Mammalian Pronation

Behold the cynodont.

(Sounds like: sign-uh-daunt.)

Cynodonts gave rise to all living mammals about 250 million years ago.

Or so.

These are pre-mammalian forms. To evolve from reptiles to mammals, there was a transition from supination to pronation—as Jon Zahourek demonstrates so clearly in this video from 1987.

From reptile to mammals. Via cynodonts.

All mammals stand on pronated hands/forearms—allowing a different form of propulsion.

And it’s all thanks to the supinator muscle.

One more thing about that word cynodont.

It’s derived from Ancient Greek:

‘Cyno’ from kúōn: dog.

And ‘odont’ from kúōn: tooth.

Dogtooth.

Why? Because cynodonts (who were carnivores) were known from their specialized teeth.

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