The Flight of the Pterosaur

You only have to glance at the spec sheet to see that there's a huge difference between a 50-pound eagle and a 500-pound Pteranodon. Now, Michael B. Habib of the Johns Hopkins School of Medicine has confirmed what everyone kinda, sorta knew already but never quite nailed down: ancient pterosaurs took off using much different flight mechanics than modern birds.

Specifically, Habib's new study shows, pterosaurs used their muscular front limbs to propel themselves off the ground, whereas birds launch themselves into the air with a quick thrust of their hind legs. He points out an excellent, if often overlooked, piece of evidence for this conclusion: "If a creature takes off like a bird, it should only be able to get as big as the biggest bird."

In other words, the lack of Quetzalcoatlus-sized eagles proves that pterosaurs and birds don't share much in common, beside their avian environment. It makes more sense to look at the resemblance between modern birds and ancient dino-birds, which were built along the same evolutionary lines (and are the birds' distant ancestors).