Publications

Lapworthellids are systematically problematical organisms known from highly variable, cone-like, commonly transversely ridged sclerites that may have longitudinal costae and transverse septa. These sclerites grew by basal-internal accretion and were external skeletal units. Recovery of ontogenetically fused sclerites from Lapworthella schodackensis (Lochman) suggests that many sclerites occurred in close juxtaposition and probably formed a multiplated external integument. Lapworthellids are apparently tommotiids that produced only high plates rather than sclerite morphologies such as the subsymmetrical to symmetrical conical and broad, low helicoid sclerites of the "mitrosagophorans." The Lapworthellidae (emended, includes "Kelanellidae"), Sunnaginiidae (new), and "Order Mitrosagophora" (=Tommotiidae (emended) and Tannuolinidae) are characterized by differences in skeleton construction and comprise the Order Tommotiida. Both the Tommotiida and the Machaeridia had multiunit, external skeletons but little evidence suggests that these groups are related or "sister" groups. Lapworthella schodackensis (Lochman) from the Taconic allochthon, eastern New York, is closely similar to and possibly conspecific with approximately coeval nodose forms from the Avalonian and Baltic platforms [Lapworthella cornu (Wiman, 1903)] and Siberian Platform (Lapworthella dentata Missarzhevsky, 1969). Lapworthella ludvigseni n. sp. from the sub-trilobitic and Tommotian Lower Cambrian of the Avalonian Platform has weakly annulated sclerites with adventitious septa.