In the late 1960s and early 1970s, paleontologists John H. Ostrom (1928–2005) and Robert T. Bakker (1945–) first suggested that dinosaurs were not sluggish, stupid, cold-blooded animals. Their work paved the way for the theory that many of these animals were actually agile, dynamic, and smart. In 1969, Ostrom published a description of the Deinonychus, a Cretaceous period carnivorous dinosaur. Based on his study of the creature, he theorized that dinosaurs may have been warm-blooded. In 1975, Bakker summarized his ideas about dinosaur endothermy in an article published in Scientific American. This set off a new era in dinosaur paleontology that continues today, especially in advancing ideas on how dinosaurs truly regulated their bodies’ metabolism and heat.