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DINOSAUR BEAKS



On the presence of beaks, Jaime wrote...

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No rostral element in a marginocephalian, thyreophoran,
iguanodontian, basal ornithopod, or basal ornithischian is 
covered in foramina, but rather are ridged or midlly pitted in 
SOME cases, but for the most part are smooth with ridges 
and channels relating to vascularization. 
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... and ...

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In beaked ornithischians, the impressions of a beaked 
premaxilla in opposition to a beaked predentary (the 
predentary DOES have foramina,on the posterior/dorsal [or 
internal] surface and the only ennervation the bone would 
bear and not external) is affirmed in a lateral surface with a
rugose, ridged and pitted surface, where the rostral 1/4 tip 
(or more) was toothless and, as shown in *Agilisaurus 
louderbacki* and *Hypsilophodon foxi*, was not toothed 
and STILL lacked foramina.
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Don't understand what you're saying Jaime, but if you're 
saying that ornithischians lack external/lateral foramina on 
the rostral part of the dentary, predentary etc you're 
incorrect. I'm looking right now at a dentary and predentary 
of an _Iguanodon_ and there certainly are external/lateral 
foramina.

There are other osteological correlates for the presence of 
rhamphothecae (including rugose bone texture on the 
palate, inset channels for blood vessels, striated bone 
texture, and vertical pillars on the lingual sides of the 
maxilla and premaxilla) but >>>none<<< of them are 
consistently present in all extant taxa that possess beaks. 
Accordingly working out which fossil taxa possessed beaks 
is often very difficult or impossible IMHO. Personally I feel 
all ornithischians and all maniraptorans possessed beaks.

-- 
Darren Naish
School of Earth & Environmental Sciences
University of Portsmouth UK, PO1 3QL

email: darren.naish@port.ac.uk
tel: 023 92846045