The brachiopod faunas from the Fezouata Shale (Lower Ordovician; Tremadocian–Floian) of the Zagora area, Anti-Atlas, Morocco: evidence for a biodiversity hub in Gondwana

Abstract

Since the early 2000s, the discovery of fossils and their collection from the Fezouata Shale has accelerated; enabling us to understand the faunas more thoroughly. The brachiopod fauna has not been investigated for the past 50 years, and we present here the results of our recent studies. From the material (c. 350 samples), 30 species were identified and assigned to 23 genera. Among these, one new genus (Tinzoulinorthis) and four new species (Wosekella maghribi, Rafanoglossa inversa, Orbithele tazagurta, Lacunites punctum) are erected; one taxon is recognized at the family level. The fauna described from the upper Tremadocian horizons is more diverse than those in the Floian. The former is characterized by a high c-diversity, although at the horizon level the a-diversity is low to medium. This fauna is typical of high-energy, shallow-water, unstable environmental conditions, in which long-lived communities were prevented from developing into climax communities, and the succession of opportunists were regularly smothered in situ and killed by storm deposits. Multivariate analyses of the faunas indicate that the Tremadocian fauna, characterized by many endemic taxa, has closer affinities with faunas from peri-Gondwanan terranes, in particular Bohemia. The Tremadocian Fezouata fauna is very rich in taxon first occurrences, which, coupled with a high c-diversity, suggest that it may have been a diversity hub. In contrast, the Floian Fezouata fauna not only shows stronger connections with Bohemia and the Montagne Noire, it also has links with the South Urals and Baltica, reflecting the changing Early Ordovician palaeogeography.