Evolution of the upper jaw mechanism in
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JR Theodore H. Eaton
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Article
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1935
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John Wiley and Sons
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English
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## Abstract This study reveals the existence of four distinct but genetically related types of upper jaw mechanisms: 1. The nonβprotractile, with no mechanism for the protrusion of the preβmaxillae. The maxillaries form part of the upper margin of the mouth, as in Isospondyli, Apodes and Haplomi.