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Post by spartan on Dec 7, 2019 1:56:36 GMT 5
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Post by Grey on Dec 7, 2019 1:59:49 GMT 5
I think the size was reported doubtful for some reasons, including a possible error because the corresponding thickness was remarkably short for such a diameter.
I'm more interested by the specimen you alluded in a sensitive thread and the 2018 English giants. At least they are actually real.
But looking at the various reconstructions of S. sikanniensis, the skull region really doesn't seem to have been massive, absolutely not comparable to a pliosaur or a sperm whale.
Regarding the pliosaurs skull width, it depends which pliosaur genus and if the geological pressures didn't compress and increase (or decrease for that matter) the skulls. Sachicasaurus is impressively wide but that doesn't seem to be comparable in the large Kronosaurus or P. kevani. But that us not the problem.
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Post by theropod on Dec 7, 2019 2:48:31 GMT 5
Geological pressures don’t work like that. Bone dimensions don’t increase noticeably as a result of compaction, they decrease.
You have to keep in mind that there is sediment all around the bone, not just on top of it. All of it is under the same pressure. If the entire sediment, including the bone, gets compacted, there’s nowhere for the bone to expand to, so it gets flattened along one axis (up to the point where it isn’t compressible any further), but it cannot expand to the sides to accomodate. That’s why you often find bones that are less compacted than the matrix they are in, even if still heavily compacted.
If a skull is 1 m wide originally, comes to lie on its dorsal or ventral side during burial (as is most likely for pliosaurs), and then gets compacted, it will still be 1 m wide afterwards.
The only way diagenetic pressure could conceivably increase a measurement by a significant margin would be if something that isn’t actually the measurement you are looking for gets "squished" into the same plane and you erraneously include it, e.g. if you had a vertebra that was pressed flat at a 45° angle, of course your "length" measurement when just taking the maximum anteroposterior dimension will actually include part of the width, not just the length.
But with pliosaur skulls being quite flat, that isn’t much of a danger. By far their largest posterior measurement is the transverse width, so again an oblique compaction vector would not be able to increase the measurement, unless it was from an anteroposterior angle (and neither P. kevani nor Sachicasaurus seem to show the pronounced assymetry you get if you have compaction along an oblique axis to begin with).
More delicate structures also might experience some sort of rotation under the load at an earlier stage (since bone is not totally rigid), before the sediment itself gets compacted, e.g. ceratopsian frills can get flattened to be in line with the rest of the skulls when they should be inclined rostrally (I’ve heard Don Henderson describe the process they used to retrodeform them), but again, this is not applicable to pliosaurs.
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Post by kekistani on Dec 7, 2019 10:12:16 GMT 5
If they are head on their spotted if they are spotted it will be difficult for them to escape the Shastasaurus. Like you said Shastasaurus was slender for it’s size. And when the dreaded toothless marine reptile catches the giant macropredatory shark, what is it going to do? Ram it and break its skull open?
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denis
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Post by denis on Dec 8, 2019 19:19:52 GMT 5
If they are head on their spotted if they are spotted it will be difficult for them to escape the Shastasaurus. Like you said Shastasaurus was slender for it’s size. And when the dreaded toothless marine reptile catches the giant macropredatory shark, what is it going to do? Ram it and break its skull open? What’s the evidence of Megalodon hunting whales larger than it? Exactly, no evidence. Those bite marks likely mean it scavenged from their remains.
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Post by Grey on Dec 8, 2019 22:28:18 GMT 5
And when the dreaded toothless marine reptile catches the giant macropredatory shark, what is it going to do? Ram it and break its skull open? What’s the evidence of Megalodon hunting whales larger than it? Exactly, no evidence. Those bite marks likely mean it scavenged from their remains. Megalodon hunted multi-tons whales. Neogene cetotherids were up to 13 m. A whale that length would weigh 20-25 tonnes. There are bite marks on cetotherids up to 9 m, 9 tons. That means megalodon regularly preyed on T. rex sized prey items. Shastasaurus preyed on flimsy squids and fishes weighing a few kg at most. There is evidence of a Pliocene predation attempt of a 7 m shark (possibly young meg) on a humpback-sized balaenopterid (Kallal. 2010) with a evidence of a severe bite if not lethal. Also, megalodons were used to fight the most fearsome foe of all, their conspecifics. There is evidence of white sharks attacking right whales calves being on average as heavy or heavier than adult white sharks. There are indications of megalodon having adaptations to kill massive preys such thick, heavy rooted teeth. Compression fractures at the tip of some teeth are unique among sharks and indicate devastating bite force. A medium-size 25-30 tonnes megalodon could potentially slaughter S. sikanniensis. A full bite in the torso would be enough. The ichthyosaur can't do nothing if not trashing its tail and flee. Even a 10 m megalodon would be a potentially lethal foe for S. sikanniensis.
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Post by kekistani on Dec 9, 2019 4:38:20 GMT 5
And when the dreaded toothless marine reptile catches the giant macropredatory shark, what is it going to do? Ram it and break its skull open? What’s the evidence of Megalodon hunting whales larger than it? Exactly, no evidence. Those bite marks likely mean it scavenged from their remains. It doesn't matter if or if not Megalodon hunted prey larger than itself (and those bites are in oddly specific areas for it to just be scavenging). Megalodon can kill Shastasarus easily, Shastasaurus can't.
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Deleted
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Post by Deleted on Dec 9, 2019 4:44:46 GMT 5
Question?
Do great white sharks kill mature male elephant seals that aren't otherwise incacipated. I read that great whites avoid doing so because the elephant seal can turn its body and bite the shark which can cause life-ending injuries.
Correct me if I'm wrong, but great white sharks usually stick to much smaller prey unlike terrestrial mammalian carnivores
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Post by kekistani on Dec 9, 2019 5:28:24 GMT 5
Question? Do great white sharks kill mature male elephant seals that aren't otherwise incacipated. I read that great whites avoid doing so because the elephant seal can turn its body and bite the shark which can cause life-ending injuries. Correct me if I'm wrong, but great white sharks usually stick to much smaller prey unlike terrestrial mammalian carnivores They do try, at least
even elephant seal cows outweigh the average white shark and they end up on the menu on some occasions
point being that the GWS can attack and kill prey of a similar if not larger size, and Meg outweighs its opponent here
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Deleted
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Post by Deleted on Dec 9, 2019 6:25:10 GMT 5
I'll admit i know nothing about elephant seals, in fact, I thought they were smaller than white sharks but it seems what female elephant seals are in the same size range as female sharks. Was that seal a male or female.?
Anyway, I would look to interactions between false killer whale/pilot whales as they are slightly larger than female great whites, but a freak 3000-4000 pounder should be able to take one.
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Post by Ceratodromeus on Dec 9, 2019 6:26:09 GMT 5
And when the dreaded toothless marine reptile catches the giant macropredatory shark, what is it going to do? Ram it and break its skull open? What’s the evidence of Megalodon hunting whales larger than it? Exactly, no evidence. Those bite marks likely mean it scavenged from their remains. What evidence is there Shastasaurus hunted something even remotely comparable to its size? Exactly, no evidence. We can use this logic too.
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Post by kekistani on Dec 9, 2019 6:30:37 GMT 5
I'll admit i know nothing about elephant seals, in fact, I thought they were smaller than white sharks but it seems what female elephant seals are in the same size range as female sharks. Was that seal a male or female.? Anyway, I would look to interactions between false killer whale/pilot whales as they are slightly larger than female great whites, but a freak 3000-4000 pounder should be able to take one. It's definitely male, females don't get noses that elongate.
That's non-comparable to the subject at hand, as both of those whales are very raptorial and have good defenses that give them the edge on the shark, not to mention that they weigh more on average, which shastasaurus can't claim for megalodon. A better comparison would be with a beaked whale.
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Post by Deleted on Dec 9, 2019 6:34:29 GMT 5
As in a female gws can get to 3k-4k pounds while a female pilot whale or false killer whale stays around 2k pounds so theoretically, a white shark can kill one. However, I'm not sure if they actually will because of the risk involved. Due to the mobility in the water as well as their dentition, they would be much tougher compared to a bulky elephant seal which is out of its element in open water. I've seen sea lions outmanuever white sharks though but i doubt a hulking elephant seal could do that too
I don't know much about beaked whales, do white sharks eat beaked whales ?
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Post by kekistani on Dec 9, 2019 7:03:00 GMT 5
As in a female gws can get to 3k-4k pounds while a female pilot whale or false killer whale stays around 2k pounds so theoretically, a white shark can kill one. However, I'm not sure if they actually will because of the risk involved. Due to the mobility in the water as well as their dentition, they would be much tougher compared to a bulky elephant seal which is out of its element in open water. I've seen sea lions outmanuever white sharks though but i doubt a hulking elephant seal could do that too I don't know much about beaked whales, do white sharks eat beaked whales ? IDK. We now killer whales eat them becasue some of the only beaked whale sightings on record are of Killer whales eating the carcasses.
GWS on average are smaller than FKW or PW.
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denis
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Post by denis on Dec 9, 2019 17:17:37 GMT 5
I'll admit i know nothing about elephant seals, in fact, I thought they were smaller than white sharks but it seems what female elephant seals are in the same size range as female sharks. Was that seal a male or female.? Anyway, I would look to interactions between false killer whale/pilot whales as they are slightly larger than female great whites, but a freak 3000-4000 pounder should be able to take one. It's definitely male, females don't get noses that elongate.
That's non-comparable to the subject at hand, as both of those whales are very raptorial and have good defenses that give them the edge on the shark, not to mention that they weigh more on average, which shastasaurus can't claim for megalodon. A better comparison would be with a beaked whale.
Source.
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