Pangea Split Reconsidered Because of Ancient Mammal Skull Found in Utah

Its owner wasn't quite reptile but not quite mammal, either.

A weird 130-million-year old skull discovered in eastern Utah is shaking up what we know about mammals and the ancient giant landmass Pangea. The small skull, found beneath the fossilized foot of a massive dinosaur, belongs to a new species newly named Cifelliodon wahkarmoosuch. The latter half of the name means “yellow cat” in the ancestral language of the Ute tribe, but as the Nature paper describing it clearly shows, this critter was quite unlike any cat living today.

A full-grown 2.5-pound Cifelliodon was probably the size of a pika, write the scientists in their study, and it likely had a small brain, tiny eyes, and teeth similar to fruit-eating bats. It’s clear, from the artist’s rendering shown below, that this was not a cute kitty. It technically wasn’t a cat at all: Cifelliodon is not classified in the paper as a mammal but as an “early mammal.” The presence of this weird animal in Utah, the team writes, also means that it’s time to seriously rethink what we know about the supercontinent Pangea.

“Based on the unlikely discovery of this near-complete fossil cranium, we now recognize a new, cosmopolitan group of early mammal relatives,” lead author and University of Southern California professor of integrated anatomical sciences Adam Huttenlocker, Ph.D. announced in a statement released Wednesday.

The new species *Cifelliodon wahkarmoosuch*.

Jorge A. Gonzalez

The scientists theorize that Cifelliodon belongs in a group called the haramiyidans — an extinct group of animals that co-existed with the dinosaurs (hence, the foot squashing). It’s not clear where they lie on the larger family tree: Some scientists believe they were the transitionary bridge between reptiles and mammals, while others claim were some of the very first mammals to exist.

Nevertheless, the subgroup that Cifelliodon belongs to, called Hanodontidae, has previously only been found in regions of North Africa dating to the Cretaceous period, which began 145.5 million years ago and ended 65.5 million years ago. The presence of a Hanodontidae family member in the Americas suggests that Pangea stuck together for a lot longer than we once thought, continuing to separate about 15 million years later than previous estimates.

The cranium of *C. wahkarmoosuch*.

Huttenlocker et. al. 

For a long time, it was generally accepted that the northern and southern continents of Pangea were completely separated by the end of the Jurassic period, somewhere around 145 million years ago. But recent discoveries, like evidence of a “North Atlantic Land Bridge” that connected the two continental masses, together fossils of shared dinosaur groups found in Africa and Europe, suggests that we’ve had the timing and order of Pangea’s breakup wrong. The discovery of Cifelliodon seems to further support that hypothesis.

This map of Pangea, from an unrelated study, shows how closely Africa and the Americas were once connected.

S. Brune, GPlates

The presence of the skull — found with only one tooth — indicates that the geographic range of the haramiyidans was much larger than previously believed and that they were able to spread to what is now North America because the division of the ancient landmass wasn’t complete. The study authors note that mammal migration, and that of their close relatives, likely continued through 145 to 101 million years ago. During this time they exploded into an ecologically diverse group and began to occupy a variety of niches that their ancestors still live in today.

The skull itself also reveals insights into the haramiyida group: Huttenlocker explained in an interview with USC on Wednesday that 3D analysis gave he and his team “rare insights into the origins of mammalian anatomy, brain structure, and even the biogeography of the early mammalian radiation.”

Huttenlocker, who has found more than 500 fossil vertebrates during his 13-year long career, also says that this find is the one he’s most proud of. Cifelloidon, he says, “is unique in that it is one of the only near-complete skulls of a mammal relative from the basal Cretaceous of North America.” It belonged to a special group near the base of the mammalian family tree, he says, that one day spiraled into our own existence.

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