Unraveling the Origin of Dolphins: The Discovery of Their Earliest Predecessors

by Liam O'Connor
Dolphin Evolution

A vivid representation of Olympicetus thalassodon hunting a school of fish with plotopterid birds in the backdrop, set in the ancient waters of the eastern North Pacific Ocean. Credit: Cullen Townsend’s artwork

Paleontologists have made a groundbreaking discovery – a new toothed whale species, Olympicetus thalassodon, which inhabited the earth 28 million years ago and provides crucial information about the evolution of present-day dolphins. The species, along with two additional similar odontocetes discovered in the vicinity, are part of the Simocetidae family, one of the early divergent groups of toothed whales. However, the study has left some unresolved questions about their echolocation capabilities.

Curious about the first ancestors of today’s dolphins? Introducing Olympicetus thalassodon, an early species of odontocete, or toothed whale, which navigated the North Pacific coastal waters approximately 28 million years ago. This species, among others, is critical in piecing together the early chronicles and diversification of modern dolphins, porpoises, and other toothed whales.

The new species is detailed in a study unveiled today (June 23) in the freely accessible journal PeerJ Life and Environment by Jorge Velez-Juarbe, a Puerto Rican paleontologist from the Natural History Museum of Los Angeles County.

Jorge Velez-Juarbe. Credit: Jorge Velez-Juarbe

“Olympicetus thalassodon and its closely related species exhibit a unique set of traits that distinguishes them from other toothed whales. Several features, such as multi-cusped teeth, symmetric skulls, and anteriorly located nostrils make them appear as a transition between primitive whales and the dolphins we are familiar with today,” explains Dr. Velez-Juarbe, Associate Curator of Marine Mammals at NHMLAC.

Olympicetus thalassodon, however, wasn’t the sole species; the remains of two other closely related odontocetes are also described in the same research paper. All the fossils were collected from the Pysht Formation, a geological unit visible along the Olympic Peninsula coastline in Washington State, and are dated between 26.5–30.5 million years ago.

Olympicetus Phylogeny. Credit: Jorge Velez-Juarbe

The study also established that Olympicetus and its near relatives were part of the Simocetidae family, a group currently known only from the North Pacific and one of the earliest diverging groups of toothed whales. Simocetids were part of a unique fauna represented by fossils found in the Pysht Formation, which included plotopterids (an extinct group of flightless, penguin-like birds), the peculiar desmostylians, early kin of seals and walruses, and toothed baleen whales.

Simocetids. Credit: Jorge Velez-Juarbe

Differences in body size, teeth, and other structures related to feeding imply that simocetids had different methods of hunting and probably prey preferences. “The teeth of Olympicetus are remarkably unusual. They are what we refer to as heterodont, meaning they display variations along the row of teeth,” Dr. Velez-Juarbe notes, “this sharply contrasts with the teeth of more advanced odontocetes, whose teeth are simpler and almost identical.”

Nevertheless, several aspects of these ancient toothed whales’ biology are yet to be understood, such as their potential for echolocation, like their existing relatives. Some features of their skull suggest the presence of structures associated with echolocation, like a melon. A previous study proposed that neonatal individuals could not perceive ultrasonic sounds, so the following step is to inspect the earbones of juvenile and adult individuals to see if this changes as they age.

Reference: “New heterodont odontocetes from the Oligocene Pysht Formation in Washington State, U.S.A., and a reevaluation of Simocetidae (Cetacea, Odontoceti)” by Jorge Velez-Juarbe​, 23 June 2023, PeerJ Life and Environment.
DOI: 10.7717/peerj.15576

Frequently Asked Questions (FAQs) about Dolphin Evolution

What new species did paleontologists discover related to dolphin evolution?

Paleontologists have discovered a new toothed whale species, Olympicetus thalassodon, which lived around 28 million years ago. This species, along with two others found in the same region, are contributing to our understanding of the early history and diversification of modern dolphins.

Who led the study on Olympicetus thalassodon?

The study was led by Puerto Rican paleontologist Jorge Velez-Juarbe from the Natural History Museum of Los Angeles County.

What are some unique features of Olympicetus thalassodon?

Olympicetus thalassodon and its close relatives exhibit a unique set of traits that differentiate them from other toothed whales. Notably, they have multi-cusped teeth, symmetric skulls, and forward-located nostrils which make them appear as an intermediate between primitive whales and modern dolphins.

Where were the fossils of Olympicetus thalassodon found?

The fossils were collected from a geological unit known as the Pysht Formation, exposed along the coast of the Olympic Peninsula in Washington State, USA.

Are there any questions left unanswered in the study?

Yes, several aspects of these ancient toothed whales’ biology are yet to be understood. This includes determining whether they had the capability to echolocate, like their contemporary relatives.

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Jayden M. June 23, 2023 - 11:26 pm

jorge velez-juarbe must be thrilled to have made this discovery! how cool it must be to dig up the past like that.

Laura T June 24, 2023 - 1:46 am

Just thinkin.. if these ancient whales were around today, I bet they’d be a sight to behold. Huge and with strange teeth, huh? Sounds awesome!

Kevin H. June 24, 2023 - 2:57 am

Wow, so cool. Din’t know dolphins had such old ancestors! Amazing how far we’ve come in understanding these creatures.

Alex D. June 24, 2023 - 11:41 am

The connections with todays dolphins are truly fascinating, what a great read! I love this stuff.

Chloe P. June 24, 2023 - 2:08 pm

i’m a bit confused about the echolocation part…did these old whales have it or not? Guess more studies are needed.


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