More crest laminations, this time in a pterosaur
When animals develop crests, it’s rarely just one bone that creates it. We just looked at Lambeosaurus, in which the crest is made of two bones, the premaxilla and nasal (no matter how you divide it). Today we’ll look at Tupuxuara, a crested pterosaur of the Early Cretaceous. It’s interesting to compare how crests grow by watching which bones grow to create them.
Figure 1. Juvenile Tupuxuara. Colors denote various bones. Note the expansion of the nasal dorsally as in laminates the premaxilla to strengthen it. The premaxilla, frontal and parietal contribute to the cranial portion of the crest.
Several years ago I was lucky enough to photograph a juvenile Tupuxuara skull at the Tucson Gem and Mineral Show. Not only did it have the proportions of an adult (isometric growth in tritosaur lizards), it more clearly differentiated the various bones used to create it. It was also preserved uncrushed and completely worked out of the matrix.
The crest in Tupuxuara is homologous to that in Germanodactylus cristatus, another sharp-jawed pterosaur with a single tooth at the tip. With skull bones often about one millimeter in thickness it helps to laminate one bone upon another for strength, something like a paper sculpture.
Figure 2. Photo of the Tupuxuara juvenile. Click to enlarge.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
2012-11-09 09:08:57
Source: http://pterosaurheresies.wordpress.com/2012/11/09/more-crest-laminations-this-time-in-a-pterosaur/
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