Modern marine ecosystems were established during the early Palaeozoic radiations of animals, first the 'Cambrian Explosion' and then, some 50 million years later, in the 'Great Ordovician Biodiversification Event.' By tracking the details of diversification through this critical interval, it should be possible to reconstruct not only the dynamics early animal evolution, but also the underlying effects of accruing ecological novelty. Unfortunately, the conventional fossil record represents only a fraction of ancient diversity, while famous 'soft-bodied' biotas such as the Burgess Shale are too rare to provide larger-scale patterns. I propose to circumvent these problems by exploiting a new, largely untapped source of palaeontological data: Burgess Shale-type microfossils. Like their macroscopic counterparts these fossils record the presence of non-biomineralizing organisms, but they also extend the view to include previously unrecorded forms and fine features. More significantly, they are proving to be quite common - to the extent that they can begin to be used to test macroevolutionary hypotheses. Systematic analysis of Burgess Shale-type microfossils through the Middle to Late Cambrian will shed fundamental new light on early evolutionary patterns, not least the poorly known interval between the Cambrian and Ordovician radiations. By integrating this enhanced fossil record with the principles of biological oceanography and macroecology, this study will also provide a unique, evolutionary view of how modern marine ecosystems function. This study will focus on the Western Canada Sedimentary Basin, which contains one of the largest, best preserved and most extensively sampled sequences of early Palaeozoic rocks on Earth. In addition to famously fossiliferous units exposed in the Rocky Mountain Fold and Thrust Belt - including the Burgess Shale itself - strata extend eastwards for over 1000 km in the subsurface, where they have been penetrated by hundreds of petroleum exploration boreholes. These subsurface materials are housed in state-of-the-art storage facilities in Calgary, Alberta and Regina, Saskatchewan and offer a unique opportunity to sample systematically through the whole of the Middle-Late Cambrian, and across an expansive shallow-water platform into continental-margin environments exposed in the Rocky Mountains. Preliminary work in both subsurface and outcrop occurrences has identified an exquisite range of Burgess Shale-type microfossils. More comprehensive sampling and analysis will substantially advance our understanding of early Palaeozoic diversity, macroevolutionary patterns, and the co-evolution of ecosystem function and environments.