Thrinaxodon

Thrinaxodon is an extinct genus of small cynodonts that lived in southern Africa and Antarctica during the Early Triassic. Its fossils preserve evidence of burrowing and mammal-like anatomy.

Cynodont: Cynodonts are therapsids that include modern mammals and their extinct relatives. Thrinaxodon belongs to this diverse group of mammal-line synapsids.
Thrinaxodon burrow: The Thrinaxodon burrow is a fossilized underground structure associated with a Thrinaxodon skeleton in South Africa. The skeleton’s position within the burrow links the animal directly to underground shelter.
Early Triassic: The Early Triassic is the first epoch of the Triassic Period, spanning roughly 252 to 247 million years ago. Thrinaxodon lived during this interval, soon after the largest known mass extinction.
Karoo Basin: The Karoo Basin is a sedimentary basin in southern Africa with an exceptionally rich record of Permian and Triassic terrestrial life. It is the principal region where Thrinaxodon fossils have been found.
Synapsid jaw evolution: Synapsid jaw evolution is the transformation of the lower jaw and its joints across the lineage leading to mammals. Thrinaxodon preserves an intermediate stage in the evolution of the mammalian jaw apparatus.
Therapsid: Therapsids are synapsids that include mammals and several extinct lineages. This broader group contains the cynodont lineage to which Thrinaxodon belongs.
Diademodon: Diademodon is an extinct herbivorous cynodont from the Early Triassic of southern Africa and Antarctica. Its burrow association with Thrinaxodon records two cynodonts sharing a shelter.
Karoo Supergroup: The Karoo Supergroup is a thick sequence of sedimentary rocks in southern Africa, spanning much of the late Paleozoic and Mesozoic. Karoo deposits preserve many of the southern African fossils assigned to Thrinaxodon.
Antarctic Thrinaxodon fossils: Antarctic Thrinaxodon fossils are Early Triassic remains of the genus recovered from Antarctica. They show that Thrinaxodon’s range extended beyond southern Africa.
Mammalian middle ear: The mammalian middle ear transmits sound through the malleus, incus, and stapes. Thrinaxodon’s jaw anatomy predates the complete separation of middle-ear bones from the lower jaw.

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