Researchers Discover 165-million-year old Mammalian Ancestor

Researchers have now discovered a 165-million-year-old proto-mammal fossil. The relic shows that animals had developed fur and hair before the evolution of true mammals.

The ancient mammalian relative is named Megaconus mammaliaformis and its biological features are described by University of Chicago scientists.

The fossil was discovered in Inner Mongolia and is believed to have existed along with feathered dinosaurs, about 100 million years before the arrival of Tyrannosaurus Rex.

"We finally have a glimpse of what may be the ancestral condition of all mammals, by looking at what is preserved in Megaconus. It allows us to piece together poorly understood details of the critical transition of modern mammals from pre-mammalian ancestors," said Zhe-Xi Luo, professor of organismal biology and anatomy at the University of Chicago.

Megaconus was a land-dwelling animal about the size of a large ground squirrel. Its jaw and dental structures show that it was most probably an omnivore, eating leaves and insects and also possibly smaller vertebrates.

The presence of fur and hair is the most distinctive feature of the animal as it is only the second pre-mammalian animal to have fur. Researchers found that the animal had sparse hair around its abdomen. Megaconus even had a long keratinous spur, which was probably poisonous, on its hind legs. These spurs are even found in present-day male platypus, which is why researchers believe that the specimen could have been a male.

"Megaconus confirms that many modern mammalian biological functions related to skin and integument had already evolved before the rise of modern mammals," said Luo, who was also part of the team that first discovered evidence of hair in pre-mammalian species in 2006 (the article was published in Science).

The skeleton, especially the hind legs, show that the animal walked like the modern-day armadillo.

Some features in Megaconus are that of reptiles such as a primitive middle ear that was attached to the jaw.

"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," Luo said in a news release.

The study is published in the journal Nature.