ASAPHELLUS AFF. FEZOUATAENSIS ENTOMBED WITH RUSOPHYCUS CARLEYI, AND OTHER CLOSE ENCOUNTERS FROM THE ORDOVICIAN OF SOUTHERN MOROCCO

The Arenig Fezouata Formation is composed of thin-bedded, pyrite-rich, fine sandstones and mudstones. The asaphid trilobite, Asaphellus, is either entombed or is in close association with the trace fossil Rusophycus carleyi. The dimensions and morphology of this trilobite closely match the trace. Five trilobite specimens have been found directly above Rusophycus carleyi. In this case, they occur in a thin bed of sandstone, suggesting that the trilobite may have been entombed in the trace that it had recently produced. Intimate associations between a putative trace maker and a trace are extremely rare, particularly for the Trilobita. The large number of specimens of both the ichnofossils and the trilobites, in close association, suggests that they are a rare example of a trace maker and its traces. Eleven coxal impressions, that form a part of R. carleyi, is the number expected for an asaphid trilobite (one for each of eight thoracic segments and one for each of three post-oral cephalic appendages). Impressions of the hypostome, cephalic margin and pygidial margin in a number of the ichnofossils also correspond to the morphology of this asaphid trilobite. A few specimens, of the ichnofossils, show impressions of a series of thoracic segments. The size and shape of the thoracic segments are consistent with some species of Asaphellus. R. carleyi has been found in Ordovician strata of other parts of the world in association with asaphid trilobites.