Day #8 on our Christmas Countdown is…

Hesperornis!

Hesperornis: the “Western Bird“

Hesperornis was a large bird from Late Cretaceous North America. It was about the size of the average human (5.9 ft., so taller than me!), and was specialized for life in the water like cormorants and loons today.

This fascinating bird almost has as long a history as some of the most famous dinosaurs, because it was first discovered in 1871 by Othniel Charles Marsh just before the infamous Bone Wars. At a fossil site in Kansas, he found bones of the pterosaur, Pteranodon, and the skeleton of a “large fossil bird, at least five feet in height.” It was almost complete, but had no wings or head.

Fortunately, Marsh’s team discovered a “nearly perfect skeleton” when they returned to the site the following year. This fossil revealed that Hesperornis had a beak full of sharp teeth, and tiny wings.

Marsh considered this find to be incredibly important, because it helped to “break down the old distinction between birds and reptiles.”

The wealth of fossils, and the history surrounding them, has led to the naming of many species, but only the original type species of Hesperornis regalis is well understood. Even then, there are a few questions still up for debate.

For example, it is clear that this bird was very well adapted to life in the water, and obviously it couldn’t fly, but how well did it fare on land? For many years it was thought that it couldn’t walk at all. The shape of the hip and position of its legs are very similar to the common loon today, which is a bird that is so specialized for water that it can’t walk on land. Instead it pushes with its legs and slides along its belly like a seal. But some recent studies suggest that Hesperornis had legs more like a cormorant (another seafaring bird), and though ungainly, was still able to walk upright.

Another question has to do with Hesperornis’ feet. The feet of water birds can vary quite a bit. There are the webbed feet many of us often think of, like ducks, and then there are lobed toes like modern grebes.

Grebes are diving water birds that can float on top of the water like a duck, but their beaks are sharp, and each of their toes has fleshy edges that make them look flat, instead of skin in between the toes like ducks. Traditionally, Hesperornis was thought to have these flat toes like a grebe, but recent studies suggest that webbed or lobed feet are equally likely. So artists can speculate either way.

Personally I find the lobed feet wonderfully prehistoric looking, and so I’ve given my Hesperornis the traditional reconstruction.

Hesperornis had to watch out for competition from other toothed birds like Ichthyornis, flying pterosaurs like Pteranodon and Nyctosaurus, and also predators in the water like the mosasaur Tylosaurus, the plesiosaur Elasmosaurus, and many sharks.

As if it didn’t have enough to worry about, it is possible that a few survived right up until the great asteroid impact. Though in truth there is no direct fossil evidence for this. It is only possible to speculate on this scenario, since the fossil record has many holes.

I would love to hear your imaginings about this fascinating bird. Do you think the evidence seems more convincing that it slid on its belly or that it could walk? Lobed feet or webbed feet? Are there any other creatures from this time and place that you enjoy learning about?

See you tomorrow for day 9 of the Critter Christmas Countdown!