Beecheriidae Smirnova, 2004
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publication ID |
https://doi.org/ 10.4202/app.00972.2022 |
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persistent identifier |
https://treatment.plazi.org/id/41708783-FFFA-FF94-8F34-CBF1FE79F967 |
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treatment provided by |
Felipe |
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scientific name |
Beecheriidae Smirnova, 2004 |
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Family Beecheriidae Smirnova, 2004 View in CoL Genus Beecheria Hall and Clarke, 1893
Type species: Beecheria davidsoni Hall and Clarke, 1893 , from the upper Visean Windsor Group of Nova Scotia, Canada .
Remarks.—The genus was established by Hall and Clarke (1893) and then emended by Stehli (1956) to include large terebratulides with dental plates and inner hinge plates converging on a platform separated from the dorsal valve floor by a septum. Beecheria was recorded for the first time in Europe by Brunton (1982, 1984), who assigned to it Terebratula hastata Sowerby, 1824 , from the Arundian (lower Visean) of Great Britain and Ireland, and established the new species Beecheria treakensis Brunton, 1984 , from British Asbian rocks, upper Visean.
Another British species of Beecheria may be Terebratula gillingensis Davidson, 1857 , from the Brigantian (uppermost Visean) of West Gilling, North Yorkshire. From the figures given by Davidson (1858) it is possible to see diverging outer hinge plates and a median septum.
Fig. 17P View Fig .
Material.—Three articulated specimens: MPUM 12092 ( RCC 49-31); MPUM 12093 ( RCC 41-14; RCK 16-3) from mud mound complex of Ricklow Quarry, Monyash, Derbyshire, UK, Monsal Dale Limestone Formation, Brigantian, upper Visean.
Description.—Medium-sized shell, ventribiconvex posteriorly, dorsibiconvex anteriorly. Subpentagonal outline; cardinal margin curved, maximum width at shell mid-length. Anterior commissure uniplicate. Ventral valve flat posteriorly, convex anteriorly. Umbo curved; palintrope anacline. Shallow, rounded sulcus starting at two-thirds shell length. Dorsal valve gently convex posteriorly, flat anteriorly. Umbo straight; palintrope anacline.
Shell smooth. Lamellae occasionally developed, with a spacing of 1.0–2.0 mm.
Dental plates diverging anteriorly forming an angle of 60°, 3.0 mm long. Dorsal valve with divergent outer hinge plates, 1.5 mm long, forming an angle of 90°.
Remarks.—The specimens are transitional in their morphology between the Asbian species Beecheria treakensis and the Brigantian Beecheria gillingensis . From the first species they differ in having a subpentagonal outline, an anteriorly flat dorsal valve and ventral sulcus, while from the latter they differ in having an elongated outline and a more convex, non-resupinate dorsal valve.
Family Gillediidae Campbell, 1965
Subfamily Gillediinae Campbell, 1965
Genus Balanoconcha Campbell, 1957
Type species: Balanoconcha elliptica Campbell, 1957 , from the Watts District of New South Wales, Australia (middle– upper Visean) .
Remarks.—The genus was recognised in Europe for the first time in England by Brunton (1982), who assigned to it Terebratula saccula from the Visean of Great Britain and Ireland on the basis of its internal characters.
Figs. 15C View Fig , 17L–O View Fig .
Material.—Fourteen articulated specimens: MPUM12094 (RCC10-15a); MPUM12095 (RCC300-1); MPUM12096 (RCK15-18); MPUM12097 (RCK15-26); MPUM12098 (RCC10-20; RCC39-2; RCC43-3, 4, 8b; RCC60-50b; RCC65G-3, 20; RCC66-2; RCC67-2). Two ventral valves: MPUM12099 (RCC10-10, 28). All from mud mound complex of Ricklow Quarry, Monyash, Derbyshire, UK, Monsal Dale Limestone Formation, Brigantian, upper Visean.
Description.—Small, elongated ventribiconvex shell with ovatotriangular outline; cardinal margin curved, maximum width at shell mid-length. Anterior commissure rectimarginate. Ventral umbo curved; palintrope anacline. Foramen permesothyrid. Dorsal palintrope anacline.
Shell smooth, with regularly concentric growth lines. Lamellae occasionally developed.
Dental plates and septalium absent. Crural bases diverging from umbo, extending to one-quarter shell length.
Remarks.—The specimens differ from Harttella oakleyi from the mound complex in Ricklow Quarry for their more elongated oval outline, less convex valves, and less recurved ventral umbo. Moreover, adult specimens completely lack a ventral or dorsal sulcus. The specimens are distinguishable from young specimens of Beecheria sp. from the same localities in having an elongate, suboval outline. They can be identified as species of Balanoconcha for their lack of both dental plates and septalium. However, no evidence of sessile hinge plates forming a V-shaped structure was found, so it is not possible to confirm the generic attribution.
Only one species assigned to Balanoconcha is known from the Visean of England: Terebratula saccula , assigned to Girtyella by Muir-Wood (1951) and later assigned to Balanoconcha by Brunton (1982, 1984) on the basis of its internal characters. The specimens here differ from B. saccula in being smaller, in lacking a ventral sulcus and in being less strongly biconvex.
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