Sphenophyllum tenerrimum ETTINGSH. ex HELMHACKER , 1874

Sphenophyllum tenerrimum ETTINGSH. ex HELMHACKER, 1874

emend. by Stur (1877)

Text-fig. 6a View Text-fig

1874 Sphenophyllum tenerrimum ETTINGSH. ex HELMHACKER , p. 50, pl. 3, figs 5–16.

1877 Sphenophyllum tenerrimum ETTINGSH. ex HELMHACKER ; Stur, p. 108, pl. 7, figs 1–14. (?Ettingshausen’s types)

1969 Sphenophyllum tenerrimum ETTINGSH. ex HELMHACKER ; Crookall, p. 602, pl. 108, fig. 6.

D e s c r i p t i o n. Ribbed stems with whorls of 9–12 leaves borne at about right-angles in proximal part of stem, but more obliquely in more distal positions. Leaves 3–10 mm long, deeply incised into 2–4 narrow-linear, splayed segments, the incisions usually extending about a half of the leaf length, each segment with a blunt apex. Occasionally the leaf segments divide for a second time. Leaf surface striate.

R e m a r k s. This is the most commonly-reported Sphenophyllum species found in lower Namurian macrofloras and is easily recognised by its whorls of deeply-incised leaves with splayed segments (e.g., Storch 1980, Havlena 1982, Terreaux de Felice et al. 2019). However, there are nomenclatural issues with the species epithet. According to Stur (1877) it was first used in manuscript but not published by Ettingshausen in 1853, and was mentioned by Stur (in Foetterle 1868: 50) in a species list but without description or illustration. The name S. tenerrimum was first validly used by Helmhacker (1874) who included a description and illustrated several specimens, although most of those specimens are now reported lost ( Jongmans 1911). Nevertheless, Helmhacker made clear reference to Ettingshausen’s specimens, which were later illustrated by Stur (1877), and so these can be legitimately taken as syntypes; Helmhaker’s publication of the name was therefore valid.

An added complication is that Helmhacker (1873) had earlier referred to the specimens he figured in his 1874a paper as Sphenophyllum binatum HELMACKER. However , this was a nomen nudum with no accompanying description or illustration, and so invalid.

This species is very similar to the upper Carboniferous Sphenophyllum trichomatosum STUR , but the leaves of the latter have segments with a more acute apex and the leaf surface tends to be smooth (non-striate) ( Jongmans 1911).

O c c u r r e n c e. Ca. 10 m below Orchard Limestone, (Upper Limestone Formation), Robroyston Colliery, Lanarkshire.