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Re: Tyrannosaur Evolution



Jaime Headden wrote:

There have been notes and records of material attributed to *Nodosaurus* from Alabama and New Jersey, and form what is apparently a "refugial" condition in the east comparable to the older Cretaceous fauna in the west. This includes nodosaurs, "primitive" hadrosaurs, etc., also not forgetting *Lophorrhothon,* the *Hadrosaurus* synonym(?) *Ornithotarsus,*

Overall, I agree with you: East Coast dinosaurs do appear to be more generalized than their western kin. However, _Lophorhothon_ is a rather contentious taxon. The material comes from a small individual, and the pyramid-like crest is weakly developed. But _Lophorhothon_ is based on juvenile hadrosaur material, and may even be a young _Prosaurolophus_. Thus, any report that _Lophorhothon_ is small-bodied or "primitive" hadrosaur must take into account the immature nature of the type material.


The rest of the hadrosaur material from the East Coast is rather fragmentary and/or lacks good skull material (such as the _Hadrosaurus foulkii_ holotype). This makes an assessment of the phylogenetic position of these hadrosaur specimens very difficult. Some researchers even consider _Hadrosaurus_ to be a nomen dubium.

The East had
huge Campanian hadrosaurs in any case, like Hypsibema crassicauda.

I haven't seen any length estimates for _Hypsibema_, but it is nonetheless huge. For a long time, _Hypsibema_ was even thought to be a sauropod.



Tim