Thrinaxodon is a genus of cynodont that lived during the early part of the Triassic period (248-245 million years ago) in what is now South Africa and Antarcitca. Because it is closely related to the lineage leading to mammals, Thrinaxodon is often considered a transitional fossil.
The two known species ranged in size from 30 to 50 cm (12 to 20 in) in length. Pits on the skull suggest that Thrinaxodon may have had whiskers, but whether it also had fur is debated. In response to the wide daily temperature swings of the early Triassic, it may have been eurythermic, able to function at a broad range of temperatures; this could have laid the groundwork for the development of homeothermicendothermy. Like its predecessors, Thrinaxodon laid eggs, and there were many reptilian features in its skeleton…
Identified from fossils in South Africa and Antarctica, this archaic proto-mammal emerged on a reptile-ruled Earth some 245 million years ago.
Why it matters: An almost perfect intermediate between mammals and reptiles, Thrinaxodon has played a key role in unveiling the evolution of mammals. Descended from a reptile group called cynodonts, Thrinaxodon was a cat-size burrower that had scales and laid eggs. But, like mammals, it had whiskers, warm blood, and, scientist suspect, a fur coat.
“Thrinaxodon shows mammal-like features beginning to kick in,” said paleontologist Paul Barrett of the Natural History Museum in London. “The origin of mammals is exceptionally well understood, and there is a whole series of fossils forming a nice transformation series that shows how mammals evolved a bit at a time.”
… a genus of cynodonttherapsid that lived during the Triassic Period (248-245 million years ago) notable for being a transitional fossil.The two known species ranged in size from that of a small badger (50 cm) to ermine-sized (30 cm long).Pits on the skull suggest that Thrinaxodon may have had whiskers, but whether it also had fur is debated, though it likely had a near-mammalian warm-blooded metabolism. Even so, Thrinaxodon still laid eggs, and there were many reptilian features in its skeleton.
Its remains were found on South Africa and Antarctica, supporting the notion that the two continents were once joined together. Its name was taken from Greek θρῖναξ “trident, three-pronged fork” and ὀδούϛ ὀδόντ- “tooth” in reference to it’s cheek teeth, but with a Greek language error: “Thrinacodon” would have been the grammatically correct form…