Page 142 - The Dinosaur Book and Other Wonders of the Prehistoric World (DK-Smithsonian)

Early birds

Dinosaurs take flight Iberomesornis Hesperornis Patagopteryx

Ichthyornis

Resembling a modern
gull, Ichthyornis was
This flightless bird equipped with teeth that
had powerful legs ideal probably helped it keep
for running across a grip on slippery fish.
the open plains of
Patagonia, Argentina,
where it lived about Traces on one
80 million years ago.
Hongshanornis fossil
suggest that it may have had
a feathery crest on its head.

EVOLUTION OF FEATHERS

Symmetrically Asymmetrically
Between the early Jurassic and the placed barbs placed barbs
Cretaceous, feathers evolved from Central rachis with on rachis on rachis
hollow filaments to the form seen unjoined barbs
in modern birds. Over time, they Hollow,
developed a main shaft, or rachis, with hairlike Tuft of barbs Hongshanornis
increasingly complex branches called feather
barbs that zipped together to form
vanes. Early vaned feathers had a
central rachis, but in later feathers the
rachis is off-center. These asymmetrical
feathers made more efficient wings
and were the key to effective flight. Stage 1 Stage 2 Stage 3 Stage 4 Stage 5

In the Cretaceous Period, about 25 million although it still had substantial wing claws. Like
years after Archaeopteryx made its first other birds of the same period, including the
clumsy flight, the early birdlike dinosaurs sparrow-sized Iberomesornis and the slightly
started giving way to more modern-looking bigger Concornis, it had a big breastbone for
birds like Confuciusornis. This is one of the anchoring flight muscles; it must have been able
140 oldest short-tailed, toothless birds known, to fly well. In time, birds like Hongshanornis

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