Ruling Reptiles

Definition: Reptiles with a highly modified diapsid skull, single copulatory organ in males and a longitudinal cloacal opening. All archosaurian species are egg laying animals. The heart is four-chambered or three chambered with a nearly complete ventral septum. Nest building and parental care of young is common among many species. Includes the crocodiles, turtles (tentative), and dinosaurs, including the birds. 

The term "ruling reptiles" refers to the dinosaurs, supposed rulers of the Mesozoic Era. In paleontological circles, dinosaurs are often referred to as "non-avian dinosaurs."