[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
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.