Late Ordovician cornulitid tubeworms from high-latitude peri-Gondwana (Sardinia and the Pyrenees) and their palaeobiogeographic significance

Abstract

Seven Cornulites species, including a new one — Cornulites leonei n. sp., are described from the Upper Ordovician Portixeddu Formation (Katian, stage slices Ka2–3) of Sardinia and the Cavá (lower Katian, stage slice Ka2) and Estana (upper Katian, stage slices Ka3–4) formations of the Pyrenees. The Sardinian and Pyrenean cornulitids represent an adaptation to live in environments with high sedimentation rates and limited hard substrates availability. Their prominent annuli could have had a stabilizing function in the soft sediment that helped cornulitids to keep a favourable position in the sediment to enable suspension feeding. The known Late Ordovician cornulitid diversity in different Gondwana areas is low, usually ranging from one to three taxa, being higher (seven) in Sardinia. Like other benthic groups during the Late Ordovician, the cornulitid tubeworm faunas within the high-latitude peri-Gondwana Province indicate a certain endemism and share morphological and ecological affinities, such as a small body size and tubes with a strikingly small apical angle. Although essentially endemic, some links with cornulitids from the Late Ordovician of Scotland are revealed.