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Showing posts from April, 2008

Allosaurus fragilis 3: Allosaurus yet again...

Yes it is, it's Allosaurus fragilis yet again! The point is, Allosaurus is by far the easiest theropod to draw...I don't know why, but perhaps it's because you see images of Allosaurus skulls everywhere, being depicted as the "generic" theropod. Of course it is one of the most abundant theropods ever so we do have a good idea of its morphology and to a certain extent its ontogeny - the vast majority of fossils are of adults or subadults while juveniles and hatchlings are very rare.

I use Allosaurus when I am testing out new ideas, whether it be biomechanics or just new angles to draw...certainly this is the case of the latter. It's not entirely a ground-breakingly new angle at all but one that I have attempted in numerous previous accounts and have never really gotten right. Though, I think I've got it almost right this time. I find angled shots really difficult - as you may have noticed, most of my drawings have got the skulls captured in a lateral aspect…

Ceratosaurus nasicornis

One of my all-time favourite theropod is for some reason Ceratosaurus nasicornis. You might think its the horns but I'm actually more drawn to the overall skull morphology. I can't remember now why but Ceratosaurus was one of the first theropods that I attempted to draw the skull of. So I guess it was the first theropod that I actually paid attention to the skull morphology in some detail...

In any case, Ceratosaurus is still a taxon of significance. It represents the diverse group of basal theropods otherwise known as Ceratosauria, though what constitutes the group has never been stable. Aside from Ceratosaurus, Ceratosauria has traditionally included such taxa as Elaphrosaurus, Dilophosaurus, Coelophysis, Syntarsus, abelisaurids and other "ceratosaurs". Recent work however seem to show Ceratosauria in this traditional sense to be unsupported. Most recent phylogenies would separate coelophysoids (Coelophysis, Syntarsus, possibly Dilophosaurus, etc.) from Ceratosauri…

More on jaw muscle reconstructions

I have some more old images of mine, this one is of the jaw muscle reconstructions in Deinonychus. The skull is reconstructed from Ostrom's (1969) original figures. And jaw muscles are based on personal observations in numerous modern bird species. Off the bat it's obvious I've only referred to birds and not crocodilians or other diapsids because of the way I've reconstructed the MAMES attaching with a tendonous attachment onto the coronoid process. The muscle attached to the dorsal and medial surfaces of the surangular just medial and posterior to the MAMES is the MAMEM. In contrast, the MAMES in crocodilians attach along the dorsal surface of the surangular with the MAMEM attaching just medial to that. I suspect given the arrangement of cranial bones that the muscles arrangements in theropods would be more similar to crocs (and other diapsids) than to birds. The MPT is reconstructed as wrapping around the ventral side to attach to the lateral surface of the angular a…

Centrosaurus

I've broken my routine and drew a Centrosaurus instead of a theropod. I couldn't decide what theropod I wanted to draw but I was getting a bit bored of theropods.

Anyway, I guess this would be Centrosaurus apertus Lambe, 1904 because of the cranial ornamentation. C. apertus and C. brinkmani Ryan et Russell, 2005 differ in their cranial ornamentations with C. apertus having larger parietal ornamentations. C. brinkmani is also restricted to the Oldman Formation of southern Alberta.

I don't really know enough about ceratopsians to write anything interesting (I just think they look great!) but I might as well comment on the forelimb posture...for the longest time, there has been a debate regarding the forelimb posture of ceratopsians. Some argued for an erect parasaggital posture while others argued for a sprawling posture with the humerus averted laterally. Anatomically, the sprawling posture seems to make sense. However, this left a discrepancy with ceratopsian trace fossils t…

Dromaeosaur head dissection

I was going through my older drawings and came across this. It's quite comical but its a dromaeosaur head midway through dissection. The skin has been peeled off to reveal the jaw adductor muscles, jaw depressor muscle, parts of the neck muscles, and trachea. I got this idea from my own numerous dissections of bird heads. Minus the fact that this looks like a dinosaur, the initial phases of dissections in bird heads also look something like this...

Even in birds there really isn't much of a subdermal layer of muscles, except some really thin sheets that presumably control the feathers. But other than that, archosaurs don't have facial muscles seen in mammals and the skin is pretty much attached directly to the skull and mandibles in most parts, especially the rostrum.

The jaw adductors visible in this phase are the M. adductor mandibulae externus (MAME) superficialis (MAMES) filling the lateral temporal fenestra, MAME medialis (MAMEM) occupying the supratemporal fenestra, an…

Be the Dinosaur: a travelling museum exhibit

For some time now, I have been working as a scientific consultant on a travelling museum exhibit called Be the Dinosaur. The main attraction to this exhibit is the virtual simulation of the Late Cretaceous Hell Creek Formation. Visitors can navigate through the environment as a Tyrannosaurus rex or a Triceratops and try and complete some tasks, such as gathering food, or crossing a river, etc. However, in order to survive these simulations, the visitor must be very keenly aware of what they need to do and where to look for necessary stuff such as energy-rich food - the dinosaurs have a virtual digestive system and need to stock up energy for severe tasks like fording rivers. These information are provided in the panel-based education kiosks located throughout the exhibit so you can't skip the kiosks and go straight into the simulator pods - because you won't be prepared to survive. I think this is a clever way to educate visitors in various fields of science associated with di…

Suchomimus tenerensis: colour

Phew...so this is an Adobe Illustrator version of the Suchomimus drawing from a few days ago. As always, I used Illustrator to trace out the outline and then use different layers to colour, shade, and add a bit of effect. The stripes took me forever to do...

DinoBase, 1 year anniversary coming up!

Well, it's almost a whole year since the launch of the new DinoBase. The actual one-year anniversary for the relaunch is the 17th of April (see here for my post on the launch day last year). I'm sure most of my readers are already aware, DinoBase is an online resource hosted by the Department of Earth Sciences, University of Bristol which I just happen to be the administrator of. The main feature of DinoBase is as the name suggests, its online database of dinosaurs. Visitors can search for dinosaurs using a number of search criteria such as genera, species, author, or year of description. I'll just go through the basic search function here.

Let's say we want to search for Tyrannosaurus rex but can't be bothered to spell out the whole name so we type in "tyranno".


Now we click on "search" and DinoBase will return the following list:


Note that DinoBase returns all records alphabetically, so the first few are the ones of interest, in this case, Tyrann…

Sinraptor dongi

Second drawing of the day...though the date has changed already. This is Sinraptor dongi an allosauroid from the Jurassic of Xinjiang, China. There are two recognised species of Sinraptor, S. dongi and S. hepingensis. S. hepingensis was initially described as the third species of Yangchuanosaurus after Y. shangyouensis and Y. magnus (Gao 1992 Vertebrata PalAsiatica30: 313-324) but was subsequently assigned to the genus Sinraptor (Currie and Zhao 1993 Canadian Journal of Earth Sciences30: 2037-2081). Compared to Yangchuanosaurus, Sinraptor has a relatively longer and lower skull. The two genera are united as Sinraptoridae. One of the distinchuishing features of sinraptorids is the high number (more than two) of accessory openings in the antorbital fossa. Another interesting feature of Sinraptor is the tall plate-like neural spines of the dorsal vertebrae. This is quite similar to Metriacanthosaurus such that Paul (1988 Predatory Dinosaurs of the World) synonymised Yangchuanosaurus with…

Suchomimus tenerensis

Ok. Back to my usual passion - drawing theropods. This time, it's Suchomimus tenerensis. As always, I ran out of paper but this time, I scotch-tapee another piece of paper to fit the tail...however, the extra length made it too big for my scanner so I had to scan it in twice and stitch them together using Photoshop...

Anyway, a bit about Suchomimus - though this dinosaur is really famous that I probably won't have anything unique to comment on. Suchomimus is a spinosaurid dinosaur from the Lower Cretaceous (Aptian) of Niger (Sereno et al. 1998). It is quite distinctly different from the other famous African spinosaur Spinosaurus in snout morphology and in the lack of the giant sail - although Suchomimus also has elongated neural spines along the posterior dorsal, sacral, and anterior caudal vertebrae. The elongation is most pronounced in the sacral vertebrae but it is nowhere as long as those seen in Spinosaurus.

Along with the slightly older Baryonyx from the UK and contemporar…

Evolutionary theories...hurt my head

It's been some time since my last post...

Anyway, I've been busy trying to write a manuscript on the evolution of bite forces using finches and cats as case studies. One thing I've found out through this process is that, it doesn't matter how sophisticated a method you use, nor does it matter how great you think your results look, what matters is your ability to tie that into a broader perspective of evolutionary theory. And I've sadly realised, that either I don't have the brains, or the imagination, or the creativity, to write anything remotely interesting in the grand scheme of evolutionary theory. Evolutionary theory's the interesting end-product of all this functional morphology and phylogenetic comparative methods anyway, and if you can't do that, then you're screwed...

But I don't intend to be lazy and give up. At the same time I've been trying to be greedy. So I've been trying to read as much evolutionary theories as I can...


....a…