A review of the Cambrian biostratigraphy of South Australia

Cambrian rocks in South Australia occur in the Stansbury, Arrowie, eastern Officer and Warburton Basins. The succession in the Stansbury and Arrowie Basins can be divided into three sequence sets (supersequences), 1, 2 and 3. Sequence set 1 can be divided into five third-order sequences: 1.0, 1.1A, 1.1B, 1.2 and 1.3. Trilobites from the Stansbury and Arrowie Basins are restricted largely to the lower part of the succession. Four trilobite zones are recognized: Abadiella huoi (latest Atdabanian–earliest Botoman), Pararaia tatei, Pararaia bunyerooensis and Pararaia janeae Zones (all Botoman). Trilobites higher in the succession are known from only a few horizons and in part correlate with the upper Lower Cambrian Lungwangmiaoan Stage of China, equivalent to the top Toyonian. Pagetia sp. has been reported in the Coobowie Formation of the Stansbury Basin, thus suggesting an early Middle Cambrian age.The Cambrian faunas of the Warburton Basin range in age from early Middle Cambrian (Late Templetonian) to very Late Cambrian, although the richest faunal assemblages are late Middle Cambrian (Ptychagnostus punctuosus to Goniagnostus nathorsti Zones). Conodonts, including Cordylodus proavus, occur in a Datsonian fauna.The Arrowie Basin contains the most complete and best studied archaeocyath succession in the Australia–Antarctica region. The Warriootacyathus wilkawillensis, Spirillicyathus tenuis and Jugalicyathus tardus Zones from the lower Wilkawillina Limestone (Arrowie Basin) and equivalents are correlated with the Atdabanian. Botoman archaeocyathids occur higher in the Wilkawillina Limestone. The youngest (Toyonian) archaeocyath fauna in Australia occurs in the Wirrealpa Limestone (Arrowie Basin).Brachiopods and molluscs of the Arrowie and Stansbury Basins can be divided into four biostratigraphic assemblages. Several informal Early Cambrian SSF biostratigraphic assemblages are recognized. Probable tabulate-like corals occur in the Botoman Moorowie Formation. Seven informal acritarch assemblages occur in the Early Cambrian of the Stansbury and Arrowie Basins. Trace fossils may mark the Precambrian–Cambrian boundary. Only two of several tuffaceous horizons from the Stansbury and Arrowie Basins have been dated (i) a date of 522.0 ± 2.1 Ma from the Heatherdale Shale of the Stansbury Basin, about 400 m above latest Atdabanian archaeocyathids and (ii) a date of 522.0 ± 1.8 Ma from the lower part of the Billy Creek Formation in the Arrowie Basin. Neither date is regarded as reliable.     

Paterimitra pyramidalis from South Australia: scleritome,shell structure and evolution of a lower Cambrian stem group brachiopod

The tommotiid Paterimitra pyramidalis Laurie, 1986, is redescribed based on well‐preserved material from the lower Cambrian Wilkawillina, Wirrapowie and Ajax limestones of the Flinders Ranges, South Australia. The material shows that the scleritome of Paterimitra pyramidalis includes three sclerite morphotypes (S1, S2 and L). Detailed shell microstructure studies show striking similarities with both the paterinid brachiopod Askepasma toddense and the tommotiid Eccentrotheca helenia, which strengthens the suggested evolutionary link between tommotiids and brachiopods. Based on the partly articulated specimens and similarities in shell microstructure and sclerite morphology with Eccentrotheca, Paterimitra pyramidalis is reconstructed as a tube‐dwelling, epifaunal, sessile, filter‐feeder with an organic pedicle‐like attachment structure. The proposed reconstruction of the scleritome comprises a basal unit composed of one S1 and one S2 sclerite, as well as an unresolved number of L sclerites lining a coniform tubular structure.     

An early Cambrian chelicerate from the Emu Bay Shale,South Australia

The Emu Bay Shale Lagerstätte (Cambrian Series 2, Stage 4) occurs on the north coast of Kangaroo Island, South Australia. Over 50 species are known from here, including trilobites and non‐biomineralized arthropods, palaeoscolecids, a lobopodian, a polychaete, vetulicolians, nectocaridids, hyoliths, brachiopods, sponges and chancelloriids. A new chelicerate, Wisangocaris barbarahardyae gen. et sp. nov., is described herein, based on a collection of some 270 specimens. It is up to 60 mm long, with the length of the cephalic shield comprising about 30% that of the exoskeleton. The cephalic margin has three pairs of bilaterally‐symmetrical small triangular spines. A pair of small eyes is placed well forwards on the ventral margin of the cephalic shield. The trunk comprises 11 segments that increase in length while narrowing posteriorly, each possibly bearing a pair of biramous appendages; the most posterior segment is almost square whereas the others are transversely elongated. The spatulate telson is proportionately longer than in taxa such as Sanctacaris, Utahcaris and Leanchoilia. Up to eight (?four pairs) of 3 mm‐long elements bearing alternating inward‐curving short and long spines beneath the cephalic shield are interpreted as basipodal gnathobases, part of a complex feeding apparatus. A well‐developed gut includes a stomach within the cephalic shield; it extends to the base of the telson. In a few specimens there are shell fragments within the gut, including those of the trilobite Estaingia bilobata (the most common species in the biota); these fragments have sharp margins and extend across the gut lumen. The species may have been a predator or a scavenger, ingesting material already broken up by a larger predator/scavenger. The morphology of this taxon shares many overall body features with Sanctacaris, and some with Sidneyia, particularly its gnathobasic complex. These chelicerate affinities are corroborated by phylogenetic analyses.     

Early Cambrian record of failed durophagy and shell repair in an epibenthic mollusc

Predation is arguably one of the main driving forces of early metazoan evolution, yet the fossil record of predation during the Ediacaran-Early Cambrian transition is relatively poor. Here, we present direct evidence of failed durophagous (shell-breaking) predation and subsequent shell repair in the Early Cambrian (Botoman) epibenthic mollusc Marocella from the Mernmerna Formation and Oraparinna Shale in the Flinders Ranges, South Australia. This record pushes back the first appearance of durophagy on molluscs by approximately 40Myr.     

Problematic cap-shaped fossils from the Lower Cambrian of North-East Greenland

Three species ofOcruranus Liu, 1979 are described from the Bastion Formation of North-East Greenland, of late Early Cambrian (middle Dyeran of North American usage) age, representing the youngest record of a genus originally described from the earliest Cambrian Meishucunian Stage of China. An accompanying species, tentatively assigned toXianfengella He &Yang, 1982, seems also to be present in South Australia in strata of late Early Cambrian (Botoman of Siberian usage) age, although also this genus was described originally from the Meishucunian.Ocruranus andXianfengella from China have been interpreted as possibly parts of coeloscleritophoran scleritomes, perhaps halkieriids, rather than individual molluscan shells. Their shell form is not typical of helcionelloids which otherwise dominate the Early Cambrian molluscan record, but conclusive evidence of affinity is not forthcoming from the Greenland records. New taxa:Ocruranus septentrionalis n. sp. andOcruranus tunuensis n. sp.      

Ontogeny of the eodiscoid trilobite Tsunyidiscus acutus from the Lower Cambrian of South China

Abstract: The morphology and ontogeny of the eodiscid trilobite Tsunyidiscus acutus Sun is described on the basis of numerous calcified specimens collected from the Lower Cambrian Shuijingtuo Formation in Yichang and Changyang, Hubei Province, South China. An ontogenetic series is established based on the articulated material including the previously unknown protaspides and meraspides (degrees 0 and 1). The material, revealing some prominent morphological changes such as the number of pygidial axial rings, genal spines retained throughout ontogeny and pygidial pleurae from furrowed to unfurrowed, enables a discussion on the trunk segmentation schedule, indicating that somitogenesis and tagmosis occurred independently during the ontogenetic development of T. acutus.     

Middle Cambrian lingulate brachiopods from the Murrawong Creek Formation,northeastern New South Wales

Fourteen species of lingulate brachiopods are documented from allochthonous limestone blocks of the Murrawong Creek Formation in the southern New England Fold Belt, northeastern New South Wales, Australia. The fauna includes Treptotreta jucunda Henderson and MacKinnon 1981, Treptotreta sp. cf. T. sp. nov. Henderson 1992, Amictocracens teres Henderson and MacKinnon 1981, Stilpnotreta magna Henderson and MacKinnon 1981, Anabolotreta tegula Rowell and Henderson 1978, Neotreta orbiculata Koneva 1990, Linnarssonia sp., Linnarssonia sp. cf. L. ophirensis (Walcott 1912), Pegmatreta clavigera sp. nov., Acrothele subsidua (White 1874), Micromitra sp. cf. M. modesta (Lochman 1940), Micromitra sp. Henderson 1992, Lingulella sp. A Henderson 1992, and Kyrshabaktella certa Koneva 1986.

The associated trilobite assemblages indicate a medial Middle Cambrian age for the blocks, and the stratigraphic ranges of several of the lingulate species have been extended. The fauna displays biogeographic links at the specific level with northeastern and southeastern Australia, New Zealand, Antarctica, North America, Kazakhstan, Siberia, and Britain; the strongest links (four species in common) are with the Georgina Basin in northeastern Australia and the Tasman Formation in New Zealand.     

Oikozetetes from the early Cambrian of South Australia: implications for halkieriid affinities and functional morphology

Shells of Oikozetetes and isolated halkieriid sclerites from a section of the lower Cambrian Mernmerna Formation in the Flinders Ranges, South Australia, are tentatively considered as being derived from the same scleritome. Details of shell morphology and the possible combination of biomineralized shell and sclerites suggest that Oikozetetes , if interpreted correctly, is closely related to Halkieria . A new interpretation of Oikozetetes shell morphology, in addition to the first report of paired muscle scars on the interior surface, sheds new light on the possible functional morphology of halkieriid shells and the means of attaching the shell to the body. The occurrence of Oikozetetes in South Australia extends its biostratigraphic range to the lower Cambrian and biogeographic range to East Gondwana.     

The diatom flora of Lake Eyre South: a large episodically filled salt lake in South Australia

Thirty-three diatom taxa were collected from the large terminal salt lake, Lake Eyre South, located in south-central Australia. The diatom assemblage included taxa that were widely distributed in marine and saline athalassic habitats in both northern and southern hemispheres, with the diatom flora of Lake Eyre South most similar to that of southern Africa. This study represents the first report on the diatom flora of Lake Eyre South and supports the findings that episodically filled lakes do not appear to be good evolutionary loci.     

Biogeography of Eocene bryozoans from the St Vincent Basin, South Australia

The first extensive and stratigraphically detailed taxonomic study of the Middle to Late Eocene Bryozoa of the St Vincent Basin has identified more than 200 species of Cheilostomata and 50 species of Cyclostomata. There are three biogeographic groups: basin endemic, Australian and global. Two-thirds (116) of the cheilostome species and seven genera are currently considered endemic to this basin. Most species are endemic to Australia and similar to those found in the Oligo-Miocene of Victoria. The Cellariidae are a common component of most Australian Cainozoic deposits, but the species are highly dissimilar, with 13 of the 17 species here being new. The global component indicates that biogeographic links with regions outside Australia still existed in the Eocene. The cyclostome genus Reticrescis is only known from the Australian and Antarctic Eocene. Ten genera have their first occurrence in the Eocene St Vincent Basin. The Phidoloporidae and Smittinidae represent the most diverse and ubiquitous groups at a geological time close to their time of origination. Contemporaneous sediments in Antarctica, eastern Europe and North America also have a diverse fauna of this family, pointing to a strong Tethyan link. Rhamphosmittina lateralis (MacGillivray) is still extant in New Zealand, having an exceptionally long time range of 40 million years. Overall, the fauna has a distinct Late Cretaceous character. A new genus of Onychocellidae appears similar to genera that were common in Cretaceous Tethyan faunas but rare during the Cainozoic. This similarity ends in the Oligocene, after which the Australian bryozoan became endemic     

Hyolith guts in the Cambrian of northern Australia -turning hyolithomorphs upside down

A single specimen of the early Middle Cambrian (Ordian) orthothecimorph hyolith Gudugu-wan hardmani with preserved gut filling has been discovered in the Montejinni Limestone, Wiso Basin, northern Australia. This represents only the eighth such occurrence worldwide. The specimen is unique among orthothecimorphs in retaining the gut filling in combination with the external mould of the operculum and invites revision of the accepted soft-part recon struction in this group, whereby the opercular lateral processes are now recognized to be ventral. Thus orthothecimorph conchs, if horizontal in life, would have been oriented ventral side down, while hyolithomorphs adopted the reverse orientation: horizontal, ventral side up.     

Predation of late Marjuman (Cambrian) linguliformean brachiopods from the Deadwood Formation of South Dakota, USA

One hundred and twenty-five linguliformean brachiopods of late Marjuman (Cambrian) age with shell perforations, presumably caused by predation, were recovered from shallow-water limestones at two localities of the Deadwood Formation in the Black Hills of South Dakota, USA. Three-quarters of the perforated valves belonged to taxa in the order Acrotretida, while one-quarter of the specimens belonged to those of the order Lingulida. This is the first report of predation of fossil lingulids. In both orders there was a marked selection for valve type. Ninety-five per cent of all perforations of acrotretids were in the ventral valve, while 87% of all perforations of lingulids were in the dorsal valve. The highest rate of predation of collected acrotretids, at any stratigraphic horizon, was 22%, while the rate of predation of collected lingulids, at any given stratigraphic horizon, was as high as 9%. Half of the perforated valves had round holes with a sharp, non-beveled exterior edge, and half had irregularly shaped holes with chipped interior edges. The former type is attributed to either boring or a swift, piercing percussive strike, while the latter is attributed to a smashing percussive strike with a blunt appendage. A third type of perforation consisting of minute, roughly circular holes is thought to be too small to be the work of predators, and is assumed to be the result of an encrusting organism or parasite. The different types of perforation seen in the brachiopod valves indicate that there was more than one type of predator attacking them, including possibly one of the earliest durophages. Various hypothetical predators are suggested as potential candidates for causing the shell perforations. The criteria for their selection as possible linguliformean predators include possessing the ability to produce one of the two types of shell perforation, and being small enough to warrant preying on small (< 2 mm) brachiopods.     

A new assemblage of dabashanellids (Crustacea: Phosphatocopida) from Cambrian Stage 3 of western Hubei Province,South China

Dabashanellids are univalved phosphatocopid crustaceans, and are among the earliest crustaceans known so far. They were reported mainly from the Cambrian Stage 3 of China, but only a single species was established. Here I report a new assemblage of dabashanellids from the Cambrian Stage 3 Shuijingtuo Formation in western Hubei Province, South China. All specimens are sub-millimetre in length, and are preserved as three-dimensional carbonaceous hollow shields. Five species of Dabashanella were recognized, including the previously reported D. hemicyclica, three new species, D. longa n. sp., D. semiorbiculata n. sp., D. unispinata n. sp., and an indeterminate form Dabashanella sp. In addition, five indeterminate forms of arthropods were recovered. These dabashanellids represent part of a meiofauna that lived in the off-shore, deeper environments of mid-northern Yangtze Sea during Cambrian Age 3. This study shows greater morphological diversity and ecologic disparity of dabashanellid crustaceans, and supports the previous suggestion that the invasion of meiofaunal ecdysozoans into the off-shore, deeper environments probably occurred simultaneously with their radiation in the shallow water.     

An exceptional record of Cambrian trilobite moulting behaviour preserved in the Emu Bay Shale,South Australia

Trilobites dominate the Emu Bay Shale (EBS) assemblage (Cambrian Series 2, Stage 4, South Australia) in terms of numbers, with Estaingia bilobata Pocock 1964 being extremely abundant, and the larger Redlichia takooensis Lu 1950 , being common. Many specimens within the EBS represent complete moulted exoskeletons, which is unusual for Cambrian fossil deposits. The abundance of complete moults provides an excellent record that has allowed the recognition of various recurrent moult configurations for both species, enabling the inference of movement sequences required to produce such arrangements. Moult configurations of E. bilobata are characterized by slight displacement of the joined rostral plate and librigenae, often accompanied by detachment of the cranidium, suggesting ecdysis was achieved by anterior withdrawal via opening of the cephalic sutures. Moulting in R. takooensis often followed the same method, but configurations show greater displacement of cephalic sclerites, suggesting more vigorous movement by the animal during moulting. Both species also show rare examples of Salter's configuration, with the entire cephalon anteriorly inverted, and several other unusual configurations. These results indicate that moulting in trilobites was a more variable process than originally thought. In contrast, other Cambrian Konservat‐Lagerstätten with an abundance of trilobites (e.g. Wheeler Shale, USA, and Mount Stephen Trilobite Beds, Canada) show larger numbers of ‘axial shields’ and isolated sclerites, often interpreted as disarticulated exuviae. This points to a higher level of disturbance from factors, such as animal activity, depositional processes or water movement, compared to that of the EBS, where quiescent conditions and intermittent seafloor anoxia contributed to an unparalleled trilobite moulting record.     

The evolutionary relationships of the earliest known cycloneuralians and a new record from the Cambrian Fortunian of South China

The Cambrian Fortunian Kuanchuanpu Formation and coeval strata in southern Shaanxi and northern Sichuan Provinces contain phosphatic carbonate that has yielded unambiguous body fossils of cycloneuralians. To date, six genera and species as well as nine indeterminate forms have been reported, and they provided information on the earliest known cycloneuralians and ecdysozoans. Among them, an indeterminate form is critical for understanding the evolution of the Fortunian cycloneuralians, and here I formally name it as Xinliscolex intermedius n. gen. n. sp. It has a series of at least seven longitudinal spinose sclerites on the dorsal side, and sensory structures such as pores and tubules distributed randomly among the annuli. The trunk end has two pairs of bilaterally arranged caudal spines. Micro-CT analysis reveals the preservation of a pharynx with inverted introvert with internally hollow scalids, an esophagus, midgut and hindgut, and a terminal anus. The digestive tract of Xinliscolex intermedius resembles that of modern priapulids, implying that the earliest known cycloneuralians have evolved a relatively derived digestive system, and this lays a foundation for their further diversification and evolution.     

A new scyphozoan from the Cambrian Fortunian Stage of South China

Animals with radial symmetry are abundant in the Cambrian Fortunian Stage of South China, but with relatively low diversity: representatives include Olivooides, Quadrapyrgites, carinachitiids, hexangulaconulariids and Pseudooides. Here, we report a new radial animal, Qinscyphus necopinus gen. et sp. nov., from the Fortunian small shelly fauna of southern Shaanxi Province, South China. Qinscyphus necopinus has a cup‐shaped profile, with slightly raised annuli and five groups of triangular thickenings in pentaradial symmetry. This organism has a comparable morphology to, and thus a close affinity with, Olivooides and Quadrapyrgites, and is interpreted as a coronate scyphozoan. This discovery adds a new crown‐group cnidarian to the Cambrian Explosion.     

New species of the myrmecophile Polyplocotes Westwood (Coleoptera: Ptinidae) from South Australia

Six new species of the Australian myrmecophilous ptinid genus Polyplocotes are described from South Australia. Three are from the deserts of central Australia, one from the Franklin Islands in the Great Australian Bight, one from Eyre Peninsula and one from the Riverland region. Morphologically, the majority of these new species are conventional Polyplocotes , but two are less typical. The characters uniting the genus are explored in the discussion, and comparisons are made to related genera. Although the six new species described here have not been observed in the field, the species of this genus are known to be myrmecophilous, and ant – beetle interactions similar to those seen in other spider beetles might occur between these new species and their host ants.     

Morphology and ontogeny of the eodiscoid trilobite Sinodiscus changyangensis from the lower Cambrian of South China

Abstract: A large number of complete specimens together with numerous disarticulated sclerites of the eodiscinid trilobite Sinodiscus changyangensis Zhang in Zhou et al., 1977 have been collected from the lower Cambrian Shuijingtuo Formation in Changyang, Hubei Province, South China. An ontogenetic series is established based on the immature and mature exoskeletons including the previously unknown protaspides and meraspides, in particular. No further substages can be differentiated in the protaspid specimens herein. Changes that took place during the meraspid period include the addition of postcephalic segments and prominent pygidial larval notches in early meraspid development which became progressively less distinct and disappeared in degree 2. Two holaspid stages are recognized based on the addition of a new pygidial segment, indicating that the start of the holaspid phase preceded the onset of the epimorphic phase and accordingly, its developmental mode is attributed to the protarthrous pattern. The trunk segmentation schedule of S. changyangensis is discussed, which is similar to other primitive eodiscoid trilobites, that is, as the boundary between the thorax and pygidium migrated posteriorly, there is no change in the number of the trunk segments. The processes of liberation of the thoracic segment and segment insertion into the pygidium are separated from one another, and the two different mechanisms, somitogenesis and tagmosis, progress independently during the ontogenetic development of the postcephalic region of these primitive eodiscinids.