A new species of Ivdelinia Andronov, 1961 from the Moroccan Givetian and its palaeoecological and palaeobiogeographical implications

Abstract

The collection and study of benthic fauna from Middle Devonian carbonate buildups of the Maïder Basin in the eastern Anti-Atlas of Morocco permitted the taxonomic revision of previously described brachiopods from this area. Rhynchonellids dominate the brachiopod fauna. In this work, however, the focus is put on the description of a new gypidulid species, <i>Ivdelinia pulchra</i>, which belongs to the family Gypidulidae (subfamily Ivdelininae), found among the brachiopods from the Aferdou el Mrakib reef mound. It represents the youngest <i>Ivdelinia </i>species so far described and is compared with other ivdelinids. <i>Ivdelinia pulchra </i>occurs as densely packed communities which lived in a carbonate predominant environment during the earlier stage of reef mound growth, suggesting a more or less allochthonous state of these communities. However, this taxon does not properly belong to the reef guild. In addition we discuss the palaeoecology of the new species

At the southern limits of the Devonian reef zone: Palaeoecology of the Aferdou el Mrakib reef (Givetian, eastern Anti‐Atlas, Morocco)

“…Given the limited outcrops of the core facies and necessity of indirect inference based on the reef‐derived debris, some disagreement developed over the years as to the palaeobathymetric position of the Aferdou reef (Franchi et al, ; Kaufmann, , ; Tessitore et al, ; Wendt, ). In his initial assessment of sedimentological and palaeoecological characteristics of the carbonate buildups of the Mader Basin, Wendt () proposed that Aferdou el Mrakib grew in a comparatively shallow‐water setting, at least temporarily reaching within the photic zone.…”

“…The first detailed geological description of Aferdou el Mrakib, together with a conodont‐based stratigraphic framework, were provided by Kaufmann () as a part of his broad geological studies in the entire Mader Basin area (Kaufmann, , , , ). Subsequently, several studies addressed selected aspects of palaeoecology and sedimentary development of the buildup (Franchi et al, ; Halamski & Baliński, ; Jakubowicz et al, ; Jakubowicz, Król, Zapalski, & Berkowski, ; Tessitore et al, ; Tessitore, Naglik, De Baets, Galfetti, & Klug, ).…”

“…Deposition of these strata was followed by the onset of relatively deep‐water, fine‐grained sedimentation that prevailed in the off‐reef setting during the main stage of the reef growth. The basal part of this argillaceous succession contains two marker horizons: (a) a bed of a nodular limestone containing numerous specimens of the phacopid trilobite Drotops megalomanicus Struve, 1990 (Kaufmann, ; Figure e,f) and (b) a horizon with several carbonate lenses hosting very rich, nearly monospecific accumulations of the gypidulid brachiopod Ivdelinia pulchra Franchi et al, (Tessitore et al, ; Figure c). In the proximal part of the ramp, the reef continued its growth.…”

“…Redeposited, yet generally well‐preserved fossils found in the fore‐reef debris represent, therefore, the bulk of the material that can provide clues as to the climax stage of the reef growth. Except the main reef builders, including tabulate and rugose corals and stromatoporoids, the most prominent reef‐derived elements include brachiopods, mostly representative of the Atrypida and pentamerid family Gypidulidae (Franchi et al, ; Tessitore et al, ; for a detailed brachiopod inventory, see Halamski & Baliński, ). The reef‐derived biota are mixed with frequent remains of nektonic organisms and local off‐reef fauna (Figure f–h), incorporated into the mass flow deposits during their basinward movement.…”

“…Nevertheless, also this buildup received limited attention in the past, and it has not yet been subjected to more extensive palaeoecological investigations. Most previous studies focused on general geological characteristics of the reef (Kaufmann, ; Wendt, , ), and only the brachiopod fauna was recently dealt with in more detail (Franchi, Schemm‐Gregory, & Klug, ; Halamski & Baliński, ; Tessitore et al, ). Here, we studied the taxonomic composition and habitats of the most important reef builders of Aferdou el Mrakib, enabling broad reconstruction of the palaeoecology and sedimentary environment of the reef.…”