a new stalked filter-feeder from the middle cambrian burgess shale, british columbia, canada一个新的跟踪中寒武世伯吉斯页岩的滤食动物,不列颠哥伦比亚,加拿大.pdfVIP

A New Stalked Filter-Feeder from the Middle Cambrian Burgess Shale, British Columbia, Canada Lorna J. O’Brien1,2*, Jean-Bernard Caron1,2 1 Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada, 2 Palaeobiology division, Department of Natural History, Royal Ontario Museum, Toronto, Ontario, Canada Abstract Burgess Shale-type deposits provide invaluable insights into the early evolution of body plans and the ecological structure of Cambrian communities, but a number of species, continue to defy phylogenetic interpretations. Here we extend this list to include a new soft-bodied animal, Siphusauctum gregarium n. gen. and n. sp., from the Tulip Beds (Campsite Cliff Shale Member, Burgess Shale Formation) of Mount Stephen (Yoho National Park, British Columbia). With 1,133 specimens collected, S. gregarium is clearly the most abundant animal from this locality. This stalked animal (reaching at least 20 cm in length), has a large ovoid calyx connected to a narrow bilayered stem and a small flattened or bulb-like holdfast. The calyx is enclosed by a flexible sheath with six small openings at the base, and a central terminal anus near the top encircled by indistinct openings. A prominent organ, represented by six radially symmetrical segments with comb-like elements, surrounds an internal body cavity with a large stomach, conical median gut and straight intestine. Siphusauctum gregarium was probably an active filter-feeder, with water passing through the calyx openings, capturing food particles with its comb- like elements. It often occurs in large assemblages on single bedding planes suggesting a gregarious lifestyle, with the animal living in high tier clusters. These were probably buried en masse more or less in-