Shelly fossils from the lower Cambrian White Point Conglomerate, Kangaroo Island, South Australia
The lower Cambrian (Series 2) White Point Conglomerate (WPC) on Kangaroo Island, South Australia contains exotic clasts representing a diverse array of lithologies, including metamorphics, chert, sandstone, and abundant carbonates, notably archaeocyath-rich bioclastic limestone. Acetic acid digestion of the WPC bioclastic limestone clasts reveals a diverse shelly fauna. This assemblage includes abundant organophosphatic brachiopods such as Cordatia erinae Brock and Claybourn gen. et sp. nov., Curdus pararaensis, Eodicellomus elkaniformiis, Eohadrotreta sp. cf. E. zhenbaensis, Eoobolus sp., Kyrshabaktella davidii, and Schizopholis yorkensis. Additional shelly taxa include the solenopleurid trilobite Trachoparia? sp., the tommotiids Dailyatia odyssei, Dailyatia decobruta Betts sp. nov., Kelanella sp., and Lapworthella fasciculata, spines of the bradoriid arthropod Mongolitubulus squamifer, and several problematica, such as Stoibostrombus crenulatus and a variety of tubular forms. The upper age limit for the WPC is constrained by biostratigraphic data from the overlying Marsden Sandstone and Emu Bay Shale, which are no younger than the Pararaia janeae Trilobite Zone (Cambrian Series 2, Stage 4). The shelly fossil assemblage from the WPC limestone clasts indicates an upper Dailyatia odyssei Zone (= Pararaia tatei to lower P. janeae trilobite zones), equivalent to the Atdabanian-early Botoman of the Siberian scheme. This contrasts with the previously suggested late Botoman age for the limestone clasts, based on the diverse archaeocyath assemblage. The minor age difference between the WPC and its fossiliferous limestone clasts suggests relatively rapid reworking of biohermal buildups during tectonically-active phases of deposition in the Stansbury Basin.
New Anatomical Information on 'Anomalocaris' from the Cambrian Emu Bay Shale of South Australia and a Reassessment of its Inferred Predatory Habits
Two species of 'Anomalocaris' co-occur in the Emu Bay Shale (Cambrian Series 2, Stage 4) at Big Gully, Kangaroo Island. Frontal appendages of 'Anomalocaris briggsi' Nedin, 1995, are more common than those of 'Anomalocaris cf. canadensis' Whiteaves, 1892, at a quarry inland of the wave-cut platform site from which these species were originally described. An oral cone has the three large, node-bearing plates recently documented for 'Anomalocaris canadensis', confirming that 'Anomalocaris' lacks a tetraradial 'Peytoia' oral cone and strengthening the case for the identity of the Australian specimens as 'Anomalocaris'. Disarticulated anomalocaridid body flaps are more numerous in the Emu Bay Shale than in other localities, and they preserve anatomical details not recognized elsewhere. Transverse lines on the anterior part of the flaps, interpreted as strengthening rays or veins in previous descriptions of anomalocaridids, are associated with internal structures consisting of a series of well-bounded, striated blocks or bars. Their structure is consistent with a structural function imparting strength to the body flaps. Setal structures consisting of a series of lanceolate blades are similar to those of other anomalocaridids and are found in isolation or associated with body flaps. A single specimen also preserves putative gut diverticula. The morphology of the appendages, oral cone, gut diverticula and compound eyes of 'Anomalocaris', along with its large size, suggests that it was an active predator, and specimens of coprolites containing trilobite fragments and trilobites with prominent injuries have been cited as evidence of anomalocaridid predation on trilobites. Based on frontal appendage morphology, 'Anomalocaris briggsi' is inferred to have been a predator of soft-bodied animals exclusively and only 'Anomalocaris cf. canadensis' may have been capable of durophagous predation on trilobites, although predation (including possible cannibalism) by 'Redlichia' could also explain the coprolites and damage to trilobite exoskeletons found in the Emu Bay Shale.
A new lower Cambrian shelly fossil biostratigraphy for South Australia
Definition of early Cambrian chronostratigraphic boundaries is problematic with many subdivisions still awaiting ratification. Integrated multi-proxy data from well-resolved regional-scale schemes are ultimately the key to resolving broader issues of global correlation within the Cambrian. In Australia, early Cambrian biostratigraphy has been based predominantly on trilobites. Phosphatic shelly fauna have great potential as biostratigraphic tools, especially in pre-trilobitic strata because they are widespread and readily preserved, but they have remained underutilised. Here we demonstrate their value in a new biostratigraphic scheme for the early Cambrian of South Australia using a diverse shelly fauna including tommotiids, brachiopods, molluscs and bradoriids. Biostratigraphic data are derived from ten measured stratigraphic sections across the Arrowie Basin, targeting Hawker Group carbonates including the Wilkawillina, Wirrapowie and Ajax limestones and the Mernmerna Formation. The stratigraphic ranges of shelly fossils are predictable and repeatable across the Arrowie Basin, allowing three discrete shelly biozones to be identified, spanning Terreneuvian, Stage 2 to Series 2, Stages 3-4. The 'Kulparina rostrata' Zone (new) and part of the overlying 'Micrina etheridgei' Zone (new) are pre-trilobitic (predominantly Terreneuvian). The Cambrian Series 2, Stage 3 'Dailyatia odyssei' Zone (new) features a very diverse shelly fauna and will be described in detail in a separate publication. These zones provide robust means to correlate Terreneuvian-Series 2 successions in neighbouring coeval basins in Australia, particularly the Stansbury Basin. Wider correlation is possible throughout East Gondwana, and especially with South China.
Nektaspid arthropods from the lower Cambrian Emu Bay Shale Lagerstätte, South Australia, with a reassessment of lamellipedian relationships
The lower Cambrian Emu Bay Shale on Kangaroo Island, South Australia, contains the only known Cambrian Burgess Shale-type biota in Australia. Two new lamellipedian arthropods, 'Emucaris fava' gen. et sp. nov. and Kangacaris zhangi gen. et sp. nov., from the Emu Bay Shale Lagerstätte are described as monotypic genera that are resolved cladistically as a monophyletic group that is sister to Naraoiidae + Liwiidae and classified within the Nektaspida as a new family Emucarididae. Shared derived characters of Emucarididae involve a bipartite, elongate hypostome and elongation of the pygidium relative to the cephalic shield and very short thorax. A monophyletic Liwiidae is composed of 'Liwia' and the Ordovician 'Tariccoia' + 'Soomaspis' but excludes 'Buenaspis', and even the membership of 'Buenaspis' in Nektaspida is contradicted amongst the shortest cladograms. New morphological interpretations favour affinities of 'Kwanyinaspis' with Conciliterga rather than with Aglaspidida, and 'Phytophilaspis' with Petalopleura.
The Emu Bay Shale Konservat-Lagersattte: a view of Cambrian life from East Gondwana
Recent fossil discoveries from the lower Cambrian Emu Bay Shale (EBS) on Kangaroo Island, South Australia, have provided critical insights into the tempo of the Cambrian explosion of animals, such as the origin and seemingly rapid evolution of arthropod compound eyes, as well as extending the geographical ranges of several groups to the East Gondwanan margin, supporting close faunal affinities with South China. The EBS also holds great potential for broadening knowledge on taphonomic pathways involved in the exceptional preservation of fossils in Cambrian Konservat-Lagerstätten. EBS fossils display a range of taphonomic modes for a variety of soft tissues, especially phosphatization and pyritization, in some cases recording a level of anatomical detail that is absent from most Cambrian Konservat-Lagerstätten.
The bivalved arthropods 'Isoxys' and 'Tuzoia' with soft-part preservation from the lower Cambrian Emu Bay Shale Lagerstätte (Kangaroo Island, Australia)
Abundant material from a new quarry excavated in the lower Cambrian Emu Bay Shale (Kangaroo Island, South Australia) and, particularly, the preservation of softbodied features previously unknown from this Burgess Shaletype locality, permit the revision of two bivalved arthropod taxa described in the late 1970s, 'Isoxys communis' and 'Tuzoia australis'. The collections have also produced fossils belonging to two new species: 'Isoxys glaessneri' and 'Tuzoia sp.' Among the soft parts preserved in these taxa are stalked eyes, digestive structures and cephalic and trunk appendages, rivalling in quality and quantity those described from better-known Lagerstätten, notably the lower Cambrian Chengjiang fauna of China and the middle Cambrian Burgess Shale of Canada.
Cambrian stratigraphy and biostratigraphy of the Flinders Ranges and the north coast of Kangaroo Island, South Australia
The lower Cambrian sediments of the Flinders Ranges, South Australia can be divided into three sequence sets. They rest unconformably on the Ediacaran succession. Sequence set ϵ1 comprises lower clastic units overlain by a carbonate dominated marine succession that shows marked lateral and vertical facies changes. Sequence sets ϵ2 and ϵ3 together comprise a largely clastic dominated succession of marginal marine to non-marine sediments with subordinate shallow marine carbonates. Sequence set ϵ1 is richly fossiliferous at some levels with biostratigraphy established for trilobites, archaeocyaths, brachiopods, small shelly fossils, acritarchs and molluscs. The Emu Bay Shale Lagerstätte (Cambrian Series 2) from the north coast of Kangaroo Island occurs within a clastic-rich shelf succession dominated by conglomerate and sandstone. The fossil content is dominated by trilobites in terms of relative abundance and currently over 50 taxa are known including, Anomalocaris, the bivalved arthropods 'Isoxys' and 'Tuzoia', the nektaspids 'Emucaris' and 'Kangacaris', the megacheiran 'Oestokerkus' amongst a variety of other arthropods. Other common taxa include palaeoscolecid worms, 'Myoscolex', sponges, hyoliths, brachiopods, a vetulicolian and several other enigmatic forms. The oldest known well preserved complex arthropod eyes occur in this biota.
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), C1, C2 and C3. Sequence set C1 can be divided into five third-order sequences: C1.0, C1.1A, C1.1B, C1.2 and C1.3. 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 400m 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.
New trilobites from the Lower Cambrian Emu Bay Shale Lagerstätte at Big Gully, Kangaroo Island, South Australia
Two new trilobites from the Lower Cambrian Emu Bay Shale Lagerstätte at Big Gully, Kangaroo Island, are described. 'Megapharanaspis nedini' gen. et sp. nov. is placed in the Megapharanaspidae, a new family of the Emuelloidea. 'Holyoakia simpsoni' sp. nov. represents the first occurrence of the genus outside Antarctica, providing further confirmation of the close faunal affinity between Cambrian trilobite faunas from Australia and East Antarctica. New specimens of 'Redlichia takooensis' are documented that provide new morphological information, including a description of the rostral plate and hypostome.
An early Cambrian faunule from the Koolywurtie Limestone Member (Parara Limestone), Yorke Peninsula, South Australia and its biostratigraphic significance
An early Cambrian shelly faunule from the Koolywurtie Limestone Member (Parara Limestone) at Teppers Knoll on Yorke Peninsula, South Australia, includes lingulate brachiopods, a variety of small shelly fossils such as tommotiids, hyolithelminth tubes and orthothecides, chancelloriid sclerites, sponge spicules, in addition to the oldest known occurrence of the redlichioid trilobite Xela. Correlation using faunas from other South Australian successions suggests that the member, in addition to the archaeocyathan fauna referred to as the 'Syringocnema favus beds', are early Botoman (pre-Pararaia janeae Zone) in age.