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XXX10.1144/jgs2015-083J. R. Paterson et al. Konservat-Lagerstätte 2016 Downloaded from http://jgs.lyellcollection.org/ by guest on September 24, 2021

2015-083review-articleReview focus10.1144/jgs2015-083The Emu Bay Shale Konservat-Lagerstätte: a view of life from East GondwanaJohn R. Paterson, Diego C. García-Bellido, James B. Jago, James G. Gehling, Michael S.Y. Lee &, Gregory D. Edgecombe

Review focus Journal of the Geological Society Published online November 10, 2015 doi:10.1144/jgs2015-083 | Vol. 173 | 2016 | pp. 1–11

The Emu Bay Shale Konservat-Lagerstätte: a view of Cambrian life from East Gondwana

John R. Paterson1*, Diego C. García-Bellido2, 3, James B. Jago4, James G. Gehling2, 3, Michael S.Y. Lee2, 3 & Gregory D. Edgecombe5 1 Palaeoscience Research Centre, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia 2 School of Biological Sciences & Environment Institute, University of Adelaide, Adelaide, SA 5005, Australia 3 Earth Sciences Section, South Australian Museum, North Terrace, Adelaide, SA 5000, Australia 4 School of Natural and Built Environments, University of South Australia, Mawson Lakes, SA 5095, Australia 5 Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK * Correspondence: [email protected]

Abstract: Recent discoveries from the lower Cambrian Emu Bay Shale (EBS) on , South Australia, have provided critical insights into the tempo of the of , such as the origin and seemingly rapid evolution of compound eyes, as well as extending the geographical ranges of several groups to the East Gondwa- nan margin, supporting close faunal affinities with South China. The EBS also holds great potential for broadening knowl- edge on taphonomic pathways involved in the exceptional preservation of in Cambrian Konservat-Lagerstätten. EBS fossils display a range of taphonomic modes for a variety of soft tissues, especially phosphatization and pyritization, in some cases recording a level of anatomical detail that is absent from most Cambrian Konservat-Lagerstätten.

Received 1 July 2015; revised 2 September 2015; accepted 16 September 2015

The lower Cambrian (Series 2, Stage 4) Emu Bay Shale (EBS) dailyi and Redlichia takooensis (Jell in Bengtson et al. 1990; Jago Konservat-Lagerstätte (Fig. 1) provides important information et al. 2006; Paterson & Brock 2007; Paterson et al. 2008). This regarding the composition of early communities and a win- equates to the Canglangpuan Stage (= upper Nangaoan–lower dow on the Cambrian radiation in Gondwana. One of the most Duyunian stages) of South China and the middle–upper Botoman intriguing aspects of the EBS is that although it yields a biota that of Siberia (Paterson & Brock 2007; Peng et al. 2012; Landing is taxonomically similar to Cambrian -type biotas et al. 2013). Based on the calibrated 2012 Geologic Time Scale, (Paterson et al. 2008), its nearshore depositional setting (Gehling the numerical age of the EBS is 514 ± 1 Ma (see Peng et al. 2012, et al. 2011) and disparate preservation styles (e.g. Briggs & Nedin fig. 19.3). The EBS is approximately coeval with the Balang and 1997; Lee et al. 2011; Paterson et al. 2011) are at odds with our Guanshan biotas of China, but younger than the Chengjiang and current understanding of typical Burgess Shale-type deposits and Lagerstätten (Peng et al. 2012). their associated taphonomic pathways and signatures (Gaines et al. The EBS is exposed in two areas of the northeastern coast of 2008, 2012b). This has led Gaines (2014) to explicitly exclude the Kangaroo Island: (1) the type section on the western side of Emu Bay EBS from the global list of more than 50 known Burgess Shale- (Daily et al. 1980); (2) Big Gully, to the east of Emu Bay (Fig. 1; type deposits, pending detailed comparative study. Gehling et al. 2011); it is only the latter site that hosts the Shelly fossils were first discovered in the EBS at Emu Bay Konservat-Lagerstätte. At Big Gully, the EBS unconformably in 1952 by Reginald Sprigg. In 1954, Brian Daily found large spec- overlies the Marsden Sandstone, a coarsening upward package of imens of the Redlichia in the EBS at Big Gully, east of Emu clastic sediments deposited in a shallow subtidal to shoreface set- Bay. However, the first description of soft-bodied EBS fossils was ting. The base of the EBS represents a sequence boundary and is not published until the late 1970s (Glaessner 1979). The history of marked by a conglomerate (up to 2 m thick) that contains various investigations on the EBS Konservat-Lagerstätte was documented clast types and sizes, including sandstone from the Marsden by Paterson et al. (2008) and Jago & Cooper (2011). Sandstone. Above the conglomerate, there is a sharp transition into mudstones that contain the Konservat-Lagerstätte, which is Age, geology and palaeoenvironmental setting restricted to the lower 10 m or so of the unit. Above this, sand- stones become increasingly prominent and, towards the top of the The Emu Bay Shale is a formation of the lower Cambrian (Series formation, contain large arthropod traces. The EBS is conformably 2) Kangaroo Island Group, a largely clastic shelf succession within overlain by the red–brown feldspathic sandstones of the subtidal the Stansbury Basin (Daily et al. 1980; Gehling et al. 2011; Jago Boxing Bay Formation, which also contain abundant arthropod et al. 2012). During deposition of the EBS and adjacent units, traces (Gehling et al. 2011). South Australia was located on the palaeoequator in the ‘tropical The interval of the EBS containing the Konservat-Lagerstätte carbonate development zone’ (Brock et al. 2000), and formed a consists of dark grey, typically laminated micaceous mudstone, part of the East Gondwana margin (Torsvik & Cocks 2013). The with common interbeds of siltstone (up to 5 cm thick) and fine sand- EBS correlates with the lower Cambrian (Series 2, Stage 4) stone (up to 20 cm thick) that probably resulted from intermittent Pararaia janeae trilobite Zone of mainland South Australia, based sediment gravity flows (Gehling et al. 2011). The mudstones show on the presence of the Estaingia bilobata, signs of small-scale fluidization, with the siltstones or sandstones

© 2016 The Author(s). Published by The Geological Society of London. All rights reserved. For permissions: http://www.geolsoc.org.uk/permissions. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics Downloaded from http://jgs.lyellcollection.org/ by guest on September 24, 2021

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(Gehling et al. 2011). This depositional setting is in stark contrast to the majority of other Cambrian Konservat-Lagerstätten, specifi- cally Burgess Shale-type deposits that formed in outer shelf envi- ronments, either near or immediately adjacent to the seaward margins of expansive carbonate platforms (e.g. Burgess Shale), or offshore of broad clastic shelves (e.g. Chengjiang) (Gaines 2014).

The Emu Bay Shale biota: diversity and palaeobiogeographical affinities Of the 50+ now known from the EBS, around 30% possess biomineralized structures, the remainder being entirely soft-bod- ied. However, in terms of the relative abundance of specimens, biomineralized taxa prevail because of the numerical dominance of the trilobite Estaingia bilobata (up to 80% of individuals on any given bedding surface). As in Cambrian Burgess Shale-type biotas (Caron & Jackson 2008; Caron et al. 2014; Zhao et al. 2014), species diversity and abundance in the EBS are dominated by panarthropods, which comprise 28 recorded species to date, with several yet to be described. The survey of the biota below is accordingly focused on , with taxonomic groups drawing on the classification of Legg et al. (2013). Other major groups represented include , molluscs, , cycloneuralian worms and a sin- Fig. 1. Geology of the area to the east of Emu Bay on the NE coast gle species of annelid. Some groups of debated affinity that are of Kangaroo Island, South Australia, showing the extent of the Emu known from other Cambrian Burgess Shale-type deposits are rep- Bay Shale at Big Gully, including the location of the main Konservat- resented by single species in the EBS, including chancelloriids, the Lagerstätte sites on the shoreline and at Buck Quarry (after Gehling probably deuterostome ‘cambroernids’ (incorporating the rotadis- et al. 2011). cids), and the vetulicolians (see Box 1; Fig. 2). occasionally loading into the underlying mudstones, resulting in Arthropods flame structures. The mudstones do not appear to be bioturbated Trilobites (especially where the soft-bodied fossils occur) and, in combination with the presence of sedimentary pyrite (McKirdy et al. 2011) and Five species have been identified in the EBS (Jell in Bengtson et al. 1990; Paterson & Jago 2006), two of which are abundant pyritized soft tissues (Paterson et al. 2011), indicate anoxia below (Estaingia bilobata and Redlichia takooensis: Fig. 3a) whereas the the sediment–water interface based on comparisons with Cambrian remaining three are very rare (Balcoracania dailyi, Holyoakia Burgess Shale-type deposits (Gabbott et al. 2004; Gaines & Droser simpsoni and Megapharanaspis nedini). The trilobites suggest 2005, 2010; Gaines et al. 2012a,b; Gaines 2014). Geochemical strong biogeographical connections with South China and studies also indicate anoxic conditions within the sediment (Hall Antarctica; as outlined below, many of the non-biomineralized et al. 2011; McKirdy et al. 2011), perhaps owing to the sealing of species in the EBS have their closest relatives in the Chengjiang the substrate by microbial mats (although there is no unequivocal biota and amplify the signal for affinities to South China. Estaingia physical evidence of them), thus generating a sharp redox boundary. is restricted to East Gondwana (Australia and Antarctica) and If microbial mats were responsible for a permeability barrier at the South China (Dai & Zhang 2012). Redlichia takooensis, by far the sediment–water interface, this may provide a taphonomic alterna- largest trilobite in the biota (articulated specimens up to 25 cm tive to the early sealing of sediments by pervasive carbonate long), was originally described from South China. Holyoakia is cements that is typical of Burgess Shale-type preservation sensu otherwise known from the type species in the Central Transantarctic stricto (Gaines et al. 2012b; Gaines 2014); interestingly, there are Mountains (Palmer & Rowell 1995). Balcoracania was originally claims for microbial mats in the Sirius Passet Lagerstätte (Mángano documented from sites in South Australia, but subsequently found et al. 2012). Moreover, EBS studies (McKirdy et al. 2011; Hall in Antarctica (Palmer & Rowell 1995). Balcoracania dailyi is et al. 2011) suggested that the benthos and water column were well noteworthy for having the largest number of thoracic segments oxygenated, which is supported (in part) by the low organic carbon (103) known from any trilobite anywhere in the world (Paterson & content in the mudstones, in addition to redox-sensitive trace ele- Edgecombe 2006). ment ratios (but see Gaines (2014, p. 132) regarding their reliability as redox proxies). However, low total organic carbon values (<1%) Other lamellipedian arthropods can also be explained by low primary productivity and/or high sed- The names Lamellipedia and refer to trilobites and their imentation rates diluting the organic matter. Notwithstanding, an (mostly non-biomineralized) relatives. Emucaris fava and oxic water column is further suggested by a diverse and abundant Kangacaris zhangi (Fig. 3b), both blind species, belong to the fam- nektobenthic–pelagic fauna, but the question of fully aerobic versus ily Emucarididae, originally known only from the EBS (Paterson dysaerobic–anaerobic conditions on the seafloor requires further et al. 2010). The only other record of the family is a species from investigation (discussed below). Chengjiang assigned to Kangacaris (Zhang et al. 2012). Another The EBS seems to have been rapidly deposited in a relatively blind arthropod in the EBS, Australimicola spriggi (Fig. 3c), was nearshore setting adjacent to an active tectonic margin that gener- originally classified in a lamellipedian group named Conciliterga, ated continual syndepositional faulting and slumping. The with which it shares its style of attachment (Paterson Konservat-Lagerstätte interval appears to form part of a localized, et al. 2012), but other phylogenetic analyses have grouped it with deeper-water micro-basin succession on the inner shelf that was Cheloniellida, known from various species in the , subject to fluctuating oxygen levels, at least in the bottom waters and (Stein et al. 2013). Downloaded from http://jgs.lyellcollection.org/ by guest on September 24, 2021

Emu Bay Shale Konservat-Lagerstätte 3

Box 1. Nesonektris and the affinities of Smith 2012). Nonetheless, the question of whether vetulicolians vetulicolians belong to the deuterostome stem-group or are more closely related to one of the extant deuterostome subgroups (thus mak- Vetulicolians are Cambrian animals known from 15 named spe- ing them crown-group Deuterostomia) remains unclear. The cies that occur in the Chengjiang and Guanshan biotas of China, bipartite division of the body had been argued to suggest affini- Sirius Passet and the Burgess Shale. An EBS vetulicolian, ties to tunicates (Lacalli 2002), implying membership of Nesonektris aldridgei García-Bellido et al. 2014, demonstrated that their distribution extended to East Gondwana. Vetulicolians Vetulicolia within Chordata. This systematic position would were originally interpreted as bivalved arthropods because their predict the presence of a notochord in vetulicolians, and indeed bipartite body is divided into an anterior part that has some sim- an axial rod that runs through the posterior body part of ilarities to a carapace and a posterior part composed of segments Nesonektris displays some morphological and preservational separated by soft intersegmental regions. Arthropod affinities features consistent with its identity as a notochord. In particular, were challenged by the absence of limbs and by the discovery of specimens show the rod fragmenting into sections, similar to the features that were more consistent with alternative (specifically early decay stages of the notochord in Amphioxus and jawless deuterostome) affinities. Based especially on a series of open- vertebrates (Sansom et al. 2013). In addition to their bipartite ings in the anterior part of the body interpreted as gill slits (Shu bodies, vetulicolians and tunicates share a thick cuticle, a termi- et al. 2010), the deuterostome hypothesis has generally found nally positioned mouth, and restriction of the notochord to the favour (Aldridge et al. 2007; Vinther et al. 2011; Ou et al. 2012; segmented posterior part of the body.

Fig. 2. (a) Reconstruction of Nesonektris aldridgei; by Katrina Kenny. (b) Axial rod structure of N. aldridgei (SAM P46336a) interpreted as a putative notochord, with arrows showing offset blocks. (c) Phylogenetic position of vetulicolians within Deuterostomia, based on the analysis by García-Bellido et al. (2014); parsimony-bootstrap values (above branches) and Bremer support (below) are shown for analyses including/excluding the non- vetulicolian fossil taxa.

Cheliceriform and ‘’ arthropods (Fig. 3h), includes specimens preserving the eyes, the anteriormost A common EBS arthropod (Fig. 3d), the description of which is cur- cephalic appendage, a series of phosphatized midgut glands, and the rently pending publication, has 11 trunk segments, a large paddle- trunk segments bearing biramous appendages extending behind the shaped telson and massive gnathobases on its cephalic appendages, carapace. A second species of , I. glaessneri, is smaller, with suggesting a relationship to Sanctacaris, Utahcaris and probably also smooth valves and short cardinal spines. is characterized by (Conway Morris & Robison 1988; Legg 2014). Comparisons coarse polygonal ornament, a spiniferous lateral ridge on each cara- with Sidneyia have also been made in the case of another EBS arthro- pace valve, and marginal spines in stereotypical positions. The pod, Squamacula buckorum (Fig. 3e; Paterson et al. 2012; Stein et al. is mostly known from empty carapaces in all its occurrences world- 2013). Squamacula is otherwise recorded only in Chengjiang (Zhang wide (Vannier et al. 2007), and the EBS species Tuzoia australis et al. 2004), providing one of numerous biogeographical links (Fig. 3i) and a large unnamed form (Tuzoia sp.) are typical in this between the EBS and South China. respect. Only a few EBS specimens preserve the large stalked eyes Oestokerkus megacholix (Fig. 3g) belongs to the same family as projecting outside the carapace margin. the Burgess Shale and Chengjiang ‘great appendage’ arthropods Radiodontans and Alalcomenaeus (Edgecombe et al. 2011). With these other leanchoiliids, it shares a long flagellum on each of three is represented by two species in the EBS, distinguished spine-bearing articles of the great appendage (the first head append- by characters of the spiny armature of their frontal appendages age). Another ‘great appendage’ arthropod, Tanglangia rangatanga (McHenry & Yates 1993; Nedin 1995; Daley et al. 2013). Anomalocaris briggsi is the more abundant, with the less common (Fig. 3f), is the second known species of this genus, otherwise frontal appendage assigned to Anomalocaris cf. canadensis. A few recorded only from Chengjiang. The Australian and Chinese species Anomalocaris oral cones are known from the EBS, one of them being share a quadrate cephalic shield, a narrow trunk of 13 segments, and associated with the frontal appendages of A. cf. canadensis (Fig. 3j a styliform telson that is as long as the trunk (Paterson et al. 2015). and k). Other body parts of Anomalocaris, including segmental flaps Bivalved stem-group arthropods and setal blades that in the Burgess Shale and at Chengjiang are known to attach to the body flaps, cannot as yet be definitively The genera Isoxys and Tuzoia, both of which have a ‘bivalved’ cara- assigned to one of the two species. The EBS material is interesting for pace, are known from many lower and middle Cambrian Konservat- revealing more abundant disarticulated body parts (especially flaps) Lagerstätten, and each is represented in the EBS by two species than at other sites with radiodontans and for the pyritization of these (García-Bellido et al. 2009). The common EBS species, I. communis recalcitrant tissues exposing some details not known from elsewhere. Downloaded from http://jgs.lyellcollection.org/ by guest on September 24, 2021

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Fig. 3. Emu Bay Shale arthropods. (a) Redlichia takooensis (left, SAM P52235) and Estaingia bilobata (right, SAM P52236). (b) Kangacaris zhangi (SAM P45179b). (c) Australimicola spriggi (SAM P44482a). (d) New cheliceriform arthropod (SAM P45427). (e) Squamacula buckorum (SAM P15347a). (f) Tanglangia rangatanga (SAM P46331a, mirrored). (g) Oestokerkus megacholix (SAM P43631a, mirrored). (h) Isoxys communis (SAM P47179a). (i) Tuzoia australis (SAM P47994a). (j, k) Anomalocaris cf. canadensis (SAM P51398a); (j) pair of frontal appendages and oral cone; (k) detail of ventral spine. Scale bars: (a–f) 5 mm; (g–j) 10 mm; (k) 3 mm. All photos in Figures 2–6 taken with Canon EOS 50D, under natural or tungsten light from NE and NW at low angle. Illustrations composed and processed, for fine-tune light intensity across figures, with Adobe Photoshop CS3. Downloaded from http://jgs.lyellcollection.org/ by guest on September 24, 2021

Emu Bay Shale Konservat-Lagerstätte 5

Notable examples of this are a series of bars within the strengthening in Redlichia (Conway Morris & Jenkins 1985), were attributed to rays on the body flaps, and the lenses of the compound eye (see Box predation by Anomalocaris (Nedin 1999), but durophagy is unlikely 2; Fig. 4c and d). Coprolites in the EBS that contain skeletal hash of for A. briggsi at least; the slender spines on its frontal appendages trilobites (including Redlichia and Estaingia), in addition to injuries most probably functioned as a feeding net (Daley et al. 2013).

Box 2. Acute vision in the early Cambrian known Cambrian trilobites. Just as noteworthy as their number is a gradient in the diameter of lenses from the edges of the eye The early fossil record of arthropod vision is dominated by trilo- to the centre: these eyes have a specialized zone of enlarged cen- bites, in which the lens arrangements of holochroal compound tral lenses. In living arthropods this region is called a ‘bright eyes have long been investigated, largely because the visual sur- zone’, a zone of increased visual acuity, and is found in preda- face is (like the exoskeleton itself) mineralized with calcium tory forms such as robberflies. Together with calculations for carbonate. In contrast, the eyes of non-biomineralized arthro- the ‘eye parameter’ (which relates the size and arrangement of pods in Cambrian Burgess Shale-type deposits are mostly ommatidia to light levels), the EBS eyes suggest a predator known from their outlines only, the visual surface typically capable of acute vision in dim light. being preserved as carbon films that do not reveal details of the Other large (2–3 cm) isolated compound eyes in the EBS can ommatidial lenses. Two EBS arthropods differ from this picture be assigned to Anomalocaris based on their similarity to the because the visual surfaces of their compound eyes were repli- stalked eyes known in articulated material of that genus in the cated by authigenic mineralization in early diagenesis (the cuti- Burgess Shale and at Chengjiang (Paterson et al. 2011). The cle being replicated by either pyrite or calcium phosphate), thus EBS Anomalocaris eyes are remarkable for the number of lenses recording the arrangements of lenses in higher fidelity than in in the visual surface, exceeding 16000 on the exposed surface typical Burgess Shale-type preservation. One of these eyes is (and presumably a large number more on the unexposed sur- known from several specimens of an arthropod of uncertain face). This is near the upper limit for arthropods throughout their affinities (the eyes are all isolated, detached from the head and geological history (including extant species). The size of the other body parts) (Lee et al. 2011). The eyes are mostly 7–9 mm visual field and number and arrangement of lenses are all con- across their long axis. The visual surface displays more than sistent with acute vision in Anomalocaris, as would be expected 3000 lenses arranged with the dense hexagonal packing of living given other morphological indications for predatory habits in arthropod eyes. This tally vastly exceeds the lens numbers of highly motile animals.

Fig. 4. (a, b) Compound eyes of an unknown arthropod showing large central ommatidial lenses forming a light-sensitive bright zone or fovea (f), and a sclerotized pedestal (p); (a) SAM P43629a; (b) SAM P43687. (c, d) Compound eye of Anomalocaris; (c) part (SAM P45920a), showing visual surface (vs) and eye stalk (es), with the boundary indicated by white arrows; us, undetermined structure; (d) counterpart (SAM P45920b) showing details of ommatidial lenses. Downloaded from http://jgs.lyellcollection.org/ by guest on September 24, 2021

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Lobopodians between Vetustovermis and the Burgess Shale Nectocaris, and the debate over the possible relationship of nectocaridids to Mollusca A single specimen of an armoured lobopodian has been discovered (see Smith 2013, and references therein). in the EBS (García-Bellido et al. 2013a). It is incomplete, but pre- serves five pairs of long, slender, annulated lobopods that bear Sponges setiform spines along the margins, followed by two pairs of shorter lobopods that terminate in a robust claw (Fig. 5a and b). By com- The Porifera so far found in the EBS are all demosponges. parison with luolishaniid lobopodians, the slender appendages are The assemblage is dominated by leptomitids (Fig. 6e), some more the anterior batch. The trunk of the EBS lobopodian bears three than 15 cm long, accompanied by a few specimens of hamptoniids long, robust spines arranged across the dorsal side of each body (Fig. 6f) and choiids. These families are present in many other segment. These characters are shared with the Chinese early Cambrian Lagerstätten (Carrera & Botting 2008; Wu et al. 2014), Cambrian luolishaniids Luolishania (Chengjiang biota) and and thus do not provide significant palaeobiogeographical infor- Collinsium (Xiaoshiba biota); the latter strengthens the hypothesis mation at a high taxonomic level. that these armoured lobopodians are stem-group onychophorans (Yang et al. 2015). Problematica

Myoscolex Some controversial animals documented from other Cambrian Konservat-Lagerstätten also occur in the EBS, but are typically Myoscolex ateles (Fig. 5c) represents a genus known only from the very rare, known only from a few specimens. These include chan- EBS. It was originally interpreted as an annelid (Glaessner 1979) celloriids, represented by a species possibly belonging to based on its segmented body. New material, which included the (Bengtson & Collins 2015; Fig. 6d), and rotadiscids, first example of phosphatized muscle tissue then known from the with a close affinity to Pararotadiscus (Zhu et al. 2002; Fig. 6g); Cambrian, prompted a reinterpretation as a relative of the Burgess Bengtson & Collins (2015) and Caron et al. (2010) have discussed Shale stem-group arthropod Opabinia (Briggs & Nedin 1997). affinities of chancelloriids and rotadiscids, respectively. However, This drew on structures identified as a proboscis, three possible the EBS has revealed an unusual taxon (informally referred to as eyes, and flaps associated with the body segments. However, a ‘petalloid’; Fig. 6h) that is relatively common and unlike anything subsequent study reasserted an annelid identity (Dzik 2004), found in other Burgess Shale-type biotas. Its bract-like elements emphasizing rod-shaped phosphatized structures on the lateral and are superficially similar to those of Dinomischus (Conway Morris ventral parts of each body segment that were interpreted as chae- 1977; Chen 2004), but the EBS taxon lacks a calyx and stem. tae. New specimens under study are suggestive of a position on the stem of Euarthropoda. Palaeoecology (Cycloneuralia) The animal community entombed within the EBS Konservat- Lagerstätte appears to have an ecological structure similar to that of Palaeoscolecids are a group of worms with a robust, annulated typical Burgess Shale-type biotas (e.g. Caron & Jackson 2008; Peel cuticle that bears rows of ornamented . They are known & Ineson 2011; Zhao et al. 2014), represented by an autochthonous from many Cambrian Konservat-Lagerstätten, either as whole- (in situ) assemblage of benthic inhabitants, plus transported indi- body compression fossils or as secondarily phosphatized (Orsten- viduals of other benthic, nektic and pelagic species (discussed fur- type) microfossils. The structure of the protrusible proboscis is ther below). The benthos is dominated by the trilobite Estaingia critical to recognizing affinities to Cycloneuralia, the extant clade bilobata, occurring in numbers of up to 300 individuals per square or grade of moulting worms that includes priapulids, nematodes metre (see density in Fig. 3j), including in situ moult ensembles. and nematomorphs (Wills et al. 2012). A large in The other relatively abundant benthic taxa include (to a much lesser the EBS was originally named Palaeoscolex antiquus by Glaessner extent) the trilobite Redlichia takooensis, the palaeoscolecid (1979), but the combined information from soft anatomy and orna- Wronascolex antiquus and sponges, with the remainder being very ment of the sclerites prompted reclassification as Wronascolex, a rare (e.g. several artiopodan arthropods, lobopodians, , genus originally described from Siberia (García-Bellido et al. brachiopods, hyoliths and chancelloriids; see Box 3). The other 2013b). Specimens of W. antiquus (Fig. 5d) preserve the scalids prevalent faunal elements of the EBS are represented by taxa that (teeth) on the proboscis, the gut and the hooks at the posterior end had probable pelagic, nektic or nektobenthic life modes, suggestive of the body; the largest specimen reaches a length of 37 cm. A of a well-oxygenated water column. Some of the more common second, rare species in the EBS, Wronascolex iacoborum, is distin- forms include a variety of arthropods, especially ‘bivalved’ taxa guished by differences in the body annulation and the density of such as Isoxys and Tuzoia (García-Bellido et al. 2009; see also sclerites on the annulations. Vannier et al. 2007, 2009), Anomalocaris (Paterson et al. 2011; Daley et al. 2013), and, to a lesser extent, cheliceriform and ‘great Spiralians (‘lophotrochozoans’) appendage’ arthropods (Edgecombe et al. 2011; Paterson et al. Representatives of this group are rare in the EBS. Members 2015), and animals such as Myoscolex and the vetulicolian include: linguliformean brachiopods, such as eoobolids and bots- Nesonektris (Briggs & Nedin 1997; García-Bellido et al. 2014). fordiids (Fig. 6a), the latter exemplified by a species attributed to The very limited diversity of autochthonous (in situ) benthic Diandongia from Chengjiang (Zhang et al. 2003, 2008); a poly- inhabitants and lack of bioturbation in the EBS, coupled with the chaete annelid with possible affinities to Burgessochaeta (Fig. 5e; dominance of Estaingia bilobata, may be clues in deciphering the Eibye-Jacobsen 2004); and hyolith molluscs (Fig. 6b). conditions on the seafloor. A similar ecological abundance of a sin- Vetustovermis planus (Fig. 6c) was described from a single EBS gle trilobite species has been well documented from the Cambrian specimen, an elongate oval body 75 mm long, originally inter- Wheeler Formation of Utah (Gaines & Droser 2003, 2005, 2010). preted as an annelid (Glaessner 1979). Better preserved specimens Here, Elrathia kingii occurs in densities of up to 500 individuals per from Chengjiang, assigned to the same species, revealed a head square metre and is interpreted as being an inhabitant of the exaero- with eyes and a pair of tentacles, and showed that the supposed bic zone, a transitional area of the seafloor between dysoxic and body segments are transverse bars reinterpreted as gills (Chen truly anoxic bottom waters. Estaingia from the EBS may have et al. 2005). Recent discussion has focused on the likely synonymy occupied the same ecological niche. Low-oxygen conditions in the Downloaded from http://jgs.lyellcollection.org/ by guest on September 24, 2021

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Fig. 5. (a, b) Luolishaniid lobopodian; (a) part (SAM P14848a); (b) counterpart showing detail of claw (SAM P14848b). (c) Myoscolex ateles (SAM P47027a). (d) Wronascolex antiquus (SAM P45224a). (e) annelid (SAM P46333a). Scale bars: (a, c, e) 5 mm; (b) 500 µm; (d) 20 mm. Downloaded from http://jgs.lyellcollection.org/ by guest on September 24, 2021

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Fig. 6. (a) Botsfordiid (SAM P44242a). (b) Ribbed hyolith mollusc (SAM P14805a). (c) Vetustovermis planus (SAM P46982b). (d) Chancelloriid (SAM P51310a). (e) Leptomitid (SAM P45545a). (f) Hamptoniid sponge (SAM P45915). (g) Rotadiscid (SAM P45196). (h) ‘Petalloid’ (SAM P45583). Scale bars: (a) 3 mm; (b, f–h) 5 mm; (c–e) 10 mm. Downloaded from http://jgs.lyellcollection.org/ by guest on September 24, 2021

Emu Bay Shale Konservat-Lagerstätte 9 bottom waters may also explain the paucity of many other motile of the trilobite Estaingia preserved dorsum-down throughout the benthic organisms, and the extreme rarity or total absence of most Konservat-Lagerstätte interval; as confirmed by stratigraphic ‘way- fixosessile taxa (e.g. brachiopods and echinoderms, respectively); up’ evidence in the sections; for example, load structures (see although the latter could also be due to the overall high, often turbid Gehling et al. 2011). Preliminary data indicate that on average, c. sedimentation rates evident in the EBS. The rarer motile benthic 75% of individuals within the mudstone horizons are preserved in taxa most probably represent individuals that were either trans- this orientation. Specimens of Redlichia takooensis are also typi- ported from their living environment (e.g. the trilobite Balcoracania cally oriented in this manner. A likely explanation for this phenom- dailyi, which typically inhabits shallow water, marginal marine set- enon (see Paterson et al. 2007) is that inversion resulted from decay tings; Paterson et al. 2007) or vagrants that lived near the boundary gases building up beneath carcasses, causing them to become buoy- of the exaerobic zone and were more tolerant of the harsh low- ant and eventually overturn (Babcock & Chang 1997). This sce- oxygen conditions. The more common palaeoscolecids (particu- nario is supported by the exaerobic zone hypothesis (discussed larly W. antiquus) and leptomitids may have also been dysaerobic above), whereby inhabitants could have asphyxiated en masse dur- specialists, as their modern phylogenetic and ecological analogues ing an intermittent landward shift of the oxycline, leaving them to (e.g. priapulids and demosponges, respectively) are known to live decay on the substrate in the absence of benthic scavengers or bio- under similar oxygen conditions (Oeschger et al. 1992; Levin 2003; turbators; as mentioned above, there is no clear evidence of biotur- Mills et al. 2014; and references therein). However, the ubiquitous bation in the EBS Konservat-Lagerstätte interval. Mass asphyxiation occurrence of Cambrian palaeoscolecids (especially Wronascolex; events owing to a fluctuating oxycline, which would have also García-Bellido et al. 2013b) and demosponges (Carrera & Botting affected parts of the water column, may also explain the abundance 2008) in various palaeoenvironmental settings worldwide, in addi- of free-swimming taxa within the EBS mudstones, especially tion to the supposed burrowing habit of palaeoscolecids (Huang Isoxys communis, the most common soft-bodied species in the et al. 2014), suggests that perhaps the EBS forms occupied the EBS. Such forms are frequently preserved in either dorso-ventral or periphery of the exaerobic zone where the sediment–water interface lateral aspect (with the largest and flattest surface area oriented par- was more oxygenated and were subsequently transported a short allel to bedding), suggestive of gravitational settling (see Zhang & distance into an optimal preservational setting (Gaines 2014). Hou 2007), as opposed to turbid burial, which can result in oblique orientations (Caron & Jackson 2006; Gabbott et al. 2008; Gaines 2014). In the case of the free-swimming arthropods, the abundance Box 3. Outstanding questions and orientation of their remains may also be a consequence of moulting, as indicated by the common occurrence of ‘bivalved’ Certain taxonomic groups that are usually represented in carapaces without trunks, and isolated elements (especially frontal Cambrian Burgess Shale-type biotas are either very scarce in appendages and body flaps) of Anomalocaris. the EBS (e.g. annelids, lobopodians) or wholly lacking (e.g. The EBS mudstones containing trilobites, especially those hori- echinoderms). Teasing out whether these rare occurrences or zons comprising unequivocal in situ moult ensembles of Estaingia absences are biogeographically, environmentally, ecologi- and Redlichia, and other free-swimming forms that are commonly cally and/or taphonomically controlled (e.g. annelids are preserved in prone, supine or lateral positions seem to indicate unknown from Chengjiang and are represented in the short periods of quiescent substrate conditions (affected by a fluc- Guanshan biota by a single specimen, but are well represented tuating oxycline) prior to frequent burial events. The often poor in the Burgess Shale and Sirius Passet biotas; Parry et al. fidelity or partial or total absence of certain anatomical structures 2014; Liu et al. 2015) remains an important challenge. One of (e.g. the appendages of some artiopodans; Paterson et al. 2010, the biggest questions surrounding the EBS Konservat- 2012) may also relate to decay rate versus pre-burial residence Lagerstätte is how the unusual combination of a nearshore time on the seafloor (Zhao et al. 2009; O’Brien et al. 2014), but the palaeoenvironmental setting and the variety of preservational relationships between preservational fidelity, original histology modes seen in EBS fossils, such as the 3D relief of soft-bod- and host sediment types (including mineralogy) should also be ied taxa and the range of early diagenetic mineralization of considered (Gaines et al. 2012b; Wilson & Butterfield 2014). labile and recalcitrant tissues, relates to typical Burgess Shale- However, several interbedded siltstone and fine sandstone layers type deposits, if at all (Gaines 2014). This will require detailed often entomb complete trilobites and vetulicolians in chaotic ori- microstratigraphic, sedimentological and geochemical analy- entations, again contrasting with the dorso-ventral or lateral orien- ses, including drill core samples. tations of these animals in mudstones, respectively; for example, the preservation styles of EBS vetulicolians in siltstones (García- Bellido et al. 2014, fig. 1A–F) compared with those in mudstones Preservation of Emu Bay Shale fossils (García-Bellido et al. 2014, fig. 4C). This suggests that intermit- Most studies on the taphonomy of EBS fossils have focused on the tent sediment gravity flows not only swept up members of the ben- diagenetic aspects, specifically the early diagenetic mineralization thos, but captured free-swimming taxa as well, with only the of soft tissues, which is particularly prominent and varied com- biomineralized or heavily sclerotized forms preserving in these pared with other documented Cambrian Konservat-Lagerstätten coarser sediments. (Gaines 2014), but also late-stage diagenetic mineralization in the Understanding the preservational modes of soft-bodied fossils form of pink to white fibrous calcite that can replicate fossils in the EBS is hindered by the extensive surficial weathering, as is (Nedin 1997). Examples of the former process include phosphati- the case in deposits such as those of Chengjiang (Gabbott et al. zation of labile tissues such as muscle (Briggs & Nedin 1997; 2004; Forchielli et al. 2014). This was one of the reasons why Nedin 1997) and gut structures (García-Bellido et al. 2009, 2013b; Gaines (2014) excluded the EBS as a Burgess Shale-type deposit, Edgecombe et al. 2011; Paterson et al. 2012), but also recalcitrant which is defined by the occurrence of soft-bodied fossils preserved extracellular cuticle (Lee et al. 2011; Paterson et al. 2011); the last as 2D, primary carbonaceous remains. This strict definition of can also be pyritized (see Box 2). ‘carbonaceous compression’ fossils means that the EBS fails on Although there is still much work to be done in understanding both counts, as (1) the fossils show no signs of carbon films and (2) these modes of preservation during diagenesis, various biostrati- recalcitrant tissues in many soft-bodied taxa (such as Isoxys, nomic characteristics also require further investigation (Box 3). The Tuzoia, non-trilobite artiopodans and even Anomalocaris frontal most conspicuous of these is the prevalence of complete specimens appendages) have some degree of three-dimensionality (e.g. Downloaded from http://jgs.lyellcollection.org/ by guest on September 24, 2021

10 J. R. Paterson et al.

Fig. 3b, f and i). Whereas the absence of carbonaceous remains Carrera, M.G. & Botting, J.P. 2008. Evolutionary history of Cambrian spicu- may simply be the result of weathering, the 3D nature of soft-bod- late sponges: Implications for the Cambrian Evolutionary Fauna. Palaios, 23, 124–138. ied fossils within the EBS mudstones, excluding specific anatomi- Chen, J. 2004. The Dawn of Animal World. Jiang Science and Technology cal structures replicated by authigenic minerals (e.g. mid-gut Press, Nanjing. glands), implies a different preservational mode from that of Chen, J., Huang, D. & Bottjer, D.J. 2005. An Early Cambrian problematic fossil: Vetustovermis and its possible affinities. Proceedings of the Royal Society of Burgess Shale-type deposits. This may be due, in part, to the pres- London, Series B, 272, 2003–2007. ence of a silt fraction within the EBS mudstones that is otherwise Conway Morris, S. 1977. A new entoproct-like organism from the Burgess lacking in Burgess Shale-type clay-rich beds containing 2D carbo- Shale of British Columbia. Palaeontology, 20, 833–845. naceous compression fossils (Gaines et al. 2012b). Conway Morris, S. & Jenkins, R.J.F. 1985. Healed injuries in Early Cambrian trilobites from South Australia. Alcheringa, 9, 167–177. Conway Morris, S. & Robison, R.A. 1988. More soft-bodied animals and algae Summary from the Middle Cambrian of Utah and British Columbia. University of Kansas, Paleontological Contributions, 122. The Emu Bay Shale Konservat-Lagerstätte provides critical informa- Dai, T. & Zhang, X. 2012. Ontogeny of the trilobite Estaingia sinensis (Chang) tion on the evolution, biogeography and ecology of Cambrian faunas from the lower Cambrian of South China. Bulletin of Geosciences, 87, 151– 158. from an East Gondwanan perspective. Overall, the EBS community Daily, B., Moore, P.S. & Rust, B.R. 1980. Terrestrial–marine transition in the appears to have been living in and under a well-oxygenated water Cambrian rocks of Kangaroo Island, South Australia. Sedimentology, 27, column (within the photic zone) that was often subjected to a fluctu- 379–399. ating oxycline. This resulted in the development of an exaerobic zone Daley, A.C., Paterson, J.R., Edgecombe, G.D., García-Bellido, D.C. & Jago, J.B. 2013. New anatomical information on Anomalocaris from the Cambrian on the seafloor (below storm wave base) that was inhabited by dys- Emu Bay Shale of South Australia and a reassessment of its inferred preda- aerobic specialists, but also acted as a preservational trap for many tory habits. Palaeontology, 56, 971–990. other benthic, nektobenthic and pelagic taxa that were transported Dzik, J. 2004. Anatomy and relationships of the Early Cambrian worm Myoscolex. Zoologica Scripta, 33, 57–69. into or settled down in this setting. Although the EBS contains a typ- Edgecombe, G.D., García-Bellido, D.C. & Paterson, J.R. 2011. A new lean- ical Burgess Shale-type biota, a unique combination of preservational choiliid megacheiran arthropod from the lower Cambrian Emu Bay Shale, modes in a nearshore setting sets it apart from other Burgess Shale- South Australia. Acta Palaeontologica Polonica, 56, 385–400. type deposits. It thus holds potential for reshaping our understanding Eibye-Jacobsen, D. 2004. A reevaluation of Wiwaxia and the polychaetes of the Burgess Shale. Lethaia, 37, 317–335. of the exceptional preservation of Cambrian soft-bodied fossils. Forchielli, A., Steiner, M., Kasbohm, J., Hu, S. & Keupp, H. 2014. Taphonomic traits of clay-hosted early Cambrian Burgess Shale-type fossil Lagerstätten Acknowledgements and Funding in South China. Palaeogeography, Palaeoclimatology, Palaeoecology, 398, 59–85. Emu Bay Shale research has been supported by grants from the Australian Gabbott, S.E., Hou, X., Norry, M.J. & Siveter, D.J. 2004. Preservation of Early Research Council (LP0774959, DP120104251, FT120100770, FT130101329), Spanish Research Council (CGL2009-07073, CGL2013-48877-P) and National Cambrian animals of the Chengjiang biota. Geology, 32, 901–904. Geographic Society Research & Exploration (#8991-11), with additional finan- Gabbott, S.E., Zalasiewicz, J. & Collins, D. 2008. Sedimentation of the cial assistance from Beach Energy Ltd and the South Australian Museum. Phyllopod Bed within the Cambrian Burgess Shale Formation of British SeaLink has provided logistical support. We are grateful to the Buck family for Columbia. Journal of the Geological Society, London, 165, 307–318, http:// access to the field area. We thank our friends and colleagues (in alphabetical dx.doi.org/10.1144/0016-76492007-023. order) R. Atkinson, M. Binnie, G. Brock, A. Camens, A. Daley, R. Gaines, M. Gaines, R.R. 2014. Burgess Shale-type preservation and its distribution in Gemmell, J. Holmes, K. Kenny, P. Kruse, J. Laurie, X. Ma, B. McHenry, M. space and time. In: Laflamme, M., Schiffbauer, J.D. & Darroch, S.A.F. Mills, L. Reid, D. Rice, N. Schroeder, E. Thomson and members of the South (eds) Reading and Writing of the Fossil Record: Preservational Pathways Australian Museum Waterhouse Club for assistance in the field and laboratory, to Exceptional Fossilization. Paleontological Society Papers, 20, 123–146. as well as providing fruitful discussions over the years. Thanks go to three anon- Gaines, R.R. & Droser, M.L. 2003. Paleoecology of the familiar trilobite ymous referees for providing helpful reviews of the paper, and to R. Gaines for Elrathia kingii: An early exaerobic zone inhabitant. Geology, 31, 941–944. commenting on an earlier draft. Gaines, R.R. & Droser, M.L. 2005. 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