Raptor's Nest

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...

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draw flight feathers on this guy mostly because of the simpler integuments of Sinornithosaurus but its quite obviously outdated now that we know one of its closest relative Velociraptor was found to have quill knobs on its ulna.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.

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...

This is one of my favorite dinosaurs - Eustreptospondylus oxoniensis . It's also perhaps one of the most complete theropod fossils from Britain. Eustreptospondylus is a Middle Jurassic 'megalosaur' from the Oxford Clay of Oxfordshire. Now, I'm not much of a historian so I won't claim to know all the details, but it was known for a long time as ' Streptospondylus ' but was subsequently renamed by Walker in 1964 in his paper ' Triassic reptiles from the Elgin area: Ornithosuchus and the origin of carnosaurs '. Ornithosuchu s is nowadays regarded as an archosaur so for some time, I was baffled as to why Walker addressed the question of carnosaur origins by redescribing a Triassic archosaur. However, it appeared I was just being lazy (as usual) as I had not even read the abstract. It is made quite clear that Walker considered Ornithosuchus to be a theropod dinosaur, a primitive carnosaur close to the ancestry of Megalosauridae and Tyrannosauridae. Thu...

I attended the 8th International Congress of Vertebrate Morphology (ICVM8) in Paris last week. There were a lot of interesting talks and I personally felt like I had information over-load! One talk in particular that I found extremely interesting was that by Adam Hartstone-Rose, a PhD student at Duke University, who had painstakingly collected data of the physiological cross-sectional areas (PCSA) of extant felids, something I've always thought was in dire need. I'm particularly interested in this because this allows us to estimate bite forces in felids to a fair amount of accuracy. The most common source for bite force estimates in mammalian carnivores come from dry skulls which have been shown to underestimate (Thomason 1991). Bite forces estimated from calculations based on PCSA on the other hand seem to be in more congruence with actual in vivo bite forces (Thomason 1991). As there are currently no studies except for Binder and van Valkenburgh (2000) on in vivo bite force...

I've been looking at and taking measurements from felid skulls now for a few weeks. I've been up in Edinburgh at the National Museum of Scotland for three days and I've also been at the osteological collections at the Bristol City Museum and Art Galleries for the last week now. I've covered 30 species of the 41 recognised extant felid species. The funny thing is that some of the older specimens in the Bristol Museum are either mislabeled or not labeled at all and we sat there for some time comparing specimens trying to ID the damned things. I'm starting to pick up some subtle morphological distinctions but it's all kind of useless unless I can link them to the right species. All I need is a list of diagnostic characters...

Biomechanically, Smilodon fatalis is an interesting animal. Where most extant felids have big strong canines, S. fatalis had long flat ones. This implies that Smilodon would not have been capable of the same kind of precision biting that modern cats employ. Struggling with prey to deliver a fatal bite to the nape of the neck and dislocating the cervical vertebrae would result in the canines contacting with bone. The long flattened canines of Smilodon probably would not have withstood that kind of load. The canines of Smilodon don't look like stabbing teeth like in modern cats, instead they look more like slicing teeth - like in Komodo dragons. To the left is a tiger skull for comparison. The tiger has a lower longer face, larger eyes, and above all has pronounced zygomatic arches. Smilodon on the other hand had smaller zygomatic arches. This reduced the amount of available space for the temporalis muscle thus reducing the overall muscle force. The tiger also has huge coronoi...