UNRAVELING EVOLUTIONARY PATTERNS IN THE EARLY CAMBRIAN; A PHYLOGENETIC ANALYSIS OF THE TRILOBITE FAMILY EDELSTEINASPIDIDAE AND THE PALEOBIOGEOGRAPHIC IMPLICATIONS

The earliest evolutionary histories and subsequent radiations of many major trilobite clades in the early Cambrian remain unresolved. Central to the problem is the relationship and divergence of plesiomorphic libristomate (“ptychoparioid”) and corynexochine trilobites. The early Cambrian trilobite Family Edelsteinaspididae presents the unique opportunity to examine a relatively large clade with distinctive morphological characteristics that appear to be related to both “ptychoparioid” and corynexochine trilobites. Edelsteinaspididae is a widespread but hitherto little-studied taxon currently composed of 15 genera with at least 42 reported species. A comprehensive phylogenetic analysis of Edelsteinaspididae is hindered by the rarity and generally poor quality of specimens. Compilation of the sparse material is further complicated due to the global occurrences in North America, Russia and China, with type material and literature often hard to obtain.

To address these problems, this analysis includes well preserved, new samples collected across North American Laurentia; broadening both taxonomic and geographic sampling for a phylogenetic analysis. This study also examines type material, replicas of type material, and images from the primary literature from North America, Russia and China to form the most comprehensive revision of Edelsteinaspididae. The phylogenetic analysis tests the current monophyletic interpretation of Edelsteinaspididae against possible polyphyletic groupings, particularly for species with potential “ptychoparioid” affinities. The analysis both resolves relationships within the group and enhances the understanding of early Cambrian trilobite biogeography by hypothesizing dispersal/vicariance patterns across the paleo-continents and inferring endemic radiations. Future analyses will incorporate these results into broader evolutionary studies on other early Cambrian trilobite clades including “ptychoparioid” and corynexochine trilobites.