'Jurassic squirrel' fossil: Hair came before mammals

A newly discovered fossil of the Megaconus mammaliaformis, a "Jurassic squirrel" that roamed the earth 165 million years ago, shows that the traits of hair and fur existed before mammals.

Scientists discovered the fossil of an ancient proto-mammal. The Megaconus mammaliaformis offers evidence that hair and fur evolved before the first mammals.

At 165 million years old, the fossil is far older than a T-Rex, but the extinct lake bed in Mongolia, where the Megaconus mammaliaformis was found, preserved the specimen in so much detail that a distinct halo of hair around the specimen was visible. Now, research published in the journal Nature suggests that fur coats have been around for a long time — longer than the mammals that now sport them.

Appearance-wise, the Megaconus mammaliaformis has been described as a "Jurassic squirrel." This proto-mammal's anklebones, middle ear, and vertebral column are all reptilian in nature, but its teeth and jaw hinge are very similar to those found in modern mammals, especially rodents. Analysis of its skeleton suggests that it walked like an armadillo and had long keratinous spurs on the ends of its back feet, similar to those found today on male platypuses.

The Megaconus would have roamed a world without flowers, which hadn't emerged yet, but teeming with feathered dinosaurs. Its fur may have evolved as a way to stay warm during nocturnal hunts, when warm-blooded foragers would have an advantage over sluggish, cold-blooded reptilians.

Related: 23-million-year-old lizard fossil found in Mexico

Zhe-Xi Luo, one of the researchers from the University of Chicago who studied the specimen, said, "We cannot say that Megaconus is our direct ancestor, but it certainly looks like a great-great-grand uncle 165 million years removed. These features are evidence of what our mammalian ancestor looked like during the Triassic-Jurassic transition," according to the university's newspaper.

The oldest known specimen of a true mammal is about 160 million years old. It appears to have been a shrew-like animal that lived off insects snagged from the ferns that lined the shores of freshwater lakes.

Megaconus is one of two fossils found that shows evidence of hairy pre-mammals. The first, found in 2004 in the same location as Megaconus, is a small semi-aquatic mammal, also about 164 million years old.  It is believed to have looked something like a beaver. 

Related: Scientists decode DNA of 'living fossil' fish


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