Nature, Published online: 01 April 2026; doi:10.1038/s41586-026-10284-2

Megachelicerax cousteaui gen. et sp. nov. is a large soft-bodied arthropod from the middle Cambrian of Utah featuring massive three-segmented chelicerae, along with five pairs of pseudobiramous prosomal limbs with non-foliaceous exopodal rami, and plate-like lamellae-bearing opisthosomal appendages.