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Between shark and ray: The evolutionary advantage of the sea angels

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Complete skeleton of a sea angel (Pseudorhina acanthoderma; SMNS 86214/41) from the Upper Jurassic period (ca. 155 Millionen years) from the Nusplinger Plattenkalke in Baden-Württemberg (Germany). Credit: J. Kriwet The general picture of a shark is that of a fast and large ocean predator. Some species, however, question this image—for example angel sharks. They have adapted to a life on the bottom of the oceans, where they lie in wait for their prey. In order to be able to hide on or in the sediment, the body of angel sharks became flattened in the course of their evolution, making them very similar to rays, which are closely related to sharks.

Flattened body as indication for a successful lifestyle

The oldest known complete fossils of angel sharks are about 160 million years old and demonstrate that the flattened body was established early in their evolution. This also indicates that these extinct angel sharks already had a similar lifestyle as their extant relatives—and that this lifestyle obviously was very successful.

Angel sharks are found all over the world today, ranging from temperate to tropical seas, but most of these species are threatened. In order to understand the patterns and processes that led […]

read more here —> phys.org

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