Sinuites ramseyensis ( Hicks, 1873 )

Ebbestad, Jan Ove R. & Cope, John C. W., 2021, A low diversity Sinuites gastropod community from the Floian, Early Ordovician, of South Wales, Acta Palaeontologica Polonica 66 (2), pp. 319-335 : 323-324

Sinuites ramseyensis ( Hicks, 1873)

Fig. 3 .

1873 Bellerophon ramseyensis sp. nov.; Hicks 1873: 50, pl. 3: 30–32.

Material.— Fifty­five specimens, NMW 2017.15 G.3–57, preserved as variably compressed internal moulds. From the Dan­lan­y­Castell quarry, Carmarthen , Wales, UK. Merlinia selwynii Trilobite Zone, Moridunian regional Stage (lower Floian Stage, Fl 1) .

Description.—Specimen length is 10–20 mm. The whorl profile is heart­shaped with height and width being about equal ( Fig. 3D ). The wide and U­shaped median sinus stretches about 1/3 of a whorl back from the aperture. The typical lateral anterior lobes are sub­angular and at the aperture the lateral lip seem to connect with a lateral­umbilical ridge. A small patch in specimen NMW 2017.15G.7 preserves ornamentation near the umbilical area about 2/3 of a whorl back from the preserved aperture. Fine, slightly wrinkled lines are expressed on the external imprint and may represent subinductural deposits ( Fig. 3E ) (Horný 1996).

Remarks.— Hicks (1873) described Bellerophon ramseyensis from the Ogof Hên Formation at Ramsey Island and St David’s in Pembrokeshire, south­west Wales, which is identified as a species of Sinuites (images available on the British Geological Survey homepage: http://www.3d­fossils. ac.uk/). The units in Pembrokeshire are the lateral equivalent to those of the Llangynog Inlier discussed herein Fortey and Rushton 2000). Preservation of the Sinuites specimens in the two areas appears quite similar, and as a matter of convenience they may be regarded as constituting the same species.

With around 50 specimens Sinuites is the most abundant taxon in the present material. Deformation does not allow a full appreciation of the morphology, but there is no reason to assume that more than one species is present.

Stratigraphic and geographic range.—Ordovician; world wide.

Figures

Fig. 3. Sinuitid bellerophontid Sinuites ramseyensis (Hicks, 1873) from the Floian, Lower Ordovician Bolahaul Member of the Ogof Hên Formation, Danlan­y­Castell quarry, Wales, UK. A. NMW 2017.15G.3, deformed shell in left lateral (A1), posterior oblique (A2), and anterior oblique (A3) views. Note the twisted and compacted median sinus seen as a line inA1 and A3. B. NMW 2017.15G.4, anterolateral shield in right lateral view.C. NMW 2017.15G.5, large, slightly dorso­ventrally flattened specimen in left lateral (C1) and dorsal (C2) views, showing median anterior sinus well. D. NMW 2017.15G.6, natural cross section in ventral view, showing the shape of the whorls. E. NMW 2017.15G.7, specimen in left lateral view (E1), showing the external mould of the initial whorls and the internal mould of the last whorl; details of the ornamentation as seen on the external mould (E2). Scale bars 5 mm.