02 September 2011
Herrerasaurus, at first glance, certainly looks like an early dinosaur; it possesses large flexible claws on its hands, a long reptilian skull filled with conical teeth which clearly mark it as a predatory animal, a long flexible tail which was held horizontal from the body for balance, and even the basal ischian pubis found in later theropods (though much more primitive) which caused the femoral attachment to face directly, or nearly so, vertical and thus without having a bowed effect like we see in modern reptiles but a more mammal-like carriage of gait with the legs swinging in a nearly vertical arc of movement like we see with later theropods and other dinosaurs. Mammal-like isn't exactly the best description for the overall movement, but if you think of your own hip attachment (where I am taking mammal-like from in this instance) then you can imagine the movement of the femoral attachment site of Herrerasaurus. Compare this image if you disagree with my description or are still confused:
There is a lot to discuss this week concerning this animal and, due to this fact, I may alter some of the days such as Sunday to discuss more of how this primitive dinosaur led to the dinosaurs we quickly recognize and love as children and adults.