Maiasaur nest model; photo by Drow – GFDL,

A shallow, warm sea reflects sunlight in the distance. Here on the shore, a flat beach is backed by low hills. The hillsides are home to dozens of large, circular depressions approximately six feet across. These are nests, and the assemblage is a rookery.

Some nests still contain eggs, others have young in residence. The nestlings have been here a while, hanging out with the their parents, who in turn provide both food and protection.Protection is essential. The young lack the ability to defend themselves, and there are very nasty predators—sharp teeth, rapier claws, and an efficient, warm-blooded metabolism—looking for a meal of succulent young flesh. The parents, themselves having fast reflexes and effective armament, are a match for the attackers, but still, only some of the young reach adulthood.

We’re not sure, but there’s a reasonable chance that all these creatures were decorated with feathers. Along with insulation against chilly nights, the feathers might provide camouflage, or attract a mate.

Why don’t we know about the feathers? These warm-blooded, egg-laying, family-conscious critters lived about a hundred million years ago, during the Cretaceous period. I’m not describing birds, or at least not the birds we know and love. These were dinosaurs. Specifically, they were Maiasaurs, a type of hadrosaur (aka duck-billed dinosaur).

When I went through my “dinosaur phase” as a five- to seven-year-old, dinosaurs were assumed to be ponderous, stupid creatures much like underdeveloped, bloated lizards. I read how their brains were the size of walnuts, and how, being cold-blooded, they were only able to function effectively at mid-day even in the tropics.

We’ve learned a lot about dinosaurs in the last half-century. Rather than resembling reptiles, paleontologists now believe that dinosaurs have more in common with birds.

For instance, reptiles are cold-blooded, but researchers have concluded that dinosaurs were warm-blooded—able to maintain a stable, raised body temperature no matter the weather. Thus, they were more energetic, able to move quickly either as the hunter or the escaping prey.

The rookery described above was discovered in 1978 in Montana by paleontologist Jack Horner and his fossil-hunting friend Bob Makela. The discovery established that some dinosaurs, at least, were social animals who built nests and cared for their young. (Since then, similar sites have been found in other places around the world.)

The Montana site contains dozens of nests. Over 300 eggs have been uncovered, plus intact fossils of animals ranging in age from the newly hatched to adult. One nest still held eleven baby Maiasaurs. Others held older nestlings, with marks on their teeth that implied plenty of chewing. Since they were still in the nest, someone must have been bringing them food. Think about it—social behavior implies some intelligence, and those well-fed nestlings implies solicitous parents. Not too many reptiles fit this description.

And what about those nasty predators? Again, they’re dinosaurs. Fast, sneaky, nest-plundering dinosaurs.

T-Rex - Jurrasic Park movieCurious, I dug deeper. I read up on the infamous Tyrannosaurus rex. We imagine T. rex as a fearsome killer, roaring defiance, then disemboweling its prey with razor-sharp, 9-inch teeth. We may need to update our mental image. Current thinking is that T. rex—ever the opportunist—was more often a scavenger, dining on the leftovers of more efficient predators. However, the discovery of a T. rex tooth embedded in the tail of fleeing, herbivorous species tells us that if the prey presented itself, T. rex was happy to oblige.

But wait—did you know that T. rex had air spaces in its bones? Birds have these spaces, but reptiles do not. In both cases, they’re used to help the animals breath, allowing them to gather oxygen while both inhaling and exhaling. They’re also lighter—an obvious advantage in flying birds, but also in huge dinosaurs.

Finally, imagine a T. rex running. Yes, the legs attach at the pelvis in the same way as in birds, not the flattened stance of reptiles. The posture of a moving T. rex looks more like that of an ostrich than a giant lizard.


chicken runPerhaps we’re thinking about this all wrong. Instead of picturing a dinosaur as a reptile but with a stable body temperature, social mores, parental care, hollow bones, and downward-pointing legs, it might be better to picture a bird with teeth. You know, kind of like the hens in Chicken Run.

That’s enough for now. It’s time for me to quit and make dinner. We’re having dinosaur breasts cacciatore.

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