CT Scan Reveals Ancient Evolutionary Adaptation

The tree of life is full of species that transitioned from aquatic to terrestrial. Some species occasionally went oppositely. A CT scan showed new information about the inner ear anatomy of ancient reptiles called thalattosuchians, providing details about one of these evolutionary turning points.

Following a protracted semiaquatic phase, these now-extinct crocodile relatives entered the ocean during the Mesozoic period. The thalattosuchians’ skeleton progressively adapted to their new aquatic environment during this process. In particular, these amphibians’ altered vestibular systems improved their swimming prowess.

It is a remarkably different evolutionary route for the same transition compared to whales, which adapted to living in the water quickly without a drawn-out semiaquatic stage. Using a high-tech computed tomography (CT Scan) device enabled the novel discoveries of an international research team.

Thalattosuchians were fast-moving marine predators that developed from their land-dwelling ancestors during the Mesozoic period, between 182 and 125 million years ago. A global study team investigated the evolutionary changes these crocodylomorphs underwent as they moved from the land to the ocean. The researchers concentrated on the inner ear, one of the vertebrates’ most significant sensory systems. The skulls of 18 thalattosuchians from the late Triassic to the Early Cretaceous were scanned using high-resolution computed tomography (CT), covering a significant portion of the development of crocodylomorphs.

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