specimen in question. Combine this with the greater organization of osteocyte lacunae in the periphery of adult T. liorhinus, and we approach the assumption that this creature grew very quickly in order to reach adulthood at an accelerated rate. Before Thrinaxodon, ontogenical patterns such as this had not been seen, establishing the idea that reaching peak size rapidly was an adaptively advantageous trait that had arisen with Thrinaxodon. Within the femur of Thrinaxodon, there is no major region of the bone that is made of parallel-fibred tissues; however, there is a small ring of parallel-fibred bone within the mid-cortex. The remainder of the femur is made of fibro-lamellar tissue; however, the globular osteocyte lacunae become much more organized and the primary osteons assume less vasculature than many other bones as you begin to approach the subperiosteal surface. The femur contains very few bony trabeculae. The humerus differs from the femur in many regards, one of which being that there is a more extensive network of bony trabeculae in the humerus near the meduallary cavity of the bone. The globular osteocyte lacunae become more flattened as you get closer and closer to the midshaft of the humerus. While the vasculature is present, the humerus contains no secondary osteons. The radii and ulnae of Thrinaxodon represent roughly the same histological patterns. In contrast to the humerii and femora, the parallel-fibred region is far more distinct in the distal bones of the forelimb. The medullary cavities are surrounded by multiple layers of very poorly vascularized endosteal lamellar tissue, along with very large cavities near the medullary cavity of the metaphyses. Discovery and naming Thrinaxodon was originally discovered in the Lystrosaurus Assemblage Zone of the Beaufort Group of South Africa. The genoholotype, BMNH R 511, was in 1887 described by Richard Owen as the plesiotype of Galesaurus planiceps. In 1894 it was by Harry Govier Seeley made a separate genus with as type species Thrinaxodon liorhinus. Its generic name was taken from the Ancient Greek for "trident tooth", thrinax and odon. The specific name is Latinised Greek for "smooth-nosed". Thrinaxodon was initially believed to be isolated to that region. Other fossils in South Africa were recovered from the Normandien and Katberg Formations. It had not been until 1977 that additional fossils of Thrinaxodon had been discovered in the Fremouw Formation of Antarctica. Upon its discovery there, numerous experiments were done to confirm whether or