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Abstract: Complex internal anatomy is documented for the first time in a Neoproterozoic
soft-bodied invertebrate. New data suggests that Ventogyrus, originally described as a
sessile, boat-shaped form belonging to the enigmatic Neoproterozoic group Petalonamae, is
actually composed of three, identical modules, arranged around an axial rod. Each mod...
Citations
... 9,23,24 Among putative Ediacaran animals are a group of macrofossils with a distinctive triradial, discoidal bodyplan, known from the White Sea assemblage of Australia and Russia [25][26][27][28][29][30][31] and potentially from late Ediacaran sections of the Doushantuo Formation from Guizhou, China. 32 This group comprises the genera Tribrachidium, Anfesta, Albumares, Hallidaya, Skinnera, and Rugoconites, 25,[33][34][35][36][37] and might also include several other problematica in need of restudy (see 16 ). ...
... In contrast, L. tribrachialis shows a morphology reminiscent of better-characterized Ediacaran trilobozoans from Australia and Russia, 31,34,37,40 and at about 37 mm of diameter it falls neatly within the upper size range of these organisms. 40 Like Lobodiscus, all trilobozoans share a discoidal shield-like body often partitioned into three equal lobes, radial branches and/or bifurcating ridges, and three-radial or rotational symmetry. ...
The late Ediacaran Jiangchuan biota, from the Dengying Formation in eastern Yunnan, is well-known for its diverse macroalgal fossils, opening a window onto eukaryotic-dominated ecosystems from the late Neoproterozoic of South China. Although multiple lines of evidence suggest that metazoans had already evolved by the late Ediacaran, animal fossils have not yet been formally described from this locality. Here, we report a putative disc-shaped macrofossil from the Jiangchuan biota, Lobodiscus tribrachialis gen. et sp. nov. This specimen shows the triradial symmetry characteristic of trilobozoans, a group of Ediacaran macrofossils previously documented in Australia and Russia. Lobodiscus could record the youngest known occurrence of trilobozoans, strengthening taxonomic and ecological continuities between the Ediacaran “White Sea” and “Nama” assemblages. Our findings may expand the known paleogeographical distribution of trilobozoans and provide data for Ediacaran biostratigraphic correlations across the Yangtze block and globally, helping to track the diversification of early metazoan-grade organisms.
... Gehling (1991) suggested that, due to the major morphological differences between Pteridinium and other fronds, it was unlikely to be closely related to them, and instead proposed they could represent macrophytic algae or even members of the Vendozoa (later Vendobionta ;Seilacher 1992;Buss and Seilacher 1994), an idea that was supported by Grazhdankin and Seilacher (2002). Fedonkin (1990), Ivantsov and Fedonkin (2002), and Fedonkin and Ivantsov (2007) argued that the three-vaned architecture of Pteridinium meant it was best considered as a member of the "Trilobozoa" (together with other threefold Ediacaran taxa such as Tribrachidium and Anfesta). However, given the morphological and taphonomic evidence, we follow Erwin et al. (2011) in considering Pteridinium as an erniettomorph. ...
Pteridinium simplex is an iconic erniettomorph taxon best known from late Ediacaran successions in South Australia, Russia, and Namibia. Despite nearly 100 years of study, there remain fundamental questions surrounding the paleobiology and paleoecology of this organism, including its life position relative to the sediment–water interface, and how it fed and functioned within benthic communities. Here, we combine a redescription of specimens housed at the Senckenberg Forschungsinstitut und Naturmuseum Frankfurt with field observations of fossiliferous surfaces, to constrain the life habit of Pteridinium and gain insights into the character of benthic ecosystems shortly before the beginning of the Cambrian. We present paleontological and sedimentological evidence suggesting that Pteridinium was semi-infaunal and lived gregariously in aggregated communities, preferentially adopting an orientation with the long axis perpendicular to the prevailing current direction. Using computational fluid dynamics simulations, we demonstrate that this life habit could plausibly have led to suspended food particles settling within the organism's central cavity. This supports interpretation of Pteridinium as a macroscopic suspension feeder that functioned similarly to the coeval erniettomorph Ernietta , emblematic of a broader paleoecological shift toward benthic suspension-feeding strategies over the course of the latest Ediacaran. Finally, we discuss how this new reconstruction of Pteridinium provides information concerning its potential relationships with extant animal groups and state a case for reconstructing Pteridinium as a colonial metazoan.
... In this short span of geological history, the triradial and the associated hexaradial types of radial symmetry have defined the body plan of many animals. Of the Ediacaran fauna, triradial (hexaradial) species are described in the genera Albumares, Anfesta, Basisacculus, Coronacollina, Jampolium, Protechiurus, Pteridinium, Rangea, Rugoconites, Skinnera, Swartpuntia, Tribrachidium, Triforillonia, Vendoconularia, Ventogyrus, possibly, Fractofusus, etc. (Glaessner and Daily, 1959;Glaessner and Wade, 1966;Wade, 1969;Glaessner, 1979aGlaessner, , 1979bFedonkin, 1981Fedonkin, , 1984Fedonkin, , 1985Fedonkin, , 1990Jenkins, 1992;Narbonne et al., 1997;Gehling et al., 2000;Ivantsov and Fedonkin, 2002;Gehling and Narbonne, 2007;Fedonkin and Ivantsov, 2007;Clites et al., 2012;Vickers-Rich et al., 2013;Narbonne et al., 2014;Ivantsov et al., 2015Ivantsov et al., , 2018Ivantsov et al., , 2019cIvantsov, 2017a, b;Hall et al., 2018). The Early Cambrian sediments contain many small triradial initially carbonate tubular fossils identified as Angustiochreida or Anabaritida (Anabarites, Aculiochrea, Selindeochrea, etc.) (Abaimova, 1978;Val'kov, 1982;Kouchinsky et al., 2009). ...
... 2, figs. 6, 7; Fig. 1d)) lobes-antimeres (Narbonne et al., 1997;Fedonkin and Ivantsov, 2007;Vickers-Rich et al., 2013;Ivantsov, 2017a;Laflamme et al., 2018). Bilobate stalked Petalonamae on reconstructions are illustrated as subbilateral (having a single plane of glide reflection) or quasi-biradial (in which the secondorder rotary axis is replaced by a helical axis and there are two mutually perpendicular planes, a glide reflection plane, and a mirror reflection plane) (see, for example, excellent drawings by Peter Trusler in Narbonne et al., 2009;2014). ...
... Consequently, Charniodiscus had two glide reflection planes and a second-order axis (Fig. 1a). The triradial and hexaradial Ventogyrus and Rangea also had doublelayered lobes (Fedonkin and Ivantsov, 2007;Vickers-Rich et al., 2013). The free-lying forms of petalonamids had neither an axial stalk nor a basal disk and were subbilateral (Ernietta, Charnia (Pl. ...
... Rapid sedimentary casting of bag-like compartments is also documented in a range of co-occurring non-rangeomorph Ediacaran taxa. Among the most spectacular examples are in situ, vertically oriented populations of Charniodiscus in Zimnie Gory sections of the White Sea (Grazhdankin, 2014;Ivantsov, 2016), reclined but similarly frondose Pambikalbae and Arborea from Nilpena in South Australia (Jenkins & Nedin, 2007;Laflamme et al. 2018;Dunn et al. 2019;Droser et al. 2020) and globular tripartite Ventogyrus from the Onega River area of the White Sea (Ivantsov & Grazhdankin, 1997;Fedonkin & Ivantsov, 2007). All of these fossils have been variably infilled during event-bed sedimentation, yielding a taphonomic continuum from fully inflated 3D casts through to essentially 2D death-mask imprints. ...
Ediacaran rangeomorphs were the first substantially macroscopic organisms to appear in the fossil record, but their underlying biology remains problematic. Although demonstrably heterotrophic, their current interpretation as osmotrophic consumers of dissolved organic carbon (DOC) is incompatible with the inertial (high Re ) and advective (high Pe ) fluid dynamics accompanying macroscopic length scales. The key to resolving rangeomorph feeding and physiology lies in their underlying construction. Taphonomic analysis of three-dimensionally preserved Charnia from the White Sea identifies the presence of large, originally water-filled compartments that served both as a hydrostatic exoskeleton and semi-isolated digestion chambers capable of processing recalcitrant substrates, most likely in conjunction with a resident microbiome. At the same time, the hydrodynamically exposed outer surface of macroscopic rangeomorphs would have dramatically enhanced both gas exchange and food delivery. A bag-like epithelium filled with transiently circulated seawater offers an exceptionally efficient means of constructing a simple, DOC-consuming, multicellular heterotroph. Such a body plan is broadly comparable to that of anthozoan cnidarians, minus such derived features as muscle, tentacles and a centralized mouth. Along with other early bag-like fossils, rangeomorphs can be reliably identified as total-group eumetazoans, potentially colonial stem-group cnidarians.
... Ventogyrus also occurs only in the White Sea region. Originally described as a Pteridinium-like organism (Ivantsov & Grazhdankin, 1997), Ventogyrus is in fact composed of three modules, each with several transverse septa, arranged around an axial rod into an egg-shaped capsule (Fedonkin & Ivantsov, 2007). ...
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.
... The latter scenario refers to partially disintegrated specimens, with their smooth external membrane probably torn out. The frond anatomy would be then similar to that of the pteridiniid Ventagyrus, with tri-radially arranged series of chambers precisely reproduced by the sand fill (Fedonkin and Ivantsov, 2007), as well as to Pambikalbae from Ediacara (Jenkins, 2007) and Siphusauctum, their triradial possible relative in the Mid Cambrian Burgess Shale biota (O'Brien and Caron, 2012). ...
Around the Ediacaran-Cambrian transition, about 540 million years ago, marine organisms began to dig in the sediment that has resulted in its better ventilation and further expansion of infaunal life. Few vertical infaunal burrows are known from the Precambrian and they are usually attributed to sea anemones. Here we show that the enigmatic Ediacaran petalonamean ‘sea pens’ were able to penetrate sediment for more than one centimetre depth while anchoring the body in the microbial mat. Their growth, as evidenced by numerous well-preserved basal discs from the late Ediacaran Lomoziv Member of the Mohyliv Formation in Podolia, Ukraine, was under control of rhythmic sedimentation events and periodic microbial mat development. Size frequency distribution in classes of both the final disc size and growth retention stages show that their size increase was stepwise. Each discrete stage corresponds to deposition of a thin sediment layer and development of the microbial mat at its top. Podolia was located near the South Pole in the Ediacaran (Vendian) and such rhythmic sedimentation was probably connected with the local climate seasonality.
... The latter scenario refers to partially disintegrated specimens, with their smooth external membrane probably torn out. The frond anatomy would be then similar to that of the pteridiniid Ventagyrus, with tri-radially arranged series of chambers precisely reproduced by the sand fill (Fedonkin and Ivantsov, 2007), as well as to Pambikalbae from Ediacara (Jenkins, 2007) and Siphusauctum, their triradial possible relative in the Mid Cambrian Burgess Shale biota (O'Brien and Caron, 2012). ...
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... Fossil remains typical for Petalonamae, such as Pteri dinium simplex Gürich, 1933 and Ernietta plateauensis Pflug, 1966, are completely composed of such mem branes and lack other structures. However, others (Rangea schneiderhoehni Gürich, 1930, Ventogyrus chistyakovi Ivantsov et Grazhdankin, 1997) had a short axial rachis, with membranes of the first order attached to it (Fedonkin and Ivantsov, 2007;Vickers Rich et al., 2013). The stalk with basal disk of Charnio discus can be regarded with certainty as a modified rachis and this extinct genus can be included in the system of Petalonamae. ...
Reconstruction and new description of the rare species Charniodiscus yorgensis Borchvardt et Nessov, 1999, which has previously been represented by a single, presently lost specimen, is provided. New material collected in the type locality and closely situated outcrops of Zimnii Bereg of the White Sea allows reconstruction of the structure of this fossil form in more detail. Like other species of the genus Charniodiscus Ford, 1958, the specimen of C. yorgensis, replaced by pyrite initially nonmineralized skeleton of an organism, consisted of a bilobate frond with the rachis passing downwards into the basal disk. It is shown that each lobe of the frond of C. yorgensis was an entire membrane arranged in transverse folds, as an accordion. Plicate lateral lobes, with their free margins directed upwards, adjoin sharp ridges of folds on either side of the membrane. Semipouches formed of bends of lateral lobes were probably the bases of tubular or seedlike elements of branches of the second order, recognized in C. oppositus Jenkins et Gehling, 1978 and C. arboreus (Glaessner, 1959) from Australian localities. Unique records of C. yorgensis buried in an upstanding position corroborate the well-known hypothesis of the vertical lifetime orientation of Charniodiscus.
... 2), or from three-dimensional specimens in-filled by sediment (e.g. [49,50]). However, such typically lobate structures do not exhibit the wavy fibrous symmetry of H. quadriformis. ...
... 2), or from three-dimensional specimens in-filled by sediment (e.g. [49,50]). However, such typically lobate structures do not exhibit the wavy fibrous symmetry of H. quadriformis. ...
Muscle tissue is a fundamentally eumetazoan attribute. The oldest evidence for fossilized
muscular tissue before the early Cambrian has hitherto remained moot, being reliant upon
indirect evidence in the form of late Ediacaran ichnofossils. We here report a candidate
muscle-bearing organism, Haootia quadriformis n. gen., n. sp., from ~560 Ma strata in
Newfoundland, Canada. This taxon exhibits sediment molds of twisted, superimposed fibrous bundles arranged quadrilaterally, extending into four prominent bifurcating corner branches.
Haootia is distinct from all previously published contemporaneous Ediacaran macrofossils in
its symmetrically fibrous, rather than frondose, architecture. Its bundled fibers, morphology,
and taphonomy compare well with the muscle fibers of fossil and extant Cnidaria,
particularly the benthic Staurozoa. H. quadriformis thus potentially provides the earliest body
fossil evidence for both metazoan musculature, and for Eumetazoa, in the geological record.
