(2683) Proposal to conserve the name Leptopteris C. Presl (Osmundaceae, Pteridophyta) against Leptopteris Brongn. (Fossil Plants)

Abstract

Leptopteris C. Presl, Suppl. Tent. Pterid.: 70. 1845 (sero), nom. cons. prop. Typus: L. fraseri (Hook. & Grev.) C. Presl (Todea fraseri Hook. & Grev.). Leptopteris Brongn., Hist. Vég. Foss. 1: 149. 23 Nov 1829, nom. rej. prop. Typus: non designatus. Leptopteris Brongn. (Hist. Vég. Foss. 1: 149. 1829) non C. Presl (Suppl. Tent. Pterid.: 70. 1845) was recovered only recently when contributing to the International Fossil Plant Names Index (IFPNI; http://fossilplants.info/about), a recently initiated global registry of the scientific names of fossil plants, algae, fungi and prokaryotes traditionally covered by the International Code of Nomenclature for algae, fungi, and plants (Turland & al. in Regnum Veg. 159. 2018). As recorded in IFPNI, fossil Leptopteris Brongn. (non C. Presl) is based on foliage with no further description of fossil-species. Brongniart created the fossil-genus, providing a generic diagnosis in clavi in his sketch of the classification of fossil ferns and a single illustration (pl. 31, fig. 1), but evidently later abandoned it, since no fossil-species were described under this generic name. In his subsequent Histoire des végétaux fossiles (Part 4), published on 1 Feb 1830, nearly a year later, in a discussion of the fossil sphenopterid foliage, Brongniart admitted the resemblance between the fossil-species Sphenopteris nervosa Brongn. (Hist. Vég. Foss. 1: 174. 1830) and (sic!) “plusieurs espèces d’Adianthum (pl. XXXI, fig. 1); mais dans les Adianthum les folioles sont presque toujours pédicellées et plus espacées, et leur texture est plus mince qu'elle ne le paraît dans la plante fossile”. From this Brongniart's original comment we could conclude that it is possible that Leptopteris Brongn. with the adiantoid type of venation, demonstrated in the figure accompanying the original diagnosis, is no more than a fossil generic counterpart of extant Adiantum L. (Sp. Pl.: 1094. 1753): “distingue ces feuilles et permettraie d'en former un groupe distinct (Leptopteris), si on les retrouvait à l’état fossile” (Brongniart, l.c. 1830: 170). However, Leptopteris Brongn. became a “nomen oblitum & dubium” even in Brongniart's original monograph on fossil plants (though unfinished), with no further descriptions or illustrations. Unfortunately, no authentic originals have been found in Brongniart's collections (Muséum National d'Histoire Naturelle, Paris, France); judging from the single foliage illustration it could not be attributed with certainty to either the ferns or pteridosperms. In any case, the valid publication of Leptopteris cannot be questioned in terms of current nomenclatural rules, and this fossil-generic name is an obstacle to the continued use of its junior homonym, Leptopteris C. Presl (l.c.), for extant osmundaceous ferns. This nomenclatural situation, with Leptopteris validated on fossil material before publication of the widely known extant osmundaceous genus has been overlooked by all subsequent researchers on fern taxonomy (Bobrov in Bot. Zhurn. (Moscow & Leningrad) 52: 1609. 1962; Miller in Contr. Mus. Paleontol. Univ. Michigan 23: 105. 1971; Kramer in Kubitzki, Fam. Gen. Vasc. Pl. 1: 200. 1990; Yatabe in J. Pl. Res. 112: 397. 1999; Grimm & al. in Syst. Biol. 64: 396. 2014; Bomfleur & al. in PeerJ 5: e3433. 2017). The aim of the proposal is to fix the status quo, i.e., to legitimize the modern wide usage of the illegitimate later homonym Leptopteris C. Presl, with six extant recognized species aggregated in four series (Bobrov, l.c.), by conservation against its senior homonym, the fossil Leptopteris Brongn. Otherwise, a new name for the extant osmundaceous genus and their associated fossil forms based on foliage, cones and pollen would be required which would lead to destabilization of modern fern nomenclature by the necessary transfer of the species names of six extant and three fossil-species (two based on dispersed spores and one on fossil stems) into a new genus (no heterotypic generic synonyms are known). ABD, https://orcid.org/0000-0003-0089-5919 I thank John McNeill for suggestions on and corrections to the initial draft. It is a pleasure to thank Valentina Bublik (Fundamental Botanical Library of the National Institute of Carpology, Moscow) for bibliographic assistance. The research is a contribution to the Palaeoflora Europaea Project, Palaeoflora of Russia (Palaeoflora Rossica) Project (NOM-19-150) and The International Fossil Plant Names Index (IFPNI; http://fossilplants.info/).