Thrinaxodon Facts and Figures

Although it wasn't quite as mammal-like as its close cousin, Cynognathus, Thrinaxodon was still a startlingly advanced reptile by early Triassic standards. Paleontologists believe this cynodont (a subgroup of the therapsids, or mammal-like reptiles, which preceded the dinosaurs and eventually evolved into the first true mammals) may have been covered in fur, and also may have possessed a moist, cat-like nose.

• Name: Thrinaxodon (Greek for "trident tooth"); pronounced thrie-NACK-so-don
• Habitat: Woodlands of southern Africa and Antarctica
• Historical Period: Early Triassic (250-245 million years ago)
• Size and Weight: About 20 inches long and a few pounds
• Diet: Meat
• Distinguishing Characteristics: Cat-like profile; quadrupedal posture; possibly fur and warm-blooded metabolism

Completing the resemblance to modern tabbies, it's possible that Thrinaxodon sported whiskers as well, which would have evolved in order to sense prey (and for all we know, this 250-million-year-old vertebrate was equipped with orange and black stripes).

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Cynognathus Facts and Figures

By Bob Strauss

What paleontologists can say for sure is that Thrinaxodon was among the first vertebrates the body of which was divided into "lumbar" and "thoracic" segments (an important anatomical development, evolution-wise), and that it probably breathed with the aid of a diaphragm, yet another feature that didn't come fully into mammalian vogue until tens of millions of years later.

Thrinaxodon Lived in Burrows

We also have solid evidence that Thrinaxodon lived in burrows, which may have enabled this reptile to survive the Permian-Triassic Extinction Event, which wiped out most of the world's terrestrial and marine animals and left the earth a smoking, inhospitable wasteland for the first few million years of the Triassic period.

(Recently, a Thrinaxodon specimen was discovered curled up in its burrow alongside the prehistoric amphibian Broomistega; apparently, this latter creature crawled into the hole to recover from its wounds, and both occupants then drowned in a flash flood.)

For nearly a century, Thrinaxodon was believed to be restricted to early Triassic South Africa, where its fossils have been discovered in abundance, along with those of other mammal-like reptiles (the type specimen was unearthed in 1894).

In 1977, however, a nearly identical therapsid species was discovered in Antarctica, which sheds valuable light on the distribution of the earth's land masses at the start of the Mesozoic Era.

And finally, here's a bit of showbiz trivia for you: Thrinaxodon, or at least a creature closely resembling Thrinaxodon, was featured in the very first episode of the BBC TV series Walking With Dinosaurs.