U.S. paleontologists talked about Ankylorhiza tiedemani, a predatory dolphin from the Oligocene era that died 23 million years ago.
Scientists from Charleston College (USA) found in South Carolina an almost complete skeleton of the prehistoric dolphin Ankylorhiza tiedemani, who lived about 25 million years ago and reached five meters in length. The find is described in the journal Current Biology.
Previously, Ankylorhiza tiedemani was known to us only by a fragment of the rostrum – the preorbital region of the skull – discovered at the end of the 19th century. According to the authors of the study, numerous evidence – from the structure of the skull and sharp teeth to the fin and spine – show that this large dolphin was the dominant super-predator in its habitat. Many features of its postcranial skeleton also imply that modern whiskered and toothed whales, apparently, independently developed similar features due to the parallel evolution and habitat in the aquatic environment.
“The fact that the baleen whales and dolphins, independently of each other, achieve the same common swimming adaptations, and not the traits that once developed between the common ancestor of both groups, surprised us,” says Robert Bossenecker, one of the authors work. – Some examples include narrowing of the caudal process, an increase in the number of caudal vertebrae, and shortening of the humerus in the fin. This does not occur, for example, in different species of seals and sea lions, which have developed different ways of swimming and have very different in appearance postcranial skeletal bones. As if adding extra bones to the fin and fixing the elbow joint forced both main groups of cetaceans to follow the same evolutionary path”.
In addition, the study of the skeleton showed that Ankylorhiza tiedemani hunted exclusively for large prey, like modern killer whales. This is its difference from all other known Oligocene dolphins. Researchers noted yet another intriguing fact: Apparently, Ankylorhiza tiedemani is the first echolocating cetacean predator to occupy a dominant position in the ecosystem. Representatives of this species died out 23 million years ago.
“Whales and dolphins have a complex and long evolutionary history, and you may not get that impression of observing their modern species,” Bossenecker adds. “Our research has opened this long, winding path of evolution”.