Upper Ordovician sponge spicules from Gondwana: New data from Peru and Libya

Abstract

The record of Middle to Upper Ordovician sponges outside Laurentia and north-Gondwana (=Australia) is too sparse that any new record significantly contribute to the global diversity and biogeographic knowledge of the group (Muir et al. 2013). Conspicuous spicule assemblages and a partially complete sponge have been recorded from Peru and Libya, from where isolated occurrences of Ordovician sponge spicules have been previously reported without any morphological or stratigraphic detail. The spicule association recorded from Peru comes from Sandbian beds on the lower part of the Calapuja Formation west of Lake Titicaca. It consists of isolated hexactins, pentactins and ropes or divergent tufts of elongate, large monaxons in subparallel orientation. Some of these monaxon groupings are clavate masses of slightly divergent, mainly smooth monaxons and some of them are ornamented. These forms resemble the genus Pyritonema McCoy (= Hyalostelia Hinde), commonly misinterpreted until the recent review by Botting (2005). Other spicule assemblages are related to root-tufts of hexactinellids with long monaxons including anchoring terminations. The spicules from the Upper Ordovician of Libya come from the basal horizon of the Melaz Shuqran Formation in the Tihemboka High, west of the Murzuq Basin. The assemblage consists of simple hexactines, hexactine-based stauracts and pentacts and some isolated large monaxons. Different size or rank of hexactines occurred; some of them in an apparent original arrangement. This association agrees with the characteristics of the protospongioid reticulosans.