Early Jurassic
The oldest remains of modern horsetails of the genus "Equisetum" first appear in the Early Jurassic, represented by "Equisetum dimorphum" from the Early Jurassic of Patagonia and "Equisetum laterale" from the Early to Middle Jurassic of Australia. Silicified remains of "Equisetum thermale" from the Late Jurassic of Argentina exhibit all the morphological characters of modern members of the genus. The estimated split between "Equisetum bogotense" and all other living "Equisetum" is estimated to have occurred no later than the Early Jurassic.