Voiseyella cf. texana ( Carter, 1967 )

Sun, Yuanlin & Baliński, Andrzej, 2011, Silicified Mississippian brachiopods from Muhua, southern China: Rhynchonellides, athyridides, spiriferides, spiriferinides, and terebratulides, Acta Palaeontologica Polonica 56 (4), pp. 793-842 : 829-830

Voiseyella cf. texana ( Carter, 1967)

Fig. 27G–J .

Material.—Four incomplete ventral and two incomplete dorsal valves from sample GB, and one incomplete ventral valve from GT.

Description.—This small and fragmentary material reveals quite satisfactory the detail of the internal shell structure as well as external shell ornamentation and micro−ornamentation. The species is characterised by strongly extended laterally shell, with pointed mucrons, narrow but quite deep ventral sulcus bounded laterally by a pair of very thick and high costae, very prominent dorsal fold delimited by deep intercostal furrows and bearing a faint medial groove, simple rounded lateral costae, prominent ventral umbo with incurved beak overhanging the apex of the delthyrium, and having strongly developed imbricate concentric lamellae. Dental adminicula are anteriorly diverging, thin, follow margins of sulcus, or are extrasinal ( Fig. 27J 2). In ontogenetically old specimens ventral valve becomes thick posteriorly and thickened dental adminicula occlude apical region of the delthyrium. Dental adminicula embrace posterior part of the

http://dx.doi.org/10.4202/app.2010.0106

longitudinally striated muscle scars which are deeply impressed posteriorly, weakly delimited anteriorly, and medially divided by a thin ridge ( Fig. 27J 2). On some ventral valves the ovarian pitting may be observed laterally of dental adminicula. Cardinal process of ctenophoridium type, quite wide, triangular in ventral view, with thickened base which extends to the proximal dorsal margins of wide plates formed by inner socket ridges and crural bases ( Fig. 27H 2). There is a low but sharp and long dorsal median ridge which continues from the umbonal region quite far anteriorly (broken anterior part of valves limits the observation). Besides prominent, regularly disposed concentric imbricating lamellae the micro−ornament consists of well defined radial, densely packed capillae ( Fig. 27J 5). The incompleteness of the specimens does not allow examining the condition of denticulation.

Remarks.—The general aspect of the shell as well as the details of its internal structure and external ornament strongly suggest that the described species belongs to the genus Voiseyella . Although the specimens are very incomplete they can be easily distinguish from Voiseyella bruntoni Baliński and Sun, 2010a from sample MH1 by having longer shell, lower and more concave ventral interarea, wider ventral sulcus, simple dorsal fold without deep median furrow, and markedly thickened posterior shell tissue.

The specimens agree in most characters to Voiseyella texana from the Chappel Limestone (Mississippian) of central Texas ( Carter 1967). Both forms have similar size and shell shape, costation, and micro−ornamentation. It is also worth of noting that in both forms occurs the characteristic thickening of the posterior shell tissue. The only discrepancy between our material and that from Texas is in the strength of sulcus bounding costae which in the former appears to be stronger. The present specimens are also quite similar in general shell shape and ornamentation to Voiseyella anterosa ( Campbell, 1957) from the Lower Carboniferous of New South Wales (see Campbell 1957; Roberts 1964) and Voiseyella novamexicana (Miller, 1881) from the Chappel Limestone (Mississippian) of Texas. Our specimens differ from the both species by having less expanded laterally shell.

Stratigraphic and geographic range.— Voiseyella texana occurs in the Mississippian Chappel Limestone of central Texas ( Carter 1967) and the upper Tournaisian Banff Formation (lower Carboniferous) of western Alberta, Canada ( Carter 1987). Here we report very similar specimens from the Tournaisian of Muhua, southern China.

Figures

Fig. 27. Strophopleurid brachiopods from the Tornaisian Muhua Formation, southern China. A–F. Voiseyella bruntoni Baliński and Sun, 2010a. A. Incomplete dorsal valve, PKUM02−0527, in exterior (A1) and interior (A2) views. B. Incomplete dorsal valve, PKUM02−0528, in exterior (B1) and posterior (B2) views. C. Slightly damaged dorsal valve, PKUM02−0529, showing exterior (C1) and enlargement of cardinalia (C2). D. Incomplete ventral valve, PKUM02−0530, in exterior (D1) and interior (D2) views. E. Incomplete ventral valve, PKUM02−0531, in exterior (E1) and posterior (E2) views. F. Almost complete dorsal valve, PKUM02−0532, in exterior (F1), interior (F2), lateral (F3), posterior (F4), and anterior (F5) views. G–J. Voiseyella cf. texana (Carter, 1967). G, H. Two incomplete dorsal valves, PKUM02−0533 (G) and PKUM02−0534 (H), in exterior (G1, H1) and interior (G2, H2) views and enlargement of the interior showing cardinalia (G3). I. Exterior of ventral valve, PKUM02−0535. J. Incomplete ventral valve, PKUM02−0536, in exterior (J1), interior (J2), anterior (J3), and posterior (J4) views, and enlargement showing external micro−ornamentation (J5). Sample MH1 (A–F), GB (G, H, J), and GT (I).