They describe a new species of primitive toothed whale, ancestor of current dolphins

June 23 () –

Scientists have described a new species of primitive toothed whale, or toothed whale, the ‘Olympicetus thalassodon’which swam along the North Pacific coast about 28 million years ago and would be the ancestor of current dolphins, as published in the open access journal ‘PeerJ Life and Environment’.

The study, by the Puerto Rican paleontologist Jorge Velez-Juarbefrom the Los Angeles County Museum of Natural History, reveals that it is one of several species that are helping to understand the early history and diversification of modern dolphins, porpoises, and other toothed whales.

“Olympicetus thalassodon and its close relatives display a combination of characteristics that really sets them apart from any other group of toothed whales. Some of these characteristics, such as the multicuspid teeth, the symmetrical skulls and the forward position of the nostrils make them seem more like an intermediate between the archaic whales and the dolphins with which we are more familiar”, explains doctor Vélez-Juarbe, NHMLAC Associate Conservator of Marine Mammals.

But the ‘Olympicetus thalassodon’ was not alone, and in the same study the remains of two other closely related odontocetes are described. All of the fossils were collected in a geologic unit called the Pysht Formation, exposed along the coast of Washington State’s Olympic Peninsula and dated to between 26.5 and 30.5 million years old.

The study further revealed that Olympicetus and its close relatives belonged to a family called Simocetidae, a group known so far only from the North Pacific and one of the earliest divergent groups of toothed whales.

Symmocetids were part of an unusual fauna represented by fossils found in the Pysht Formation and that included Plothoptera (an extinct group of flightless penguin-like birds), the rare desmostilids, primitive relatives of seals and walruses, and baleen toothed whales.

Differences in body size, teeth, and other feeding-related structures suggest that simocetids displayed different forms of prey acquisition and likely prey preferences.

“The teeth of ‘Olympicetus’ are really strange, they are what we call heterodonts, which means that they show differences along the dental row -explains Vélez-Juarbe-this stands out against the teeth of more advanced toothed whales, whose teeth are simpler and tend to look almost the same.”

However, other aspects of the biology of these early toothed whales remain to be elucidated, such as whether or not they could echolocate like their living relatives. Some aspects of its skull can be related to the presence of structures related to echolocation, such as a melon.

A previous study had suggested that neonatal individuals could not hear ultrasonic sounds, so the next step would be to investigate the ear bones of subadult and adult individuals to see if this changed as they aged.