Cambrian palaeoscolecids (Cycloneuralia) from Gondwana and reappraisal of species assigned to Palaeoscolex

Gondwana Research 24 (2013) 780–795

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Cambrian palaeoscolecids (Cycloneuralia) from Gondwana and reappraisal of species assigned to Palaeoscolex Diego C. García-Bellido a, b,⁎, John R. Paterson c, Gregory D. Edgecombe d a

Instituto de Geociencias (CSIC, UCM), 28040-Madrid, Spain Sprigg Geobiology Centre, School of Earth & Environmental Sciences, University of Adelaide, SA 5005, Australia Division of Earth Sciences, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia d Department of Earth Sciences, The Natural History Museum, London SW7 5BD, UK b c

a r t i c l e

i n f o

Article history: Received 22 August 2012 Received in revised form 9 November 2012 Accepted 12 December 2012 Available online 2 January 2013 Handling Editor: M. Santosh Keywords: Palaeoscolecida Wronascolex Cambrian Australia Spain

a b s t r a c t The discovery of new palaeoscolecid material (Cycloneuralia) from the Emu Bay Shale Konservat-Lagerstätte of Kangaroo Island, South Australia (Cambrian Series 2, Stage 4) and from the Murero biota of NE Spain (Cambrian Series 3, Stage 5—Drumian) has prompted a reappraisal of Palaeoscolex Whittard, 1953, the genus to which species from these, and other Cambrian localities, have most recently been assigned. Available data from scanning electron microscopy show the presence of Hadimopanella-type sclerites covering the surface of these taxa, permitting taxonomic schemes based on microfossils and whole-body compression fossils to be reconciled. The sclerite pattern, size and shape indicate that several of the Cambrian species assigned to Palaeoscolex need to be reassigned to Wronascolex Ivantsov and Zhuravlev, 2005, a genus originally described from Siberia. The studied material includes Wronascolex antiquus (Glaessner, 1979) and Wronascolex iacoborum sp. nov. from Kangaroo Island (Australia) and two new specimens of Wronascolex? from the Iberian Ranges (Spain). SEM examination of the types of Palaeoscolex ratcliffei Robison, 1969, a Cambrian species from Utah to which Murero material has been compared, suggests that this species should possibly be assigned to Wronascolex. These taxa are also considered in a Cambrian palaeobiogeographic context, together with the presence of isolated Hadimopanella sclerites, showing a distribution of Wronascolex largely confined to palaeotropical environments. © 2013 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

1. Introduction Palaeoscolecidans are a lower Palaeozoic group of vermiform animals of millimetric to decimetric size, which can be identified by the presence of an annulated cuticle with rows of phosphatic microelements. These “worms” have been known since the nineteenth century (Ulrich, 1878), but it was not until the mid 1980s that they were assigned their own class, the Palaeoscolecida (Conway Morris and Robison, 1986). The systematic affinities of the group have been under debate for some time, having been associated with the annelids (Whittard, 1953), the nematomorphs (Hou and Bergström, 1994; Wills et al., 2012), the chaetognaths (Ahnelt, 1984), and the priapulids (Conway Morris, 1997; Wills, 1998; Lehnert and Kraft, 2006; Harvey et al., 2010). All modern work has converged on the hypothesis that palaeoscolecids lie within or are allied to Cycloneuralia, a group of moulting animals that includes the extant Nematoida (Nematoda and

⁎ Corresponding author at: Sprigg Geobiology Centre, School of Earth & Environmental Sciences, University of Adelaide, SA 5005, Australia. Tel.: + 61 8 8313 4870; fax: + 61 8 8313 6222. E-mail addresses: [email protected] (D.C. García-Bellido), [email protected] (J.R. Paterson), [email protected] (G.D. Edgecombe).

Nematomorpha) and Scalidophora (Priapulida, Kinorhyncha and Loricifera) (e.g., Maas et al., 2007; Zhuravlev et al., 2011). Palaeoscolecids have been placed on the stem groups of either Cycloneuralia (Budd, 2001; Conway Morris and Peel, 2010) or Ecdysozoa as a whole, but formal phylogenetic analyses ally them most closely to either Priapulida (Harvey et al., 2010) or Nematomorpha (Wills et al., 2012). Palaeoscolecidans in Cambrian rocks have been described from Australia, the USA, China, Spain, the United Kingdom, Siberia, Greenland, Turkey, Sardinia, Kazakhstan, Iran and Antarctica. The fossils of these animals can be preserved in four modes. One is macroscopic, soft-bodied (including Burgess Shale-type) preservation within fine-grained clastics, producing thin compressions of the organisms, including their soft tissues (e.g. Conway Morris and Robison, 1986; Zhu et al., 2005). The second mode is Orsten-type preservation, where the external organic cuticle of the animals has been secondarily phosphatized, now recovered as three-dimensional microscopic cuticle fragments (but almost never as complete specimens and rarely exceeding 1 mm in length) with phosphatic elements and occasionally other structures including sensilla, preserved in their original arrangement (e.g. Müller and Hinz-Schallreuter, 1993; Topper et al., 2010). Thirdly, the microelements are also found as small shelly fossils (SSF), in the form of isolated sclerites or plates, and these have been usually

1342-937X/$ – see front matter © 2013 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.gr.2012.12.002

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Fig. 1. Simplified geological map of the early Cambrian Big Gully localities. From Paterson et al. (2012).

described under the form taxa Milaculum, Hadimopanella, Kaimenella and Utahphospha (e.g. Müller, 1973; Gedik, 1977; van de Boogaard, 1983; Hinz et al., 1990). A fourth mode has recently been described in the Cambrian of Saskatchewan (Canada), consisting of organic-walled microfossil remains of isolated sclerites (Butterfield and Harvey, 2012, fig. 3D), now termed “small carbonaceous fossils” (SCFs). Considerable problems arise when comparing morphological characters among these forms, particularly when trying to determine the complete size of the animal and ontogenetic variability (seldom known for the microfossil forms), as well as the detailed structure of cuticle between sclerites (which is rarely preserved in compressed macrofossils), thus making it difficult to resolve relationships between taxa preserved in different modes. The fact that as many as 14 different Orsten-type taxa, some with a considerable range of sclerite sizes and shapes, can occur within a single sample (e.g., Müller and Hinz-Schallreuter, 1993, table 1) demonstrates that making the connection between a particular type of isolated sclerite and a whole-body taxon can be very difficult in many cases. This may have led to assigning sclerites with different patterns to a single form taxon, such as Hadimopanella oezgueli, which includes sclerites with multiple circles of nodes and others with just one circle of nodes (cf. van de Boogaard, 1983, figs. 3a–e, 4b–e vs. figs. 3f and 4a). This becomes evident in the Chinese Guanshan Lagerstätte (Hu et al., 2012), which has one taxon exclusively covered in sclerites with several circles of nodes (Wudingscolex sapushanensis) and another one having only sclerites with a single circle of nodes (Yunnanoscolex magnus). In this study we focus on macroscopic compression fossils from Australia and Spain, with occasional reference to isolated sclerites

and phosphatized microscopic scleritome fragments in the context of palaeoscolecid taxonomy. Here we document new material from the Cambrian Emu Bay Shale (South Australia) and Murero (Zaragoza, NE Spain) KonservatLagerstätten, preserved as macroscopic compression fossils with mineralised sclerites. We revise Palaeoscolex antiquus Glaessner, 1979, from the Emu Bay Shale based on new collections that elucidate details of its soft anatomy and sclerite morphology, and reassign it to Wronascolex Ivantsov and Zhuravlev, 2005. Previously documented palaeoscolecids from the Murero Formation include a large (c. 8 cm long) individual described by Conway Morris and Robison (1986) and a small specimen (c. 3 cm long) by Gámez Vintaned (1995), both being assigned to Palaeoscolex cf. P. ratcliffei Robison, 1969. Here we present two new palaeoscolecid specimens from that same locality and transfer them to Wronascolex. 2. Localities 2.1. Australia The Emu Bay Shale Konservat-Lagerstätte is located at Big Gully, about 10 km NNW of the town of Kingscote on the north coast of Kangaroo Island, South Australia. The lowest unit of the Cambrian succession at Big Gully is the White Point Conglomerate, up to 575 m thick and characterized by cobble to boulder polymict conglomerate with minor mudstones and sandstones (Gehling et al., 2011). The Marsden Sandstone, including the Rouge Mudstone

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Fig. 2. Simplified geological map of the early–middle Cambrian Murero locality. Asterisk indicates where Wronascolex? spec. 1 (MPZ 96/223) was found. Modified from García-Bellido et al. (2011).

Member at its base, overlies this unit conformably. The overlying Emu Bay Shale is typically 50–60 m thick, and starts with a thin basal conglomerate, regarded as a sequence boundary, followed by a succession of mudstones, siltstones and sandstones. The Lagerstätte occurs in the basal 10 m of the Emu Bay Shale, within dark grey to black, laminated, micaceous mudstones that are interbedded with thin, structureless, fine sandstones up to 20 cm thick. The upper 30 m comprises largely interbedded mudstones and thin-bedded reddish brown micaceous sandstones, with abundant arthropod tracks towards the top of the unit. The basal sandstones of the Boxing Bay Formation rest conformably on the Emu Bay Shale in coastal sections, but further inland the contact is channelled. Soft-bodied fossils were collected from the shoreline outcrop between the 1960s and 1990s, while a new excavation (Buck Quarry) that started in 2007 has focused on fossiliferous levels some 400 m from the coast (Fig. 1).

To date, the Emu Bay Shale biota comprises over 50 species, including trilobites with soft parts, a large variety of non-biomineralised arthropods (anomalocaridids, megacheirans, concilitergans, nektaspids, bivalved arthropods), a lobopodian, a vetulicolian, palaeoscolecids, a priapulid-like form, a polychaete, brachiopods, molluscs, chancelloriids, sponges and a number of incertae sedis (Glaessner, 1979; Conway Morris and Jenkins, 1985; Bengtson et al., 1990; McHenry and Yates, 1993; Nedin, 1995a, 1995b; Briggs and Nedin, 1997; Nedin, 1999; Dzik, 2004; Paterson and Jago, 2006; Paterson et al., 2008; García-Bellido et al., 2009; Paterson et al., 2010, 2011; Edgecombe et al., 2011; Lee et al., 2011; Paterson et al., 2012). The Lagerstätte is interpreted as having been deposited in a localised, deep water mini-basin on the inner shelf, with fluctuating oxic to anoxic conditions on the seafloor below an otherwise oxygenated water column (Gehling et al., 2011; Hall et al., 2011; McKirdy et al., 2011).

D.C. García-Bellido et al. / Gondwana Research 24 (2013) 780–795 Table 1 Australian and Spanish palaeoscolecid dimensions (in mm). Abbreviations: t = talus; T1 = plates (80–100 μm); T2 = platelets (30–50 μm); T3 = microplates (15–20 μm); wcp = wave-cut platform. Specimen

Max length

Wronascolex antiquus SAM P14795 >36 SAM P14809 >152 SAM P14816 >50 SAM P14818 >37 SAM P14883 23 SAM P14941 >55 SAM P14999 >110 SAM P15159 >146 SAM P15160 >70 SAM P15246 >180 SAM P15281 >140 SAM P15416 21 SAM P21010 Hol >35 SAM P21011 Par >23 SAM P45224 375

Max width

Min width

Rings/mm

Sclerites

Level

3.5 12.0 8.3 3.5 1.0 5.0 5.0 11.4 6.5 7.0 9.0 1.0 8.0 2.0 12.0

3.5 12 6.4 1.0 1.0 5.0 5.0 5.4 6.5 7.0 8.0 1.0 8.0 2.0 12.5

3 1 1 2.5 – 1.3 2 1.7 2 1.7 1.5 3.8 1 2 0.7–1

– – – – – T2 T2 – – T1 – – T1, T2 – –

12.5 11.7 9.8 11.6 11.8 t 11.7 11.6 11.6 11.7 11.4 9.0 wcp wcp 11.0

Wronascolex iacoborum sp. nov. SAM P43746 >55 2.0

1.0

Wronascolex? spec. 1 MPZ 96/223 220

11.0

10.0

Wronascolex? spec. 2 A.P.-1971 30 + 39

10.5

8.0

4.5

T1,T2,T3

10.5

0.7–0.9

T1, T2

–

2.5

T1, T2

–

2.2. Spain The Murero Lagerstätte is the only Burgess Shale-type deposit so far described from Spain. It is located in the Rambla de Valdemiedes (Valdemiedes Gully), north of the town of Murero (Fig. 2), about 80 km southwest of Zaragoza (NE Spain), in the western branch of the Iberian Chains. A 210 m-thick succession is exposed along the Rambla de Valdemiedes, mostly composed of lutites, with occasional levels of very fine-grained sandstones, and some minor interbedded dolostones and dolomitic nodules (Liñán et al., 2008). The Murero succession includes most of the Mesones Group (subdivided into

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the Valdemiedes, Mansilla, and Murero formations) and the base of the Acón Group (lowest part of the Borobia Formation), with ages ranging from upper Bilbilian (upper part of Cambrian Stage 4) to lower Languedocian (=Cambrian Stage 5 and part of the Drumian Stage). The specimens studied here correspond to the Murero Formation, Cambrian Series 3, Stage 5 (Regional Bilbilian–Leonian Stages), thought to have been deposited in a relatively deep sub-littoral and low-energy environment (Liñán et al., 2008). The Murero succession includes about 50 trilobite species, brachiopods with preserved pedicles, articulated sponges, bradoriids and echinoderms (cinctans, eocrinoids, and edrioasteroids), plus palaeoscolecids, a lobopodian, filamentous algae and ichnofossils (Gámez Vintaned, 1995; Gámez Vintaned and Mayoral Alfaro, 1995; Liñán and Mergl, 2001; Gozalo et al., 2004; García-Bellido et al., 2007; Liñán et al., 2008; Zamora et al., 2009; Zamora, 2010; Zamora and Álvaro, 2010; Gámez Vintaned et al., 2011; García-Bellido et al., 2011). 3. Terminology and methods Morphological terminology applied to the description of palaeoscolecid body annulation and sclerites follows Müller and Hinz-Schallreuter (1993). Terminology applied to the proboscis follows Conway Morris (1977). Light photography of specimens used a Canon EOS 5D digital camera with either a Canon MP-E 65 mm 1–5× macro lens, a Canon CompactMacro EF 50 mm or a Tamron SP Di 90 mm. Scanning electron microscopy was done on carbon coated original specimens at 20 kV with a JEOL JSM-6400 (Fig. 5), and on uncoated specimens in low vacuum at 26 kV with a FEI Inspect-S ESEM equipped with backscatter detector and energy dispersive X-ray spectroscopy-SEM EDS (Figs. 6, 8, 9 and Fig. A1). 4. Systematic palaeontology Class Palaeoscolecida Conway Morris and Robison, 1986 Family Palaeoscolecidae Whittard, 1953 Wronascolex Ivantsov and Zhuravlev, 2005 Emended diagnosis. Long, slender cylindrical worms, covered by annulated cuticle, each annulation with 1–4 rows of Hadimopanellatype circular phosphatic sclerites: round or slightly ovate discs with an

Table 2 Dimensions of Cambrian palaeoscolecid compression-fossil taxa with Hadimopanella sclerites. All dimensions in mm, except sclerite sizes which are in μm. Note that ‘plates around ring’ refers to the number of plates making a single band around a complete annulation. Abbreviations: c = circular; e = elongate; I. = Ivantsov; W.= Wrona; Z. = Zhuravlev; ∅ = diameter; *= central node occasionally present. Taxon

References

Specs. Max length

Max Rings/mm Plates around Plate ∅ Plate rows/ Plate width ring ring nodes

Plate Platelet Microplate shape ∅ ∅

Wronascolex antiquus

Glaessner (1979), this publication This publication

>100

375

13

0.7–3.8

70–100

80–150

1

3–6

c

40–50

–

>55

2

4.5

60

40–50

2

5

c

25

15

220 11 30 + 39 10.5 111 4

0.7–0.9 2.5 1.4–1.8

90–100 90–100 60–70

80–100 100 70–80

4 3–4 4 (2, 6)

? ? ?

c c c

30 30–50 40–60

– – –

43

1.2

5.5–8.3

50–60

40–80

4

5–8 (+1*)

c

30–40

+

40

3

5.5–6.2

40

30–80

2

4–10 (+1*) c

–

–

49 81

1.5 7

8–10 2.5

60–80 70

25 × 40 80–100

2 2

7–11 ?

e c

25 –

+ –

32.5 14 100 80–100

2.6 1.5 8 2

8 6–8 2.5 5

50–75 40–50 100–120 40–50

90 20–40 40–45 30–45

2 2–3 3–5 2,4

? ? 2–6 0 (+1)

c c c c

– – – 10

– – – –

30

1–2

3–5

90–100

15–20

7–8

4

c

–

–

50

6

2–8

?

15–20

?

4

c

–

–

Wronascolex iacoborum sp. nov. Wronascolex? spec. 1 Wronascolex? spec. 2 Wronascolex? ratcliffei

1

This publication 1 This publication 1 Robison (1969), 1 this publication Wronascolex lubovae I. and W. (2004), 4 I. and Z. (2005) Wronascolex spinosus I. and W. (2004), 3 I. and Z. (2005) Palaeoscolex piscatorum Whittard (1953) 4 Palaeoscolex cf. P. ratcliffei Conway Morris and 1 Robison (1986) Palaeoscolex cf. P. ratcliffei Gámez Vintaned (1995) 1 Palaeoscolex huainanensis Lin (1995) 1 Yunnanoscolex magnus Hu et al. (2012) 50 Mafangscolex sinensis Hou and Sun (1988), >100 Hu (2005) Maotianshania cylindrica Sun and Hou (1987), >100 Hu (2005) Paramaotianshania zijunia Hu et al. (2012) 15

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ornamented upper surface of a single circle of 4–10 nodes and an occasional central node. Oral end with spiny introvert. Gut simple and straight. Type species. Palaeoscolex lubovae Ivantsov and Wrona, 2004. Other species. P. ratcliffei Robison, 1969; P. antiquus Glaessner, 1979; Palaeoscolex spinosus Ivantsov and Wrona, 2004; Palaeoscolex sp. Ivantsov and Wrona, 2004. Discussion. It has become apparent, through the SEM study of compressed palaeoscolecid macrofossils, that Palaeoscolex has become a ‘wastebasket’ genus, including taxa with a variety of sclerite morphologies. We agree with Ivantsov and Zhuravlev (2005) that, in the absence of detailed sclerite information obtained through SEM, some Cambrian Palaeoscolex species described to date are nomina dubia (e.g., Palaeoscolex cf. P. ratcliffei Conway Morris and Robison, 1986, Palaeoscolex cf. P. ratcliffei Gámez Vintaned, 1995 and Palaeoscolex huainanensis Lin, 1995). Here we argue towards reserving the genus Palaeoscolex exclusively for palaeoscolecids which preserve Milaculum-type plates of the kind shown in the Ordovician type species, Palaeoscolex piscatorum: elongated sclerites with nodes disposed parallel or subparallel to the sagittal axis (Conway Morris, 1997). Thus, we include in Wronascolex all of the macroscopic palaeoscolecid fossils known to have Hadimopanella sclerites with 3 to 10 nodes arranged in a single circle and with or without a central node of the same size as the others, like H. oezgueli described from the Cambrian of Iran (Wrona and Hamdi, 2001, pls. 2, 3) and some specimens from the Cambrian of Spain (van de Boogaard, 1983, figs. 3f, 4a). This concept of the genus could encompass the recently proposed Yunnanoscolex Hu et al., 2012, the type species of which, Y. magnus Hu et al., 2012, was noted to have similar plates to Wronascolex spinosus but argued by the authors to differ in quincunxially arranged plates and central nodes, as well as by the shape of the ventral protuberances. The latter refer to rounded protuberances ca. 200–300 μm in diameter that are irregularly present on the ventral side of posterior annulations. The plates of Y. magnus Hu et al., 2012, do not have a strictly quincunxial arrangement (Hu et al., 2012, fig. 2D, F), and we do not identify a clear-cut difference from the variability in plate arrangements observed across species of Wronascolex. However, the presence of ventral protuberances has not been recognized in Wronascolex, which may validate the generic separation of Yunnanoscolex, though they are present in Wudingscolex Hu et al., 2012. We distinguish Wronascolex from macrofossil taxa like Guanduscolex (Hu et al., 2008; pl. I, figs. 6–10) and Wudingscolex (Hu et al., 2012; fig. 3D–F) that have Hadimopanella-like sclerites that exhibit several circles of nodes, similar to the holotype of Hadimopanella knappologicum (Bengtson, 1977, text—fig. 2) or specimens of H. oezgueli from the Cambrian of Spain (van de Boogaard, 1983, figs. 3a–e). Mafangscolex sinensis (Hou and Sun, 1988), a type species that was previously assigned to Palaeoscolex, has circular sclerites, but these are flat and have a single small node in the centre, plus they show a continuum in size between the largest (45–50 μm) and the smallest (~8 μm) sclerites, and thus lack distinct plates, platelets and microplates (Hu, 2005; pl. 17, figs. 5, 9). Maotianshania Sun and Hou, 1987, and Paramaotianshania Hu et al., 2012, despite having body sizes similar to the smallest Wronascolex specimens (Tables 1, 2), have minute Hadimopanella sclerites (15–20 μm), intermediate in size between Wronascolex platelets and microplates. At least in the case of Maotianshania, although widely classified as a palaeoscolecid, an ornamentation of polymorphic tessellating plates that Harvey et al. (2010) cited as diagnostic of “palaeoscolecids sensu stricto” has not been confirmed; Maotianshania

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resolves in different positions in the priapulid stem group in phylogenetic analyses (Harvey et al., 2010; Wills et al., 2012), but is consistently not closely related to Palaeoscolex (by definition, the proxy for palaeoscolecids sensu stricto). A number of Orsten-type fossils also preserve Hadimopanella (or similar) sclerites on their cuticles, but are not considered for synonymy due to the reasons discussed above. Among these are: Austroscolex spatiolatus Müller and Hinz-Schallreuter, 1993 (text—fig. 4F, H, K), with two rows of plates per annulation and 4 nodes per sclerite; Corallioscolex gravius Müller and Hinz-Schallreuter, 1993 (text—fig. 5D, F), with 2–3 rows of plates, each with 6–7 nodes; Rhomboscolex chaoticus Müller and Hinz-Schallreuter, 1993 (fig. 9B, C, G, H), with two rows of 4 to 9-node sclerites; Schistoscolex angustosquamatus Müller and Hinz-Schallreuter, 1993 (text—fig. 10G), with two rows and 1–4 nodes per sclerite; Thoracoscolex armatus Müller and Hinz-Schallreuter, 1993 (text—fig. 15H), with two rows of sclerites, each with 2–5 nodes; Pantoioscolex oleschinskii Müller and Hinz-Schallreuter, 1993 (fig. 16C), with an indeterminate number of rows per annulation and sclerites with 4–6 nodes, all from the Monastery Creek Phosphorite Member (Beetle Creek Formation), Queensland, Australia. Other examples in the same category are: Corallioscolex labyrinthus (Ivantsov and Wrona, 2004), with two rows of 7 to 10-node sclerites (Ivantsov and Wrona, 2004, figs. 9, 10; Ivantsov and Zhuravlev, 2005, pl. XX, fig. 3a–b) and other cuticle fragments (Ivantsov and Wrona, 2004, figs. 7, 8; Ivantsov and Zhuravlev, 2005, pl. XIX, fig. 5) from the early Cambrian Sinsk locality in eastern Siberia (Russia); and cuticle fragments from the lower Cambrian Mernmerna Formation in the Flinders Ranges of South Australia that possess Hadimopanella sclerites referable to two form species on a single scleritome (Topper et al., 2010). Cuticle fragments from the Bitiao Formation (Furongian) of Hunan (China) assigned to Schistoscolex hunanensis Duan et al., 2012 were illustrated presenting annulations with two rows of round to polygonal closely-packed sclerites with irregular-sized nodes, a few of them with 3–4 subequal nodes (Duan et al., 2012; fig. 3K). The transfer of several Cambrian species from Palaeoscolex to Wronascolex results in the latter being a lower and middle Cambrian genus with a widespread geographic distribution, and greatly reduces the stratigraphic range of Palaeoscolex, which is increasingly seen as an Ordovician genus. Distribution. Occurrences of Wronascolex from Siberia, Australia and China are considered Cambrian Series 2, Stage 4 in age. Wronascolex lobovae, W. spinosus and W. sp. from the Sinsk Formation of Siberia occur within the Bergeroniellus gurarii Biozone of the mid Botoman (Ivantsov and Wrona, 2004). Wronascolex antiquus and Wronascolex iacoborum sp. nov. from the Emu Bay Shale of South Australia occur within the Pararaia janeae trilobite Zone that corresponds to the early-mid Canglangpuan of China and mid–late Botoman of Siberia (Paterson et al., 2008) and is possibly coeval with the Sinsk biota (cf. Paterson and Brock, 2007, fig. 5). W. spinosus? from the Guanshan Biota of the Wulongqing Formation of Huize, Yunnan, China (Liu et al., 2012) occurs within the Palaeolenus and Megapalaeolenus zones (middle–upper Canglangpuian Stage; Zhang et al., 2008; Hu et al., 2010) and is therefore slightly younger than the Siberian and Australian occurrences (Paterson and Brock, 2007; Yuan et al., 2011; Geyer and Peel, 2011). The youngest occurrence is represented by specimens of Wronascolex? from the Murero Formation (Spain), representing a Caesaraugustan age (mid–late Cambrian Stage 5—Drumian) (Liñán et al., 2008). Wronascolex antiquus (Glaessner, 1979) (Figs. 3–5; Tables 1, 2) 1979. Palaeoscolex antiquus sp. nov., Glaessner, pp. 25–27, fig. 3.

Fig. 3. Wronascolex antiquus (Glaessner, 1979); Buck Quarry, Emu Bay Shale (South Australia), Cambrian Series 2, Stage 4. A, SAM P45224a, part, largest complete specimen (375 mm long); B–C, SAM P45227, under water; B, specimen showing annulated surface with sclerites, C, detail of sclerites, where larger plates have been lost. D–E, SAM P15159a, low-angle light from left; D, possible moult with break at midlength, E, detail of wrinkle in cuticle; F, SAM P151415, smallest complete specimen (21 mm long). Scale bars, 10 mm (A, D), 2 mm (B, E, F), 1 mm (C).

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Fig. 5. Wronascolex antiquus (Glaessner, 1979); Buck Quarry, Emu Bay Shale (South Australia), Cambrian Series 2, Stage 4. A–F, H: SAM P43742; G: SAM P43741; SEM images; A, overall view of sclerite pattern of one row of large plates per annulation; B, detail of pattern with row of large plates interspersed with several rows of platelets; C, group of three upward facing platelets (bottom right one with 3 nodes), beside three 5-node negative impressions (upper right corner); D, group of several downward-facing platelets and negative impressions; E, 5-node Hadimopanella platelet with internodal groove; F, 5-node Hadimopanella platelet; G, 4-node Hadimopanella platelet with internodal groove; G, 6-node Hadimopanella platelet with internodal groove. Scale bars, 1 mm (A), 500 μm (B), 50 μm (C–F).

2008. Palaeoscolex antiquus Glaessner; Paterson et al., fig. 2F. Emended diagnosis. Worms 20–370 mm in length and 1–12 mm wide in compressed specimens. One to four annulations per millimetre, each with one row of large Hadimopanella-type sclerites (plates) and several rows of platelets. Sclerites with 3–6 nodes and without a central node. Spiny proboscis and 1–3 large terminal hooks present. Material. Over one hundred specimens, most with part and counterpart, from Buck Quarry and shore outcrop, Emu Bay Shale, Kangaroo Island.

Description. The fossils are found as flat compressions, showing either the top or bottom layers of the original cylindrical body, and only occasionally preserved in their entire length. One or both ends curved or coiled. The uncoiled length of complete specimens ranges from c. 20 mm (Fig. 3F) to more than 370 mm (Fig. 3A), with width between 1 mm in the smallest and 12 mm in the largest (Table 1). The mouth is in the distal end of a retractable proboscis (Fig. 4A, B). In specimens with everted proboscis (Fig. 4B; “stage 4” sensu Conway Morris, 1977, p. 23), it appears to be three-zoned, with 11 rows of scalids in Zone I

Fig. 4. Wronascolex antiquus (Glaessner, 1979); Buck Quarry, Emu Bay Shale (South Australia), Cambrian Series 2, Stage 4. A, SAM P45919a, proboscis in eversion stages 1–2, with outline of retracted introvert (arrow); B, SAM P15051a, proboscis in eversion “stage 4”; C–D, SAM P45340, specimen with two hooks in posterior end, D, detail of the hooks; E, SAM P45225, specimen with one hook in posterior end; F, SAM P47066, specimen with three hooks; G, SAM P45340a, specimen with two hooks (part); H, P45340b, specimen with two hooks (counterpart); I–J, SAM P43740, specimen with gut; J, detail of phosphatized gut; K, SAM P45218a, specimen with phosphatized gut. Scale bars, 0.5 mm (D), 1 mm (A, F), 2 mm (C, E, G–H, J), 5 mm (B, I, K).

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Fig. 6. Wronascolex iacoborum sp. nov.; Buck Quarry, Emu Bay Shale (South Australia), Cambrian Series 2, Stage 4. A–F, SAM P43746. A, overall image of whole specimen; B, detail of sclerite rows of framed area in A; C, detail of posterior end with sclerites; D, detail of annulation pattern (in central right area of B) with alternating rows of large (vertical arrow) and medium (horizontal arrow) Hadimopanella sclerites, and a few isolated small (tilted arrow) sclerites; E, detail of 5-pointed Hadimopanella sclerite; F, detail of deformed Hadimopanella sclerite. B–F: backscattered SEM images. Scale bars, 5 mm (A), 500 μm (B–C), 30 μm (D), 15 μm (E, F).

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Fig. 7. Wronascolex? spec. 1; Rambla de Valdemiedes, Murero (NE Spain), Murero Formation, Cambrian Series 3, Stage 5—Drumian (regional Caesaraugustan Stage). A–F, MPZ 96/ 223. A, detail of anterior half; B, camera lucida drawing of anterior half (black frame indicates area in Fig. A1–B); C, Camera lucida of posterior half; D, detail of posterior half; E, image of complete specimen; F, oral area with spines (arrows), under water. Scale bars, 10 mm (A–D), 50 mm (E), 3 mm (F). Abbreviations: a, anus; an, annulus; blc, bottom layer of cuticle; iag, inter-annular groove; ol, overlap of grooves; osp; oral spines; p, proboscis.

(proximal limit indicated by arrow in Fig. 4B) and an indeterminate number in zones II and III, which are partially imprinted by annulation of underlying trunk. In specimens with almost fully-retracted proboscis (between stages 1 and 2 of Conway Morris, 1977), only a ring of approximately 30 scalids can be recognized (Fig. 4A), together with the curved outline or retracted introvert (arrow). The anus is located at the end of what is usually the coiled end of the specimen, and it occasionally shows 1, 2 or 3 large hooks (Fig. 4E, G–H, C–D and F, respectively). These hooks are about 0.5 mm wide at the base, and 2 mm long. The body is annulated along its whole length, and covered in rows of circular sclerites (Fig. 3B–C) parallel to the annulations. The Hadimopanella-type sclerites are composed of calcium phosphate, as indicated by EDS semi-quantitative analysis, and have two sizes: large ones (plates), disposed in one row per annulation, are 80–150 μm

in diameter (Fig. 5A–B). There are about 50 plates per annulation in the exposed side, probably about one hundred around the whole annulation. Platelets are 40–50 μm in diameter (Fig. 5C–H), and arranged in 6–8 rows per annulation, with 70–80 sclerites per row (Fig. 3C), which would make over 1000 small sclerites for each complete annulation. These sclerites show evidence of shearing, truncating the tips of the nodes. All the plates appear truncated, while the best-preserved platelets usually have 5 nodes (Fig. 5E, F), but also occur as 3 (Fig. 5C, bottom right), 4 (Fig. 5G) and 6 nodes (Fig. 5H, where the bottom-left node is lost). Some platelets are preserved inverted, occasionally leaving behind a 5-node negative impression (Fig. 5C, D). Others present well-defined internodal grooves (Fig. 5E, H), but no central nodes have been recognized. Regarding internal structures, a few specimens preserve an elongated gut, which is

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Fig. 8. Wronascolex? spec. 2; Rambla de Valdemiedes, Murero (NE Spain), Murero Formation, Cambrian Series 3, Stage 5—Drumian (regional Caesaraugustan Stage). A–F, A.P.-1971. A, complete specimen (symbol indicates deformation ellipse and principal compression axis); B, Posterior end, low angle light; C, SEM image of posterior end; D, SEM image of two different layers, with plates and platelets; E, SEM image of annulations with plates; F, SEM detail of oval-shaped distorted plates; G, SEM detail of a recrystallized plate; H, SEM detail of three recrystallized platelets. A, B: low-angle light, C–H: backscattered SEM images. Scale bars, 10 mm (A), 5 mm (B), 1 mm (C), 500 μm (D, F), 200 μm (E), 50 μm (F, G).

about one third to one fourth the width of the body (Fig. 4I–K). The preserved part of the gut does not connect to either end of the animal and can only be recognized in a fifth of its total length, probably corresponding to the midgut. EDS semi-quantitative analysis of this structure indicates that it is preserved as calcium phosphate, and constitutes a band with a slight relief compared with the rest of the compressed fossil. One specimen (SAM P15159) shows a series of unique characteristics regarding its cuticle (Fig. 3D): it is broken in the middle, has a

wrinkle extending across the width of the body (Fig. 3E), and is strongly compressed, with weakly expressed annulations (all but a few sclerites are present, and they only become apparent under SEM-EDS), lacking the ridge-valley appearance of contracted specimens. These features are consistent with being an empty exuvia (see discussion below). Discussion. This palaeoscolecid reaches the largest size known for the group to date, being more than 37 cm in length and 13 mm wide, only partially rivalled by Wronascolex? specimen 1 from Spain, which is 22 cm long and 11 mm wide (Table 2). However, most of its

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Fig. 9. A–G, Wronascolex? ratcliffei (Robison, 1969); Spence Shale, Langston Formation, Calls Fort (Utah), Cambrian Series 3, Stage 5: KUMIP 204390. H–J, indeterminate palaeoscolecid, Lampazar Formation, Sierra de Cajas (Jujuy, Argentina), Furongian, Cambrian: PIL 14.548. A, overall view under water, with polarized light (arrows point at annulation boundaries, frames indicate areas in Fig. 9C–E); B, overall view, dry with angled light to show reflective digestive tract; C, detail of inner part of the coil with row of single plates dividing into two rows (horizontal arrows), with interspersed plates and platelets (tilted arrows); D, detail of area with three rows of plates; E, detail of aboral area with closely spaced sets of three rows of plates; F, recrystallized smooth plates (73–79 μm across) and part of the preserved gut (white area in top right corner); G, SEM-EDS elemental mapping of the area in F, notice the enhanced content in Fe, O and Mg for the sclerites and gut trace and the enhanced Al, K and Si of the surrounding matrix. H, detail of the putative anterior end of the specimen, showing dark bands of iron oxide; I, detail of a segment bound by two interannulation ridges, showing the pattern of the cuticle, a few gypsum micro-rosettes and some iron oxide (white); J, detail of the tessellate pattern, larger tessellae close to the edges and smaller in the centre of the ring; notice the faint ridge across the lower end of the image. C–F, I–J: backscattered SEM images. Scale bars, 50 μm (J), 200 μm (F, G, I), 500 μm (C, D), 1 mm (E, H), 5 mm (A, B).

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features fall well within the characteristics of the genus: basically Hadimopanella-type sclerites on its cuticle arranged in rings with one or more rows of plates. W. antiquus is the only species in the genus that has exclusively one row of plates, while W. spinosus and W. iacoborum sp. nov. have two, the two Spanish Wronascolex? specimens have three to four and W. lubovae has four (cf. Ivantsov and Zhuravlev, 2005). The number of plates in a row around a complete ring falls in the genus range (40–110), but in the higher end (70–100). Sclerite sizes in this species are also within the upper limits of other Wronascolex plates (80–100 μm) and platelets (40–50 μm), but can reach up to 150 μm in diameter; these approach the isolated sclerites of H. oezgueli Gedik, 1977 from Iran (Wrona and Hamdi, 2001) and two of the specimens from the Láncara Formation in northwestern Spain (van de Boogaard, 1983, figs. 3f, 4a). Other palaeoscolecids also preserve terminal hooks at the aboral end, but those tend to be considerably smaller: Y. magnus has two hooks, 0.5 mm long and 0.2 mm wide at the base (Hu et al., 2012, fig. 2A, B), while Maotianshania cylindrica has two 0.5 mm-long hooks (cf. Hu, 2005) and M. sinensis likewise has two distal hooks (Hu, 2005). Undisputable empty palaeoscolecid moults have not been recognized before, but Orsten-type material from Queensland does show a double layer of sclerite-bearing cuticle (Müller and Hinz-Schallreuter, 1993, text—figs. 12B, 14C) in specimens that may represent individuals that were about to undergo moulting. The specimen of W. antiquus described above as either representing an exuvia or a decayed carcass (Fig. 3D, E) has its trunk torn and separated near its midlength (Fig. 3D), but this rupture is unlikely to mark the position of an exuvial line, based on comparison with exuviae of priapulids. The extant Priapulus caudatus moults by ecdysial rupture at the base of the introvert (Lang, 1948; Carlisle, 1959) rather than further back on the trunk. The exuvia of Priapulus is wrinkled and folded (Lang, 1948, pl. 2, fig. 4), analogous to the possible Wronascolex moult.

Occurrence. Shore outcrop and Buck Quarry, Emu Bay Shale, Cambrian Series 2, Stage 4, Big Gully, Kangaroo Island, South Australia. Wronascolex iacoborum sp. nov. (Fig. 6; Tables 1, 2) Type material. Holotype: SAM P43746 (Fig. 6), one specimen, with part and counterpart from level 10.5, Buck Quarry, Emu Bay Shale, Kangaroo Island. Etymology. Iacobus, Latin for James; named after James B. Jago (University of South Australia) and James G. Gehling (South Australian Museum). Diagnosis. Very thin and elongated worm, with four to five annulations per millimetre, each with two rows of Hadimopanella-type sclerites. These plates are small (40–50 μm). Platelets and microplates also present. Sclerites with 5 nodes and without a central node. Description. The holotype is almost complete with its posterior end coiled, and only lacking the oral end. The preserved length is 55 mm and its width is constant at about 2 mm (Table 1), which confers a length to width ratio of more than 25:1. The body is annulated along its whole length, with about 4–5 annulations per mm, and each annulation bearing two rows of large circular sclerites (Fig. 6B–C). The sclerites have three sizes, disposed in alternating rows (Fig. 6B, D): plates of 40–50 μm in diameter (Fig. 5D–F), platelets of about 25 μm, and microplates of 15 μm. There are about 50 large Hadimopanella-type sclerites per row in the exposed side, probably about one hundred around the whole annulation. Most sclerites present sheared nodes (Fig. 6F), but some plates still preserve 5 nodes (Fig. 6E). Discussion. Although this taxon overlaps in size with the smaller specimens of W. antiquus (Tables 1, 2), it shows up to 5 annulations per millimetre, compared with the 2.5–3.8 of the latter. It has two rows of sclerites per annulation instead of one, and its sclerites are smaller, with plates 40–50 μm in diameter compared with the 80–150 μm of W. antiquus, and platelets about half the size of those in W. antiquus. Another difference is the presence of microplates,

Fig. 10. Palaeogeographic distribution of the most relevant palaeoscolecids and isolated sclerites discussed in this study. Early Cambrian palaeogeographic reconstruction modified from McKerrow et al. (1992).

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which have not been recognized in W. antiquus. Although it overlaps in overall body size and plate size with the Siberian species (W. lobovae and W. spinosus), it differs in having fewer annulations per millimetre (6–8 in the latter), sclerites at the lower end of the Siberian range and not showing a central node on its sclerites. Occurrence. Buck Quarry, Emu Bay Shale, Cambrian Series 2, Stage 4, Big Gully, Kangaroo Island, South Australia. Wronascolex? spec. 1 (Fig. 7; Fig. A1; Tables 1, 2) Material. Single specimen, without counterpart (MPZ 96/223), Murero Formation, Rambla de Valdemiedes, Murero, Spain. Description. The fossil is preserved as a flat compression, slightly darker than the surrounding matrix. The total extended length of the specimen is 220 mm, with a maximum width of 11 mm (Table 1 and Fig. 7A–E) and it is found partially coiled. At the anterior tip there are at least seven spines (Fig. 7F), 1 to 2 mm long, that surround what can be considered to be the mouth (Fig. 7B, osp, and F). The mouth is in the distal end of a 33 mm-long unarmed extended proboscis (Fig. 7B), “stage 4” (sensu Conway Morris, 1977), which starts in a constriction that separates it from the rest of the body. Along the body are numerous parallel interannular grooves and pits left by sclerites, these structures are not present on the proboscis. In areas where there are no discernible grooves, the pits left by the lost sclerites still follow parallel lines. In the other areas the pits are located adjacent to the interannular grooves. Due to compression, the cuticle now shows longitudinal wrinkles along the whole body. In some places the upper layer of the cuticle is preserved, covering the lower layer, as seen in the specimen described by Conway Morris and Robison (1986). This overlapping produces, after compression, the interannular grooves of one layer to be printed on the other. The anus is defined by convergent wrinkles, and is located in a subterminal position. This is possibly due to burial orientation rather than being its original position in life. The annulation is very faint (Fig. 7B, C and Fig. A1-A, arrows) and the sclerite pattern is almost only discernible by the sclerite impressions preserved in the form of pits (Fig. A1-A, B), but it allows recognizing four rows of plates. Less than 2% of the original sclerites remain (light circular structures in Fig. A1-C, D), but these sclerites are circular and show two sizes (Fig. A1-D): plates are about 80–100 μm in diameter, while platelets are about 30 μm. The preserved sclerites have been recrystallized (Fig. A1-D) and no detailed structures, such as nodes, are recognizable. Discussion. Although the diagnostic sclerite nodes are not preserved, this fossil is tentatively assigned to Wronascolex based on the overall body size, annulation, and particularly the size and circular shape of its sclerites. The apical spines are similar to those observed in the tip of the proboscis of the priapulid Fieldia lanceolata from the Burgess Shale (Conway Morris, 1977; pl. 27, fig. 2), and do not show the relief of those in W. antiquus (Fig. 4A). The extension of the proboscis is similar to Phase 2 described for the priapulid Louisella pedunculata (Conway Morris, 1977). This phase, with spines parallel to the longitudinal axis of the body, is the most common in this species (Conway Morris, 1977). Neither the gut nor any other internal structures can be recognized, which suggests that some degree of decay had taken place, but that it did not significantly affect the more recalcitrant cuticle. The general dimensions of the specimen and the preserved diagnostic characters (number of annulations per mm and size of sclerites) place this specimen close to W. antiquus (Glaessner, 1979), but the Murero worm presents four rows of plates, whereas W. antiquus has only one. So, in the lack of evidence from the node pattern on the sclerites, and despite having sclerite size and shape compatible with Hadimopanella, we leave this taxon under open nomenclature. Occurrence. Talus slope of the Murero Formation, Caesaraugustan Stage (Cambrian Series 3, Stage 5—Drumian), at Rambla de Valdemiedes, Murero (NE Spain). Wronascolex? spec. 2 (Fig. 8; Tables 1, 2) Material. Incomplete single specimen, without counterpart (A.P.-1971) from the Rambla de Valdemiedes, Murero, Spain.

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Description. The specimen is coiled and, due to rock breakage, is composed of two fragments 30 and 39 mm long. The maximum width is 1 cm (Fig. 8A). A reconstruction of the inner coil of the specimen would add 50 mm between fragments. This would make the specimen at least 120 mm long, although there is an unknown length lost on the other tip. The fossil is preserved three-dimensionally (i.e., the annulations show considerable relief), and the typical palaeoscolecid coiling suggests that the preserved end corresponds to the anus. The specimen preserves the original sclerites along the whole extension of the body (Fig. 8D–F). The sclerites are circular, or slightly oval due to tectonic deformation (principal compression axis indicated in Fig. 8A). They occur in two sizes (Table 2): plates are about 100 μm in diameter (Fig. 8G), 80 by 120 μm when oval, while platelets are about 30 μm in diameter (Fig. 8H). Recrystallization of the sclerites has obscured the surface pattern (Fig. 8G, H). Discussion. The specimen does not preserve any internal structures. This is possibly due not only to taphonomic factors, but also to the presence of a very contracted cuticle, which shows a significant (ridge-and-valley) three-dimensional arrangement (Fig. 8B). The width, number of plates around each annulation and number of plate rows, as well as the plate and platelet diameter, is almost identical with Wronascolex? spec. 1. The only difference is the number of annulations per millimetre and the apparent density of plates per annulation, but this could be due to the highly contracted cuticle mentioned above. An open nomenclature assignment to Wronascolex is employed for the same reasons as noted above for the other Murero specimen. Occurrence. This specimen was collected in 1971 by Mr. Antonio Pineda in loose scree at the Rambla de Valdemiedes. It is impossible to assign to a particular level, but the lithology is very similar to that of the local Murero Formation, Caesaraugustan Stage (Cambrian Series 3, Stage 5—Drumian). Wronascolex? ratcliffei (Robison, 1969) (Fig. 9A–G) 1969. Palaeoscolex ratcliffei Robison, pp. 1171–1172, pl. 138, figs. 1–2. 1991. Palaeoscolex ratcliffei Robison; Robison, 1991, fig. 6.5. Type material. Holotype: part (UU1020) and counterpart (KUMIP 204390, Fig. 9A–G), Spence Shale, Langston Formation, Utah, USA. Emended diagnosis. Large worm, with one to two annulations per millimetre. Each annulation generally has two bands of double rows of large sclerites, but occasionally bands present one or three rows. Plates 70–80 μm in diameter. Platelets uncommon, but range in size from 40 to 60 μm. Microplates absent. Presence of nodes on sclerites unknown. Gut simple and straight. Description. The body is coiled, 111 mm long and ranges in width from 2.5 mm at the base of the decayed proboscis (outer end of the coil), to 4 mm in its widest area (up to 5 mm in the partially decayed part), and 1.5 mm in the aboral end. There are 1.4–1.8 annulations per millimetre, more densely packed in the anteriormost end, and an estimated total of c. 160. Annulations present two bands separated by a central naked zone (‘unarmed’ in Conway Morris and Robison, 1986). Bands usually have two rows of sclerites, but some areas show either single rows (inner part of coil, Fig. 9C) or triple rows (some parts of the outer coil, Fig. 9D and the aboral end, Fig. 9E). The limit of each annulation (arrows, Fig. 9A) is not defined by a groove or a crest as in the other specimens described in this paper, but rather by the closely spaced, well-defined rows of sclerites of adjoining annulations, being the inner, naked zone (‘unarmed’ in Conway Morris and Robison, 1986) wider and less well-defined by the somewhat looser arrangement of the sclerites. Discussion. The type material of this species from Utah was reexamined because previous work on Murero palaeoscolecids had made comparisons with this taxon (Conway Morris and Robison, 1986; Gámez Vintaned, 1995), referring the Spanish material to Palaeoscolex cf. P. ratcliffei. The tentative assignment to Wronascolex herein is due to the impossibility of recognizing any nodes on the surface of the circular plates after their recrystallization to iron-magnesium oxide (Fig. 9G).

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Otherwise, the characteristics are consistent with those of this genus, as was noted by Ivantsov and Zhuravlev (2005). It is, however, a large species, in the upper range of the genus. Occurrence. This specimen was collected from talus at locality SE 1/4 sec. 14, T. 10 N., R. 2 W., near Calls Fort, Utah, probably in the lower 15 m (according to Robison, 1969) of the Spence Shale Member, Langston Formation (Cambrian Series 3, Stage 5). Indeterminate palaeoscolecid (Fig. 9H–J) 2005. Palaeoscolex cf. P. ratcliffei Robison; García-Bellido and Aceñolaza, 2005, pp. 470–71, pl. 1, figs. 3–4. 2011. Palaeoscolex sp. cf. P. ratcliffei Robison, 1969; García-Bellido and Aceñolaza, 2011, pp. 534–536, figs. 3A–D. Material. Partial specimen, part and counterpart (PIL 14.548), Lampazar Formation (Furongian), Sierra de Cajas, Jujuy, Argentina. Description. The preserved length of the most complete part is 18 mm, and has a maximum width of 2.4 mm. The body is traversed by parallel grooves, defining thirty annulations, each approximately 0.25 mm long, and thus about 4 annulations per mm. Under a scanning electron microscope (Fig. 9I–J), the surface of the cuticle presents a tessellated polygonal pattern, characteristic of palaeoscolecids sensu stricto (cf. Harvey et al., 2010), but lacks any biomineralised sclerites (plates, platelets or microplates). These tessellae vary in size: larger near the annulation boundary (arrow in Fig. 9J), smaller in the centre. Each annulation has two transverse lines of sclerite pits, located beside the grooves, leaving an unornamented central band in the annulation. Discussion. García-Bellido and Aceñolaza (2011) assigned this specimen to Palaeoscolex, with comparison to Wronascolex? ratcliffei. However, examination of the specimen under SEM shows that, although the tessellated pattern of palaeoscolecids sensu stricto is present in the cuticle, there are no sclerites and thus, this fossil deviates from the rest of that group. Because the taxon is known from a single incomplete specimen we have refrained from formalising it at the species level and its systematic affinities within the Priapulida are uncertain. 5. Palaeobiogeographical relationships of Cambrian palaeoscolecids Early Palaeozoic palaeoscolecid worms or their isolated sclerites (e.g., Hadimopanella) have been described from most major palaeocontinents: Gondwana, Laurentia, Siberia, Avalonia and Baltica. Wronascolex and H. oezgueli are only present in the tropical to temperate waters (latitude>30°) around Gondwana, and in Siberia (Fig. 10). H. oezgueli has been described from Turkey (Gedik, 1977), Spain (van de Boogaard, 1983), Sardinia (Cherchi and Schroeder, 1985), Kazakhstan (Märrs, 1988) and Iran (Wrona and Hamdi, 2001); Hadimopanella apicata occurs in Spitsbergen (Wrona, 1982), Shropshire, England (Hinz, 1987), and Greenland (Peel and Larsen, 1984; Bendix-Almgreen and Peel, 1988; Skovsted, 2008). Hadimopanella antarctica was originally described from erratic boulders on King George Island, Antarctica by Wrona (1987), who later found it together with H. apicata (Wrona, 2004), making these the highest palaeolatitude representatives. Other members of the group, such as Wronascolex? ratcliffei and the isolated sclerite Hadimopanella? coronata (van den Boogaard, 1989) seem to have a wider distribution (Laurentia and Baltica, respectively, Fig. 10). Until a re-evaluation of the various H. oezgueli morphs is undertaken, a more detailed palaeobiogeographic analysis may be futile. Acknowledgements Funding for this research was provided by Australian Research Council (LP0774959, DP120104251), Spanish Research Council (RYC200700090, CGL2009-07073) and National Geographic Society Research & Exploration (#8991-11) grants, with additional financial assistance from Beach Energy Ltd. and the South Australian Museum, while SeaLink has provided logistical support. We are grateful to the Buck family for access to the field area. We thank our collaborators in Emu Bay

Shale research, J. Gehling, J. Jago, and M. Lee for support and advice, in addition to R. Atkinson, M. Binnie, G. Brock, A. Camens, A. Daley, M. Gemmell, K. Kenny, P. Kruse, J. Laurie, B. McHenry, N. Schroeder, E. Thomson, and members of the South Australian Museum Waterhouse Club for their assistance in the field and lab. Thanks also to A. Pineda for lending his specimen for study and U. Farrell for loan of the type material from University of Kansas, to Hu Shixue for additional information on some of the Chinese material, to G. Brock for SEM-EDS analysis of a W. antiquus specimen, and to the journal's referees for their advice. Appendix A. Supplementary data Supplementary data associated with this article can be found in the online version, at http://dx.doi.org/10.1016/j.gr.2012.12.002. These data include Google maps of the most important areas described in this article. References Ahnelt, P., 1984. Chaetognatha. In: Matoltsy, A.G., Richards, K.S. (Eds.), Biology of the Integument. 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