Schizophoria (Schizophoria) resupinata ( Martin, 1809 )

Sun, Yuanlin & Baliński, Andrzej, 2008, Silicified Mississippian brachiopods from Muhua, southern China: Lingulids, craniids, strophomenids, productids, orthotetids, and orthids, Acta Palaeontologica Polonica 53 (3), pp. 485-524 : 521

Schizophoria (Schizophoria) resupinata ( Martin, 1809)

Fig. 27F–L .

1809 Conchyliolithus Anomites ( resupinatus ); Martin 1809: 49, figs. 13, 14.

1968 Schizophoria resupinata (Martin) 1809 ; Pocock 1968: 80–86, pl. 18: 7; text−figs. 13–15.

1968 Schizophoria resupinata (Martin) ; Brunton 1968: pl. 2: 1–6.

1989 Schizophoria (S.) resupinata ( Martin, 1809) ; Żakowa 1989: 103–106, pl. 1: 1–5; pl. 2: 1–5; pl. 3: 1–4; text−figs. 2–10.

2006 Schizophoria resupinata ( Martin, 1809) ; Bassett and Bryant 2006: 504–508; pl. 6: 1–10; pl. 7: 1–16; text−figs. 5–7.

Material.—70 complete shells and more than thousand isolated dorsal and ventral valves, several very small shells usually not exceeding 2 mm in width are also present.

Remarks.—The specimens from China are characterized by elliptical shell outline, width exceeding length, with rather gently rounded lateral and anterior margins. The shell is ornamented with more or less uniform costellae, but those with aditicules are slightly and gradually higher just prior to the termination with the aditicules’ apex ( Fig. 27K, L ). Those of aditicules which are filled with shell substance terminate with a small opening, in diameter similar to that of puncta, about 25µm ( Fig. 27K 2 ; see also Jin et al. 2007). In some specimens the openings of aditicule, especially those near the anterior margin, remain quite large attaining 120 µm in diameter ( Fig. 27L ).

Schizophoria (Schizophoria) resupinata is divided by some authors (e.g., Demanet 1934; Bond 1942; Pocock 1968) into several varieties which are regarded by some other as subspecies. Although the material from Muhua is numerous and well preserved, it is represented generally by disarticulated immature valves. This causes some difficulties in identifying it with any of these varieties or subspecies. Moreover, as Bassett and Bryant (2006) noted, some shell features are quite variable and their range should be studied carefully before separating stocks.

Stratigraphic and geographic range.—The species is one of the commonest form in sample MH1. It was revealed also in samples DPS−3, GB, Mu−42, and MH2. Schizophoria (Schizophoria) resupinata is a widely recognizable species ranging from the Late Devonian till the late Carboniferous (Pennsylvanian; K–D zones according to Pocock 1968).

Figures

Fig. 27. Schizophoriid brachiopods from the Muhua Formation, sample MH1. A–E. Schizophoria sp. A, B. Incomplete ventral valves, PKUM02−0345 (A) and PKUM02−0346 (B), in exterior (A1, B1) and interior (A2, B2) views. C. Incomplete ventral valve, PKUM02−0347, in exterior view. D. Incomplete ventral valve, PKUM02−0349, in interior view. E. Ventral valve, PKUM02−0348, in exterior view. F–L. Schizophoria (Schizophoria) resupinata (Martin, 1809). F. Ventral valve, PKUM02−0350, in exterior view. G, H. Dorsal valves, PKUM02−0351 (G) and PKUM02−0352 (H), in exterior (G1, H1) and interior (G2, H2) views. I. Ventral valve, PKUM02−0353, in interior view. J. SEM micrograph of juvenile shell, PKUM02−0354, in dorsal (J1) and posterior (J2) views. K. SEM micrographs of incomplete valve, PKUM02−0355, showing external costellae, nearly filled with shell substance openings of aditicules, and shell punctation; specimen in general (K1) and enlarged (K2) views. L. SEM micrograph, PKUM02−0356, showing external ornamentation, large openings of aditicules, and shell punctation.

Fig. 2. Lithological sections of the Tournaisian Muhua Formation at five sampling sites around Gedongguan village and their locations near Muhua, Guizhou Province, China (modified after Dzik 1997).