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Post by theropod on Oct 10, 2019 2:34:51 GMT 5
Err the arguably most successful radiation of animals with ziphodont dentitions ever to exist had long and narrow jaws, and presumably used them routinely and quite effectively for slicing into "large, flat surfaces", by which I suppose you mean the body of a large animal.
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Post by dinosauria101 on Oct 10, 2019 2:40:58 GMT 5
The serrations are a good point. But still, as a whole, the long and narrow jaw simply isn't a good mechanical solution for slicing into a large flat surface..serrated teeth ain't gonna change that fact. They would certainly help in cutting a fish in half though. Well, like theropod said, that seems to be the NORM for slicers. You don't need a high bite force for efficient slicing.
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Post by theropod on Oct 10, 2019 3:08:52 GMT 5
^Pliosaurs had a high bite force. They also weren’t "slicers" or even ziphodont in a manner comparable to the taxa I was referring to. Pliosaur teeth vary quite a bit depending on the taxon. Some are conical like crocodile teeth (Kronosaurus), some are more banana-shaped and have carinated edges similar to T. rex teeth (Pliosaurus), and some are in between (Liopleurodon). Some would be more croc-like, but others would probably have had more of a bone-crushing shearing bite similar to Tyrannosaurus.
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Post by sam1 on Oct 10, 2019 3:34:48 GMT 5
Err the arguably most successful radiation of animals with ziphodont dentitions ever to exist had long and narrow jaws, and presumably used them routinely and quite effectively for slicing into "large, flat surfaces", by which I suppose you mean the body of a large animal. We're really side tracking here at this point, but this proclamation of yours doesn't change the physics and mechanics of a bite. It doesn't change the fact that a long and narrow jaw of a smaller animal is a poor tool for trying to bite big chunks off a bigger animal..like, a huge, round, fat body of a whale kind of bigger. Do I need to explain the gape, and bite surface and force distribution problems? It's not something to argue over. And I suggest you stop pulling things out of context.
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Post by theropod on Oct 10, 2019 4:02:59 GMT 5
No, it does not, exactly. A narrow jaw can effectively focus bite or impact force on a small area, potentially helpful for deep biting. It also brings the direction of the tooth rows more in line with any backwards pulling force, which would make the pull (which is how ziphodont teeth cut) more efficient.
What is it with this fascination everyone has with biting off "big chunks" of other animals?
It’s not the size of the chunk of muscle you are missing that kills you, it is the blood loss. Blood loss depends on the length and depth of the wound margins (the part that is actually sliced, proportional the the number and size of blood vessels it can expect to sever), not the area or volume in between them.
Maybe you should, as I am obviously missing your point entirely.
How am I pulling things out of context by noting that the morphology you claim is poorly suited for something is precisely the morphology the most long-lived, widespread and successful radiation of predators doing that thing had developed?
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Post by sam1 on Oct 10, 2019 12:12:49 GMT 5
My point goes back to the premise about sharks not needing to be bigger(longer) than whales in order to kill them, whereas pliosaurs would need be. A 13m megalodon could relatively easily kill a 15m whale..a 13m pliosaur, probably not. Even at parity lengths, a pliosaur would be too small, its gape wouldn't be sufficient and jaw structure wouldn't be strong enough to effectively deliver on the critical parts of the trashing whale body. Also, note that such bite indeed needs to be extremely voluminous because of the whale's thick layers of blubber and skin. So yeah, a pliosaur simply doesn't have an appropriate "feeding apparata".
That said, I need to put a disclaimer though..bitting on the tail root region could maybe work. It just depends if the pliosaur can withstand and resist the trashing force of a much larger animal.
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Post by Infinity Blade on Oct 10, 2019 17:29:04 GMT 5
The first thing I need to ask, before I ask what this assertion is based off of, is how massive a 13m pliosaur is compared to a 15m whale? This can be answered by literally anyone here.
Doesn't this have more to do with penetrative ability (which with large, pointed, sometimes serrated teeth and a very powerful bite I think a macropredatory pliosaur would have a lot of)?
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Post by theropod on Oct 10, 2019 17:49:58 GMT 5
A 13 m pliosaur would be around 20 t.
The whale’s mass depends a lot on the species we are talking about, based on regressions in Lockyer 1976:
Eubalaena glacialis: 49 t
Eschrichtius robustus: 37 t
Balaenoptera musculus: 20 t
Balaenoptera physalus: 22 t
Balaenoptera borealis: 17 t
Balaenoptera brydei: 20 t
Megaptera novaeangliae: 47 t
Physeter macrocephalus: 33 t
Note that these are not accounting for fluid loss during weighing. Lockyer suggests that figures for mysticetes represent 94% of actual live weight, the one for the sperm whale 90% (Lockyer later published two modified formulae for sperm whales that account for this in 81 and 91, which give 36.5 and 36.4 t respectively at 15m, but use rather different exponents of 2.74 and 3.18). Also note that the exponents and slopes on the regressions vary quite a bit, so the weights predicted at 15 m aren’t necessarily indicative of their relative weights at typical adult sizes (as for a blue or fin whale, a 15 m specimen isn’t an adult).
Lockyer, C. 1976. Body weights of some species of large whales. ICES Journal of Marine Science 36 (3): 259–273. Lockyer, C. 1981. Estimates of growth and energy budget for the sperm whale, Physeter catodon. FAO Fisheries Series (FAO). Lockyer, C. 1991. Body composition of the sperm whale, Physeter catodon, with special reference to the possible functions of fat depots. Rit Fiskideilda 12 (2): 1–24.
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Post by theropod on Oct 10, 2019 18:09:26 GMT 5
Yet there are pliosaur bite marks suggesting likely predation on Leedichthys. These are bites inflicted on fins, which would make scavenging unlikely since there is very little nutritional value in actinopterygian fins, and at any rate the description of the bite marks don’t appear consistent with a defleshing pattern.
Presumably the attacker was a large pliosaur, but since no confirmed real pliosaurs 13 m in length exist (even if not totally impossible) and since most Leedsichthys specimens are in the 5 - 20 ton range, the fish was likely at least the size of the attacking pliosaur, if not larger.
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Post by sam1 on Oct 10, 2019 23:52:40 GMT 5
The first thing I need to ask, before I ask what this assertion is based off of, is how massive a 13m pliosaur is compared to a 15m whale? This can be answered by literally anyone here. Doesn't this have more to do with penetrative ability (which with large, pointed, sometimes serrated teeth and a very powerful bite I think a macropredatory pliosaur would a lot of)? I'll answer tomorrow, don't have the time now.
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Post by sam1 on Oct 11, 2019 0:00:40 GMT 5
Yet there are pliosaur bite marks suggesting likely predation on Leedichthys. These are bites inflicted on fins, which would make scavenging unlikely since there is very little nutritional value in actinopterygian fins, and at any rate the description of the bite marks don’t appear consistent with a defleshing pattern. Presumably the attacker was a large pliosaur, but since no confirmed real pliosaurs 13 m in length exist (even if not totally impossible) and since most Leedsichthys specimens are in the 5 - 20 ton range, the fish was likely at least the size of the attacking pliosaur, if not larger. I've read about that, and it's just not enough for anything conclusive. For all we know it could've been a pliosaur feeding on a dying, sick, or wounded leedsichtys. That said, I don't think the defensive properties of that fish are a good comparison to those of a baleen whale.
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Post by theropod on Oct 11, 2019 4:53:12 GMT 5
Why is that?
And of course large prey items are dying, sick, or injured. But that doesn’t actually make them physically easier to bite. Yet, bite marks on the fins clearly demonstrate one possible way how a pliosaur might be able to debilitate a larger prey item.
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Post by sam1 on Oct 11, 2019 13:43:23 GMT 5
..because the whale has a thick layer of fat and skin, for one thing. Causing a critical blood loss would be a tall order if the bite is not deep and voluminous enough.
Now to answer to Infinity blade.. as you surely know, a long, narrow jaw produces only a fraction of the total bite force at the tip of the jaw. So if the targeted surface is large and round enough, such jaw can clasp it only partially and a bite would be more like a wide pinch. That said, we need a visual representation of a say, averagely bulky 13-15m whale species body and a 10-12m pliosaur jaw to support or debunk the premise.
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Post by dinosauria101 on Oct 11, 2019 16:02:01 GMT 5
Well, at the beginning, I thought a whale would be hard to bite like that due to rotund shape (except areas, like tail, fins, etc)
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Post by Infinity Blade on Oct 11, 2019 16:53:49 GMT 5
So basically your point is just that it doesn't produce enough bite force at the tip of the jaw because of the long, narrow shape thereof? Yes, that's true...except that a pliosaur would still bite very hard at the tip of the jaw. Dry skull estimates, which I believe we've established as substantial underestimates of absolute bite force in life, for Kronosaurus suggest forces of ~1.5t at the front of the jaw. And not only do these, again, greatly underestimate absolute bite force, but the hypothetical 13m pliosaur you alluded to earlier would bite far harder than that at the tip of its own jaw. There's also the teeth somewhat further back (i.e. the caniniforms, which are either in the front or somewhat midway->), which of course exert more force. If a pliosaur can properly clasp a large whale in its jaws and bite it (and I think it could), it wouldn't be something I would merely describe as a "wide pinch". I agree a visual comparison would be nice.
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