Diving Birds of the Dinosaur Era

When in the depth of the winter, a full hundred miles from the nearest land, one sees a loon in the path of the steamer, listens to its weird, maniacal laughter, and sees it slowly sink downward through the green waters, it truly seems a hint of the bird-life of long-past ages. – William Beebe, The Bird: Its Form and Function, 1906.

In 1872, Yale paleontologist Othniel Charles Marsh described a very peculiar bird. The fossil avian, found in the Cretaceous strata of Kansas, looked like a loon with a mouth full of sharp teeth. He called his find Hesperornis regalis.

The bird was more than a bizarre creature from an ancient era. The fact that Hesperornis had teeth testified to the remote origin of avians. The celebrated English naturalist Thomas Henry Huxley, quite taken with the bird after being introduced to it by Marsh during a 1876 tour of America, pointed out that Hesperornis diminished the anatomical “hiatus” between archaic birds and the dinosaur-like creatures Huxley hypothesized were the avian rootstock. Teeth were an ancient, reptilian feature, and so Hesperornis was a skeletal mosaic of old and new traits. And while Huxley was insistent that the direct line of descent between reptile and bird had not yet been found, creatures such as Hesperornis, the archaic bird Archaeopteryx, and the dinosaur Compsognathus illustrated that the transformation between reptile and bird was possible.

In time, though, Hesperornis fell out of the evolutionary spotlight. The aquatic bird, which chased after fish in a shallow sea which cleft North America in two during the Late Cretaceous, was far too specialized to be of much help in determining the finer points of avian ancestry.

But Hesperornis remains important to our understanding of avian evolution in another way. We now know that birds are dinosaurs – they just happen to be the only lineage of the diverse and disparate group that survived to the present day. And, as far as we know, the first members of the avian lineage evolved around 150 million years ago. Avian dinosaurs flourished alongside their non-avian counterparts – the evolution and radiation of birds is part of the dinosaurian success story. The bizarre nature of Hesperornis and its close relatives helps put this tale in context. By 80 million years ago, at the latest, birds had radiated into disparate forms, including marine divers with greatly reduced wings. In the video above, part of the Royal Tyrrell Museum’s ongoing paleontology lecture series, Joe Sanchez explores the natural history of Hesperornis and kin – birds which lived and died in a long-lost Cretaceous sea.