Yorgia

Abstract: Mobility represents a key innovation in the evolution of complex animal life. The ability to move allows for the exploration of new food sources, escapes from unfavorable environmental conditions, enhanced ability to exchange genetic material, and is one of the major reasons for the diversity and success of animal life today. The oldest widely accepted trace fossils of animal mobility are found in Ediacaran-aged rocks (635-539 Ma). The earliest definitive evidence for movement associated with exploitation of resources for feeding occurs in the White Sea assemblage of the Ediacara Biota-macroscopic, soft-bodied fossils of Ediacaran age. Here, we evaluate potential support for mobility in dickinsoniomorphs, presenting new data regarding abundant Dickinsonia and associated trace fossils from the Ediacara Member, South Australia. Results quantitatively demonstrate that Dickinsonia was capable of mobility on relatively short, ecological timescales. This organism was bilaterally symmetrical, likely moved via muscular peristalsis, and left trace fossils due to active removal of the organic mat related to feeding. Analogous structures associated with Yorgia indicate that it was also mobile and fed in a similar manner. Morphological evidence suggests that two other modular taxa, Andiva and Spriggina, were able to move but did not feed in a manner that impacted the organic mat. Together, these data suggest that mobility was present in multiple disparate bilaterally symmetrical Ediacaran taxa.

Abstract: Coutts, F.J., Gehling, J.G. & Garcia-Bellido, D.C., August 2016. How diverse were early animal communities? An example from Ediacara Conservation Park, Flinders Ranges, South Australia. Alcheringa 40, xxx–xxx. ISSN 0311-5518Fossils of the Ediacara biota record the earliest evidence of animal communities and, as such, provide an invaluable glimpse into the abiotic and biotic processes that helped shape the evolution of complex life on Earth. A diverse community of Ediacaran macro-organisms is preserved with high resolution in a fossil bed recently excavated from north Ediacara Conservation Park (NECP) in the Flinders Ranges, South Australia. Many of the commonly described Ediacaran taxa from the Flinders Ranges are represented on the bed surface and include: Parvancorina, Rugoconites, Spriggina, Dickinsonia, Tribrachidium, Kimberella, Charniodiscus and Yorgia, including two new taxa. Numerous additional fossil-bed fragments from the same locality were analysed that preserve a similar suite of taxa and shar...

Abstract: The Serebryanka and Sylvitsa groups on the western slope of the Urals characterize the Vendian section of the eastern folded framework of the East European Platform [1]. They are conspicuous against the background of the coeval platformal sequences by their relatively complete sedimentary record, sufficiently good outcrops, and opportunities for detailed sedimentological study both along and across the regional paleoslope. The tillite units serve as key elements of the stratigraphic framework of the Serebryanka Group. However, their number and continuity along the strike remain a matter of debate [1, 2]. The Sylvitsa Group comprises the following formations recognized on a regional scale (from bottom to top): Staropechny Formation (with a thin tillite unit at the base), Perevalok, Chernokamen, and Ust’-Sylvitsa formations. Their specific structural features serve as criteria for largescale correlation with Upper Vendian platformal sequences [1‐3]. The Ediacaran-type soft-bodied fossil biota is abundant in the Chernokamen Formation. The great density of fossil populations, the high taxonomic diversity of this biota, and the presence of endemic (for the Southeast White Sea region) taxons give grounds to suggest biogeographic links between the Central Ural and White Sea segments of the Late Vendian paleobasin [4]. The fossil biota from sedimentary rocks of the Chernokamen Formation comprises Cyclomedusa davidi Sprigg, Dickinsonia sp., Dickinsonia tenuis Glaessner et Wade, Ediacaria flindersi Sprigg, Eoporpita medusa Wade, Inaria khatyspytia (Vodanjuk), Irridinitus multiradiatus Fedonkin, Medusinites mawsoni (Sprigg), Nemiana simplex Palij, Paliella patelliformis Fedonkin, Palaeopascichnus delicatus Palij, Protodipleurosoma wardi Sprigg, Vaizitsinia sophia Sokolov et Fedonkin, and Yorgia sp. These data make it possible to correlate the Chernokamen Formation of the Central Urals with the reference section of the southeastern White Sea region. The Upper Vendian of the White Sea region includes a very characteristic taxon Yorgia , which appears for the first time in the Zimnegorsk Formation. However, insufficiently reliable stratigraphic and facies affiliations of the Sylvitsa Group and the absence of isotopic datings remained serious obstacles for such correlation until recently. In 2002, we found thin volcanic ash beds in the upper part of the Staropechny Formation. These beds are associated with the chocolate brown thin-bedded mudstones that crop out on the left bank of the Sylvitsa River downstream of the Kernos Creek. In 2003, volcanic ash beds, which are also closely related to the chocolate brown mudstones, were revealed in the Staropechny and Perevalok formations and in the lower subformation of the Chernokamen Formation in the Vilukha ravine on the left and right banks of the Us’va River. In 2004, ash beds were traced for 4.5 km in the lower subformation of the Chernokamen Formation along the Mezhevaya Utka River. In all the above cases, ash beds were readily discernible as a poorly cemented light gray (with pinkish, cream, and greenish hues) rock among the host chocolate brown mudstones. Members of chocolate brown mudstones with volcanic ash beds are important for Upper Vendian stratigraphy of the East European Platform. The tuffaceous rocks serve as key units for subdivision and correlation of outcrops and borehole sections [2, 3, 5, 6]. The most complete Upper Vendian platformal sections of the Mezen syneclise and the southeastern White Sea region

Abstract: A large animal, formally described as Yorgia waggoneri (Ivantsov, in press) has been discovered at a Vendian locality on the shore of the White Sea, in northern Russia. It is anatomically transitional between the Ediacaran “segmented worms”; Dickinsonia and Spriggina. Like Dickinsonia, it had a metameric dorsal quilt, composed of a series of muscular chambers, and presumed intestinal caeca. Yorgia was unlike Dickinsonia, but similar to Spriggina, Marywadea, and Praecambridium, in that the anterior part of the dorsal quilt did not overhang the caeca. Rather, it was displaced posteriorly, with the medial chamber arched to the left. In effect, a lunate anterior region with ramified caeca was exposed dorsally. The left and right series of chambers were asymmetric, alternating along the mid‐line. These organisms are not related to either annelids or arthropods, but possible homologies between characters of these animals and those of present day nemerteans and some deuterostomian phyla are proposed here.