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How did the formation of Pangea change shallow-water habitats for marine organisms?

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Line graph showing the number of marine animal families from the Precambrian era to the present, with illustrations of key groups such as trilobites, ammonoids, marine reptiles, and diatoms. The graph highlights major extinction events and a rise to 1,900 living families today. — Permian extinction The diversity of marine animal families since late Precambrian time. The data for the curve comprise only those families that are reliably preserved in the fossil record; the 1,900 value for living families also includes those families rarely preserved as fossils. The several pronounced dips in the curve correspond to major mass-extinction events. The most catastrophic extinction took place at the end of the Permian Period.

The formation of Pangea significantly altered marine environments, contributing to the mass extinction event at the end of the Permian Period. As the supercontinent assembled, the total extent of shallow-water habitats declined substantially.

Furthermore, the configuration of Pangea created land barriers that inhibited the circulation of cold polar waters into tropical regions. This lack of circulation is believed to have reduced dissolved oxygen levels in the remaining warm-water habitats. These combined environmental stressors—the loss of habitat area and the decline in oxygenation—severely impacted marine life, contributing to a 95 percent reduction in the diversity of marine species during this period.1