Great appendage


Great appendages are claw-like appendages which attach to the heads of the "great appendage arthropods", a name usually refers to Megacheira, a class of extinct arthropod characterized by a pair of "short-great appendages" bearing in front of the animal's head.
, showing great appendages with elongated flagella.
In general, megacheiran's great appendage have 6 segments, with the promixal two segments forming a peduncle and the finger-like distal four segments forming a claw, both connect by an elbow joint. Great appendages are interpret as raptorial limbs involved in predation, with those of some genus such as Yohoia are structurally comparable to the raptorial maxillipeds of mantis shrimp. While the great appendages of leanchoilid megacheirans such as Leanchoilia and Yawunik have elongated flagella, suggest a sensory role alongside predatory function.
 have multi-segmented frontal appendages, which are suggested to be either homologous or non-homologous with the megacheiran's great appendages.
Radiodont's frontal appendages have controversial relationships to those of the megacheirans. They have been suggested to be homologous with the antennule of the euarthropods, or the chelicerae of chelicerates, although the latter possibility had been discounted by some authors. Later observations reject the homology of this two type of "great appendages", with neural structures clarifying the segmental affinities of radiodont frontal appendages as protocerebral, and megacheiran's short-great appendages as deutocerebral. Similar appendages also found in other Cambrian arthropods such as Isoxys and Occacaris, but their segmental affinities remain conjectural. On the other hand, a 2020 study suggested that the great/frontal appendages of Megacheirans, Isoxyids and Radiodontans to be homologous, and that the presence of a great appendage is the ancestral condition for Euarthropoda.