Productus cf. productus ( Martin, 1809 )

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 : 886

Productus cf. productus ( Martin, 1809)

Fig. 10A .

Material.—One articulated specimen: MPUM11919 (RCC41-3a) from mud mound complex of Ricklow Quarry, Monyash, Derbyshire, UK, Monsal Dale Limestone Formation, Brigantian, upper Visean.

Description.—Medium-sized, elongated concavo-convex shell with suboval outline; cardinal margin wide. Ears large, convex. Both valves geniculated. Anterior commissure rectimarginate. Ventral visceral disc convex, slightly depressed anteriorly in the middle; geniculation angle 120°. Trail straight, long, laterally spreading anteriorly.

Ornamentation consists of low, rounded ribs with narrow subangular interspaces. Ribs increase in number anteriorly by intercalation. They number 12 per 10.0 mm at geniculation and on trail, where some become larger than average and sinuous. Subangular rugae on flanks, fainter on visceral disc, absent from trail. They number 5 per 5.0 mm length.

Remarks.—The specimen is close to P. productus based on the absence of a ventral sulcus, on the laterally spreading trail, and the lack of spine rows on flanks ( Muir-Wood 1928). The density of ribs is similar to the one reported by Muir-Wood (1928: 41).

Figures

Fig. 10. Productidae from the Brigantian (uppermost Visean) of Ricklow Quarry, near Monyash (localities RCC-, RCK-; see Fig. 3) and Wensley Dale, near Matlock (locality WI1; see Fig. 2), Derbyshire, UK. A. Productus cf. productus (Martin, 1809), MPUM11919 (RCC41-3a) in ventral view. B–E. Eomarginifera cf.laqueata (Muir-Wood, 1928). B. MPUM11910 (RCC32-26) in ventral (B1), lateral (B2), and anterior (B3) views. C. MPUM11911 WI1-41) in ventral (C1) and anterior (C2) views. D. MPUM11914 (RCC60-35) dorsal valve interior and external cast. E. MPUM11915 (RCC300-13) dorsal valve external cast. F–L. Antiquatonia hindi (Muir-Wood, 1928). F. MPUM11917 (RCC13-2) in ventral view. G. MPUM11918 (RCC50-1) in anterior view. H. MPUM11920 (RCC123-1) in ventral view. I. MPUM11921 (RCK15-7) in ventral view. J. MPUM11925 (RCC32-6) ventral valve in anterior view. K. MPUM11922 (WI1-19) in ventral (K1), lateral (K2), dorsal (K3), and posterior (K4) views. L. MPUM11923 (WI1-25) in ventral view. M–Q. Antiquatonia aff. hindi (Muir-Wood, 1928). M. MPUM11930 (RCC12-8) in ventral (M1) and posterior (M2) views. N. MPUM11934 (RCC39-19) ventral valve in ventral view.O. MPUM11935 (RCC2-8) dorsal valve external cast. P. MPUM11931 (RCC13-3a) in posterior (P1) and ventral (P2) views. Q. MPUM11932 (RCC32-19) in anterior (Q1) and lateral (Q2) views. Scale bars 10 mm.