Frangula priabonica Doweld, 2017

Doweld, Alexander B., 2017, New names of fossil Atadinus, Endotropis and Frangula (Rhamnaceae), Phytotaxa 321 (2), pp. 194-200 : 196-197

3.6. Frangula priabonica Doweld , sp. nov.

— Frangula hordwellensis Chandler (1961: 131) , nom. inval. (Art. 36.1(a)).

Description:—The fruit pyrenaceous, 6.25 mm long and 4 mm wide, having two pyrenes. Each pyrene containing a single seed closely embraced by the endocarp except the proximal end, subcircular or broadly oboval, much flattened, with marked excavation at the base where the hilar end of the seed projects beyond the endocarp; apex slightly emarginate. One flattened surface with a median longitudinal suture. Endocarp formed superficially of somewhat irregular-sized equiaxial cells, 0.012 –0.016 mm in diam., the smallest towards the base. Inner layers formed of oblique fibres giving a striate appearance. Seeds anatropous with a marginal raphe, agreeing in shape with endocarp. Seed where exposed at the base having a deep hilar excavation, narrowly oval in outline and provided with a low median ridge parallel with the long axis of the excavation and the broad surfaces of the seed. Testa 0.1 mm thick at margin, but 0.05 mm at the middle of a broad surface, formed superficially of convex finely digitate cells about 0.025 mm, columnar in section, the columns having slightly sinuous outlines due to the convexity of these cells piled one upon another. Tegmen thin, finely striate, formed of elongate cells which produce parallel striae [emended after Chandler 1961, 1963].

Type:—V. 42156 (Natural History Museum, London, U.K.) – figured by Chandler (1961: pl. 27, fig. 85).

Geography:—Hordle [Hordwell] Cliffs, South Hampshire, U.K.

Stratigraphy:—Upper Eocene (Priabonian = Headon Hill Formation).

Status:—Fruits (endocarps).

Eponymy:—From Priabonian, a geological stage of the Upper Eocene (known fossil plant record).

IFPNI registration record:— 454EAEFA-4611-4435-940F-46BFA2286C36.

Note:—As Chandler (1961: 131) clearly did not accept the genus Frangula , treating the group as a subgenus of Rhamnus , then she cannot be accepting “ Frangula hordwellensis ” and so the fossil-species was not validly published under Art. 36.1(a). Furthermore, she clearly accepted the assignment of the species to Rhamnus , but failed to definitely associate “ hordwellensis ” with the generic name Rhamnus and so “ Rhamnus hordwellensis ” is not validly published too under Art. 35.2 (cf also Art. 35 Ex. 6). The fossil-species was not also validated later ( Chandler 1963: 100) since she continued to associate “ hordwellensis ” with the subgeneric name Rhamnus subgen. Frangula ( Miller 1754: [517]) Hartig (1851: 482), but explicitly accepted the assignment of the species to Rhamnus . “ Rhamnus hordwellensis ” was just mentioned without validation by Gregor (1977: 213). The fossil-species is validated here with a new epithet “ priabonica ” reflecting the narrow geological time of known plant fossil record. The fossil-species is most likely compared with extant Frangula purshiana .