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Post by creature386 on Jun 22, 2013 18:16:34 GMT 5
And do you see either winning the evolutionary battle at the moment? I don't. What has at one time been suggested is that the typically smaller carcharhiniform sharks are possibly repressing the lamniforms... Yes, exactly. Let's get back to the original question, did Pliosaurs repress Ichthyosaurs because they were more powerful? Not necessarily. Again, if one group going extinct (temnodontosauridae) and another one taking over its niche (pliosaurs) would always mean the latter was simply more powerful, there would be quite some paradoxa. Uhm, why did you quote the same sentence twice? |
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Post by Grey on Jun 22, 2013 18:16:37 GMT 5
Orcas repressed white sharks.
When CA2 killed a white sharks off Farallon Islands, the estimated 100 great whites individuals vanished of the region and migrated toward hawaian waters.
You did not check Siversson ? Great whites are doomed and will disappear, even without human interaction, whereas orcas are more dominant than ever. Probably, carcharhinids will replace white shark niche when it will have disappeared.
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Post by theropod on Jun 22, 2013 18:18:30 GMT 5
^Still no good comparison since the orca simply outclassed the white shark due to growing bigger. There is no rule behind this, and it is even to some extend a predator prey situation, or not?
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Post by creature386 on Jun 22, 2013 18:21:25 GMT 5
Great whites are doomed and will disappear, even without human interaction I don't know if this can be said. Without humans, the great white population may decrease, but you have to remember that humans still take a great part in the decreasing of sharks. Without human interaction, the sharks may have more time to find a niche where they can avoid orcas (maybe in the deep sea). |
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Post by creature386 on Jun 22, 2013 18:23:24 GMT 5
^Still no good comparison since the orca simply outclassed the white shark due to growing bigger. The same could have happened in Grey's ichtyosaur vs pliosaur scenario. |
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Post by Grey on Jun 22, 2013 18:34:10 GMT 5
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Yes, I've responded in my last post. Orcas are winning, and the rising carcharhinids, less sensitive than white sharks are slowly replacing them. Just like white sharks and orcas replaced megalodon and leviathan. No direct competition there, just replacement.
But orca ecologically outclasses the white shark as it can push them out of a region. Their ecological pressure and dominance is obvious.
I repeat for the second time.
I don't say that pliosaurs outcompeted ichthyosaurs because of their strength, I was comparing their respective reign of dominance. Pliosaurs were more dominant longer and developped more impressive (IMO) predatory apparatus.
I hope I don't have to repeat again.
Tylosaurines and mosasaurines grew bigger yes, and indeed, had others advantages for an evolutionnary perspective.
You're right here.
But orcas and white shark became dominant after the demise of megatooth.
Only the orcas grew bigger and became wider spread. I've not seen further in this but even at parity, during their evolution, we can suspect that orcas had better physical predispositions than the white shark to outcompete the other.
I don't know, do what you want, yes you're confusing to read !
You're wrong, some eras have been filled with far more numerous and far bigger potential preys. Read my quote from Kent for example ?
Because leviathan was related to the evolution of the filter-feeders, increase in number and size, it became bigger than most of the other predators in the evolution.
We don't see that gigantism related pattern evolution elsewhere among marine predators in evolution, at least not yet.
Fossils records indicate that for now, sorry if it disappoints you. Perhaps we'll found new exceptions for that pattern others than the two whales specialists of the Miocene.
Perterborough sounds highly doubtful and even then it would be just another new predator a bit exceeding 20 tons.
Just like for the big ichthyosaurs.
Even if we found of others predators above 20 tons, we'll probaby not found these in great number.
Now you think what you want, even disregard once again extended works...
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Post by Grey on Jun 22, 2013 18:36:51 GMT 5
^Still no good comparison since the orca simply outclassed the white shark due to growing bigger. There is no rule behind this, and it is even to some extend a predator prey situation, or not? You should read the papers about that event before arguing dude. The competitive pressure has been clearly hinted on that event. Yes orcas are bigger but still there is competition, both are apex predators of similar niches. |
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Post by coherentsheaf on Jun 22, 2013 18:43:54 GMT 5
^Still no good comparison since the orca simply outclassed the white shark due to growing bigger. The same could have happened in Grey's ichtyosaur vs pliosaur scenario. Except early jurassic pliosaurs are smaller than ichthyosaurs. If being bigger or more powerful is the deciding advantage, replacement of a top predator niche would be almost impossible, as initially the current top predator will always be larger. |
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Post by Grey on Jun 22, 2013 18:47:45 GMT 5
The same could have happened in Grey's ichtyosaur vs pliosaur scenario. Except early jurassic pliosaurs are smaller than ichthyosaurs. If being bigger or more powerful is the deciding advantage, replacement of a top predator niche would be almost impossible, as initially the current top predator will always be larger. In that case there are of course others evolutionnary factors, like those cited for mosasaurs (better reproduction rate, better access to food sources). |
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Post by creature386 on Jun 22, 2013 18:49:16 GMT 5
If being bigger or more powerful is the deciding advantage, replacement of a top predator niche would be almost impossible, as initially the current top predator will always be larger. Grey has never claimed they did so because of their strength: I don't say that pliosaurs outcompeted ichthyosaurs because of their strength, I was comparing their respective reign of dominance. Pliosaurs were more dominant longer and developped more impressive (IMO) predatory apparatus. |
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Post by coherentsheaf on Jun 22, 2013 18:52:02 GMT 5
Except early jurassic pliosaurs are smaller than ichthyosaurs. If being bigger or more powerful is the deciding advantage, replacement of a top predator niche would be almost impossible, as initially the current top predator will always be larger. In that case there are of course others evolutionnary factors, like those cited for mosasaurs (better reproduction rate, better access to food sources). I would say that was the case almost every time. Outcompetig has little to do with killing the other animal in a fight. |
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Post by Grey on Jun 22, 2013 18:55:02 GMT 5
True, only at the end, I constat that the winner is often the most robust, or at least evolves even more robust than its predecessor.
In any case, pliosaurs as apex predators evolved more spectacular and longer than macropredatory ichthyosaurs, although I agree that the data is lacking regarding the laters.
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Post by theropod on Jun 22, 2013 19:16:49 GMT 5
^Still no good comparison since the orca simply outclassed the white shark due to growing bigger. The same could have happened in Grey's ichtyosaur vs pliosaur scenario. But to date we have not a single pliosaur that was larger than these ichthyosaurs. If pliosaurs repressed them, which is probable, it wasn't necessarily due to mere power. Reproductive success, predatory success and efficiency, versatility are all factors that have to be considered here before focusing on "which would have won in a fight?" |
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Post by Grey on Jun 22, 2013 19:19:11 GMT 5
We're not sure yet that they really outclasses pliosaurs, even if that's quite possible. I'd prefer wait a proper description.
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Post by theropod on Jun 22, 2013 19:20:02 GMT 5
True, only at the end, I constat that the winner is often the most robust, or at least evolves even more robust than its predecessor. In any case, pliosaurs as apex predators evolved more spectacular and longer than macropredatory ichthyosaurs, although I agree that the data is lacking regarding the laters. How long giant macrophagous ichthyosaurs existed is not known to date, but at least from the Anisian to the Toarcian. Which is actually more formidable has to be determined on the basis of anatomy, not evolutionary history. We know little of their predatory anatomy, just that they had ziphodont teeth, and likely robust, large skulls mounted on huge bodies. Thalattoarchon is interesting to have a look at since it preserves a good part of the skull and is a nice example of a very large macrophagous ichthyosaur (stated to be VERY conservatively estimated at 8,6m), albeit probably smaller and less bulky than Himalayasaurus (of which both vertebra and radius are clearly exceeding all the compared Shonisaurus-specimens) or the unnamed temnodontosaur. In its morphology it seems to display some features reminiscent of an orca (eg. a compact skull and large, deeply rooted teeth), but others clearly different (eg. labiolingually flattened teeth with sharp cutting edges), but arguably also formidable. I would consider their jaws very formidable if they were anything like this one |
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