Late Ordovician cornulitids from Anticosti Island, eastern Canada, and their evolutionary implications

Two Late Ordovician cornulitid species, Cornulites richmondensis (Miller, 1874) and Cornulites hemistriatus new species, from the Ellis Bay and Vaureal formations of Anticosti Island, eastern Canada, are each shown in this study to have a thick, punctate, cross-bladed lamellar, calcitic conch wall, a crested fold, a septate juvenile part, and endoconic chamber deposit. These Late Ordovician, free-living (i.e., nonencrusting) forms of Cornulites Schlotheim, 1820 have characters intermediate between Cornulites and the late Silurian-Devonian forms of Tentaculites Schlotheim, 1820, particularly by having incipient inner layers and poorly fused annuli, but lacking cornulitid-type vesicular microstructures. The described cornulitids are similar to brachiopods in their cross-bladed lamellae and pseudopunctae, but their lamellar layers are considerably finer and much less distinct than those of brachiopod shells.