Once considered ‘weird wonders’ of the Cambrian, the emblematic Burgess Shale animals Anomalocaris and Opabinia are now recognized as lower stem group euarthropods and have provided crucial data for constraining the polarity of key morphological characters in the group. Anomalocaris and its relatives (radiodonts) had a worldwide distribution and survived until at least the Devonian. However, despite intense study, Opabinia remains the only formally described opabiniid to date. Here we reinterpret a fossil from the Wheeler Formation of Utah as a new opabiniid, Utaurora comosa nov. gen. et sp. By visualizing the sample of phylogenetic topologies in treespace, our results fortify support for the position of U. comosa beyond the nodal support traditionally applied. Our phylogenetic evidence expands opabiniids to multiple Cambrian Stages. Our results underscore the power of treespace visualization for resolving imperfectly preserved fossils and expanding the known diversity and spatiotemporal ranges within the euarthropod lower stem group.

Readme file: README.txt

Nexus (.nex) is a common file type for phylogenetic data, and the required runfile to use MrBayes for phylogenetic analysis.

.p are sampled parameter files from MrBayes analysis, output for each run specified.

Newick (.tre) files are phylogenetic tree outputs, which can be visualized directly e.g. with Figtree.

.tnt is a file type for phylogenetic data, specifically the required runfile to conduct maximum parsimony phylogenetic analysis in TNT.