Filicites sect. Sphenopteris 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 : 17-18

Filicites sect. Sphenopteris BRONGNIART

Text-fig. 1f, j

1822a Filicites (Sphenopteris) BRONGNIART , p. 233.

1825 “ Sphaenopteris ” (BRONGNIART) STERNBERG, Tentamen p. xv.

Ty p e. Filicites (sect. Sphenopteris) elegans BRONGNIART, 1822a, p. 233 , pl. 2, fig. 2; Loc.: Waldenburg Formation (Serpukhovian Stage), Upper Silesia; ≡ “ Sphaenopteris ” elegans (BRONGNIART) STERNBERG, 1825 , Tentamen p. xv.

D i a g n o s i s. “pinnules cunéiformes, arrondies ou lobées à l’extrémié, et les nervures palmées ou rayonnantes de la base de la pinnule.”

D i s c u s s i o n. It is incorrectly stated in the International Fossil Plant Names Index (http://fossilplants.info/) that the first use of Sphenopteris as a genus is in Sternberg (1823: 36), but Sternberg clearly stated that he regarded it here as a section (“Abteilung”) and earlier (p. 27) that it was of Filicites . The first use of Sph(a)enopteris as a generic name is in the 1825 Tentamen of Sternberg. Although when first used as a generic name the spelling was altered to Sphaenopteris by Sternberg (1825), the original orthography of Brongniart’s (1822a) section must be retained (ICN, Art. 60.1).

This is one of the most confused of the Brongniart fossil-taxa, and is still regularly used for both fern and seedplant fossil-species. However, the type ( S. elegans ) is welldocumented as a Mississippian-age early seed-plant (e.g. Kidston 1923 -1925: 242) and so the name Sphenopteris should only be applied to this group of early seed-plant fronds. It should be noted in passing that Kidston adopted for this species the taxonomic synonym Diplotmema adiantioides (SCHLOTHEIM ex POTONIÉ) GOTHAN, 1913 (≡ Cuneatopteris adiantoides SCHLOTHEIM ex POTONIÉ, 1907, p. 2 ) since the first use of the species epithet (as “ Filicites adiantoides ” SCHLOTHEIM, 1820 ) pre-dated both Brongniart’s and Sternberg’s works. However, as “ F. adiantioides ” was published prior to the starting point for publication of fossiltaxa (ICN, Art. 13.1) this must be rejected.

This raises a practical problem with classifying some fossil fern fronds with small lobed pinnules, especially of Palaeozoic age. Although there are numerous welldefined fossil-genera for such ferns (e.g. Renaultia ZEILLER, 1883 , Zeilleria KIDSTON, 1884 ) these are diagnosed by their reproductive structures. Those species for which reproductive structures are unknown have tended to be placed in Sphenopteris (e.g. Brousmiche 1983) but this is not tenable given that the type of that name is a seed-plant. There is in fact no available legitimate name for a fossilgenus of species of such fern fossils for which reproductive structures are unknown. It would be possible to establish an “artificial” genus for such species; this would be analogous to the fossil-genus Taeniopteris BRONGNIART, 1828a nom. cons., which is now used for entire cycadophyte-like leaves for which neither cuticles nor reproductive structures are known (van Konijnenburg-van Cittert et al. 2017). However, to date no such fossil-genus has been established for these fern fossils.Another option would be to revert to Brongniart’s (1822a) original conception for Sphenopteris as including all pteridophyllous foliage with lobed pinnules and supressing names such as Renaultia and Zeilleria but this would seem a retrograde step. The only viable option within the current framework of the ICN is to make a judgement as to the taxonomic position of such species based on similarities in the morphology of the sterile foliage, maybe using an open-nomenclature-like qualifier similar to that used in palaeozoology ( Matthews 1973, Bengtson 1988).

In passing, mention should be made of a later homonym of S. elegans , Sphenopteris elegans (YOKOYAMA) ÔISI, 1940 (≡ Onychiopsis elegans YOKOYAMA, 1895 ) based on a type from the Lower Cretaceous Series of Japan.