Casea

Extinct genus of synapsids

Casea is a genus of herbivorous caseid synapsids that lived during the late Lower Permian (Kungurian) in what is now Texas, United States. The genus is only represented by its type species, Casea broilii, named by Samuel Wendell Williston in 1910. The species is represented by a skull associated with a skeleton (the holotype FMNH UC 656), a second skull (FMNH UC 698), a partial skull with a better preserved dentition than that of the preceding skulls (FMNH UC 1011), and several incomplete postcranial skeletons. Three other Casea species were later erected, but these are considered today to be invalid or belonging to different genera. Casea was a small animal with a length of about 1.20 m and a weight of around 20 kg.

The genus name and specific epithet honor paleontologists Ermine C. Case and Ferdinand Broili. The palate is broad and plate like. A narrow interpterygoid vacuity divides the posterior portions of the palate at the midline. The fossil pocket was about 3 m long, 1.8 m wide, and 60 cm thick. The location and faunal composition of the Cacops bone bed indicate the existence of a distinct fauna that lived in a geographical area far from the floodplains and deltas of coastal regions, where lived the well known fauna from the more classical Lower Permian localities of North America. The Casea specimens were in association with very numerous specimens of the armoured and entirely terrestrial amphibian Cacops (more than 50 individuals are listed including ten skulls, hence the name of the bone bed), a dozen skeletons of the Varanopidae Varanops, and fragments of Seymouria and Captorhinus. Many of the bones were covered with a very thin layer of cemented clay; others were more or less cemented together in nodular masses. Most of the skeletons were lying on their belly, but some were found on their backs. On most of the skeletons the limbs were articulated. In others, the phalanges of the feet were more or less dispersed, and the tail or the entire limbs were disarticulated. In 1974, Denise Sigoneau Russell and Donald E. Russell established the species Casea rutena for a specimen from southern France. These three species are known from the following material :

Casea nicholsi is represented by two specimens from the upper part of the Vale Formation in Knox County. The holotype (FMNH UR 86) consists of a partial basicranium and lower jaw (mainly preserved as a natural cast), a large part of the vertebral column (except the tail), part of the pelvis, elements of the forelimbs, and part of the foot. The only referred specimen (FMNH UR 85) was found in direct association with the holotype and, like it, consists of a partial skull, a large part of the vertebral column without the tail, part of the shoulder bones, the pelvis, a femur, and a fibula end.

In the first phylogenetic analysis of Caseidae published in 2008, Casea broilii occupies a basal position within the caseidae, but is however more derived than Oromycter. Below the phylogenetic analysis of Caseasauria published by Benson in 2012. Among vertebrates this feeding strategy can be subdivided into many categories, including folivory, frugivory, and granivory but among early terrestrial vertebrates, it is feeding on leaves, stems, roots and rhizomes. Herbivores use massive crushing dentition on the palate and mandibles.

The locomotion of Casea involves a three vertebra sacrum in early synapsids and no apparent link to body size. LeBlanc and Reisz argue that this sacral anatomy was related to more efficient terrestrial locomotion than to increased weight bearing. Selective pressures for weight bearing or more efficient locomotory styles and increasingly terrestrial lifestyles may have promoted the repeated acquisition of three sacral vertebrae in Synapsida. The development of the third sacral rib attachment to the pelvis in Synapsids may support this hypothesis.