medium · SAT Reading & Writing

While the skeletal remains of the thalattosuchian, an extinct group of marine crocodylomorphs, suggest a fully aquatic lifestyle, recent CT scans of their inner ear anatomy reveal a more complex transition. Early species possessed vestibular systems similar to modern terrestrial crocodiles, whereas later forms evolved compact, thick-walled ear canals. Researchers argue that this specialized sensory adaptation was likely a response to the pressures of deep-sea diving rather than a prerequisite for entering the water. Which choice best states the main idea of the text?

1. Later species of thalattosuchians developed compact and thick-walled ear canals.
2. The sensory evolution of thalattosuchians followed their transition to a marine environment rather than preceding it.
3. The transition of crocodylomorphs to water was driven primarily by changes in their vestibular systems.
4. Thalattosuchians were incapable of deep-sea diving until their inner ear anatomy became identical to that of modern crocodiles.

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