|
Allosaurus
fragilis
Allosaurus
is one of the best
known therapods of the Mesozoic era because of the sheer amount of fossil
material collected, mainly from the late Jurassic Morrison formation. More than
ten thousand bones of Allosaurus were uncovered at the Cleveland-Lloyd quarry in
central Utah, representing many individuals from different size ranges and age
classes.
It is not known why so many Allosaurs died
together. Perhaps it was some sort of predator trap such as that found at Rancho
La Brea. Packs of Allosaurs may have been drawn to dying sauropods, the
bones of which are found alongside the numerous predator remains at Cleveland
-Lloyd. But the number of saurapod remains was nowhere near that of the Allosaur
remains, which is unusual
given the normal predator to prey ratios for terrestrial vertebrate faunas: the hunters are always less numerous than the hunted.
An active and
powerful predator, adult Allosaurs averaged about 30 feet in length, though they
may have grown throughout their lives provided they were able to
survive well into adulthood at all. Remains of huge Allosaurs such as Epanterias
and Saurophaganax are known from deposits of later
age than the Morrison formation. These could be distinct species or just huge
examples of Allosaurus. But the fossil evidence is incomplete, especially
concerning Saurophaganax, so the taxonomic
affinities are still in question
|