No abstract

Marine Lower Devonian successions are widely exposed in the Dra Valley (Southern Anti-Atlas, Moroccan Pre-Sahara). Resulting from new studies, especially on brachiopods, conodonts, and dacryoconarid tentaculitids, the chronostratigraphic assignments of the Lower Devonian formations are revised. Thanks to lateral and vertical facies variations, it is possible to correlate pelagic and neritic successions and corresponding biostratigraphies. Pelagic conodont, dacryoconarid and goniatite faunas allow correlations and dating in the sense of the Bohemian and global chronostratigraphies, whereas units of the traditional Rhenish subdivision can be identified by means of neritic brachiopods.

Quantitative analyses of the taxonomic composition and palaeoecology of five Early Devonian faunules (earliest Lochkovian to early Emsian) collected from the locality Jebel Ouaoufilal in the Tafilalt (Morocco) were conducted. We examined 3376 specimens belonging to 158 species and their stratigraphic distribution. The quantitative data sets were analysed for alpha diversity and ecospace utilization. Macrofossils of every faunule were identified, counted and grouped according to ecological categories of tiering, motility and feeding behaviour. Based on these data, we noted (i) a strong increase in species richness, especially in benthic species, from the lowermost Lochkovian to the Pragian stage and a following subtle decrease in the early Emsian and (ii) a considerable expansion of ecospace use from the earliest Lochkovian to the early Emsian. These general trends are considered to be a result of favourable living conditions due to a growing oxygen content at the sea floor, which correlates with a regional and potentially a global regression from the Lochkovian to the Pragian. A transgression in the early Zlíchovian probably reduced the species richness by decreasing the oxygenation of bottom waters. Additionally, we described and figured three new genera and six new species of the diverse Pragian faunule (86 species): the hederelloid Filihernodia buccina gen. et sp. nov., the crinoid Hexawacrinus claudiakurtae gen. et sp. nov., the gastropods Oriomphalus multiornatus sp. nov., Eohormotomina restisevoluta gen. et sp. nov., and the cephalopods Tenuitheoceras secretum gen. et sp. nov. and Arionoceras kennethdebaetsi sp. nov. We record the first occurrence of Tiaracrinus moravicus from Africa. •

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

On Aferdou El Mrakib, a large reef mound in the Maïder region (Anti-Atlas, Morocco), thick-shelled gypidulids of two genera are locally very abundant. Like Stringocephalus in the shallow water limestone formations in Germany, these Moroccan brachiopods of the genera Devonogypa and Ivdelinia often display greenish shells. By analysing these shells by EDX, it turned out that the colour was possibly caused by impurities of Fe 2?-ions. The concentration varies, indicating that the colour is less dependent on the concentration than on shell thickness, because only the thickest parts of the shells appear green and thin-shelled forms never display the green colour. There is also some indication that the Fe content increases towards deeper shell layers (further away from the surface). In addition, we examined the quality and spatial distribution of sublethal injuries in over 200 specimens of Devonogypa and Ivdelinia. Shape, spatial distribution on the shells, and abundance of the sublethal injuries support the hypotheses that (1) the injuries had several causes, (2) some of these were inflicted by predators, probably cephalopods, and (3) many fractures and deformations might have been caused by the brachiopod shells hitting each other in dense populations in agitated water. The existence of dense clusters, built by the association of members of both genera or of only one taxon, is corroborated by the patchy occurrence of these brachiopods.