This type of saurischian dinosaur walked on bird-like hind limbs, and
they were exclusively meat-eating forms, such as _Allosaurus_ (Pl. 44)
of Jurassic age. Some theropods were exceptionally large and were
undoubtedly vicious beasts of prey. This assumption is borne out by such
anatomical features as the small front limbs with long sharp claws for
holding and tearing flesh, and the large strong jaws which were armed
with numerous, sharp, dagger-like teeth. The largest of all known
theropods was _Tyrannosaurus rex_ which, when standing on his hind
limbs, was almost 20 feet tall. Some individuals were as much as 50 feet
long, and _Tyrannosaurus_ is believed to have been among the most
vicious animals to ever inhabit our earth. A cast of the skull of one of
these great beasts is on display in the Texas Memorial Museum at Austin,
and a _Tyrannosaurus_ tooth has been found in the Big Bend National Park
in Trans-Pecos Texas.