Halorella tenuicostata, (Termier, 1936)

Baliński, Andrzej & Biernat, Gertruda, 2003, New observations on rhynchonelloid brachiopod Dzieduszyckia from the Famennian of Morocco, Acta Palaeontologica Polonica 48 (3), pp. 463-474 : 471-473

publication ID	https://doi.org/ 10.5281/zenodo.13388115
DOI	https://doi.org/10.5281/zenodo.13328080
persistent identifier	https://treatment.plazi.org/id/BD121F17-FFE8-FF94-FFBF-F92B733EF808
treatment provided by	Felipe
scientific name	Halorella tenuicostata
status

Treatment

D. tenuicostata ( Termier, 1936)

Figs. 9 View Fig , 10 View Fig .

Halorella tenuicostata nov. sp.; Termier 1936: 1199–1120, pl. 12: 3–13. Halorella tenuicostata Termier ; Termier and Termier 1948: 47, figs.

10, 11; 1950: 73, pl. 98: 42–44, pl. 100: 11, 12, 16.

Lectotype: here designated; ZPAL Bp XVII/38−11, near Bou−Nebedou , Morocco; Late Devonian, Famennian; illustrated by Termier (1936, pl. 12: 6) and re−illustrated here in Fig. 10F View Fig .

Remarks.—This species is easily distinguished from all other species of the genus. Externally, it is characterized by medium−sized, rarely larger, very wide, triangular to almost fusiform or sub−cylindrical, finely costate shell. In large individuals, an arrest of growth (at least one) of the shell forming concentric rugae can be observed ( Fig. 10D View Fig ). Sometimes a distinct geniculation of the anterior commissure may be developed ( Fig. 10G, D View Fig 2 View Fig ). Faint and wide, slightly irregular radial plicae, independent of radial costation, are developed on some large shells ( Fig. 10D, F View Fig ). Posterior sectors of the commissure sharpened, vary from gently convex to distinctly concave in profile, resulting in characteristically curved posteriorly or up−turned lateral shell extremities ( Fig. 10E View Fig ).

D. tenuicostata differs from other species of the genus also in details of the internal shell structure. Serial sections of two shells reveal that dental plates are short but distinct, convergent ventrally. Crural bases are closely set on the ventral surface of the hinge plates, slightly elevated, forming longitudinal ridges. Proximal parts of the crura are compressed dorso−ventrally and slightly concave dorsally. Crural blades markedly widen anteriorly (see also Termier 1936: pl. 12: 12–13; Termier and Termier 1959: pl. 98: 44) and twist from horizontal to vertically subparallel in cross section, becoming slightly convex laterally. Median septum is rather low, attaining about half of the shell length. Dorsal adductor scars are deeply impressed and divided by the median septum.

External and internal differences of D. tenuicostata from other known species of the genus make the species quite easily recognizable and well defined, whereas the remining species of Dzieduszyckia are all externally similar to each other and difficult to separate. We decidedly prefer, however, despite the differences mentioned above, to keep the species within the genus Dzieduszyckia . Thus, the genus forms distinct and highly characteristic lineage of rhynchonelloid brachiopods which is exceptionally well represented in Morocco.

Occurrence.—The species is known from the Famennian limestones of several localities in vicinity of Bou Nebedou, near Khenifra (Middle Atlas, Morocco).