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A New Dickinsonid from the Upper Vendian of the White Sea Winter Coast (Russia, Arkhangelsk Region)
Abstract
A description and reconstruction of the new fossil are based on the rounded isometric imprints, which are composed of two rows of transverse elements. The elements are arranged in the manner of glide reflection symmetry. The lateral flanks of the elements are pointed and curved in identical directions. It is suggested that this fossil was preserved as imprints of different appearances (positive and negative) including "trilobite-like" forms. The relief of the imprints could be positive or negative. The fossils occur as isolate imprints or in accumulations.
... The upper one is a 10 cm thick sandstone bed that extends for at least 200 m laterally without any significant change in thickness. The fossil assemblage in this horizon is dominated by large specimens of Yorgia (Ivantsov, 1999;Dzik and Ivantsov, 1999). A much more diverse fossil assemblage has been recovered from the soles of sandstone lenses about 3 m below. ...
... Since Runnegar (1982), it has been generally accepted that the quilt of the dickinsoniid dipleurozoans was contractile and easily changed its shape while being enveloped by the sediment. This applies as well to the White Sea Yorgia (Ivantsov, 1999;Dzik & Ivantsov, 1999) and probably also to Podolimirus, if it is truly a dipleurozoan. ...
... Ventral view of sandstone slab PIN 3993/5018 with Yorgia waggoneriIvantsov (1999) from the Erga Formation, Zimnie Gory, Yorgia locality on the White Sea shore, Russia, showing sand injecting the space between the ventral body covers and dorsal 'quilt' (low angle light from SE; modified afterDzik and Ivantsov, 2002, Fig. 3A). ...
Fossiliferous strata of the late Ediacaran Lomoziv Member of the Mohyliv Formation, once known from now flooded outcrops along the Dniester River, have been recently exposed in a large quarry near the Novodnistrovs'k electric plant dam in Podolia, Ukraine. Finely bedded arkosic sandstone with claystone/siltstone intercalations is locally rich in 'elephant skin' surfaces indicating original presence of microbial mats. Imprints of soft-bodied organisms frequently occur on the sole surfaces of the sandstones. There are no signs of early diagenetic cementation with iron sulfides and the fossils are usually strongly compacted, with low relief. Specimens of bilaterally symmetrical latest Precambrian animals newly collected at the quarry offer additional evidence that their bodies had a complex internal anatomy. This relates especially to Podolimirus mirus, previously known from only fragmentary specimens representing only marginal parts of its chambered organ ('quilt'). It appears that there is a large region of the body in front of the 'quilt', with a lobate organ resembling bifurcating anterior structures earlier thought to represent intestinal diverticula in other dickinsoniids. The 'quilt' (presumably a dorsal muscular organ) of Podolimirus has a deep medial sinus that may have hosted a cylindrical axial organ analogous to that reported in the dickinsoniids from northern Russia and Australia.
... Another crucial consideration that the potential segmentation/metamerism, which apparently occurred in Dickinsonia, Yorgia and several related Ediacaran taxa ( fig. 2), was commonly presumed to be very distinct from true bilaterian segmentation: "these organisms consisted of two rows of right and leftside identical "halfsegments" (isomers) located along its longitudinal axis in line with the principle of glide reflection symmetry …, not of a series of segments as in most Articulata" (fig. 2;Ivantsov, 1999Ivantsov, , 2013. Despite potential exceptions (Waggoner, 1996;Ivantsov et al., 2019b) this type of symmetry is rare in true bilaterians, but very common in the majority of evidently sedentary Ediacaran forms, such as Rangeomorpha ( fig. 2) (MacCall, 2006;Xiao & Laflamme, 2008;Dunn et al., 2021), and also very frequent in plants (Ivantsov, 2013: 253). ...
Various evaluations of the last common bilaterian ancestor ( lcba ) currently suggest that it resembled either a microscopic, non-segmented motile adult; or, on the contrary, a complex segmented adult motile urbilaterian. These fundamental inconsistencies remain largely unexplained. A majority of multidisciplinary data regarding sedentary adult ancestral bilaterian organization is overlooked. The sedentary-pelagic model is supported now by a number of novel developmental, paleontological and molecular phylogenetic data: (1) data in support of sedentary sponges, in the adult stage, as sister to all other Metazoa; (2) a similarity of molecular developmental pathways in both adults and larvae across sedentary sponges, cnidarians, and bilaterians; (3) a cnidarian-bilaterian relationship, including a unique sharing of a bona fide Hox-gene cluster, of which the evolutionary appearance does not connect directly to a bilaterian motile organization; (4) the presence of sedentary and tube-dwelling representatives of the main bilaterian clades in the early Cambrian; (5) an absence of definite taxonomic attribution of Ediacaran taxa reconstructed as motile to any true bilaterian phyla; (6) a similarity of tube morphology (and the clear presence of a protoconch-like apical structure of the Ediacaran sedentary Cloudinidae) among shells of the early Cambrian, and later true bilaterians, such as semi-sedentary hyoliths and motile molluscs; (7) recent data that provide growing evidence for a complex urbilaterian, despite a continuous molecular phylogenetic controversy. The present review compares the main existing models and reconciles the sedentary model of an urbilaterian and the model of a larva-like lcba with a unified sedentary(adult)-pelagic(larva) model of the lcba .
... Dickinsonia specimens were first discovered in the Ediacara deposits of Flinders Ranges, South Australia, and later in various localities in Russia and Ukraine, notably in the White Sea of the Arkhangelsk region, ranging 567-550 mya (F. S. Dunn et al., 2018;Fedonkin, Gehling, Grey, Narbonne, & Vickers-Rich, 2007;Dima Grazhdankin, 2004). Yorgia specimens are likewise found in deposits in the White Sea area (A Yu Ivantsov, 1999). The latest Dickinsonia specimens thus predate the onset of the Cambrian (~540-485 mya) and the associated ecological changes (NJ Butterfield, 2009;Nicholas Butterfield, 2018;Saltzman et al., 2011;Sperling et al., 2013;Van De Velde, Mills, Meysman, Lenton, & Poulton, 2018) by about 10 million years. ...
This thesis is about the complicated and multifaceted problem of the evolution of the
eumetazoan body plan and its key role in the emergence of organismal complexity in
the animal kingdom. As such, it draws on a very broad range of topics and discussions
including empirical research programmes in palaeontology, comparative morphology,
classical and genetic developmental biology, and morphological and molecular
phylogenetics; as well as theoretical/philosophical research around the conceptual
bases of phylogenetics, homology, scientific integration, and biological complexity and
individuality. In the following chapters, I first provide background on and an outline
of the thesis (chapter 1); I then propose an overarching conceptual framework for the
integration of different kinds of evidence in macroevolutionary biology (chapter 2),
with a special emphasis on the integration of morphological and developmental genetic
evidence in inferring morphological homology (chapter 3); followed by providing a
phylogeny of the major animal groups incorporating the two Ediacaran fossils
Dickinsonia and Yorgia (chapter 4) and building on this phylogenetic placement to
propose a novel evolutionary scenario for the evolution of key features of the
eumetazoan body plan—namely the gastric cavity and bilateral symmetry—in light of
Dickinsonia and other Ediacaran fossils (chapter 5). I finish with a discussion on the
evolution of complexity in the animal kingdom in light of preceding chapters and the
multilevel selection literature (chapter 6), and a brief final conclusion.
... Besides Tribrachidium heraldicum, this rich fossil complex contains Andiva ivantsovi, Archaeaspinus fedonkini, Armilifera parva, Aspidella terranovica, Charniodiscus yorgensis, Cyanorus singularis, Dickinsonia costata, D. lissa, D. cf. tenuis, Eoporpita medusa, Harlaniella ingriana, Ivovicia rugulosa, Jampolium tripartitum, Keretsa brutoni, Kimberella quadrata, Margaritiflabellum anatolii, Cephalonega stepanovi, Paravendia janae, Parvancorina minchami, Staurinidia crucicula, Temnoxa molliuscula, Yorgia waggoneri, as well as the feeding traces, Epibaion and Kimberichnus [3,4,16]. The assumed trace is an arcuately curved wide flat band (shallow depression on the imprint), extending from the shield-like body (Figure 3c,d). ...
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.
... in Yorgia wagonneri ( Fig. 3; Ivantsov, 1999), Anfesta stankovskii (Fedonkin, 1984) and Albumares brunsae (Keller & Fedonkin, 1977), as well as Cyanorus singularis (Ivantsov, 2004), the latter of which seems to show both external rugosity and internal branching structures (plate 1 and figs 1-6 in Ivantsov, 2004; see also discussion in Dzik & Martyshyn, 2015). ...
The earliest evolution of the animals remains a taxing biological problem, as all extant clades are highly derived and the fossil record is not usually considered to be helpful. The rise of the bilaterian animals recorded in the fossil record, commonly known as the 'Cambrian explosion', is one of the most significant moments in evolutionary history, and was an event that transformed first marine and then terrestrial environments. We review the phylogeny of early animals and other opisthokonts, and the affinities of the earliest large complex fossils, the so-called 'Ediacaran' taxa. We conclude, based on a variety of lines of evidence, that their affinities most likely lie in various stem groups to large metazoan groupings; a new grouping, the Apoikozoa, is erected to encompass Metazoa and Choanoflagellata. The earliest reasonable fossil evidence for total-group bilaterians comes from undisputed complex trace fossils that are younger than about 560 Ma, and these diversify greatly as the Ediacaran-Cambrian boundary is crossed a few million years later. It is generally considered that as the bilaterians diversified after this time, their burrowing behaviour destroyed the cyanobacterial mat-dominated substrates that the enigmatic Ediacaran taxa were associated with, the so-called 'Cambrian substrate revolution', leading to the loss of almost all Ediacara-aspect diversity in the Cambrian. Why, though, did the energetically expensive and functionally complex burrowing mode of life so typical of later bilaterians arise? Here we propose a much more positive relationship between late-Ediacaran ecologies and the rise of the bilaterians, with the largely static Ediacaran taxa acting as points of concentration of organic matter both above and below the sediment surface. The breaking of the uniformity of organic carbon availability would have signalled a decisive shift away from the essentially static and monotonous earlier Ediacaran world into the dynamic and burrowing world of the Cambrian. The Ediacaran biota thus played an enabling role in bilaterian evolution similar to that proposed for the Savannah environment for human evolution and bipedality. Rather than being obliterated by the rise of the bilaterians, the subtle remnants of Ediacara-style taxa within the Cambrian suggest that they remained significant components of Phanerozoic communities, even though at some point their enabling role for bilaterian evolution was presumably taken over by bilaterians or other metazoans. Bilaterian evolution was thus an essentially benthic event that only later impacted the planktonic environment and the style of organic export to the sea floor.
... (6) Bilateromorpha, as the name says, comprise organisms with a bilaterally symmetric body (i.e., that consists of mirror image halves) (Fedonkin et al., 2007b). (7) Dickinsoniomorpha are flat and thin, at first glance bilaterally symmetric forms that consist of large number of segments, with one segment having a distinctive crescent shape and superficially resembling an arthropodal head-shield; the segments of the two sides do not line up perfectly along the midline, however, but are offset, are alternate, a kind of symmetry known as glide reflection (as opposed to mirror reflection symmetry ) (Ivantsov, 1999Ivantsov, , 2001Ivantsov, , 2004Ivantsov, , 2007). (8) Petalonamae, an imperfectly defined group dominated by serially quilted body plans, most exotic to mainstream biology; their mouldic preservation within sandstone is intriguing in that the specimens appear in variously curved and oriented shapes, approximately resembling internal moulds of pots and troughs (Pflug, 1972; Grazhdankin and Seilacher, 2002) (Figure 1). ...
DefinitionEdiacaran period: An interval in the history of earth after the Marinoan/Varanger glaciation of the Neoproterozoic Era (see Chapter Snowball Earth), but before the Cambrian radiations. This interval marks the introduction of complex macroscopic organisms, leading to a revolution in the structure and evolution of marine paleocommunities, including the establishment of multi-level trophic structures, coevolutionary predator–prey interactions and infaunal activity.Ediacaran biota: A highly distinctive assemblage of Ediacaran-age macroscopic organisms preserved as casts and moulds in siliciclastic, volcaniclastic, and carbonate sediments.IntroductionEdiacaran biota is a heterogeneous assemblage representing the earliest known communities of macroscopic organisms. Diverse Ediacaran fossil assemblages are coeval with the earliest phosphatized metazoan embryos (Xiao et al., 1998; but see Bailey et al., 2007; Xiao et al., 2007), the earliest undisputed traces of ...
... The body of rangeomorphs was compartmentalized into a fractal network of branched tubular structures (Narbonne, 2004;Grazhdankin and Seilacher, 2005;Narbonne et al., 2009) (Fig. 1.7). Dickinsoniomorpha are flat and thin, at first glance bilaterally symmetric forms that consist of a large number of segments, with one segment having a distinctive crescent or rhomboidal shape and superficially resembling an arthropodal head-shield; the segments of the two sides do not line up perfectly along the midline, however, and instead show offset or alternate glide reflection symmetry (as opposed to mirror reflection symmetry) (Ivantsov, 1999(Ivantsov, , 2001(Ivantsov, , 2004(Ivantsov, , 2007 (Fig. 1.3). Petalonamae, an imperfectly defined group dominated by serially quilted body plans, is most exotic to mainstream biology; their moldic preservation within sandstone is intriguing in that the specimens appear in variously curved and oriented shapes, approximately resembling internal moulds of pots and troughs (Ivantsov and Grazhdankin, 1997;Grazhdankin and Seilacher, 2002) (Fig. 1.4). ...
When each of the Avalon-, Ediacara-, and Nama-type fossil assemblages are tracked through geological time, there appear to be changes in species composition and diversity, almost synchronized between different sedimentary environments, allowing a subdivision of the late Ediacaran into the Redkinian, Belomorian and Kotlinian geological time Intervals. The Redkinian (580-559 Ma) is characterized by first appearance of both eumetazoan traces and macroscopic organisms (frondomorphs and vendobionts) in a form of Avalon-type communities in the inner shelf environment, whereas coeval Ediacara-type communities remained depauperate. The Belomorian (559-550 Ma) is marked by the advent of eumetazoan burrowing activity in the inner shelf, diversification of frondomorphs, migration of vendobionts from the inner shelf into higher energy environments, and appearance of tribrachiomorphs and bilateralomorphs. Ediacaran organisms formed distinctive ecological associations that coexisted in the low-energy inner shelf (Avalon-type communities), in the wave-and current-agitated shoreface (Ediacara-type communities), and in the high-energy distributary systems (Nama-type communities). The Kotlinian (550-540 Ma) witnessed an expansion of the burrowing activity into wave-and current-agitated shoreface, disappearance of vendobionts, tribrachiomorphs and bilateralomorphs in wave-and current-agitated shoreface, together with a drop in frondomorph diversity. High-energy distributary channel systems of prodeltas served as refugia for Nama-type communities that survived until the end of the Ediacaran and disappeared when the burrowing activity reached high-energy environments. This pattern is interpreted as an expression of ecosystem engineering by eumetazoans, with the Ediacaran organisms being progressively outcompeted by bilaterians.
For almost 150 years, megascopic structures in siliciclastic sequences of terminal Precambrian age have been frustratingly difficult to characterize and classify. As with all other areas of human knowledge, progress with exploration, documentation and understanding is growing at an exponential rate. Nevertheless, there is much to be learned from following the evolution of the logic behind the biological interpretations of these enigmatic fossils. Here, I review the history of discovery as well as some long-established core members of widely recognized clades that are still difficult to graft on to the tree of life. These ‘orphan plesions’ occupy roles that were once held by famous former Problematica, such as archaeocyaths, graptolites and rudist bivalves. In some of those cases, taxonomic enlightenment was brought about by the discovery of new characters; in others it required a better knowledge of their living counterparts. Can we use these approaches to rescue the Ediacaran orphans? Five taxa that are examined in this context are Arborea (Arboreomorpha), Dickinsonia (Dickinsoniomorpha), Pteridinium plus Ernietta (Erniettomorpha) and Kimberella (Bilateria?). With the possible exception of Dickinsonia , all of these organisms may be coelenterate grade eumetazoans.
Re-evaluation of eumetazoan modular coloniality gives a new perspective to Ediacaran–Ordovician animal diversification. Highly integrated eumetazoan colonies (porpitids [“chondrophorines”], pennatulacean octocorals, anthozoans) prove to be unknown in the Ediacaran. Ediacaran Evolutionary Radiation (EER, new term) fossils include macroscopic and multicellular remains that cannot be compellingly related to any modern group. Claims of eumetazoan coloniality in the Ediacaran are questionable. The subsequent Cambrian Evolutionary Radiation (CER, terminal Ediacaran–late early Cambrian) records appearance and diversification of deep burrowers and a relatively abrupt development of biomineralization. The CER began in a transition zone that spans the Ediacaran–Cambrian boundary and includes the final few million years of the Ediacaran. The early CER has pseudocolonial(?) Corumbella that may be related to some Phanerozoic taxa (conulariids) and records appearance of the first macroscopic biomineralised organisms (Cloudina, Namacalathus, Namapoikea), which may not be eumetazoans. Modular eumetazoans dominate and define many Ordovician and younger habitats (coral, bryozoan, sabellitid reefs; pelagic larvaceans, salps, early–middle Palaeozoic graptolites), but eumetazoan coloniality largely “missed” the EER and CER. All purported Ediacaran–Ordovician porpitids (“chondophorines”) and pennatulaceans are not colonial eumetazoans. Only in the late early Cambrian (late CER) or early middle Cambrian do a few modular colonial eumetazoans first occur as fossils. These include Sphenothallus (available evidence precludes Torellella coloniality), some corals (colonial “coralomorphs”), and lower middle Cambrian graptolithoids. Modular eumetazoan colonies (corals, graptolithoids) in the late early and early middle Cambrian (late Epoch 2–early Epoch 3) and appearance of mid-water predators (cephalopods, euconodonts) and bryozoans in the late Cambrian–earliest Ordovician (late Furongian–early Tremadocian) are the root for the Great Ordovician Biodiversification Interval (GOBI, new term) and diverse later Phanerozoic communities.
A new dickinsoniid from a recently discovered fossiliferous horizon within the Mezen Formation at the White Sea shore in Russia shows details of internal anatomy exquisitely preserved in fine sediment. In several specimens, the dorsal segmented unit was specifically deformed under the sudden sediment load. As a result, dense internal organs are reproduced as furrows on the lower bedding surface, whereas those which easily collapsed as oval elevations. This pattern corresponds to the distribution of probable intestinal caeca in Dickinsonia and probable gonads in Yorgia. A pharyngeal structure is represented by a circular imprint and the intestine by a wide axial furrow.
-Reconstructions of the habitats and taphonomic environments of soft-bodied metazoans are given for the Upper Vendian of Arkhangelsk District (White Sea Winter Coast). Soft-bodied biota inhabited almost all hydrodynamic zones of the Zimnie Gory Section of the paleobasin: relatively undisturbed environments near the seafloor where sedimentation of distal tempestite fans occurred below the storm wave base, relatively deep and narrow gutters along strong storm-generated currents, and shoals with permanent wave agitation. In some cases, a correlation between taphocoenonoses and relatively narrow facial zones can be demonstrated, and biotopes of soft-bodied organisms can be identified. The presence of a fossil assemblage with typical Ediacarian representatives in alluvial sandstones extends our knowledge on habitat environments of Precambrian organisms.