Scratch Traces of Large Ediacara Bilaterian Animals

Abstract

Ediacara fan-shaped sets of paired scratches Kimberichnus teruzzii from the Ediacara Member of the Rawnsley Quartzite, South Australia, and the White Sea region of Russia, represent the earliest known evidence in the fossil record of feeding traces associated with the responsible bilaterian organism. These feeding patterns exclude arthropod makers and point to the systematic feeding excavation of seafloor microbial mats by large bilaterians of molluscan grade. Since the scratch traces were made into microbial mats, animals could crawl over previous traces without disturbing them. The trace maker is identified as Kimberella quadrata, whose death masks co-occur with the mat excavation traces in both Russia and South Australia. The co-occurrence of animals and their systematic feeding traces in the record of the Ediacara biota supports previous trace fossil evidence that bilaterians existed globally before the Cambrian explosion of life in the ocean.

The advent of animals: The view from the Ediacaran

“…Notable aspects of this radiation include dramatic increases in mobility (18); the appearance of undisputed bilaterians, such as burrowing organisms and stem-group mollusks (e.g., refs. 23 and 24); the advent of sexual reproduction (25); the appearance of the first biomineralizers (26,27); and the advent of active heterotrophy by multicellular organisms (24,(28)(29)(30)31).…”

“…Although a terrestrial origin was recently proposed (35), this hypothesis has been rigorously tested and is not consistent with any of the sedimentologic data (31,34,(36)(37)(38)(39)(40). Fossils of the Ediacara Biota are indeed preserved in a variety of marine environments (2), from outer shelf and slope settings in volcanic sediments of forearc basins of the Avalon Terrane (41,42) to prograding carbonate platforms such as southern China (43,44) and shallow marine prograding siliciclastic environments of the east European Platform (19,20,45,46).…”

“…1F) from the Ediacara Member of the Rawnsley Quartzite, South Australia, and the Verkhovka Formation, Zimnie Gory Formation, and in the basal part of the Erga Formation of the White Sea region of northwestern Russia. From their orientation and proximity, these body and trace fossils are interpreted as evidence of mat grazing activities (31,54,55). The suggestions of molluscan affinities for Kimberella (23,24,53) should not overlook some important differences from extant gastropod grazing behaviors (31,56).…”

“…From their orientation and proximity, these body and trace fossils are interpreted as evidence of mat grazing activities (31,54,55). The suggestions of molluscan affinities for Kimberella (23,24,53) should not overlook some important differences from extant gastropod grazing behaviors (31,56). Two genera of the so-called dickinsoniomorphs, Dickinsonia (Fig.…”

The Ecological Physiology of Earth's Second Oxygen Revolution

“…By contrast, large triploblastic Ediacaran organisms, such as Kimberella (commonly but not definitively thought to be related to the mollusks; Fedonkin et al 2007, Vinther 2015, moved across the seafloor, making extensive scratch marks on the sediment surface (Gehling et al 2014). The combination of Kimberella's size, locomotion, and feeding mode would have required both a blood vascular system and much higher minimum oxygen levels than those of rangeomorphs.…”