Cynognathus: Facts & Overview

Instructor: Charles Spencer

Charles teaches college courses in geology and environmental science, and holds a Ph.D. in Interdisciplinary Studies (geology and physics).

Cynognathus may hold the record for the sheer number of different genus and species names it has carried since its discovery in the late 19th century - at least nine! But that's not why it is an important fossil. Learn more in this lesson.

Not Quite a Mammal

Sketch by Nobu Tamura, used under Wikimedia Commons license.
Cynognathus sketch

Meet your second cousin, about seven times removed (evolution-wise, that is). Although in the sketch it resembles a cross between a chipmunk and pit bull, it was a reptile.

The genus name Cynognathus (pronounced 'sigh-nog-NAY-thus') means 'dog jaw.' It wasn't a dog, obviously, but it did have a somewhat dog-shaped head and lots of canine-looking teeth. It belonged to the group of mammal-like reptiles called therapsids, and more specifically a sub-group known as cynodonts (meaning 'dog teeth'). Mammals evolved from another cynodont species, so while not a direct ancestor, we are indeed related.

Appearance and Lifestyle

Based on fossils, Cynognathus was about one meter long, with a stocky build. Its legs were positioned beneath its body as it walked, which suggests that it had a mammalian-like gait.

It had a jaw full of teeth that were designed for nipping (incisors), tearing (canines) and chewing (cheek teeth), all of which adds up to a carnivorous diet. And just what did they chomp with all those teeth? Most likely, they preyed on their herbivorous reptile therapsid cousins (who no doubt would want to stay away from family reunions).

Skull of Cynognathus crateronotus. Source: Wikimedia user Diderot. Public domain image.
Cynognathus jaw

It also had a diaphragm, a muscle that enhances lung function and is characteristic of modern mammals. Another mammalian characteristic it probably had: whiskers. Did it have fur? There is no direct fossil evidence, and although many artistic reproductions show it with a nice fur coat, that could be just artistic license.

Home on the Range in Gondwana

Cynognathus evolved in the early Triassic Period (which began 251 million years ago). The animals lived across much of the southern hemisphere landmass known as Gondwana, the southern half of the supercontinent called Pangaea. All of the fossils known are today classified as belonging to a single species, Cynognathus crateronotus, but it is possible that they might represent multiple, but similar species.

During the Triassic period, Pangaea shifted position and the climate across Gondwana changed as the southern part of the supercontinent moved into drier latitudes. As the climate became more arid, the plant species upon which the prey of Cynognathus fed died out, and a (food) chain of events followed. Cynognathus became extinct sometime in the middle Triassic, about 215 million years ago.

Why Is Cynognathus Important?

Cynognathus fossil locations shown in tan. Source: U.S. Geological Survey.
Small Gondwana

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