''Oedaleops'' is an extinct genus of caseasaur

synapsid Synapsida is a diverse group of tetrapod vertebrates that includes all mammals and their extinct relatives. It is one of the two major clades of the group Amniota, the other being the more diverse group Sauropsida (which includes all extant rept ...

s from the

Early Permian 01 or 01 may refer to: * The year 2001, or any year ending with 01 * The month of January * 1 (number) Music * '01 (Richard Müller album), ''01'' (Richard Müller album), 2001 * 01 (Urban Zakapa album), ''01'' (Urban Zakapa album), 2011 * ''01011 ...

of the

Southwestern United States The Southwestern United States, also known as the American Southwest or simply the Southwest, is a geographic and cultural list of regions of the United States, region of the United States that includes Arizona and New Mexico, along with adjacen ...

. Fossils have been found in the

Cutler Formation The Cutler Formation or Cutler Group is a stratigraphic unit exposed across the U.S. states of Arizona, northwest New Mexico, southeast Utah and southwest Colorado. It was laid down in the Early Permian during the Wolfcampian epoch. Desc ...

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

, which dates back to the Wolfcampian stage of the Early Permian. All remains belong to the single known species ''Oedaleops campi''. ''Oedaleops'' was closely related to '' Eothyris'', and both are part of the family

Eothyrididae Eothyrididae is an extinct family of very primitive, insectivorous synapsids. Only three genera are known, '' Eothyris'', '' Vaughnictis'' and '' Oedaleops'', all from the early Permian of North America. Their main distinguishing feature is the l ...

. Like ''Eothyris'', it was probably an

insectivore file:Common brown robberfly with prey.jpg, A Asilidae, robber fly eating a hoverfly An insectivore is a carnivore, carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the Entomophagy ...

Discovery

''Oedaleops'' was first described by paleontologist Wann Langston Jr. in 1965 on the basis of a mostly complete skull (specimen

UCMP The University of California Museum of Paleontology (UCMP) is a paleontology museum located on the campus of the University of California, Berkeley. The museum is within the Valley Life Sciences Building (VLSB), designed by George W. Kelham a ...

35758, the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

of ''Oedaleops'') and a few isolated skull and postcranial fragments. The UCMP 35758 skull has been the sole specimen of ''Oedaleops'' used in most analyses of its evolutionary relationships. The more fragmentary specimens have been assigned to ''Oedaleops'' with caution because they are hard to distinguish from the bones of other Cutler Formation synapsids such as '' Aerosaurus''. Additional specimens of ''Oedaleops'' were described in 2013, including many isolated dentaries (lower jaw bones),

pectoral Pectoral may refer to: * The chest region and anything relating to it. * Pectoral cross, a cross worn on the chest * a decorative, usually jeweled version of a gorget * Pectoral (Ancient Egypt), a type of jewelry worn in ancient Egypt * Pectora ...

and limb bones, and disarticulated vertebrae representing at least three new individuals.

Description

''Oedaleops'' has a wide and low skull with a convex margin when viewed from the side. It has large

orbits In celestial mechanics, an orbit (also known as orbital revolution) is the curved trajectory of an physical body, object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an satellite, artificia ...

or eye sockets and numerous teeth, the most of any caseasaur. It differs from its closest relative, ''Eothyris'', in having a

frontal bone In the human skull, the frontal bone or sincipital bone is an unpaired bone which consists of two portions.'' Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bo ...

that forms a greater portion of the upper margin of the orbit. Another distinguishing feature of ''Oedaleops'' 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 the

temporal fenestra Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit (eye socket). These openings have historically been used to track the evolution and affinities of reptiles. Temporal fenestrae are commonly (al ...

. ''Oedaleops'' lacks the enlarged

caniniform In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, eye teeth, vampire teeth, or fangs, are the relatively long, pointed tooth, teeth. In the context of the upper jaw, they are also known as ''fangs''. They can appear mo ...

teeth and blunt snout of ''Eothyris''. Because no tail bones are known, the total body length of ''Oedaleops'' is uncertain. The length of the dorsal vertebral column (the length of vertebrae making up the back) can be estimated at around from the lengths of individual

dorsal vertebra In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae of intermediate size between the cervical and lumbar ve ...

e in ''Oedaleops'' 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 . 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.

Relationships

Since its naming in 1965, ''Oedaleops'' has been interpreted as a close relative of ''Eothyris'' from the Early Permian of Texas. Langston placed both in the family

. Since 1980, most

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

analyses place eothyridids in a

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

or evolutionary grouping called

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 insect ...

, which also includes a family of mostly herbivorous Early Permian synapsids called

Caseidae Caseidae are an Extinction, extinct Family (biology), family of Basal (phylogenetics), 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 so ...

. The majority of analyses place Caseasauria as the basal-most clade within Synapsida. With caseids and eothyridids are equally closely related to the

last common ancestor A most recent common ancestor (MRCA), also known as a last common ancestor (LCA), is the most recent individual from which all organisms of a set are inferred to have descended. The most recent common ancestor of a higher taxon is generally assu ...

of synapsids, the body plan of ''Oedaleops'' 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 a

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

from the phylogenetic analysis of Sumida ''et al.'' (2013) that shows many of the same relationships as those found in previous analyses, except for having ''Eothyris'' being more closely related to caseids than to ''Oedaleops'' (making Eothyrididae

paraphyletic Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

References

* Langston, W. 1965. ''Oedaleops campi'' (Reptilia: Pelycosauria), a new genus and species from the Lower Permian of New Mexico, and the family Eothyrididae. ''Bull. Texas Mem. Mus.'' 9: 1–47.

External links

www.palaeos.com
(picture of a skullcast) {{Taxonbar, from=Q3282065 Eothyrididae Prehistoric synapsid genera Cisuralian synapsids of North America Fossil taxa described in 1965 Cisuralian genus first appearances Cisuralian genus extinctions