A key evolutionary innovation of dinosaurs is that they walk with a fully erect posture, holding their hind legs vertically under their hips. What else makes a dinosaur a dinosaur? Learn how scientists define this group of reptiles in the first video from the AMNH.tv series "Dinosaurs Explained."

Ever since the first dinosaur fossil was identified almost 200 years ago, people have wondered how these fascinating animals lived, moved, and behaved. In the video series "Dinosaurs Explained" on AMNH.tv, Museum paleontologists Mark Norell, Michael Novacek, and Lowell Dingus answer the most frequently asked questions about dinosaurs.

Visit AMNH.tv to watch the other videos in the series.

A new species of feathered dinosaur discovered in southern Germany is further changing the perception of how predatory dinosaurs looked. The fossil of Sciurumimus albersdoerferi,which lived about 150 million years ago, provides the first evidence of feathered theropod dinosaurs that are not closely related to birds. The fossil is described in a paper published today in the Proceedings of the National Academy of Sciencesby researchers at the Museum and at the Bayerische Staatssammlung für Paläontologie und Geologie and Ludwig Maximilians University, both in Germany.

In addition to peer-reviewed research papers, Steve Brusatte, a graduate student at Columbia University who is advised by Museum Curator Mark Norell, has already written children’s dinosaur guides and a coffee-table book of dinosaurs and their relatives. Now, he’s added another book to the list.

A new study has used skull anatomy to show that the evolution of birds from dinosaurs may have resulted from a drastic change in dinosaur development.

In a study published this week in the journal Nature, researchers from Harvard University, the Museum, the New York Institute of Technology, The University of Texas at Austin, and the Autonomous University of Madrid report evidence that while many dinosaurs took years to reach sexual maturity, birds sped up the developmental clock, which led them to retain the physical characteristics of baby dinosaurs.