New research from a collaboration between Argentinian and University of Alberta and McGill University palaeontologists adds a new piece to the puzzle of snake evolution.

The researchers examined a strikingly well-preserved fossil of the rear-limbed snake Najash rionegrina, found in Argentina. The study shows that nearly 100 million years ago, these legged snakes still had a cheekbone—also known as a jugal bone—that has all but disappeared in their modern descendants.