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|The tetanurans, the “fused tails”, make up the second clade of theropods. They lack a fang-like tooth in the gap between maxillary and premaxillary bones of the upper jaw that most ceratosaurs had. One tetanuran, Protoceratosaurus bradleyi, possessed a nasal horn (Weishampel, p. 165). The end of the pubis expanded to form a pubic “boot” which anchored large leg muscles. The crested Antarctic dinosaur Cryolophosaurus seems to be a primitive tetanuran but its skeleton includes some features associated with ceratosaurs (Hammer, 1994).|
|Torvosaurus is the most basal tetanuran known whose relatives, such as Yangchuanosaurus, are known from various parts of the world (Lambert, 1990, Fastovsky, 1996).|
|Two interesting theropods,
Baryonx and Spinosaurus are
related to the torvosaurids. The early tetanurans
(such as Torvisaurus and Spinosaurids)
were large while most of the later coelurosaurs
were small to medium sized, although two lineages, therizinosaurids
and tyrannosaurs, evolved to large sizes (Serreno,
Baryonyx, “heavy claws”, resembled a large crocodile. One fossil specimen was found with a partially digested one meter long fish in its abdomen. Baryonyx is unlike most other theropods in its long snout, its long and low nostril, its large hand claw, its large number of teeth, and a longer, straighter neck than most theropods. Its large thumb claws would have been useful in grabbing fish. It may have been capable of both bipedal and quadrupedal locomotion (Charig, 1997). (Charig, 1986).
|Spinosaurus ,“thorn lizard”, possessed a spinal frill, possibly for thermoregulation
or display. It was a fish eating
theropod. Suchomimus, an early spinosaurid, has a
lower sail than Spinosaurus and
has a thumb claw and other features which link it to Baryonx.
One find of Baryonyx included bones of a young iguanodont, indicating that its diet was not limited to fish. A spinosaurid tooth (similar to the spinosaurid Irritator) was found in the neck vertebrae of a pterosaur fossil, indicating that spinosaurids included pterosaurs in their diets (Buffetaut, 2004).
|There are a number of
species of the family Megalosauridae, “great lizards”, known from
|Dryptosaurus is the only known member of a group that may be related to Megalosaurus.|
The Allosauridae, “different lizards”, were
the top predators of the Jurassic. Their
neck had an S-shaped curve and they had small hornlets on their heads.
They were the most common predators of the Late Jurassic.
Perhaps a group of allosaurs could have hunted the large sauropods. The various species of this group are known
from every continent except
was the largest allosaur, reaching 12 meters in length. It possessed short arms. One fossil site in
similar to Allosaurus but was
smaller and lived on the island which is now
| Tyrannosaurus rex was the largest known terrestrial
predator for about 90 years but, in recent years, finds of Gigantosaurus and Carcharodontosaurus have challenged this title. Gigantosaurus
“gigantic lizard” had a skull which measured1.5 meters and its body estimated
12.5 meters making it larger than Tyrannosaurus
(its femur was 2 inches longer than that of the largest known T. rex) and heavier (weighing 8 tons).
Carcharodontosaurus possessed a 62 inch
skull—3 inches longer than that of T.
rex and about the size of Gigantosaurus. Unfortunately, the leg bones are unknown so
that estimating its body size is not possible.
T. rex is known from
The first known member of the family Compsognathidae
was Compsognathus, “pretty jaws”. Measuring 2-3 feet in
length, it was the smallest known dinosaur until the discovery of Microraptor. It lived in the Late Jurassic. One fossil specimen died with a lizard in its
stomach. Compsognathus had only 2 fingers and resembled birds in the structure
of its ribs, shoulders, and wrists (Lambert, 1990, Fastovsky, 1996).
| In 1996, a compsognath named Sinosauropteryx from
The theropod Irenichnites was about the size of a chicken (Russell, 1989).