Temporal range: 89–65 million years ago: Upper Cretaceous
|H. regalis skeleton in swimming pose; note feet pointing sideways.|
Anatomy and life style[change | edit source]
Hesperornis was a large bird, reaching up to 1.5 meters (5 feet) in length. It had virtually no wings, and swam with its powerful hind legs.
Hesperornis hunted in the waters of such contemporary shelf seas as the North American Inland Sea, the Turgai Strait and the prehistoric North Sea, which then were subtropical to tropical waters, much warmer than today. They probably fed mainly on fish, maybe also crustaceans, cephalopods and mollusks, as do the diving seabirds of today. Their teeth were helpful in dealing with slippery or hard-shelled prey.
On land, Hesperornis species may or may not have been able to walk. They certainly could not stand upright like penguins as in the early reconstructions. Their legs attached far at the back and sideways, with even the lower leg being tightly attached to the body (see photo of skeleton). Thus, they were limited to a clumsy hobble at best on land and would have been more nimble if they moved by sliding on their belly or galumphing. The leg skeleton of Hesperornis was so thoroughly adapted to diving that their mode on land, and their egg-laying and parental care, is a matter of speculation.
Young Hesperornis grew fairly quickly and continuously to adulthood, as is the case in modern birds. More young birds are known from the fossil record of the more northerly sites than from those further south. This suggests that at least some species were migratory like today's penguins, which swim polewards in the summer.
References[change | edit source]
- Discussed in detail by Marsh (1880) and Gregory (1952).
- Rees, Jan & Lindgren, Johan 2005. Aquatic birds from the Upper Cretaceous (Lower Campanian) of Sweden and the biology and distribution of hesperornithiforms. Palaeontology 48(6): 1321–1329. doi:10.1111/j.1475-4983.2005.00507.x (HTML abstract)
- Hills L.V.; Nicholls E.L.; Núñez-Betelu L. "Koldo" M. & McIntyre D.J. 1999. Hesperornis (Aves) from Ellesmere Island and palynological correlation of known Canadian localities. Canadian Journal of Earth Sciences 36(9): 1583-1588. HTML abstract
- Chinsamy A, Martin, Larry D. & Dobson, P. (1998): Bone microstructure of the diving Hesperornis and the volant Ichthyornis from the Niobrara Chalk of western Kansas. Cretaceous Research 19(2): 225-235. doi:10.1006/cres.1997.0102 (HTML abstract)