Re: dinosaurs coronoids

["David Marjanovic" <david.marjanovic@gmx.at>]

 

I have read on Osteology of the reptiles of Alfred S.Romer that some dinosaurs have two coronoids in the mandible, this seems to me a fact in contrast to all the other amniotes (except synapsids).

If some dinosaurs (protoceratops? sauropoda?) have a second coronoid, have they inherited it from ancient amphibians as the synapsids or is a secondarily developped

character?

AFAIK having 2 coronoids (coronoids II and III = intercoronoid and coronoid) is the plesiomorphy for amniotes, so dinosaurs have simply inherited this. The coronoid II is sometimes called supradentary in dinosaurs. Dromaeosaurus has both, birds, oviraptorosaurs and others have lost number II. However, AFAIK not much is published on these bones, apparently they have been of little interest so far.