Linoprotonia sp.

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 : 896-897

Linoprotonia sp.

Fig. 13E, F .

Material.—Three articulated specimens: MPUM11991 (RCC42-17); MPUM11992 (RCC60-59); MPUM11993 (RCC73-23f). Two fragments: MPUM11994 (RCC73- 30b; RCK15-60). All from mud mound complex of Ricklow

Quarry, Monyash, Derbyshire, UK, Monsal Dale Limestone Formation, Brigantian, upper Visean.

Description.—Medium-sized, transversely semicircular shell. Cardinal margin wide, almost corresponding to maximum width, which is attained anteriorly. Ears moderate, poorly separated. Anterior commissure rectimarginate. Ventral valve regularly convex, weakly geniculated. Trail convex, gently flaring laterally. Umbo strongly enrolled.

Ventral valve surface multicostellate. Ribs cylindrical, straight, with narrow interspaces, increasing in number anteriorly by intercalation. Some ribs may be thicker and wider than neighbouring ones. Ribs number 15 per 5.0 mm, 20.0 mm from the umbo. Three to four prominent, subquadrate, concentric rugae restricted to umbonal flanks. Two symmetrical spine bases scars on umbonal flanks, 7.0 mm from the umbo.

Remarks.—The specimens are similar to both Linoprotonia hemisphaerica from the Asbian, upper Visean, and its ancestor ( Ferguson 1971) L. corrugatohemisphaerica ( Vaughan, 1905) from the Holkerian, middle Visean, of Great Britain. The specimens are close to L. hemisphaerica in their dimensions and outline, but differ from it in having denser radial ornamentation. They share with L. corrugatohemisphaerica the radial ornamentation, though they are larger, they lack the characteristic pointed umbo displayed by L. corrugatohemisphaerica ( Ferguson 1971: pl. 41: 8) and have a more convex ventral valve.

Order Orthotetida Waagen, 1884

Suborder Orthotetidina Waagen, 1884

Superfamily Orthotetoidea Waagen, 1884

Family Pulsiidae Cooper and Grant, 1974

Genus Schellwienella Thomas, 1910

Type species: Spirifera crenistria Phillips, 1836 , from the Visean Pendleside Group of Bowland , Yorkshire, England .

Remarks.—The genus differs from Pulsia Ivanov, 1925 , as this has parallel dental plates; from Meekella White and St. John, 1867 , of the Meekellidae Stehli, 1954 , as this shows dental plates converging on the valve floor.

Schellwienella sp.

Fig. 13I .

Material.—One ventral valve: MPUM 11995 ( RCC 36-12). One fragment: MPUM 11996 ( RCC 128-17b). Both from mud mound complex of Ricklow Quarry, Monyash, Derbyshire, UK, Monsal Dale Limestone Formation, Brigantian, upper Visean.

Description.— Small, ventral shell moderately convex posteriorly, flat anteriorly. Cardinal margin straight, wide. Ventral umbo straight; interarea low, apsacline, asymmetrical. Convex, smooth pseudodeltidium, no monticulus; perideltidium evident. Apical angle 60°.

Ventral valve ornamented by two orders of ribs. Primary ribs have wide flat interspaces, and increase in number anteriorly by intercalation. One to two thinner secondary ribs are present between each pair of primary ribs, starting 10.0 mm from the umbo, increasing in number anteriorly by intercalation, becoming four between each pair of primary ribs at the anterior margin. Weak concentric micro-ornamentation of growth lines.

Short dental plates diverging from each other at 60°. Long bilobed cardinal process, directed postero-ventrally; lobes diverging from each other with an angle of 120°.

Remarks.—The specimen shows an ornamentation which is distinctive of a small number of Western European Schellwienella species: S. cylindrica ( M’Coy, 1844) from the Visean of Castle Espie ( Ireland), S. ornata Demanet, 1934 , from the Visé Formation at Visé ( Belgium), and S. scotica Reed, 1954 , from the Visean of the Midland Valley of Scotland. The specimen differs from S. ornata by having a coarser ornamentation, fewer secondary ribs intercalated between primary ribs, a larger angle of divergence between the dental plates (25° in S. ornata ; Mottequin and Simon 2017) and a broader pseudodeltidium. The specimen strongly resembles S. scotica specimens figured by McIntosh (1974: pl. I: I–N) both in rib density and dental plates divergence angle. However, it is also similar to S. cylindrica , which differs from S. scotica in having a resupinate ventral valve and strongly convex dorsal valve. As the specimen is a ventral valve broken anteriorly, no information about its outline and lateral profile is available. The specimen is thus left in open nomenclature.

Figures

Fig. 13. Echinoconchidae, Linoproductidae, Monticuliferidae, Orthotetida, and Orthida from the Brigantian (uppermost Visean) of Ricklow Quarry, near Monyash, Derbyshire, UK (localities RCC-, RCK-; see Fig. 3). A. Echinoconchus punctatus (Sowerby, 1822), MPUM11976 (RCK15-47) in ventral view. B–D. Pustula cf. pustulosa (Phillips, 1836), B. MPUM11989 (RCC128-17a) dorsal valve external cast. C. MPUM11987 (RCC41-1) in ventral view. D. MPUM11988 (RCC128-7) in ventral (D1) and dorsal (D2) views. E, F. Linoprotonia sp. E. MPUM11991 (RCC42-17) in ventral (E1) and lateral E2) views. F. MPUM11992 (RCC60-59) in ventral view. G. Fluctuaria undata (Defrance, 1826), MPUM11926 (RCC300-14) ventral valve in ventral view. H.?Serratocrista aff. dalriensis McIntosh, 1974, MPUM11997 (RCC10-40) ventral valve in ventral view. I. Schellwienella sp., MPUM11995 RCC36-12) ventral valve in ventral view. J, K. Schizophoria (Schizophoria) cf. connivens (Phillips, 1836). J. MPUM12009 (RCC60-48) in ventral view. K. MPUM12010 (RCC1B-7) dorsal valve in dorsal view. L–O. Schizophoria (Schizophoria.) resupinata (Martin, 1809). L. MPUM12003 (RCC1B-4) dorsal valve in dorsal view. M. MPUM11999 (RCC1B-26) in dorsal view. N. MPUM12004 (RCC1B-25) dorsal valve in dorsal view. O. MPUM12005 RCC36-1a) dorsal valve in dorsal view. Scale bars 10 mm.