Why Did The Trilobites Go Extinct?

[ralph124c]

I mean, they lasted for millions of years, and had a very wide range/habitat.
They also don’t look all that different from modern arthropods. Plus, they lived under water, so they were pretty well protected from harsh weather.
I realize that paleontologists don’t have much to go on (from examining fossil remains), but were these creatures so specialized that they could not withstand any disruption of their environment?
Finally, would biologists be surprised if some modern ones were found living near one of those deep sea volcanic vents? They could have hidden in places like that, and escaped the great extinction.

[Sailboat]

Wikipedia offers a decent summary:

Exactly why the trilobites became extinct is not clear; with repeated extinction events (often followed by apparent recovery) throughout the trilobite fossil record, a combination of causes is likely. After the extinction event at the end of the Devonian period, what trilobite diversity remained was bottlenecked into the order Proetida. Decreasing diversity[66] of genera limited to shallow water, shelf habitats coupled with a drastic lowering of sea level (regression) meant that the final decline of trilobites happened shortly before the end Permian mass extinction event.[61] With so many marine species involved in the Permian extinction, the end of nearly 300 million successful years for the trilobite is hardly surprising.

I would interpret that through Stephen Jay Gould’s reminder that extinction and survival are often contingent, meaning randomness (“luck”) is a factor, not just fitness. Example: suppose one particular subgroup of trilobites has evolved a mutation that resists the climate change that’s about to happen, but a rockslide wipes them all out, and they do not thus wind up surviving the climate change. Sometimes it’s just luck.

So my interpretation of what the Wikipedia page suggests is that various previous events resulted in most of the extremely diverse trilobites going extinct, gradually narrowing the surviving types through a long decline to those adapted to shallow waters. Then the Permian Mass Extinction, the worst one ever, which wiped out 96% of marine species, abruptly finished off those survivors.

[Anne_Neville]

Nobody knows what caused the Permian-Triassic extinction event, in which the trilobites became extinct. There are several theories, but nobody knows which, if any, of them is correct. Whatever it was, it didn’t just kill off the trilobites. It caused the largest mass extinction in Earth’s known history.

Whatever happened, living in the ocean was not good protection against it. Up to 96% of all marine species became extinct, as opposed to 70% of land-dwelling vertebrate species. Living under water is no guarantee of surviving a mass extinction, or even of having a better chance of surviving one than a land-dwelling species would.

[dolphinboy]

I often heard it said that 90% of all animal species that ever lived on the planet have gone extinct. A better question might be how did the Trilobites manage to hang on for so long?

[Elendil_s_Heir]

Fun fact: Trilobites are the official Ohio state fossil.

http://www.ohiohistorycentral.org/entry.php?rec=1874

[SmithCommaJohn]

@dolphinboy

I often heard it said that 90% of all animal species that ever lived on the planet have gone extinct. A better question might be how did the Trilobites manage to hang on for so long?

I understand that it’s actually well above 99%

[VOW]

Because of all the extinct creatures, I wonder just how many of the so-called “protected species” are really slated to die off?

IMHO, trilobites HAD to die, so we could enjoy all the neat-o fossils!
~VOW

[John_DiFool]

@SmithCommaJohn

I understand that it’s actually well above 99%

It depends on whether you call a line of descent which is still extant the evolution of one species or not. I.e. the difference between a species which went extinct and has no current descendants, vs. a species which went extinct but does have descendants.

[whitetho]

@VOW

Because of all the extinct creatures, I wonder just how many of the so-called “protected species” are really slated to die off?

~VOW

Probably worth a link to Evolution Going Great, Reports Trilobite from that famous scientific journal, The Onion.