The fossilized bird known as Archaeopteryx has had quite a history of identity crises. Researchers once classified it as a "missing link" between dinosaurs and birds. It was considered to be an ancient bird, then changed to a dinosaur, and now it's supposed to be a bird again. So, what is it?

In 1993, a fossil of a long-tailed bird was found in China that still contained feathers and bones. The fossilized Confuciusornis sanctus is supposedly 120 million years old, but observation has shown that original organic materials such as bones and feathers break down in just thousands of years, even if bacteria aren't present.

If dinosaurs evolved into birds, then fossils should show plenty of sequential transitional features between the two groups. For example, some evolutionists speculate that the earliest stages of feather evolution consisted of filaments, or "dinofuzz," on dinosaurs' skin.

Sauropods, such as Diplodocus and Apatosaurus, were immense, four-footed dinosaurs. By their fossils, researchers know that their unique skeletal design features were specially equipped to support their bulk.

Archaeopteryx has long been hailed as a "missing link" between birds and dinosaurs. After a recent analysis of a different fossilized creature, however, Chinese researchers concluded that Archaeopteryx was not the first bird to have evolved, but was instead more like a dinosaur. This new categorization aptly illustrates the unreliability of evolutionary tree analyses.