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RE: Bakker's Brontosaurus and Late Cretaceous populations

Denver Fowler wrote:

I don't really agree with the oversplitting of alot of the North American taxa (especially ornithischians); it gives a very false idea of dinosaurian diversity. For example, it is extremely difficult (if not impossible) to tell one lambeosaurine from another postcranially, even size- wise there isn't huge variation, yet the likes of Lambeosaurus, Corythosaurus, Parasaurolophus etc are afforded enus-level distinction. Substitute any of the ornithischian subfamilies and the result is similar.
Contrast this with my old buddy Iguanodon, which shows as much variation between the contemporaneous I.bernissartensis and I.atherfieldensis as is seen between the Hadrosaurinae and Lambeosaurinae

Like a lot of things, 'lumping' and 'splitting' are often in the eye of the beholder. Nevertheless there are obvious examples of oversplitting. In recent years there has been a tendency to consolidate. The Morrison sauropods are a good example: _Cathetosaurus_, _Ultrasaurus_, _Supersaurus_, _Seismosaurus_ and maybe _Dystylosaurus_ have either already sunk or are about to be sunk into long-established genera. Against the flow, heroic efforts have been made to reinstate _Brontosaurus_; and I don't know what to make of _Eobrontosaurus_. _Coelophysis_/_Syntarsus_ and _Ornithomimus_/_Dromiceiomius_ are other examples. On the ornithischian side, a case could be made to unite the _Lambeosaurus_-_Corythosaurus_-_Hypacrosaurus_ complex into a single genus, but I don't see this happening.

At the other end of the spectrum, there are genera that look rather 'lumpy', and perhaps (in some cases, definitely) deserve to split up into more than one genus: _Plateosaurus_, _Alamosaurus_, _Iguanodon_, _Probactrosaurus_, _Psittacosaurus_, _Euoplocephalus_, &c. This has already happened with _Chilantaisaurus_, _Dilophosaurus_ and _Titanosaurus_. The process of breaking up European _Plateosaurus_ has already begun: one study spun off _Gresslyosaurus_ as a valid genus, another resurrected _Efraasia_, another erected _Ruehleia_, and more may be on the way. (The process is not entirely one-way: _Sellosaurus_ was sunk into _Plateosaurus_, although as a separate species from the type.) Work is being done to break up others among the aforementioned 'lumpy' genera, and some new names have already been coined - but these have yet to be published.