The family Emuellidae Pocock, 1970 was established for Emuella Pocock, 1970 and Balcoracania Pocock, 1970 from the Lower Cambrian of South Australia. Based on their peculiar trunk tagmosis, emuellids have been interpreted as the sister group of all other trilobites with dorsal facial sutures, and classified as high as the ordinal level. Cladistic analysis with a range of exemplar taxa of the Olenellina and Redlichiina instead resolves the emuellids within the Redlichiina, with tagmosis into a prothorax and opisthothorax ("telosoma") nonhomologous in olenellines and emuellids. A taxonomic revision of Australian species identifies Balcoracania flindersi as a junior subjective synonym of B. dailyi, whereas the two named species of Emuella are considered to be distinct. Balcoracania dailyi possesses up to 103 thoracic segments, the maximum number recorded in any trilobite

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.

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.

A distinctive group of lobopodians known from Cambrian Stage 5 in western Laurentia includes 'Acinocricus' Conway Morris & Robison, 1988, from the Spence Shale in Utah, and an unnamed species from the Burgess Shale, British Columbia, popularly known as 'Collins' monster'. The temporal gap from their closest relative, the Chengjiang lobopodian 'Luolishania', is bridged by a single, incomplete specimen of a Collins' monster-type lobopodian from the Emu Bay Shale (Cambrian Series 2, Stage 4), Kangaroo Island, South Australia, the first lobopodian discovered in this Konservat-Lagerstätte. Pending formal description of the Burgess Shale species, the Australian specimen is left unassigned to a genus.

The discovery of new palaeoscolecid material (Cycloneuralia) from the Emu Bay Shale Konservat-Lagerstätte of Kangaroo Island, South Australia (Cambrian Series 2, Stage 4) and from the Murero biota of NE Spain (Cambrian Series 3, Stage 5-Drumian) has prompted a reappraisal of 'Palaeoscolex' Whittard, 1953, the genus to which species from these, and other Cambrian localities, have most recently been assigned. Available data from scanning electron microscopy show the presence of 'Hadimopanella'-type sclerites covering the surface of these taxa, permitting taxonomic schemes based on microfossils and whole-body compression fossils to be reconciled. The sclerite pattern, size and shape indicate that several of the Cambrian species assigned to 'Palaeoscolex' need to be reassigned to 'Wronascolex' Ivantsov and Zhuravlev, 2005, a genus originally described from Siberia. The studied material includes 'Wronascolex antiquus' ( Glaessner, 1979) and 'Wronascolex iacoborum sp'. nov. from Kangaroo Island (Australia) and two new specimens of 'Wronascolex'? from the Iberian Ranges (Spain). SEM examination of the types of 'Palaeoscolex ratcliffei' Robison, 1969, a Cambrian species from Utah to which Murero material has been compared, suggests that this species should possibly be assigned to 'Wronascolex'. These taxa are also considered in a Cambrian palaeobiogeographic context, together with the presence of isolated Hadimopanella sclerites, showing a distribution of Wronascolex largely confined to palaeotropical environments.

Background: Vetulicolians are one of the most problematic and controversial Cambrian fossil groups, having been considered as arthropods, chordates, kinorhynchs, or their own phylum. Mounting evidence suggests that vetulicolians are deuterostomes, but affinities to crown-group phyla are unresolved. Results: A new vetulicolian from the Emu Bay Shale Konservat-Lagerstätte, South Australia, 'Nesonektris aldridgei' gen. et sp. nov., preserves an axial, rod-like structure in the posterior body region that resembles a notochord in its morphology and taphonomy, with notable similarity to early decay stages of the notochord of extant cephalochordates and vertebrates. Some of its features are also consistent with other structures, such as a gut or a coelomic cavity. Conclusions: Phylogenetic analyses resolve a monophyletic Vetulicolia as sister-group to tunicates (Urochordata) within crown Chordata, and this holds even if they are scored as unknown for all notochord characters. The hypothesis that the free-swimming vetulicolians are the nearest relatives of tunicates suggests that a perpetual free-living life cycle was primitive for tunicates. Characters of the common ancestor of Vetulicolia + Tunicata include distinct anterior and posterior body regions - the former being non-fusiform and used for filter feeding and the latter originally segmented - plus a terminal mouth, absence of pharyngeal bars, the notochord restricted to the posterior body region, and the gut extending to the end of the tail.