Diversity and palaeoecology of Early Devonian invertebrate associations in the Tafilalt (Anti-Atlas, Morocco)

Abstract

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 Zlchovian 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.