My son and I just spent the afternoon watching the charming Your Inner Fish series (his idea, not mine), and learned all kinds of fascinating things about the importance of jaws. They’re where our ears come from. Well, our sensitive, mammalian ears.
And that transformation started with critters like these – therapsids, mammal-like reptiles.
These four fellows here are from H.R. Barghusen’s “Notes on the Adductor Jaw Musculature of Venkujovia, Anomodont Therapsid, Permian, USSR”. From top left, they are a Dimetrodon, a “hypothetical condition”, a Venjukova and a Lystrosaurus.