Styracocephalus platyrhynchus(Greek for "spiked-head") is an extinct genus of dinocephalian therapsid that existed during the mid-Permian throughout South Africa, but mainly in the Karoo Basin. It is often referred to by its single known species Styracocephalus platyrhynchus. The Dinocephalia clade consisted of the largest land vertebrates and herbivores during the early to mid-Permian. This period is often also referred to as the Guadalupian epoch, approximately 270 to 260 million years ago.[1][2]
Although multiple Styracocephalus skulls have been recovered, there has yet to be a specimen found of the entire therapsid skeleton. A majority of the skulls collected have also been mature skulls, as the juvenile tapinocephalid skulls are identified by having a small non-fused basioccipital.[3] The presence of enlarged canines, pachyostotic cranial boss, and horns are all plesiomorphic traits found in Dinocephalia.[2] Styracocephalus's head ornament meant that it could be recognised from a distance. One of the most striking feature of Styracocephalus is the large backward-protruding tabular horns.[4] It was around 1.8 metres (5 ft 11 in) in length,[5] with a 42-centimetre-long (17 in), 29-centimetre-wide (11 in) skull.[4]
The first Styracocephalus fossil was discovered by Lieuwe Dirk Boonstra in 1928 from a Tapinocephalus bed on a farm called Boesmans Rivier, in the Beaufort West Division.[1] The original skeleton was crushed, but still showed some unique features such as outward projecting tabular horns, a shallow snout, and a small temporal opening. The skull had a maximum length of around 400 mm and a width of 390 mm.[4] Upon initial discovery, Boonstra compared the newfound specimen to Burnetia stating that the palate was more like that of a gorgonopsian than a therapsid. When Boonstra evaluated its place as a therapsid, it was found to contain characteristics resembling Therocephalia, Gorgonopsia, as well as Dinocephalia.[6] The first classification of Styracocephalus was in 1929 by S. H. Haughton and he placed it in its own new subclade of Therapsida due to its unique blend of features.[1] This original holotype that was found is called SAM 8936.[6]
Although the SAM 8936 holotype was used to identify many characteristics of the skull, more recent specimens such as the SAM K 8071 specimen helped determine the posterior of the skull. The SAM K 8071 specimen was twice the size of the original holotype showing the variety seen in the morphological size of Styracocephalus.[6]