Geniculifera keyserlingiana (De Koninck, 1843)

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 : 884-885

Geniculifera keyserlingiana (De Koninck, 1843)

Fig. 9L .

1843 Productus keyserlingiana ; De Koninck 1843: 200, pl. 10: 8.

1847 Productus keyserlingianus De Koninck, 1843 ; De Koninck 1847: 239, pl. 14: 6.

1862 Productus keyserlingianus De Koninck, 1843 ; Davidson 1862 a: 174, pl. 34: 15–16.

1991 Geniculifera keyserlingiana (De Koninck, 1843) ; Brunton and Tilsley 1991: 291.

1993 Geniculifera keyserlingiana (De Koninck, 1843) ; Brunton et al. 1993: 114, figs. 61–71.

2000 Geniculifera keyserlingiana (De Koninck, 1843) ; Brunton et al. 2000: fig. 304.

Material.—One articulated specimen: MPUM 11905 ( RCC 73-28) from from mud mound complex of Ricklow Quarry, Monyash, Derbyshire, UK, Monsal Dale Limestone Formation, Brigantian, upper Visean.

Description.—Small, elongated concavo-convex shell with semi-elliptical outline; cardinal margin corresponding to the maximum width. Ears small, convex, poorly separate. Cardinal angles right. Both valves geniculated. Corpus cavity deep. Anterior commissure rectimarginate. Ventral visceral disc moderately convex; geniculation angle about 90°. Trail long; flanks steep. Dorsal visceral disc slightly concave posteriorly, more concave anteriorly. Flat ears. Geniculation angle 90°. Trail long. Fold and sulcus absent.

Ornamentation consists of low, rounded, circular spine bases covering the ventral visceral disc, quincuncially arranged. Broad (1.0 mm), low, rounded costae with flat wide interspaces on ventral trail. Dorsal valve covered by low, rounded rugae; they number four per 3.0 mm length. Micro-ornamentation of concentric growth lines on both valves.

Remarks.—The specimen differs from Geniculifera boonensis (Branson, 1938) in having more numerous prominent swollen spine bases on the ventral visceral disc and weaker concentric ornamentation.

Figures

Fig. 9. Productellidae and Productidae from the Brigantian (uppermost Visean) of Ricklow Quarry, near Monyash, Derbyshire, UK (localities RCC-, RCK-; see Fig. 3). A–E. Krotovia spinulosa (Sowerby, 1814). A. MPUM11886 (RCC73-22a) in ventral view. B. MPUM11889 (RCC3-18) dorsal valve interior and external cast. C. MPUM11891 (RCK15-16) interior and external cast. D. MPUM11892 (RCK15-28) dorsal valve interior and external cast. E. MPUM11887 (RCK15-10) in ventral view. F–K. Breileenia radiata Brunton in Brunton and Lazarev, 1997. F. MPUM11895 (RCC65-1) in anterior (F1), ventral (F2), and lateral (F3) views. G. MPUM11898 (RCC12-1) dorsal valve external cast. H. MPUM11899 (RCC12-7) dorsal valve interior and external cast. I. MPUM11900 (RCC12-15) dorsal valve external cast. J. MPUM11903 (RCC38A-2) fragment in anterior view. K. MPUM11901 (RCC12-23b) dorsal valve external cast. L. Geniculifera keyserlingiana (De Koninck, 1843), MPUM11905 (RCC73-28) in antero-ventral (L1), lateral (L2), and dorsal (L3) views. M. Limbifera sp., MPUM11890 (RCC54-10b), ventral valve in ventral view. N. Carringtonia cf. carringtoniana (Davidson, 1862a), MPUM11906 (RCC2-51) dorsal valve interior and external cast. O. Productus sp., MPUM11908 (RCC1-61b) in ventral view. P. Productus sp., MPUM11909 (RCC60-6) dorsal valve external cast.