A review of the nomenclature of Cyclostigma (Cyclostigmatales: Cyclostigmataceae; fossil Isoetophyta)

Abstract

AbstractThe complicated nomenclatural history of the extinct genus Cyclostigma Haught., established for arborescent trunks of presumably ancient isoetopsids (Isoetophyta: Cyclostigmatales), is reviewed and corrected with newly found bibliographic and historical data. The fossil name Cyclostigma, an illegitimate later homonym of two extant angiosperm genera, Cyclostigma Hochst. ex Endl. (Apocynaceae) nec Cyclostigma Klotzsch (Euphorbiaceae), was recently conserved and listed in App. III of ICN since the XVIII IBC in 2011. The fossil generic name Cyclostigma, associated with three species epithets and a distinct fossil family name Cyclostigmataceae (“Cyclostigmeae”), was invalidly published by Haughton in his series of works of 1859 and 1860 (reprinted several times), the genus lacking a description. Haughton’s family name based on his “Cyclostigma” and the species published in this genus were also not validly published. However, the generic name Cyclostigma was validly published in a little‐known publication by Haughton in 1859, not by Heer in 1871, as generally accepted in modern systematic palaeobotany, or Baily in 1861. In course of thorough nomenclatural analysis it has been shown that three fossil species names, which fell into oblivion still in the early works in the 19th century, Sigillaria dichotoma Haught. 1855, Lepidodendron griffithii Brongn. 1857 and L. minutum Haught. 1855 (non Sauveur) have priority over Cyclostigma kiltorkense Haught. 1859. Since C. kiltorkense has entered solidly into systematic palaeobotany and served as an index marker in historical geology, its retention through conservation is proposed. The nomenclature of the name Cyclostigmataceae is corrected as to be first validly published by Haughton in 1860.