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Flying Dinosaurs
People familiar with Pterodactylus (tehr-o-DAK-til-us) and Pteranodon (teh-RAN-o-dahn)
may wonder why they cannot be found in the Dinosaur Bios. The reason is
that pterosaurs (to give them their group name) were not dinosaurs, although
they were related to them; they were flying reptiles.
Archaeopteryx (ar-kee-OP-ter-iks), on the other hand, is considered by
most to be a true flying dinosaur. It has feathers, and only birds have
feathers; therefore, Archaeopteryx is usually considered a bird. (This
argues for the evolution of birds from theropods.) Seven specimens showing
the faint impression of feathers have been found. In one case (the Teyler
specimen) the fossil was mis-identified in 1857, and the error was not
corrected until 1970 when the feathers were first detected. This incident
reaffirms the adage that some of the best discoveries are made in museum
storerooms. Another Archaeopteryx specimen was mis-identified as a Compsognathus
in 1951. When the skeletons of Compsognathus and Archaeopteryx are compared,
it is easy to see how the fossils might be confused and how some conclude
that birds are descended from coelurosaurian dinosaurs.
Archaeopteryx's first toe, pointing backwards, would have permitted it
to grip a branch or perch exactly like a modern bird. However, the lack
of bone structure to support adequate wing muscles suggests that Archaeopteryx
could not fly as well as modern birds. Instead, it may have clambered into
trees and then glided to another tree or to the ground. The claws on its
wings would have been useful for climbing, not unlike the modern day baby
hoatzin from South America, which also has claws on its wings for climbing
in trees.
Sinornis (seh-NOR-niss), a recent find from China, may prove to be a link
between Archaeopteryx and modern birds.
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