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Parvancorina — an arthropod from the Late Precambrian (Ediacarian) of South Australia
Abstract
After consideration of the preservation of the remains of the flexible integuments of some 60 specimens of Parvancorina minchami GLAESSNER, 1958, from Ediacara, available details of their morphology are reviewed and interpreted in terms of growth, feeding and locomotion. Insufficient detail of their limbs is preserved to define unequivocally the systematic position and phylogenetic significance of Parvancorina. Resemblances with other fossils support assignment to the Arthropoda. The genus is believed to be related to Marrellomorpha which appear to be phylogenetically close to ancestral Trilobitomorpha. These are considered to have diversified into divergent lines of descent leading to Crustacea and Chelicerata, but Parvancorina is unlikely to have direct descendants among the living arthropods. Zusammenfassung Etwa 60 Exemplare von Parvancorina minchami GLAESSNER, 1958, von der Fund-stelle Ediacara wurden untersucht. Die Fossilisation ihrer oft deformierten und ursprüng-lich biegsamen Körperhülle wird beschrieben und Wachstum, Nahrungsaufnahme und Bewegung werden dargestellt. Der Bau der Gliedmaßen ist nicht in Einzelheiten erkenn-bar, so daß die systematische und phylogenetische Einordnung der Gattung nicht präzi-siert werden kann. Auf Grund der beobachteten Merkmale von Parvancorina und Ähnlich-keiten mit anderen Fossilien ist der Schluß berechtigt, daß sie zu den Arthropoden gehört. Parvancorina zeigt Verwandtschaftsbeziehungen zu Marrellomorpha und steht primitiven Trilobitomorpha nahe, aus denen nach heutigen Ansichten die Crustacea und Chelicerata hervorgegangen sind. Sie ist jedoch nicht als Ahnenform von rezenten Arthropoden anzusehen.
... This event is documented by the Cambrian fossil record, which depicts a coherent sequence of events, including the origins of bioturbation, biomineralization, animal reef systems, zooplankton, and the appearance of all major animal phyla in the 30 or so million years following the Ediacaran-Cambrian boundary (2,(7)(8)(9)(10). However, Precambrian ancestors to the Metazoa have long been sought (11)(12)(13), with exploration efforts yielding numerous and diverse paleontological discoveries in this interval of time (8,14). ...
... However, the anchor of Parvancorina lacks the anterior doublure and medial keel of the cephalic structure of Skania, meaning these structures are not homologous (109). The growth trajectory of Parvancorina does not match that of Skania (109,110), and neither do the segmentation arrangement and attachment location of the supposed appendages (13,109,111). The Ediacaran taxa Vendia and Praecambridium were also suggested to have euarthropodlike guts, gonads, and intestinal caeca (112), but these are better understood as postdeath wrinkling and osmotic contractions, in concert with xenomorphism of the thin bodied organism over the irregular sediment surface, comparable to the taphonomy of other taxa from the White Sea and global specimens of Dickinsonia (113). ...
... The exact timing of the origination of animals has long been the subject of debate, with many claims being made for Ediacaran age animals (12,13), including euarthropods (11,103,112). The development of molecular clocks during the 1990s (123) provided a stimulus for investigating the late Precambrian record for the earliest evolution of animals, as did the biomolecular preservation of sterols from approximately 640 Ma or younger (124, 125) (SI Appendix). ...
Euarthropoda is one of the best-preserved fossil animal groups and has been the most diverse animal phylum for over 500 million years. Fossil Konservat-Lagerstätten, such as Burgess Shale-type deposits (BSTs), show the evolution of the euarthropod stem lineage during the Cambrian from 518 million years ago (Ma). The stem lineage includes nonbiomineralized groups, such as Radiodonta (e.g., Anomalocaris) that provide insight into the step-by-step construction of euarthropod morphology, including the exoskeleton, biramous limbs, segmentation, and cephalic structures. Trilobites are crown group euarthropods that appear in the fossil record at 521 Ma, before the stem lineage fossils, implying a ghost lineage that needs to be constrained. These constraints come from the trace fossil record, which show the first evidence for total group Euarthropoda (e.g., Cruziana, Rusophycus) at around 537 Ma. A deep Precambrian root to the euarthropod evolutionary lineage is disproven by a comparison of Ediacaran and Cambrian lagerstätten. BSTs from the latest Ediacaran Period (e.g., Miaohe biota, 550 Ma) are abundantly fossiliferous with algae but completely lack animals, which are also missing from other Ediacaran windows, such as phosphate deposits (e.g., Doushantuo, 560 Ma). This constrains the appearance of the euarthropod stem lineage to no older than 550 Ma. While each of the major types of fossil evidence (BSTs, trace fossils, and biomineralized preservation) have their limitations and are incomplete in different ways, when taken together they allow a coherent picture to emerge of the origin and subsequent radiation of total group Euarthropoda during the Cambrian.
... The Ediacaran fossil Parvancorina is a small, anchor-shaped fossil displaying apparent bilateral symmetry, antero-posterior differentiation ( Fig. 2), and has been interpreted as a benthic marine animal with arthropod affinities ( Gehling, 1991;Laflamme et al., 2013;Lin et al., 2006;Sperling and Vinther, 2010). While it has been compared with Cambrian arthropods such as Skania ( Gehling, 1991;Glaessner, 1980;Lin et al., 2006) and Primicaris ( Zhang et al., 2003), recent revisions of morphologically similar Cambrian arthropods disagree ( Legg, 2015), so the phylogeny of Parvancorina is far from settled. Two species have been described: Parvancorina minchami ( Glaessner, 1959) is known from both the Flinders Ranges of South Australia and the White Sea region of northwestern Russia. ...
... Individuals of the genus Parvancorina generally range between 1 and 40 mm in length and are known from dorsal external molds on the soles of siliciclastic beds ( Naimark and Ivantsov, 2009). The main dorsal anatomy of Parvancorina consists of an anterolateral ridge intersected sagittally by a medial ridge ( Glaessner, 1980) ( Fig. 1), and based on their (apparent) consistent morphology from juveniles to adults, they have been described as probable direct developers, implying that they were mobile throughout post-embryonic growth ( Lin et al., 2006). However, the attribution of mobility, or any other informative ecological traits, when the only evidence of its existence are shallow concave impressions in siliciclastic beds, becomes problematic; thus, new applications for interpreting these fossils (e.g., spatial analyses) are necessary and could prove potentially revolutionary. ...
... Orientation was recorded using the widest end of the fossil. We excluded all specimens where we could not easily identify the anterolateral ridge or where we could not determine the wider end of the fossil (regarded as 'anterior') from the narrower end (regarded as 'posterior') ( Glaessner, 1980). To analyze the population structure of Parvancorina, it was first necessary to examine and quantify their growth patterns. ...
The ancient in situ fossil seafloor communities of the Ediacara biota present an unparalleled window into the assembly of the earliest complex macroscopic organisms, including early animals on Earth ca. 555 million years ago (mya). The unique preservation style of Ediacara fossil seafloors preserves whole communities virtually ‘frozen in time’, including both living and dead organisms at the time of burial. This phenomenon, where the fossilized organisms are arranged as they were in life offers an unparalleled opportunity to examine ecological patterns in some of the earliest examples of animal communities in deep time. The small, anchor-shaped fossil genus Parvancorina is common among the Ediacara biota; however, its morphology and ecology have received little attention. Here, we describe a population of juvenile Parvancorina preserved on a section of fossil seafloor recently excavated from the characteristic Ediacara Member from Ediacara Conservation Park in the Flinders Ranges, South Australia. We applied spatial methods to the sample population of Parvancorina (n = 202) and found that they demonstrated two size-clusters, distinguishing juveniles from adults, and further analyses showed that the smaller specimens tended to be spatially aggregated. For the first time among any Ediacara taxon, we found that this sample population of Parvancorina demonstrated a strong bimodal orientation, suggesting that orientation played an important behavioral role in its autecology. The aggregated spatial distribution and bimodal orientation of Parvancorina likely resulted from behavioral responses to the influence of benthic currents, suggesting that Parvancorina had a complex sensory network, and was capable of motility.
... The fossils are deep, bilaterally symmetrical negative hyporelief impressions, with good definition and preservation. Features including the characteristic shield and anchor-shape are clearly identifiable despite their size (see Glaessner, 1979). A solitary Tribrachidium heraldicum ( Fig. 3I) was identified from a deep negative hyporelief impression and again is a relatively small individual at 9 mm in diameter. ...
Ediacara fossil surfaces from the Flinders Ranges (South Australia) commonly record excellent preservation quality and can provide a palaeoecological window into some of the oldest communities on Earth (ca. 555 Ma). An excavated semi-contiguous sandstone bed of 6.5 m² from a fossil locality at Crisp Gorge in the central Flinders Ranges records an abundance of taxa and structures characteristic of White Sea assemblage communities. Stratigraphic analysis places the fossil surface within the Oscillation Rippled Sandstone Facies of the Ediacara Member at Crisp Gorge. The community appears to be predominantly juvenile forms, with Dickinsonia costata, Parvancorina minchami and Tribrachidium heraldicum present only within interpreted juvenile size ranges. The textured organic surface contains structures including low relief ridges and round bosses, but overall records a smooth bed surface and is interpreted as representing a surface with only an immature microbial mat developed before burial. No effaced or decayed organisms were identified. Community analysis describes an intermediate Shannon diversity (1.27) and an uneven community dominated by the population of D. costata, which comprises more than 50% of the individuals. The examined parameters, when combined with the presence of small, juvenile taxa and an immature organic mat, suggests that the community inhabiting this surface prior to its catastrophic burial may have been comparable to a modern early-stage, primary successional community. The Crisp Gorge bed emphasizes that Ediacara fossil surfaces from South Australia span a range of developmental stages and offer a window into Ediacaran sea-floor communities at various stages of maturity.
... Suas bordas s?o consistentes e h? uma eleva??o longitudinal na por??o mediana (Zucatti da Rosa, 2005). Suas afinidades ainda n?o s?o muito com- preendidas, mas existe a possibilidade de que esse organis- mo estaria relacionado aos artr?podes (Glaessner, 1980). Parvancorina ? ...
The Ediacaran Period marks the first appearance of complex macroscopic organisms in the fossil record. Current evidence
indicates that Ediacara biota is composed of animals, groups of extinct giant protists, algae and other organisms without
proven affinities with modern groups. Fossils of this biota have been documented in at least 40 locations worldwide. In
South America, ediacaran metazoan fossils are found in Brazil, Paraguay, Uruguay and Argentina. In most of these locations, are found fossils of the last moment of evolutionary ediacaran biota, capable of performing skeletogenesis, such as Cloudina and
Corumbella , related to Nama assemblage. This evolutionary novelty arose probably in response to predation pressures and chemical changes in the oceans. Newly, fossils of soft-bodied organisms were found, typical of other ediacaran assembly (White Sea), in Santa Catarina (Brazil). This occurrence is of great importance since it represents the only discovery about its assemblage in South America. This work aims to compile the occurrences of the Ediacara biota in South America, as well as discussing the importance of inclusion and study these events on the world scene in the scope of one of the most important issues of Paleobiology: the origin and evolution animals on Earth.
Until recently, paleontological data were almost completely ignored by zoologists studying the origin of major groups of invertebrates and the early phylogeny of the Metazoa, chiefly because Charles Lyell had long ago emphasized the incompleteness of the geological and paleontological record. Charles Darwin adopted the same view and discussed the absence of ancestors of the Cambrian fauna. Only in the last few decades has paleontological information become available that bears on this problem, yet it, too, has been ignored in favor of new methods in the studies of living systems, in particular, from such fields as histology, genetics, biochemistry, and molecular biology. Along with the classical approaches, i.e., comparative anatomy and embryology, neontology dominated the study, not only of the systematics of Recent organisms, but also of the origin and phylogeny of Metazoa.
Reference to fossil imprints of soft-bodied Ediacaran metazoans made by Hill and Bonney (1877, p. 757) recorded two of “those curious arrangements of concentric rings which have been supposed to be organisms” present on one of the bedding faces of the North Quarry, Woodhouse Eaves in Charnwood, Forest, Leicestershire, England (see Ford, 1958, 1963); the markings were dismissed as being “accidental ... (and) inorganic.” Early this century, P. Range and H. Schneiderhöhn collected fossil remains of equivalent age at Kuibis Farm in South West Africa (Namibia), and the organic nature of this material was confirmed by Gürich (1929, 1933). The history of discovery of such fossils during the mid part of the century (Sprigg, 1947, 1949; Ford, 1958, 1963, 1968, 1979a,b, 1981; Anderson and Misra, 1968) and the subsequent finding of similar materials widely sited about the globe are well known (e.g., Glaessner, 1984; Hofmann, 1987).
Up to the 1950s, the Precambrian was regarded as unrewardingly unfossiliferous, records of fossils being isolated, few in number and dubious. The change came with the discovery by Reg Sprigg of body fossils in latest Proterozoic sediments in South Australia. Although there had been descriptions of isolated fossils (now recognised as Ediacaran) from rocks of this age in the nineteenth century and at the start of the twentieth century, in Newfoundland and Namibia, respectively, the Ediacara finds stimulated researches and now, at the start of the twenty-first century, diversified fossil assemblages are known, all over the world, from the period 600–543 Ma, known formerly as the Vendian and now officially as the Ediacaran. In this account, a brief description of the history of these finds is given, followed by descriptions of the most important provinces [South Australia, Leicestershire, Namibia, Russia (Podolia, the White Sea Coast, Urals and Siberia), Newfoundland (Avalon Peninsula) and Northwest Canada]: then of 27 other known occurrences of this dominantly soft-bodied and perplexing fauna(?)–it seems certain that some, at least of the fossils, are animal fossils, although some, even the greater part, could be a unique form of life, not animals or plants (“Vendobionta”). These descriptions, derived in the course of a literature search lasting over a year, are followed by discussions of important special aspects: trace fossils; geochronology and correlation; geotectonics; glaciation (the “Snowball Earth” concept applied to the Varangian/Laplandian/Marinoan glaciation, which ushered in this last subdivision of the Proterozoic); the evidence for Ediacaran and other life forms existing in the Proterozoic prior to its last, Ediacaran, chronological subdivison; the Vendozoa concept. The last section consists of short summary of conclusions. This text essentially constitutes an objective record of what has been published to 2005 on the Ediacaran System.
Morphological and quantitative characteristics of the growth variability of two Parvancorina species were analyzed based on new abundant material from the Vendian of the White Sea. Growth variability in this problematic
taxon appears to be wider than previously suggested. We found allometric growth in the White Sea population of P. minchami Glaessner, 1958, in contrast to isometric growth in Australian representatives of the species. Another White Sea species,
P. sagitta Ivantsov, 2004, shows gradual formation of anchor-shaped structure in juveniles. Based on Australian material, it was previously
believed that this structure did not change during ontogeny. These two distinctive features together with a strong variability
of age-related measurements distinguish Parvancorina from other early arthropods (Scania, Primicaris), and cast doubt on the growth pattern as an argument in favor of the arthropodan nature of Parvancorina.
Constraining the origin of animal groups is allowed, to some extent, by discoveries of Cambrian Lagerstätten that preserve both mineralizing and nonmineralizing organisms. A new species is reported here of the Cambrian arthropod Skania, which bears an exoskeleton that shares homologies with the Neoproterozoic (Ediacaran) organism Parvancorina and firmly establishes a Precambrian root for arthropods. A new monophyletic group, Parvancorinomorpha, is proposed as the first clade within the arthropod crown group demonstrably ranging across the Neoproterozoic–Paleozoic transition. The Parvancorinomorpha is interpreted to be the sister group of the Arachnomorpha. Incipient cephalization in Skania and related genera represents a step in the progression toward division of a cephalon from a large posterior trunk as shown in Cambrian arachnomorphs such as naraoiids and the addition of a pygidium and thoracic tergites as shown in the arachnomorph clade basal to trilobites. This evidence can serve as a new calibration point for estimating the divergence time for the last common ancestor of arthropods and priapulids based on molecular clock methods.
Inaria karli gen. et sp. nov., a moderate sized lobate fossil from the Late Precambrian Ediacara assemblage, occurs in a number of modes of preservation involving composite moulding of a compressed, thin-walled bulbous organism. Numerous specimens occur on the soles of sandstones interbedded with relatively thick claystones within the Ediacara Member of the Rawnsley Quartzite (Pound Subgroup) in the central Flinders Ranges. Reconstruction suggests a sack-shaped anemone with an erect pharynx. It occupied a benthic position on the shelf below fair weather wave base. Comparisons with Ediacaran and Early Cambrian trace fossil and body fossil impressions with radial symmetry suggest that Inaria was a non burrowing precursor to actinian infauna.
The new bilateral metazoan Andiva ivantsovi gen. et sp. n. is described here from the siliciclastic deposits of the Ust'‐Pinega Formation (Upper Redkino Stage, Vendian) exposed in the sea cliffs of the Winter Coast, White Sea, Russia. The bipolarity of its shield‐like imprints, modes of deformation, growth pattern and the regeneration marks, though rare, indicate that the fossil represents a convex dorsal carapace of a triploblastic invertebrate whose anatomy is yet to be discovered. The thin and flexible carapace was composed of an organic, non‐mineralised, and slowly degradable substance. Fossil Andiva exhibits much in common in the overall body plan, fine structure, and mode of preservation with the well‐known Ediacara taxa Ovatoscutum and Chondroplon that were interpreted as the bilateral pneumatophores of the oldest Chondroplidae (Hydrozoa, Coelenterata). In the light of the new morphological and taphonomic data related to Andiva, the nature of Ovatoscutum, Chondroplon, and probably Dickinsonia, has to be reconsidered.
The Ediacara fossil assemblage occurs widely in the Flinders Ranges, South Australia, in a single, readily mappable stratigraphic interval—the Ediacara Member of the Rawnsley Quartzite, which is part of the Pound Subgroup of the Wilpena Group. The Member occurs low in the Rawnsley Quartzite and consists of siltstones, medium‐ to thick‐bedded sandstones, and heterolithic units of intercalated siltstone and sandstone. Features such as rhythmical bedding and flaser bedding, interference and flat‐topped ripples, winnowed coarse sand residues, abundant clay galls, and rare desiccation cracks suggest that the heterolithic siltstone/sandstone units represent intertidal deposits. The rich body‐fossil assemblage occurs chiefly in these deposits of probable intertidal origin, and for the most part appears to represent organisms stranded by the tide away from their normal habitat. Associated bioturbation structures include horizontal, penetrative (post‐depositional) burrows, but vertical dwelling burrows have not been found; the Pound Subgroup evidently pre‐dates their widespread appearance.
A re-examination of Aysheaia pedunculata Walcott, 1911 and Skania fragilis Walcott, 1931, based partly on hitherto unpublished materials as well, shows the first to be morphologically intermediate between the Onycophora and the Tardigrada as it has some features which are typical of either Phyla; S. fragilis appears to be comparable only to Parvancorina minchami Glaessner, 1958 from the Upper pre-Cambrian of Australia.
ZweiApus-ähnliche Branchiopoden aus dem unterdevonischen Hunsrückschiefer, eine breite und eine schlanke Form, werden beschrieben
und abgebildet. Beide besitzen aber kein Postabdomen mit Furca wieApus und sind deshalb unter den Notostraca oder einer anderen Gruppe der Branchiopoden nicht unterzubringen. Es wird vorgeschlagen,
sie in eine neue Ordnung Acercostraca (άϰεϱϰoζ=schwanzlos) einzuordnen.
- M F Glaessnee
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-(1962): Precambrian fossils. -Biol. Rev., 37: 467-494.
-(1979) : Precambrian. -In: Treatise on Invertebrate Paleontology (R. A. ROBISON
and C. TEICHEET, eds.), Pt. A: A79 -A118.
Novye nakhodki okamenelostey v valdayskoy serii dokembriya po r
- B M M A Keller
- Fedonkin
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serii dokembriya po r. Syuzme. -Izv. Akad. Nauk SSSR, Ser. Geol., (1976)
No. 3: 38 -44 (in Russian).
- P Tasch
TASCH, P. (1969): Branchiopoda. -In: Treatise on Invertebrate Paleontology
(R. C. MOORE, ed.) Part R, (Arthropoda 4/1), R128-191.