Molecular clock
The oldest known members of the genus are from the Early Cretaceous around 125 million years ago, with records being known from the Aptian-Albian of Argentina,China, Portugal and the United States. The fossil record of "Ephedra" outside of pollen disappears after the Early Cretaceous. Molecular clock estimates have suggested that last common ancestor of living "Ephedra" species lived much more recently, during the Early Oligocene around 30 million years ago. However, pollen modified from the ancestral condition of the genus with branched pseudosulci (grooves), which evolved in parallel in the living North American and Asian lineages is known from the Late Cretaceous, suggesting that the last common ancestor is at least this old.