Contents Updated: Tuesday, August 24, 1999
Compsognathus was a small (two feet long) dinosaur about the weight of a hen from the end of the Jurassic, 140 million years ago. It was clearly fast and could catch nimble creatures as its prey. Its hand only had two digits and its forelimbs were short, putting its grasping abilities in doubt, but in the time period up to the end of the Cretaceous its descendants could have well adapted along the required lines.
Ornitholestes lived about the same time as compsognathus but was bigger and had a more powerful head. Its arms were long and it had three digits two of which were long and the other, the thumb, short but opposed. It would have been quite good at grasping and could have diversified into even better forms.
The coelurosaurs were small, lightly built fast running predators. They had small heads with sharp teeth, moderately long necks and long arms with grasping hands. Animals of this type must have been abundant during the 140 million years reign of the dinosaurs but because of their slightly built physiology they decayed and their bones were scavenged quickly so that few specimens have been found. The dromaeosaurids, which seemed to have evolved from coelurosaurs, lived at the end of the Cretaceous.
The ornithomimosaurs had three digit hands, long arms, large brains and opposed thumbs. Oviraptorosaurs which fall into the same category had grasping hands. Saurornithoidids like stenonychosaurus could have hunted the mammals into the night and sharpened their intelligence against that of our distant ancestors. These dinosaurs were thought by Dale Russell capable of evolving intelligence.