Researchers Describe Second Opabiniid Ever Discovered

A former professor in the Department of Organismic and Evolutionary Biology at Harvard popularized the “weird wonder” stem-group arthropods Opabiniid and Anomalocaris, discovered in the Cambrian Burgess Shale, turning them into icons in popular culture. While the “terror of the Cambrian’ Anomalocaris with its radial mouth and spiny grasping appendages is a radiodont with many relatives, the five-eyed Opabinia—with its distinctive frontal proboscis remains the only Opabiniid ever discovered.

An international team of researchers led by Harvard University confirms that a specimen previously considered a radiodont is an Opabiniid. The new study in Proceedings of the Royal Society B used novel and robust phylogenetic methods to confirm Utaurora comosa as only the second Opabiniid ever discovered and the first in over a century.

Utaurora comosa, found in the 500 million-year-old middle Cambrian Wheeler Formation of Utah, was first described in 2008 as a radiodont.  The author Stephen Pates, the former postdoctoral fellow in the Department of Organismic and Evolutionary Biology (OEB) at Harvard, first encountered the specimen at the University of Kansas Biodiversity Institute & Natural History Museum while a graduate student.

Pates looked at a variety of radiodonts and concluded that this specimen did not fulfil the definition of a real radiodont. Pates collaborated with co-lead author Jo Wolfe, a postdoctoral associate in OEB who examines the links between fossils and modern arthropods, to establish where Utaurora placed best in the tree of life after joining senior author Professor Javier Ortega-group Hernández’s in OEB.