Taphonomy and palaeoecology of the green Devonian gypidulid brachiopods from the Aferdou El Mrakib, eastern Anti-Atlas, Morocco

Abstract

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.

Fossil‐Lagerstätten, palaeoecology and preservation of invertebrates and vertebrates from the Devonian in the eastern Anti‐Atlas, Morocco

“…The light grey Eifelian to early Givetian carbonates and claystones of the Maïder Basin do yield occasional invertebrate remains such as corals, crinoids, brachiopods and trilobites. Particularly at Jebel Rheris, Jebel Issoumour, Jebel Oufatene, Madene El Mrakib and around the reef-mound Aferdou El Mrakib, reef fauna occurs in more or less rock-forming amounts, sometimes in the form of biostromes or carbonate build-ups (Kaufmann 1998;Fröhlich 2006;Tessitore et al 2013Tessitore et al , 2016. Towards the end of the Givetian, carbonate production decreased, and locally (particularly in the depocentre), ammonoid associations occur that show the same goethite preservation as in the Tafilalt Basin (Bockwinkel et al 2015).…”

“…It is thus not surprising that some of the carbonate build‐ups contain abundant corals (Kaufmann ; Berkowski ) and brachiopods (Halamski & Baliński ; Tessitore et al . ). Similarly, ammonoids are common from the Emsian to the Viséan (Klug ; Korn et al .…”

“…Several groups of invertebrates are very common in the Maïder and Tafilalt regions. It is thus not surprising that some of the carbonate build-ups contain abundant corals (Kaufmann 1998;Berkowski 2006) and brachiopods (Halamski & Baliński 2013;Tessitore et al 2013). Similarly, ammonoids are common from the Emsian to the Viséan (Klug 2001;Korn et al 2007Korn et al , 2016aDe Baets et al 2013) and occur in impressive diversity, but their modes of preservation are almost as diverse.…”

Deep in shadows, deep in time: the oldest mesophotic coral ecosystems from the Devonian of the Holy Cross Mountains (Poland)

“…Thus, the size of colonies also supports the interpretation of the Laskowa biostrome as an MCE. It must be stressed that tabulates exceeding 50 cm are rare in the Devonian, but such colonies are known from the Givetian of Anti-Atlas (Tessitore et al 2013).…”

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

“…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.…”