US Scientists Have Found The Remains Of A Prehistoric Dolphin Five Meters Long
Paleontologists have found an almost complete skeleton of a prehistoric Dolphin In the US state of South Carolina. At length, he reached a height of approximately five meters and is marked by sharp "shark" teeth. The discovery of this fossil indicates a parallel, but separate evolution of baleen whales and dolphins, scientists write in the scientific journal Current Biology.
"We were very surprised that the features of anatomy that help dolphins and baleen whales swim quickly appeared in them independently of each other, and were not formed in their common ancestors. Among these similarities is the narrowing of the base of the tail, an increased number of tail vertebrae, and an equally short humerus," commented one of the authors of the article, a paleontologist from the College of Charleston (USA) Robert Bosseneker.
According to modern ideas, the first representatives of cetaceans appeared about 50 million years ago on the territory of the modern Middle East or South Asia. They were like large dogs that led to a semi-aquatic lifestyle. However, later their front legs turned into fins, the hind legs disappeared and their place was taken by the "whale" tail. The animals themselves gradually increased by several hundred times.
Subsequently, about 30 million years ago, the ancestors of cetaceans divided into two groups – baleen and toothed whales. The evolution of both groups took very different paths. How this happened and what their first representatives looked like, scientists can not yet say for sure, paleontologists find very few fossils of Oligocene whales (33.9 – 23.0 million years ago).
Bosseneker and his colleagues made the first major find of this kind – fragments of the skeleton of an unknown species of Dolphin that lived about 25 million years ago in the season what is now the East coast of the United States. The first of these fragments, part of the skull of a very large cetacean, was found by paleontologists in the 1880s on the banks of the Wando River, and the second almost complete skeleton was discovered during the construction of a residential block in Charleston in the 1990s.
The former owners of this skeleton recently donated it to the Charleston Museum of natural history. Thanks to this, scientists have studied in detail the structure of the skeleton of this cetacean and understand what it ate and how it looked.
Dolphin with a shark smile
Initially, as Bossenecker notes, researchers believed that they were dealing with a close relative of the ancient dolphins of the genus Squalodon. They lived about 20 million years ago and were similar in body shape to modern South Asian river dolphins. This was indicated by the shape and size of the skull, as well as some other features of the late nineteenth-century find and skeleton fragments found in the 1970s.
The discovery of a new, almost complete skeleton of this Dolphin has caused scientists to change their minds dramatically. In particular, it turned out that it had unusually large, but primitive teeth, more similar to the teeth of sharks than basilosaurus – the first toothed whales. Some of them were damaged or showed signs of mechanical damage.
This suggests that the Dolphin, named Ankylorhiza Tiedemani because of the unusual shape of the roots of its teeth, was a very specialized predator-feeding only on large prey. This distinguishes it from all other known Oligocene dolphins and suggests that its role in the ecosystem was similar to that of modern orcas.
Another unusual feature of Ankylorhiza Tiedemani is that the structure of its skull was adapted for echolocation. According to the researchers, this Dolphin was the first cetacean predator to take a dominant position in the ecosystem thanks to such an organ.
All this suggests that Ankylorhiza Tiedemani was both the largest and most primitive cetacean creature of the Oligocene. However, interestingly, many features of its anatomy, including the shape of the front fins and tail, were very similar to how similar parts of the body of baleen whales are arranged.
This, according to scientists, suggests that both these and other cetaceans initially developed along similar, but different paths. In the course of evolution, they got about the same set of devices for rapid movement in the water. Subsequent discoveries of the remains of ancient whales of that era, as I hope Boessenecker and his colleagues will help to understand how it happened.