[6] The spines on the great appendages of leanchoilid megacheirans such as Leanchoilia and Yawunik are elongated into flagella-like structures, suggesting a sensory role alongside predatory function.

The biramous limbs of megacheirans are homonomous (i.e. having little differentiation from each other), with endopods typically divided into seven segments/podomeres, and paddle-shaped exopods, which are fringed with thin lamellae.

[10][11][12] Possible megacheirans include Enalikter described from the Silurian of the United Kingdom, and Bundenbachiellus from the Early Devonian of Germany;[13][14] due to their possession of great appendage-like cephalic appendages.

[16] The Late Cambrian Orsten taxon Oelandocaris typically considered to be a crustacean relative, has also been suggested in some studies to be a megacheiran.

[17] Megacheirans are either suggested to be stem-group chelicerates or stem-group arthropods,[3] with the former hypothesis based on the chelicerae-like morphology of the great appendages[18][19][20] alongside neuroanatomy[21] and the presence of a reduced labrum[22] resembling those of modern chelicerates, it being argued that chelicerae and the great appendages are homologous structures.