When Gerry Harding captures a "Hypsilophodont" this information is given:
In the harsh quartz lights, the hypsilophodont's green head hung down out of the sling, the tongue dangling, the eyes dull. ... The hypsy was a small dryosaur, seven feet long, weighing about five hundred pounds.
This means that Dryosaurus is the only genus of which we can be sure appeared in the novels.