The Cabrières Biota of the Landeyran Formation in southern Montagne Noire, France is one of the key Early Ordovician faunas, as it represents a Lagerstätte close to the Ordovician South Pole. Sponges are a major component of this biota, despite their relatively lower abundance in comparison to algae and arthropods. Four distinct morphotypes of hexactinellids are described here. Three of them share characteristics that tubular reticulosans with closely spaced, subcircular, elongated oval or subsquare parietal gaps composed of slender-rayed hexactines or stauractines. This provides an excellent insight into a hintzespongiid affinity and probably indicating previously unknown groups. Another disarticulated spicule assemblage, composed of hexactines and diactines, tentatively suggests a protospongiid affinity. Additionally, two types of hexactinellid root tufts are documented. This distinctive sponge fauna differs markedly from its coeval tropical and temperate counterparts, offering a potential to investigate the Ordovician polar ecosystem through sponges.
Li et al. (Mon,) studied this question.