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Triassic Sharks Spawned in Fresh Water
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12-09-2011 1:13pm#1Bit of a curious one here: The discovery of what appears to be a nursery for two types of egg laying shark in Kyrgyzstan dating from the late Triassic.Gilles Cuny wrote:For all the people who think that modern sharks are some kind of living fossils that did not evolve since hundreds of millions of years, there is something to think about!
As far as I know no modern sharks breed in such a way.
Here is an illustration of a xenacanth shark fighting a Dimetrodon (by Robert T. Bakker):
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Bit of a curious one here: The discovery of what appears to be a nursery for two types of egg laying shark in Kyrgyzstan dating from the late Triassic.
As far as I know no modern sharks breed in such a way.
Here is an illustration of a xenacanth shark fighting a Dimetrodon (by Robert T. Bakker):
Good ol' Bakker, one of the few paleontologists with imagination XD
I think I read somewhere that the spine in the Xenacanth's head was venomous? That Dimetrodon looks like he's about to impale itself through the roof of the mouth >.<0 -
Bit of a curious one here: The discovery of what appears to be a nursery for two types of egg laying shark in Kyrgyzstan dating from the late Triassic.
As far as I know no modern sharks breed in such a way.
Here is an illustration of a xenacanth shark fighting a Dimetrodon (by Robert T. Bakker):
With some species of modern shark, the young congregate in shallow saltwater lagoons and in shallow reefs in a similar manner to what is described in the article. The young shark feed and grow in that area until they are old/big enough to venture into the open ocean.0 -
With some species of modern shark, the young congregate in shallow saltwater lagoons and in shallow reefs in a similar manner to what is described in the article. The young shark feed and grow in that area until they are old/big enough to venture into the open ocean.
Yeah but I think what he meant is that no ocean sharks breed in freshwater... even the bull shark, which is famous for being able to live in freshwater, has to return to the ocean to breed.
However, there ARE sharks that may breed in freshwater today. The true river sharks (genus Glyphis) are very poorly known, but there's some evidence that at least some species may live in coastal waters but swim up river to reproduce, as juveniles are always found in fresh and brackish water.
Unfortunately these rare sharks are very poorly known- no one really knows a lot about their life history.
River sharks:
Also, is it really correct to say that sharks "spawn"? I mean, sharks fertilize their eggs internally... I thought "spawning" was when fish released large numbers of eggs AND sperm into the water for external fertilization?0 -
Yeah but I think what he meant is that no ocean sharks breed in freshwater... even the bull shark, which is famous for being able to live in freshwater, has to return to the ocean to breed.
However, there ARE sharks that may breed in freshwater today. The true river sharks (genus Glyphis) are very poorly known, but there's some evidence that at least some species may live in coastal waters but swim up river to reproduce, as juveniles are always found in fresh and brackish water.
Unfortunately these rare sharks are very poorly known- no one really knows a lot about their life history.
River sharks:
Also, is it really correct to say that sharks "spawn"? I mean, sharks fertilize their eggs internally... I thought "spawning" was when fish released large numbers of eggs AND sperm into the water for external fertilization?
Not entirely true. There are pockets of bull sharks who one way or another became landlocked in lakes in South America and in Australia that have managed to maintain a population which strongly suggests that they can adapt to breeding in freshwater.
The population of Bull Shark in Lake Nicaragua in central America is also suspected to contain shark that are breeding there, and tagged adult bull shark have been recorded returning to the lake and they get back there in a very simuilar manner as to how salmon return to the river of their birth, by jumping up rapids and waterfalls etc.
Would agree with the questions of the word spawn in this case as well. My definition of spawning would be the same are what you have said.0 -
Not entirely true. There are pockets of bull sharks who one way or another became landlocked in lakes in South America and in Australia that have managed to maintain a population which strongly suggests that they can adapt to breeding in freshwater.
The population of Bull Shark in Lake Nicaragua in central America is also suspected to contain shark that are breeding there, and tagged adult bull shark have been recorded returning to the lake and they get back there in a very simuilar manner as to how salmon return to the river of their birth, by jumping up rapids and waterfalls etc.
Would agree with the questions of the word spawn in this case as well. My definition of spawning would be the same are what you have said.
Thanks for clearing that up, I actually was thinking of the Nicaraguan bull sharks when I wrote the above, but I remembered reading that they had been almost exterminated by now because they weren´t breeding in the lake, and they were being targeted by murderers- er, shark fishermen for the fin trade in their way to the ocean or something like that.
I already did some research on the definition of spawning and indeed, it does not apply to sharks. Maybe we should change the thread title? If we want to be very correct and geekish, that is
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Thanks for clearing that up, I actually was thinking of the Nicaraguan bull sharks when I wrote the above, but I remembered reading that they had been almost exterminated by now because they weren´t breeding in the lake, and they were being targeted by murderers- er, shark fishermen for the fin trade in their way to the ocean or something like that.
I already did some research on the definition of spawning and indeed, it does not apply to sharks. Maybe we should change the thread title? If we want to be very correct and geekish, that is
The sharks in Lake Nicaragua have been butchered for their fins alright, but a number of small juvenile shark have been found in the past there, and while this in not 100% proof that they are breeding in the lake, it does seem more likely that they were indeed born in the lake rather than the other option which would see the much smaller juvenile shark somehow make the same difficult journey to the lake as large adults have been recorded doing.
I can remember reading that it was seen as unlikely that they made it the whole way in from the sea as predators and the waterfalls along the route should have prevented them from doing so in any sort of number that would be comparable to the amount of juveniles found in the lake.
A similar train of thought has been suggested for the juveniles found thousands of miles up the Amazon and in some of the South American lakes0 -
The sharks in Lake Nicaragua have been butchered for their fins alright, but a number of small juvenile shark have been found in the past there, and while this in not 100% proof that they are breeding in the lake, it does seem more likely that they were indeed born in the lake rather than the other option which would see the much smaller juvenile shark somehow make the same difficult journey to the lake as large adults have been recorded doing.
I can remember reading that it was seen as unlikely that they made it the whole way in from the sea as predators and the waterfalls along the route should have prevented them from doing so in any sort of number that would be comparable to the amount of juveniles found in the lake.
A similar train of thought has been suggested for the juveniles found thousands of miles up the Amazon and in some of the South American lakes
Interesting. Now I think it's possible that Bull Sharks are on their way to give rise to new fresh-water species 0 -
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