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Showing posts from October, 2007

Ontogeny and taxonomy of pachycephalosaurs

There were two interesting talks on pachycephalosaurs at the SVP annual meeting in Austin, Texas. I don’t know if they were coincidental but both talks dealt with the possible synonymy of Dracorex, Stygimoloch and Pachycephalosaurus.

The first talk was by John Horner. Horner (2007) used comparative cranial morphology, computer tomography and osteohistology to hypothesize that Dracorex, Stygimoloch and Pachycephalosaurus all represent different stages in an ontogenetic series of a single taxon Pachycephalosaurus.

Aside from having a flat head, Dracorex differs from Stygimoloch and Pachycephalosaurus in having large supratemporal fenestrae. Dracorex also has extensive ornamentation along the squamosals. Stygimoloch has closed off its supratemporal fenestrae and have a well-developed frontoparietal dome incorporating the rostral part of the frontal and postorbital but not the lateral and caudal elements of the skull. Stygimoloch also has extensive cranial ornamentations along the squamosal…

Deinonychus antirrhopus

I painted an older sketch of Deinonychus antirrhopus using Photoshop. I must admit, I'm no where near a computer artist but I had quite a bit of fun with Photoshop. I didn't know you can do so much with it...

Anyway, the all-too-famous Deinonychus antirrhopus. One of my favourite dinosaurs thus far. I didn't draw flight feathers on this guy mostly because of the simpler integuments of Sinornithosaurus but its quite obviously outdated now that we know one of its closest relative Velociraptor was found to have quill knobs on its ulna. These are little bumps on the surface of the bone and are typically associated with flight feathers in modern birds.

Wood-eating behaviour in hadrosaurs

I came across a really interesting article yesterday about some hadrosaur coprolites from the Upper Cretaceous Two Medicine Formation that contained woody materials (Chin 2007). This is direct evidence that at least some hadrosaurs ate wood. Coprolites at this locality regularly contain wood indicating that conifer wood was regularly ingested. Wood contains lignin which cannot be digested by vertebrate herbivores so there is no nutritional value on its own. Thus, in order for any animal to intentionally ingest wood it must have a very good reason of doing so as processing wood is such an effort, both in mechanical digestion (chewing) and chemical digestion. The absence of little twigs from the coprolites pretty much rules out accidental ingestion while foraging leaves.

On the other hand, the author found signs of fungal decomposition in the wood material. So apparently, the hadrosaur was eating fungus-infected, or in other words, rotting wood. Fungus de-lignifies wood and makes cellulo…