738


Journal of Paleontology 91(4):735–754


who mentioned the presence of diploporitans (Calix sedgwicki Rouault, 1851 and Holocystites? sp.) in Darriwilian quartzites from the Jbel Tachilla (western Anti-Atlas). Since this initial report, abundant and diverse echinoderm faunas have been described from various parts of the Anti-Atlas and from all Ordovician formations (Termier and Termier, 1950, 1970; Choubert et al., 1953; Ubaghs, 1963; Chauvel, 1966, 1969, 1971a, 1971b, 1977, 1978; Chauvel and Régnault, 1986; Donovan and Savill, 1988; Cripps, 1990; Beisswenger, 1994; Le Menn and Spjeldnaes, 1996; Ruta, 1999; Gutiérrez-Marco et al., 2003; Lefebvre and Fatka, 2003; Lefebvre and Botting, 2007; Lefebvre et al., 2007, 2008, 2010, 2016b; Nardin, 2007; Régnault, 2007; Hunter et al., 2010; Noailles et al., 2010; Sumrall and Zamora, 2011; Allaire et al., 2015; Martin et al., 2015; Nardin and Régnault, 2015; Sprinkle et al., 2015; Zamora et al., 2015). As a result, the Anti-Atlas of Morocco is the only peri-


Gondwanan region yielding a relatively complete record of successive echinoderm faunas from the Tremadocian to the Hirnantian (Lefebvre et al., 2013). It thus provides a unique record of the diversification of this clade of marine invertebrates in siliciclastic settings at high, southern paleolatitudes (close to the South Pole) during the Great Ordovician Biodiversification Event (Lefebvre, 2007; Lefebvre et al., 2013). Twelve classes or distinctive groups of echinoderms have been documented so far in the Ordovician of the Anti-Atlas, including asteroids, cor- onates, crinoids, cyclocystoids, diploporitans, edrioasteroids, eocrinoids, ophiuroids, rhombiferans, solutans, somasteroids, and stylophorans. The locality yielding the new cyclocystoid lies in the


Taddrist Formation, close to the village of Battou (South of Alnif, eastern Anti-Atlas) (Figs. 1, 2). This locality was descri- bed by Rábano et al. (2014), who provided detailed information about the faunal content and age based on the presence of key graptolites and trilobites. In this area, the Taddrist Formation has been excavated predominantly by local collectors and has yiel- ded a rich faunal assemblage preserved in carbonate concre- tions. Only three specimens of cyclocystoids were collected by us directly from the outcrop; the remainder were acquired from amateur or commercial collectors or bought at fossil shows (e.g., Sprinkle et al., 2015). Considering that the concretions from this bed between 38 and 40m above the base of the formation have a characteristic aspect, all of them probably derive from the same or a laterally equivalent outcrop, and major differences in their stratigraphic position are not likely. Unfortunately, original top or bottom of our cyclocystoid con- cretions from this layer has not been recorded by any of the collectors, perhaps because many concretions were already weathered out and lying on the surface of this sloping outcrop. Rábano et al. (2014) suggested that the levels containing


fossiliferous concretions belong to the Didymograptus murchi- soni graptolite Biozone (Gutiérrez-Marco et al., 2003), which


Figure 2. Chronostratigraphical chart for the Ordovician, indicating the level that provided the studied specimens. Correlations between stratigraphic units in the Anti-Atlas (after Destombes et al., 1985; Gutiérrez-Marco et al., 2003; Villas et al., 2006), British regional time scale (Fortey et al., 1995), North American graptolite zonal sequences (Webby et al., 2004), Mediterranean regional stages (Gutiérrez- Marco et al., 2003), and global stages are shown (from Sumrall and Zamora, 2011, modified). Kral = Kralodvorian; Tr. = Tremadocian; pars. = partial.


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