Revision of the Silurian encrinurine trilobite Wallacia Lamont 1978, with species from Gotland and Canada

A group of late Llandovery and, exceptionally, earliest Wenlock encrinurine trilobites from the Baltic area, the British Isles, and Canada, is recognized as monophyletic. The generic name Wallacia Lamont 1978 is available for this group.Wallacia is regarded as sister taxon to Encrinurus sensu stricto. A systematic revision of species from Gotland recognizes W. laevis (Angelin 1851), from the Upper Visby Beds, and W. jaanussoni n. sp. and W. masterleei n. sp. from the Lower Visby Beds. Cladograms based on seventeen characters for the ten named species of Wallacia place W. masterleei and W. laevis as the closest relatives of a Canadian Telychian clade that includes W. elegantula (Billings 1866),W. chattertoni n. sp., and W. hypolepra (Stearn 1956).