The most probable Eumetazoa among late Precambrian macrofossils

Abstract

In late Precambrian macrofossil assemblages ascribed to shallow-water marine benthos, remains of colonial bacteria, multicellular algae, giant protozoans, parazoans, and eumetazoans of various phyla were provisionally identified. However, the reliability of these definitions is vanishing due to limitations imposed by a specific preservation of Precambrian fossils, represented mainly by imprints or secondary external molds. A very limited number of taxa only possesses features which are indicative for their eumetazoan affinities. Thus, Vendoconularia triradiata had an inverted pyramidal theca covered with a complex sculpture alike that of some Cnidaria, (Scyphozoa?). Kimberella quadrata had a complicated non-metameric bilateral body, which left a wide variety of trace fossils of its intense locomotion, and, probably, could belong to the Trochozoa. Although morphological features of Keretsa brutoni were mostly lost during fossilization, it preserved an array of characteristics similar to those of arthropods, including antenna-like appendages, but lacking distinct trunk limbs and, probably, bilateral symmetry.