Najash: the Cretaceous snake that kept its legs

Najash rionegrina is a roughly 90‑million‑year‑old snake fossil from Patagonia that preserved a pelvis and well-developed hindlimbs, and later CT studies found a mix of lizard-like and snake-like skull features indicating prolonged limb retention in some early snakes.

Najash rionegrina is a Cretaceous snake fossil from the Patagonia badlands of Argentina that preserved a pelvis and well-developed hindlimbs. It was first described in 2006 from an approximately 90‑million‑year‑old specimen. A 2019 study using high-resolution CT scans of additional Najash skulls revealed a mix of lizard-like and snake-like features. Together, these findings show that some early snake lineages retained functional hindlimbs for many millions of years. Key findings: - Najash preserved a bony sacrum and well-developed hindlimbs, not merely small vestigial spurs. - Earlier legged snake fossils were often from marine deposits, but Najash comes from Patagonia and differs anatomically in ways that suggest terrestrial functionality. - CT studies of Najash skulls revealed both lizard-like and snake-like elements, including a cheekbone once thought absent in all snakes. - Fossil and genetic evidence indicate limb loss in snakes was gradual, with forelimbs lost earlier and hindlimbs persisting in some lineages for tens of millions of years. - Phylogenetic analyses place Najash outside the crown group of modern snakes, making it a basal branch important for reconstructing early snake anatomy. Summary: Najash's anatomy complicates simple, linear models of snake evolution by showing long-lived hindlimb-bearing lineages alongside the gradual emergence of classic snake features. Its basal placement makes it important for understanding early changes in snake form and function. Undetermined at this time.