Nobody claimed such a similarity existed, so not sure whom you expect to bring a source for it. You can misrepresent what you disagree with all you like, but that does nothing to shift the burden of proof–all it does is prevent a constructive discussion.
These animals have extremely different teeth, because they have extremely different jaws, which they move in an extremely different way. I’m not trying to pull some sort of morphological resemblance out of thin air here, because there is none. What there is is a functional resemblance, and that’s completely consistent with the officially suggested function of their jaw apparata.
(my) Working hypothesis: Megatooth shark teeth functionally similar to Carnosauria. (working in this case as in "being worked on", but also as in "It works!"–simply because it does and you don’t appear inclined to actually refute it)
(your) Alternative hypothesis: Megatooth shark teeth functionally similar to those of
T. rex.
Lines of evidence:•Tooth marks of megatooth sharks and carnosaurs show a qualitatively similar bite mechanism. Their tooth marks consist of ghashes that were the result of mesiodistal movements of the jaws during attack or feeding.
T. rex’ record on the other hand shows an aptitude for deep puncturing and shearing off proportionately large bones (e.g. Happ 2008).
You have not even attempted to demonstrate any notable quantitative differences in terms of prey-bone modification between
Carcharocles and carnosaurs (this greater aptitude at biting bone in the shark’s case that you like to allude to, for all we know an artifact of the fact that most of this shark’s recorded prey items were much smaller than itself and thus had relatively smaller bones, while carnosaur bite marks are mostly known from the bones of animals several times their size…).
However, with
T. rex we already know marked qualitative and quantitative differences, which get all the more pronounced when looking at functional morphology. There do not appear to be any genuine exclusive puncture marks attributable to
C. megalodon at all, despite the considerably better fossil record of its biting traces as compared to theropods (as we already confirmed, that wonderful display you tried to sell us of a
Carcharocles tooth embedded in the articular surface of a whale centrum is a fake, as are others like it). So that already rules out the whole functional similarity thing. If you think
Carcharocles was an excellent bone slicer while carnosaurs weren’t–well, think that, but you’ll have to understand if I don’t just because your feeling tells you that.
Speaking of allosaurian prey-bone modification, there are some rather impressive examples on top of those I already posted (such as bone fragments making up 50% of a giant
Allosaurus coprolithe–so much for the fragile-toothed animal that avoided biting bone at all costs, or
Brink et al.’s recent work→ on the particularly tough microstructure of theropod serrations:
antediluviansalad.blogspot.de/2015/08/allosaurus-more-of-vulture-than-falcon.html• Likewise, while their tooth shapes are very different and will also experience mechanical failure differently, there are definite cutting adaptions in
Carcharocles teeth and the teeth of carnosaurian theropods (Broad, flat tooth shape=low CBR, sharp cutting edges). This just isn’t the case in
T. rex, whose teeth are ~70% as thick as they are wide (Smith et al. 2005) and have blunt edges (Abler 1992).
Carcharocles and carnosaur crowns appear to heavily overlap in terms of relative thickness at a given length (e.g. cf. Bakker 1998, Canale et al. 2015 and Bendix-Almgreen 1983), so most likely the shark’s CBR is in slicer-morphospace too.
You can certainly find carnosaur teeth that match the robusticity of even particularly robust meg teeth (e.g.
link→,
link→,
link→,
link→), just as you can find less robust examples of both.
Megalodon and carnosaur teeth are knifes or sawblades, tyrannosaurus teeth are "pegs with poor cutting ability" (Barrett & Rayfield 2006). There’s an obvious functional difference here, based on these two points and also, pre-eminently, the next one.
• As even you acknowledged, there is an additional difference pertaining to the way their teeth are anchored. Even if
C. megalodon teeth themselves had crowns just as robust (and accordingly blunt, which I’m sure is not a suggestion you’d agree with, seeing how it’d be a clear disadvantage) as those of
T. rex, they would not be capable of performing the kind of bone modification dedicated durophages do without dislodging, irrespective even of their crown robusticity. That is in fact why there are so many teeth known, they fell out easily. Carnosaurs are more similar here too, their teeth have much less pronounced roots. That being said Carnosaur teeth were probably more prone to being broken than to being dislodged, because their teeth are still thecodont and embedded in bone with half their length, unlike lamniform teeth. But I’m sure we can agree that whether a tooth fractures or dislodges first is all the same for our intends and purposes.
Alternative hypothesis decisively rejected, working hypothesis corroborrated (admittedly mostly by the same data that lead to it in the first place, but that’s the consequence of only making a hypothesis based on all the available data in the first place. With luck at some point you or I will have the means to verify this further).
My opinion stands unless evidence to the contrary is presented.
As always, feel free to present it, just don’t expect me to believe you as long as it seems you are just trying to make is look as if megalodon’s teeth somehow combined all the strengths and none of the weaknesses of various dental morphologies without even bothering with real, quantifiable evidence.
–––References/Further reading:Abler, William L. (1992): The serrated teeth of tyrannosaurid dinosaurs, and biting structures in other animals. Paleobiology, 18 (2), pp. 161-183.
Bakker, Robert T. (1998): Brontosaur killers: Late Jurassic allosaurids as sabre-tooth cat analogues. Gaia, 15 pp. 145-158.
Barret, Paul M.; Rayfield, Emily J. (2006): Ecological and evolutionary implications of dinosaur feeding behaviour. TRENDS in Ecology and Evolution, 21 (4), pp. 217-224.
Bendix-Almgreen, Svend E. (1983): Carcharodon megalodon from the Upper Miocene of Denmark, with comments on elasmobranch tooth enameloid: coronoïn. Bulletin of the geological Society of Denmark, 32 pp. 1-32.
Canale, Juan I.; Novas, Fernando E.; Pol, Diego (2015): Osteology and phylogenetic relationships of Tyrannotitan chubutensis Novas, de Valais, Vickers-Rich and Rich, 2005 (Theropoda: Carcharodontosauridae) from the Lower Cretaceous of Patagonia, Argentina. Historical Biology: An International Journal of Paleobiology, 27 (1), pp. 1-32.
Happ, John (2008): An Analysis of Predator-Prey Behaviour in a Head-to-Head Encouter between Tyrannosaurus rex and Triceratops. In: Larson, Peter; Carpenter, Kenneth: Tyrannosaurus rex the Tyrant King. Bloomington, pp. 355-368.
Smith, Joshua B.; Vann, David R.; Dodson, Peter (2005): Dental Morphology and Variation in Theropod Dinosaurs: Implications for the Taxonomic Identification of Isolated Teeth. The Anatomical Record, 285 (A), pp. 699-736.
(Enough citations for you? Granted, they’re not citations for what you asked for, but if all you ever ask for is for me to bring proof for something I never claimed, you’ll have to wait a long time until you get it.)
