Cephalonega, a New Generic Name, and the System of Vendian Proarticulata A

Home , Andiva, Isomer (Proarticulata), Proarticulata, Solza (animal), Vendia, Yorgia

ISSN 0031-0301, Paleontological Journal, 2019, Vol. 53, No. 5, pp. 447–454. © Pleiades Publishing, Ltd., 2019. Russian Text © The Author(s), 2019, published in Paleontologicheskii Zhurnal, 2019, No. 5, pp. 14–21.

Cephalonega, A New Generic Name, and the System of Vendian Proarticulata A. Yu. Ivantsova, *, M. A. Fedonkina, A. L. Nagovitsynb, and M. A. Zakrevskayaa aBorissiak Paleontological Institute, Russian Academy of Sciences, Moscow, 117647 Russia bArkhangelsk Office, Russian Geographical Society, Russian Academy of Sciences, Arkhangelsk, 163001 Russia *e-mail:[email protected] Received December 29, 2017; revised November 9, 2018; accepted February 14, 2019

Abstract—Due to homonymy, a new name Cephalonega Fedonkin, nom. nov. was proposed for the genus of Vendian macroorganisms, Onega Fedonkin. The improved diagnosis of this genus and evidence that this genus belongs to Proarticulata, an extinct phylum of Metazoa, are given. A detailed characterization of the phylum and all Proarticulata classes is given for the first time.

Keywords: Late Vendian, Ediacaran, Proarticulata, Vendiamorpha, Dipleurozoa, Cephalozoa, Onega, Ceph- alonega DOI: 10.1134/S0031030119050046

INTRODUCTION the genus and the description of the species were mod- In 1972 the first large locality of Ediacaran-type ified. In order to substantiate the systematical position fossils in the Upper Vendian natural outcrops in the of the taxon the refined characteristics of Proarticulata north-west of the East European Platform was discov- and subordinated high-rank taxa were formulated. ered on the Onega Peninsula along the banks of the Syuzma River (Keller et al., 1974). At the early stages DISCUSSION of studying the Syuzma locality, several impressions of a small organism were found and this organism was The phylum Proarticulata was distinguished in the described as the monotypical genus Onega Fedonkin, composition of the Vendian fauna on the basis of 1976 (Keller and Fedonkin, 1976). The small sizes, the studying the bilateral–symmetrical animals, which presence of signs of segmentation, and, at this, the exhibit symmetry of gliding reflection. Originally, observed simplicity in the structure allowed one to these animals were grouped into the classes of Vendi- consider this creature as a juvenile form of articulated amorpha and Dipleurozoa (Fedonkin, 1985). In this animals: arthropods (Keller and Fedonkin, 1976; work, we substantiate the creation of the third class of Glaessner, 1979) or annelids (Fedonkin, 1981). Later, proarticulates, Cephalozoa. Over the past years, due to Fedonkin ascribed Onega to protoarticulates belong- systematic excavations and the detailed study of the ing to the phylum of Metazoa, which became extinct representative fossil material (Ivantsov, 2007, 2008, probably in the Precambrian (Fedonkin, 1985). Due 2011), proarticulates obtained the status of the group to the discovery and study of new localities of macro- of Vendian invertebrates of the highest species diver- fossils in the southeastern White Sea Region, includ- sity, while their distribution is limited only by the ing the largest in the world Zimnie Gory locality, the Upper Vendian of Eastern Europe (including the less attention of researchers has been paid to the Urals) and the Ediacaran of South Australia. Dickin- Syuzma finds. Only in the early 21st century, the study sonia Sprigg, 1947, one of the classical Neoproterozoic of new materials obtained during large-scale surveys fossils, described and interpreted in many articles, is a made it possible to refine the morphology of an organ- typical representative of proarticulates. ism and expand the known range of its stratigraphic Proarticulates have a low and wide metameric distribution (Ivantsov, 2007). At the same time, it body, but without lateral or ventral appendages, which turned out that the name Onega was preoccupied by can act as limbs. There are known finds of feeding Onega Distant, 1908, a genus of modern South Amer- traces of proarticulates that allow one to ascribe them ican leafhoppers of the family Cicadellidae (Takiya to metazoans, capable of active movement and nutri- and Cavichioli, 2004). tion (Ivantsov and Malakhovskaya, 2002; Fedonkin, In this work, the new generic name for Syuzma fos- 2002; Gehling et al., 2005; Ivantsov, 2011). One of the sil organism is suggested. In addition, the diagnosis of characteristic features of the structural organization of

447 448 IVANTSOV et al. proarticulates is their “pre-articulation” or “pseudo- ear zone), with which the proximal ends of isomers are metamerism” that means the separation of a body into linked. The occurrence of a narrow longitudinal struc- two rows of “semi-segments” (isomers), shifted rela- ture, which divides the body into two rather indepen- tive to each other on both sides of the sagittal plane dent parts contradicts to the structural pattern of the (Fedonkin, 1985; Ivantsov, 2008). The alternating Phanerozoic articulates. There is no evidence of such arrangement of isomers (symmetry of gliding reflec- a structure on their fossil remains. Thus, the phylum tion) is usually quite clear on fossil remains of proar- Proarticulata can be contrasted to all other single seg- ticulates of all known species, but, sometimes, there mented metazoans. are specimens with the opposite arrangement of iso- It is likely that the segmented structure, which mers. As an example, a juvenile form of Dickinsonia determines a characteristic impression of proarticu- costata is mentioned (Gehling et al., 2005; Evans et al., lates, represents only a part of the body of an organ- 2017; Hoekzema et al., 2017; Dunn et al., 2018). It ism. This thin-walled formation covered inner zones should be noted that the opposite arrangement of iso- of the body from dorsal and ventral sides (Ivantsov mers is characteristic of small specimens with thin iso- et al., 2019) and was made of the matter, denser and mers, but it is not always. Such an arrangement is more resistant to decomposition, than other materials unknown for proarticulates with wide isomers. Never- in the structure of proarticulates (Bobrovskiy et al., theless, some researches consider the very opposite 2019). The formation was covered with a different kind arrangement as a primary one and describe Dickinso- of matter, which formed a shield, sometimes unseg- nia, correspondingly, as normally segmented organ- mented, on the dorsal side of the body. The outer sur- isms (Glaessner and Wade, 1966; Wade, 1972; Jen- face of the shield was covered with tubercles and other kins, 1992; Gehling et al., 2005; Evans et al., 2017; outgrowths. It is assumed that the segmented structure Hoekzema et al., 2017; Dunn et al., 2018). Here, we represented the basal membrane covered with the present images of large and small specimens of one of ectodermal integuments (Ivantsov et al., 2019). Dickinsonia species, which have thin isomers with the distinct alternative arrangement (Plate 3, figs. 2, 3). In According to E. Dzik, in Dipleurozoa (a high-rank our opinion, the clearness and regularity of impres- taxon, which includes several Cephalozoa genera of sions indicate the absence of deformation of the body the proposed system apart from Dickinsonia), a special and, correspondingly, the primary origin of such an metameric organ, consisting of a series of muscle arrangement of isomers. The insignificant postmor- chambers, was located inside the body above the tem longitudinal displacement of one or the other side straight intestinal tract with outgrowths. In the ana- of the body would be enough for the small specimen tomical organization of Dipleurozoa species, Dzik (Plate 3, fig. 3) to have the opposite arrangement of traces homology with nemerteans and some deu- isomers (or vice versa). However, based on this terostomatous organisms (Dzik and Ivantsov, 1999; assumption, it is difficult to explain an absence of con- Dzik and Martyshyn, 2015). However, the dorsal tinuity of ridges marking the boundaries between iso- arrangement of the metameric organ is not confirmed mers, observed on the body axis of the large specimen by the fossil material available. Accordingly, the inter- (Plate 3, fig. 2). Of course, it is hard to prove the pri- pretation of some structures (see the above works) that mary origin of any arrangement by showing more and are weakly expressed on impressions, such as muscular more found specimens. However, the possibility of pharynx or serially arranged gonads seems to be poorly differentiation of the “segments” on impressions into substantiated. two parts strictly along the body axis and the displace- In contrast to such ideas, Fedonkin (2002) inter- ment of these parts relative to each other, no matter preted the metameric structure of Dickinsonia, Ova- what a reason was, indicates the presence of a certain toscutum, and Andiva as a ribbed, thin and flexible dor- longitudinal structure (membrane, cord or other lin- sal cover or shield. Due to this, the problem of the seg-

Explanation of Plate 3 Proarticulates from Upper Vendian deposits of the southeastern White Sea Region; figs. 1–4 natural impressions, figs. 5–9 latex casts; Scale bar: figs. 1–3, 1 cm; figs. 4–8, 0.5 cm; fig. 9, 0.3 cm. Figs. 1–4. Dickinsonia cf. menneri (Keller, 1976): (1) spec. PIN, no. 4716/5148, one of the largest specimens of the species; (2) spec. PIN, no. 4716/5165, a detail, which shows the alternating arrangement of isomers, typical of proarticulates; (3) spec. PIN, no. 4716/5150, an average-sized specimen (a larger size of the head section relative to the width of isomers, long preserved during the ontogenesis, a diagnostic feature of the species); (4) spec. PIN, no. 4716/5146, specimen with intravital damage of the posterior end of the body, which led to the splitting of the zone of formation of new isomers and the subsequent growth in two directions: (4a) a general view, (4b) a detail; Lyamtsa bank, Lyamtsa locality, fossil assemblage L2(XII); Ust-Pinega Formation, Arkhangelsk Beds. Figs. 5–10. Cephalonega stepanovi (Fedonkin, 1976): (5) holotype PIN, no. 3992/5049; (6) spec. PIN, no. 3992/5005 (arrow shows the filamentous outgrowth); (7) spec. PIN, no. 3992/5041; Syuzma River, Syuzma locality, fossil assemblage SZ1(XX); Syuzma Beds; (8) spec. PIN, no. 3993/6795; (9) spec. PIN, no. 3993/6397; Winter Coast of the White Sea, Zimnie Gory locality, fossil assemblage Z11(XXII); Zimnie Gory Beds; (10) spec. PIN, no. 4853/600; Solza River, Solza locality, fossil assemblage SL1(VII); Syuzma Beds.

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Plate 3

1 5

6 4а

7 8 9

PALEONTOLOGICAL JOURNAL Vol. 53 No. 5 2019 450 IVANTSOV et al. mentation of the lower side of proarticulates is still remarkable structure, which is characteristic only of open. However, there are the feeding traces of some the Syuzma proarticulate is represented by the pres- species, including D. costata, which represent, in fact, ence of two thin filamentous outgrowths extending imprints of the ventral side of these organisms. from the posterior end of the segmented area (Ivantsov According to these traces, the upper and lower sides of et al., 2019). Judging by the fact that they occur only in proarticulates were segmented in the same way specimens with clearly visible tubercles and their pres- (Ivantsov, 2011). ence does not affect the size and shape of adjacent iso- The body growth during the ontogenesis of proar- mers, these filaments have an ectodermal origin. ticulates was realized in two ways: an increase in a In this respect, the outbreak of small Cephalonega number of isomers (or their pairs, which some species of approximately the same size should be authors consider as segments) and an increase in noted (Fig. 1). It was most likely due to biological, but their linear dimensions (Runnegar, 1982; Ivantsov, not taphonomical reasons and the granulometric 2004; Hoekzema et al., 2017). It is generally regarded composition of rocks, since in all cases the organisms that the growth zone was located at the pointed end of were buried in situ without subsequent transportation the proarticulate body, where new small isomers were and size grading. In addition, the size of sandstone added (Runnegar, 1982; Sperling and Vinther, 2010; grains, which could affect in theory the ability to dis- Gold et al., 2015; Evans et al., 2017). According to an tinguish fossil impressions, was different in all locali- alternative hypothesis, the growth zone in the Discin- ties. This phenomenon may indicate the beginning of sonia species was located between the unpaired lobe a certain phase of the individual development of an and the rest of the body, and new isomers were animal, for example, settling of the floating stage. inserted (Hoekzema et al., 2017; Dunn et al., 2018). A The refined morphological characteristics of the pointed end overgrown with small isomers is usually phylum Proarticulata and subordinate high-rank taxa interpreted as the posterior one (Glaessner and Wade, are given below. We are aware of problems and the 1966; Wade, 1972; Runnegar, 1982), but this became conventionality of suprageneric systematics of proar- clear only when oriented movement and feeding traces ticulates since: despite the extensive fossil material of animals were found in association with the body available many aspects remain unclear especially in imprints (Ivantsov and Malakhovskaya, 2002; Geh- terms of the anatomical organization, early ontogene- ling et al., 2005; Ivantsov, 2011). An interesting terato- sis, histology, and physiology. logical phenomenon is observed for the first time in The studied material is stored in the Borissiak Pale- the specimen of . cf. from our collection: the D menneri ontological Institute of Russian Academy of Sciences intravital splitting of the body along the axis into two (PIN) (collection nos. 3992, 3993, 4716, 4852, and parts with the formation of an additional line of alter- 4853). nating isomers (Plate III, fig. 2). This specimen confirms the assumption of the posterior terminal Phylum Proarticulata Fedonkin, 1985. Metazoans arrangement of the growth zone in proarticulates. At with a low wide body, divided completely or partially the opposite (anterior) end, many proarticulates has into two rows of the same-type elements, isomers, an unpaired lobe or unsegmented part. The Dickinso- arranged alternatively relative to the longitudinal axis nia species have sub-triangular outlines of the latter. of the body., The unsegmented head section is distin- This segment is expressed to varying degrees in the guished at the anterior end of many organisms. In taxa of Dipleurozoa and Cephalozoa and interpreted turn, in small forms, it can surround laterally the seg- as an element of the initial evolutionary cephalization mented (trunk) section. of Metazoa. It is likely that sensory cells (mechanore- Internal structures are represented by channel ceptors, chemoreceptors, thermoreceptors, and oth- complexes. One of them consists of a large axial canal, ers), reacting to various kinds of stress were concen- single or double, and a series of smaller lateral canals, trated at the anterior end of actively moving animals. sometimes dichotomously branching. This complex is The head section of small and juvenile proarticulates is interpreted as a digestive–distribution system. Another relatively large in size and can cover the body from the complex consists of many thin branching channels, anterior side and laterally (Ivantsov, 2008). The located mainly in the head section. The latter is inter- growth and transition to more adult forms was accom- preted as a secretory organ, which is also probably a panied by an abrupt increase in a number of isomers, part of the digestion system. which may indicate the existence of a particular larval Based on the traces found in association with body stage in ontogenesis (Zakrevskaya and Ivantsov, 2017). remains of trace-producers, at least, three species of The similarity of Cephalonega nom. nov. with proarticulates could move and feed by the upper layer proarticulates and, above all, with the juvenile speci- of microbial mats, destroying them with the ventral mens of some representatives of the class Cephalozoa surface. The digestion was either external or occurred is determined by the presence of the head section and in the special cavities of the digestive-distribution sys- the pattern of body segmentation, alternative arrange- tem, which opened in slits on the ventral side. The ment of the transverse elements of the trunk section, length of traces indicates that proarticulates were able and the small-tubercle sculpture of the integument. A to move relatively quickly over considerable distances

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6 (a) Linear y = 0.595x + 0.1813 2 = 0.9102 5 R Logarithmic y = 2.627ln x – 0.982 4 R2 = 0.8823

Width, mm 2

0 123456789 Length, mm 6 (b) y = 0.6346x – 0.048 R2 = 0.982 5

4 y = 0.6486x + 0.0667 R2 = 0.8887 3 y = 0.5019x + 0.4022 2 Width, mm = 0.8312 2 R Syuzma SZ1(XX) Winter Coast Z1(I) 1 Winter Coast Z11(XXII) Solza SL1(VII)

0 123456789 Length, mm

Fig. 1. Proportions of the body of Cephalonega stepanovi (Fedonkin, 1976): (a) for the species in general, (b) for different localities. that could be possible if they haddeveloped a no head section. The external ends of isomers are ori- muscular system. ented sideways and backward. The axial structure is The growth of proarticulates was caused by an composed of the axial channel and lateral branches, increase in a size of their bodies and in a number of one branch per one isomer. Genera Paravendia isomers. An addition of new isomers was at the poste- Ivantsov, 2004, Vendia Keller, 1969, and, probably, rior end of the body throughout the lifetime or only at Karakhtia Ivantsov, 2004 are ascribed to this class. the early stage of ontogenesis. It was proved that there Class Dipleurozoa Harrington et Moore, 1955. existed larvae of some species with a relatively large Proarticulates are from small to very large in size. At head and weakly segmented trunk sections. In addi- the early stage of ontogenesis, the head section is tion, it is assumed that they had other ecological pref- semicircle or wide triangle and the external ends of erences than an adult organism. isomers are oriented sideways and backward. At the The symmetry of gliding reflection, which deter- intermediate and late stages of ontogenesis, isomers mines the architectonics of some groups of the Ven- are arranged subradially, and the head section in shape dian benthos, including attached modular forms and and size is close to anterior isomers. The axial struc- mobile bilateral proarticulates, is interpreted as a result ture consists of a single or doubled axial channel and of spiral growth of the body (probably, spiral cleavage lateral branches. A number of the latter can be consid- of an egg), which allows the assumption of the phylo- erably less than a number of isomers. This class genetic link between these groups (Fedonkin, 2017). includes only one genus Dickinsonia Sprigg, 1947. Class Vendiamorpha Fedonkin, 1985. Proarticulates Class Cephalozoa Ivantsov, 2004. Proarticulates are are mainly represented by small specimens. There is from small to large in size. The head section, well

PALEONTOLOGICAL JOURNAL Vol. 53 No. 5 2019 452 IVANTSOV et al. defined at all stages of ontogenesis, is semicircular to Cephalonega stepanovi (Fedonkin, 1976) crescent in shape. The external ends of the isomers are Plate 3, figs. 5–10 backward oriented. The axial structure consists of the Onega stepanovi: Keller and Fedonkin, 1976, p. 42, pl. III, axial channel and lateral branches or only of branches; figs. 3, 6; Fedonkin, 1981, p. 71, pl. XIII, figs. 5, 6; Fedonkin, one isomer is per one branch. Sometimes, the sculp- 1985, p. 93, pl. XIX, figs. 1, 2, 4, 8, 9; Ivantsov, 2007, p. 4, pl. III, ture on the dorsal surface of juvenile specimens is rep- figs. 7, 8, fig. 3c. resented by small tubercles. This class combines the H o l o t y p e. PIN, no. 3992/5049 (formerly GIN, most of proarticlate genera, including: Andiva Fed- no. 4464/57V), impression; Arkhangelsk Region, onkin, 2002, Archaeaspinus Ivantsov, 2007, Cephal- Winter Coast of the White Sea, the Syuzma River right onega Fedonkin, nom. nov., Cyanorus Ivantsov, 2004, bank 5.5 km upstream of the mouth, Syuzma locality; Ivovicia Ivantsov, 2007, Lossinia Ivantsov, 2007, Upper Vendian, Ust-Pinega Formation, Syuzma Marywadea Glaessner, 1976, Ovatoscutum Glaessner Beds, fossil assemblage SZ1(XX) (Keller and Fed- et Wade, 1966, Podolimirus Fedonkin, 1983, Praecam- onkin, 1976, pl. III, fig. 6; Fedonkin, 1981, pl. XIII, bridium Glaessner et Wade, 1966, Spriggina Glaessner, fig. 6; Fedonkin, 1985, p. 93, pl. XIX, fig. 8). 1958, Tamga Ivantsov, 2007, and Yorgia Ivantsov, 1999. D e s c r i p t i o n. The body outlines of small specimens are elliptical, larger specimens have ovoid outlines; the maximum width is near the anterior end of SYSTEMATIC PALEONTOLOGY the trunk section. The anterior part of the head section (located ahead of the trunk section) is two times lon- CLASS CEPHALOZOA ger than the posterior one (located behind the trunk section) and its width from the lateral sides; moreover, Order and Family Incertae Sedis it is only slightly less than the length of the trunk section. Isomers are oval, subradially oriented. They Genus Cephalonega Fedonkin, nom. nov. increase in size from the first pair to the fourth one, gradually decreasing after that. A visible number of Onega (non Distant, 1908): Keller and Fedonkin, 1976, p. 42; Glaessner, 1979, p. 104; Fedonkin, 1981, p. 20;Fedonkin, 1985, isomers – 8–10 pairs. p. 56; Fedonkin, 1987, p. 104; Ivantsov, 2007, pp. 4–5. There are two variants of preservation of the trunk section. In the first case, its surface is flat or slightly E t y m o l o g y. From genus name Onega and from κεϕαλ curved in the axial part; there are no visible isomers Greek ή (head). (Pl. 3, fig. 10), or their boundaries are represented by Holotype. Onega stepanovi Fedonkin, 1976 thin grooves; sometimes there is visible sculpture, con- from the Upper Vendian of the Arkhangelsk Region. sisting of evenly scattered tubercles (Pl. 3, figs. 8, 9). Iso- mers can be well-defined both on the edges and on the D i a g n o s i s. Body with predominantly ovoid axis of the section, demonstrating the alternation, typ- outlines, with expanded and slightly blunted anterior ical of proarticulates (Pl.3 fig. 9). In the second case, a end; separated into two sections: unsegmented head wide and deep groove occurs on the axis of the section and trunk, separated into two rows of isomers; at this, and isomers occur as short, deformed to a varying the head section surrounds the trunk one all around. degree, ridges, the internal ends of which rest against Isomers are sharp oval outgrowths, small, slightly to the axial groove (Pl. 3, figs. 6, 7). Apparently, these elongated in the direction transverse to the axis of the two variants of preservation indicate different stages of body, arranged into a compact group. The dorsal sur- decomposition of the tissue of the trunk section, face is covered by small tubercles. Two backward-ori- which was accompanied by a collapse of the least ented thin filamentous outgrowths extend from the dense sites, inner parts of isomers and the axial struc- posterior margin of the trunk section. ture (Fig. 2). C o m p a r i s o n. This genus is similar to small The external margin of the head section is outlined proarticulates and juvenile forms of large Cephalozoa by a thin rim, which is the most prominent at the ante- species in the way the head section surrounds all iso- rior end. The dorsal surface is covered by small conical mers (Tamga, Yorgia, Ovatoscutum) and tuberculose tubercles, which increase in size from the external sculpture of the dorsal surface (Yorgia, Archaeaspinus, margin towards the center. Two thin backward-ori- Lossinia). It differs in ovoid outlines of the body and ented filamentous outgrowths extend from the poste- small isomers, arranged into a compact group and in rior margin of the trunk section (Pl. 3, fig. 6). The the presence of filamentous outgrowths. length of these outgrowths does not exceed a half- length of the trunk section (Ivantsov et al., 2019, text- R e m a r k s. The formal diagnosis of the genus was fig. 3). first presented in (Glaessner, 1979). The position of the anterior end of the body was determined by anal- D i m e n s i o n s (Fig. 1). The minimum length, ogy with other proarticulates. 2.5 mm, a maximum length, 8.2 mm; in addition, there is a fragmentary specimen larger in size, but C o m p o s i t i o n. Type species. poorly preserved (PIN, no. 4853/1120), which belongs

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(b)

AS IS

(c)

FO (a)

Fig. 2. Schematic reconstruction of Cephalonega stepanovi (Fedonkin, 1976): (a) dorsal view, cuticle cover on the right half of the trunk section is removed, (b) transverse section, (c) the same, for the collapsed body. Abbreviations: (IS) isomer, (AS) axial structure, (FO) filamentous outgrowths. supposedly to the species being described; incomplete The field works and the preparation of the fossil material length, 17 mm. was supported by the Russian Foundation for Basic D i s t r i b u t i o n. Upper Vendian, Ust-Pinega Research (project no. 17-05-02212-a). The laboratory and Formation, Syuzma, Zimnie Gory, and Erga beds; theoretical investigations were performed within the frame- southeastern White Sea Region, Arkhangelsk Region. work of the state assignment of Paleontological Institute of Russian Academy of Sciences “The emergence of life, the M a t e r i a l. One hundred and nineteen speci- formation of the biosphere, and development of ancient mens, including 80 specimens from the Syuzma local- biotas”. ity, fossil assemblage SZ1(XX), PIN, nos. 3992/401, 504, 505, 5003, 5005, 5006, 5008, 5016–5023, 5025– 5046, 5049–5051, 5074, 5075, 5078, 5081–5089, REFERENCES 5102–5107, 5111–5131, 5133; 4 specimens from the Bobrovskiy, I., Krasnova, A., Ivantsov, A., Luzhnaya Karakhta Yuzhnoe locality, fossil assemblage K2(VI), (Serezhnikova), E., and Brocks, J.J., Simple sediment rhe- PIN, nos. 4852/103, 111, 270, 276; 17 specimens from ology explains the Ediacara biota preservation, Nat. Ecol. the Solza locality, fossil assemblage SL1(VII) Evol., 2019, vol. 3, no. 4, pp. 582–589. “Osnovnoe,” PIN, nos. 4853/94, 158, 598, 600–603, Dunn, F.S., Liu, A.G., and Donoghue, P.C.J., Ediacaran 840–846, 1042, 1043, 1096; 2 specimens from an developmental biology, Biol. Rev., 2018, vol. 93, no. 2, undesignated fossil assemblage, PIN, nos. 4853/1120, pp. 914–932. 1121; 1 specimen from the Zimnie Gory locality, Elo- Dzik, J. and Ivantsov, A.Yu., An asymmetric segmented or- voe Yuzhnoe locality, PIN, no. 3993/6439), 10 speci- ganism from the Vendian of Russia and the status of the mens from fossil assemblage Z11(XXII) “Upper yel- Dipleurozoa, Hist. Biol., 1999, vol. 13, pp. 255–268. low,” PIN, nos. 3993/5682, 5690, 6395-97, 6415, Dzik, J. and Martyshyn, A., Taphonomy of the Ediacaran 6663–6666; and 5 specimens from fossil assemblage Podolimirus and associated dipleurozoans from the Vendi- Z1(I) “Kimberella lenses,” PIN, nos. 3993/5617, an of Ukraine, Precambrian Res., 2015, vol. 269, pp. 139– 5618, 5685, 5689, 6893. 146. Evans, S.D., Droser, M.L., and Gehling, J.G., Highly reg- ACKNOWLEDGMENTS ulated growth and development of the Ediacara macrofossil Dickinsonia costata, Plos One, 2017, vol. 12, no. 5, pp. 1–15. The authors are grateful to Dr. Arthur Anker (The Fed- Fedonkin, M.A., Belomorskaya biota venda (dokembriiska- eral University of Goiás, Brazil) for reminding about the ya besskeletnaya fauna severa Russkoi platformy) (White Sea taxonomic situation with the name Onega. Vendian Biota: Precambrian Non-Skeletal Fauna of the

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Northern Russian Platform), Tr. Geol. Inst. Akad. Nauk deniya akad. A.V. Ivanova. Chast’ I.) (Proc. St. Petersburg SSSR, vol. 342, Moscow: Nauka, 1981. Soc. Nat. A Contribution to the 100th Anniversary of Aca- Fedonkin, M.A., Systematic description of Vendian Meta- demician A.V. Ivanov “Evolutionary Morphology of Ani- zoa, in Vendskaya sistema. Istoriko-geologicheskoe i paleon- mals”), Mamkaev, Yu.V., Ed., Tr. S.-Peterb. Ob-va Eastest- tologicheskoe obosnovanie. T. 1. Paleontologiya (Vendian voispyt., Ser. 1. vol. 97, St. Petersburg: S.-Peterb. Gos. System. Historical Geology and Paleontological Substanti- Univ., 2008, pp. 32–42. ation. Vol. 1. Paleontology), Moscow: Nauka, 1985, Ivantsov, A.Yu., Feeding traces of proarticulata—the Ven- pp. 70–106. dian metazoa, Paleontol. J., 2011, vol. 45, no. 3, pp. 237– Fedonkin, M.A., Besskeletnaya fauna venda i ee mesto v 248. evolyutsii Metazoa (Soft-Bodied Vendian Fauna and Its Ivantsov, A.Yu. and Malakhovskaya, Ya.E., Gigantic traces Place in the Evolution of Metazoa), Tr. Paleontol. Inst. of Vendian animals, Dokl. Earth Sci., 2002, vol. 385, no. 3, Akad. Nauk SSSR, vol. 226, Moscow: Nauka, 1987. pp. 618–622. Fedonkin, M.A., Andiva ivantsovi gen. et sp. nov. and relat- Ivantsov, A.Yu., Zakrevskaya, M.A., and Nagovitsyn, A.L., ed carapace-bearing Ediacaran fossils from the Vendian of Morphology of integuments of the Precambrian animals, the Winter Coast, White Sea, Russia, Ital. J. Zool., 2002, Proarticulata, Invertebr. Zool., 2019, vol. 16, no. 1, pp. 19–26. vol. 69, pp. 175–181. Jenkins, R.J.F., Functional and ecological aspects of Edi- Fedonkin, M.A., Symmetry of gliding reflection in the acaran assemblages, in Origin and Early Evolution of the Vendian (Ediacaran) invertebrates: a hint to the spiral mode Metazoa, Lipps, J. and Signor, P., Eds., Topics in Geobiol- of body growth, and probably, to the spiral cleavage of an egg ogy, vol. 10, New York: Plenum Press, 1992, pp. 131–176. in early metazoan evolution? in Abstr. IV Int. Congr. Invertebr. Morphol., Moscow: Pero, 2017. Keller, B.M. and Fedonkin, M.A., New organic fossil finds in the Precambrian Valday Series along the Syuzma River, Gehling, J.G., Droser, M.L., Jensen, S.R., and Runnegar, B.N., Izv. Akad. Nauk SSSR, Ser. Geol., 1976, no. 3, pp. 38–44. Ediacara organisms: relating form to function, in Evolving Form and Function: Fossils and Development, New Haven: Keller, B.M., Menner, V.V., Stepanov, V.A., and Chuma- Yale Univ. Press., 2005, pp. 43–66. kov, N.M., New finds of Metazoa in the Vendomian of the Russian Platform, Izv. Akad. Nauk SSSR, Ser. Geol., 1974, Glaessner, M.F., Precambrian, in Treatise on Invertebrate no. 12, pp. 130–134. Paleontology, Part A, Lawrence: Univ. Kansas Press., 1979, pp. 79–117. Runnegar, B., Oxygen requirements, biology and phyloge- Glaessner, M.F. and Wade, M., The Late Precambrian fos- netic significance of the late Precambrian worm Dickinso- sils from Ediacara, South Australia, Palaeontology, 1966, nia, and the evolution of the burrowing habit, Alcheringa, vol. 9, pp. 599–628. 1982, vol. 6, no. 3, pp. 223–239. Gold, D.A., Runnegar, B., Gehling, J.G., and Jacobs, D.K., Sperling, E.A. and Vinther, J., A placozoan affinity for Ancestral state reconstruction of ontogeny supports a bilat- Dickinsonia and the evolution of late Proterozoic metazoan erian affinity for Dickinsonia, Evol. Dev., 2015, vol. 17, feeding modes, Evol. Dev., 2010, vol. 12, no. 2, pp. 201– pp. 315–324. 209. Hoekzema, R.S., Brasier, M.D., Dunn, F.S., and Liu, A.G., Takiya, D.M. and Cavichioli, R.R., A review of the Neo- Quantitative study of developmental biology confirms tropical sharpshooter genus Onega Distant, 1908 (Hemip- Dickinsonia as a metazoan, Proc. R. Soc. B, 2017, vol. 284, tera: Cicadellidae: Cicadellini), Zootaxa, 2004, vol. 718, no. 1862, pp. 1–9. no. 1, pp. 1–19. Ivantsov, A.Yu., Vendian animals in the phylum Proarticu- Wade, M., Dickinsonia: polychaete worms from the Late lata, in Abstr. Int. Conf. IGSP Project 493 “The Rise and Fall Precambrian Ediacaran fauna, South Australia, Mem. of the Vendian Biota”, Padova, 2004. Queensl. Mus., 1972, vol. 16, no. 2, pp. 171–190. Ivantsov, A.Yu., Small Vendian transversely articulated fos- Zakrevskaya, M.A. and Ivantsov, A.Yu., Dickinsonia costa- sils, Paleontol. J., 2007, vol. 41, no. 2, pp. 113–122. ta—the first evidence of neoteny in Ediacaran organisms, Ivantsov, A.Yu., Proarticulata—a phylum of Metazoan ani- Invertebr. Zool., 2017, vol. 14, no. 1, pp. 92–98. mals that became extinct in the Precambrian, in Evolyut- sionnaya morfologiya zhivotnykh: k stoletiyu so dnya rozh- Translated by D. Voroshchuk

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