Newswise — Curious about the appearance of the ancient ancestors of today's dolphins? Allow me to introduce you to Olympicetus thalassodon, a recently discovered species of early toothed whale, known as an odontocete. Approximately 28 million years ago, this remarkable creature inhabited the North Pacific coastline. Its discovery, along with other similar species, contributes significantly to our understanding of the early evolution and diversification of modern dolphins, porpoises, and other toothed whales. The detailed description of this new species can be found in the open access journal PeerJ Life and Environment, authored by Jorge Velez-Juarbe, a paleontologist from the Natural History Museum of Los Angeles County.
According to Dr. Velez-Juarbe, Associate Curator of Marine Mammals at NHMLAC, Olympicetus thalassodon and its close relatives possess a unique set of features that distinguish them from all other groups of toothed whales. Notably, their combination of characteristics, such as multi-cusped teeth, symmetric skulls, and forward nostril placement, gives them an appearance that bridges the gap between ancient whales and the more recognizable dolphins we know today.
Olympicetus thalassodon was not the sole discovery in the study. The paper also documented the remains of two other closely related toothed whales, all originating from the Pysht Formation. This geological unit is found along the coast of the Olympic Peninsula in Washington State and is estimated to be around 26.5 to 30.5 million years old.
Additionally, the study unveiled that Olympicetus and its closely related counterparts belonged to a family known as Simocetidae. This particular group is currently only known from the North Pacific and represents one of the earliest branches in the evolutionary tree of toothed whales. Simocetids were part of a peculiar ecosystem documented by fossils discovered in the Pysht Formation. This ecosystem featured a diverse range of species, including plotopterids (flightless birds resembling penguins), the peculiar desmostylians, early ancestors of seals and walruses, as well as toothed baleen whales.
Variances in body size, teeth, and other feeding-related structures indicate that simocetids employed diverse methods of acquiring prey and likely had distinct preferences for certain types of prey. Dr. Velez-Juarbe highlights the peculiar nature of Olympicetus' teeth, describing them as heterodont, which means they exhibit variations along the tooth row. This characteristic sets them apart from the teeth of more advanced odontocetes, whose teeth are simpler and tend to have a uniform appearance.
Nevertheless, several aspects of the early toothed whales' biology still require further investigation, including their ability to echolocate like their modern relatives. Certain features of their skulls are potentially associated with echolocation, such as the presence of a melon structure. A previous study indicated that newborn individuals might be unable to perceive ultrasonic sounds. Therefore, the next phase of research would involve examining the earbones of subadult and adult specimens to determine if this capability developed as they matured.
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