The fossilized remains of a previously-unknown species of primate have been unearthed in central China. At 55-million years old, it is the oldest known primate skeleton ever discovered, and harbors tantalizing clues about a pivotal branching point in humanity’s evolutionary lineage.
Top image: CAS/Xijun Ni
Researchers have dubbed the newly identified primate Archicebus achilles, a name chosen to highlight the creature’s interesting heel anatomy (which we’ll get to in a moment), rather than its heroic proportions. In fact, Archicebus was actually quite small. Estimates put its weight at somewhere between 20 and 30 grams. Held in the palm of your hand, a specimen on the upper end of that range would have had roughly the same heft as $1.25 in quarters.
That makes Archicebus one of the tiniest primates to ever live (smaller, even, than the pygmy mouse lemur – the world’s tiniest living primate); but the combination of its diminutive size, its unprecedented age and its unique body plan make it one of the most fascinating evolutionary discoveries in recent memory.