Theropoda
From Freepedia
| Theropoda Conservation status: Fossil | ||||||||||||
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| Image:TrexFoot.jpg T. rex foot Picture taken at Field Museum of Natural History, Chicago | ||||||||||||
| Scientific classification | ||||||||||||
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Coelophysidae |
Theropods ("beast foot") are a group of bipedal saurischian dinosaurs. Although they were primarily carnivorous, it is believed a number of theropod families evolved herbivory during the Cretaceous. Theropods first appear dduring the Carnian age of the Late Triassic (about 220 million years ago), and were the sole large terrestrial Carnivores from the Early Jurassic until the close of the Cretaceous (65 million years ago). Today they are represented by the 8600 living species of birds, which evolved in the Late Jurassic from small specialised coelurosaur dinosaurs.
Among the features linking theropods to birds are the three-toed foot, a wishbone, air-filled bones, and (in some cases) feathers and brooding of the eggs.
Coelophysoids, including Coelophysis and Dilophosaurus are among the most primitive of theropods; they range from Late Triassic to Early Jurassic in age.
The somewhat more advanced Ceratosauria (including Ceratosaurus and Carnotaurus) appear during the Early Jurassic, and dcontinued through to the Late Jurassic in Lauraisa, and - in the form of the abelisaur lineage - the end of the Cretaceous in Gondwana
The Tetanurae are more specialised again than the Ceratosaurs. They are subdivided into Spinosauroidea or Torvosauroidea (originally called "Megalosaurs") which were most common during the Middle Jurassic but continue to the Middle Cretaceous, and the Avetheropoda. The Latter clade - as their name indicates - are more closely related to birds, and are again divided into the Carnosauria (including Allosaurus) and the Coelurosauria, a very large and diverse dinosaur group that was espexcially common during the Cretaceous.
Some Coelurosaur clades are: tyrannosaurs, including the famous Tyrannosaurus rex, the dromaeosaurs, including Velociraptor and Deinonychus, the superficially similar Troodontidae, the herbivorous ornithomimids ("ostrich dinosaurs"), the omnivorous oviraptorosaurs, and the birds.
