The genus Dzieduszyckia is especially well represented and diverse in the Famennian strata of the Middle Atlas, Morocco. In this paper we re-study and re-illustrate the rich collection of Dzieduszyckia from Morocco, described by Henri and Genevičve Termier, and originally referred to Halorella or Eoperegrinella. New data on the internal shell structure of D. crassicostata, D. intermedia, and D. tenuicostata indicate great intraspecific variability in morphology. The structure of crura of three studied species demonstrates that subfamily Dzieduszyckiinae is better placed within the family Halorellidae, instead of Peregrinellidae. Type specimens (lectotypes) of the three species were also selected. An analysis of the stable isotopes of carbon and oxygen of the shell material of Dzieduszyckia and carbonate sediment was used to investigate the presumed chemosynthetic nature of its paleoenvironments. The analyses of the Moroccan and Polish material do not show any signature of unusual environmental conditions: they fall in the range of the mean values of d13C for the Late Devonian.

Key words: Brachiopoda, Halorellidae, Dzieduszyckia, carbon isotopes, Famennian, Morocco.

Andrzej Baliński [balinski@twarda.pan.pl], and Gertruda Biernat [gbiernat@twarda.pan.pl], Instytut Paleobiologii PAN, ul. Twarda 51/55, PL−00−818 Warszawa, Poland.