Functional Morphology of Animal Feeding Apparata

[theropod]

Back then, it may not have been recognised that Carcharodontosaurus had recurved, ziphodont teeth, much like most other theropods. Don't forget his book was published quite a while before SGM-DIN 1 was discovered.
Stromer initially described a straight, tringular tooth morphology similar to a shark's, based on an unerupted (perhaps abnormal?) tooth in the holotype. Perhaps that's what inspired Paul to try and draw some sort of functional distinction between it and other theropods, even though his phrasing doesn't make much sense to me. But by now it appears clear that most teeth were of the typical, recurved theropod-type (albeit exceptionately flat and broad-bladed).

[creature386]

Hm, aren't teeth among the things you pretty much always find when you have a partial skull from a dinosaur (and from what I know, there was a partial skull of BSP 1922 X46)?

[Infinity Blade]

Alright, well, Carcharodontosaurus wasn't the only dinosaur that he thought would cut out wounds, and by that, I think he means something like this



instead of this



In fact, he doesn't really go more in depth with Carcharodontosaurus aside from its supposedly/erroneously straight, triangular teeth. He explains his idea that tyrannosaurids would have done this twice in the book (although I haven't read the whole thing) on account of the D cross-sectioned premaxillary teeth (with the serrated bicarinae on the back) lined in a U-shaped dental arcade, allowing them to scoop out flesh. But again, isn't it kind of the idea that these bladed-toothed theropods would bite out a chunk of flesh (like in the former image) and not just create lacerations (like in the latter image)?

[theropod]

creature386 :
This is what stromer writes on the matter:

Zähne Die Reihe der funktionierenden Zähne der Oberkiefer ist vollkommen ausgefallen, aber in dem linken großen Oberkieferstück und in den zwei rechten Stücken sind mehrere Ersatzähne wenigstens teilweise zu sehen. In einigen Alveolen ragt nämlich die Spitze eines Ersatzzahnes, meist etwas dem Hinterrande genähert auf, am weitesten in der 2. und 7. von vorn links, wo sie fast den Oberrand erreicht, dann in der vordersten Alveole des rechten, hinteren (mittleren) Stückes. Viel tiefer darin liegt die Spitze in der hier nächstfol- genden Alveole und der Abdruck einer Zahnspitze in dem vorderen rechten Stück. Am meisten zu sehen ist der Ersatzzahn in der vordersten Alveole in dem hinteren (mittleren) rechten Stück, Taf. I, Fig. 3 und ein Wenig zerquetschte Zahnkeime ganz hinten und um 6 Zähne weiter vorn im großen linken Stück, Taf. I, Fig. 2. Alle diese Oberkieferzähne bieten dasselbe Bild: sie sind gerade, stark seitlich abge- plattet, mit gleichmäßig, sehr mäßig gewölbter Außen- und Innenseite und stärkster Wöl- bung in Mitte des Zahnes und mit zugeschärftem, wenig konvexem und fein gezähneltem Vorder- und Hinterende. Die Zähne, deren wagrechter Querschnitt ungefähr spindelför- mig ist, lassen also vorn und hinten, außen und innen kaum unterscheiden und gleichen eher solchen des Selachiers Carcharodon als den stets rückgebogenen und schlankeren der Megalosauridae.

Teeth The row of functional teeth in the upper jaw is completely dislodged, but in the large left part of upper jaw and the two right pieces several replacement teeth are at least partially visible. That is to say, in some alveoli the apex of a replacement tooth protrudes, usually somewhat close to to the posterior rim, furthest in the 2. and 7. left one from the front, where it almost reaches the upper rim, then in the anteriormost alveolus of the right, posterior (intermediate) part. The tip in the subsequent alveolus, and the imprint of a tooth-tip in the anterior right piece are situated much further in. Most completely visible is the replacement tooth in the anteriormost alveolus of the posterior (intermediate) right piece, plate I fig. 3 and slightly crushed tooth germs at the posterior end and 6 positions further anterior in the large left piece, plate I, fig. 2. All these upper teeth present the same picture: they are straight, strongly flattened transversely, with consistently weakly convex outer and inner surfaces and the region of most pronounced convexity in the mid-part of the tooth, and with sharpened, sparsely convex and finely serrated anterior and posterior ends. The teeth, whose horizontal crosssection is roughly spindle-shaped, thus barely allow distinction between anterior and posterior, medial and lateral, and resemble more those of the selachian Carcharodon than the invariably recurved and more slender ones of the Megalosauridae.

Further down he remarked on some tooth fragments that showed a more recurved morphology, but in general, and that’s what he named the animal for, he based his observations of the tooth morphology on the replacement teeth mentioned above, because the functional dentition had fallen out. I really don’t have a good explanation for why those replacement teeth were so aberrant while the vast majority of Carcharodontosaurus teeth are so much more "normal" though.


Infinity Blade : I doubt tyrannosaurid incisiform teeth were used to inflict injuries by flesh-extracting, their morphology rather seems feeding-related. D-shaped crosssections don’t exactly reflect a perfect slicing morphology (or anything close to what extant chunk-cutters have) either, rather a compromise between providing something more suited to scraping the meat off the carcass than the large mid-maxillaries, but yet withstanding the force of the killing bites.

Am I right in assuming the latter picture is a Varanus bite?
I think like varanids, most ziphodont theropods did both, depending on what they were biting. In the case of the wound on that hand, the varanid probably wasn’t overly big compared to the human whose hand it bit, more likely smaller by quite a margin. On the other hand, the shark, which, judging by the bite wound, may be a 3m+ great white, was probably a lot larger than the seal. The shark also bit (and generally bites) a body region with very different consistency to a human hand, a consequence of aquatic tetrapods generally being softer-bodied/having less bony areas and appendages than terrestrial ones.
I’ve read and seen accounts of komodo dragons tearing large chunks of tissue from the abdomens of their prey, but that’s not at odds with causing simple slice wounds when biting a bony distal limb element to cut the tendons.

No idea what unspoken thoughts others have on this, of course, but I’d certainly assume carnosaurs and equivalent theropods had the ability to take out chunks (though obviously very different in shape and with a more anteroposterior motion than sharks or even varanids), but would also happily refrain from doing that where appropriate (by quick nipping bites used to sever something vital, as opposed to more drawn-out tearing bites to rip off large amounts of meat on all sides).

[Infinity Blade]

I doubt tyrannosaurid incisiform teeth were used to inflict injuries by flesh-extracting, their morphology rather seems feeding-related. D-shaped crosssections don’t exactly reflect a perfect slicing morphology (or anything close to what extant chunk-cutters have) either, rather a compromise between providing something more suited to scraping the meat off the carcass than the large mid-maxillaries, but yet withstanding the force of the killing bites.

Well, I don't think that they'd really slice per se (because as you said, they're not morphologically adapted for it), but maybe heave out flesh like, as GSP put it, a trowel in dirt (the flat side wouldn't slice meat behind it, but with sufficient force it could then act like a scoop). Maybe their primary function really did pertain to feeding (I find this very likely), but I can see where GSP is coming from; I wouldn't be surprised if they could, at least at times, do something remotely similar to what GSP described against a live creature.

Am I right in assuming the latter picture is a Varanus bite?

Yes. Apparently, it was from a crocodile monitor (Varanus salvadorii).

In the case of the wound on that hand, the varanid probably wasn’t overly big compared to the human whose hand it bit, more likely smaller by quite a margin. On the other hand, the shark, which, judging by the bite wound, may be a 3m+ great white, was probably a lot larger than the seal.

I know, I was only really concerned with was the appearance/nature of the injuries.

[Infinity Blade]

Mark Witton and Darren Naish's work on Hatzegopteryx's neck and head and predatory ecology is finally out!

The emerging picture is rather different for Hatzegopteryx. Here, we can plug our results of a relatively short, strong neck and high fractions of cervical musculature into its overall robust construction, reinforced bones, massive and wide jaws, and stupendous size. Collectively, this paints an image of a far more solidly built and powerful animal than Arambourgiania. If - as most of us now seem to think - azhdarchids were 'terrestrial stalkers', we can imagine Hatzegopteryx as as a giant azhdarchid turned up to 11: a prairie-roaming giant with elevated maximum prey size and capacity for violent and forceful foraging tactics. Given how dangerous we know modern azhdarchid-like birds can be, and armed with a powerful neck and giant, reinforced skull, we might even imagine Hatzegopteryx using powerful bites, bludgeoning blows of its head and stabbing motions to tackle prey too large to swallow whole. If we're right, Hatzegopteryx was both a truly awesome, but also entirely terrifying animal. There is not exact modern analogue for this sort of creature, but if you imagine a giant mix of a shoebill stork, a ground hornbill, and the Terminator you might be pretty close.

markwitton-com.blogspot.com/2017/01/new-paper-when-short-necked-giant.html

[Infinity Blade]

Here's an interesting read. It proposes that Smilodon would have killed its prey by creating a pneumothorax with a closed-mouth stab. I'll post the abstract.

"Smilodon fatalis was a large extinct felid distinguished by their two impressive maxillary canines and surprisingly low canine fracture rates. Previous theories regarding their attack strategy have suggested delivering damage by a bite with their maxillary canines. It has also been previously suggested that the canines could have been used to deliver a non-biting stab with an open jaw. It has been generally hypothesized that the attack was delivered to the neck of their large herbivore prey. Smilodon fatalis could have used their canines in a non-biting stab delivered with a closed jaw for the sole purpose of creating a pneumothorax. Creation of a pneumothorax would maximize immediate attack lethality, and minimize exposure of its canines to fracture."

file.scirp.org/Html/6-1400102_27414.htm

[Infinity Blade]

So recently, a new paper came about Tyrannosaurus' bite force, and bite pressure, came out.

Paul M. Gignac, Gregory M. Erickson. The Biomechanics Behind Extreme Osteophagy in Tyrannosaurus rex. Scientific Reports, 2017; 7 (1) DOI: 10.1038/s41598-017-02161-w

Bite force was estimated up to 34,522 N, but pressure at the tooth tips was estimated (using calculated bite force) up to 2,974 MPa (431,342 psi).

There's also a news article reporting the publication (link) where Greg Erickson is quoted making a good point.

From their work on crocodilians, they realized that high bite forces were only part of the story. To understand how the giant dinosaur consumed bone, Erickson and Gignac also needed to understand how those forces were transmitted through the teeth, a measurement they call tooth pressure.

"Having high bite force doesn't necessarily mean an animal can puncture hide or pulverize bone, tooth pressure is the biomechanically more relevant parameter," Erickson said. "It is like assuming a 600 horsepower engine guarantees speed. In a Ferrari, sure, but not for a dump truck."

Now, this study was interesting, but I still have one query.

If I understand things correctly, peak bite forces are significantly higher than sustained bite forces. Blaze once noted that peak bite forces in an adult Tyrannosaurus (I think from Bates and Falkingham's study) were 3-4 times greater than sustained bite force figures (35-57 kN). If this study's figures are sustained bite forces, then wouldn't Tyrannosaurus actually be capable of tooth pressures even greater than calculated here, even if they are ephemeral?

[Infinity Blade]

Something I'm baffled by is how Sue, an >8 tonne animal, had a bite force just over twice as much as a "bob-tailed, 4.51 m Australian saltwater crocodile", which would certainly have been an order of magnitude smaller (correspondingly, maximum tooth pressures for Sue were only 20% higher than recorded for a saltie: 358,678 psi vs. 431,342 psi).

Is this just an effect of comparing in vivo bite forces to non-in vivo estimates? Or can crocodiles really bite that much harder than Tyrannosaurus on a proportional basis?

[Infinity Blade]

Why do I feel like I kind of know (or rather, confident to) the answers to my questions, but am simply seeking confirmation or negation for them? Lol.

Anyway though, contributing more to this thread. Information on Kolponomos' feeding mechanics (A unique feeding strategy of the extinct marine mammal Kolponomos: convergence on sabretooths and sea otters).

Later on I'll try to share my thoughts on the Smilodon paper I posted above.

[spartan]

May 21, 2017 7:44:14 GMT 5 Infinity Blade said:

Something I'm baffled by is how Sue, an >8 tonne animal, had a bite force just over twice as much as a "bob-tailed, 4.51 m Australian saltwater crocodile", which would certainly have been an order of magnitude smaller (correspondingly, maximum tooth pressures for Sue were only 20% higher than recorded for a saltie: 358,678 psi vs. 431,342 psi).

Is this just an effect of comparing in vivo bite forces to non-in vivo estimates? Or can crocodiles really bite that much harder than Tyrannosaurus on a proportional basis?

Probably mostly the first. From McHenry:

The discrepancy between dry skull derived estimates of bite force, and observed values for the same taxa, is especially important. In all cases, observed bite force exceeds the predictions based upon the dry skull method; for example, the Alligator specimen (Figure 7-10) predicted in the present study to have a bite force of 1338 N at the rear bite position (Table 7-7) should have an in vivo bite force of 3900–4500 N.

[Grey]

May 21, 2017 7:44:14 GMT 5 Infinity Blade said:

Something I'm baffled by is how Sue, an >8 tonne animal, had a bite force just over twice as much as a "bob-tailed, 4.51 m Australian saltwater crocodile", which would certainly have been an order of magnitude smaller (correspondingly, maximum tooth pressures for Sue were only 20% higher than recorded for a saltie: 358,678 psi vs. 431,342 psi).

Is this just an effect of comparing in vivo bite forces to non-in vivo estimates? Or can crocodiles really bite that much harder than Tyrannosaurus on a proportional basis?

The 30 tonnes of pressure at the tooth tip is very impressive.

It is notable though that Deinosuchus, according to the same author and using the same method, has an even higher bite force than Tyrannosaurus, not really surprising though given how solidly built the crocodilian skull is.

However is it implying that Deinosuchus had an even more enormous pressure at tooth tip or not ?

And what the implications for the pliosaurs bite force ?

[Infinity Blade]

That didn't answer my question. Are we comparing estimation methods that severely underestimate actual bite force in life with something extrapolated from in vivo figures? See Spartan's post regarding Tyrannosaurus. And according to their methodology, Erickson et al. (2012) directly measured bite force in crocodilian species (so in vivo I suppose?); I'm guessing that they extrapolated that >100 kN bite force figure for Deinosuchus from these measurements.

If you multiply that 34,522 N figure for Tyrannosaurus by three fold, you get something nearly in line with that bite force figure extrapolated from Deinosuchus (i.e. something >100 kN), so in absolute terms these two predators should be able to bite as hard. And if you still believe the 57 kN figure by Bates and Falkingham is still within the realm of possibility, you obviously get even higher results (some 171 kN or something).

[Infinity Blade]

So, here's what I did. I decided to calculate the approximate amount of pressure a Tyrannosaurus could generate at its tooth tips with what I think are accurate approximations of in vivo bite force.

First, let's take the recently estimated figure of 34,522 N. Multiplying that by three as an approximation of in vivo bite forces gives you 103,566 N, which if you turn into lbf you arrive at 23,282.5631 lbf. From the bite force figure that corresponded to the enormous tooth pressure in Erickson's paper, I found the area to be 0.01799268 in^2 (34,522 N=7,761 lbf, psi=lbf/in^2-->lbf/psi=in^2; 7,761 lbf/431,342 psi=0.01799268 in^2). So 23,282.5631/0.01799268 gives you 1,294,001.95 psi.

If you use earlier estimations of 35 and 57 kN and give them the exact same treatment (multiply by three for in vivo forces, convert to lbf, etc.), you get tooth pressures of 1,311,919.02 psi and 2,136,533.83 psi, respectively.

If I'm right about this in vivo stuff, then Tyrannosaurus could generate pressures at its teeth numbering in the millions to splinter bones, even more so if the 57 kN figure estimated some years before is accurate and "turned into" an approximate in vivo value.

So what do you all think? Are my premises correct? Do I have a false understanding of anything?

[Infinity Blade]

Taipan posted a PDF to this paper on Carnivora. Because I don't know much about frogs, I was really surprised by the results of this study.

Bite force in the horned frog (Ceratophrys cranwelli) with implications for extinct giant frogs

"Of the nearly 6,800 extant frog species, most have weak jaws that play only a minor role in prey capture. South American horned frogs (Ceratophrys) are a notable exception. Aggressive and able to consume vertebrates their own size, these “hopping heads” use a vice-like grip of their jaws to restrain and immobilize prey. Using a longitudinal experimental design, we quantified the ontogenetic profile of bite-force performance in post-metamorphic Ceratophrys cranwelli. Regression slopes indicate positive allometric scaling of bite force with reference to head and body size, results that concur with scaling patterns across a diversity of taxa, including fish and amniotes (lizards, tuatara, turtles, crocodylians, rodents). Our recovered scaling relationship suggests that exceptionally large individuals of a congener (C. aurita) and extinct giant frogs (Beelzebufo ampinga, Late Cretaceous of Madagascar) probably could bite with forces of 500 to 2200 N, comparable to medium to large-sized mammalian carnivores."

"Our predictions for Beelzebufo also are compatible with available information on bite force in mammals. Published direct empirical measurements of voluntary bite forces in large mammals are surprisingly rare. Studies on captive colonies of two carnivorans, Crocuta crocuta (spotted hyaena) and Canis latrans (coyote), provide the only reliable empirical data. C. crocuta produced values of ~1000–4500 N for 6 + year old adults40. The greatest measurement for C. latrans, produced by an eight year-old male, was 704 N41. Bite forces estimated for Beelzebufo (UA 9269), both at the jaw tips and jaw midpoint, span the lower half of the range for C. crocuta and considerably exceed the maximum for C. latrans. Estimates of bite force derived from morphology-based models for Canis lupus (gray wolf), and Panthera leo (lion) and P. tigris (tiger) the size of adult females, are 774 N, 2024 N, and 2165 N, respectively. Our estimates of bite force at the jaw tips for Beelzebufo (UA 9269) exceed the estimated bite force for C. lupus, the latter of which is unexpectedly similar to the in vivo measurement for the much smaller C. latrans. Bite force at the jaw midpoint for Beelzebufo (UA 9269) is similar to that estimated for the largest extant cats, P. leo and P. tigris."

www.nature.com/articles/s41598-017-11968-6

It's possible those lion and tiger values are not in vivo (I don't remember), but either way, 2200 N is impressive.