Lemurosaurus

Lemurosaurus is a genus of extinct biarmosuchian therapsids from the Late Permian of South Africa. The generic epithet Lemursaurus is a mix of Latin, lemures “Ghosts, sprits”, and Greek, sauros, “lizard”. Lemurosaurus is easily identifiable by its prominent eye crests, and large eyes. The name Lemurosaurus pricei was coined by paleontologist Robert Broom in 1949, based on a single small crushed skull, measured at approximately 86 millimeters in length, found on the Dorsfontein farm in Graff-Reinet. To date, only two skulls of the Lemurosaurus have been discovered, so body size is unknown. The second larger, more intact, skull was found in 1974 by a team from the National Museum in Bloemfontein. The holotype skull was poorly preserved and referred to as BP/1/816. Lemurosaurus pricei was coined by Robert Broom in 1949 who was convinced it was a Gorgonopsian. Since 1949 it was presumed that Lemurosaurus was most closely related to Ictidorhinus martinsi. Then in 1970 this classification expanded when Rusell Sigogneu classified more genera within Ictidorhinidae and place them within Gorgonopsia. In 1989 Sigogneau restructured Ictidorhinds into four family-level taxa. These four were Biarmosuchidae, Hipposauridae, Ictidorhinidae, and Burnetiidae. Many of these classifications required further research, and some were incorrect altogether. In 1974, a second skull known as NMQR 1702 was extracted on the farm Petersburg in South Africa, 50 kilometers southeast of the type locality. The specimen was left unprepared until 2000, when it was discovered to be a second Lemurosaurus skull. Present knowledge points to Lemurosaurus being a part of Burnetiamorpha. Both specimens have flaws that make it difficult to make definitive conclusions as to some aspects of structure. On the BP/1/816 skull the postorbital and occipital regions of the left lateral side are missing, and on the right lateral side they are poorly preserved. The entire skull is crushed and warped, adding some ambiguity to measurements. The posterior part of the jaw is also severely damaged, and it is weathered enough that sutures cannot be distinguished. NMQR 1702 is also quite weathered on its external surface, and the different skull matrices are tough to differentiate. The left posterolateral corner of the skull is warped, resulting in missing features like a portion of the zygomatic arch, the occipital condyle, and the paraoccipital process of the opisthotic. A full skeleton has yet to be located, leaving many questions about Lemurosaurus’ full size and structure. Lemurosaurus’ most distinctive feature is its triangular supraorbital bosses. They are tall, stretching up on either side toward the pineal foramen. On the postfrontal there is a pachyostosed supraorbital boss, which has a stronger arch than that of BP/1/816. The upper canines are oval when you look at a cross-section. The premaxillary dentition in NMQR 1702 is not fully intact, but there are four upper incisors. There are strong indications that there could have been five, but one was lost through weathering or poor preservation. The lower canine rests in the anterior section of the choana, much like gorgonopsians, therocephalians, and burnetiamorphs. In the third and fourth positions there are two complete incisors on the right side. A 7.7 millimeter precanine diastema is located behind the upper incisor on that same right side. This seems large, but when compared to incisors of dinocephalians and anomodonts, they are relatively small. Serration is present in NMQR 1702 but it is faint compared to the intense serration of BP/1/816. It is speculated that these differences in serration between NMQR 1702 and BP/1/816 might be ontogenetic, for it is common for juvenile therapsids to lose serration as they get older. There are also high ridges on the dorsal margins of the orbit, and a small midline crest anterior to the pineal foreman. The lacrimal is large, with two fossae where it contacts the maxilla that are not well defined. This structure is not like anything seen in basal therapsids, but it is present in other burnetiamorphs. The squamosal is poorly defined, but deformation of the zygomatic arch suggests the squamosal extends nearly to the posterior end of the maxilla. Also on the squamosal are two small knobs along the ventral margin. These knobs are now considered indicative of burnetiamorphs.