A new Frasnian placoderm assemblage from the eastern Anti-Atlas, Morocco, and its palaeobiogeographical implications

Abstract

A preliminary description of a new placoderm assemblage from the upper Frasnian of Morocco shows close similarity to the Bad Wildungen locality in Germany, with the arthrodire taxa Enseosteus, Rhinosteus, Walterosteus, Brachydeirus, Oxyosteus, Brachyosteus, Erromenosteus and Aspidichthys in common. Both horizons are from the late Frasnian, conodont Zone 13 ( bogartensis). The North African assemblage is probably slightly younger, in between the lower and upper part of this Zone, the Upper rhenana to linguiformis Zone. Southern Morocco was located on the northern shelf of Gondwana and Bad Wildungen on the southern shelf of Laurussia during the Upper Devonian. The analysis of five late Frasnian localities is in conflict with the palaeogeographical model from the palaeomagnetic data, indicating a large ocean separating both continents. No palaeobiogeographical barrier to the placoderms was present between these continents, supporting an alternative hypothesis, primarily based on palaeontological data with a small ocean separating Gondwana and Laurussia and a connection in the Late Devonian.