Hummingbirds wear a public image of fragile, ethereal beauty: tiny jewels whirring through the air, occasionally pausing to drink daintily from a flower. Their unusual appearance supports this: the iridescent feathers, the long dainty bill, the near-invisible feet all make them seem quite apart from the everyday world of animals who don’t shimmer in the sun and do have feet.

But hummingbirds, like all birds, evolved from dinosaurs. Hidden under that glimmering exterior is a tiny, fierce raptorial dinosaur.

Hummingbirds do a good job of not looking like raptors. (Raptor is an unfortunately vague word. In this post I’m going to use it in the sense of running-adapted carnivorous dinosaur, such as a velociraptor, not in its other sense of bird of prey.) While raptors had long necks and strong legs for running, hummingbirds have no neck and barely any legs.

But this—you might want to sit down—is a lie. Hummingbirds have necks and legs! They only reveal this when they think no one is looking:

There’s that hidden neck.

The legs are more difficult to see, but you can infer their existence from the strange places that the feet turn up when a hummingbird gets itchy.

Can you scratch the top of your head with your foot?

This all makes more sense when you look under the feathers to the skeleton of the hummingbird. You can still see that raptor ancestor in the hummingbird’s bones: the legs are hidden, but they’re there, and the neck is indeed long, just folded up most of the time.

The long muscular tail of a raptor is mostly gone, but there are still a few vertebrae to show where it was. The spine, a flexible line of vertebrae in a raptor, has fused to form a rigid structure against which the flight muscles can pull. The breastbone has become huge so that those flight muscles can attach to it. The arm bones, already rather small in many raptors, are smaller still, just an attachment point for the many wing feathers.

That beak is not a raptor’s tooth-filled jaw by any definition, though. Birds replaced teeth with bills because bills are much lighter: very important if you want to fly.

I don’t think raptors had tongues as long as hummingbirds’ either.

And then there are the feathers… maybe. We’re increasingly suspecting that many, maybe all dinosaurs had feathers well before they became what we would call birds. So the feathers may be something hummingbirds have in common with their “terrible lizard” ancestors. And if raptors had feathers, might they have folded and hidden their necks in those feathers the same way hummingbirds do now? Might they have displayed to each other with colorful feathers, as hummingbirds do?

Raptors might have looked a lot more like hummingbirds than we used to think. After all, we’ve been guessing at their appearance based on their fossilized skeletons. We can see from the hummingbird’s example that the skeleton doesn’t necessarily match the external appearance of an animal.

Certainly hummingbirds still have a ferocious dinosaur heart beating under their breastbone. That bill isn’t dainty—it’s a sword.

*Photos obtained from Flickr and used via Creative Commons. Many thanks to these photographers for using Creative Commons!