Skip to main content

Jaw biomechanics of Smilodon fatalis 2

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 forces in large carnivores, Adam's study on PCSA in large cats will most definitely be a valuable resource for functional morphologists.

Another cool talk was one by Blair van Valkenburg and Graham Slater (delivered by van Valkenburgh) on the cranial morphology of sabre-tooths. Results from a geometric morphometrics analysis was presented on the cranial morphology of extant cats and different sabre-tooths. Interestingly, sabre-toothed felids (macairodonts) are extreme morphotypes of modern cats diverging from extant feline morphology in which the rostrum becomes more upturned. If I remember correctly, similar trends can be seen in sabre-toothed nimravids as well. So this morphological trait of an upturned rostrum is pretty much associated with hypertrophied canines. It does make sense to have a more upturned snout if you've got massive canines.

Van Valkenburgh also briefly mentioned something interesting which made me think a bit. She suggested that perhaps sabre-tooths were extremely fast killers. At the time it didn't make much sense to me as I'd thought that sabre-tooths probably bit off chunks of flesh from the prey and waited for it to die of shock and loss of blood (Akersten 1985). However, I eventually grasped the potential that sabre-tooths may have bit into the throat much like some large cats do today but completely severed the trachea and any large arteries thus killing the prey almost instantaneously. When modern cats go for the throat or muzzle it tends to be a rather lengthy process as the canines sometimes don't even break the skin and they have to wait for the prey to suffocate (if I'm not mistaken - at least that's what it sounded like from the talk).

So the bottom line is: any kind of hunting strategy could have been possible for Smilodon as long as they kept their canines away from forceful contact with bones...

Akersten, W. A. 1985. Canine function in Smilodon (Mammalia; Felidae; Machairodontinae). Contributions in Science 356:1-22.

Binder, W. J., and B. Van Valkenburgh. 2000. Development of bite strength and feeding behaviour in juvenile spotted hyenas (Crocuta crocuta). Journal of Zoology 252:273-283.

Thomason, J. J. 1991. Cranial Strength in Relation to Estimated Biting Forces in Some Mammals. Canadian Journal of Zoology-Revue Canadienne De Zoologie 69(9):2326-2333.


Will Baird said…
Anyone considered doing a similar set of studies - albeit a bit more limited - for the other sabre-toothed synapsids? Like, oh, the therapsids such as the gorgonopsids?

It would make for an interesting comparison if nothing else.
Mambo-Bob said…
I haven't heard of any. Everyone seems to be interested in sabre-toothed machairodonts, nimravids and marsupials...

Popular posts from this blog

R for beginners and intermediate users 3: plotting with colours

For my third post on my R tutorials for beginners and intermediate users, I shall finally touch on the subject matter that prompted me to start these tutorials - plotting with group structures in colour.

If you are familiar with R, then you may have noticed that assigning group structure is not all that straightforward. You can have a dataset that may have a column specifically for group structure such as this:

B0 B1 B2 Family
Acrocanthosaurus 0.308 -0.00329 3.28E-05 Allosauroidea
Allosaurus 0.302 -0.00285 2.04E-05 Allosauroidea
Archaeopteryx 0.142 -0.000871 2.98E-06 Aves
Bambiraptor 0.182 -0.00161 1.10E-05 Dromaeosauridae
Baryonychid 0.189 -0.00238 2.20E-05 Basal_Tetanurae
Carcharodontosaurus 0.369 -0.00502 5.82E-05 Allosauroidea
Carnotaurus 0.312 -0.00324 2.94E-05 Neoceratosauria
Ceratosaurus 0.377 -0.00522 6.07E-05 Neoceratosauria
Citipati 0.278 -0.00119 5.08E-06 Oviraptorosauria

The difference between Lion and Tiger skulls

A quick divergence from my usual dinosaurs, and I shall talk about big cats today. This is because to my greatest delight, I had discovered today a wonderful book. It is called The Felidæ of Rancho La Brea (Merriam and Stock 1932, Carnegie Institution of Washington publication, no. 422). As the title suggests it goes into details of felids from the Rancho La Brea, in particular Smilodon californicus (probably synonymous with S. fatalis), but also the American Cave Lion, Panthera atrox. The book is full of detailed descriptions, numerous measurements and beautiful figures. However, what really got me excited was, in their description and comparative anatomy of P. atrox, Merriam and Stock (1932) provide identification criteria for the Lion and Tiger, a translation of the one devised by the French palaeontologist Marcelin Boule in 1906. I have forever been looking for a set of rules for identifying lions and tigers and ultimately had to come up with a set of my own with a lot of help fro…

Top 10 scientifically important theropod dinosaurs of all time (off the top of my head)

I thought I'd do a fun post for once. And since list based articles are the norm for fun on the internet, I thought I'd do one on dinosaurs, but given that I know most about theropods, I've decided to restrict my list to theropods (...maybe in a future post, I'll do other clades).

My ranking is based mostly on scientific importance so it may not reflect awesomeness, and it is obviously subjective as to how I rank importance to science. For instance, interesting discoveries or unique palaeobiology are ranked relatively low compared to wealth of information and data or completely revolutionising our understanding of the evolution of theropods.

So here are my top 10 scientifically important theropod dinosaurs of all time (off the top of my head)

10. Megalosaurus

Being the first dinosaur to be named, Megalosaurus automatically deserves a spot on this list, but given the fragmentary nature of known fossil specimens, and being mostly useless as a meaningful source for biologi…