New opabiniid diversifies the weirdest wonders of the euarthropod stem group.

Once considered 'weird wonders' of the Cambrian, the emblematic Burgess Shale animals and are now recognized as lower stem-group euarthropods and have provided crucial data for constraining the polarity of key morphological characters in the group. and its relatives (radiodonts) had worldwide distribution and survived until at least the Devonian. However, despite intense study, remains the only formally described opabiniid to date. Here we reinterpret a fossil from the Wheeler Formation of Utah as a new opabiniid, nov. gen. et sp. By visualizing the sample of phylogenetic topologies in treespace, our results fortify support for the position of 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 spatio-temporal ranges within the euarthropod lower stem group.