Ericiolacerta is an extinct genus of small therocephalian therapsids from the early Triassic of South Africa and Antarctica. Ericiolacerta, meaning "hedgehog lizard" (from the Latin ericius, "hedgehon" and lacerta, "lizard"), was named by D.M.S. Watson in 1931. The species E. parva is known from the holotype specimen which consists of a nearly complete skeleton found in the Lystrosaurus Assemblage Zone within the Katberg Formation of the Beaufort Group in South Africa, and from a partial jaw found in the Lower Triassic Fremouw Formation in Antarctica. Ericiolacerta was around in length, with long limbs and relatively small teeth. It probably ate insects and other small invertebrates. The therocephalians – therapsids with mammal-like heads – were abundant in Permian times, but only a few made it into the Triassic. Ericiolacerta was one of those. It is possible that they gave rise to the cynodonts, the only therapsid group to survive into post-Triassic times. Cynodonts gave rise to mammals.
Discovery
The Ericiolacerta holotype specimen Ericiolacerta parva was discovered in 1931 in the Katberg Formation of the Beaufort Group near Harrismith, Free State in South Africa and described by Professor David Meredith Seares Watson in an article for the Zoological Society of London. It was discovered by A. W. Putterill within a cornerstone block of limestone from the shales of the Lystrosaurus Assemblage Zone, placing it between ~251-249 Ma during the early Triassic. The specimen consisted of a nearly complete skeleton with a slightly crushed skull. Watson described it as being closely related to the Therocephalian Scaloposaurus based on their skull morphology but as a new member of the family Scaloposauridae founded by Broom in 1914 based on differences in its dentition and jaw structure. This classification was later changed as this family was invalidated and many of its members were moved into the superfamily Baurioidea.
Another specimen was discovered in 1971 in the Lower Triassic Fremouw Formation of the Transantarctic Mountains in Antarctica near the McGregor and Shackleton glaciers and described in 1981 by Edwin H. Colbert and James W. Kitching. They described an associated mandibular ramus and pterygoids, and the hindlimbs of an Ericiolacerta parva specimen based on similarities in jaw structure, dentition, and foot structure to the Watson specimen from Africa. This diagnosis was later revised in Huttenlocker & Sidor (2012), in which the hind limbs were reevaluated as belonging to an indeterminate Eutherocephalian, and the mandibular ramus and pterygoids were confirmed as likely belonging to Ericiolacerta parva. The discovery of this species and others such as Lystrosaurus within both the African Lystrosaurus zone and the Antarctic Fremouw Formation lends more evidence to the fact that these continents were previously congruent as presented in Elliot et al. (1970).
Description
Ericiolacerta parva was described as a small, fossilized reptile preserved extremely well, despite the skull being partially crushed before it was buried, resulting in distortion of the occipital, otic, and mandibular bones, as well as the loss of part of the premaxillae and zygoma. The specimen is also missing twelve vertebrae from its midsection, but besides these the skeleton is completely preserved. The curled position of the skeleton is similar to that assumed by many small mammals when they die, and the displacement of the bones was determined to be as a result of the movement and rotting of still-attached skin. The cause of the fractured skull was attributed to a larger animal likely stepping on the body. The specimen's total length from snout to the hind end of the pelvis was measured to be . It was notable for the small size and irregularity of its teeth, the reduction/lack of canine teeth, the large size of its head and pectoral girdle compared to its relatively small pelvic girdle, and its long, slender limbs. By comparison, the Antarctic mandible from 1981 was described as being from a larger Ericiolacerta parva specimen, but maintained the small tooth size, irregularity, and reduced canines seen in the dentition of the African specimen. Both specimens demonstrate a slender dentary with a smooth, rounded ventral margin, which was determined by Huttenlocker & Sidor (2012) to be a compelling apomorphy in diagnosing the species. The presence of a tuber calcis on the posterior side of the calcaneum in the specimen was revised as a poor character in assigning Ericiolacerta parva and was used to reevaluate the hindlimbs of the Antarctic specimen as belonging to an indeterminate Eutherocephalian.