Coeloterorhynchus schucherti ( Stainbrook, 1945 )

Baliński, Andrzej, 2006, Brachiopods and their response to the Early-Middle Frasnian biogeochemical perturbations on the South Polish carbonate shelf, Acta Palaeontologica Polonica 51 (4), pp. 647-678 : 666-667

Coeloterorhynchus schucherti ( Stainbrook, 1945)

Figs. 14A–C , 15 .

1945 Pugnoides schucherti Stainbrook , n. sp.; Stainbrook 1945: 43, fig. 1: 13, pl. 4: 15–19.

1979 Parapugnax schucherti ( Stainbrook, 1945) ; Baliński 1979: 36–37, fig. 11B–C, pl. 4: 4–5, 7.

1985 Coeloterorhynchus schucherti Stainbrook, 1945 ; Baliński 1985: 242–243, pl. 21: A–D; pl. 22: 1–2.

1990 Parapugnax schucherti ( Stainbrook, 1945) ; Budziszewska 1990: 37–38, pl. 8: 1.

1993 “ Parapugnax ”; Makowski in Racki et al. 1993: pl. 18: 5.

Material.—Ten complete shells and 11 fragmentary specimens from Wietrznia Id−W (beds 4, 14, and 18) and Wietrznia Ie sections (beds 43–45, 65, and 66).

Description.—Shell medium to small sized for genus, strongly dorsibiconvex, subpentagonal in outline with the greatest width at about midlength. The cardinal margin broadly obtuse forming an angle of 107–120°, lateral margins rounded, anterior margin truncated, anterior commissure strongly uniplicate.

Ventral valve gently convex, sulcus very wide, uniformly concave and poorly bounded laterally, widening rapidly and forming long, wide, distally slightly rounded tongue.

Dorsal valve convex in lateral profile, narrowly domed in anterior view, with swollen umbonal region; lateral flanks strongly expanded ventrally; fold originating about the midvalve, poorly defined with convex top.

Shell smooth, noncostate in posterior half but covered by fine, flat, often difficult to trace, radiating capillae (about 6 per mm); anterior surface costate, median costae strong, angular, simple; flanks marked by up to 7 flattened costae, fold with 4–7, and sulcus with 3–6 costae; parietal costae absent or one costa can be observed on each slope; growth lines dense.

Ventral valve interior with short, delicate dental plates. Dorsal interior with horizontal hinge plates; without median septum ( Fig. 15 ).

Remarks.—The specimens here described have strong resemblance to Pugnoides schucherti described from the Independence Formation of Iowa by Stainbrook (1945). The species was inadequately figured by him and it is difficult to determine the range of external variability. However, Cooper and Dutro (1982: 77) noted that the Independence species is quite variable. It seems, that the specimens here described fall within the range of variability of Stainbrook’s species. The colour shell pattern in Coeloterorhynchus schucherti from the Dębnik anticline (southern Poland) was described by Baliński (1985).

Occurrence.—The species was recovered in several layers of Wietrznia Id−W and Ie sections representing Palmatolepis transitans conodont Zone (Figs. 2, 3). Earlier it was described from the early part of the Middle Frasnian (Middle and Upper Polygnathus asymmetricus Zone ; = Pa. punctata – Pa. hassi zones) of the Dębnik anticline of southern Poland ( Baliński 1979). Originally, it was described as Pugnoides schucherti from the Independence Shale of Iowa ( Stainbrook 1945).

Figures

Fig. 14. Rhynchonellid brachiopods from the middle Wietrznia Beds of Wietrznia Ie (A) and Id−W (B–F). A–C. Coeloterorhynchus schucherti (Stainbrook, 1945), ZPAL Bp 60/7 (A), GIUS 4−273 Wt/IM−12 (B), and GIUS 4−273 Wt/IM−13 (C), three complete shells in dorsal (A1, B1, C1), ventral (A2, B2, C2), lateral (A3, B3, C3), posterior (A4, B4, C4), and anterior (A5, B5, C5) views. D–F. Coeloterorhynchus dillanus (Schmidt, 1941), GIUS 4−273 Wt/EB−1 (D), GIUS 4−273 Wt/EB−2 (E), and GIUS 4−273 Wt/EB−6 (F), three complete shells in dorsal (D1, E1, F1), ventral (D2, E2, F2), lateral (D3, E3, F3), posterior (D4, E4, F4), and anterior (D5, E5, F5) views.

Fig. 15. Serial sections of the shell of Coeloterorhynchus schucherti (Stainbrook, 1945), ZPAL Bp 60/34, middle Wietrznia Beds of Wietrznia Ie. Numbers refer to distance in mm from ventral umbo.