| Oedaleops | |
|---|---|
 | |
| Restoration ofOedaleops campi | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Synapsida |
| Clade: | †Caseasauria |
| Family: | †Eothyrididae |
| Genus: | †Oedaleops Langston, 1965 |
| Type species | |
| †Oedaleops campi Langston, 1965 | |
Oedaleops is an extinct genus ofcaseasaursynapsids from theEarly Permian of theSouthwestern United States. Fossils have been found in theCutler Formation inNew Mexico, which dates back to the Wolfcampian stage of the Early Permian. All remains belong to the single known speciesOedaleops campi.Oedaleops was closely related toEothyris, and both are part of the familyEothyrididae. LikeEothyris, it was probably aninsectivore.
Oedaleops was first described by paleontologistWann Langston Jr. in 1965 on the basis of a mostly complete skull (specimenUCMP 35758, theholotype ofOedaleops) and a few isolated skull and postcranial fragments. The UCMP 35758 skull has been the sole specimen ofOedaleops used in most analyses of its evolutionary relationships. The more fragmentary specimens have been assigned toOedaleops with caution because they are hard to distinguish from the bones of other Cutler Formation synapsids such asAerosaurus. Additional specimens ofOedaleops were described in 2013, including many isolateddentaries (lower jaw bones),pectoral and limb bones, anddisarticulated vertebrae representing at least three new individuals.[1]
Oedaleops has a wide and low skull with a convex margin when viewed from the side. It has largeorbits or eye sockets and numerous teeth, the most of any caseasaur. It differs from its closest relative,Eothyris, in having afrontal bone that forms a greater portion of the upper margin of the orbit. Another distinguishing feature ofOedaleops is the thinness of the postorbital bar, a strut of bone separating the back of the orbit from a hole in the back of the skull called thetemporal fenestra.Oedaleops lacks the enlargedcaniniform teeth and blunt snout ofEothyris.[2]
Because no tail bones are known, the total body length ofOedaleops is uncertain. The length of the dorsal vertebral column (the length of vertebrae making up the back) can be estimated at around 20 centimetres (7.9 in) from the lengths of individualdorsal vertebrae inOedaleops and the number of dorsal vertebrae present in related synapsids. Adding the length of the skull gives a snout-vent length (the length of the body from the tip of the skull to hips) of 25 centimetres (9.8 in). Like other early synapsids,Oedaleops probably had sprawling limbs and a body set low to the ground. The front of the body may have been slightly elevated above the level of the hips.[1]
Since its naming in 1965,Oedaleops has been interpreted as a close relative ofEothyris from the Early Permian of Texas. Langston placed both in the familyEothyrididae. Since 1980, mostphylogenetic analyses place eothyridids in aclade or evolutionary grouping calledCaseasauria, which also includes a family of mostly herbivorous Early Permian synapsids calledCaseidae.[2] The majority of analyses place Caseasauria as thebasal-most clade within Synapsida. With caseids and eothyridids are equally closely related to thelast common ancestor of synapsids, the body plan ofOedaleops and other eothyridids (characterized by large heads and relatively narrow bodies) more closely approximates what is predicted for the synapsid common ancestor than does the body plan of caseids (characterized by extremely small heads and barrel-shaped bodies). Therefore,Oedaleops is one of the most important taxa in phylogenetic analyses and the features of its skeleton have an important bearing on the relationships of other synapsids. Below is acladogram from the phylogenetic analysis of Sumidaet al. (2013) that shows many of the same relationships as those found in previous analyses, except for havingEothyris being more closely related to caseids than toOedaleops (making Eothyrididaeparaphyletic):[1]
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