Lucas Joel

Oceans today are home to a variety of seals, ranging from leopard seals darting through Antarctic surfs in pursuit of a penguin to endangered Hawaiian monk seals lounging on sunlit shores.

But how did seals first take the evolutionary dive into the oceans more than 30 million years ago? Paleontologists know that seals’ ancient ancestors lived and walked on land. But what helped transform them into marine mammals is a tale riddled with holes.

Recently, a pair of researchers studying prehistoric seal fossils and remains of modern species discovered a new piece of the story. They reported in March in the Journal of Vertebrate Paleontology that contemporary seals attack and bite their prey using much the same technique that their ancestors did millions of years ago.

Morgan Churchill, a paleontologist at the University of Wisconsin-Oshkosh who was not involved in the work, called this study of seals, “the first comprehensive analysis that’s looked at the skulls and mandibles of living species that also incorporates fossils.”

Their finding suggests that the ability to bite was an evolutionary adaptation that contributed to the animals’ ability to make a successful transition from land to water, said Sarah Kienle, a comparative biologist at the University of California, Santa Cruz who led the research.

Seals today have a variety of eating styles. Take the leopard seal. If it catches its penguin, Kienle says, it will devour the bird in a characteristic way: it will bite it, and then shake it until the penguin breaks into pieces that the seal can swallow.

But some seals also use additional eating techniques. Some suck in food such as fish from the water. Some take a gulp of krill and then filter out the water through their teeth, like baleen whales. Each species of seal has a unique skull and lower jaw shape that can be used to identify its eating style.

Knowing that these different styles exist, Kienle and her colleague, Annalisa Berta of San Diego State University, compared the bones of fossil seals with specimens of every known modern seal so that they could identify the eating styles of the seals’ ancestors. The team built digital maps using images of bones from 234 modern seals and 15 extinct seals. These maps clustered together landmarks on the sets of bones that the researchers say identified seals that fed by biting, using suction or filter-feeding.

They then compared the maps from modern seals with those of extinct seals, and found that extinct species were mostly biters, suggesting that the ability to bite is something that seals inherited from their terrestrial forebears. And that likely means that the ancient seals who first took to the oceans started out with biting instead of the diverse eating styles of contemporary seals.

“It makes sense, because they evolved from terrestrial carnivores,” Kienle said. She adds that seal ancestors were “able to take a feeding strategy that they were doing on land and successfully translate that to the water environment,” a technique that has allowed these marine mammals to thrive and diversify into a variety of ocean habitats some 30 million years later.

This article originally appeared in <a href="https://www.nytimes.com/2019/04/04/science/seals-evolution-biting.html" id="a319617e-7572-3c9b-ab2c-19721e739e42">The New York Times</a>.

(Trilobites)

How Seals Took to the Seas

The dinosaur, Ambopteryx longibrachium, lived about 163 million years ago. When Min Wang, a vertebratepaleontologist at the Chinese Academy of Sciences, first saw the fossil, which he and his team pulled out of Jurassic-age rocks in Liaoning province in China, “I thought it was a bird,” he said.

Birds evolved from dinosaurs, and so the two groups share many features. Wang assumed Ambopteryx was a bird because the animal sported relatively long forelimbs, just as modern birds do. But as his team carefully chipped away the rock surrounding the fossil over the course of about a year, distinctly dinosaurian features began to emerge. Ambopteryx, for one thing, had long fingers, a trait that birds lack.

Wang’s team was also surprised to find the remains of soft tissue around the dinosaur’s arms and torso. This tissue, in life, formed flaps of skin that probably resembled batlike wings, Wang said.

The new find, published in the journal Nature, follows a report in Nature in 2015 — by a team including authors of the new paper — that described the only other known batlike dinosaur. That animal, called Yi qi, was the first of its kind, and other paleontologists were skeptical.

The doubts arose because Yi qi was so bizarre.

“I think that if you had asked a paleontologist to just draw up some kind of fantasy dinosaur, you know, a lot of us never would have come up with something that was that weird,” said Stephen Brusatte, a vertebrate paleontologist at the University of Edinburgh, who was not involved in the new research. But the discovery of Ambopteryx, which is a close cousin of Yi qi, “pretty much seals the deal that there was this group of dinosaurs with batlike wings,” he said.

So batlike dinosaurs definitely existed. But exactly how Ambopteryx flew through the air remains unclear.

The team’s best guess is that the animal’s flying style was “halfway between a flying squirrel and a bat,” said Jingmai O’Connor, a co-author and a vertebrate paleontologist at the Chinese Academy of Sciences.

Despite this lingering mystery, Brusatte said, the discovery of Ambopteryx underscores that on the dinosaur family tree, there were several branches — not just the one that led to birds — that gave rise to flying dinosaurs. And, he added, it is unsurprising that dinosaurs may have evolved to fill the kinds of ecological roles filled today by mammals such as flying squirrels.

Perhaps paleontologists should not be too shocked by the next oddity they dig up.

“Maybe a dinosaur with seven arms, or a tyrannosaur with a big horn sticking out of its head, or, I don’t know, a brachiosaurus with webbed feet,” he said. “I have no idea! Who knows what we might find. But that makes the field very, very exciting.”

This article originally appeared in <a id="44428a2d-3817-33ac-a7b0-368542a5f2f7" href="https://www.nytimes.com/2019/05/08/science/dinosaur-bat-wings.html">The New York Times</a>.

Dinosaurs with bat wings were more than legend

Imagine an animal that looks like a dinosaur, and you probably will not imagine a bat. But that may change. A team of paleontologists in China announced on Wednesday the discovery of a dinosaur that sported the same kinds of fleshy wings bats use to flit through the air.

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Lucas Joel

Articles written by the author

How Seals Took to the Seas

Dinosaurs with bat wings were more than legend