Ever wonder what northern China looked like 160 million years ago?

Imagine lush jungle. Flitting insects. Massive dinosaurs. And four-legged fluff balls. The fluff balls—also called docodonts—were some of the earliest known mammals.

And at least two of them drowned.

A few years ago, farmers discovered two fossilised skeletons in the remains of an ancient lake. The animals’ tiny skeletons were stuck in slabs of rock.

The farmers delivered the fossils to a team of scientists, who used CT scans—like we use for human medicine—to work out what was inside the stone.

And…success! They uncovered two new species of fluff ball!

And…surprise! The two species lived very different lifestyles. Until this discovery, we’d assumed early mammals were all pretty much alike: too busy escaping dinosaurs to do much adapting.

These two species appear to have evolved in much the same way as modern mammals.

Agilodocodon scansorius (named for its agility and climbing adaptation)
Length: around 13–14cm
Weight: anywhere from 27–40 grams (around the same as a mouse)
Ate: tree sap and gum
Most like: a long-nosed squirrel

• Oldest known tree-climbing mammal
• Used its long, curved claws and flexible elbows and wrists to race up trees, like squirrels and monkeys
• Fingers and limbs were in proportions typical of modern climbing mammals
• Used its chisel-like teeth to gnaw through tree bark and feasted on sap and gum

Docofossor brachydactylus (named for its digging adaptation and stubby fingers)
Length: around 7–9cm
Weight: less than 17 grams (around half a mouse)
Ate: insects
Most like: an African golden mole

• Oldest known burrowing mammal
• Used its shovel-like paws and stumpy fingers to dig
• Had stubby, wide teeth like modern mammals that hunt underground
• Had a wide, flat body suited to scurrying through tunnels.

*I wrote this story for CSIRO’s Scientriffic magazine, now Double Helix.

* And I’m sorry I haven’t posted in ages…I’ve been busy on some secret projects. Hopefully details can be revealed soon….