Überraschung: Fossilien aus dem Burgess-Schiefer im Ordoviz Marokkos
Surprise: fossils from the Burgess Shale in the Ordovician of Morocco
Furca mauretanica (Van Roy, 2006), Lower Ordovician, Fezouata biota with soft-bodied fossils, Zagora formation, southeastern Morocco, ca 4x4 cm, interesting details, partly three-dimensional. Perhaps it could be a relative of the Burgess fossil Marrella. Collection: Troppenz. Seller and photos: Mohamed Segaoui.
The Fezouata fossils of Morocco; an extraordinary record of marine life in the Early Ordovician
Peter Van Roy, Derek E. G. Briggs and Robert R. Gaines
Journal of the Geological Society, 172, 541-549, 7 July 2015, https://doi.org/PreviousNext
The discovery of the Fezouata biota in the latest Tremadocian of southeastern Morocco has significantly changed our understanding of the early Phanerozoic radiation. The shelly fossil record shows a well-recognized pattern of macroevolutionary stasis between the Cambrian Explosion and the Great Ordovician Biodiversification Event, but the rich soft-bodied Fezouata biota paints a different evolutionary picture. The Fezouata assemblage includes a considerable component of Cambrian holdovers alongside a surprising number of crown group taxa previously unknown to have evolved by the Early Ordovician. Study of the Fezouata biota is in its early stages, and future discoveries will continue to enrich our view of the dynamics of the early Phanerozoic radiation and of the nature of the fossil record.
Supplementary material: A complete faunal list is available at http://www.geolsoc.org.uk/SUP18843.
The Lower Ordovician Fezouata formations of Morocco hit the headlines in 2010 when they were reported to yield a diverse fauna of Burgess Shale-type fossils (Van Roy et al. 2010). Exceeding 1000 m in combined thickness, the Lower and Upper Fezouata formations are extensive units that crop out over a wide area in the Anti-Atlas region of southeastern Morocco, extending some 200 km south of the town of Alnif, and a similar distance to the west of Zagora, where the Fezouata biota was first discovered (Figs 1 and 2). Although abundant and diverse open-marine shelly faunas had been reported from these fine-grained siliciclastic deposits since the 1950s (e.g. Choubert et al. 1955; Destombes & Willefert 1959; Destombes 1962, 1972; Chauvel 1966, 1978; Havlíček 1971; Destombes et al. 1985), the first exceptionally preserved fossils were discovered only in the early 2000s by Mohamed ‘Ou Said’ Ben Moula, a local collector (Van Roy 2006; Van Roy & Tetlie 2006). He first shared information about his localities with Peter Van Roy in 2002, initiating a collaboration between a Moroccan collector and Belgian researcher that continues to this day.
Pictures: Typical Burgess Shale-type animals from the Fezouata biota. (a) Aegirocassis benmoulai, a giant filter-feeding anomalocaridid preserved in three dimensions within a concretion. Two sets of swimming flaps are evident on the left side of the trunk. (YPM (Yale Peabody Museum) 237172.) (b) A marrellomorph arthropod, probably belonging to the genus Furca. (MHNT (Natural History Museum of Toulouse) PAL.2007.39.80.1.) (c) Different type of marrellomorph showing similarities to Skania and Vachonisia. (YPM 226539.) The body and appendages are concealed by the carapace. All specimens are from the uppermost Tremadocian Araneograptus murrayi biozone.
Below: Aegirocassis reconstruction: Nobu Tamura / Creative Commons.