The Origin of Crustacean Biramous Appendages and the Evolution of Arthropoda

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Science  02 Nov 1990:
Vol. 250, Issue 4981, pp. 667-669
DOI: 10.1126/science.250.4981.667


The evolution of biramous appendages in crustaceans is central to the debate on the origin of the arthropods. It is proposed that the biramous limb evolved through the basal fusion of adjacent pairs of ancestrally uniramous appendages. As a result, the existing system of homology, in which uniramous and biramous appendages are considered equivalent, may be invalid. Similarly, the homology of individual body segments between uniramians, such as insects and myriapods, and arthropod groups with biramous limbs is also called into question. Two uniramian segments, or a diplosegment, may be homologous to a single body segment in biramous groups.

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