hypsilophodonts

["Nicholas R. Longrich" <longrich@phoenix.Princeton.EDU>]

        Drinker and Othnielia are not really just another couple of
hypsilophodonts. For one, they have halluxes. For another, reversible
ankles. That means they can climb trees, supposedly. For another, the jaws are 
very differen 
very different. The beak is very narrow in the front- which bakker claims
means that they pulled leaves in from the sides. For another, they lack the 
diastema- the gap between the nipping and chewing functions/surfaces in the 
jaws- a horse has nipping teeth up front, a gap in the jaw, and then the big 
grinder i
nders in the back. In a duckbill or ceratopsian, this is obvious: beak up
front, teeth in backj. Othnielia et al don't have this. What's more, the teeth
themselves are quite unique- the little cusps on the edge tmhemselves bear cusps
which is pretty unusual- something like what multituberculate mammals had
however. So between having arboreal adaptations, and unique teeth running to the
predentary, these guys are not just your average hypsilophodonts. Bakker claims 
they aren't hypsilophodonts at all.