Scientists Track Repeated Marine Predator Evolution in Ancient and Modern Oceans

Scientists have taken a closer look at the evolution of marine predators. Drawing on recent breakthroughs, they've taken a comprehensive look at how life in the ocean has responded to environmental change from the Triassic to the Anthropocene.

In this latest study, the researchers synthesized decades of scientific discovers to examine the patterns driving the transitions that whales, dolphins, seals and others species underwent as they moved from land to sea.

Marine tetrapods actually represent a diverse group of living and extinct species of mammals, reptiles, amphibians and birds that all play a critical role as large ocean predators in marine ecosystems.

"We know from the fossil record that previous times of profound change in the oceans were important turning points in the evolutionary history of marine species," said Neil Kelley, one of the researchers, in a news release. "Today's oceans continue to change, largely from human activities. This paper provides the evolutionary context for understanding how living species of marine predators will evolve and adapt to life in the Anthropocene."

In some cases, similar anatomy evolved among lineages that adapted to marine lifestyles. As an example, modern dolphins and extinct marine reptiles called ichthyosaurs descended from distinct terrestrial species. However, they both have an extremely similar fish-like body plan even though they were separated in time by more than 50 million years.

"Land to sea transitions have happened dozens of times among reptiles, mammals and birds, across major extinctions," said Nicholas Pyenson, one of the researchers. "You often get similar looking results but convergence is more than skin deep. It can be seen on a broad range of scales, from molecules to food webs, over hundreds of millions of years."

Not all adaptations seen in marine tetrapods can be blamed on convergent evolution, for example. As baleen whales evolved to live underwater, they developed a unique filter-feeding system that depends on hair-like plates instead of teeth. In contrast, toothed whales evolved to catch and feed on prey by emitting calls and using echolocation.

The findings are published in the journal Science.

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