Origin of Equisetum: Evolution of horsetails (Equisetales) within the major euphyllophyte clade Sphenopsida

Elgorriaga and colleagues infer progressive size reduction and compact strobili along the Equisetaceae plus Neocalamites lineage, with modern-horsetail-like character combinations present by Jurassic times; this is a topology-dependent trend, not a body plan shared by all Equisetopsida.

A combined living-and-fossil character analysis places Equisetum within sampled sphenopsids and reconstructs horsetail transitions; this is a matrix-dependent topology, not an Equisetopsida origin date.

Equisetopsida is displayed at 372.2–0 Ma only as a Sphenopsida/Equisetopsida Devonian-to-living navigation lineage; it is not a crown-Equisetum origin date, direct-ancestor chain or claim that one species persisted throughout.