In the Fayum desert of northern Egypt, not too far from the banks of the Nile, the vestiges of ancient forests are preserved in the sand-covered strata. The fossils are ghosts of a vanished oasis in which prehistoric cousins of modern elephants wallowed in lush wetlands and a host of ancient primates scrambled through the trees, and despite being known as one of the world's best fossil sites for over a century paleontologists are continuing to discovery new species from the desert rock. The trouble is that not all these new species are easily classified.
Approximately 37 million years ago,…