stemarthropod
Stem arthropod is a term used in evolutionary biology to describe organisms that lie on the stem lineage leading to the crown group of Arthropoda. In other words, stem arthropods are more closely related to modern arthropods (insects, crustaceans, myriapods, and chelicerates) than to other living animals, but they are outside the last common ancestor of all living arthropods. The concept helps scientists study the origin and early evolution of arthropods by focusing on transitional forms rather than defining a formal clade.
Morphology of stem arthropods is typically mosaic, combining primitive and derived features. They often show segmentation
Most known stem arthropods come from Cambrian deposits and include a range of organisms such as radiodonts