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Re: Muttaburrasaurus vs Altirhinus



Alessandro Marisa wrote

>There are two Iguanodontia: Altirhinus from Mongolia and Muttaburrasaurus
>from Australia.
>These Iguanodontia lived approximatively in the same time, but it differs
>from all other Iguanodontia in the possession of a large snout and a nasal
>bulla.
>A similar characteristic may be evolved independantly for two time in
>everyone of this Iguanodontia, or this characteristic evolved one time and
>consequently this animals migrating from an emisphere to another?

While Altirhinus is an iguanodontid (the holotype was for a long time
referred to as Iguanodon mongoliensis), Mutt. appears to be a much more
basal/primitive ornithopod which may not even be iguanodontian. Molnar
suggests that Mutt. diverged from the ornithopod lineage leading to
iguanodontids/duckbills before the divergence of dryosaurids/Tenontosaurus.
Thus Mutt. and Atlirhinus are not closely related and the nasal bulla
developed independantly in these two dinosaurs.

>And can the nasal bulla constitute an adaptation for the habits for
>potentiated the olfactory sense?
>
Possibly, or perhaps they used them as resonating chambers for making a
loud racket.

Cheerio
Brian Choo