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Paleo Profile: The Strange, Defenseless Snout

Paleontologists name a new dwarf, toothless dolphin

Dolphin

A restoration of Inermorostrum xenops.

This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American


Dolphins are odontocetes. That literally translates to "toothed whales", the broader cetacean family that they belong to. But that's just the view from the top. Dig into the evolutionary history of whales some of these seagoing mammals start bucking the trend. There are ancient baleen whales - or mysticetes - that have teeth, for example, and researchers have just announced a 29 million year old "toothed whale" that doesn't have any teeth at all.

Paleontologists Robert Boessenecker and colleagues have named the ancient cetacean Inermorostrum xenops. Or, roughly, the "strange face with a defenseless snout." This fossil dolphin, which used to swim through seas that once covered what's now South Carolina, doesn't have a single tooth in its mouth. This, combined with its short snout, led Boessenecker and coauthors to propose Inermorostrum was a suction feeder, creating little underwater vacuums to slurp up prey.

Of course, no fossil whale stands - or is that swims? - alone. "The Oligocene represents one of the most important periods of whale evolution," Boessenecker and colleagues write, documenting an underwater evolutionary boom of different whale lineages. Inermorostrum is part of that, showing that ancient odotocetes weren't just sharp-toothed hunters. This time period saw ancient whales evolving a variety of ways to snap and sift and suck up their food, setting the stage for the what we see in their relatives today.

Skull

The skull of Inermorostrum xenops. Credit: Boessenecker et al 2017

Fossil Facts


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Name: Inermorostrum xenops

Meaning: Inermorostrum means "defenseless snout", while xenops means "strange face."

Age: Oligocene, about 29 million years ago.

Where in the world?: Berkeley County, South Carolina.

What sort of organism?: A dolphin belonging to a group called xenorophids.

How much of the organism’s is known?: A partial skull and fragment of braincase.

References:

Boessenecker, R., Fraser, D., Churchill, M., Geisler, J. 2017. A toothless dwarf dolphin (Odontoceti: Xenorophidae) points to explosive feeding diversification of modern whales (Neoceti). Proceedings of the Royal Society B. doi: 10.1098/rspb.2017.0531

Previous Paleo Profiles:

The Light-Footed Lizard The Maoming Cat Knight’s Egyptian Bat The La Luna Snake The Rio do Rasto Tooth Bob Weir's Otter Egypt's Canine Beast The Vastan Mine Tapir Pangu's Wing The Dawn Megamouth The Genga Lizard The Micro Lion The Mystery Titanosaur The Echo Hunter The Lo Hueco Titan The Three-Branched Cicada The Monster of Minden The Pig-Footed Bandicoot Hayden's Rattlesnake Demon The Evasive Ostrich Seer The Paradoxical Mega Shark The Tiny Beardogs The Armored Fish King North America's Pangolin The Invisible-Tusked Elephant The Mud Dragon The Spike-Toothed Salmon The Dream Coast Crocodile Buriol's Robber Ozimek's Flyer The Northern Naustoceratopsian The High Arctic Flyer The Tomatillo From the End of the World The Short-Faced Hyena The Mighty Traveler from Egg Mountain Keilhau's Ichthyosaur Mexico's Ancient Horned Face Mauricio Fernández's Plesiosaur New Zealand's Giant Dawn Penguin The Orange Sea Lion Mongolia's Ginkgo Cousin The Geni River Frog Isabel Berry's Dinosaur The Whale Caiman The Moab Lizard Yang Zhongjian's Lizard The Little Anubis The Shuangbai Lizard The Wyvern Dinosaur The "Need Helmet" Dinosaur The Jianianhua Dragon The Liaoning Hunter The Dalian Lizard Crompton's Aleodon Jenkins' Amphibian Serpent From the Chinle The Large Ancestor Lizard The Crown Tooth Currie's Alberta Hunter The Elephant Bird Mimic The Crested Thief The Hiding Hunter The Horned Lizard The Silk Bird The Sieve-Toothed Plesiosaur