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Increasing fossil finds are helping researchers understand how such early whales made their way to the continent 

By Riley Black, January 3, 2022

In 1973, amateur paleontologist Peter Harmatuk found a strange tooth in the rock of a stone quarry near Castle Hayne, North Carolina. At the time, the tooth’s identity wasn’t clear beyond “mammal.” But just last year, George Mason University paleontologist Mark Uhen and colleague Mauricio Peredo published a more refined interpretation. The tooth appears to have belonged to a group of strange, long-snouted whales called remingtonocetids. Picture a large otter with a comically-long snout and you have a general idea of what these mammals looked like, creatures that were able to ply the waves as well as walk along sandy beaches. Perhaps that seems strange. Whales are most familiar to us as creatures of the sea, propelling themselves through the water with their paired flukes. Somehow, however, seal-like whales had made it to the shores of ancient North America from southern Asia.

“Remingtonocetids are thought to be coastal animals,” Uhen says, more like modern seals and sea lions. Instead of swimming straight across the ancient Atlantic, then, they may have gradually expanded their range from their place of origin near ancient Pakistan and India through Eurasia, eventually crossing a much shorter distance to northern North America, possibly in what’s now Canada, and then moving south.

Tracing the route these whales took may be difficult. Rocks of the relevant age, Uhen says, aren’t found north of New Jersey. Clues about the coastal route the otter-like whale took may have been lost due to quirks of geology. But that doesn’t mean the trail has gone entirely cold. “Undoubtedly there are more middle Eocene, semi-aquatic whales to be discovered and described in North America,” Uhen says. The fossils are relatively rare, and hard to find, but they are there. The rock formation that the new tooth came from, for example, has also yielded the remains of a protocetid—or proto whale—named Crenatocetus and fully-aquatic whales named Pachycetus and Cynthiacetus, all of which have been named since 1990.

Thanks to such finds, paleontologists have been able to outline the ancestry of today’s leviathans in greater detail, and there’s more to the story than the origin of humpbacks and bowheads. Researchers are continuing to turn up strange new species of early whales, often in unexpected places. Many early whales were not as closely bound to the land as previously thought, and finds like the remingtonocetid from North Carolina are demonstrating how a diverse array of amphibious whales were able to spread around the world.

Ever since the mid-19th century, paleontologists and anatomists have been fascinated with the puzzle of how whales went from living on land to spending their whole lives in the sea. The relevant fossils to explain the transition seemed elusive and experts could really only guess as to how whales originated. That changed in the 1970s. 

The discovery of a roughly 55-million-year-old whale called Pakicetus helped center paleontologists’ focus on Pakistan, India and Egypt, and soon there was a veritable flood of early whale species. Even this year, Mansoura University Vertebrate Paleontology Center paleontologist Abdullah Gohar and colleagues named a new early whale, Phiomicetus anubis, from Egypt. The ancient menagerie doesn’t represent a straight line of land-dwelling mammals becoming more and more at home in the water. Different species of early whales overlapped in time and space, Gohar says, pointing out Phiomicetus as but one example. The whale lived alongside another otter-like whale called Rayanistes, and, Gohar speculates, the sharp-toothed Phiomicetus may have targeted the calves of its relative. Early whale species did not appear one after the other, but represented an entire family that proliferated around the water’s edge before whales became entirely at home in the sea.

The prehistoric coastlines of North America play a role in the story, too. During the 19th century, Black slaves discovered large bones in the fields of the South. These fossils were later named and described by paleontologists in the U.S. and England, although researchers did not always immediately know what they were looking at. Naturalist Richard Harlan, for example, thought some of these bones belonged to an enormous seagoing lizard and named them Basilosaurus—meaning “king lizard”—before anatomist Richard Owen recognized that the creature was a mammal and likely a fossil whale. And it was big. The largest specimens represent animals about 66 feet long, the largest mammal that had ever lived until modern whale families began to evolve. And Basilosaurus wasn’t alone. Paleontologists are now realizing that there was a greater diversity of early whales in North America than they previously expected.

Millions of years ago, whales also walked along the shores of ancient Georgia. If you were to visit the beaches of what would one day become the Peach State about 40 million years ago, you might spot a strange mammal waddling along the shore or lurking in an estuary like a big, hairy crocodile. Paleontologists know this animal as Georgiacetus, one of several early whales whose fossils have helping experts explore how whales went from amphibious mammals to the blubbery beasts we know today.

Like the newly-named Phiomicetus, Gohar says, the creature belonged to an ancient group of protocetids that represent a turning point in whale evolution. Named in 1998, Georgiacetus resembles other early whales found in northern Africa, Asia, and, as a recent find elucidated, South America. The whale was more amphibious and retained functional hind limbs that would have allowed the mammal to stand on land. The fact that Georgiacetus turned up in the rocks of North America indicates that whales were capable of swimming across entire oceans, like the ancient Atlantic, even before they became fully adapted to life at sea. “Protocetids are regarded as the first cetaceans who conquered the oceans,” Gohar says.

By land or by sea, early whales moved between continents and were a larger part of Earth’s ancient ecology than paleontologists previously expected. Digging up new information about early whales isn’t just about adding new species to the growing list of fossil species. The fact that early whales keep turning up in unexpected places indicates that some were probably more adept in the water than previously recognized. By sea or by coast, whales started to move further and further afield very quickly after their origin, their lives deeply connected to the water. Long before the evolution of blowholes or blubber, whales were at home in the seas. It’s unclear where the next tantalizing find will turn up, but, given the surprising discoveries of the past three decades, fossil whales will surely keep making waves.

Riley Black |  | READ MORE

Riley Black is a freelance science writer specializing in evolution, paleontology and natural history who blogs regularly for Scientific American.

(Sources: Smithsonian Magazine)