Dinosaur Diversity conundrum

[deanm]

What is the current state of the argument?

Were dinosaurs (in terms of species & diversity) on the decline in the late Cretaceous?

I don't happen to have the references handy but there seems to be two different schools of thought on this subject.

The first group maintains that dinosaur diversity was declining towards the end of the Cret. based upon the fossil record.

The second group argues that dinosaur diversity was increasing overall and that the fossil record is poor for the tail end of the Cret. plus there was a turnover in the actual major groups.


DeanM

[thagomizer]

Seems to me that it was decreasing, but I don't have any cites. Just look at the number of different dinosaur species present in the Dinosaur Park formation en.wikipedia.org/wiki/Dinosaur_Park_Formation a few million years before the extinction, to the number in the en.wikipedia.org/wiki/Hell_Creek_Formation Hell Creek formation just before the big finale.

Specifically look at the herbivores. 6 hadrosaurs in the DP formation compared to just 1 in Hell Creek! (The Hell Creek Parasaurolophus listed on the wiki page is extremely dubious and probably represents another Edmontosaurus and Anatotitan is also becoming generally accepted as a synonym).