Allosauroidea is a superfamily or
clade of
theropod dinosaurs which contains four
families — the
Metriacanthosauridae,
Allosauridae,
Carcharodontosauridae, and
Neovenatoridae. The oldest-known allosauroid,
Shidaisaurus jinae, appeared in the early
Middle Jurassic (probably
Bajocian stage) of
China. The last known definitive surviving members of the group died out around 93 million years ago in Asia (
Shaochilong) and South America (
Mapusaurus), though the
megaraptorans, including the late-surviving
Orkoraptor of the
Late Cretaceous (
Maastrichtian stage), may belong to the group as well. Additional, but highly fragmentary, remains probably belonging to
carcharodontosaurids have been found from the
Campanian-Maastrichtian boundary (70 Ma ago) in
Brazil. Allosauroids had long, narrow skulls, large orbits, three-fingered hands, and usually had "horns" or ornamental crests on their heads. The most famous and best understood allosauroid is the
North American genus Allosaurus.