What's so special about dinosaurs?

Long, long ago--actually, in 2006--I wrote an article for the New York Times about a very strange relative of today's alligators and crocodiles. Effigia, which lived 210 million years ago, did not slouch around inTriassic swamps. Instead, it stood on two big hind legs, holding its front legs--arms, really--aloft. It looked an awful lot like a bipedal dinosaur, despite the fact that the ancestors of dinosaurs and crocodiles split off 250 million years ago. As just one species standing upright, Effigia might have been an evolutionary fluke. But today at Science Now, Brian Switek writes that a contemporary relative of Effigia was a biped, too. So now it appears that there was a lineage of crocodile relatives running around upright at the same time as some dinosaurs were too. The dinosaurs went on to fame and glory--or, at any rate, a continued upright existence. The crocodile lineage ended up on all fours, where they remain today. [Reconstruction by Carl Buell]