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Precambrian Research 269 (2015) 139–146

Contents lists available at ScienceDirect

Precambrian Research

jo ur nal homep ag e: www.elsev ier .com/ locate /precamres

aphonomy of the Ediacaran Podolimirus and associatedipleurozoans from the Vendian of Ukraine

erzy Dzika,c,∗, Andrej Martyshynb

Instytut Paleobiologii PAN, Twarda 51/55, 00-818 Warszawa, PolandTOV Geomarket Impeks, ul. Urlovska 8/53, Kyiv, UkraineZakład Paleobiologii i Ewolucji, Wydział Biologii, Centrum BiolChem, Uniwersytet Warszawski, Zwirki i Wigury 101, 02-096 Warszawa, Poland

r t i c l e i n f o

rticle history:eceived 25 February 2015eceived in revised form 2 July 2015ccepted 3 August 2015vailable online 20 August 2015

eywords:ate Precambriandiacarianilaterians

a b s t r a c t

Fossiliferous strata of the late Ediacaran Lomoziv Member of the Mohyliv Formation, once known fromnow flooded outcrops along the Dniester River, have been recently exposed in a large quarry near theNovodnistrovs’k electric plant dam in Podolia, Ukraine. Finely bedded arkosic sandstone with clay-stone/siltstone intercalations is locally rich in ‘elephant skin’ surfaces indicating original presence ofmicrobial 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 stronglycompacted, with low relief. Specimens of bilaterally symmetrical latest Precambrian animals newly col-lected at the quarry offer additional evidence that their bodies had a complex internal anatomy. Thisrelates especially to Podolimirus mirus, previously known from only fragmentary specimens representing

volutionnatomy

only marginal parts of its chambered organ (‘quilt’). It appears that there is a large region of the bodyin front of the ‘quilt’, with a lobate organ resembling bifurcating anterior structures earlier thought torepresent 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 thatreported in the dickinsoniids from northern Russia and Australia.

© 2015 Elsevier B.V. All rights reserved.

. Introduction

A diverse assemblage of Ediacaran fossils, including those ofrobable bilateral animals Podolimirus and Dickinsonia, was recov-red from the Lomoziv Member of the Mohyliv Formation duringonstruction of the Novodnistrovs’k dam on the Dniester Rivern 1979 (Velikanov, 1985; Fedonkin, 1985; Fedonkin and Vickers-ich, 2007). Eventually, most of the exposures of the fossiliferoustrata were flooded. An opportunity to add to the evidence inand has emerged with return to construction works in the lastears. A large quarry is now operating near the dam (27◦27′46.4′′ E;

8◦35′06.3′ N), where the entire Mohyliv Formation is exposednd available to study. A collection of about two thousand speci-ens of Ediacarans have been collected by the junior author, among

Abbreviations: KSU, Department of General and Historical Geology, Tarashevchenko National University of Kyiv, Ukraine; PIN, Paleontological Institute ofhe Russian Academy of Sciences in Moscow, Russia; SAM, South Australian Museumn Adelaide, Australia.∗ Corresponding author at: Instytut Paleobiologii PAN, Twarda 51/55, 00-818arszawa, Poland. Tel.: +48 226978738; fax: +48 22 620 6225.

E-mail address: dzik@twarda.pan.pl (J. Dzik).

ttp://dx.doi.org/10.1016/j.precamres.2015.08.015301-9268/© 2015 Elsevier B.V. All rights reserved.

them new specimens of the controversial Podolimirus and otherprobable dipleurozoans (sensu Dzik and Ivantsov, 1999) with upto now poorly understood anatomy and relationships (Martyshyn,2012). The Podolian material is of interest because it has a differ-ent composition from the classic Australian and northern Russianfossil assemblages and its mode of fossilization. It is different fromthe assemblages from the White Sea, but more similar to that inAustralia, but yet unlike the latter, the rock enclosing has not beeninfluenced by weathering in desert conditions. The Podolian fos-sils may assist in better understanding those taphonomic processesthat enabled preservation of soft-bodied imprints left in coarsesands.

2. Geological setting

Two members of the Mohyliv (Mogilev in Russian literature)Formation are exposed in the Novodnistrovs’k Quarry (Martyshyn,2012). The basal-most Lomoziv (Lomozov) Member was deposited

directly on an eroded crystalline rock base — with granitic boul-ders in the basal member. It represents the second sedimentarycycle in the Vendian of Podolia (Korenchuk and Ishchenko, 1981).Conglomerate beds vary in thickness, with a maximum of 1 m,

140 J. Dzik, A. Martyshyn / Precambrian Research 269 (2015) 139–146

Fig. 1. Fossiliferous Late Vendian strata exposed in the Novodnistrovs’k Quarry, Podolia, Ukraine. (A) Stratigraphic sequence of the lower Lomoziv Member, Mohyliv Formationn tion exw c plan

wlTssobo

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oting position of microbial mats containing fossil Ediacarans. (B) View of the secall of the quarry. (D) Location of the quarry relative to the Novodnistrovs’k electri

ith intercalations of sandy siltstone and thin arkosic sandstoneenses (Velikhanov et al., 1983; Korenchuk and Velikanov, 1987).he Yampil (Yampol) Member consists mostly of thick-beddedandstones up to 9 m thick, grading upwards into a thin-beddedandstone, up to 3 m in thickness. The Lyadova (Lyadov) Memberf the overlying Yaryshiv (Yaryshev) Formation with a siltstonease (up to 2 m) and up to 14 m of claystone with thin siltstoner sandstone intercalations in its upper part (Fig. 1).

Ediacaran fossils are most common in the upper part of theampil Member, where molds of more or less compacted bodies ofeltanelliformis (usually referred to as Nemiana) occur on the solef the sandstone slabs. These may originally have been sphericalicrobial (cyanobacterial?) colonies (Ivantsov et al., 2014), bowl-

ng and bouncing over the sea bottom until they were imbeddedn suddenly deposited mud. Subsequently deposited sand infilledhe space after organic bodies decayed. Compacted lenticular sand-tone bodies may be found within the siltstone without any sign ofeing infilled from above, which means that occasionally sand was

ncorporated by the colonies already during their life.Lenticular imprints of either cyanobacterial colonies or petalon-

mean ‘sea pens’ holdfasts occur also in the siltstone beds of theomoziv Member. In the horizon about 70 cm below the main con-lomerate bed in the southern wall of the quarry these organicemains are associated with imprints of dipleurozoan bodies,ncluding Podolimirus and Dickinsonia.

Based on micropaleontological evidence, the Mohyliv Formationf Podolia is significantly older than the Erga (formerly Mezen) For-ation on the White Sea shore (Burzin, 1998). Grazhdankin (2014,

igs. 5 and 6) dated the lower Erga Formation at 550.2 ± 4.6 Ma,

posed in the south-western corner of the quarry. (C) General view of the easternt dam. (E) Map of Ukraine with location of the studied sites indicated.

a date reported by Iglesia Llanos et al. (2005) for strata exposedat the Zolotica River in the same region. In an earlier publicationthe age for the underlying Zimnie Gory Formation, also fossilifer-ous, was 555.3 ± 0.3 Ma (Martin et al., 2000). Compston et al. (1995)dated zircons from tuffs at the top of the Sławatycze Formation inthe Polish part of the Podolian Basin at 551 ± 4 Ma, and the Rb–Srisochron age of basalts from Ukraine is 552 ± 53 Ma (Nosova et al.,2008). The boundary between Sławatycze and Białopole formationsis correlated with the boundary of Yaryshiv and Nahoryany forma-tions in Podolia (Moczydłowska, 1991). Grazhdankin et al. (2011)and Grazhdankin (2014) gave 553 Ma for the base of the YarishivFormation.

3. Taphonomy

Preservation of the dipleurozoan Ediacarans in the LomozivMember significantly differs from that in the most spectacularof known Ediacaran localities at Zimnie Gory on the White Seacoast. There are two main fossiliferous horizons within the ErgaFormation exposed in the cliff. The upper one is a 10 cm thicksandstone bed that extends for at least 200 m laterally withoutany significant change in thickness. The fossil assemblage in thishorizon is dominated by large specimens of Yorgia (Ivantsov, 1999;Dzik and Ivantsov, 1999). A much more diverse fossil assemblagehas been recovered from the soles of sandstone lenses about

3 m below. The lenses of a fine-grained quartz sandstone with aclay matrix apparently developed as a result of synsedimentarydeformation of a sand load of varying thickness that was depositedon a clay bed. The stretch marks, which frequently affect fossils

J. Dzik, A. Martyshyn / Precambrian R

Fig. 2. Thin sections of sandstone slabs with ‘elephant skin’ lower surface typical ofthe Ediacarian microbial mats. (A) Erga Formation, Zimnie Gory Kimberella localityon the White Sea shore, Russia, microbial mat ruptured at the margin of “stretchmark” and fluidized pure sand filling the rupture (modified after Dzik, 2003, Fig.3A). (B) Lomoziv Member of the Mohyliv Formation, level with Hiemalora in theNc

cisbtiemitstDGeposo

M

ovodnistrovs’k Quarry, irregularly laminated muddy, arkosic sandstone prone toompaction with numerous microbial mats preserved.

learly demonstrate that both the sand above and clay below thenterface were semiliquid long after formation of the Ediacarans’ole casts and external molds. The same conclusion was reached,ased on microfault studies, by Gehling (1999, p. 48) in respecto the Australian Ediacaran fossils. Especially informative are sandnjections, which penetrated ruptures in the microbial mats. Theyxpanded below the mat, replacing the hydrated clay, but the matargin remained intact, locked between the sand layer above and

ts injection below (Fig. 2A). Pyrite-cemented sand grains alonghe bed sole formed the Gehling’s (1999) ‘death mask’, whichtabilized the sand replicas of the microbial mat beneath and ofhe dorsal surfaces of bodies lying on it (Steiner and Reitner, 2001;zik, 2003). The Erga Formation fossiliferous sandstone at Zimnieory is relatively poor in clay minerals, and its compaction is low,nabling preservation of nearly unaltered original tridimensionalroportions of fossilized organisms. This recorded various stagesf decay and collapse of internal organs under the load of hydrated

and (Dzik, 2003, 2011), offering a powerful tool in restoring theriginal anatomy of Precambrian animals.

The mechanical properties of the arkosic sands of the Lomozivember of the Mohyliv Formation were different. There is a

esearch 269 (2015) 139–146 141

significant clay mineral content in the sandstone, as well aspresence of angular quartz sand grains in the shale intercalations.The ‘elephant skin’ surfaces, indicating the original presence ofmicrobial mats, are irregularly distributed, and compaction of thefossiliferous strata is strong (Fig. 2B). As a result, the fossils arepreserved in low relief and mostly as replicas of imprints left bycollapsed animal bodies on the microbial mat. It is more difficultto distinguish imprints of dorsally located organs from thoseoriginally located below than in case of the White Sea material.

3.1. Preservation of the dipleurozoan dorsal ‘quilt’

Among newly collected specimens of Ediacarans from theLomoziv Member of Mohyliv Formation of great value is the almostcomplete specimen KSU No 17p174 (Fig. 3). It is preserved on thelower sole surface of a laminated sandstone slab. The slab splits intolayers of millimeter thickness. The strata below were even moreregularly and finely laminated as shown by remnants of two suchlaminae left in places (Fig. 3B). They are of uniform thickness in allplaces in which they can be recognized, of less than 0.5 mm thick-ness. This suggests that the microbial mat similar to that knownfrom the White Sea (Fig. 2A), on which the body was deposited,persisted for relatively long time (perhaps seasons). Although thebody was somewhat deformed and laterally bent before fossiliza-tion, it exposes a set of structures previously unknown in any of theUkrainian Ediacarans. The presumably anterior part of the body isof trapezoidal outline, with roughly parallel, tongue-like depres-sions in the sandstone slab sole, which means that it was anteriorlyfilled with a material more resistant to compaction than the regionbehind. The posterior margin of the trapezoidal anterior part formsa transverse elevation with distinct margin. This means that eitherit was easily compressed under the sand load or the sand fromabove penetrated its interior. Behind there is an area covered bycollapsed chambers of the dorsal ‘quilt’. It is widely accepted thatsuch organs in the Vendian animals were originally filled with liq-uid under pressure. This is inferred from specimens interpreted asrepresenting different stages of collapse. They range from thosewith dorsal and ventral walls superimposed in a way suggestingpresence of vertical wall between segments to those with convexdorsal surfaces of segments as if being under pressure from inside(Seilacher, 1989).

The quilt of KSU No 17p174 specimen is composed of two setsof strongly arched units, 13 (perhaps 14) in number, with size anddepth of the arching gradually decreasing toward the posteriorend. The central zone of each of the ‘quilt’ chambers is depressed,and margins are marked by sharp elevations. In places there aretwo elevations separating chambers from each other; these maybe interpreted as marks left by vertical, between-chambers walls,pressed down and bent during the structure collapse. It is unclearwhether the chambers continue across the midline or, like in mostdipleurozoans (Dzik, 2003), they were separated by a medial wall.There are oval impressions close to the midline that may representlaterally bent vertical walls of this kind, but they are hard to distin-guish from impressions of oval microbial mat flakes, which occurin the anterior part of the ‘quilt’ on its left half (Fig. 3).

Several other specimens of serially distributed relatively largechambers of the dorsal ‘quilt’ have been found in the Lomoziv Mem-ber beds. The most similar to the specimen KSU No 17p174 is theholotype specimen PIN 3994/417 of Podolimirus mirus Fedonkin inVelikhanov et al. (1983) collected in 1979 on the right bank of theDnester River north of the Novodnistrovs’k Dam. The specimenexhibits two series of ‘segments’ separated by an empty area in

between them, and already Fedonkin (1985) suggested that theyare displaced from their original disposition. This would mean thatonly marginal parts of the arched units are represented there. TheFedonkin’s specimen is an individual of somewhat larger size than

142 J. Dzik, A. Martyshyn / Precambrian Research 269 (2015) 139–146

Fig. 3. Podolimirus mirus Fedonkin, 1983, specimen KSU No 17p174 from the lower Lomoziv Member of the Mohyliv Formation at the Novodnistrovs’k Quarry. (A) Photographtaken under low angle light from NE. (B) Explanatory drawing traced from photographs with variously oriented light (in the drawing light is from ‘South’); chambers of thedorsal ‘quilt’ numbered.

Fig. 4. Restoration of Podolimirus mirus Fedonkin, 1983 anatomy in cross section and from ventral side with hypothetical body covers and intestine removed (B) and itscomparison with available fossils from the Lomoziv Member of the Mohyliv Formation (A, C–F). (A) Nearly complete specimen KSU No 17p174 from the Novodnistrovs’kQuarry (Fig. 2). (C) Holotype PIN 3994/417 from the right Dnester bank North of the dam representing displaced marginal parts of the ‘quilt’, drawing based on new photographstaken under low angle light (illustrated also in Fedonkin, 1985, p. 10, Fig. 4). (D) Specimen PIN 3994/404 illustrated by Fedonkin in Velikhanov et al. (1983, p. 30, Fig. 3) as‘fragment of a feather-like form of unclear systematic position’. E. Specimen KSU No 17p175 from the Novodnistrovs’k Quarry. F. Holotype of Valdainia plumosa Fedonkin1983 PIN 3994/276 from north of the dam; based on new photographs.

brian Research 269 (2015) 139–146 143

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Fig. 5. Ventral view of sandstone slab PIN 3993/5018 with Yorgia waggoneri Ivantsov(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 after Dzik and Ivantsov, 2002, Fig. 3A).

J. Dzik, A. Martyshyn / Precam

he newly collected KSU No 17p174, but the mode of preservations closely similar. The tips of some of the chambers are more visiblen the holotype — terminating parabolically, rounded at their tips.

Another newly collected specimen KSU No 17p175 (Fig. 4E)ossesses chambers complexly displaced, but the margin of theody preserves a series of posteriorly-directed terminations ofhambers. This suggests that specimen PIN 3994/276, which wassed to introduce Valdainia plumosa Fedonkin in Velikhanov et al.1983), associated with the P. mirus holotype, represents the samepecies, the latter name being chosen as the valid one (Fig. 4F).he rock matrix, in which V. plumosa is preserved, is a sandstoneith relatively little compaction and the specimen is preservedore tridimensionally, with vertical walls between chambers pen-

trating the sandstone matrix. Fedonkin (1985) noticed presencef ‘intersegmental’ elevations separated by furrows. If they repre-ent vertical walls of the chambers, each unit had its own (perhapsollagenous, as suggested by its elasticity in other dipleurozoans)nvelope that could partially separate from its neighbor. Alterna-ive, but less likely, interpretation of the ‘intersegmental’ units ishat they are homologous to probable gonads of Yorgia, attachedo vertical walls of the ‘quilt’ chambers. Yet another candidateor representing a deformed Podolimirus ‘quilt’ is the ‘fragment of

feather-like form of unclear systematic position’ PIN 3994/404llustrated by Fedonkin in Velikhanov et al. (1983, p. 30, Fig. 3).lthough it lacks indication of its origin, it is likely to come from

he same strata.Since Runnegar (1982), it has been generally accepted that the

uilt of the dickinsoniid dipleurozoans was contractile and easilyhanged its shape while being enveloped by the sediment. Thispplies as well to the White Sea Yorgia (Ivantsov, 1999; Dzik &vantsov, 1999) and probably also to Podolimirus, if it is truly aipleurozoan.

The medial sinus in the quilt visible in specimen KSU No 17p174as no correspondence to the external outline of the body. One mayuess that it is an expression of a medial furrow, with its depthncreasing anteriorward, that held an internal organ. Such a tubulartructure is located in this region in some dickinsoniids, interpretedy some as intestine, based on its anatomical location and an infillore resistant to compaction than the remaining body (Dzik and

vantsov, 2002).Podolimirus, as restored on the basis of new specimen, is similar

o Yorgia not only in its size and arched disposition of dorsal cham-ers, but also in the presence of probably bifurcating structures inront of the ‘quilt’. In Yorgia these structures have been interpreteds intestinal diverticula by analogy with modern animals (caeca;zik and Ivantsov, 1999), and such interpretation is offered herelso for Podolimirus (Fig. 4B). Whatever the nature of the anteriorlyocated organs in Yorgia and Podolimirus, this region of the body hadifferent morphology from the section occupied by the ‘quilt’. This

s indicated by how it has been preserved, evidenced by a tendencyo allow sand to penetrate the body interior.

.2. Sediment injections into the body

A transversely running elevation separates the frontal part of theody of Podolimirus specimen KSU No 17p174 and grades anteriorly

nto a depression with a lobate appearance, but posteriorly its slopes steep over most of its extent. Taking into account strong com-action of the imprint, it is a situation similar to that observed in annigmatic specimen of Yorgia (Fig. 5; Dzik and Ivantsov, 1999). Onenterpretation of this structure is that liquidized sand either pressedn the anterior of the body squeezing its content and pushing it

ackward, or it filled the interior of the body, gradually replacing itsuids. In the Yorgia specimen PIN 3993/5018 (Fig. 5) vertical septaenetrate deeply the sand fill from below suggesting that the sec-nd interpretation is closer to truth. It is not clear, however, if these

were vertical walls separating chambers of the dorsal quilt or theventral portion of the body was also septate. Specimen SAM P 14387of Dickinsonia from Ediacara (Fig. 6C), in which the sand injectionis three-dimensionally preserved, shows no septa on the ventralsurface. Either Yorgia differed from Dickinsonia in its anatomy, orinjections penetrated the body on different levels in each of thesespecimens. Whatever is the correct explanation, it appears that theanterior end of the body was prone to decomposition and that sandwas more likely to penetrate the body interior from there than fromother sides of the dipleurozoan body.

Some inconsistency to the idea of specificity of the anteriorregion of the body is introduced by specimen PIN 3994/564 of Dick-insonia costata from Podolia illustrated by Fedonkin (in Velikhanovet al., 1983, p. 31, Fig. 3). There is no indication where it was col-lected on the label but Yaryshiv Formation is noted in Fedonkin andVickers-Rich (2007). This seems unlikely, as Table 5 in Velikhanovet al. (1983) lists Dickinsonia only in the Lomoziv beds, and nosuch fossils have ever been found later in the Yaryshiv Formation(Martyshyn, 2012). In this specimen (Fig. 6A), the termination of thebody, which seems to be destroyed by sand injection, is the poste-rior one. However, the rather coarse-grained nature of the sedimentmakes interpretation of this specimen difficult, not preserving fine

detail, and it is uncertain whether the sand truly entered the inte-rior of the body or just deformed it.

144 J. Dzik, A. Martyshyn / Precambrian Research 269 (2015) 139–146

Fig. 6. Internal anatomy of Dickinsonia. (A) Specimen PIN 3994/564 of Dickinsonia costata with posterior end filled with sand from north of the dam at Novodnistrovs’k(illustrated also by Fedonkin in Velikhanov et al., 1983, p. 31, Fig. 3) probably the Lomoziv beds. (B) D. costata specimen KSU No 17p177 with probable fill of intestinaldiverticula recently found in the Lomoziv Member of Mohyliv Formation at the Novodnistrovs’k Quarry. (C). Dickinsonia sp. specimen SAM P 14387 from the Pound Quartziteat Ediacara in the Flinders Range, Australia (illustrated also in Dzik, 2003, Fig. 7C), with injection of sand in the anterior part of the body. (D) D. costata specimen SAM T6 d WaD

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1-2051 from Ediacara with infill of intestinal caeca (illustrated also in Glaessner anzik, 2003).

.3. Preservation of internal organs ventral to the quilt

The newly found specimen KSU No 17p177 from the Lomozivember of Mohyliv Formation (Fig. 6B) presents difficulty in inter-

retation. It has a nearly flat surface with poorly recognizableubunits of the quilt but has tubular sand-filled structures extend-ng from the axial region of the body. These tubular structuresre not parallel to one another in some places or to chambers ofhe ‘quilt’. In this respect they resemble the classic ‘caeca’ in thepecimen from Ediacara illustrated already by Glaessner and Wade1966, p. 101, Fig. 4) and much better preserved in the specimenf Long (1995, p. 15; Dzik, 2000). Connection of these structuresith the original body anatomy is not widely accepted because

his contradicts the idea that the ‘quilt’ represents the whole bodyf the dipleurozoan Ediacarans. That the body of Dickinsonia wasomposed not only of the dorsal ‘quilt’ but also other internal struc-ures is shown by several other specimens from Ediacara, amonghem SAM P 14387, of exquisite, as for Ediacara, three-dimensionalreservation (Fig. 6C). The quilt in that specimen is only slightlyompressed by the sand load from above, enveloping a central tubu-ar organ resistant to compaction. This is interpreted to mean that it

as filled with something other than the surrounding soft tissue. Bynalogy with fossils of various Palaeozoic bilaterian animals, intes-ine with its fill seems a reasonable guess of its nature. Notably,here are also rows of resistant structures parallel to the long axisf the body on both sides. Their location is thus similar to tubular

tructures in Yorgia (Dzik and Ivantsov, 1999) and oval structuresn ‘Dickinsonia’ tenuis from Zimnie Gory (Dzik and Ivantsov, 2002).n the latter, not only axial tubular structure is resistant to com-action and frequently preserved, but also lateral ‘diverticulae’

de, 1966, p. 101:4). (E) Restoration of internal anatomy of D. costata (modified after

serially extending from it (interpreted in terms of ctenophore bodyplan by Xhang and Reitner, 2006; see also Dzik, 2002). These ‘diver-ticulae’ bifurcate anteriorly (Fig. 3), providing a ‘connecting link’between Dickinsonia and Yorgia in their construction.

Among new fossils from the Lomoziv Member of MohylivFormation one (KSU No 17p179; Fig. 7) exhibits serially arrangedorgans along the midline, which have collapsed and appear to havebeen filled with sand from above in a manner similar to specimensfrom the White Sea ‘Dickinsonia’ tenuis. The only other publishedfossil that resembles the new Lomoziv material is ‘Spriggina’borealis Fedonkin in Paliy et al. (1979) from the Erga Formation ofthe White Sea (Fedonkin, 1985, p. 21, Fig. 5). Its poor preservationprevents any closer comparison. The Podolian material representstwo individuals preserved in close proximity. Both have a roundeddiamond shape with a thickened, smooth fringe around theiredges. Possibly, the animal wore a kind of a dorsal shield. In thisrespect it resembles Vendia. The original specimen of this enigmaticEdiacaran was preserved as a concave mold of the body on thesandstone bed sole (Keller, 1969). A series of oblique convexitiesdeveloped on both sides, merging alternately in the midline. Theseconvexities resemble impressions of tubular bodies preservedbetween chambers in Yorgia. Perhaps the lack of such convexitiesin specimens classified in Paravendia (Ivantsov, 2001) correspondsto variable preservation of structures proposed to representsgonads in Yorgia, based on their serial distribution and changingmode of preservation depending on ontogenetic stage. They were

resistant in large, presumably mature, specimens but collapsed insmaller specimens (Dzik and Ivantsov, 1999). Ediacarans with abody outline similar to that of the enigmatic Podolian species, butwith serially arranged oval bodies near the midline may not be as

J. Dzik, A. Martyshyn / Precambrian R

Fig. 7. Probable relative of Spriggina borealis Fedonkin, 1979, specimen KSU No1P

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7p179 from the Lomoziv Member of Mohyliv Formation at Novodnistrovs’k Quarry,odolia, Ukraine.

istant phylogenetically to it, as the plain morphology of fossilsuggests. Their shields frequently show tuberculation (e.g., Onega;vantsov, 2007) similar to that on the shield of Kimberella (as inter-reted by Dzik, 2011). All this suggests that the whole plexus ofilaterally symmetrical Ediacarans may represent a monophyleticnit of relatively recent (in the Late Vendian) history.

. Conclusions

The newly discovered fossil Ediacarans from the Lomoziv Mem-er of Mohyliv Formation are preserved in a style more typical ofaterial from Australian Ediacaran localities in the Fliders Range

han to that characterizing material from the Erga Formation thatrops out along the White Sea shore in northern Russia. Unlikehe White Sea fossiliferous horizons, thick microbial mats did notevelop in the environments typical of the Ukrainian locality onlay surfaces during prolonged episodes of non-deposition, only toe suddenly covered by sand. In Podolia, sedimentation was moreneven and microbial mats are chaotically distributed within bedsharacterized by arkosic sandstones and siltstones, not so differ-nt in their compactional properties. As a result, the quality ofeproduction of morphological details is lower and preservation isess three-dimensional than that in the northern Russian outcrops.he general mechanisms for preserving imprints on microbial matnd impressions of dorsal body surfaces on soles of overlying beds,emains more or less similar. This enables interpretation of tapho-omic history of particular imprints and hypothetical restorationf the anatomy of the Vendian animals which left such impressions.t was a complex taphonomic scenario and by no means does thequilt’ alone represent the entire organism. Although incomplete,he presentation of anatomical data based on fossils from the newkrainian locality show that some of the Podolian organisms rep-

esent taxa rather distant from those known from other localitiesf the latest Precambrian.

cknowledgements

Participation of the senior author in expedition to the Zimnieory locality on the White Sea shore and travel to Australia

esearch 269 (2015) 139–146 145

was financed with the research grant 6 PO4D 010 13 from thePolish Committee of Scientific Research. The manuscript has beensignificantly improved owing to constructive criticism from twoanonymous referees.

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