EmeraldellaandLeanchoilia,two arthropods from the Burgess Shale, Middle Cambrian, British Columbia

Abstract

The type species of 2 much discussed but hitherto poorly known genera of arthropods are described in detail from new preparations [E. brocki and L. superlata]. Photographs, explanatory line drawings and reconstructions including 3-dimensional models are included. The single species of Emeraldella, E.Brocki, is recognized, and the type and only specimen of Emeraldoides is referred to it. Synonymous with L. superlata are Walcott''s 3 spp. L. major, Bidentia difficilis and Emeraldella micrura, Simonetta''s, L. amphiction, L. persephone and L. protogonia. E. brocki may be allied with Molaria spinifera; problematical is any relationship to aglaspidids. L. superlata may be most closely related to Actaeus armatus. Emeraldella and Leanchoilia are disimilar and different from either Sidneyia or Naraoia; these 4 genera are so heterogeneous that Stormer''s grouping of them into the taxon Merostomoidea is rejected as no longer useful.