South Australian Museum

The rise and diversification of metazoans in the late Ediacaran have been linked to global sea-level changes. However, the regional record of these changes remains ambiguous. Here, we investigate the origin of an unconformity at the base of the Ediacara Member in South Australia that hosts one of the most diverse assemblages of the Ediacara Biota. The unconformity is traceable throughout the Flinders Ranges, creating deep southeast-oriented valleys reaching 280 m in depth and more than 6 km in width. The base of their infill is marked by rip-up clast breccias overlain by gravity-flow deposits interbedded with deep-water siltstone. The succession shallows upward and is capped by wave-reworked sediments that are correlative throughout the basin. We propose that this basal unconformity formed through the propagation of shelf-incising submarine canyons, potentially during a global lowstand. A significant transgression led to their infill and deposition of the Ediacara Member, allowing preservation of the diverse assemblage of the Ediacara Biota.

Most extant beaked whales have reduced dentition of one or two pairs of tusk-like, mandibular teeth that erupt through the gum only in adult males. Additional teeth have been recorded in several species and genera. A juvenile Hector's beaked whale (SAMA M26434) having additional teeth was collected in South Australia and its skeleton and tissues examined. Ultrastructural and chemical data of one additional tooth were obtained using Energy-Dispersive X-ray, Scanning Electron Microscopy and nanoindentation. Skull and skeleton features were consistent with this species: slender mandible, laterally-compressed, triangular main teeth at its tip; short rostrum; narrow vertex; wide, straight-sided gap between premaxillary crests. Analysis of mtDNA and nuclear genes placed M26434 in a clade with conspecifics. A small, additional tooth was found dorsal to each main tooth. It had moderately thick, prismless enamel and a well-defined enamel-dentine junction. Ca and P were the main components of enamel and dentine. Concentrations of P2O5 and MgO were higher in dentine while concentrations of CaO and Na2O were higher in enamel. Mechanical properties of hardness and elastic modulus revealed lower values in dentine than enamel. Simplified microstructure and lower mechanical properties of the enamel point to the additional teeth being vestigial/rudimentary. Beaked whales may hold important clues to the evolutionary significance of additional teeth.

Biotic dispersal between regions is mediated by a suite of geographical, environmental, and biotic factors. Australia and Melanesia-with the latter centred on New Guinea-are geographically proximate regions that show differing abiotic environments and geological histories, providing an opportunity to document how environmental variation may interact with geographical proximity in shaping dispersal and evolution. Here, we present a phylogenomic framework and analysis of dispersal history for geckos in the genus Gehyra, a radiation of similar to 70 species that occur across Australia, Melanesia, and nearby regions. Despite an evident history of numerous overwater dispersals in species groups occurring in Melanesia, we find very low rates of historical dispersal between Australia and Melanesia and no evidence of an increase in dispersal rate as land bridges formed between Australia and New Guinea from the late Miocene onwards. Analyses of body-size evolution suggest that 'giant' large-bodied forms have evolved on islands, but rather than evolving repeatedly on different islands, these are mostly members of a single old clade that dispersed across multiple islands. In contrast to some other Australasian vertebrate radiations, for Gehyra geckos, environmental differences appear to have strongly impeded dispersal between Australia and Melanesia, while also favouring differing trajectories of body size evolution.

A new species of gall midge Yukawadiplosis exocarpi Adair and Kolesik is decribed that causes flower galls on Exocarpos cupressiformis (Santalaceae), a tree endemic to southeast Australia. Infested flowers do not produce fruit. The larva, pupa, male and female are described and illustrated, and the mitochondrial COI gene is sequenced. A new genus, Yukawadiplosis Adair and Kolesik (Cecidomyiidi: Cecidomyiini) is proposed to contain the new species.

The accurate characterization of species diversity is a vital prerequisite for ecological and evolutionary research, as well as conservation. Thus, it is necessary to generate robust hypotheses of species limits based on the inference of evolutionary processes. Integrative species delimitation, the inference of species limits based on multiple sources of evidence, can provide unique insight into species diversity and the processes behind it. Here, we show how community observations can be integrated with standard molecular and phenotypic data sets under an integrative framework to identify the processes generating genetic and phenotypic variation. We implement this approach in Varanus tristis, a widespread and variable complex of Australian monitor lizards. Using genomic, phenotypic (linear and geometric morphometrics, coloration), spatial, and environmental data, we show that disparity in this complex is inconsistent with intraspecific variation and instead suggests that speciation has occurred. Based on our results, we provide an updated taxonomy for this complex and identify the processes that may have been responsible for the geographic sorting of variation. Our workflow provides a guideline for the integrative analysis of several types of data to identify the occurrence and causes of speciation. Furthermore, our study highlights the benefits and caveats associated with community science and machine learning-two tools used here-in taxonomic research.