Western Interior Seaway
The Western Interior Seaway was home to early birds also, including the flightless Hesperornis which had stout legs for swimming through water and small wing-like appendages used for marine steering rather than flight; and the tern-like Ichthyornis, an early avian with a toothy beak. Icthyornis shared the sky with large pterosaurs such as Nyctosaurus and Pteranodon. Pteranodon fossils are very common and it was likely a major component of the surface ecosystem, though it was only found in the southern reaches of the Seaway.