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Home , Aysheaia, Jianshanopodia, Kerygmachela, Lobopodia, Onychodictyon, Pambdelurion

[Palaeontology, Vol. 52, Part 3, 2009, pp. 561–567]

AN LOBOPODIAN FROM THE SOOM SHALE LAGERSTA¨ TTE, SOUTH AFRICA by ROWAN J. WHITTLE*,à, SARAH E. GABBOTT*, RICHARD J. ALDRIDGE* and JOHANNES THERON *Department of Geology, University of Leicester, Leicester LE1 7RH, UK; e-mails: [email protected]; [email protected] Department of Geology, University of Stellenbosch, Private Bag XI, Stellenbosch 7602, South Africa; e-mail: [email protected] àPresent address: British Antarctic Survey, Madingley Road, Cambridge, CB3 0ET, UK; e-mail: [email protected]

Typescript received 18 July 2008; accepted in revised form 27 January 2009

Abstract: The first lobopodian known from the Ordovician and . The new preserves an annulated is described from the Soom Shale Lagersta¨tte, South Africa. trunk, lobopods with clear annulations, and curved claws. It The organism shows features homologous to Palaeozoic mar- represents a rare record of a benthic organism from the ine lobopodians described from the Middle Bur- Soom Shale, and demonstrates intermittent water oxygena- gess Shale, the Lower Cambrian Chengjiang biota, the Lower tion during the deposition of the unit. Cambrian Lagersta¨tte and the Lower Cambrian of the Baltic. The discovery provides a link between marine Key words: Lagersta¨tte, lobopodian, Ordovician, Soom Cambrian lobopodians and younger forms from the Shale.

Cambrian lobopodians are a diverse group showing a in an intracratonic basin with water depths of approxi- great variety of body shape, size and ornamentation. mately 100 m (Gabbott 1999). Dominantly quiet water However, they share a segmented onychophoran-like conditions are indicated by a lack of flow-induced sedi- body, paired soft-skinned annulated lobopods, and in mentary structures and the taphonomy of the . The most cases body (Bergstro¨m and Hou 2001). Soom Shale sediment was largely anoxic; geochemical Only one undescribed specimen of lobopodian has previ- analyses indicate that euxinic bottom waters prevailed at ously been identified between the late Cambrian and the times (Gabbott 1998). Carboniferous (von Bitter et al. 2007) (Table 1). Here we The Soom Shale community consisted of invertebrates, describe a new occurrence of a Late Ordovician lobopo- early and algae. In particular there is a num- dian and discuss the morphological interpretation of the ber of taxa (Moore and Marchant 1981; Fortey specimen. and Theron 1994; Braddy et al. 1995, 1999; Gabbott et al. 2003; Whittle et al. 2007), conodonts (Theron et al. 1990; Aldridge and Theron 1993; Gabbott et al. 1995), agna- GEOLOGICAL SETTING AND FAUNA thans (Aldridge et al. 2001), (Aldridge et al. 1994), scolecodonts (Whittle et al. 2008), orthoconic The argillaceous Soom Shale Member is a 10–15 m thick (Gabbott 1999) and enigmatica (Aldridge unit and is the lower member of the Cedarberg Forma- et al. 2001). Many of the fossils exhibit soft part preserva- tion, which occurs towards the top of the Table Moun- tion, which can include muscle tissue (Gabbott et al. tain Group in South Africa. The Soom Shale occurs 1995). It appears that soft tissues were replicated by au- immediately above glacial tillites and dropstones are pres- thigenic clay minerals and alunite group minerals, some- ent at the base of the member. Water temperatures are times with a high degree of fidelity (Gabbott 1998; thought to have been relatively cool (Gabbott 1998) and Gabbott et al. 2001). in this respect the Soom Shale represents an unusual restricted marine fauna (Aldridge et al. 1994). The Soom Shale Member has been correlated with MATERIALS AND METHODS the persculptus graptolite Biozone of Hirnantian (Late Ordovician) age (Sutcliffe et al. 2000; Young et al. 2004). The repository of the specimen (C1974) is the Council of Palaeogeographical reconstructions indicate that it was Geosciences of South Africa, Bellville. It was discovered at deposited at approximately 30–45S (Young et al. 2004), Keurbos Quarry near Clanwilliam (3216¢ S, 1858¢ E) in

ª The Palaeontological Association doi: 10.1111/j.1475-4983.2009.00860.x 561 562 PALAEONTOLOGY, VOLUME 52

TABLE 1. Fossil lobopodians from the Early Cambrian to the Tertiary. Helenodora and specimens found from the onwards have been interpreted as onychophorans.

Taxa, authorship, year of publication Age Distribution

Luolishania longicruris Hou and Chen, 1989 Early Cambrian Chengjiang Lagersta¨tte, China inermis Chen et al., 1995 Early Cambrian Chengjiang Lagersta¨tte, China Cardiodictyon catenulum Hou et al., 1991 Early Cambrian Chengjiang Lagersta¨tte, China fortis Hou and Bergstro¨m, 1995 Early Cambrian Chengjiang Lagersta¨tte, China sinicum Chen et al., 1989 Early Cambrian Chengjiang Lagersta¨tte, China ferox, Hou et al., 1991 Early Cambrian Chengjiang Lagersta¨tte, China decora Liu et al., 2006 Early Cambrian Chengjiang Lagersta¨tte, China Miraluolishania haikouensis Liu and Shu, 2004* Early Cambrian Chengjiang Lagersta¨tte, China pedunculata, Walcott, 1911 Middle Cambrian , Canada A.? prolata Robison, 1985 Middle Cambrian Burgess Shale, Canada Hallucigenia sparsa (Walcott, 1911) Middle Cambrian Burgess Shale, Canada Hadranax augustus Budd and Peel, 1998 Early Cambrian Sirius Passet Lagersta¨tte, North Greenland auerswaldae Pompeckj, 1927 Early Cambrian Baltic region Orstenotubulus evamuellerae Maas et al., 2007 Cambrian Sweden Not yet formally described von Bitter et al., 2007(fig. 2E, F) Silurian Eramosa Lagersta¨tte, Canada Helenodora inopinata Thompson and Jones, 1980 Carboniferous Mazon Creek of northern Illinois Cretoperipatus burmiticus Engel and Grimaldi, 2002** Cretaceous Amber of Myanmar (Burma) Tertiapatus dominicanus Poinar, 2000 Eocene Baltic amber Succinipatopsis balticus Poinar, 2000 Eocene Baltic amber

*In Liu et al. (2004), was considered to be a junior synonym of Luolishania longicruris by Ma et al. (2006) contested by Liu et al. (2008b). **In Grimaldi et al. (2002). a light grey siltstone. In fifteen years of collecting this is fact, plesiomorphic while others were not demonstrable the only known specimen. It occurs in multiple pieces in the majority of fossil forms. He further noted that the that comprise part (C1974 a, d), and counterpart (C1974 presence of lobopodian features in and b–c, e). The specimen is incomplete, with the anterior indicated that lobopodians were not mono- and possibly the posterior portions missing. The fossil phyletic. Liu et al. (2007) supported the view that lobopo- was studied using an optical microscope, drawn with the dians are paraphyletic, and cladistic analyses by Ma aid of a camera lucida, and photographed with and with- Xiaoya (pers. comm. 2008) suggest that the group is para- out ammonium chloride coating, using a digital camera phyletic or polyphyletic. Given the continuing uncertain- (Canon EOS 5D). A Hitachi S-3600N Scanning Electron ties surrounding these phylogenetic relationships, we use Microscope Energy Dispersive X-ray facility (SEM EDX) the here with equivocation. was used in partial vacuum mode for chemical analyses The proposed affinity of the Cambrian lobopodians of the uncoated specimen. with extant onychophorans (e.g. Robison 1985; Ramsko¨ld and Chen 1998) has been the subject of some debate. Bergstro¨m and Hou (2001) noted similarities to tardi- SYSTEMATIC PALAEONTOLOGY grades and Liu et al. (2008a) argued that lobopodians have a much closer relationship to than to Phylum LOBOPODIA Snodgrass, 1938? either onychophorans or .

Remarks. In recent analyses of panarthropod relationships doubts have been raised regarding the of the Class XENUSIA Dzik and Krumbiegel, 1989 Lobopodia. Ramsko¨ld and Chen (1998) concluded that Cambrian lobopodians form two that join the Description. The specimen is incomplete, with a length of at extant onychophorans in an unresolved trichotomy; they least 70.7 mm and a width of at least 31 mm. The central body combined the three clades within the total group Ony- portion appears sub-cylindrical and shows clear transverse annu- chophora. Budd (1999), however, regarded the support lations in some places (Text-figs 1–2), visible at a density of for a monophyletic ‘’ to be weak. He argued c. 7–8 ⁄ mm (Text-fig. 3F). The body is elongated and tapers towards the presumed posterior, appendages decrease in size and that some of the characters considered by Ramsko¨ld and the central trunk extends beyond what is probably the final pos- Chen (1998) to be synapomorphies of this group were, in WHITTLE ET AL.: ORDOVICIAN LOBOPODIAN FROM THE SOOM SHALE 563

TEXT-FIG. 1. Lobopodian specimen C1974 from the Soom Shale. Two sets of appendages are visible on the specimen, on either side of the main trunk (see Text-figure 2 for composite explanatory drawing). A, Part (C1974 a, d), the trunk of the organism is mostly preserved in positive relief. B, Counterpart (C1974 b–c, e), the main trunk is mostly preserved in negative relief.

5 mm A 5 mm B terior appendage. At the anterior end, appendages become more branch (Text-figs 1–2, 3A), which is further divided into three crowded and this end of the fossil is incomplete (Text-figs 1–2). or four tips distally. This degree of complexity is not clear on There are no cephalic or caudal structures that clearly indicate any of the other appendages, and thus a11 may be a modified the orientation of the fossil. However, there is variation in the anterior-most appendage. Posterior of a8–a11 there are seven position and size of the lobopods which has been noted in other appendages labelled a7–a1, which are simple lobes with clear taxa in relation to orientation. Paucipodia has a body that tapers margins (Text-figs 1–2); these appendages decrease in size at both ends, extending beyond the final lobopods; appendages towards the posterior of the organism. On some (for example a7 are longest in the middle and become shorter towards the ante- to a4) there are traces of transverse annulations (Text-figs 2, rior and posterior (Hou et al. 2004). However, in Cardiodictyon 3E). On a5 and a6 (C1974b), there is an indication of a feature and Luolishania, crowding of appendages has been noted at the with positive relief along the axis of some of the lobes which anterior end of the body, and this has been suggested as giving may be homologous to the fine canal seen in the appendages of an impression of initial cephalisation (Bergstro¨m and Hou other lobopodians (Chen et al. 1995; Bergstro¨m and Hou 2001; 2001). A decrease in lobopod spacing towards one end of the Liu et al. 2006). fossil, and the apparent increase in appendage complexity indi- On the right of the body the appendages (Text-fig. 1A) are cate that this is most likely the anterior of the fossil, although preserved in two dimensions; in some, coloured mineral films evidence of cephalic features cannot confirm this. In C1974, the indicate their position (Text-fig. 1). Some of the appendages appendages get smaller towards the other end of the body, and roughly correspond to the position of the lobes on the left side the body extends slightly beyond the smallest appendage; this is of the body although they are slightly offset (Text-fig. 2). How- considered to be the posterior of the organism. ever, they cannot be matched up exactly because they are not On the left hand side of the body (Text-fig. 1A) the append- preserved along the entire length of the body, and they are very ages are elongate, unjointed, preserved in positive relief and faint in some places. It is likely that the body has become taper towards their termination. They have been numbered from slightly twisted, and thus the appendages no longer lie exactly posterior (where they can be clearly recognised individually) to opposite each other. The impressions of some of the transverse anterior (where the individual extent of each appendage is not annulations from the lobes can be seen with a density of clear) (Text-fig. 2). There are 11 appendages preserved; the ante- c. 2–3 ⁄ mm (Text-fig. 3B). rior-most appendages from a8–a11 are more crowded and On appendages a3, a4, possibly a5, a8 and a9 (those from the appear complex owing to the presence of branches and ⁄ or orna- left hand side of the body, where preservation is clearest) claws mentation (Text-figs 1–2, 3A, C). Appendage a11 has a large are evident, which are curved with their convex edge facing 564 PALAEONTOLOGY, VOLUME 52

a11 lateral lobes an anomalocaridid affinity is discounted. The specimen is similar in size to other lobopodians, for example Paucipodia (Hou et al., 2004) and Hadranax, a10 which is also incomplete at the anterior and posterior ends (Budd and Peel 1998). It is similar in width to Jians- a9 hanopodia, although this Chengjiang fossil is much longer (Liu et al. 2006). a8 Modern onychophorans have a pair of claws on each lobopod and most fossil lobopodians have clawed lobo- pods, but the number and arrangement of claws varies a7 aan (Hou and Bergstro¨m 1995). Each lobopod on C1974 has pcf at least one pair of curved claws the presence of which a6 distinguishes it from Jianshanipodia, Xenusion and Hadr- anax. The appendages are stout, comparable with those in a5 Jianshanipodia and Hadranax (Budd and Peel, 1998; Liu cl o et al., 2006). The exact structure of the appendages is a4 unclear, but some branching occurs on at least one, which may be similar to the branched frontal appendage a3 of Hadranax (Budd and Peel, 1998). tan The possession of annulations and fleshy unjointed cl a2 lobes is consistent with a placement of the specimen a1 within the lobopodians. It is most similar to Cambrian forms, but lacks features that are diagnostic of any cur- rently described . The preserved features do not 2 mm even allow it to be assigned to a particular family, and it Areas of gut does not show any definitive autapomorphies. In view of preservation this, the specimen is not classified below class level and additional specimens will be necessary to resolve its phy- TEXT-FIG. 2. Composite camera lucida drawing of part and counterpart (C1974a–e); a1–a11 refer to the appendages on the logenetic position and . left side of the body that are mostly preserved in positive relief, with a11 anteriormost and a1 posterior-most. Dark areas on the distal tips of these appendages are claws (cl). The appendages on PRESERVATION AND ECOLOGY the right side of the body are only faintly preserved; however, some of the annulations on this side are seen as clear black lines Soft tissues have been preserved in the Soom Shale (aan). Annulations can also be seen on some of the appendages through rapid postmortem mineralization by authigenic on the left and on the main trunk (tan). Features with positive clay minerals (Gabbott et al. 2001). Original biominerals, relief can be seen along the centre of a6 and possibly a5, (pcf) such as aragonite, calcite and apatite, have, however, been on a6. The areas where the gut trace can be seen are shaded in completely dissolved to leave moulds, which have subse- grey; ‘o’ refers to the area of organic preservation that appears quently compacted (Gabbott 1998; Gabbott et al. 2001). in the region of the gut. Many of the systematic characters of fossil lobopodians are cuticular and, because specimen C1974 preserves anteriorly and are much darker than the surrounding matrix mostly labile, noncuticular anatomy, comparison with (Text-fig. 2). There are possibly two claws per appendage on a3 other species is difficult. External ornamentation such as and a4; one may be slightly bigger than the other (Text-fig. 3D). tubercles, nodes and sclerites is absent, either because The more complex appendages (a8 and a9) possibly carry more these features are not preserved or because they were not claws. There is an axial gut trace, evident as a raised structure along present on the organism. Annulations are present on a most of the body length. The gut is mostly covered by overlying few areas on the body, an indication that some surficial material, but where underlying areas have been exposed, it is characteristics have the potential to be preserved. The revealed as darker than the surrounding tissue, with preservation presence of a gut and the preserved soft-tissues of the occurring as organic carbon in two patches (Text-fig. 2). organism indicate that the specimen is a body fossil and not a moult. Remarks. The presence of the clawed appendages indicates The morphology of the specimen is consistent with it that the specimen is a lobopodian; as it has no traces of being benthic. Gabbott (1998) indicated that there was WHITTLE ET AL.: ORDOVICIAN LOBOPODIAN FROM THE SOOM SHALE 565

intermittent water oxygenation during the deposition of the Soom Shale, which means conditions occasionally could have been hospitable for benthic taxa. All of the previously described body fossils of lobopo- dians and onychophorans come from units that were probably deposited in warmer waters. However, the fossil record of isolated sclerites identified as phosphatized lob- opodian plates is diverse and much more widespread in Lower Cambrian deposits (Zhang and Aldridge 2007). The evidence presented here demonstrates that lobopodi- B ans could inhabit cooler, nontropical waters and lends A support to the evidence from lobopodian plates that lobo- podians had a much wider distribution than their current body fossil record indicates.

Acknowledgements. RJW acknowledges a NERC studentship (NER ⁄ S ⁄ A ⁄ 2003 ⁄ 11281); collecting was also funded by research grants from NERC (GR3 ⁄ 10177 to RJA) and the National Geographic Society (6715-00 to RJA). Mr and Mrs J. N. Nieuwoudt, Keurbos Farm, and Mr and Mrs J. D. Coetze, Sandfontein, allowed access to fossil localities. The Council for Geoscience, South Africa, provided logistical support. Excavation permit (No. 2005-11-002) for this work was issued by the Provin- C cial Heritage Authority. The South African Heritage Resources Agency (SAHRA, National Heritage Authority) was responsible for authorizing the export permit to allow for the study of the fossil material in the UK. We acknowledge two anonymous reviewers, whose suggestions improved the manuscript. We thank Ma Xiaoya for her helpful discussion, Derek Siveter and Mark Williams for suggestions with manuscript drafting and Rob Wilson for technical assistance. D

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