Functional Morphology of Animal Feeding Apparata

[theropod]

Aug 22, 2019 16:21:26 GMT 5 Infinity Blade said:

I think big predatory dinosaur skulls do too(?), but I'm not sure

Yes, probably.

Christiansen’s study also contains all data necessary for a bite force comparison:
mass 73.3 kg, skull 230 mm, 879.5 N (canine), 1348.0 N (carnassial)
These are dry skull estimates, so it would probably be most appropriate to compare them to sue’s estimate from McHenry (2009) rather than Stan’s from Bates & Falkingham.
skull 1497 mm, 16 841 N (anterior), 26 091 N (posterior)

(8400/73.3)^(1/3)*230 = SL (isometric) = 1117 mm

(8400/73.3)^(2/3)*879.5 = canine BF (isometric) = 20 750 N
(8400/73.3)^(2/3)*1348.0 = carnassial BF (isometric) = 31 803 N


So it’s probably a good guess to say T. rex would have a bite force very similar to a jaguar when corrected for body mass.

And just for fun, the allometric values:

(8400/10^-4.638)^(1/2.762) = SL (allometric) = 1259 mm
(1259/230)^2*879.5 = canine BF (allometric) = 26 353 N
(1259/230)^2*1348.0 = carnassial BF (allometric = 40 391 N

Note that I don’t know what exactly Christiansen’s skull length measurement is, if it’s basal or condylobasal, then the maximum skull length would be larger.

[Infinity Blade]

This is probably a dumb question but I assume that the anterior bite force described for Tyrannosaurus corresponds to the anteriormost incisiform teeth, right? Not the caniniform teeth (which are found in the maxilla and roughly correspond in position to the canines of a mammal)?

[theropod]

It’s actually a very good question, because no.

McHenry 2009 said:

Three possible bite points were identified; each represents the largest upper jaw tooth in the front, middle, and rear
parts of the tooth row respectively (which tooth each one is applied to varies between species).

These are the bite points McHenry used, the one for the front was 131.5cm on front of the jaw joint. The anterior bite point isn’t the anteriormost tooth, indeed it looks like the anteriormost maxillary tooth (see Figure 7-12).

[Infinity Blade]

theropod

Since we were now discussing bite force, I felt it was better and fitting to move the last three posts into this thread.

The interesting thing is that T. rex's posterior bite force is ~55% harder than its anterior bite. For the jaguar, it's ~53%. I was expecting the jaguar's short jaws would make it so that bite force at the canines wasn't that much lower than bite force at the carnassials.

[creature386]

I've been googling for pictures of the Tyrannosaurus' and the jaguar's jaw adductor muscles and here's what I've found.

Tyrannosaurus:

www.researchgate.net/figure/Jaw-adductor-muscle-model-for-Tyrannosaurus-rex-BHI-3033-in-A-dorsal-C-left_fig2_317028057
Jaguar:

www.researchgate.net/figure/Mandibular-adductor-origins-o-and-insertions-i-lateral-view-Muscle-abbreviations_fig7_296120723

To me, it looks as if the theropod's jaws are not just slightly longer, but its adductor muscles are also extending slightly further to the anterior end. That might at least be part of the reason why the difference is so small.

[Verdugo]

Aug 22, 2019 17:25:38 GMT 5 Infinity Blade said:

This is probably a dumb question but I assume that the anterior bite force described for Tyrannosaurus corresponds to the anteriormost incisiform teeth, right? Not the caniniform teeth (which are found in the maxilla and roughly correspond in position to the canines of a mammal)?

The Mid position in McHenry directly corresponds to the Caniniform in T-rex (i have made a post on this). I suppose that would make a more apple to apple comparison, canine to caniniform, no?. Anyway:

T-rex Mid bite force (Table 7-7) = 19169 N

[Infinity Blade]

Aug 22, 2019 19:01:55 GMT 5 Verdugo said:

Aug 22, 2019 17:25:38 GMT 5 Infinity Blade said:

This is probably a dumb question but I assume that the anterior bite force described for Tyrannosaurus corresponds to the anteriormost incisiform teeth, right? Not the caniniform teeth (which are found in the maxilla and roughly correspond in position to the canines of a mammal)?

The Mid position in McHenry directly corresponds to the Caniniform in T-rex (i have made a post on this). I suppose that would make a more apple to apple comparison, canine to caniniform, no?. Anyway:

T-rex Mid bite force (Table 7-7) = 19169 N

Yes, you are right. That's why I was wondering.

[Verdugo]

I always think the pterygoid muscle in T-rex might have been underestimated. In modern reptiles that independently evolved to bite really hard for whatever purposes, usually have bulging pterygoid muscles that extend far beyond what their skull morphology would indicate. For instance:

Tegu


And of course, Crocodilians


I will probably look more into this some times down the road

[Infinity Blade]

theropod

Actually, I just remembered (and I can’t believe I forgot this earlier) that Sakamoto et al. (2019) made their own dry skull estimates for two different T. rex specimens, particularly Stan and AMNH 5027. Their minimum “functional bite force” estimate for Stan is on par with McHenry’s posterior bite force figure for Sue, and their maximum force figures are significantly higher than McHenry’s estimate. I made a post about this on page 12, which in fact was the basis for the size comparison I made and the whole conversation that ensued.

[theropod]

Sorry, totally overlooked that. Well, that should of course be considered, then.

[theropod]

I have to amend my statements regarding Pliosaur teeth:
Massare (1987) describes the ridges on Liopleurodon teeth as sharp and serrated, sufficiently to serve as cutting edges, even though the whole tooth is round in cross-section. She further suggests that this form became modified into the trihedral tooth shape of Pliosaurus during the Upper Jurassic, making two of these ridges more prominent. She also illustrates a tooth of P. brachydeirus, which is also serrated, so this also seems to be the case in this taxon.

Massare, J.A. 1987. Tooth morphology and prey preference of Mesozoic marine reptiles. Journal of Vertebrate Paleontology 7 (2): 121–137. tandfonline.com/doi/pdf/10.1080/02724634.1987.10011647

[Infinity Blade]

An oft-repeated factoid about the slow loris is that it is the only venomous primate. The brachial gland on the ventral surface of the elbow supposedly secretes the venom and the loris licks this gland. The dental combs (needle-like teeth on the lower jaw) are thought to inject the venomous brachial gland exudate into victims.

Or so it’s thought. According to the link below there is no clinical evidence demonstrating that the slow loris’ bite is venomous.

primatology.net/2010/10/19/are-slow-lorises-really-venomous/

[Infinity Blade]

As is probably known around here, leopard seal postcanine teeth are used for sieving/filter feeding krill, not for piercing and tearing relatively large prey like penguins and other seals. The postcanine teeth are actually described as being delicate.

The lack of abrasive wear on the postcanine dentition supports the hypothesis that these teeth, and their long sharp cusps, are primarily used for sieving, rather than for piercing prey during grip-and-tear feeding as suggested by Adam and Berta (2002). Abrasive wear on the canines and incisors is congruent with descriptions of these teeth being used to pierce and hold large prey as it is shaken apart prior to swallowing (Hamilton 1939; Edwards et al. 2010); since the postcanines do not show similar amounts of abrasive wear, they probably are not frequently used in a similar fashion. The relatively delicate morphology of the leopard seal’s multi-cusped postcanines (when compared to other grip-and-tear feeding marine mammals such as the killer whale) may constrain this species’ predatory capacity by leading them to adopt their prey shaking, grip-and-tear handling technique when dealing with large prey. Although slower and energy intensive (Rogers 2009), this method involves holding large prey with the robust anterior teeth during shaking and thus limits postcanine abrasion or fracture, which could otherwise reduce efficiency of the postcanine teeth in retaining small prey during the water expulsion and sieving that follows suction.

www.academia.edu/2059106/Leopard_seals_Hydrurga_leptonyx_use_suction_and_filter_feeding_when_hunting_small_prey_underwater



PCA of the postcanine teeth of leopard seals also shows them to be relatively blunt.

The origin of baleen whales (Mysticeti), the largest animals on Earth, is closely tied to their signature filter-feeding strategy. Unlike their modern relatives, archaic whales possessed a well-developed, heterodont adult dentition. How these teeth were used, and what role their function and subsequent loss played in the emergence of filter feeding, is an enduring mystery. In particular, it has been suggested that elaborate tooth crowns may have enabled stem mysticetes to filter with their postcanine teeth in a manner analogous to living crabeater and leopard seals, thereby facilitating the transition to baleen-assisted filtering. Here we show that the teeth of archaic mysticetes are as sharp as those of terrestrial carnivorans, raptorial pinnipeds and archaeocetes, and thus were capable of capturing and processing prey. By contrast, the postcanine teeth of leopard and crabeater seals are markedly blunter, and clearly unsuited to raptorial feeding. Our results suggest that mysticetes never passed through a tooth-based filtration phase, and that the use of teeth and baleen in early whales was not functionally connected. Continued selection for tooth sharpness in archaic mysticetes is best explained by a feeding strategy that included both biting and suction, similar to that of most living pinnipeds and, probably, early toothed whales (Odontoceti).

The first two principal components together account for 85.8% of the total variance, and clearly separate out leopard and crabeater seals because of their relatively blunt intercusp notch and rounded anterior/posterior edges of the main cusp (figure 2). Harp (Pagophilus groenlandicus) and harbour seals (Phoca vitulina) also have relatively blunt notches, but retain sharp blades on their main cusps. Extinct cetaceans, including toothed mysticetes, largely fall within the morphospace defined by extant terrestrial carnivorans and non-filtering pinnipeds, all of which use their teeth to pierce and hold prey (i.e. for raptorial feeding). Surprisingly, toothed mysticetes are closer to terrestrial carnivorans and archaeocetes than either †Squalodon or any of the pinnipeds. The DFA also separates leopard and crabeater seals from all other extant carnivorans and, based on the resulting discriminant function, groups the fossil cetaceans with the modern raptorial species (figure 2).

royalsocietypublishing.org/doi/full/10.1098/rsbl.2017.0348



Also, interestingly enough, the leopard seal's canines and incisors have been claimed to be not all that different from those of other seals. It's arguably the only extant macrophagous pinniped, but it shows no specialization for the habit, only for sieving krill.

When it feeds upon large bodied prey, it nips with its incisors and canines – which are not really any different from those of fish-eating pinnipeds. In other words, the only modern pinniped which could be argued to be a macrophagous apex predator only has dental specializations for feeding upon krill.

Blog post by Robert Boessenecker->

[Infinity Blade]

Nov 3, 2017 23:11:11 GMT 5 Infinity Blade said:

CORTICAL VS TRABECULAR BONE AND THE SPECIALIZED KILLING BITE OF SABER-TOOTHS
FIGUEIRIDO, Borja, University of Málaga, Málaga, Spain; PÉREZ-RAMOS, Alejandro, University of Málaga, Málaga, Spain; VAN VALKENBURGH, Blaire, university of California Los Angeles, Los Angeles, CA, United States of America

"The repeated evolution of elongate and laterally compressed (saber-like) canine teeth in different lineages of carnivorous mammals is one of the most spectacular cases of convergent evolution towards a specialized killing behavior. Although scimitar-toothed and dirk-toothed sabertooths have been traditionally identified as different ecomorphs, it is not clear whether these morphs deployed different killing bites. Here we use histologically-based algorithms to quantify the volume of cortical and trabecular bone in coronal sections of complete skulls to create biomechanical profiles of the ‘scimitar toothed’ Homotherium serum and in the ‘dirk-toothed’ Smilodon fatalis, as well as in a comparative sample of living carnivores, including the ‘conical-toothed’ Panthera leo. Whereas trabecular bone is well suited to deal with continuous and repetitive loads, cortical bone is better able to dissipate larger, more localized stresses. Our data indicate that Smilodon has much thicker cortical bone in its rostrum than other taxa. In the posterior region of the skull, cortical bone thickness is similar in Homotherium and Smilodon, but greater than in P. leo. In the same region, the trabecular bone in Homotherium is thicker than in Smilodon but thinner than in P. leo. Our results suggest that the two ecomorphs of saber-tooths differ in the distribution and quantity of cortical and trabecular bone across their skulls, reflecting different behaviors during prey dispatch. The thickened rostrum of Smilodon suggests that it deployed one or two very strong killing bites with its canines, whereas Homotherium might have used multiple, less forceful slashing bites. This suggests that the saber-tooth killing repertoire was more complex than previously suspected."

Grant Information:
Spanish MINNECO (Grants CGL2012-37866; CGL2015-68300P).
Technical Session XIX (Saturday, August 26, 2017, 3:45 PM)

vertpaleo.org/Annual-Meeting/Annual-Meeting-Home/SVP-2017-program-book-7-20-17a-(1).aspx

The full paper is out now.

sci-hub.tw/10.1016/j.cub.2018.08.012

[Verdugo]

Does anyone knows any T-rex BF studies that are done in 3D FEA? I know there are 3D BF studies of T-rex in Bates et al and Erickson et al but i don't think neither studies actually employed 3D FEA.