sphenopsid

noun

sphe·​nop·​sid sfi-ˈnäp-səd 

: any of a class or division (Sphenopsida or Sphenophyta) of primitive vascular plants characterized by jointed ribbed stems, small leaves usually in whorls at distinct stem nodes, and sporangia in sporangiophores and made up of the horsetails and extinct related forms

Word History

Etymology

ultimately from Greek sphēn wedge + New Latin -opsis

First Known Use

1957, in the meaning defined above