Dissorophus
Dissorophus (DI-soh-ROH-fus) (meaning "double roof" for two layers of armor) is an extinct genus of temnospondyl amphibian that lived during the Early Permian Period about 273 million years ago. Its fossils have been found in Texas[1] and in Oklahoma[2] in North America. Its heavy armor and robust build indicate Dissorophus was active on land, similar to other members of the clade Dissorophidae that are known from the Late Carboniferous to the Early Permian periods. Dissorphusis distinguished by its small body size, disproportionately large head and short trunk.
The American paleontologist Edward Drinker Cope first briefly described Dissorophus in 1895,[3] likely deriving the genus name from Ancient Greek δισσός/dissos "double" and ὀροφή/orophe "roof" to refer to the double layer of armor formed by horizontal "spinous branches" at the top of the neural spines of the vertebrae that "touch each other, forming a carapace" with overlying rows of bony osteoderms that form an armored "dermal layer of transverse bands which correspond to the skeletal carapace beneath," a feature expressed as well in the type species name multicinctus, meaning "many-banded" in Latin. Cope referred to the animal as "a veritable batrachian [amphibian] armadillo."
DeMar[5] mentions Boulenger's interpretation of Dissorophus as “remarkable for an extraordinary exo- and endo-skeletal carapace",[4] reflected in the name Dissorphus multicinctus for its double layered armor.[5]
Additional specimens of Dissorophus were later collected by the Museum of Comparative Zoology at Harvard College and the University of Chicago, described by the paleontologists Williston, Case and Romer. Williston (1914) divided the Dissorophidae into two subfamilies: Aspodosaurinae and Dissorophinae. He distinguished the Aspodosaurinae as having an open otic notch and single layered armor (one armor segment per vertebral segment), and Dissorophinae as having a closed otic notch and double layered armor (two armor segments per vertebral segment).[4]
Below is a cladogram from Schoch (2010). Schoch developed his cladogram based on an analysis of anatomical features of dissorophids. He found that Dissorophus, Broiliellus texensis, Broiliellus brevis and Broiliellus olson all share a pointed snout as a common feature.[6]
Modern amphibians are semi-aquatic. According to DeMar, Dissorophus multicinctus had made a full transition on terrestrial land, indicated by the presence of a dermal armor that made it less dependent on water and better adapted to active life on land.[1]
