Aulacella interlineata (Sowerby, 1840)

Halamski, Adam T. & Baliński, Andrzej, 2009, Latest Famennian brachiopods from Kowala, Holy Cross Mountains, Poland, Acta Palaeontologica Polonica 54 (2), pp. 289-306 : 293-294

Aulacella interlineata (Sowerby, 1840)

Fig. 2B–E .

1840 Orthis interlineata ; Sowerby 1840: pl. 53: 11, pl. 54: 14.

1882 Orthis bergica sp. nov.; Kayser 1882: 61–63, pl. 2: 6–11.

1902 Orthis interlineata Phill. ; Drevermann 1902: 514–515. 1926 Orthis Bergica Kayser ; Lecointre 1926: 122. 1929 Dalmanella interlineata Sowerby ; Dehée 1929: 31–33, pl. 5: 1–5. 1932 Dalmanella interlineata (Sowerby) ; Gallwitz 1932: 88–90, pl. 6:

6–7 [cum syn.]. 1932 Dalmanella bergica (Kayser) , nov. em.; Gallwitz 1932: 85–88,

pl. 6: 3–5 [cum syn.]. non 1964 Aulacella interlineata (Sowerby, 1840) ; Sougy 1964: 437, pl.

42: 18, 19 [ A. prisca ]. 1976 Aulacella interlineata (Sow.) ; Matyja 1976: pl. 1: 2, 6.

Material.— 13 specimens: 12 originating from set L ZPAL Bp 57/4–6, 28–30, 35–36, 86–89; one from set K, ZPAL Bp 57/18 .

Description.—Shell rather small (up to 12.1 mm in width), transverse, with maximal width near the anterior margin (4/5 to 7/8 of the shell length measured from the umbo). Some specimens are nearly rectangular in outline ( Fig. 2C, D ), whereas others are trapezoidal ( Fig. 2E ). Postero−lateral extremities frequently angular, antero−lateral ones rounded. Dorsal sulcus imperceptible ( Fig. 2C ) to distinct, yet shallow ( Fig. 2E ), U−shaped in cross−section, occupying about 1/3 of the shell width at anterior commissure. Anterior commissure rectimarginate to unisulcate.

Ornamentation of costae and costellae, the latter arising by both intercalation and bifurcation, all of comparable height and thickness at anterior margin, separated by wider furrows, 2–4 per mm at anterior margin.

The single dorsal interior ZPAL Bp 57/4 shows a stout cardinal process, strong brachiophores, a muscle area extending to 1/3 of the valve length, highly elevated peripherally and subdivided medially by a wide longitudinal elevation ( Fig. 2E ).

Ventral interior unknown.

Remarks.—This species differs from the type species of the genus, namely Eifelian–Givetian Aulacella prisca (Schnur, 1851) (= Aulacella eifeliensis according to several authors), as well as from Frasnian Aulacella aggeris Mottequin, 2008 , in more subquadrate postero−lateral extremities and in the position of maximal width (at 4/5–7/8 of the shell length in the former, 3/ 4 in A. prisca , about midlength or slightly anteriorly in A. aggeris ; Mottequin 2008). Internal structures of both taxa do not show any major difference, except for much stronger bordering of the muscle area in the described species.

Kayser (1882) and Gallwitz (1932) separated Aulacella interlineata (Sowerby, 1840) and A. bergica ( Kayser, 1882) according to the size. The latter author held that both the Rhenish material he investigated and the Étroeungt material described by Dehée (1929) under Dalmanella interlineata consisted in fact of two species, the actual D. interlineata and D. bergica ( Kayser, 1882) , the former being smaller. However, the differences in form are very subtle (mean length to width ratios 0.78 and 0.77, respectively; presence or absence of a sulcus; weaker or stronger convexity of valves). A similar case occurs within the samples of Aulacella prisca from the Middle Devonian of the Łysogóry Region, which show high intraspecific variability ( Biernat 1959 reduced to synonymy several taxa described by Gürich 1896 from the upper Eifelian of Skały); in the lower Givetian of Błonia Sierżawskie near Świętomarz some very large forms are present ( Halamski 2009: pl. 11: 31, 33–36) that are, once again, best treated as representing intraspecific variability. This favours the broad interpretation of A. interlineata with A. bergica as a synonym ( Drevermann 1902; Dehée 1929). This view is provisorily accepted here, but should be confirmed on the type material of both taxa.

Stratigraphic and geographic distribution.—Europe, Northern Africa; Frasnian to Famennian ( Dehée 1929). Reports from Armenia ( Abrahamian 1957) may require confirmation.

Figures

Fig. 2. Middle to Latest Famennian brachiopods from Kowala. A. Barroisella sp. The bivalved specimen ZPAL Bp 57/70a showing strongly exfoliated ventral valve (ventral internal mould) and interior of dorsal valve (lower right) (A1) and its counterpart ZPAL Bp 57/70b (A2); enlargement of the posterior region of the ventral valve showing pseudointerarea and elongated median muscle scar (A3). B–E. Aulacella interlineata (Sowerby, 1840). B–D. Three shells ZPAL Bp 57/4a, 4b, and 86, respectively, in dorsal (B1, C1, D1) and ventral (B2, C2, D2) views showing variability in the shell outline. E. Dorsal valve ZPAL Bp 57/5 exterior (E1) and interior (E2). F, H, I. Schellwienella pauli (Gallwitz, 1932). F. Slightly destroyed shell ZPAL Bp 57/20 in dorsal (F1), ventral (F2), lateral (F3), posterior (F4), and anterior (F5) views. H. Limestone block ZPAL Bp 57/103 with accumulation of shells of S. pauli. I. Interior of ventral valve ZPAL Bp 57/100. G. Productida indet., mould ZPAL Bp 57/7 of exfoliated dorsal valve. J. Productida indet. Posterior view of mostly decorticated and slightly crushed dorsal valve ZPAL Bp 57/8. K. Mesoplica sp. Ventral valve ZPAL Bp 57/1 in ventral (K1) and posterior (K2) views. Scale bars 5 mm.