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New dasycladalean algal species from the Kalana Lagerstätte (Silurian, Estonia)

Published online by Cambridge University Press:  28 April 2015

Viirika Mastik and
Oive Tinn
Viirika Mastik
Affiliation:
Department of Geology, University of Tartu, Ravila 14A, 50411 Tartu, Estonia, 〈viirika.mastik@ut.ee〉, 〈oive.tinn@ut.ee〉
Oive Tinn
Affiliation:
Department of Geology, University of Tartu, Ravila 14A, 50411 Tartu, Estonia, 〈viirika.mastik@ut.ee〉, 〈oive.tinn@ut.ee〉
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Abstract

A Silurian (Llandovery, Aeronian) Lagerstätte in Kalana, Estonia, has revealed exceptionally preserved noncalcified thalli of dasycladalean (divison Chlorophyta) algal fossils. The siphonous, serially segmented fossils of Palaeocymopolia silurica n. sp. are closely similar to P. nunavutensis, a Ludlovian species from the Arctic Canada. The occurrence of closely related species at Baltica and Laurentia paleocontinents indicates a wide distribution of noncalcified algal flora on both sides of the Iapetus Ocean in the Paleozoic. The exceptionally well-preserved specimens from the Kalana Lagerstätte show similarity to extant species Cymopolia barbata, with lack of a calcium carbonate skeleton being the major observable difference from the latter.

Information

Type
Articles
Information
Journal of Paleontology , Volume 89 , Issue 2 , March 2015, pp. 262 - 268
Copyright
Copyright © 2015, The Paleontological Society 

Introduction

Algae constitute a number of polyphyletic or paraphyletic groupings of primarily aquatic photoautotrophic organisms (Taylor et al., Reference Taylor, Taylor and Kings2009; Graham and Wilcox, Reference Graham and Wilcox2000). Molecular clock studies suggest that the first algae occurred on Earth during the late Paleoproterozoic, approximately 1.5 Ga ago (Yoon et al., Reference Yoon, Hackett, Ciniglia, Pinto and Bhattacharya2004; Taylor et al., Reference Taylor, Taylor and Kings2009), but, based on microfossils, it has also been argued (Moczydlowska et al., Reference Moczydlowska, Landing, Zang and Palacios2011) that their origin predates 1.8 Ga. Whereas the Precambrian fossil record of algae is meager, the Phanerozoic record has greatly benefited from the ability of several algal groups to precipitate or deposit CaCO3 (Brownlee and Taylor, Reference Brownlee and Taylor2002). However, because the vast majority of algae do not calcify (Taylor et al., Reference Taylor, Taylor and Kings2009), all fossils of non-calcifying macroalgae are of special value.

The Paleozoic noncalcified algae are known from a few Lagerstätten, where some of them show well-preserved delicate morphology. Several green algae fossil localities of Silurian age have been discovered in North America; the best known are Waukesha, Wisconsin (LoDuca et al., Reference LoDuca, Kluessendorf and Mikulic2003); Gasport, New York (LoDuca and Brett, Reference LoDuca and Brett1997; Ruedemann, Reference Ruedemann1925); Hamilton, Ontario (LoDuca, Reference LoDuca1995); Cornwallis Island, Canada (LoDuca et al., Reference LoDuca, Melchin and Verbruggen2011); and New Brunswick, Canada (LoDuca et al., Reference LoDuca, Miller and Wilson2013). In Europe, exceptionally preserved algal fossils of Silurian age have been found in Kommersøy, Norway (Høeg, Reference Høeg1937); Gotland and Skåne, Sweden (Nitecki and Spjeldnaes, Reference Nitecki and Spjeldnaes1993; Kenrick and Vinther, Reference Kenrick and Vinther2006); Aymestry, England (Elliott, Reference Elliott1971); and Podolia, Ukraine (Ishchenko, Reference Ishchenko1985). A similar fossil algal locality has also been mentioned (Korde, Reference Korde1993) in the Eastern Sayan Mountains, Russia.

The algal flora in the Kalana Lagerstätte, Estonia, comprises approximately ten morphologically distinguishable macroscopic species (Tinn et al., Reference Tinn, Meidla, Ainsaar and Pani2009). Many algal fossils in Kalana can be classified to the green algal order Dasycladales (divison Chlorophyta, Class Ulvophyceae), an extant group of tropical to subtropical, shallow-water marine green algae, with a long and highly diverse geological history that is dominated by calcareous forms (Berger and Kaever, Reference Berger and Kaever1992; Kenrick and Vinther, Reference Kenrick and Vinther2006). Having been in existence since the Cambrian (Berger and Kaever, Reference Berger and Kaever1992; Deloffre, Reference Deloffre1988), the dasyclades comprise a large and significant component of the algal fossil record that includes five families with nearly 200 genera, some of which have a fairly large number of species (Berger and Kaever, Reference Berger and Kaever1992). The dasyclade flora in Kalana includes the species treated in this paper (Palaeocymopolia silurica new species), and also Medusaegraptus mirabilis, Chaetocladus sp., and Inopinatella sp., and several species that remain to be treated in additional papers.

Geological setting

The specimens described in the present study were collected from a quarry near Kalana village in Central Estonia (Fig. 1.1, 1.2). The working quarry exposes a limestone and dolomite succession of early Aeronian (Llandovery, Silurian) age, in local stratigraphy known as the Raikküla regional stage (Fig. 1.3). The outcrop area of the Raikküla regional stage extends as a latitudinal, eastward-widening belt from the west coast up to eastern Estonia. In boreholes, the thickness of the Stage varies between 16.3 m in the northwest up to 176.3 m in the southwest; in the outcrop area, the thickness is between 20 to 75 m (Nestor, Reference Nestor1997).

Figure 1

Geographical position (1) and simplified geological map of Estonia (2). Gray color indicates the outcrop area of strata belonging to the Raikküla Stage. The stratigraphical column (3) demonstrates the lithology of the algal beds of the Raikküla Stage.

The Raikküla Stage consists of a variety of carbonate rocks, the most characteristic of which are micro- and cryptocrystalline limestones cyclically interbedding with marl- or mudstones in the south and wacke-, pack-, and grainstones in the north (Nestor, Reference Nestor1997). In several places, the carbonates are secondarily dolomitized. However, primary dolomites have also been described in some sections in Central Estonia, where they form the uppermost parts of shallowing-upwards sedimentary cycles (Nestor, Reference Nestor1997). The Raikküla Stage consists of the Raikküla, Nurmekund, and Saarde formations, laterally replacing each other from north to south (Nestor, Reference Nestor1997), whereas its five local subdivisions have been regarded as sedimentary mesocycles (Nestor et al., Reference Nestor, Einasto, Männik and Nestor2003).

The quarry exposes the boundary section of the Jõgeva and Imavere beds of the Nurmekund Formation, which consists of wavy-bedded to nodular secondary micritic dolostone intercalating with thin interlayers or films of dolomitic marlstone. The marlstone intercalations are mostly light-brown, microlaminated, and contain kerogenuous material and specific organic detritus of algae, which have been described as “dendroids,” Leveillites, and Rhadinograptus (Kaljo, Reference Kaljo1970; Nestor et al., Reference Nestor, Einasto, Männik and Nestor2003). The most abundant noncalcified macroscopic algal remains occur in the lower part of the quarry, in the light to dark brown organic-rich, microlaminated, partly dolomitized limestones, which form thin laminae on the bedding planes of micritic limestone layers. Most of the algal material occurs as fine interlayers in 2–10 cm thick dolomitic beds.

Biostratigraphically, the Raikküla Stage correlates with the Aspelundia Superzone (Männik, Reference Männik2007); the algal layers are within the Pranognathus tenuis conodont zone (Ainsaar et al., Reference Ainsaar, Tinn, Männik and Meidla2014).

Material

The algal material includes complete thalli as well as fragments of different sizes and states of preservation. Palaeocymopolia silurica n. sp. occurs as black or dark gray carbonaceous fossils. The studied material falls largely into three types of preservation. The first type (Fig. 2.1) consists of abundant, individual 0.4–0.7 cm-long disjointed ‘repetitive elements.’ The slabs are covered with fine, 1–2 mm thick, organic-rich layers of algal fragments and disarticulated organic debris. The material of that type comprises 13 slabs, with a total area of 29.5 dm2.

Figure 2

Three different types of the preservation of the material. The first type (1) consists of abundant individual disjointed repetitive elements (TUG 1269-12). Material of the second type (2) consists of the fragments of sparsely distributed 3-dimensional cylindrical carbonaceous main axis and occasional repetitive elements on some branches (TUG 1269-13). The third type (3) comprises nearly complete branching thalli (TUG 1269-14).

Material of the second type (Fig. 2.2) consists of sparsely distributed fragments of three-dimensionally preserved cylindrical carbonaceous main axes, some of them showing bifurcations, and occasional ‘repetitive segments’ on some ‘branches.’ Mudstone layers with algae of that type of preservation exhibit also a number of dark gray, pyritic, linear structures of variable orientation and numerous calcitic infillings. Twelve rock samples, one of which is two-sided, were collected from this type, with a total area about 30 dm2.

The third type includes slabs with nearly complete branching thalli (Fig. 2.3). The collection of specimens of that type of preservation comprises 52 rock samples, four of them with counterparts, with a total area of 96 dm2.

Two drillcores (Fig. 1.2) from different parts of Estonia have also revealed rare Palaeocymopolia specimens: the Laeva drillcore (353-2290) (at 38.3 m depth), and Kullamaa (Võhma) drillcore (353-3539) (at 53.55 m depth).

The beds with fossilized algae contain also a number of faunal fossils. These are mostly calcitic, but occasional partly dolomitized or silicified specimens occur as well. The normal-marine shelly carbonate fauna (rhynchonelliformean brachiopods and gastropods) occurs mostly as coquina lenses varying between one and several centimeters in thickness and ten centimeters to several meters in lateral extent. Occasional rugose and tabulate corals, sponges, nautiloids, crinoids, and bryozoans can also be found. Some surfaces show graptolites; micropaleontological samples yield low-diversity scolecodont and ostracode fauna. In addition to typical normal-marine sediments and fauna, certain beds show thin lamination, layers with desiccation cracks, abundant leperditiid crustaceans, and occasional eurypterid remains, indicating a shallow lagoonal environment.

The studied beds are not devoid of ichnofossils. Although the majority of samples do not reveal any bioturbation or show rare discrete isolated traces only, in places the degree of bioturbation shows completely disturbed beds, allowing ranking of the ichnofabric with classification index 5 sensu Droser and Bottjer (Reference Droser and Bottjer1986). As a rule, however, trace fossils do not occur together with best-preserved algal thalli.

Systematic paleontology

The described and photographed material is housed at the Natural History Museum of the University of Tartu, Estonia, under the collection number TUG 1269. The drillcore material is housed at the Institute of Geology at Tallinn University of Technology.

Division Chlorophyta Pascher, Reference Pascher1914, emend. Lewis and McCourt, Reference Lewis and McCourt2004

Class Ulvophyceae Mattox and Stewart, Reference Mattox and Stewart1984

Order Dasycladales Pascher, Reference Pascher1931

Remarks

Taxonomically, the Dasycladales is an order of large unicellular green algae in the class Ulvophyceae. The members of the order Dasycladales are a clearly defined group with siphonous, radially symmetrical nonseptate thallus. The usually elongated cell may be large, measuring up to 200 mm (Berger and Kaever, Reference Berger and Kaever1992). In the course of growth, the main axis generates numerous regularly positioned branched laterals, arranged in regular whorls. The cell is anchored to a substratum by means of nonseptate rhizoidal branches that are in open communication with the main axis. The systematic classification of fossil as well as Recent Dasycladales has been described comprehensively by Berger and Kaever (Reference Berger and Kaever1992), LoDuca (Reference LoDuca1997), Lee (Reference Lee2008), and Graham et al. (2009).

At present, two families, Dasycladaceae and Acetabulariaceae, are extant and include only 11 genera. This low number of extant genera has been regarded as an indication of waning of the order (Berger and Kaever, Reference Berger and Kaever1992), and has caused the Recent species to be designated as ‘living fossils.’

The dasycladalean fossil record extends back to the Cambrian. The oldest fossils assigned to Dasycladales are Yakutina aciculata (Korde, Reference Korde1973; Riding, Reference Riding1994, Reference Riding2001; Verbruggen et al., Reference Verbruggen, Ashworth, LoDuca, Vlaeminck, Cocquyt, Sauvage, Zechman, Littler, Littler, Leliaert and De Clerck2009) and Seletonella mira from the upper Cambrian (Korde, Reference Korde1973; Riding Reference Riding1994, Reference Riding2001; Verbruggen et al., Reference Verbruggen, Ashworth, LoDuca, Vlaeminck, Cocquyt, Sauvage, Zechman, Littler, Littler, Leliaert and De Clerck2009). Both species belong to family Seletonellaceae, a group of extinct Dasyclades, that, unlike living representatives, have an endospore type of reproduction, meaning that the gametes were situated within the main axis (Verbruggen et al., Reference Verbruggen, Ashworth, LoDuca, Vlaeminck, Cocquyt, Sauvage, Zechman, Littler, Littler, Leliaert and De Clerck2009).

Family Triploporellaceae Berger and Kaever Reference Berger and Kaever1992

Genus Palaeocymopolia LoDuca et al., Reference LoDuca, Melchin and Verbruggen2011

Diagnosis

Noncalcified serial-segmented thallus with dichotomous branching and a corticated structure; segments clavate or pyriform, each comprising a cylindrical main axis and cylindrical laterals arranged in radial fashion (emended from LoDuca et al., Reference LoDuca, Melchin and Verbruggen2011).

Palaeocymopolia silurica new species

Figures 3.1, 3.2, 4.1–4.9

Holotype

TUG 1269-9 (Fig. 3.1).

Figure 3

Palaeocymopolia silurica n. sp. (1) Holotype (TUG 1269-9), and (2) (TUG 1269-11) are counterparts of slabs with nearly complete branching thalli.

Diagnosis

Noncalcified serially segmented thallus with central cylindrical main axis. Dichotomous branching at every second to fifth repetitive element, up to six repetitive elements after the last branching. Branches terminating with bundles of fine hair-like filaments, which occur also between two last segments.

Occurrence

Strata of Aeronian age, Raikküla Stage, quarry near Kalana village, and two drillcores (Laeva and Kullamaa), Estonia.

Description

Thallus distinctly serially segmented. The largest specimen (the type specimen TUG 1269-9) shows a system of three main “branches.” The height of the largest specimen is ~10 cm. The specimens branch dichotomously at every second to fifth repetitive element.

At the center of each segment is a cylindrical main axis (Figs. 4.6, 4.7; 5.1), synonymized here with central cylinder, 0.20–0.55 mm in diameter. The main axis runs through the whole thallus, branching dichotomously at every second to fifth repetitive element. In places, the branching axis can be observed through broken segments (Fig. 4.6); occasionally, the carbonized fragments of axes are the only preserved parts of the thallus (Fig. 4.7).

Figure 4

Details of P. silurica. (1) (TUG 1269–15); (2) (TUG 1269–19); and (3) (TUG 1269–16) show different branches terminating with bundles of fine filaments. (2) Shows also bifurcation of the hair-like filaments, pointed out with an arrow. (4), (TUG 1269-14) The Palaeocymopolia silurica n.sp. growing tip is pointed out with an arrow; (4, 5). (TUG 1269-17) show different shapes of repetitive elements. (6, 7). (TUG 1269-18) Variously preserved main axis pointed out with arrows. (8) Polygonal structures on the segments that could be interpreted as facets. (9) Enlargement of box in Figure 4.8 (TUG 1269-14).

Figure 5

Labeled reconstruction of Palaeocymopolia silurica n. sp. (1), Main axis; (2) repetitive elements; (3) growing tip; (4) polygonal structure; and (5), hair-like filaments.

Repetitive elements (segments) are barrel-shaped to pyriform (Figs. 4.4, 4.5; 5.2). The lengths of individual elements are 2.4–11 mm (average=6.1 mm), width 1.2–4.9 mm (average=2.7 mm). At the growing tips of some “branches,” small, rounded structures can be observed (Figs. 4.4; 5.3) that probably represent the new growing tips for branches or hair-like filaments.

A number of specimens show polygonal structures on the segments that could be interpreted as facets (Figs. 4.8, 4.9; 5.4), which possibly covered the reproductive structures, normally described as gametangia in the genus. There are approximately 55 whorls in a single repetitive element.

At the growing tips and between the last two segments, the branches terminate with a bundle of slender hair-like filaments (Figs. 4.1–4.3; 5.5), which are up to 3 mm long and 0.03 mm wide; some individual filaments show bifurcation (Fig. 4.2)

Etymology

The name refers to the age of the species.

Remarks

LoDuca et al. (Reference LoDuca, Melchin and Verbruggen2011) described a closely similar species as Palaeocymopolia nunavutensis from the Silurian (Ludlovian) of Cornwallis Island, Arctic Canada. The major similarity shared by P. silurica and P. nunavutensis is a noncalcified, dichotomously branching serially segmented thallus, which comprises a cylindrical main axis in the same size range (diameter of the main axis of P. silurica is 0.2–0.55 mm; the diameter of the main axis of P. nunavutensis is 0.25–0.5 mm).

Palaeocymopolia nunavutensis was described (LoDuca et al., Reference LoDuca, Melchin and Verbruggen2011) as an endosporate species, meaning that the gametangia were positioned in the central axis. However, LoDuca et al. (Reference LoDuca, Melchin and Verbruggen2011) had no positive evidence of endosporate condition, and this statement was based on negative evidence only. The abundant and well-preserved specimens from Kalana have not revealed any features that could suggest endosporate condition of the species. Moreover, although we have not observed in our material anything that could be certainly assigned as gametangia, several specimens (Fig. 4.8,4.9) show well-preserved polygonal structures on the segments that could be interpreted as facets that covered the reproductive structures. Therefore, it is equally possible that the gametangia have not been preserved in our material and the specimens were of choristospore type of morphology. Nonetheless, as far as the fossils have not revealed the position of gametangia, it is not possible to decide with confidence if the species had endo- or choristosporate type of arrangement of reproductive structures. Therefore, the genus Palaeocymopolia is emended to remove endosporate reproduction as a diagnostic feature.

The detailed inspection reveals that the shape of the repetitive elements of the specimens of P. nunavutensis from Canada and P. silurica from Estonia is also somewhat different. Those from Estonia show more rounded edges and larger variation of shapes than the Canadian specimens. The Estonian specimens branch dichotomously at every second to fifth repetitive element, compared to the Canadian specimen, which has fewer branchings. In addition, the well-preserved specimens of P. silurica show branches terminating with bundles of bifurcating fine hair-like filaments (Fig. 4.2), which also occur between the two last segments. However, such structures have not been described in P. nunavutensis. On the other hand, the fossil material from Kalana is far more abundant and so could possibly show more disparity than the few fragments from Canada; also, the variations in segment shape of the Estonian material may also be due to thallus deformation resulting from compression.

The fossilized thalli of P. silurica (Fig. 5) are closely similar to those of the extant dasycladalean alga Cymopolia barbata. While LoDuca et al. (Reference LoDuca, Melchin and Verbruggen2011) claimed that the absence of the branching hair-like filaments between the segments and the endosporate condition are the main differences between the Recent genus Cymopolia and the Silurian genus Palaeocymopolia, these characters do not seem to be critical in the case of P. silurica. In both cases, thalli with dichotomously branching, serially segmented form, segment size, and shape, and size and morphology of filaments in the tufts, are comparable in these taxa. P. silurica has preserved morphology consistent with Cymopolia, but many of the diagnostic features of this extant genus could not be evaluated for the Silurian material because of their loss in the process of fossilization. However, even if the preservation plays a role in character occurrence, a new taxon is permitted as indicated in Chapter 1, Article 1.2, Example 3 of the International Code of Nomenclature for algae, fungi, and plants, 2012 (Melbourne Code), and in Chapter 2, Section 3, Article 11.1 (McNeill et al., Reference McNeill, Barrie, Buck, Demoulin, Greuter, Hawksworth, Herendeen, Knapp, Marhold, Prado, Prud’homme Van Reine, Smith, Wiersema and Turland2012).

Most Cymopolia species from the Cretaceous to Recent, and extant C. barbata, are strongly calcified, especially in their cortex. Recent Dasycladales deposit a biogenic calcium carbonate, mostly aragonitic, skeleton, although to a different extent. It has been argued (Berger and Kaever, Reference Berger and Kaever1992) that, depending on environmental conditions, this fine coat might also be missing. However, the fossils of P. silurica, as well as other algal remains in the Kalana deposit, are preserved as carbonaceous remnants that do not show traces of internal or external calcification. In some instances, decalcification can remove the skeleton (LoDuca and Brett, Reference LoDuca and Brett1997), but because numerous carbonate fossils, e.g., ostracodes, bryozoans, etc., are present in the studied beds, decalcification has probably not occured in Kalana. LoDuca et al. (Reference LoDuca, Melchin and Verbruggen2011) hypothesized that noncalcified algae could have been widespread in the Paleozoic seas and our incomplete knowledge of such flora stems from their poor preservation potential.

At present, all 38 living species of the order Dasycladales inhabit tropical to subtropical shallow subtidal settings (Berger and Kaever, Reference Berger and Kaever1992; Graham et al., 2009), preferring shallow-marine euhaline waters, protected from strong storm and ground waves. During early Silurian times, the Baltic Paleobasin was located approximately 10°–20°S of the equator (Cocks and Torsvik, Reference Cocks and Torsvik2005). According to the present geological records, and relying on the available fossil data, the material was deposited in conditions of normal-marine salinity and probably in shallow water protected from direct wave action. The available data show that similar conditions also dominated in the Laurentian Paleobasin on the other side of the Iapetus Ocean, where the algal flora of the similar Konservat-Lagerstätten of North America, although of somewhat younger age, has been described (LoDuca, Reference LoDuca1997; LoDuca and Brett, Reference LoDuca and Brett1997; LoDuca et al., Reference LoDuca, Kluessendorf and Mikulic1999, Reference LoDuca, Kluessendorf and Mikulic2003, Reference LoDuca, Melchin and Verbruggen2011). The presence of closely related species offshore of two different paleocontinents can be taken as evidence of a broad distribution area of the genus.

Conclusions

The exceptionally well-preserved siphonous, serially segmented thalli of Palaeocymopolia silurica n. sp. from the Kalana Lagerstätte in Estonia show close similarity to P. nunavutensis from the Silurian of Arctic Canada. However, as the fossils of P. silurica have not revealed the position of gametangia, it is not possible to decide with confidence if the described species had endo- or choristosporate type of arrangement of reproductive structures.

P. silurica in Estonia is approximately 15 Mya older than the Canadian species P. nunavutensis, and it therefore is the oldest serially segmented macroalga with corticated tissue. Their distribution in the Baltic as well as in the Laurentian paleobasins indicates a wide distribution of noncalcified dasyclade algal flora on both sides of the Iapetus Ocean in the Paleozoic.

The exceptionally well-preserved specimens from the Kalana Lagerstätte show similarity to extant species Cymopolia barbata, but many of the diagnostic features of the extant genus could not be evaluated for the Silurian material because of their loss during the process of fossilization.

Acknowledgments

We thank S. T. LoDuca, R. Lupia, and an anonymous reviewer for helpful comments on an earlier version. We are grateful to all the people who helped to collect fossils during different field sessions, and special thanks to Tõnu Pani for introducing us these exceptional layers. We also appreciate the kind help of L. Ainsaar and the geology team of Tallinn Technical University. This study was supported financially by the Estonian Research Council (grant No. ETF9231, target finance project SF0180051s08 and and IUT20-34). This study is a contribution to the IGCP Project 591 “The Early to Middle Paleozoic Revolution.”

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Figure 0

Figure 1Geographical position (1) and simplified geological map of Estonia (2). Gray color indicates the outcrop area of strata belonging to the Raikküla Stage. The stratigraphical column (3) demonstrates the lithology of the algal beds of the Raikküla Stage.

Figure 1

Figure 2Three different types of the preservation of the material. The first type (1) consists of abundant individual disjointed repetitive elements (TUG 1269-12). Material of the second type (2) consists of the fragments of sparsely distributed 3-dimensional cylindrical carbonaceous main axis and occasional repetitive elements on some branches (TUG 1269-13). The third type (3) comprises nearly complete branching thalli (TUG 1269-14).

Figure 2

Figure 3Palaeocymopolia silurica n. sp. (1) Holotype (TUG 1269-9), and (2) (TUG 1269-11) are counterparts of slabs with nearly complete branching thalli.

Figure 3

Figure 4Details of P. silurica. (1) (TUG 1269–15); (2) (TUG 1269–19); and (3) (TUG 1269–16) show different branches terminating with bundles of fine filaments. (2) Shows also bifurcation of the hair-like filaments, pointed out with an arrow. (4), (TUG 1269-14) The Palaeocymopolia silurica n.sp. growing tip is pointed out with an arrow; (4, 5). (TUG 1269-17) show different shapes of repetitive elements. (6, 7). (TUG 1269-18) Variously preserved main axis pointed out with arrows. (8) Polygonal structures on the segments that could be interpreted as facets. (9) Enlargement of box in Figure 4.8 (TUG 1269-14).

Figure 4

Figure 5Labeled reconstruction of Palaeocymopolia silurica n. sp. (1), Main axis; (2) repetitive elements; (3) growing tip; (4) polygonal structure; and (5), hair-like filaments.