Functional Morphology of Animal Feeding Apparata

[Infinity Blade]

By any chance does anyone have any measurements to confirm or refute the bolded/underlined below? I'm under the impression it's fabricated, but in any case it would be interesting to see what actual data says.

Daspletosaurus torosus is most widely accepted as the direct ancestor to Tyrannosaurus rex. The only notable differences between the two are that Daspletosaurus possesses proportionally larger teeth, longer arms, and smaller feet, and is overall more muscular and heavily built than Tyrannosaurus. Its fossils can be found in Alberta and Montana and come from a period between 77 and 74 million years BCE.

magazine.scienceconnected.org/2017/03/dinosaur-gave-rise-tyrannosaurus-rex/

[Verdugo]

Nov 1, 2019 7:17:06 GMT 5 Infinity Blade said:

By any chance does anyone have any measurements to confirm or refute the bolded/underlined below? I'm under the impression it's fabricated, but in any case it would be interesting to see what actual data says.

Daspletosaurus torosus is most widely accepted as the direct ancestor to Tyrannosaurus rex. The only notable differences between the two are that Daspletosaurus possesses proportionally larger teeth, longer arms, and smaller feet, and is overall more muscular and heavily built than Tyrannosaurus. Its fossils can be found in Alberta and Montana and come from a period between 77 and 74 million years BCE.

magazine.scienceconnected.org/2017/03/dinosaur-gave-rise-tyrannosaurus-rex/

Probably not accurate AFAIK
Snively et al 2006 See table 1

You can try to compute the Crown Height/Skull Length ratio to see which animals have relatively larger maxillary tooth:
Daspletosaurus: 7.47%
TrA: 8.54%
TrB: 7.03%
TrL: 6.44%

Daspletosaurus's CH is within the range of T-rex's. However, T-rex teeth are still more robust and thicker, mesiodistally (FABL) and labiolingually (MLBL). Also, the measurements in the table are average of several teeth, not sure how the the largest tooth in the jaws of these animals would compare to each other though.

Some of the statements in the link that you posted (Das being more muscular and heavily built than T-rex) are pretty bollocks too

[Verdugo]

Sept 13, 2014 18:06:56 GMT 5 theropod said:

On Carnotaurus sastrei:
Thirdly, their necks:

I know this is old but do know any papers providing in-depth details of the neck musculature of Abelisaurid (Carnotaurus or Majungasaurus)? There are several papers (that i know) describing the cervical vertebrate osteology but they don't explain in details the functional implication of the musculature. I'm looking for a paper on the same level of details as those by Snively. Snively has made several papers on neck musculature of Tyrannosaurid and Allosaurid but i'm not sure if he ever made one for Abelisaurid

[theropod]

Nope, I don't know anything of the sort. Mendez' paper on the comparative cervical osteology is very useful, but there's no detailed myological description on the level of Snively et al.'s neck muscle paper.

[Verdugo]

Nov 11, 2019 4:46:21 GMT 5 theropod said:

Nope, I don't know anything of the sort. Mendez' paper on the comparative cervical osteology is very useful, but there's no detailed myological description on the level of Snively et al.'s neck muscle paper.

Mendez's paper is all good but they do not provide much implication on its myology. Normally, i have to look at the osteological descriptions of the cervical vertebrates in Mendez's, then look again at Snively's to see what those descriptions really mean, function wise. Obviously, having a paper that directly describes the myology in details would have been much more helpful. Also, IIRC, Mendez's does not provide descriptions on the insertion areas of these muscles at the back of the skull so i still think we're missing pieces of the puzzle here. Normally, having details on the insertion sites are very helpful. For instance, if the insertion areas are large and rugose, you can tell that the muscles are probably hypertrophied. Or if the insertion areas are distal from the occipital condyle, we can tell that the muscle leverages are high.

Anyway, i agree with most of your assessments other than this part (yes i know it's old so you probably have change your opinions since but i still have to point that out):

Carnotaurus doesn’t have downturned paroccipital processes to enhance the ventroflexive ability of its head as is the case in Allosaurus (Bakker 1998, Antón et al. 2003, Snively et al. 2007, 2013). Rather its paroccipital processes are directed laterally (Bonaparte 1990) as is the case with basal ceratosaurs. That alone already implies major differences in muscle arrangement between the two (but there’s far more to it than that).

This is correct. However, powerful ventroflexion is still possible in taxa without this adaptation in Allosaurus. Snively 2007 pointed out the developed basitubera in several taxa that could link to powerful ventroflexion:

Sinraptor dongi and Gorgosaurus
libratus (ROM 1247) appear to have ventrally extensive
basitubera, providing high leverage for ventroflexive
muscles. Ceratosaurus has massive basitubera with large
insertions of m. l. cap. prof. and m. r.c.v., indicating that
these muscles were large and effective ventroflexors.

Do we have evidence to fully dismiss the possibility of powerful ventroflexion coming from these muscles (and not m. longissimus capitis superficialis as in Allosaurus) in Carnotaurus? I mean i'm not totally convinced that Carnotaurus's ventroflexion is crap just because it does not have ventrally situated paroccipital processes, there are other muscles that could play a role in ventroflexion too.

EDIT: Also you cited Mendez to suggest that the neck of Carnotaurus is rigid. However, i can't find where Mendez specifically stated so. They did state that the axial skeletons (dorsal, sacral, caudal) are rigid but i can't find where they specifically stated so for the neck (i Ctrl+F for the word 'rigid' and 'stiff'). Perhaps you could provide more insights?  

[creature386]

While this paper is nine years old, it's incredible that we have no post on dromaeosaurid bites so far, despite these animals being there popular here. So, here's at least something:

Weak/fast biters exhibit rostrally displaced tooth rows (high mB) along with posteriorly positioned/oriented muscles (low mM). Their consistently low MA values throughout their tooth rows indicate they were less efficient at delivering forceful crushing bites, but more effective in fast snapping bites. Weak/fast biters are typically small- to medium-sized theropods, with the exception of spinosaurs; fast biting is suitable for piscivory. Dromaeosaurs are here found to be low-efficiency biters, but this does not preclude the possibility that they were ‘big-game hunters’ (Paul 1988, p. 364) because if they did indeed use their sickle claws, then ‘the jaws were secondary weapons’ (Paul 1988, p. 364). Further, weak-biting Varanus komodoensis (Moreno et al. 2008) is capable of inflicting deep wounds through saw-motion biting (Auffenberg 1981), so it is not difficult to imagine dromaeosaurs similarly delivering saw-motion bites if kicks were not enough to kill their prey.

royalsocietypublishing.org/doi/10.1098/rspb.2010.0794

[theropod]

Mendez's paper is all good but they do not provide much implication on its myology. Normally, i have to look at the osteological descriptions of the cervical vertebrates in Mendez's, then look again at Snively's to see what those descriptions really mean, function wise. Obviously, having a paper that directly describes the myology in details would have been much more helpful. Also, IIRC, Mendez's does not provide descriptions on the insertion areas of these muscles at the back of the skull so i still think we're missing pieces of the puzzle here.

Yes, but we have to make the best of what we have.

In the end of the day, osteological description is the basis of any inference about musculature. While we don’t have a rigorous muscle reconstruction for Carnotaurus, because it seems nobody looked at the attachment sites in detail, the cervical osteology does provide some important insights into what it was or wasn’t adapted for.

For example the most prominent feature in the Carnotaurus neck are the hugely enlarged epipophyses. Those are insertion sites of M. transversospinalis cervicis, meaning that muscle (dorsi/lateroflexive) must have had a very large moment arm (we can’t necessarily tell much about the muscle size itself from that, but large moment arms already have functional implications).

Nov 11, 2019 10:27:19 GMT 5 Verdugo said:

Carnotaurus doesn’t have downturned paroccipital processes to enhance the ventroflexive ability of its head as is the case in Allosaurus (Bakker 1998, Antón et al. 2003, Snively et al. 2007, 2013). Rather its paroccipital processes are directed laterally (Bonaparte 1990) as is the case with basal ceratosaurs. That alone already implies major differences in muscle arrangement between the two (but there’s far more to it than that).

This is correct. However, powerful ventroflexion is still possible in taxa without this adaptation in Allosaurus. Snively 2007 pointed out the developed basitubera in several taxa that could link to powerful ventroflexion:

Sinraptor dongi and Gorgosaurus
libratus (ROM 1247) appear to have ventrally extensive
basitubera, providing high leverage for ventroflexive
muscles. Ceratosaurus has massive basitubera with large
insertions of m. l. cap. prof. and m. r.c.v., indicating that
these muscles were large and effective ventroflexors.

Do we have evidence to fully dismiss the possibility of powerful ventroflexion coming from these muscles (and not m. longissimus capitis superficialis as in Allosaurus) in Carnotaurus? I mean i'm not totally convinced that Carnotaurus's ventroflexion is crap just because it does not have ventrally situated paroccipital processes, there are other muscles that could play a role in ventroflexion too.

This is a question of specialization for ventroflexor-driven biting, or "hatchet-biting", which has been proposed (but never substantiated) for Carnotaurus. I don’t think the burden of proof rests on me here, it rests on the people postulating some kind of "hatchet bite" analogous to Allosaurus for Carnotaurus, but somehow they never seem to bring evidence for that claim. I don’t need to provide evidence that there wasn’t any powerful ventroflexive musculature in Carnotaurus–there may well be, as you pointed out there are powerful ventroflexors in many theropods (Snively & Russell 2007). Others should provide evidence that Carnotaurus was specialized for ventroflexion in excess of the ordinary for theropods. I’ve already done enough by demonstrating that from what evidence is available, this seems unlikely. So as things are, I find this hypothesis unlikely, baseless even.

The baseline here is Allosaurus, the taxon for which there is the most solid evidence for ventroflexive augmentation of the bite (as several studies have outlined, e.g. Snively et al. 2013, Rayfield et al. 2001 and Bakker 1998).  But I think if someone wants to establish some sort of biting mode, they should bring the evidence to support it, as many have done e.g. in the case of Allosaurus. Deflection of the paroccipital processes adds two more muscles with large ventroflexive moment arms in this taxon, the M. iliocostalis longus and M. longissimus capitis superficialis. Exact muscle sizes are of course always highly speculative, but if we follow Snively et al.’s (2013) reconstruction, then M. long. cap. sup. is the largest ventroflexive muscle in Allosaurus and contributes over 40% of the summed muscle forces of the M. longissimus and rectus capitis. This would only increase even more if we added the M. iliocostalis, also inserting on the paroccipital process, which Snively et al. didn’t model. It has this in addition to the "normal" theropod ventroflexors, the M. rectus capitis and M. l. cap. profundus, not instead of them.

So if we want to propose a taxon had a similar biting mechanism driven by ventroflexors, we should be able to point out at least some parallels with Allosaurus, at least some sort of hint for particularly large ventroflexors and/or moment arms, don’t you think?

EDIT: Also you cited Mendez to suggest that the neck of Carnotaurus is rigid. However, i can't find where Mendez specifically stated so. They did state that the axial skeletons (dorsal, sacral, caudal) are rigid but i can't find where they specifically stated so for the neck (i Ctrl+F for the word 'rigid' and 'stiff'). Perhaps you could provide more insights? 

I seem to recall Méndez 2014a stating that the entire axial skeleton of Carnotaurus is relatively stiff, not just the dorsal, sacral and caudal collumn. In fact, this is stated in the abstract, and again in the conclusion, and also in the discussion of Méndez 2014b.

In the neck, for one it is the high robusticity, and the tall epipophyses, that would likely reduce the range of motion. On the other hand, once again we are contrasting this Allosaurus, which is noted as having a particularly flexible neck (Snively et al. 2013), and has numerous adaptions for this (stronger opisthocoely, long, low neural spines).

Bakker, R.T. 1998. Brontosaur killers: Late Jurassic allosaurids as sabre-tooth cat analogues. Gaia 15: 145–158.

Méndez, A.H. 2014a. The caudal vertebral series in abelisaurid dinosaurs. Acta Palaeontologica Polonica 59 (1): 99–108.
Méndez, A.H. 2014b. The cervical vertebrae of the Late Cretaceous abelisaurid dinosaur Carnotaurus sastrei. Acta Palaeontologica Polonica 59 (3): 569–580.

Rayfield, E.J., Norman, D.B., Horner, C.C., Horner, J.R., Smith, P.M., Thomason, J.J. and Upchurch, P. 2001. Cranial design and function in a large theropod dinosaur. Nature 409 (6823): 1033.

Snively, E. and Russell, A.P. 2007. Functional variation of neck muscles and their relation to feeding style in Tyrannosauridae and other large theropod dinosaurs. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology: Advances in Integrative Anatomy and Evolutionary Biology 290 (8): 934–957.
Snively, E., Cotton, J.R., Ridgely, R. and Witmer, L.M. 2013. Multibody dynamics model of head and neck function in Allosaurus (Dinosauria, Theropoda). Palaeontologia Electronica 16 (2): 1–29.

[creature386]

My post on the dentition of Purussaurus brasiliensis:

lack of serrations in the carinae distinguishes the teeth of this taxon from the marked pseudoziphodont serrations seen in Purussaurus (see Aureliano et al., 2015; Souza et al., 2016).

www.researchgate.net/publication/330734002_A_new_caimanine_Crocodylia_Alligatoroidea_species_from_the_Solimoes_Formation_of_Brazil_and_the_phylogeny_of_Caimaninae
Pseudoziphodont means that they have similarities with the type of teeth carcharodontosaurids or varanids possess, but aren't really the same.
A bit more detail:

The teeth of Purussaurus sp. are subcircular at their base, slightly flattened at the crown, and bear pseudoziphodont ridges (sensu [55]). A gradual transition can also be seen from taller and acutely pointed anterior teeth to broader and lower posterior ones, which are more button-shaped (heterodont in shape and size). The teeth of P. neivensis have been described as curving backwards and slightly inwards [56]. Isolated teeth attributed to P. brasiliensis [19] show the same characteristics (see Fig. 5). This tooth morphology is ideal for piercing and smashing [57] and indicates a high resistance to bending forces and breakage (potentially against hard materials such as bone). On the other hand, the false ziphodont carinae, analogous to the true ziphodont morphology, assisted the teeth in puncturing and drawing through flesh [58]. All this suggests that Purussaurus were indeed predators of vertebrates. Due to the possession of stouter teeth, Purussaurus exhibited a selection towards maximizing tooth strength, also allowing in niche separation.

journals.plos.org/plosone/article?id=10.1371/journal.pone.0117944

[Infinity Blade]

Here's some information about the neck of Machairodus aphanistus and its functional role in killing prey.

The study of cervical anatomy in the Miocene machairodontine felid Machairodus aphanistus reveals the early stages of evolution of the sabre-toothed adaptations in the homotherin lineage. The cervical vertebrae of M. aphanistus show a surprising mosaic of features, combining a more primitive atlas than its derived relative Homotherium, with a set of elongated, caudal cervical vertebrae that display well-developed transverse processes with complex and strong muscle insertion areas. In spite of its primitive morphology, the atlas of M. aphanistus does show a slight caudal projection of the atlas wings, indicating an emphasis on vertical motions of the cranial portion of the neck and skull. The rest of the cervical vertebrae of M. aphanistus show clear adaptations for strength, flexibility and precise control of neck motions compatible with the canine shear-bite model and comparable to those of Homotherium. Such a powerful and flexible neck could provide additional stability to partly compensate for the risk of canine breakage created by the less specialized adaptations of the skull and cranial cervical vertebrae for the machairodontine bite.

academic.oup.com/zoolinnean/article-abstract/188/1/319/5581941?redirectedFrom=fulltext

[Infinity Blade]

I'm sure I've posted this study elsewhere, but this is the study documenting bite marks on a hadrosaur caudal by a juvenile Tyrannosaurus, demonstrating that even late-stage juveniles were capable of puncturing bone, despite their lack of osteophagous adaptations compared to the adults (Peterson & Daus, 2019).

The real reason I made this post was that, although Figure 9 of the study illustrates how big the jaws and bitten bone are relative to each other, I wanted to show an image including a human for scale.


www.eurekalert.org/pub_releases/2019-03/uowo-ttr031119.php

Pretty decently sized bone, both relative to the jaws and to us humans, that appears to have been solid (looking at the figures in the paper). And yet bitten through by a bladed toothed juvenile T. rex with a relatively elongated skull.

[Infinity Blade]

People here might remember reading the following claim. This is from our own Tyrannosaurus profile.

Scientists believe this powerful predator could eat up to 500 pounds (230 kilograms) of meat in one bite.

Read more: theworldofanimals.proboards.com/thread/14/tyrannosaurus-rex?page=1#ixzz6AvujiCmG

I've looked around the Internet for the original source or measurement for this claim, but I have not been able to find out a whole lot (someone told me the oldest sources claiming such were Enchanted Learning and High Point University).

Just this morning I took the liberty of asking Dr. Thomas R. Holtz Jr. to see if he knew better (and what he thought of the claim). This is what we said in our brief exchange.



So he himself wasn't sure either. However, he did not find the value to be unreasonable.

One of our former users (SpinoInWonderland) actually went out of their way to create a visual for me.


^This is a Tyrannosaurus skull next to a hypothetical 230 kg sphere of flesh. The tyrannosaur's gape is at 25^o, which is close to the optimal gape of 28^o (Lautenschlager, 2015).


^This is the skull with its mouth open at 63.5^o (Lautenschlager, 2015).

The 230 kg sphere of flesh is ~76 cm in diameter, for the record. We can verify that these are indeed the dimensions of a hypothetical sphere of flesh 230 kg in mass by using a couple formulas. By using the formula for a sphere's volume (4/3π*r³), we get 229,847.2961 cm³. The density of flesh is close to 1 kg/L, which is equivalent to 0.001 kg/cm³. Multiplying the volume in cubic centimeters by 0.001 kg/cm³ gives us a mass that's ~230 kg (~229.847 kg to be more precise).

While a Tyrannosaurus would usually not be ripping off this much meat in one go (given how optimal gape angles are from 28-32^o from the reference cited earlier), it's clear that it could fit 230 kg of flesh in its mouth, and therefore bite off that much flesh in one bite. Keep in mind too that 1.) the bolus of flesh obviously wouldn't be a sphere, but would be much flatter in shape as it is pressed down and bitten off the prey item/carcass by T. rex, and 2.) gape angle estimations actually go up to 80^o for Tyrannosaurus.

References:

Lautenschlager, S. (2015). Estimating cranial musculoskeletal constraints in theropod dinosaurs. Royal Society Open Science, 2(11), 150495.

[Infinity Blade]

Proposed functions for Istiodactylus teeth and even claws for feeding. Basically, these could include taking large chunks of flesh from much larger animals (e.g. dinosaurs, crocodiles, or fish) akin to a cookiecutter shark, scavenging (since it does not have the skull reinforcements necessary for struggling with large prey), and using the well-developed manus claws to manipulate carcasses.

www.sciencedirect.com/science/article/pii/S0195667113001699?via%3Dihub

[Infinity Blade]

I've recently discovered a paper about the biomechanics of ornithosuchid jaws.

www.researchgate.net/publication/323927440_Rediscovered_Cranial_Material_of_Venaticosuchus_rusconii_Enables_the_First_Jaw_Biomechanics_in_Ornithosuchidae_Archosauria_Pseudosuchia

These authors find that Venaticosuchus would have had a strong, but slow bite (Venaticosuchus would apparently have had a relatively stronger bite than other ornithosuchids, Alligator, and aetosaurs). They suggest that this, along with supposed structural weak points in the laterally compressed snout and teeth, would have relegated ornithosuchids to scavenging niches, not as apex predators.

I strongly disagree with this assessment, especially if by scavenger they truly mean "obligate scavenger".

1.) It is once again important to point out that obligate vertebrate scavengers tend to be, and pretty much have to be, large soaring fliers (e.g. vultures); needless to say, ornithosuchids do not fit this description. That alone refutes the scavenger hypothesis for ornithosuchids.

2.) Interestingly, this is also the first time I've ever seen a strong yet slow bite being seen as an issue for the purposes of predation. If I remember correctly, there is a trade-off between bite speed and strength. Ornithosuchids may have had a slow bite that may not have been well-suited for catching small, fast, and agile prey, but I can't imagine it being much of an issue against slower, larger prey. In absolute terms, how slow could its bite have possibly been?

3.) They point out a weak spot in the laterally compressed snout. I'm not sure what that weak spot is, having looked at the citation they provide for this and not finding anything of note (okay, I didn't flat out read that full paper, but I did use "weak" as a key word for a quick search, and got no results). Wikipedia claims it's the diastema, but I was unable to find where the paper claims this. If it's just the laterally compressed shape of the rostrum, it doesn't mean the snout was too weak to handle live prey, it just means it did not use (or at least wasn't as specialized for using) the same feeding or dismembering habits as say, in modern crocodylians. They also claim the laterally compressed shape of the teeth to not be suited for struggling with live prey, but again, that just means they're not the most structurally suited for mediolateral loads. The teeth of modern Komodo dragons, the upper canines of machairodonts, and the teeth of several extinct reptiles (e.g. lots of Mesozoic carnivorous dinosaurs) were like this, and no one claims them to be scavengers. The authors provide an alternative suggestion that ornithosuchids may have grabbed small to medium-sized prey with their forelimbs to resist lateral stresses, although they also point out that the bipedal abilities of ornithosuchids need testing.

4.) At the very end of their paper (the conclusion) the authors suggest ornithosuchids like Venaticosuchus were more likely to have been scavengers or hunting small prey that did not exceed them in size. This latter part runs completely counter to their suggestion that the bite was too slow to effectively catch prey, even more so small, faster, and more agile prey.

Overall, I see no reason to suppose ornithosuchids did not hunt their own prey like all other terrestrial vertebrate carnivores. A lot of the features of the skull and teeth that have been said to limit their capacity to catch and handle live prey instead seem like adaptations for a specific method of killing and dismemberment seen in some other predatory reptiles, most notably carnivorous dinosaurs (what with the laterally compressed and evidently deep snout and the slicing ziphodont teeth). The authors even point out the possibility of the use of the forelimbs for prey handling, which, if true, could further solidify the carnivorous theropod comparison.

[Infinity Blade]

Apparently a rigid lower jaw in tyrannosaurids has been suggested since 2000.

sci-hub.tw/10.1671/0272-4634(2000)020[0619:TCBOT]2.0.CO;2

[Infinity Blade]

Apparently this is how the cross sections of a grey wolf compare to that of a leopard, particularly at the base (i.e. the dentino-enamel junction).


Original source->

The functional reason for this:

Wolves use their canines to slash at the hide and muscle of prey, producing lacerations and extensive bleeding. This use contrasts with that of felids, which use their canines to stab and hold struggling prey. These different uses of the canines are reflected in their configuration in the two types of carnivores. The circular cross section of felid teeth, for example, reflects the unpredictable direction of stresses on teeth deeply imbedded in the flesh of prey. In contrast, the elliptical cross section of wolf canines suggests adaptation to loads primarily applied along the long axis of the ellipse, front to rear, as when a wolf is pulled along by running prey (fig. 4.4).

source->

In other words, canid vs felid canines are analogous to carnosaur vs tyrannosaurid teeth. The major difference being that the theropod teeth are much more specialized for slicing than their carnivoran counterparts (on account of their serrated bicarinae), and that, unlike felids, the incrassate teeth of tyrannosaurids are also an adaptation for osteophagy.

It should be noted that this only holds true for their modern representatives. Saber-tooths, of course, had mediolaterally compressed upper canines, and borophagines and the dire wolf had rounder canines more like those of modern felids and hyaenids (suddenly the dire wolf's reclassification into its own genus makes more sense).