STL Science Center

STL Science Center

02 August 2014

Running At Dawn

©Nobu Tamura
Eodromaeus has a typical looking dinosaur body plan. It diverges from what would become the body plan of theropods in a number of small ways including the number of digits present on both hands and feet. The primitive trait of 4 to 5 digits on hands and feet is exemplified in this primitive dinosaur, one of those traits that clearly allies this animal with the base of the theropod tree. This is not an animal at the base of the dinosaur tree, there are animals on lower brnches that are even more primitive including Herrerasaurus and other basal saurischians as well as the basal-most ornithischians. Like its cousins, the family Coelophysidae, and other theropods as well, Eodromaeus possessed a long counterbalancing tail that allowed it to maintain its balance while running on two legs. We know that most basal members of dinosaur clades started their evolutionary paths as bipedal animals, and theropods were no exception as their earliest forms, such as Eodromaeus prove. Theropods were fairly unique, of course, in that they as a group remained bipedal throughout their evolutionary line (arguments have been made to the contrary before).

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