duration; over 50 metazoan orders first appear in the record during that interval (Valentine et al., 1991).
Vendian Faunas. The earliest fossils that may be metazoans are preserved in two modes. One is as body fossils, chiefly as impressions in this case. Most of these fossils somewhat resemble cnidarians but many cannot easily be assigned to living classes, and their affinities even as to kingdom are in dispute. Seilacher (1989) has suggested that most of them are not metazoans at all but represent a separate, extinct multicellular clade; they are suggested to have fed via symbionts as chemautotrophs (Seilacher, 1989), phototrophs, or osmotrophs (McMenamin, 1993). However, especially well-preserved specimens of "medusoid"