Gondwana Research 19 (2011) 310–326Contents lists available at ScienceDirect Gondwana Research j o u r n a l h o m e p a g e : w w w. e l s e v i e r. c o m / l o c a t e / g r The oldest bivalved arthropods from the early Cambrian of East Gondwana: Systematics, biostratigraphy and biogeography a, b,c a d Timothy P. Topper , Christian B. Skovsted , Glenn A. Brock , John R. Paterson a Department of Biological Sciences, Macquarie University, NSW 2109, Australia b Department of Earth Sciences, Uppsala University, Villavägen 16, SE-752 36 Uppsala, Sweden c Department of Palaeozoology, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden d Division of Earth Sciences, School of Environmental & Rural Science, University of New England, Armidale NSW 2351, Australia article info abstract Article history: The oldest bradoriid fauna from Australia, occurring in the lower Cambrian Ajax and Wirrapowie limestones of the Flinders Received 15 February 2010 Ranges, South Australia consists of eleven taxa, including one new genus and species, Quadricona madonnae gen. et sp. nov. Received in revised form 30 April 2010 and two new species, Liangshanella circumbolina sp. nov. and Zepaera jagoi sp. nov. In the Ajax Limestone, Liangshanella Accepted 23 May 2010 Available online 4 circumbolina sp. nov. occurs c. 20 m below the FAD of the zonal trilobite Abadiella huoi. This pre-trilobitic occurrence June 2010 represents the oldest bivalved arthropod hitherto known from East Gondwana and suggests a lower Cambrian (Series 2, Stage 3) age for the assemblage. The recognition of distinct bradoriid assemblages associated with the Abadiella huoi (Atdabanian), Keywords: Cambrian Pararaia tatei, P. bunyerooensis and P. janeae (all Botoman) trilobite biozones in South Australia indicates great potential for Arthropoda future regional biostratigraphic correlation. Quantitative biogeographic analysis including new taxonomic data from the lower Bradoriida Cambrian of South Australia, highlights the strong endemism displayed by early Cambrian bradoriid communities and Phosphatocopida strengthens the close faunal affinities with South China and Antarctica. South Australia © 2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. 1. Introduction ostracods and are also not directly related to the other widespread group of Cambrian bivalved arthropods, the Phosphatocopida (see also Hinz- Bradoriids are small, bivalved, marine arthropods that formed an Schallreuter and Schallreuter, 2009). Current evidence suggests important component of Cambrian faunal assemblages before their extinction phosphatocopids are a sister group to the Eucrustacea, a group that includes in the middle Ordovician (e.g. Melnikova et al., 1997; Siveter and Williams, all crustacean taxa with extant derivatives (Maas et al., 2003; Jones and 1997; Hou et al., 2002; Vannier et al., 2005; Zhang, 2007; Jones and Kruse, Laurie, 2006; Williams et al., 2007, 2008). The possession of five head 2009). The group had a worldwide distribution and are present in all of the appendages in Kunmingella, accompanied by endopods that consist of fewer major Cambrian Lagerstätten, including the Buen Formation (Siveter et al., than seven podomeres indicate that bradoriids most probably represent stem 1996), Qiongzhusi Formation (Hou and Bergström, 1991; Hou et al., 2002), group crustaceans (Hou et al., 1996, 2010; Shu et al., 1999; Williams et al., Burgess Shale Formation (Conway Morris, 1986; Siveter and Williams, 1997) 2007, 2008). and the Alum Shale Formation (e.g. Müller, 1964, 1979, 1982; Maas et al., 2003). Historically, bradoriids were suggested to be the ancestors of ostracods A total of 41 bradoriid and 12 phosphatocopid genera have been described (Sylvester Bradley, 1961; Hinz-Schallreuter, 1993a, b, 1999; Zhang and Pratt, from latest early and middle Cambrian [Series 2 (Stage 4) and Series 3 (Stage 1993; McKenzie et al., 1999; Gozalo and Hinz-Schallreuter, 2002), but 5 to Guzhangian)] equivalent successions across central and northern investigation of appendage morphology in exceptionally preserved specimens Australia (Öpik, 1961, 1963, 1967, 1968; Fleming, 1973; Jones and of Kunmingella Huo, 1956 and Kunyangella Huo, 1956 from China (Hou et McKenzie, 1980; Hinz, 1991, 1992a,b, 1993; Hinz and Jones, 1992; Hinz- al., 1996, 2002; Shu et al., 1999; Hou et al., 2010) suggests that bradoriids Schallreuter, 1993a, 1999; Hinz-Schallreuter and Jones, 1994; Jones and share few synapomorphies with Laurie, 2006; Jones and Kruse, 2009). In stark contrast, the diversity and abundance of bivalved arthropods from the thick lower Cambrian successions of South Australia have, until recently, been seriously neglected. The authors have recently documented 13 bradoriid and a single phosphatocopid species from the lower Cambrian (Series 2, Stage 4) Mernmerna Formation in the Corresponding author. Tel.: +61 2 9850 7719; fax: +61 2 9850 6053. E-mail Arrowie Basin (Skovsted address:
[email protected] (T.P. Topper). 1342-937X/$ – see front matter © 2010 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.gr.2010.05.012 T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 311 et al., 2006; Topper et al., 2007) adding substantially to the diversity of bivalved arthropods previously documented from the Parara Limestone in the The carbonate-dominated Ajax Limestone is approximately 280 m thick at Bivalved Stansbury arthropods Basin co-occur (Chapman, 1918;with the first Bengtson trilobites et al., 1990).on several continents AJX-M and conformably overlies the siliciclastic Parachilna Formation (Fig. (Williams et al., 2007), but appear slightly earlier than the first recorded 2A). The lower 120 m of AJX-M section is dominated by massive trilobite (Abadiella) in southern China (Hou et al., 2002; Williams et al., stromatolitic boundstones and dolomitised bioclastic and cryptalgal, 2007; Zhang, 2007; Zhang, et al., 2008). The faunal abundance and early laminated limestones. Shelly fossils are generally absent from this part of the stratigraphic occurrence of bivalved arthropods in South China has prompted section. The upper 160 m of section consists of richly fossiliferous (frequently some authors (Hou et al., 2002; Williams et al., 2007) to suggest that silicified) beds including grey to buff coloured, thin nodular limestone beds bradoriids may have originated in the South China region. The oldest and red, massive, bioclastic limestone with minor nodular interbeds (Skovsted bradoriids previously documented from South Australia were possible et al., 2009). svealutids from the lower Cambrian (Atdabanian equivalent) Parara Limestone at Curramulka Quarry on Yorke Peninsula (Chapman, 1918). The second section, ER-9, was measured through the Wirrapo-wie Studies of small shelly fossil (SSF) assemblages from the Parara Limestone Limestone and conformably overlying Mernmerna Formation outcropping on on Yorke Peninsula have also estab-lished the presence of species belonging the eastern limb of a north plunging syncline in the northern Elder Range to the Hipponicharionidae (Albrunnicola bengtsoni Hinz-Schallreuter, 1993a) (Figs. 1C, 2B). The base of the ER-9 section is at coordinates 31°40'2.6"S; and Monaster-iidae (Epactridion portax Bengtson in Bengtson et al., 1990). 138°26'11.5"E [WGS84]. The upper 47 m of massive, algal dominated, These bradoriids occur within the Abadiella huoi trilobite Biozone, which mottled and ribboned carbo-nates of the Wirrapowie Limestone was sampled broadly correlates with the Abadiella trilobite Zone in South China (Jell in at section ER-9, with sampling continuing into the Mernmerna Formation. Bengtson et al., 1990; Steiner et al., 2001; Zang et al., 2001; Paterson and The conformably overlying Mernmerna Formation reaches a maximum Brock, 2007) and the Atdabanian Stage of Siberia (Zhuravlev and Gravestock, thickness of 191 m in ER-9 and is dominanted by argillitic to nodular 1994; Zhuravlev, 1995). The oldest phosphatocopid in Australia (Indianidae limestones interbedded with calcareous mudstone in the lower two-thirds of gen. et sp. indet. A) has also been documented from the Abadiella huoi the exposure, grading into a calcareous mudstone with minor limestone Biozone in the Ajax Limestone, South Australia (Bengtson et al., 1990). nodules in the upper 60 m of outcrop. The majority of bivalved arthropod specimens are derived from the upper Wirrapowie Limestone; only a few specimens are present in the overlying Mernmerna Formation (Fig. 2B). Detailed collections along measured stratigraphic sections through the Ajax Limestone reveal that the oldest bradoriid occurs c. 20 m below the first appearance datum (FAD) of the zonal trilobite Abadiella huoi. This pre- trilobitic occurrence suggests an early Series 2, Stage 3 age and represents the 2.2. Biostratigraphy and age oldest bivalved arthropod hitherto known from the lower Cambrian of East Gondwana. In a further contribution to the understanding of early Cambrian The International Submission on Cambrian Stratigraphy (ISCS) has bivalved arthropod biodiversity from East Gond-wana, three new bradoriid recently adopted a four-Series, ten-Stage framework for the Cambrian species are described herein from the lower Cambrian Ajax Limestone (Series chronostratigraphic timescale (Babcock et al., 2005; Babcock and Peng, 2007; 2, Stage 3) in the Mount Scott Range and the upper part of the Wirrapowie Peng and Babcock, 2008; Babcock et al., 2009). Whilst the majority of stages Limestone (Series 2, Stages 3-4) in the Elder Range. The new data, when are undefined and key horizons are yet to be resolved (Babcock and Peng, combined with the recent documentation of a number of South Australian 2007), two Series (Terreneuvian and Furongian) and four stages (Fortunian, bivalved arthropod assemblages (e.g. Skovsted et al., 2006; 2009; Topper et Drumian, Guzhangian and Paibian) have been ratified (Babcock et al., 2009). al., 2007) provides the opportunity to shed new light on the biogeography, The traditional lower Cambrian has been replaced by two Series and four biodiversity and evolution of early Cambrian South Australian assemblages. A Stages, with only the base of the Cambrian system, currently defined (Brasier quantitative analysis of Australian and East Gondwanan bradoriid et al., 1994; Landing, 1994; Landing et al., 2007). biogeography is provid-ed, using a pair-group cluster analysis for presence- absence data (Raup-Crick similarity index) utilising the statistical package ‘PAST’ (Hammer et al., 2001). The fossiliferous part of the Ajax Limestone as represented in section AJX-M broadly coincides with the currently unnamed Cambrian Series 2, Stages 3-4. These stages are approximately equivalent to the Atdabanian and Botoman of the Siberian stage nomenclature. The FAD of Abadiella huoi, the eponym of the oldest Australian trilobite Biozone, at 137 m above the base of 2. Localities, biostratigraphy and age the section marks the first occurrence of a trilobite taxon in the Ajax Limestone, and most likely falls within Cambrian Series 2, Stage 3 (Babcock 2.1. Localities et al., 2005; Babcock and Peng, 2007; Babcock et al., 2009). Jell (in Bengtson et al., 1990) has described fragmentary specimens of “Redlichiid indet. 3” – The bivalved arthropods described herein were collected from two lower possibly representing a species of Redlichia (cf. Paterson and Brock, 2007) – Cambrian (Series 2, Stages 3-4) stratigraphic sections in the Arrowie Basin from a stratigraphic level that coincides with the Pararaia tatei Biozone in the (Figs. 1, 2). The first stratigraphic section (AJX- Ajax Limestone. Thus, the upper Ajax Limestone that equates to the P. tatei M) was measured through the Ajax Limestone outcropping in the Mount Biozone may be early Stage 4 in age, given that one of the proposed candidate Scott Range, northern Flinders Ranges, South Australia (Figs. 1B, 2A). The horizons to mark the base of this stage is the FAD of Redlichia (Babcock et base of the AJX-M section is located at coordinates 30°35'49" S, 138°19'59.3" al., 2005; Babcock and Peng, 2007). Consequently, the entire Ajax Limestone E [WGS84] and is equivalent to section M of Gravestock (1984, fig. 2). The at section AJX-M may potentially span from the late Terreneuvian Series, stratigraphy and sedimentology of the Ajax Limestone at section AJX-M has Stage 2 through to the unnamed Cambrian Series 2, Stage 4. Ongoing been summarised by Brock et al. (2006) and Skovsted et al. (2009); the latter investigations to determine the FAD and LAD of SSFs, brachiopods and paper documents specimens of the early Cambrian stem group brachiopod molluscs (see Topper et al., 2009), in conjunction with chemostratigraphic Mickwitzia from the upper part of the section. analyses, will help to constrain the position of Series and Stage boundaries in the lower Cambrian succession of South Australia. 312 T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 Fig. 1. A, locality map showing study areas, the Mount Scott and Elder ranges, Flinders Ranges, South Australia. B, simplified geological map of the Mount Scott Range showing the positions of section AJX-M through the Ajax Limestone. C, geological map of the Elder Range showing position of the ER9 section through the Hawker Group. The AJX-M section contains an abundance of silicified, phos-phatic or bivalved arthropods documented through the entire AJX-M stratigraphic phosphatised macro- and microfossils, including species of trilobites, section are plotted against the lithostratigraphic column in Fig. 2A. Two lingulate and rhynchonelliform brachiopods, molluscs, tommotiids, distinct trilobite biozones can be differentiated in the AJX-M section (see problematic small shelly fossils, spongio-morphs, plus eight species of Jago et al., 2006 for the most recent review of the biostratigraphy of the lower bivalved arthropods documented herein. Archaeocyaths from the AJX-M Cambrian of South Australia). The first appearance datum (FAD) of the index section were described by Gravestock (1984; his section M) and Bengtson et trilobite taxon Abadiella huoi at 137 m true thickness above the base of the al. (1990, fig. 6) documented a variety of taxa including trilobites, molluscs, section defines the base of the eponymous biozone. The LAD of A. huoi sponge spicules and SSFs from spot localities along this creek section. occurs at 197.67 m above the base of the section indicating that the entire A. Recently, Skovsted et al. (2009) described the first East Gondwanan huoi Biozone is 60.67 m thick in the section. The base of the succeeding occurrence of the stem group brachiopod Mickwitzia from this locality. The Pararaia tatei trilobite Biozone, defined by the FAD of the stratigraphic ranges of trilobites and eponymous species, is located at T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 313 Fig. 2. A, stratigraphic ranges of trilobite and bivalved arthropod taxa through the Ajax Limestone in the AJX-M section, Mount Scott Range. B, stratigraphic ranges of stem group brachiopod, trilobite, and bivalved arthropod taxa through the upper Wirrapowie Limestone and Mernmerna Formation in the ER-9 section in the Elder Range. 199.63 m (true thickness) above the base of the section and 1.96 m above the stromatolitic limestones representing the top 40 metres of section AJX-M, and last appearance datum (LAD) of Abadiella huoi. This leaves a small the presence of the normally much older tommotiids Micrina etheridgei and stratigraphic gap of 1.96 m, where it is difficult to ascertain the exact Dailyatia ajax in these beds strongly suggests substantial reworking (or fault boundaries of the two trilobite biozones. The Pararaia tatei Biozone represents repetition) in this interval. at least a 39.7 m stratigraphic interval in the upper half of the section, with the The FAD of the oldest bradoriid taxon, Liangshanella circumbolina sp. LAD of the eponymous species occurring at 239.33 m above the base of the nov., occurs at 117 m above the base of the section, c. 20 m below the FAD of section, which equates with a distinctive erosional surface undoubtedly Abadiella huoi. Despite detailed sampling throughout the AJX-M section, we reflecting a short hiatus in sedimentation. No trilobite specimens were acknowledge that pervasive dolomitisation has destroyed original fabrics, and recovered from the red and grey dolomotised, so uncertainties remain about the presence (or not) of trilobites (and other fossils) 314 T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 in the lower dolomitised part of the Ajax Limestone succession. If the pre- a ‘western’ faunal realm, characterized by the genera Indiana and Bradoria trilobitic occurrence of Liangshanella circumbolina sp. nov. is accepted, then and an ‘eastern’ faunal realm, characterized by the so called ‘alutids’ (e.g. this suggests an early Series 2, Stage 3 age for this taxon, representing the Zepaera, Liangshanella and Kunmingella). The term ‘alutids’ was used to oldest bivalved arthropod hitherto described from the lower Cambrian describe bradoriids with apparent outer border structures on their shields (Shu succession of South Australia. The rest of the bivalved arthropod assemblage and Chen, 1994). However, recent taxonomic revisions have demonstrated (7 species in total – see Fig. 2A) from AJX-M, correlates with the A. huoi that the nominate taxa Aluta should be considered a nomen dubium and the Biozone and is still significantly older that the bivalved arthropods recently term ‘alutids’ be abandoned (Siveter and Williams, 1997; Williams et al., documen-ted from the Mernmerna Formation (P. bunyerooensis and P. janeae 2007). biozones) in the central Flinders Ranges by Skovsted et al. (2006) and Topper et al. (2007). Only two species, Mongolitubulus squamifer Missarzhevsky, Palaeobiogeographic studies have tended to concentrate on comparisons 1977 and Zepaera sp. range into the succeeding Pararaia tatei Biozone (Fig. of Cambrian bradoriid biogeographical patterns with that of trilobites (e.g. 2A). Melnikova et al., 1997; Hou et al., 2002; Williams et al., 2007; Zhang, 2007). The ‘western’ faunal realm identified by Shu (1981) is generally associated Two species that occur in the Ajax Limestone have been previously with cool to cold water systems broadly mirroring the Olenellid trilobite documented from South Australia: Dabashanella hemicyclica Huo, Shu and Province whilst the ‘eastern’ realm reflects warm water, largely equatorial Fu in Huo et al., 1983, from the Pararaia bunyerooensis Biozone of the communities equivalent to the Redlichiid trilobite province (Melnikova et al., Mernmerna Formation (Skovsted et al., 2006) and Mongolitubulus squamifer 1997; Hou et al., 2002; Williams et al., 2007). Bradoriid taxa characteristic of from the P. janeae Biozone of the Mernmerna Formation (Topper et al., 2007). the Redlichiid trilobite province include Shangsiella, Comptaluta and Unfortunately, since both are long-ranging taxa they have limited Zepaera, whereas others, such as Indiana, Walcottella and Dielymella, biostratigraphic value. Other long-ranging taxa with low biostrati-graphic epitomize the Olenellid trilobite province. The trilobite-based Acadobaltic utility in the AJX-M and ER-9 sections include generic forms Euzepaera, Province sensu Sdzuy (1972), a region that includes Baltica, Avalonia, Zepaera. and Mongolitubulus. Specimens of each genus from AJX-M and Armorica and Morocco also displays strong provinciality. This is supported ER-9 are either too poorly preserved (e.g. Euzepaera sp. and Zepaera sp.) or by the presence of genera such as Beyrichona Matthew, 1886, Indiana and display substantial morphological variation and fragmentation (e.g. Wimanicharion Hinz-Schallreuter, 1993a, which are almost exclusively Mongolitubulus sp.) that pre-cludes assessment at species level. known from these areas in the late early and middle Cambrian (Streng et al., 2008). However, uncertainties have arisen regarding the degree of differentiation between the olenellid and redlichiid provinces (Zhang, 2003; The bradoriid assemblage at section ER-9 is mainly restricted to the Palmer, 2005). Zhang (2003) and Palmer (2005) have noted that some early Wirrapowie Limestone, which equates to the basal 47 m (true thickness) of Cambrian trilobites from both provinces display similarities that suggest that the section. The dearth of trilobite specimens throughout the ER-9 faunal provinciality was not as well developed in the early Cambrian. stratigraphic section does not allow precise placement of the zonal trilobite boundaries. The first trilobite recovered in the section, Alanisia guillermoi Richter and Richter, 1940 occurs 106 m above the base of the section and is generally taken to represent the Pararaia tatei Biozone (Jell in Bengtson et al., The use of the term ‘western’ and ‘eastern’ was abandoned by Shu and 1990). Although no trilobites indicative of the Abadiella huoi Biozone were Chen (1994) who established the “European” realm and the “4A” realm, based recovered from the basal 47 m of the ER-9 section, these beds do contain predominantly on temperature-latitude gradients. The “European” faunal typical Atdabanian representatives including the tannuoliniid tommotiid realm consisted of Baltica, Avalonia, northern France and North Africa and Micrina etheridgei Tate, 1892 and the paterinid brachiopod Askepasma cf. represented a cool to cold water fauna and the “4A” faunal realm consisted of toddense, which widely co-occur with Abadiella huoi elsewhere in the Laurentia, Asia (North and South China), Siberia, Tarim, Kazakhstan, Arrowie Basin and provide strong evidence in support of an A. huoi Biozone Mongolia, Australia and Antarctica, representing an equatorial, warm water equivalent age for the bradoriid assemblage in the Wirrapowie Limestone at fauna (Shu and Chen, 1994). Shu and Chen (1994) suggested a number of section ER-9. The occurrence of Quadricona madonnae gen. et sp. nov. possible dispersal routes for bradoriids, including migration from South China provides additional correlation with section AJX-M and supports a A. huoi to Australia during the late early Cambrian, based on the presence of Zepaera equivalent biostratigraphic age for the assemblage. on both palaeocontinents. The late early Cambrian timing of the migration was based solely on the lack of bradoriid taxa from the early Cambrian of Australia. Zepaera has subsequently been discovered in the early Cambrian of Australia (Skovsted et al., 2006; Topper et al., 2007; herein) in conjunction Two species, Alutella sp. and Spinospitella coronata Skovsted, Brock and with a diverse suite of bradoriid genera, suggesting that if a migration event Paterson, 2006 are also present in the overlying Mernmerna Formation at ER- did occur between South China and Australia, it must have transpired much 9. Spinospitella coronata co-occurs with the P. tatei Biozone trilobite A. earlier than previously recognised. Williams et al. (2007) broadly supported guillermoi and continues to range 25 m (true thickness) above the occurrence the idea of ‘western’ and ‘eastern’ faunal realms; however, stressed that the of A. guillermoi. Alutella sp. is confined to the uppermost part of the section patterns of bradoriid biogeography was much more complicated than previous which can be confidently assigned a Pararaia janeae Biozone biostrati-graphic works indicated; they identified a number of distribution patterns and age, based on the presence of the eponym along with Serrodiscus gravestocki assemblages, reflecting tropical and temperate climates as well as those Jell in Bengtson et al., 1990, Hebediscina yuqingensis Zhang in Zhang et al., groups that had a cosmopolitan distribution. 1980, Atops rupertensis Jell, Jago and Gehling, 1992, and a possible edelsteinaspidid. 3. Biogeographic implications Williams et al. (2007) provided a detailed account of the affinities and biogeography of bradoriids for the duration of the Cambrian until their The distribution of bradoriids, and to a much lesser extent eventual extinction in the mid-Ordovician. Williams et al. (2007) reviewed phosphatocopids, has often been utilised in Cambrian palaeobio-geographical number of palaeocontinental regions the bradoriid faunas from a analyses (e.g. Melnikova et al., 1997; Siveter and Williams, 1997; Williams including Laurentia, Avalonia, Siberia, South China, central and Siveter, 1998; Hou et al., 2002). Shu (1981), in an early biogeographical review of bradoriids, identified Asia and Gondwana commenting on the palaeogeographical positions of these regions pertaining to T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 315 Fig. 3. A, reproduced cluster analysis of early Cambrian bradoriid genera conducted by Williams et al. (2007, fig. 10A, page 224). B, pair-group cluster analysis for presence-absence data (Raup- Crick similarity index, correlation coefficient 0.6587) for 60 bradoriid genera from the early Cambrian. C, pair-group cluster analysis for presence-absence data (Raup-Crick similarity index, correlation coefficient 0.6684) with Australia and Antarctica as amalgamated provinces of the palaeocontinental region of East Gondwana. bradoriid distribution. Sedimentary successions from West Gond-wana have associations between Avalonia, Laurentia, Baltica and West Gond-wana yielded cambriids from the lower Cambrian of France (Vannier et al., 2005), (Morocco and Amorica). Bradoriid assemblages from South China clustered hipponicharionids from Spain (Gozalo and Hinz-Schallreuter, 2002; Gozalo et with those of Kazakhstan as part of an eastern hemisphere, warm water fauna, al., 2004) and a number of taxa from the middle Cambrian of Morocco (Hinz- whilst Australian bradoriid data (based on two taxa) for the early Cambrian Schallreuter, 1993a). East Gondwana yields taxa from the lower Cambrian of display only weak statistical similarity to South China, Kazakhstan and Antarctica (Rode et al., 2003; Wrona, 2009) along with prolific faunas from Siberia (Fig. 3A). We have performed a number of presence-absence cluster the lower Cambrian through to the Furongian of Australia (e.g. Öpik, 1968; analyses (Fig. 3B, C) using ‘PAST’ (Raup-Crick similarity index), employing Jones and McKenzie, 1980). According to Williams et al. (2007, see table 2), the biogeographical distribution data provided by Williams et al. (2007, table at the generic level, Australia produces one of the most diverse bradoriid 2 and appendix A), but also incorporating new taxonomic data published in assemblages (23 genera documented in total) during the Cambrian to Early recent years that Ordovician interval. The large majority of East Gondwanan bradoriid taxa have been described from the Ordian and succeeding Stages across central and northern Australia (e.g. Öpik, 1968; Fleming, 1973; Hinz-Schallreuter, 1999). Previously, the Australian Ordian Stage was considered to be early Middle Cambrian (e.g. Shergold, 1996 and references therein), however evidence continues to amass suggest-ing that this stage should be regarded as latest Early Cambrian (see Laurie, 2006 and Paterson and Brock, 2007 for discussion). Consequently, all bradoriid genera described from the Ordian Stage of Australia are treated as early Cambrian in age and incorporated into the following analyses. The taxonomic diversity and biogeographic analysis of bivalved arthropods reported by Williams et al. (2007) only included two lower Cambrian (Cambrian Stage 2, Series 3-4) taxa from South Australia (Albrun-nicola bengtsoni Hinz-Schallreuter, 1993a and Epactridion portax Bengtson in Bengtson et al., 1990). Recent work by Skovsted et al. (2006), Topper et al. (2007), Wrona (2009) and herein document another thirteen bivalved arthropod genera from the lower Cambrian of South Australia and Antarctica, greatly increasing the database of early Cambrian bivalved arthropod biodiversity from East Gondwana. As part of their original evaluation of bradoriid biogeography, Williams et al. (2007, fig. 10) performed a pair-group cluster analysis using the statistical Fig. 4. A, pair-group cluster analysis for presence-absence data (Raup-Crick similarity index, package ‘PAST’, based on presence-absence data (Raup-Crick similarity correlation coefficient 0.6361) for 18 bradoriid genera from the early Cambrian, omitting index) of 32 bradoriid genera from the early Cambrian and 33 genera from the bradoriid genera that have been documented from only a single palaeoncon-tinental region. B, middle Cambrian. The cluster analysis presented by Williams et al. (2007, fig. pair-group cluster analysis for presence-absence data (Raup-Crick similarity index, correlation 10, reproduced here in Fig. 3A) indicated a wide distribution of bradoriid coefficient 0.6876) for 18 bradoriid genera from the early Cambrian, omitting bradoriid genera that have been documented from only a single palaeoncontinental region and with Australia and genera during the early Cambrian, with close faunal Antarctica as amalgamated provinces of the palaeocontinental region of East Gondwana. 316 T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 was not used in the Williams et al. (2007) analysis (e.g. Skovsted, 2006; (Fig. 3C) produces a dendrogram that is very similar to the results obtained by Skovsted et al., 2006; Topper et al., 2007; Zhang, 2007; Dies Αlvarez et al., Williams et al. (2007). The only noticeable difference is the close association 2008; Hinz-Schallreuter et al., 2008; Wrona, 2009), in addition to data of Siberia with Laurentia and East Avalonia, discussed above and West provided herein. Any bradoriid taxon that was questionably assigned at Avalonia displaying a stronger faunal association with Armorica and Morocco generic level have been omitted from the following analysis. Given the scope (Fig. 3C). Recent publica-tions (e.g. Skovsted et al., 2006; Topper et al., 2007; of our data, the biogeographic cluster analyses were limited to the early Zhang, 2007; Hinz-Schallreuter et al., 2008; Dies Αlvarez et al., 2008; Jones Cambrian; results discussed below. and Kruse, 2009; Wrona, 2009 and herein) have greatly increased the database of early Cambrian bivalved arthropod biodiversity, especially from East Gondwana, where nine new genera have been established. Despite this 3.1. Bradoriid assemblages from East Gondwana increase in faunal diversity, the resulting cluster analysis (Fig. 3C) produced only minor changes to the results of the original analysis conducted by At the specific level the bradoriid assemblages from the early Cambrian of Williams et al. (2007). East Gondwana are largely endemic. Strong faunal provinciality among bradoriid species is not unusual at this time and has been recognised by numerous authors (e.g. Siveter and Williams, 1997; Williams et al., 2007), in A possible explanation for the limited variation in analyses is the high particular faunas from South China frequently display high levels of levels of endemism displayed in recently described bradoriid assemblages endemism (Hou et al., 2002; Zhang, 2007). However, several genera from (Skovsted et al., 2006; Topper et al., 2007; Zhang, 2007; Wrona, 2009). East Gondwana exhibit a wider distribution in the early Cambrian, including Recent documentation of early Cambrian bradoriid assemblages from South Liangshanella Huo, 1956 that has a near cosmopolitan distribution. As a result Australia contain a high portion of endemic genera, including Spinospitella of particular palaeocontinental regions displaying high levels of endemism Skovsted, Brock and Paterson, 2006, Amphikeropsis Topper, Skovsted, Brock during the early Cambrian (e.g. East Gondwana and South China), two cluster and Paterson, 2007, Onagrocharion Topper, Skovsted, Brock and Paterson, analyses were undertak-en (Figs. 3B-C, 4). The first analysis (Fig. 3B-C) 2007 and Quadricona gen. nov. A diverse early Cambrian fauna from the incorporates the presence-absence of 60 bradoriid genera from the early Yu'anshan and Shuijingtuo formations of South China documented by Zhang Cambrian. The second analysis (Fig. 4) only incorporates bradoriid genera (2007) included three new endemic genera, Retaluta, Spinaluta and Yucola. that have been documented from two or more early Cambrian To highlight the strong endemism displayed by South Chinese faunal palaeocontinental regions, thereby removing all endemic taxa. We have also assemblages during the early Cambrian, of the total 32 genera documented, run the analysis with Australia and Antarctica as separate entities during the 19 are entirely restricted to the South China province. The addition of early Cambrian (Figs. 3B, 4A) and as amalgamated provinces of the endemic taxa into a quantitative cluster analysis would not significantly palaeocontinental region of East Gondwana (Figs. 3C, 4B). We note that change the resulting biogeographic groupings of the palaeocontinental differences in taxonomic diversity between the analysed faunas do impose regions; merely change the similarity index between them. To gain a better some limita-tions on the cluster analysis. Some regions remain inadequately understanding of the association of faunal assemblages during the early explored in terms of bradoriid diversity (see Appendix), for example, Cambrian we decided to conduct the cluster analysis again by omitting Antarctica only has four described genera for the early Cambrian (e.g. Rode bradoriid genera that have only been documented from a single lower et al., 2003; Stigall, 2008; Wrona, 2009). Bradoriid diversity in other regions Cambrian palaeocontinental region, effectively removing all endemic taxa. is much higher, such as Australia where 21 bradoriid genera have been documented from the early Cambrian (e.g. Skovsted et al., 2006; Topper et al., 2007; herein). The South China terrain hosts the most diverse bradoriid faunal assemblage during the early Cambrian with 32 genera documented. The resulting cluster analysis (Fig. 4A) displays four distinct biogeographic groupings for the early Cambrian. Similar to previous results, close faunal associations exist between the palaeocontinental regions of the Acadobaltic Province (sensu Sdzuy, 1972), including West Avalonia, West Gondwana (Morocco and Armorica) and Baltica. Siberia has been biogeographically linked with Kazakhstan based solely on the occurrence of The first pair-group cluster analysis (Fig. 3B) displays many similarities Alutella Kobayshi and Kato, 1951 on both palaeocontinents. Laurentian with the original cluster analysis (Fig. 3A) produced by Williams et al. faunal assemblages have curiously been closely associated with Antarctica, (2007). Williams et al. (2007) recognised a wide distribution of congeners in based on the presence of Albrunnicola Martinsson, 1979 and Liangshanella the western hemisphere, between Avalonia, Baltica, Laurentia and West Huo, 1956. However, this appears superficial, considering the strong evidence Gondwana, a view supported by data presented here. Both analyses also supporting the close early Cambrian faunal associations of Australia and illustrate an association between South China and Kazakhstan. Close faunal Antarctica, based on trilobites (Palmer and Rowell, 1995; Brock et al., 2000; connections exist between West Avalonia and West Gondwana (Morocco and Paterson, 2005; Paterson and Jago, 2006), brachiopods (Holmer et al., 1996; Armorica) based on the presence of taxa including Hipponicharion Matthew, Brock et al., 2000), archaeocyaths (Zhuravlev and Gravestock, 1994), 1886 and Matthoria Siveter and Williams, 1997. The bradoriid fauna of molluscs (Wrona, 2003) and small shelly fossils (Evans and Rowell, 1990; Baltica displays close similarities with the fauna of West Avalonia, but also Wrona, 2004). The apparent close relationship between Laurentia and with Armorica and Morocco, supporting the previously recognised (Gozalo et Antarctica highlights one of the challenges with utilising this quantitative al., 2004; Dies Αlvarez et al., 2008) Acadobaltic Province sensu Sdzuy technique as differences in taxo-nomic diversity between faunal assemblages (1972). The main discrep-ancy between the analyses is the close faunal can distort the outcomes. Only two non-endemic bradoriid genera have been association between Siberia, Laurentia and East Avalonia (Fig. 3C) based on confirmed from Antarctica (Albrunnicola and Liangshanella), six genera have the presence of taxa including Liangshanella Huo, 1956 and Matthoria, a been documented from Laurentia, whereas twelve genera have been grouping not recognised in the analysis presented by Williams et al. (2007). documented from the early Cambrian of Australia (see Appendix). Despite Australia, similar to data presented Williams et al. (2007), displays only weak Albrunnicola and Liangshanellaoccurring on all three continental statistical similarity to Siberia, Laurentia, East Avalonia and Antarctica. terranes, statistically, Antarctica will display a higher similarity to Laurentia because of the higher taxonomic diversity of Australian faunal assemblages. Incorporating the early Cambrian faunal assemblages of Australia and Antarctica to form an East Gondwana assemblage T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 317 Fig. 5. Liangshanella circumbolina sp. nov. All specimens from the Ajax Limestone, Mount Scott Range. A-D, holotype, SAMP44789, sample AJX-M/209.2; A, lateral view of right valve, stereo pair, scale bar 500 μm, B, interior view of right valve, scale bar 500 μm, C, external surface ornament, scale bar 10 μm, D, detail of external surface ornament, scale bar 5 μm; E, detail of external surface ornament, scale bar 5 μm, SAMP44790, sample AJX-M/209.2; F-I, SAMP44791, sample AJX-M/209.2; F, lateral view of left valve, scale bar 500 μm, G, interior view of left valve, scale bar 500 μm, H, detail of interior of left valve, scale bar 10 μm, I, detail of sealed, tubular structures, protruding from the interior of the valve, scale bar 10 μm. Australia and South China are shown to have a very strong faunal present in the early Cambrian of South China, further strengthening the association, with a similarity index of 0.94 (Fig. 4A), a marked contrast with biogeographic ties between the two palaeocontinental regions. The the information presented by Williams et al. (2007) and by our previous biogeographic groupings shown in Fig. 4B strongly reflect the distribution of analysis (Fig. 3A-B). Incorporating the early Cambrian faunal assemblages of trilobites during the early Cambrian. South China and East Gondwana are Australia and Antarctica to form an East Gondwana assemblage (Fig. 4B) characterised by trilobites that distinguish the Redlichiid trilobite Realm, barely changes the original dendrogram. East Gondwana and South China whilst Laurentia, Avalonia and Baltica are characterised by trilobites again display a very definitive faunal association, with a slightly stronger distinguishing the Olenellid trilobite Realm. Intervening regions, such as similarity index than previously of 0.96 (Fig. 4B). This result is not Siberia, Morocco, Armorica and potentially Kazakhstan are characterised by surprising, as bradoriid taxa such as Zepaera Fleming, 1973, Haoia Shu, 1990, trilobites of the transitional Bigotinid trilobite Realm (McKerrow et al., 1992; Hipponicharion, Liangshanella, Parahoulongdongella Shu, 1990, Pillola, 1993). Albrunnicola (Albrunnicola bengtsoni =Beyrichona chinensis Zhang, 2007, p. 145) and Mongolitubulus (Mongolitubulus unispinoa = Spinella unialata) Early Cambrian trilobites and other non-mineralized arthropods have documented from the Mernmerna Formation (Skovsted et al., 2006; Topper et recently been subjected to a number of quantitative biogeographic analyses al., 2007) and the Ajax and Wirrapowie limestones herein (Figs. 5-7), have all (e.g. Lieberman, 1997, 2003a, b; Meert and Lieberman, 2004; 2008; been documented from the lower Cambrian (Eoredlichia-Wutingaspis Hendricks and Lieberman, 2007; Z. Zhang et al., 2008). In particular, the Biozone) of China (e.g. Shu, 1990; Hou et al., 2002; Zhang, 2007). Based on results of Lieberman (2003a, text-fig. 2; 2003b, fig. 2) and Meert and similar shield morphologies, we consider Spinella unialata Zhang, 2007 (pl. Lieberman (2004, fig. 4) show similar major biogeographic groupings to our 17, figs. 1-8) to be conspecific with Mongolitubulus unispinosa Topper, results, especially when compared with the cluster analysis that omitted Skovsted, Brock and Paterson, 2007 (figs. 6A-J, 7A-C) and Beyrichona endemic bradoriid genera and treated Australia and Antarctica as a single chinensis Shu, 1990 documented by Zhang (2007, p. 145, pl. 17, figs. 9-16) to region (Fig. 4B). However, it is important to note that some discrepancies be conspecific with Albrunnicola bengtsoni Hinz-Schallreuter, 1993a. may be the result of the type of analysis conducted (phylogeographic vs. cluster, or a cladistic vs. phenetic approach, respectively) and the fact that the trilobite analyses were strongly biased towards the inclusion of olenelline taxa, which are absent in East Gondwana and South China. The analysis The biogeographic ties between the two palaeoncontinental regions of involving non-mineralized arthropods (Hendricks and Lieberman, 2007) pro- South China and East Gondwana has been previously recognised based on duced results that show significant differences in area relationships to those trilobites (see Paterson and Brock, 2007). However, the results of the original produced by bradoriid and trilobite data, although the grouping of Baltica and cluster analysis (Fig. 3C) show a low similarity index between South China Africa and the close relationship of Siberia and Laurentia (Hendricks and and East Gondwana (0.3). This evidently appears to be a direct result of Lieberman, 2007, fig. 2) is supported by some of our results (Figs. 3B-C, 4A). differences in taxonomic diversity between the analysed faunas, due to high Hendricks and Lieberman (2007) provided a number of explanations for these levels of endemism. Ten out of the total 12 non-endemic bradoriid genera differences, documented from the early Cambrian of South Australia are 318 T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 Fig. 6. A-F, Zepaera jagoi sp. nov. All from the Ajax Limestone, Mount Scott Range, all scale bars 200 μm, unless otherwise stated. A-C, holotype, SAMP44792, sample AJX-M/266; A, lateral view of right valve, stereo pair, B, detail of external surface ornament, scale bar 20 μm, C, detail of spinose margin, scale bar 20 μm; D, lateral view of left valve, SAMP44793, sample AJX-M/256; E-F, SAMP44794, sample AJX-M/266; E, internal view of left valve, F, internal view showing duplicature, scale bar 20 μm; G-M, Quadricona madonnae gen. et sp. nov. G-J, holotype from the Mernmerna Formation, Elder Range, SAMP44795, sample ER-9/67.3; G, lateral view of left valve, H, oblique lateral view of left valve, I, oblique lateral view from posterior, J, detail of external surface ornament, scale bar 10 μm; K, lateral view of right valve, scale bar 500 μm, SAMP44796, sample AJX-M/268.7; L-M, SAMP44797, sample AJX-M/271.3; L, dorsal view of shield, scale bar 500 μm, M, oblique view of shield, scale bar 500 μm. but it is also worth noting that their analysis included taxa ranging from the douvillei (Mansuy, 1912) accounting for over 80% of recovered individuals in early Cambrian to latest Ordovician, potentially introduc-ing noise to the the Chengjiang biota (Hou and Bergstrom, 1991; Hou et al., 2002). In biogeographic signal. contrast, East Gondwanan bradoriid assemblages contain an equal proportion Recent palaeogeographic reconstructions of the early Cambrian indicate of many different groups, including the svealutids (Liangshanella), that Australia and the South China block occupied the tropical carbonate hipponicharionids (Hipponicharion and Albrunnicola), beyrichonids development zone (30° ± 5° north and south latitudes) (Brock et al., 2000; (Parahoulongdongella), comptalu-tids (Zepaera, Alutella), monasteriids Meert and Lieberman, 2004; Williams et al., 2007). During the early (Epactridion) and many other genera that are yet to be confidently assigned at Cambrian in South China, the dominant groups of bivalved arthropods are the family level (e.g. Onagrocharion, Amphikeropsis and Spinospitella). kunmingellids and the comptalutids. Kunmingellids frequently cover bedding surfaces (e.g. in the Heilinpu Formation), with the type species, Kunmingella Williams et al. (2007) identified a number of faunal assem-blages that reflected tropical and temperate climates during the T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 319 Fig. 7. A-G, Parahoulongdongella bashanensis Shu, 1990. From the Mernmerna Formation, Elder Range and the Ajax Limestone, Mount Scott Range, all scale bars 200 μm, unless otherwise stated. A, lateral view of right valve, SAMP44798, sample ER-9/16.5; B-D, SAMP44799, sample ER-9/16.5; B, lateral view of right valve, C, oblique lateral view of right valve, D, detail of external surface ornament, scale bar 10 μm, E-G, SAMP44800, sample ER-9/53.5; E, lateral view of right valve, F, oblique lateral view of right valve, G, detail of external surface ornament, scale bar 50 μm; H, Zepaera sp., lateral view of right valve, SAMP44801, sample AJX-M/410; I, Mongolitubulus sp., lateral view of spine, SAMP44802, sample ER-9/10.8; J-K, Mongolitubulus squamifer Missarzhevsky, 1977. J-K, SAMP 44803, sample AJX-M/415; J, lateral view of spine, scale bar 60 μm, K, detail of external surface ornament, scale bar 20 μm; L, Comptalutid gen et. sp. indet., lateral view of right valve, scale bar 100 μm, SAMP44804, sample AJX-M/266; M, Euzepaera sp., lateral view of right valve, scale bar 500 μm, SAMP44805, sample ER-9/53.5; N, Spinospitella coronata Skovsted, Brock and Paterson, 2006, lateral view of valve fragment, SAMP44806, sample ER-9/0; O, Dabashanella hemicyclica Huo and Shu in Huo et al., 1983, lateral view of left valve, SAMP44807, sample AJX-M/274.4; P, Indet. phosphatocopid, lateral view of left valve, scale bar 100 μm, SAMP44808, sample AJX-M/256.5. Cambrian. The East Gondwana bradoriid assemblage in the early Cambrian amongst the early Cambrian faunal assemblages of South China (Hou et al., broadly conforms to the climatic distribution patterns identified by Williams 2002). Hipponicharion, a genus previously thought to be re-stricted to the et al. (2007). Comptalutids, prevalent in South Chinese and Australian Acadobaltic Province (sensu Sdzuy, 1972; Gozalo and Hinz-Schallreuter, assemblages are interpreted as warm water tropical and sub-tropical 2002; Gozalo et al., 2004) has since been documented from South China and bradoriids that cover a latitudinal range from about 30° North to 15° South South Australia (Topper et al., 2007; Zhang, 2007), extending the (Williams et al., 2007). Species of Liangshanella have been documented from biogeographic range of the genus into low latitude, tropical regions. The early Cambrian faunal assemblages in East Gondwana, South China, beyrichonids, Beyrichona Matthew, 1886 and Parahoulongdongella have also Avalonia, Laurentia and Baltica and thus seems capable of surviving in both been described from the low latitude faunas of southern Kazakhstan low and mid-latitudes (Williams et al., 2007). (Melnikova et al., 1997), South Australia and South China (Topper et al., 2007; Zhang, 2007). While both groups may be more abundant in Avalonian The beyrichonids and hipponicharionids have been recognised as mid- to and Baltic faunas, holistically, representatives of the Hipponicharionidae and high latitude bradoriids (further north and south than 30°), based on their Beyrichonidae, were evidently able to disperse between the warm climates of preference for Avalonia and Baltica during the Cambrian (Williams et al., South Australia and South China and the cooler climates of Avalonia and 2007). Regardless, some hipponicharionids, like Neokunmingella Zhang, Baltica. 1974, Meishucunella Jiang, 1982 and occur 320 T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 4. Systematic palaeontology fied by Hou et al. (2002) who synonymised both Hanchungella and Ovaluta with Liangshanella citing similar shield morphologies. Hou et al. (2002) All specimens described and illustrated herein are housed in the considered that the alleged differences in anterior cardinal angle – palaeontological collection of the South Australian Museum (acro-nym: traditionally used to discriminate these genera – was the result of SAMP). Stratigraphic ranges for all taxa are provided in terms of true deformational processes, and thus of no taxonomic significance. Zhang (2007) thickness above the base of the AJX-M and ER-9 sections. The terminology disputed this synonymy and suggested that a lack of ontogenetic information used to describe the bivalved arthropods largely follows that employed to made such claims premature. Zhang (2007) considered all generic names describe Ordovician and later ostracods (as adopted in Siveter and Williams, valid, and noted that the presence of an anterior lobe can be used to 1997; Williams and Siveter, 1998; Hou et al., 2002). We follow Siveter et al. distinguish Hanchungella from a lobeless Liangshanella. Zhang (2007) was (2003, p. 13) in using the more neutral term “head-shield”, or “shield” instead also unconvinced that Ovaluta represented a juvenile instar of Liangshanella, of the ostracod term “carapace” (see also Maas et al., 2003). The majority of instead noting the strong similarities in shield size and features of Ovaluta additional bivalved arthropod taxa in the Ajax and Wirrapowie assemblages with Bullaluta Copeland, 1986, an upper Cambrian (Furongian) bradoriid of (see Figs. 2, 7) have been described previously from the Mernmerna western Newfound-land, and suggested that the former may be a junior Formation; refer to Skovsted et al. (2006) and Topper et al. (2007) for synonym. descriptions and discussions. Liangshanella circumbolina sp. nov. displays the postplete shield, Phylum Arthropoda Siebold and Stannius, 1845 lateroadmarginal rim and lack of lobation typical of the genus and is similar Order Bradoriida Raymond, 1935 Family Svealutidae in general shield outline to L. liangshanensis Huo, 1956, L. rotundata Huo, Öpik, 1968 1956 and L. yunnanensis Zhang, 1974 described from South China and L. Liangshanella Huo, 1956 burgessensis Siveter and Williams, 1997 from the Burgess Shale in Canada. Type species. Liangshanella liangshanensis Huo, 1956 However, all four of these species have a weakly to moderately developed Liangshanella circumbolina sp. nov. (Fig. 5) anterodorsal node, a feature absent in L. circumbolina sp. nov. Liangshanella Type material. Holotype: SAMP44789 (Fig. 5A-D) from sample number baensis described by Zhang (2007, pl. 15, figs. 1-5) from the Shuijingtuo AJX-M/209.2, 117 m true thickness above the base of the section, Ajax Formation of southern China differs by possessing a broad, shallow sulcus Limestone, Mount Scott Range. Paratypes: SAMP44790 (Fig. 5E) and underneath the anterodorsal margin and a narrow marginal rim. Liangshanella SAMP44791 (Fig. 5F-I) from sample number AJX-M/ 209.2, 117 m true sayutinae (Melnikova, 1988) from the Trans-Baikal area in the Russian Far- thickness above the base of the section, Ajax Limestone, Mount Scott Range. East and Greenland (Melnikova et al., 1997; Skovsted, 2006) lack an anterodorsal node and has a valve profile similar to L. circumbolina sp. nov., Etymology. Dervied from the Latin prefix circum, circle and bolus, lump. but differ by the surface ornament of fine cancelate ridges. Liangshanella In reference to the distinctive circlet of raised papillate struc-tures on the circumbolina sp. nov. possesses a very distinctive exterior valve ornament outer valve surface. consis-ting of evenly distributed depressions each containing a raised circlet Diagnosis. Moderately to strongly inflated postplete valves with of closely joined papillae surrounding a single, sub-micron sized central a straight hinge line. Latero-admarginal ridge present, entire between perforation (Fig. 5C-E). This highly distinctive exterior valve ornament has cardinal corners, anterodorsal or posterodorsal lobation or sulci absent. Outer not been previously documented from any Liangshanella species, nor indeed surface with numerous, shallow depressions each hosting a submicron sized, from any other bradoriid species. However, it should be noted that the centrally located circular perfora-tion girt by a circlet of raised, closely majority of Liangshanella species have been described based on “crack-out” packed papillate structures; individual depressions are sealed on the internal macrofossil specimens from fine-grained siliciclastic rocks (e.g. Siveter and valve surface by raised, cylindrical pillars. Williams, 1997; Hou et al., 2002), a mode of preservation not ideal for preserving fine, microstructural detail. Minute surface perforations have been Description. Moderately to strongly inflated valves, with a straight hinge previously interpreted as potential openings for sensory setae (Skovsted et al., line. Postplete valves exhibiting a distinct lateroadmarginal ridge, entire 2006; Topper et al., 2007), analogous to those found in modern ostracods. The between cardinal corners and separated from the lateral surface by a function of the raised circlet of papillae surrounding the central perforation is continuous furrow. Maximum dimensions of shield are 1.48 mm in length and unknown, but may have provided some protection to the base of sensory hairs 1.27 mm in height. Lateral surface lacks dis-tinct anterodorsal or that may have developed inside the sealed cylindrical pillars on the inner posterodorsal nodes or sulci. Valve surface consists of numerous, small surface of the valve. Similar structures are found in the recent ostracod, depressions, varying from 7 – 12 µm in diameter that are evenly distributed Elofsonia baltica (Hirschmann, 1909), which possesses sieve-pores that have over the entire shield (Fig. 5C). Each individual depression hosts a submicron a central sensory hair, surrounded by a ring of mound-like papillae (see sized, centrally located circular perforation (Fig. 5D-E) surrounded by a Whittaker, 1973, pl. 1:37:200, fig. 2). However, the exact functional circlet of raised, closely packed papillate structures; raised circlet structure significance of the mound-like papillae in this taxon also remains mysterious. has an approximate diameter of 4 µm (Fig. 5D-E). Internally, each depression is sealed by raised cylindrical pillars that protrude from the valve some 10 - 13 µm (Fig. 5H-I); neighbouring pillars can be fused or isolated (Fig. 5H, I), depending on space between individual depressions. Remarks. Postplete bradoriid valves from the Cambrian that display little The FAD of Liangshanella circimbolina sp. nov. occurs some 20 m below or no lobation are often referred to the genus Liangshanella Huo, 1956. the FAD of the zonal trilobite Abadiella huoi in the Ajax Limestone. The pre- Originally described for svealutids that exhibit no lobation (Huo, 1956), the trilobitic occurrence of this species means that, potentially, Liangshanella generic diagnosis has since been modified slightly to incorporate an anterior circumbolina sp. nov. represents the oldest bradoriid taxon hitherto lobe that may range from well developed to virtually lacking (Siveter and documented from the early Cambrian of East Gondwana. Previously, the Williams, 1997; Hou et al., 2002). The simplicity of shield morphology makes oldest bradoriids documented from East Gondwana were possible svealutids it difficult to distinguish Liangshanella from other bradoriid genera that also from the lower Cambrian (Atdabanian equivalent) Parara Limestone at possess a non-lobate shield, such as Indiana Matthew, 1902, Hanchungella Curramulka Quarry on Yorke Peninsula described by Chapman (1918) as Huo, 1956, Ovaluta Zhang, 1987 and Indota Öpik, 1968. Such difficulties are ostracods. Jell in Bengtson et al. (1990, fig. 7) indicated that the lower exempli- levels of the Parara Limestone at Curramulka T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 321 contained A. huoi, and thus can be correlated with the A. huoi Biozone. Jones remnants of three head and two trunk appendages. Based on the ontogentic and Laurie (2006) suggest that the drawings by Chapman (1918, pl. 9, figs 1, patterns of segmentation in Crustacea, Hou et al. (2010) reconstructed the 2, 5) bear some resemblance to the Svealutidae, however without a more adult as having four head appendages. However, to date only two bradoriid accurate representation of the specimens, comparison with L. circumbolina species (Kumingella douvelli and Kunyangella cheni) have been described sp. nov. is not possible. with their soft-part anatomy preserved (Hou et al., 1996, 2010; Shu et al., 1999). Distribution. Ajax Limestone, lower Cambrian (Series 2, Stage 3), In the absence of soft-part preservation, Zhang (2007) suggested detailed Flinders Ranges, Arrowie Basin, South Australia. ontogenetic assessment may provide a solution for elucidating the taxonomic Stratigraphic range. All specimens recovered from a single stratigraphic status of comptalutids. Whilst the various growth stages of some bradoriids, level, 117 m above the base of the AJX-M section. such as Zepaera rete Jones and McKenzie, 1980, Flemingopsis dua (Jones and Family Comptalutidae Öpik, 1968 McKenzie, 1980) and Houlongdongella xichuanensis Zhang, 1987, have been Zepaera Jones and McKenzie, 1980 well illustrated, the ontogeny of the vast majority of bradoriids remain Type species. Zepaera rete Jones and McKenzie, 1980 obscure. This is primarily due to a lack of available material, since an Zepaera jagoi sp. nov (Fig. 6A-F) accurate ontogenetic framework requires a considerable catalogue of Type material. Holotype: SAMP44792 (Fig. 6A-C) from sample number specimens. Zhang (1987), for example, investigated AJX-M/266, 148.75 m true thickness above the base of the section, Ajax Limestone, Mount Scott Range. Paratypes: SAMP44793 (Fig. 6D) from 131 specimens of Houlongdongella xichuanensis and Hinz-Schall-reuter sample number AJX-M/255, 143 m true thickness above the base of the (1999) examined 240 specimens of Zepaera rete and 221 specimens of section, Ajax Limestone, Mount Scott Range and SAMP44794 (Fig. 6E-F), Flemingopsis dua for ontogenetic analysis. The difficulties associated with from sample number AJX-M/266, 148.75 m true thickness above the base of charting bradoriid ontogeny using external features of the shield was recently the section, Ajax Limestone, Mount Scott Range. highlighted by Hou et al. (2010) who described pre-adult and adult specimens of Kumingella douvelli and Kunyangella cheni that displayed changes in soft- Etymology. Named for Dr. Jim Jago, in recognition for his con-tributions part anatomy between growth stages, but little or no morphologic change was to South Australian Cambrian geology, palaeontology and biostratigraphy. manifested in shield morphology. The genus Zepaera was originally reserved for comptatulid bradoriids with distinctive lobes forming a characteristic Diagnosis. Valves postplete, with a marked retral swing and a well omega-shaped ridge on the anterior part of the valve. However, the omega- developed, straight hinge line. Lateroadmarginal ridge present, entire between shaped ridge was found to be only distinct in juvenile stages, gradually cardinal corners with valves showing weak anterior sulcation. Valve exterior becoming effaced, until it fades completely in adult stages (Jones and with widely spaced, circular punctae; surface ornament consists of irregularly McKenzie, 1980; Hinz-Schallreuter, 1999). This ontogenetic variation has concentric wrinkled texture. Valve margin well defined, ornamented by a also been observed in other comptalutids (e.g. Flemingopsis dua Hinz- series of regularly spaced, short, tapering spines. Schallreuter, 1999). Zepaera jagoi sp. nov. lacks these characteristic ridges and with the large majority of specimens approaching a maximum length of Description. Valves small (maximum height 810 µm, maximum length approximately 960 µm), postplete, with a well developed, straight hinge line. Valves have a thin (approximately 7.5 µm in width) later-oadmarginal ridge, entire between cardinal corners. Lateroadmar-ginal ridge separated from the lateral surface 900 µm, all specimens are herein considered to represent fully mature adults. by a continuous, but weakly defined shallow depression (Fig. 6C). Valve Zepaera jagoi sp. nov. displays the typical postplete shield outline and marked margin well defined, ornamented by a series of regularly spaced, short, retral swing characteristic of adult Zepaera species. Zepaera jagoi sp. nov. tapering spines (Fig. 6C). Spines are approximately 10 µm in length and vary displays a weak V-shaped anterodorsal sulcus but lacks any obvious anterior between 13-19 µm in width and are continuous along the valve margin, lobation that characterises the type species, Z. rete. The irregularly concentric, between cardinal corners (Fig. 6A). Lateral surface moderately to strongly wrinkled ornament of Z. jagoi sp. nov. also distinguished it from the well inflated, without distinct anterodorsal or posterodorsal nodes. A weak, V- developed reticulate ornament in the type species. There are a number of shaped centrodorsal depression is present in some specimens (Fig. 6D). Cambrian bradoriid genera with short spine-like protuberances from their Surface is infrequently punctate (Fig. 6C) ornamented with an irregularly shield; however the regularly spaced, short spines that adorn the valve margin concentric wrinkled texture (Fig. 6B). Some specimens exhibit low, flat of Z. jagoi sp. nov. (Fig. 6A, C) have not been previously described in any circular welt-like structures, varying in diameter from 26 µm to 63 µm (Fig. known bradoriid taxon. 6B). Interior displays a well defined duplicature, entire between the cardinal corners (Fig. 6F). Distribution. Ajax Limestone, lower Cambrian (Series 2, Stage 3), Abadiella huoi Biozone, Flinders Ranges, Arrowie Basin, South Australia. Remarks. Comptalutids, like svealutids, frequently exhibit mor- Stratigraphic range. A total of 5.6 m between 143.15-148.75 m above the phologically simple shields that result in taxonomic confusion between some base of the section AJX-M. early Cambrian bradoriids such as Houlongdongella Lee, 1975, Flemingopsis Family Hipponicharionidae Sylvester Bradley, 1961 Jones and McKenzie, 1980, Zepaera Jones and McKenzie, 1980 and Remarks. A subtriangular shield in conjunction with distinct, anterodorsal Quetopsis Hinz-Schallreuter, 1999. The exact taxonomic status and and posterodorsal lobes is indicative of two families within the Bradoriida, relationship of these taxa has been the focus of frequent discussion, but the Hipponicharionidae and the Beyrichoni-dae. The beyrichonids can be remains controversial (Shu, 1990; Hinz-Schallreuter, 1999; Skovsted et al., discriminated from the hipponichar-ionids by having a less inflated shield, 2006; Zhang, 2007). Due to the simplicity of the comptalutid shield, soft-part with subdued anterior and posterior lobes that are frequently less ventrally morpho-logical information will undoubtedly play an important role in the extended (Hinz-Schallreuter, 1993a, c; Siveter and Williams, 1997). The close taxonomic resolution of many comptalutid taxa. New soft-part preservation morphological similarity between the two families was recognised by Öpik has assisted in the taxonomic classification of the comptaluid Kunyangella (1968), who regarded the Hipponicharionidae as a subjective synonym of the Huo, 1965 documented from the Chengjiang Lagerstätte of China (Hou et al., Beyrichonidae based on the comparable morphology of Hipponicharion 2010). A specimen of Kunyangella cheni Hou, Williams, Siveter, Siveter, Matthew, 1886 and Beyrichona Matthew, 1886, the type genera of their Aldridge and Sansom, 2010 interpreted as a penultimate instar displays respective families. This view has not been widely accepted. Hinz- Schallreuter (1993a), 322 T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 Siveter and Williams (1997) and Williams et al. (2007) all emphasized the measuring on average 1.19 cm in length and 0.922 cm in height, with a different lobation between the families, in particular the anterior and posterior maximum length of 1.3 cm and height of 1.05 cm. Valves are moderately lobes that ventrally extend further in the Hipponicharionidae than in the convex with generally rounded posterior and anterior margins. The anterior Beyrichonidae. In addition, Zhang (2007) noted that the posterior node or and posterior borders extend slightly beyond the hinge line (Fig. 6G). A linear lobe is distinct in the Hipponicharionidae, whereas it often forms as distinct, narrow, lateroadmar-ginal ridge is entire between cardinal corners. sulcation in the Beyrichonidae, a morphological feature that characterises the Anterodorsal and posterodorsal nodes are discrete, short, sharp, nipple-like type species, Beyrichona papilio Matthew, 1886 (see Siveter and Williams, pro-tuberances (Fig. 6E-F, L). Posterodorsal node is positioned slightly more 1997, pl.4, figs. 9-10). Based on the differences in shield inflation and dorsally than the anterodorsal node (Fig. 6G). A slight central, dorsal swelling lobation, both families are recognised as valid, separate taxonomic groupings. close to the dorsal valve margin, slightly anterior of the midline forms a weak and indistinct central lobe (Fig. 6G). Exterior surface with numerous small u- to v-shaped indentations, hosting a single, minute perforation with a Quadricona madonnae gen. et. sp. nov. displays the amplete shield, distinctive, but simple, raised rim approximately 3 µm in diameter (Fig. 6J). subtriangular shield outline and distinct lateroadmarginal ridge reminiscent of Surface sculpture partially wrinkled, especially towards the margins of the the Hipponicharionidae and Beyrichonidae, however the lobation is strikingly valves (Fig. 6I). Interior surface smooth. different. Quadricona madonnae gen. et. sp. nov. displays short, pointed anterior and posterior nodes (Fig. 6E-F, L), unlike the rounded nodes, or ridge-like lobes frequently encountered in the Beyrichonidae and the Remarks. Quadricona madonnae gen. et sp. nov. is based on eight Hipponicharionidae. The anterior and posterior nodes are prominent in all specimens recovered from the Ajax Limestone in the Mount Scott Range and specimens with no examples of posterior sulcation observed, a feature the upper Wirrapowie Limestone in the Elder Range. Quadricona madonnae frequently displayed by the beyrichonids. The moderately inflated shield and gen. et sp. nov. is the only taxon unequiv-ocally common to both localities prominent lobation displayed by Quadricona madonnae gen. et. sp. nov. and the short stratigraphic ranges in both sections (Fig. 2) may have potential supports des-ignation to the Hipponicharionidae. for future regional correlation. The shield outline and surface ornament of Q. madonnae is closely comparable to a number of Cambrian bradoriids such as Quadricona gen. nov. the hipponicharionid Albrunnicola bengtsoni Hinz-Schallreuter, 1993a and the Etymology. Derived from the Latin prefix quattuor, four and conus, cone. beyrichonid Parahoulongdongella bashanensis Shu, 1990 (see Figs. 6J, 7D). In reference to the four, short nodes on the complete shield of the bradoriid. This suggests that similar types of surface ornamentation may appear in many different bradoriid lineages, restricting the value of this feature in higher level Diagnosis. Valves small, subamplete, with a subtriangular shield outline bradoriid taxonomy. and well developed, straight hinge line. Narrow lateroad-marginal ridge, entire between cardinal corners. Anterodorsal and posterodorsal nodes are discrete, short, nipple-like protuberances. Surface with many small, closely Distribution. Ajax and Wirrapowie Limestones, Early Cambrian (Series 2, spaced circular pores, each in a well defined u-shaped depression; some pores Stage 3), Abadiella huoi Biozone, Flinders Ranges, Arrowie Basin, South with raised, circular margin. Surface sculpture partially wrinkled, more Australia. prominent towards the valve margin. Stratigraphic range. A total interval range of 1.45 m from 150.26-151.71 m above the base in section AJX-M (Ajax Limestone) and a total of 4.71 m Remarks. Discrimination of genera within the Hipponicharionidae is from 38.6-43.31 m above the base in section ER-9 (Wirrapowie Limestone). predominantly related to shield shape, size and ventral extent of the anterior and posterior lobes. For example, Wimanicharion Hinz-Schallreuter, 1993a, Andresia Hinz-Schallreuter, 1993a and Neokun-mingella Zhang, 1974, Acknowledgements typically exhibit confluent anterior and pos-terior lobes. Albrunnicola Martinsson, 1979, one of the most common bradoriids in early Cambrian Financial support towards fieldwork and laboratory costs come from a assemblages from South Australia, is characterised by a weakly developed Macquarie University Research Development Grant to GAB and CBS. posterior lobe, with both lobes restricted to the dorsal half of the valve. Funding support for CBS was also provided by a postdoctoral grant from the Quadricona gen. nov. is similar in shield outline to Albrunnicola and also has Swedish Research Council (VR). We extend warm thanks to Mr Graham a very similar surface sculpture (see Topper et al., 2007, fig. 10F-G). Ragless, owner of Beltana Station and Mr Glen Gabe, Manager at Mt. Little However, the degree and development in shield lobation between the two Station for access to the field areas. We are indebted to B. Jonak, P. Cockle, genera is strikingly different. The discrete short, nipple-like projections dis- L.E. Holmer, J.B. Jago, R. Smart, M. Smith, T. Bradley, R. Callow and M. played by Quadricona gen. nov. is a unique morphological character-istic that Fuller for their assistance during the field seasons when this material was easily distinguishes it from other genera within the Hipponicharionidae. collected. We are indebted to Dean Oliver (Dean Oliver Graphics) for drafting Figs. 1-2 with characteristic skill and speed. We also acknowledge Elsevier for permission to reproduce the cluster analysis presented by Williams et al. Quadricona madonnae gen. et sp. nov. (Fig. 6G-M) (2007, fig. 10, reproduced here in Fig. 3A). The manuscript benefited from the Type material. Holotype: SAMP44795 (Fig. 6G-J) from sample number constructive reviews of two anonymous reviewers. ER-9/67.3, 38.6 m true thickness above the base of the section, Wirrapowie Limestone, Elder Range. Paratypes: SAMP44796 (Fig. 6K) from sample number AJX-M/268.7, 150.2 m true thickness above the base of the section and SAMP 44797 (Fig. 6 L-M) from sample number AJX-M/271.3, 151.7 m Appendix A true thickness above the base of the section, Ajax Limestone, Mount Scott Range. Global distribution of bradoriid genera of the major palaeoconti-nents Etymology. Named for the American entertainer Madonna; in reference to during the early Cambrian. Presence of bradoriid genera indicated by shaded the nodes on each valve resembling her conical brassiere made famous during box. Taxa that have only been documented from a single palaeocontinental the 1980s and 1990s, particularly her “Blond Ambition” tour in 1990. region and subsequently removed from the second cluster analysis (Fig. 4) are indicated with an asterix. Principal sources of revised taxonomy and Diagnosis. As for genus, by monotypy. biogeographic informa-tion from Morocco (Hinz-Schallreuter, 1993a), Description. Valves subamplete with a subtriangular outline and a well Australia (Opik, 1968; Fleming, 1973; Jones and McKenzie, 1980; Hinz- developed, straight hinge line. The valves are small in size, Schallreuter, T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 323 1999; Skovsted et al. 2006; Topper et al., 2007), Antarctica (Rode et al., 2003; and Bassler, 1931; Dies Αlvarez et al., 2008), West Avalonia (Siveter and Wrona, 2009), Armorica (Gozalo et al., 2004; Vannier et al., 2005), Siberia Williams, 1997), East Avalonia (Williams and Siveter, 1998), South China (Melnikova et al., 1997), Laurentia (Siveter et al., 1996; Siveter and Williams, (Hou et al. 2002; Zhang, 2007) and Kazakhstan (Melnikova et al. 1997). 1997; Skovsted 2006), Baltica (Ulrich 324 T.P. Topper et al. / Gondwana Research 19 (2011) 310–326 References Gozalo, R., Dies, M.A., Chirivella, J.B., 2004. 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