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Representatives of Trilobozoa, a group of tri-radially symmetrical animals, were re-examined based on the material from a new, extensive collection of macrofossils from the Late Ediacaran (Vendian) sediments of the southeastern White Sea region. In addition to body imprints, the collection contains specimens suggesting that trilobozoans could move independently. The shield-like body of trilobozoans consisted of three antimeres. Each antimere has a cluster of grooves on the outer surface and an inner cavity. The system of branched grooves is interpreted as a ciliary organ for gathering food particles, and the elongated inner cavities associated with it are interpreted as digestive organs. It is suggested that trilobozoans were slow-moving benthic seston-feeders of a coelenterate level of organization. [ABSTRACT FROM AUTHOR]

There are multiple tri-radially symmetric taxa among the Ediacara Biota, but the tri-radial body plan is unique to this time; taxa with threefold symmetry go extinct by the beginning of the Cambrian. Many of these taxa are included in a morphogroup referred to as Trilobozoa or Triradialomorpha. Abundant specimens of these tri-radial taxa exist at the Nilpena National Heritage Ediacara fossil site and at other sites throughout Australia. Here, we review the occurrence and diversity of tri-radial genera from the Australian Ediacaran, including Albumares, Anfesta, Coronacollina, Hallidaya, Rugoconites, Skinnera and Tribrachidium and evaluate the possibility that their shared symmetry unites them phylogenetically. We find that, with the exception of Coronacollina, these taxa are morphologically similar enough to justify considering them a clade of related organisms. The diversity and abundances of these taxa in South Australia provide a unique venue for research investigating the relationships among these Ediacaran taxa. [ABSTRACT FROM AUTHOR]

We describe traces of macroorganisms in association with the body imprints of trace-producers from Ediacaran (Vendian) deposits of the southeastern White Sea region. They are interpreted as traces of locomotion and are not directly related to a food gathering. The complex remains belong to three species: Kimberella quadrata, Dickinsonia cf. menneri, and Tribrachidium heraldicum. They were found in three different burials. The traces have the form of narrow ridges or wide bands (grooves and linear depressions on natural imprints). In elongated Kimberella and Dickinsonia, the traces are stretched parallel to the longitudinal axis of the body and extend from its posterior end. In the case of the isometric Tribrachidium, the trace is directed away from the margin of the shield. A short length of the traces indicates that they were left by the organisms that were covered with the sediment just before their death. The traces overlaid the microbial mat with no clear signs of deformation under or around the traces. A trace substance, apparently, differed from the material of the bearing layers (i.e., a fine-grained sandstone or siltstone) and was not preserved on the imprints. This suggests that the traces were made with organic material, probably mucus, which was secreted by animals in a stressful situation. The mucus traced the movements of the organism before death. The discovered traces of locomotion are direct evidence of the ability of some Ediacaran macroorganisms to move independently.

Tribrachidium is a monospecific genus of the Ediacara biota found globally. In the Ediacara Member of the Rawnsley Quartzite, Flinders Ranges of South Australia, the spatial distribution of Tribrachidium across the seafloor is best described as patchy. Although Tribrachidium is the dominant fossil on two of the twenty-six beds currently excavated and is present in large numbers on another, the genus most commonly occurs as no more than a handful of specimens on a bed. Tribrachidium size frequency distributions of each of the three beds with more than 5 specimens are all statistically distinguishable from one another. Additionally, the size range on any given bed is smaller than the overall size range observed for the genus. These patterns suggest that these organisms lived in populations composed of single generations. The beds with numerous Tribrachidium come from different facies and are characterized by the presence of dissimilar mixes of taxa and textured organic surfaces, indicating that Tribrachidium was a generalist, able to adapt to a variety environments. Uniquely, the base or internal structure of Tribrachidium is also found preserved in both positive and negative relief as a sequence of concentric ridges on beds where Tribrachidium is the dominant genus. The most parsimonious explanation for the presence of these concentric ridge fossils is that they are the fossilized form of a Tribrachidium preserved when the organism was buried upside-down, flipped over, or dead and partially decayed prior to burial. [ABSTRACT FROM AUTHOR]

We describe traces of macroorganisms in association with the body imprints of trace-producers from Ediacaran (Vendian) deposits of the southeastern White Sea region. They are interpreted as traces of locomotion and are not directly related to a food gathering. The complex remains belong to three species: Kimberella quadrata, Dickinsonia cf. menneri, and Tribrachidium heraldicum. They were found in three different burials. The traces have the form of narrow ridges or wide bands (grooves and linear depressions on natural imprints). In elongated Kimberella and Dickinsonia, the traces are stretched parallel to the longitudinal axis of the body and extend from its posterior end. In the case of the isometric Tribrachidium, the trace is directed away from the margin of the shield. A short length of the traces indicates that they were left by the organisms that were covered with the sediment just before their death. The traces overlaid the microbial mat with no clear signs of deformation under or around the traces. A trace substance, apparently, differed from the material of the bearing layers (i.e., a fine-grained sandstone or siltstone) and was not preserved on the imprints. This suggests that the traces were made with organic material, probably mucus, which was secreted by animals in a stressful situation. The mucus traced the movements of the organism before death. The discovered traces of locomotion are direct evidence of the ability of some Ediacaran macroorganisms to move independently. [ABSTRACT FROM AUTHOR]