Angiospirifer bisulcatus ( Sowerby, 1825 )

Carniti, Alessandro P., Porta, Giovanna Della, Banks, Vanessa J., Stephenson, Michael H. & Angiolini, Lucia, 2022, Brachiopod fauna from uppermost Visean (Mississippian) mud mounds in Derbyshire, UK, Acta Palaeontologica Polonica 67 (4), pp. 865-915 : 903

Angiospirifer bisulcatus ( Sowerby, 1825)

Fig. 14P–S .

1825 Spirifer bisulcatus ; Sowerby 1825: 152, pl. 494: 1–2.

1858 Spirifera bisulcatus Sowerby, 1825 ; Davidson 1858: 31 (pars), pl. 4: 1; pl. 5: 1; pl. 6: 1–9, 13–17; pl. 7: 4.

1991 Spirifer bisulcatus Sowerby, 1825 ; Brunton and Tilsley 1991: 293.

2008 Spirifer bisulcatus Sowerby, 1825 ; Legrand-Blain 2008: pl. 3: 1–2.

2011 Angiospirifer bisulcatus ( Sowerby, 1825) ; Angiolini et al. 2011: 74, figs. 1, 2, 6A–I. (cum syn.)

Material.—Four articulated specimens: MPUM 12031 (WI1-10); MPUM 12032 (WI1-12a); MPUM 12033 (WI1-30); MPUM 12034 (WI1-39). Two ventral valves: MPUM 12035 (WI1-11); MPUM 12036 (WI1-36). All from Wensley Dale, Matlock, Derbyshire, UK, Eyam Limestone Formation, upper Brigantian, upper Visean.

Description.—Medium-sized, ventribiconvex shell with semicircular outline; cardinal margin straight, slightly less or corresponding to the maximum width. Cardinal angles acute to obtuse, cardinal extremities subangular. Anterior commissure uniplicate. Ventral interarea apsacline, denticulate. Low, rounded sulcus starting near umbo, widening and deepening anteriorly, extending in a subrounded tongue at the commissure. Dorsal interarea orthocline, very low. High, subrounded fold starting 5.0 mm from umbo, widening and increasing in height anteriorly.

Ornamentation consists of coarse, rounded, simple costae with narrow, rounded interspaces. Costae number 4–5 per 10.0 mm at the anterior commissure. Ventral sulcus with five ribs: one mesial costa widening anteriorly, not distinctly larger than lateral ones, which derive from bifurcation near the umbo of the sulcus-bounding costae. Fold with four indistinct ribs. Irregularly spaced lamellae covering both valves.

Remarks.—The specimens are close to Angiospirifer bisulcatus in their morphology and ornamentation. They differ from A. trigonalis in having a lower and more rounded dorsal fold, in having a regularly semicircular outline, rather than subtriangular, and in lacking a median sulcal costa widening and thickening anteriorly with respect to the lateral ones. However, the specimens lack the sulci bordering the fold which characterize most dorsal valves of A. bisulcatus .

Stratigraphic and geographic range.— Angiospirifer bisulcatus is recorded in the upper Tournaisian–Visean of England and Ireland and the Visean of Belgium ( Brunton and Tilsley 1991; Angiolini et al. 2011; this study).

Figures

Fig. 14. Rhynchonellida and Spiriferida from the Brigantian (uppermost Visean) of Ricklow Quarry, near Monyash (localities RCC-, RCK-; Fig. 3) and Wensley Dale, near Matlock (locality WI1; Fig. 2), Derbyshire, UK. A–G. Pleuropugnoides pleurodon (Phillips, 1836). A. MPUM12011 (RCC49-22) in dorsal (A1) and anterior (A2) views. B. MPUM12013 (RCK15-4) in ventral (B1) and dorsal (B2) views. C. MPUM12017 (RCK15B-3) in ventral (C1), dorsal (C2), and anterior (C3) views. D. MPUM12015 (RCK15-19) in ventral (D1) and dorsal (D2) view. E. MPUM12014 (RCK15-15) in lateral (E1), ventral (E2), and posterior (E3) views. F. MPUM12012 (RCC73-9) in lateral (F1), ventral (F2), posterior (F3), and anterior (F4) views. G. MPUM12016 RCK15-29) in ventral (G1), dorsal (G2), and anterior (G3) views. H–L. Propriopugnus pugnus (Martin, 1809).H. MPUM12021 (RCC2-55) in dorsal view.. MPUM12022 (RCC3-7) in dorsal (I1) and anterior (I2) views. J. MPUM12024 (RCC73-22b) in ventral (J1) and anterior (J2) views. K. MPUM12026 RCC60-4d) dorsal valve in dorsal view. L. MPUM12028 (WI1-33) in dorsal view. M.?Fusella sp., MPUM12037 (RCC128-5) ventral valve in ventral view. N, O. Martiniinae gen. et sp. indet. N. MPUM12065 (RCC2-58a) ventral valve in ventral view. O. MPUM12066 (WI1-32) ventral valve in ventral view.P–S. Angiospirifer bisulcatus (Sowerby, 1825). P. MPUM12032 (WI1-12a) in ventral view. Q. MPUM12035 (WI1-11) ventral valve in ventral view. R. MPUM12031 (WI1-10) in lateral (R1), dorsal (R2), ventral (R3), anterior (R4), and posterior (R5) views. S. MPUM12033 (WI1-30) in lateral (S1), dorsal S2), ventral (S3), anterior (S4), and posterior (S5) views. T–V. Latibrachythyris cf. crassa (De Koninck, 1843). T. MPUM12039 (RCC1-34a) ventral valve in ventral view. U. MPUM12038 (RCC1-21) ventral valve in ventral view. V. MPUM12041 (RCC54-17a) ventral valve in ventral (V1) and posterior (V2) views. Scale bars 10 mm.