Undescribed cheloniellid / Sidneyia-like arthropod
Middle Cambrian
Wheeler Formation
House Range, Millard Co., Utah, USA

Giant 113mm cheloniellid? arthropod on huge 300mm slab. First we have ever seen. New to science and currently undescribed.

Cheloniellids were marine arthropods that lived during the Paleozoic era, particularly in the Ordovician and Silurian periods, but known from the Cambrian and extending into the Devonian. They had a unique body plan characterized by a cephalon (head) that was fused with a shield-like thorax. Their bodies were covered in a hard exoskeleton, and they likely had multiple pairs of appendages for various functions such as feeding and locomotion.

These organisms are important in the study of arthropod evolution and paleontology, as they represent a unique group with distinct characteristics. However, please note that the knowledge of specific details about cheloniellids may be limited, as our understanding of these extinct organisms continues to evolve with ongoing research and new discoveries.

This new organism seems to share similarities with a smaller Utah taxon called Nettapezoura and could even be a close relative of the huge Burgess Shale taxa Sidneyia. We’ve never seen anything quite like this from the Cambrian of Utah before.