What Actually Died Off at the Great Dying?

[Polycarp]

Whenever one reads about the mass extinction events, the high benchmark is always the Permian-Triassic extinction event, when supposedly over 90% of all speices died off. And I won’t doubt that that figure is accurate.

But one would think that that would mean that at least a reasonable proportion of higher taxa went extinct as well. And frankly, I’m not seeing that in the (textbook-level) literature.

Okay, brachiopods got reduced from a major component of the seafloor fauna to a very minor one. But they survived. Trilobites and acanthodians (‘spiny sharks’) died out during the Permian – but well before its end, and both were groups in decline – much as if the tuatara died out today: a whole order would die out with it, but outside New Zealand it would be noticeable only to people interested in such stuff, kind of a ‘celebrity death pool’ item. Several lineages of amphibians died out – but their relatives survived into and dominated the early Triassic.

So what actually died off in the Great Dying?

[Dervorin]

Lots, if you check with Wikipedia: Permian–Triassic extinction event - Wikipedia

@Wiki

Marine invertebrates suffered the greatest losses during the P–Tr extinction. In the intensively-sampled south China sections at the P-Tr boundary, for instance, 280 out of 329 marine invertebrate genera disappear within the final 2 sedimentary zones containing conodonts from the Permian.

The end-Permian is the only known mass extinction of insects, with eight or nine insect orders becoming extinct and ten more greatly reduced in diversity.

There is enough evidence to indicate that over two-thirds of terrestrial amphibian, sauropsid (“reptile”) and therapsid (“mammal-like reptile”) families became extinct. Large herbivores suffered the heaviest losses.

Even among those families and orders that survived, large numbers of genera and species were wiped out. Snails, for example, had a 98% reduction in the number of genera (from the above link).

[Polycarp]

That’s a nice summary, Dervorin, and it brings together a lot of what I’d seen before. The point is that, by and large, it was “most of X, Y, and Z, died out, and the survivors re-radiated”. along with “M and N died out during the Permian but either (a) had been in decline, with only a couple genera surviving, or (b) may have died out before the P-Tr event, or © both.” The blastoids are a notable exception I hadn’t remembered – that’s a whole class of echinoderm that died out.

Thanks for the link, though.