Alligators sprawled at the elbow much less than Professor Lull’s Centrosaurus, and yet the horned dinosaur was supposed to be a much more advanced evolutionary design than the ‘gator. Some thing was deeply wrong here. Why would an advanced dinosaur exhibit a more sprawled posture than its more primitive relative?(dinosaur factory) I needed evidence from the shoulder-bone structure which I could use to evaluate dinosaur forequarters. Two pieces of evidence came immediately to hand: First, the shoulder socket’s shape.(life size dinosaur)An elephant or rhino’s shoulder socket is shaped like an oval saucer. It is a hollowed-out joint surface, elongated fore to aft, which faces downward and backward to fit over the top of the upper arm bone. But lizards and crocs, whose elbows sprawl, have a saddle-shaped shoulder joint, concave from bottom to top and convex from the inside out. (animatronic dinosaur costume)This saddle-shaped notch lets the upper arm swing out and back and twist around like an axle, a complicated set of movements required by the sprawling and semi-erect gaits. Now, what kind of shoulders did dinosaurs have?
I spent a year digging into museum drawers, and covering myself with dust while I diagrammed the shoulder sockets of the Dinosauria. Almost all had rhino-type joints. (life like dinosaur)When properly mounted, dinosaur shoulder joints were concave sockets facing downward and backward. Markings on the bones showed clearly that the joint didn’t curve around to face sideways as it did in ‘gators or lizards. Professor Lull’s Centrosaurus had a misaligned front end, as did the mounts of most other horned dinosaurs.