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This 220-million-year-old fossil offers evidence that
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This 220-million-year-old fossil offers evidence that dinosaurs were not ancestral

May 28, 2010
This 220-million-year-old fossil offers evidence that dinosaurs were not ancestral to birds.

More about this Image An archosaur called Longisquama insignis, a small reptile roughly the size of a mouse, has ignited scientific controversy due to the six vane-like appendages attached to either side of Longisquama's back. Longisquama's lived about 220 million years ago in Asia, during the late Triassic era. Some researchers believe the appendages were non-avian feathers and that early archosaurs were the ancestors of modern birds. Longisquama is controversial because it's not a dinosaur and most paleontologists believe that birds evolved from dinosaurs.

In 1999, a team of scientists who studied the fossil found arresting parallels between the appendages and feathers, most notably, a hollow shaft with a sheath characteristic of modern feathers. Some scientists believe this shows that the genetic and developmental potential to produce feathers was present in these early archosaurs. The team also reached the conclusion that the feathers weren't used for thermoregulation but likely allowed the creature to glide between trees.

However, many scientists believe that features as specialized as feathers had only one path of evolution so if feathers evolved from Longisquama's, which occupies one branch of the archosaur family (a subclass of reptiles), they are unlikely also to have evolved in another archosaur, like theropods. Paleontologists who do believe that birds evolved from theropod dinosaurs cite skeletal similarities to back up their claim.


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