Early whales swam in the seas, gracefully "wagging their hips", or rather, with both hind legs at once. Paleontologist Mark Uhen and his colleagues from the Alabama Museum of Natural History presented this vision of the transition of whale ancestors from land to water based on an analysis of recent findings
It is known: the distant ancestors of whales were land animals that walked on four legs, then they switched to a semi-aquatic lifestyle, and now we have a family of cetaceans sporting fins and powerful tails that allow them to pierce the water column at high speed.
In the photo: Modern baleen (Mysticeti) and big-toothed (Odontoceti) whales (top) evolved from the “waving hip up and down” style of the ancient whale Georgiacetus (bottom). An intermediate view is shown between them (illustration by Mary Parrish, Smithsonian Institution).
Not everything is clear with the intermediate forms of this branch of the tree of life. And one of the key points is when exactly the whale's tail fin appeared and how the anatomy of early whales affected their way of moving in the water.
Wen analyzed new remains recently found by amateur fossil hunters along the banks of rivers in Alabama and Mississippi. The bones belonged to the ancient species of whale Georgiacetus vogtlensis, which swam along the coast of the Gulf of Mexico about 40 million years ago. This creature reached approximately 3.7 meters in length and probably used its sharp teeth to deal with squid and fish.
According to biologists in a press release from the Society of Vertebrate Paleontology, this species is not new to science. But the "fresh" remains provided researchers with previously unknown information about the tail of this creature.
So, he did not have a caudal fin, but he had very developed hind legs. It was they who served as "motors", or rather, the "flight" of this creature in the water was facilitated by the undulating movement of the body in the hips.
Previously, scientists have suggested that whales in their evolution have experienced several methods of movement in water: rowing with four legs, only hind legs, swinging and waving the tail.
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The undulating movement of the femoral part of the body was usually considered “missed” in this chain, which, after a series of experiments, led, they say, to the “calling card” of whales - the movement of the tail up and down.
However, according to Mark, who studied the new fossils of Georgiacetus and, in particular, its caudal vertebrae, this is the movement that ancient whales "invented" without having acquired the tail fin itself.
It is interesting that the closest heirs of Georgiacetus, who had already received a real whale tail, lived only 2 million years after the "whale with legs".
Earlier, scientists also discovered that Georgiacetus vogtlensis had large hips (and therefore hind legs), but its pelvis was not connected to the spine. This meant that this animal not only could not support its weight on land, but was also unable to perform powerful strokes with its hind legs (as, for example, ducks do), which baffled the researchers.
Now Wen has solved the riddle by proposing a "wave-femoral" thrust design. So this ancestor of whales swam in almost the same way as they swim now, although outwardly it did not look like them.
Find out why some scientists suggest that whales be classified as artiodactyls and read about a very strange ancient whale.