Oxfordian brachiopods from the Saïda and Frenda mountains (Tlemcenian Domain, north-western Algeria)

Abstract

Five brachiopod species are reported from two middle to upper Oxfordian (Late Jurassic) outcrops, situated in the Saïda and Frenda mountains (Tlemcenian Domain, north-western Algeria) and belonging to the heterochronous (Callovian to Oxfordian, locally to the Kimmeridgian) Argiles de Saïda Formation (Saïda Clay Formation). The upper Oxfordian (probably Dichotomoceras bifurcatus Zone) outcrop A yielded Dictyothyris kurri and Loboidothyridoidea indet. The middle Oxfordian (Liosphinctes plicatilis Zone, Cardioceras vertebrale Subzone) outcrop B yielded Monticlarella rollieri, Karadagithyris boullierae sp. n., and Zittelina sp.; this is the first report of the last-mentioned genus from Africa. Karadagithyris boullierae sp. n. is a link between previously known Bajocian to Bathonian (Callovian?) Karadagithyris s.s. and Tithonian to Lower Cretaceous species, formerly segregated as Svaljavithyris; the latter is considered herein as synonym of Karadagithyris. It is characterised by a plano-uniplicate anterior commissure and a suberect beak. The adult loop of Zittelina is confirmed as bilacunar (kingeniform) and not diploform (campagiform). The bulk of the assemblages comprises small and either smooth or finely ornamented species and thus represents a low-energy environment. The lack of modern revisions of the reported species in their type areas is the reason why only Dictyothyris kurri may be used as an index species for the middle to late Oxfordian.