Ichthyornis
With its feathered body, powerful wings and keeled breastbone,
Ichthyornis, ("fish bird") must have looked and acted like a plump
tern. The mouth was armed with backwardly curved teeth which did
not reach the front of the upper jaws; the lower jaws had extra
joints which allowed them to open widely like the jaws of mosasaurs, with which they have sometimes been confused.
Though the
various species of Ichthyornis stood only 6 to 9 inches high, they
were apparently able to swallow thick-bodied fish.
Hesperornis
Very little is known about Cretaceous birds, for their remains are
fragmentary and rare. Hesperornis ("western bird") had very large
feet, diminutive wings and a flat unkeeled sternum, thus
indicating that it could not fly. Its legs were turned backward so
far they could only be used for swimming. The articulation of the
lower jaw was similar to that of the mosasaur, including sharp
teeth.
Hesperornis
had no need for wings or walking legs as long as it stayed in the
water. There it lived like an oversized, flightless loon, skimming
over the surface, diving, and swimming long distances while
submerged. It could easily capture small fish while dodging
carnivorous reptiles that might have fed upon it Hesperornis
probably nested on isolated islands or it is possible that it gave
birth to live young and never ventured onto dry land.
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