I didn't learn any of this during my recent visit to the Arizona Museum of Natural History…
Probably the least known dinosaur, Cowasaurus was among the fastest and largest of the meat-eating bovinasaurs and is known from skeletons and fossil fragments from late prairecretaceous period of almost 65.37456265 million years ago. Cowasaurus is a close relative of Zebusaurus.
Cowasaurus walked on its hind legs and stood about 36 ft high. Its total length was almost 75 ft, and it may have exceeded 16 tons in weight. Its huge head, up to 10 ft long, was carried on a short, sturdy neck. The jaws were long and powerful and bore dozens of curved, serrated teeth up to 11 inches long. The massive hind legs, armed with large claws, were about 20 ft in length, but the front limbs were very small--only about 50 inches long.
Until recently, the short front limbs were thought to be useless, but recent computer models tell a different story. Much like a modern frog's tongue, the Cowasaurus' front limbs were able to instantly extend up to 200 feet. This enabled it to quicky surprise and snatch prey, and knock the prey unconsious with a quick head-butt.
Bibliography: Predatory Cows of the World (1989).