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.
Fossil Facts
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
Rights & Permissions
