Cynodonts (Dog-Teeth) were a suborder/clade of therapsid amniotes, appearing in the Middle to Late Triassic time period, around 256-250 MYA. Unlike the earlier therapsids, such as the gorgonopsids of the Late Permian, or even some of the therocephalians of the earlier Triassic, non-mammalian cynodonts were generally fairly small animals, not much bigger than modern house cats or medium-sized dogs. Mammals are actually dirived cynodonts.
In the Walking with... Series[]
As illustrated in Walking with Dinosaurs, ep. 1, cynodonts such as Thrinaxodon (identified later in The Complete Guide to Prehistoric Life encyclopedia),
had a mixture of reptilian and mammalian characteristics - they were furry and whiskered, but still hatched their young from eggs, and lacked mammary glands. Modern animals - the platypus and the spiny anteaters (echidnas) still have these physical features, thus identifying these ancient protomammals as our direct ancestors, as opposed to their evolutionary cousins, the Dicynodonts ("two dog-teeth"), also illustrated in that same episode (the cattle-sized Placerias), who were not. It is still hard to identify exactly, when the non-mammalian cynodonts had died-out/became replaced by mammals proper - the fossils of both these groups in the Jurassic time period are quite rare and not preserved too well, but by the end of the Mesozoic, the non-mammalian cynodonts as well as the monotremes (like the Steropodon from ep. 5) were replaced by the marsupial (like the Didelphodon in ep. 6) and first placental mammals, who went-on to dominate the fauna in the Cenozoic.
Thrinaxodon's skeleton (Wiki image).
Known Cynodonts[]
- Thrinaxodon - The most commonly seen and the only identified species in the series.
- An unidentified Cynodont that appeared in the companion book of Sea Monsters (Possibly a synonym for Thrinaxodon).
- Mammals