Laxitextella sp. A

Olempska, Ewa, 2004, Late Triassic spinicaudatan crustaceans from southwestern Poland, Acta Palaeontologica Polonica 49 (3), pp. 429-442 : 436-438

Laxitextella sp. A

Fig. 8 .

Material.—Thirteen carapaces and valves (carapaces with only one valve visible).

Description.—Carapace of moderate size, varying from ovato−oblong to subrhomboidal in lateral outline, up to 7.4 mm long and up to 6.0 mm high; dorsal margin almost straight to slightly convex; umbo small, close to anterior end of dorsal margin; growth bands approximately 26 in largest specimens; growth bands widely spaced in median part and closely spaced in ventral part of valve; growth bands flattened with fine reticulate ornament; 3–4 meshes (0.020 mm in diameter) in narrow growth band in ventral part of carapace, 10–12 meshes (0.033 mm in diameter) in median part of carapace.

Remarks.—The specimens from Krasiejów are similar in valve shape and ornamental pattern to those of Shipingia dorsorecta ( Reible, 1962) from “obere Bunte Mergel” of Germany, but differ from the latter in larger size of valves, more growth bands, and the small umbo. However, the material of Reible (1962: pl. 9: 1, 2, fig. 16) is very poorly preserved and details of morphology are difficult to study (see also discussion in Seegis 1997 and Channell et al. 2003).

The specimens of Laxitextella sp. A from Krasiejów differ from those of L. laxitexta in their fine reticulate ornament (up to 10 meshes in median part), the presence of several closely spaced growth bands in ventral part of the carapace, and relatively more widely spaced growth bands in the median part of the carapace.

Laxitextella sp. A differs from Laxitextella sp. sensu Seegis 1997 in more delicate ornamentation on growth bands. It is similar in lateral outline and size of the valves to Laxitextella forbesi ( Jones, 1862) from the Upper Triassic of Argentina, but the latter has granulate ornament on the growth bands. L. sp. A is also similar in ornamentation pattern to Laxitextella sp. sensu Tintori 1990.

Occurrence.—Late Carnian, Krasiejów, Poland.

Figures

Fig. 8. Laxitextella sp. A. A. Left valve ZPAL Cr. 6/1 in oblique lateral−ventral view (A1), and details of growth bands reticulate ornamentation in mid−ventral area (A2, A3); the same in anterior view (A4); the same showing details of growth bands ornamentation in mid−anterior area (A5); details of shell structure in mid−anterior area (A6). B. Left valve ZPAL Cr. 6/13 in lateral view.