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|From the basal theropods, two clades of theropods evolved: the ceratosaurs and the tetanurans. Ceratosauria is the smaller of the two clades. In the hips of ceratosaurs depicted below, the hip socket is open (a characteristic of all dinosaurs) and two of hip bones (the pubis and ischium) form long processes for the attachment of leg muscles. In ceratosaurs, the pubic bones lack the prominent pubic boot found in tetanurans. In some ceratosaurs, such as Coelophysis and Syntarsus pictured below, the hipbones fused in adulthood and some fusion of foot and anklebones occured in adults as well. (Weishampel), 1993.|
|Sexual dimorphism has been observed in some species of ceratosaurs. Some individuals (thought to be females) possessed a longer skull and neck and thicker and stronger limbs. Males are thought to have been more slender and many possessed crests on their skulls. Ceratosaurus was unusual in retaining a functional fourth finger. Most ceratosaurs (and theropods in general) reduced the number of functional fingers to three.|
| The species of the family Coelophysidae
lived from the Late Triassic to Early Jurassic. They had a long tail for
maintaining balance. Some had conical teeth adapted for grabbing prey while
others had teeth better adapted for slashing. Some had crests on their skulls.
Coelophysis is named hollow form. From the remains of a juvenile
in the abdominal cavity of an adult, it appears that they could cannibalize
their own young. They seem to have traveled in groups given that hundreds
of individuals died at one site in a sudden New Mexico flood. There were
3 primary digits on the hand and they retained the trace of a fourth. There
may have been a sexual dimorphism with males being larger (Lambert, 1990,
In Syntarsus without tarsus, several parts of the ankle
and foot are fused (the astragalus and calcaneus are fused; the other
tarsal bones are fused to the metatarsals of the foot). Syntarsus rhodensiensis
possessed a long antorbital fenestra that was 40% its skull length. S.
kayentakatai possessed 2 crests on it skull and its fibula was fused to
its calcaneus (Weishampel).
|In Dilophosaurus, the two ridged lizard, the skull possessed 2 fragile bony crests. Dilophosaurus was a large dinosaur and could reach almost 7meters in length. Some researchers have proposed that the crests were so fragile and the teeth were so weak that these dinosaurs could not have been active predators and must have fed on carrion. Most disagree with this. If closely related to coelophysids, Dilophosaurus was the largest member of this group (Lambert, 1990, Fastovsky, 1996).|
|The family Ceratosauridae include the horned lizards. These were large theropods with a lighter skull. They possessed small bony plates along the vertebral column and still retained primitive 4 fingered hands. There was some fusion of the hip and foot bones.|
| The family Abelisauridae includes a group of
Abels lizards, large theropods with fused ankles known
from South America, Africa, and India. They possessed a light lower jaw
with slender teeth, a slim body, and a number of primitive skeletal characteristics.
The theropod families Abelisauridae and Noasauridae are probably related
given that they share a number of features and are both known from the southern
continents (Bonaparte, 1991).
|Carnotaurus, the carnivorous bull, had short horns over its eyes and short arms. The forelimbs of some ceratosaurs, such as those of Ceratosaurus and especially those of Carnotaurus, were reduced (Lambert, 1990, Fastovsky, 1996).|