Menucoestheria bocki, Olempska, 2004

Olempska, Ewa, 2004, Late Triassic spinicaudatan crustaceans from southwestern Poland, Acta Palaeontologica Polonica 49 (3), pp. 429-442 : 439

Menucoestheria bocki sp. nov.

Figs. 5C, D , 9 .

Holotype: ZPAL Cr. 6/29 ( Fig. 9B ).

Type horizon and locality: Late Triassic, late Carnian, Krasiejów,southwestern Poland.

Derivation of name: In honour of Wilhelm Bock, a researcher of Triassic spinicaudatans.

Diagnosis.—Carapace oval in outline; moderate in size; growth bands ornamented with reticulation in dorsal and median areas of valve, passing into radial striae in ventral growth bands.

Material.—19 more or less fragmentary specimens.

Description.—Carapace of moderate size, elliptical in outline, up to 4.8 mm long and 3.2 mm high; dorsal margin straight and long, umbo inset subcentral to subterminal, slightly raised above dorsal margin; anterior margin rounded, posterior more narrowly rounded; ventral margin slightly convex; growth lines 14–24 in number; dorsal and median growth bands representing younger moult stages ornamented by reticulate pattern, median−ventral growth bands ornamented by densely spaced, minute, slightly anastomozing radial striae, density of these structures averages about 10 per 0.20 mm.

Remarks.— Menucoestheria bocki sp. nov. exhibits a wide range of variation in its type of surface ornamental pattern ( Fig. 9 ). The Polish material is similar to that of Bairdestheria colombiana (Bock, 1953) from the Rhaetic of Colombia ( Bock 1953a: pl. 13: 5–7, 12) in having radial striae ornament in terminal growth bands and changing from anastomozing striae to reticulate ornament. M. bocki resembles representatives of Menucoestheria from the Late Triassic of Chile ( Gallego and Covacevich 1998) in its carapace outline and appearance of the ornamentation pattern.

Occurrence.—Late Carnian, Krasiejów, Poland.

Figures

Fig. 5. A. Laxitextella laxitexta (Jones, 1890). Left valve ZPAL Cr. 6/2 in oblique dorsal view (A1), and details of shell structure showing layers of cuticle (A2–A4). B. Menucoestheria? sp. Right valve ZPAL Cr. 6/3 with details showing layers of cuticle in mid−dorsal area. C, D. Menucoestheria bocki sp. nov. C. Specimen ZPAL Cr. 6/28, showing growth bands ornamentation (C1), and details of shell structure showing layers of cuticle in median area (C2). D. Specimen ZPAL Cr. 6/15, showing growth band reticulate ornamentation in mid−dorsal part (D1), and details of cuticle layers in mid−dorsal area (D2).

Fig. 9. Menucoestheria bocki sp. nov. A. Right valve ZPAL Cr. 6/15 in lateral view (A1), and details showing growth bands ornamentation, reticulate in dorsal and median areas, passing into radial striae in ventral part (A2), the same in oblique view (A3). B. Right valve ZPAL Cr. 6/29 in lateral view (B1), and details of growth bands ornamentation (B2, B3); holotype. C. Right valve ZPAL Cr. 6/20 in lateral view (C1), dorsal area (C2), and details of growth bands ornamentation (C3, C4).