Cleiothyridina struniensis ( Dehée, 1929 )

Halamski, Adam T. & Baliński, Andrzej, 2009, Latest Famennian brachiopods from Kowala, Holy Cross Mountains, Poland, Acta Palaeontologica Polonica 54 (2), pp. 289-306 : 299-300

Cleiothyridina struniensis ( Dehée, 1929)

Fig. 9C–F.

1929 Seminula? struniensis sp. nov.; Dehée 1929: 27–28, pl. 4: 1–3.

1976 Composita struniana (Dehée) ; Matyja 1976: pl. 10: 1, 3, 5 [spelling error for struniensis ].

?1983 Cleiothyridina sp. ; Biernat 1983: 140–141, pl. 6: 3.

Material.—Two shells (ZPAL Bp 57/85, 2, 113) and a single ventral valve (ZPAL Bp 57/34).

Description.—Shell up to 25.4 mm in length, moderately to strongly elongate, ventribiconvex. Maximal width at 3/5–3/4 of the length. Interareas not apparent. Umbo thick, incurved, with large pedicle foramen attaining up to 2.4 mm in diametre. Anterior commissure uniplicate, deflection subtriangular to trapezoidal, occupying 3/5–4/5 of the shell width. Ornamentation of spine bases arranged along concentric lines ( Fig. 9C 6 ).

The single ventral interior ZPAL Bp 57/34 shows short dental plates and small, deeply impressed rhomboidal posterior adductor scars, and faintly impressed, large anterior adductor scars ( Fig. 9E).

Remarks.—The material is described here as belonging to one species; however, differences in shape between the specimens illustrated in Fig. 9C and D are quite notable; the former is nearly identical to the specimens from the type collection ( Dehée 1929); the latter, wider and more pentagonal, is more alike to Cleiothyridina royssii (L’Éveillé, 1835) as illustrated by Matyja (1976: pl. 15: 1–3). However, this species is more rounded in outline. The shell shown in Fig. 9F reveals a prominent ventral sulcus. The interior figured in Fig. 9E is fragmentary, and it cannot be precised to which morphotype it is more similar.

The micro−ornamentation of the described shells is characteristic of the subfamily Cleiothyridininae . They are very similar externally to specimens from the “calcaires d’Étroeungt” described and illustrated by Dehée (1929) as Seminula (?) struniensis Dehée, 1929 . Brice (in Hubert et al. 2007) referred the Étroeungt material to the genus Composita considered by Alvarez and Rong (2002) to include Seminula . The Holy Cross Mountains species (and, consequently, the putatively conspecific Ardennes specimens) is referred here rather tentatively to the genus Cleiothyridina on account of longitudinally ovate outline (pentagonal in Crinisarina ) and fine growth lamellae (large in Carteridina ); however, diagnostic internal characters of both type specimens and shells from Kowala are unknown.

The muscle scars figured in Fig. 9E show notable similarity to those of Cleiothyridina dilimensis Grunt, 1997 from the lower–middle Carboniferous of Kolyma−Omolon Massif ( Grunt 1989: fig. 31).

The specimen from the early Famennian (Late Palmatolepis crepida or Early Palmatolepis rhomboidea Zone ) of Jabłonna described as Cleiothyridina sp. by Biernat (1983: pl. 6: 3), with length approximately equal to the width and poorly developed sulcus and fold, might also belong to the described species.

Stratigraphic and geographic distribution.—Avesnois ( France), latest Famennian ( Dehée 1929); Holy Cross Mountains ( Poland), most probably latest Famennian.

Figures

Fig. 6. Transverse serial sections of Novaplatirostrum sauerlandense Sartenaer, 1997 through shell ZPAL Bp 57/40 from Kowala, set L. Numbers indicate distances in mm from ventral umbo.