeth. They can appear more flattened howeve ...

tooth in front of the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

. Eothyridids share with the

Caseidae Caseidae are an extinct family of basal synapsids that lived from the Late Carboniferous to Middle Permian between about 300 and 265 million years ago. Fossils of these animals come from the south-central part of the United States (Texas, Oklaho ...

a number of specialised features associated with the morphology of the snout and external naris and it is likely that their common ancestor was close in build to ''Eothyris''. The two together form the clade

Caseasauria Caseasauria is one of the two main clades of early synapsids, the other being the Eupelycosauria. Caseasaurs are currently known only from the Late Carboniferous and the Permian, and include two superficially different families, the small inse ...

. ''Eothyris'' is known from a single skull specimen; ''Oedaleops'' is known from three partial skulls and some parts of some limbs. ''Vaughnictis'' is known from a partial skull, six dorsal vertebrae and some hind-limb bones. The skulls are approximately six centimeters in length, suggesting that the total length of the animals was under one meter. The species were found in the lower

in what is today

. In modern cladistics, the Eothyrididae are considered to be a basal group within the Caseasauria. Caseasauria forms a sister group of the

Eupelycosauria Eupelycosauria is a large clade of animals characterized by the unique shape of their skull, encompassing all mammals and their closest extinct relatives. They first appeared 308million years ago during the Early Pennsylvanian epoch, with the fo ...

, out of which the

therapsids Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented mor ...

evolved.

References

* Carroll, R. L. (1988), ''Vertebrate Paleontology and Evolution'', WH Freeman & Co. * Reisz, R. R., 1986, ''Handbuch der Paläoherpetologie – Encyclopedia of Paleoherpetology, Part 17A Pelycosauria'' Verlag Dr. Friedrich Pfeil, * Romer, AS & Price L.I (1940), Review of the Pelycosauria. ''Geol. Soc. Amer. Spec. Papers'' 28: 1–538. * Brocklehurst, N., Reisz, R. R., Fernandez, V. & Fröbisch, J. (2016) ''A Re-Description of 'Mycterosaurus' smithae, an Early Permian Eothyridid, and Its Impact on the Phylogeny of Pelycosaurian-Grade Synapsids. ''PlosOne'' 11:e0156810.

External links

Tree of LifeThe Paleobiology Database
{{Taxonbar, from=Q136601 Caseasaurs Prehistoric synapsid families Taxa named by Llewellyn Ivor Price Taxa named by Alfred Romer

See also

References

External links