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?