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CHAPTER EIGHTEEN Ecology of Nontrilobite Arthropods and Lobopods in the Cambrian Arthropods and lobopods first appear for certain in the body fossil record in the Atdabanian and, at the time of this appearance, already exhibit a wide spread of ecologic strategies. | 18-C1099 8 10 00 2 19 PM Page 404 CHAPTER EIGHTEEN Graham E. Budd Ecology of Nontrilobite Arthropods and Lobopods in the Cambrian Arthropods and lobopods first appear for certain in the body fossil record in the Atdabanian and at the time of this appearance already exhibit a wide spread of ecologic strategies. Investigation of Cambrian arthropod ecology is hampered however by three factors the paucity of authentic nontrilobite trace fossils the restriction of the wide variety of poorly sclerotized taxa to the principal Cambrian Lagerstätten which may not necessarily provide a representative aliquot of Cambrian environments and the continuing lack offirm consensus over the systematics of nontrilobite forms. Cambrian arthropod ecology is thus still largely based on functional morphology with as yet only a poor understanding of ecologic interactions and trophic webs. In recent years several promising areas for research into early arthropod ecologies have emerged including the study of previously unsuspected miniature taxa from Swedish orsten and the Canadian Mount Cap Formation. Such discoveries have demonstrated that Cambrian arthropods played a critical role at all levels of the trophic web as indeed they continue to do today. However a few strategies e.g. sessile filter feeding mineralization of limbs are probably not present in the Cambrian. Moreover the ecologic sophistication of Cambrian arthropods was limited by their relatively simple body plans involving a small number of tagmata as defined with reference to their segment types. This simplicity which reflects a primitive deployment of homeotic genes rather than the much more complex patterns seen in advanced arthropods may have been an important factor in distinguishing Cambrian from Recent ecologies. The recent recognition of the lobopods as an important morphologic grouping in the Cambrian was entirely unexpected. Although some distance must be covered before a full understanding of their systematics is .
