Poacites SCHLOTHEIM ex BRONGNIART

Cleal, Christopher J. & Thomas, Barry A., 2018, Nomenclatural Status Of The Palaeobotanical “ Artificial Taxa ” Established In Brongniart’S 1822 “ Classification ” Paper, Fossil Imprint 74 (1 - 2), pp. 9-28 : 21

Poacites SCHLOTHEIM ex BRONGNIART nom. illegit.

Text-fig. 2i

1820 Poacites SCHLOTHEIM , p. 416 (nom. inval.).

1822a Poacites SCHLOTHEIM ex BRONGNIART , p. 210 (nom. illegit.).

Ty p e. Poacites carinata BRONGNIART, 1822a, p. 238 , pl.

3, fig. 2; Loc.: Pennsylvanian Subsystem.

D i a g n o s i s. “Feuilles linéaires, à nervures paralléles.”

D i s c u s s i o n. This generic name was first used by Schlotheim (1820) for fossils he interpreted as being of grass-like leaves but this is invalid as it pre-dated the starting point for taxonomic nomenclature of fossil plants (ICN, Art. 13.1) as well as lacking a generic diagnosis (ICN, Art. 39.1). However, a review of Schlotheim’s (1820) work by Ballenstedt (1821) mentioned one of the species, “ Poacites zeaeformis ” SCHLOTHEIM , accompanied by a brief description: “auf Tafel XXVI [of Schlotheim 1820] zwei Abbildungen von Poacites zeaeformis , welche Grasart mit dem Mais sehr viel Ähnlichkeit hat, verzüglich auf den selteren Exemplaren die noch Stengelblaettern zeigen.” Since this review only mentioned this one species under the generic name Poacites , this species diagnosis may also be used for the genus (ICN, Art. 38.5), thereby validating the publication of the generic name in this review. Nevertheless, the name is in practice unusable as the syntypes (as illustrated in Schlotheim 1820: pl. 26, figs 1, 2) show different types of fossils and the diagnosis is effectively meaningless in identifying a species.

Apparently unaware of Ballenstedt’s (1822) review, Brongniart (1822a) later illegitimately used the generic name Pothocites for a rather different, grass-like fossil, which he named Pothocites carinata BRONGNIART. This looks remarkably like a Carboniferous arborescent lycopsid leaf that today is usually named Cyperites bicarinata LINDLEY et HUTTON, 1832 (e.g. compare with Rex 1983). Although Brongniart (1822a) does not refer to any of the four species described by Schlotheim (1820), he unequivocally attributed the generic name Poacites as he used it to Schlotheim and provided generic a diagnosis very similar to that of Poacites SCHLOTHEIM ex BALLENSTEDT. However , P. carinata is quite different from Schlotheim’s types of Poacites and it would be difficult to see how both could be meaningfully included within the same fossil-genus. Poacites SCHLOTHEIM ex BRONGNIART should therefore be regarded as a later homonym of Poacites SCHLOTHEIM ex BALLENSTEDT and therefore regarded as illegitimate.