We present the first DNA evidence for the relationship of a rare chiton, Choriplax grayi, from one of only eleven individuals ever found since its discovery in 1864. Many ideas have been proposed to explain the strange morphology of this species; our new results suggest another new hypothesis. This molecular phylogeny of chitons allows us to infer that shell reductions have developed separately, using different mechanisms, in two clades of chitons.

Phoronida is a group of enigmatic animals with larva and adults described as separate taxa, sometimes not matched. To date, 10 species and 39 larval forms have been mentioned in the literature. Using morphological and molecular methods, we have studied some phoronid larvae from Vostok Bay, where phoronids are extremely abundant.

The land snail genus Setobaudinia is one of the most speciose of the biodiversity hotspot region of the Western Australian Kimberley. We describe nine new species of Setobaudinia and examine its relationships with other genera showing similar shells. Some genera show few species with wider distribution while other ones, richer in species, are restricted to narrower areas. Shared shell features are generally the result of environmental effects.

We examined competing origin theories (broadly described as young and dispersal-based versus old and vicariant) for the New Zealand biota using Thomisidae as our study group. Modern distributions suggest that some species may support the vicariance model, but our multi-locus approach found that while distinct from Australian relatives, divergence was only 5.3 million years ago. The inference of ancient patterns of speciation from modern lineages may be misleading.

A new Neotropical doryctine genus, Bolivar gen. nov., is described. Phylogenetic relationships of this genus within the Doryctinae and among most of its known species were assessed using DNA sequence data. This genus comprises eight described species, and its origin is probably South American with a subsequent diversification to Central America and Mexico.

Our knowledge of Australia’s animal species is poor, with an estimate of 70% undescribed. The aim of this work was to undertake a systematic study of the poorly known plant bug (Miridae) genus Rayieria, which is endemic to Australia and whose species are commonly associated with Acacia and Eucalyptus. In this work, we document ten new species belonging to this genus and analyse their phylogenetic relationships and association with plants.