|The spotted, or "laughing" hyena|
Hyenas are familiar African predators that are best known for scavenging, although they don’t actually scavenge most of their food. There are four living hyenas: the spotted or laughing hyena (Crocuta crocuta), brown hyena (Parahyaena brunnea), striped hyena (Hyaena hyaena), and aardwolf (Proteles cristatus). The striped hyena is also found in the Middle East and India. In general, hyenas are fairly large, dog-like animals with lengthy forelimbs and sloped backs (rather like a German Shepherd) and powerful, bone-cracking dentition. The aardwolf is the black sheep of the family, being much smaller than its cousins and subsists almost entirely on termites—apparently they won’t voluntarily eat meat.
|The small, adorable aardwolf|
|Pachycrocuta, by Mauricio Anton|
Surprisingly, however, hyenas are actually on the cat family tree. They’re not cats per say, but if you think of dogs and cats as “end-points” on a diverging family tree, hyenas are around mid-tier on the cat branch. This relationship is given away by the morphology of their auditory bullae, or ear capsules. If you look at the bottom of a dog or cat skull, you’ll see two inflated areas down by the foramen magnum; this is where the ear bones live. In caniforms (dog branch), they have single-chambered bullae. Feliforms (cat branch) have double-chambered bullae, and it turns out that hyenas have double-chambered bullae.
|You can see how the auditory bullae are divided in two here, from Wikipedia.|
But dolphins are clearly mammals, ichthyosaurs are clearly reptiles, sharks are clearly cartilaginous fish, and tuna are clearly ray-finned fish. They all solved the ecological challenges in different ways before coming, more or less, to the same conclusion.
This has gotten a little longer than I anticipated, but the point is that hyenas are not dogs; they're almost cats, and convergent evolution is super neat.