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Re: YAVERLANDIA




Joe Parish wrote:

Have you got any further information regarding the identity of Yaverlandia bitholus?

Maryañska (1990) stated that "Hopson (1979) doubted the relationship of Y. bitholus with other pachycephalosaurs because of the structure of its fragmentary endocranial activity. Although these differences in the endocranial cast are significant, it is also true that Y. bitholus shares with other pachycephalosauridae two characters not found in any other ornithischians: the thickening and doming of the skull roof and the textured nature of its dorsal surface" (pp.574-575).


I believe these two characters are also found in _Majungatholus_, an abelisaur. From memory, "thickening and doming of the skull roof" is also seen among the Indian abelisaur material.


The possibility of _Yaverlandia_ being an ankylosaur was raised in a popular dinosaur book by David Lambert (can't remember which one, but published some time in 1990's). He's also repeated this possibility elsewhere in person:
http://www.cmnh.org/fun/dinosaur-archive/1996May/0307.html


The exact reason (maybe based on one of Steven Hutt's new Isle of Wight discoveries) remains elusive. It's worth remembering though that _Yaverlandia_ remains the only known pachycephalosaur from outside North America and Asia. All other non-Asiamerican putative pachycephalosaurs (try saying THAT ten times quickly :-) ) have been re-assigned (_Majungatholus_, _Taveirosaurus_), although I think the jury's still out on _Stenopelix_ (pachy, ceratopsian, or basal marginocephalian?).

As for the domes from the Maleri Formation of India... This is one of the earliest dinosaur-bearing horizons anywhere in the world. Pachys from the Carnian...? Hmmm. These I have to see.

Are there any ankylosaurians with skull roof thickening and texturing?

Almost all of them, I would guess. Whether it would lead one to be mistaken for a pachycephalosaur is another matter. It would be interesting to look into (especially the Wealden ankylosaurs).



Tim



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