20/03/17 Tom Harvey (Univ. Leicester)
The Cambrian “explosion” under the microscope: exceptionally preserved “small carbonaceous fossils” (SCFs)
The fossil record documents an explosive Cambrian radiation of metazoans and other organisms. In particular, Burgess Shale/Chengjiang/Sirius Passet-type Lagerstätten provide us with staggeringly detailed snapshots of the unfolding drama, via their exceptional preservation of articulated, non-biomineralizing macrofossils. By definition, however, exceptional occurrences tell us little about larger-scale patterns and processes, and in any case, all taphonomic modes are biased to a greater or lesser extent. As a result, many fundamental questions remain, such as when animals first evolved, and whether Burgess Shale-type assemblages are representative of Cambrian communities more generally. To fill some of the gaps, I have focused my attention on small carbonaceous fossils, or SCFs, which are a category of gently-extracted “palynomorphs” that are too large and/or delicate to be routinely recovered using conventional techniques. Although SCFs have been largely overlooked, they are proving to be widespread, and offer a rich complementary dataset for Cambrian palaeobiology. As well as extending the diversity and distribution of various non-biomineralizing “Burgess Shale-type” taxa, SCFs include a variety of “small shellies” preserved as carbonaceous taphomorphs, and also “cryptic” forms that have not previously been documented from the Cambrian, including derived crustaceans and meiofaunal loriciferans. In this talk I will review some of the key discoveries from my recent work on SCFs from western Canada and the Baltic Basin.
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