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 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. •

Unusual occurrence of dalmanitid trilobites in the Lochkovian of the Prague Basin (Czech Republic)

“…This migration route (A in Fig. 6) is consistent with the suggested course of the South Equatorial Current (sensu Wilde 1991) as well as the South Tropical Current along the NE margin of Laurussia (see Scotese & McKerrow 1990, Gnoli 1985, Gnoli et al 1988, Manda & Frýda 2010, Frey et al 2014. In the latest Lochkovian there was another, minor influx of new trilobite elements -e.g.…”

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

“…Regional palaeoecology was examined by Frey et al . (, ) for the Early Devonian of the southern Tafilalt Platform and the Famennian to Tournaisian and locally for the Pragian to Eifelian by Klug et al . ().…”

“…Some of these layers contain rich benthic as well as planktonic assemblages, indicating increased oxygen levels (Frey et al . ; Klug et al . ).…”

Ancestry, Origin and Early Evolution of Ammonoids

“…2. Increase in swimming speed and maneuverability (Klug 2001a;Korn and Klug 2003;Klug et al 2008a, b;Monnet et al 2011;De Baets et al 2013b;Frey et al 2014;Naglik et al 2015): The changes in conch morphology of early ammonoids occurred simultaneously and convergently (or even in parallel) in various clades (Korn and Klug 2003;Kröger 2005;Monnet et al 2011Monnet et al , 2015. This supports the hypothesis that the evolutionary tendency towards tighter coiling was ecologically driven.…”

“…According to fossil evidence, the Bactritida had originated already in the earliest Emsian. This phylogenetic event was followed by the origin and radiation of ammonoids in a geologically abbreviated amount of time (Erben 1960(Erben , 1964a(Erben , b, 1965(Erben , 1966Becker and House 1994;House 1996;Klug et al 2008;Kröger 2008b;De Baets et al 2010, 2013bFrey et al 2014).…”