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How did the Triassic-Jurassic mass extinction affect marine invertebrates?

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Jurassic paleogeography — Jurassic Period Distribution of landmasses, mountainous regions, shallow seas, and deep ocean basins during the late Jurassic Period. Included in the paleogeographic reconstruction are the locations of the interval's subduction zones.

The mass extinction at the Triassic-Jurassic boundary was a significant event that eliminated approximately half of all marine invertebrate genera. This extinction caused drastic population reductions and the disappearance of many families of brachiopods, gastropods, and bivalves.12

Among the most notable losses were the conodonts, which went extinct, and many Triassic ceratitid ammonoids, which suffered heavy casualties. Only the phylloceratid ammonoids survived the event, eventually giving rise to the explosive radiation of cephalopods during the Jurassic Period.2

The extinction is widely attributed to intense volcanic activity associated with the breakup of Pangea, which likely increased atmospheric carbon dioxide levels and led to ocean acidification. Other researchers suggest that sea level changes, climatic change, and associated anoxia were primary drivers of the collapse. Following this event, marine ecosystems began a recovery process, with diversity increasing rapidly during the early Hettangian Age.21