Yu-Yun Chen　　 Master Thesis Abstract Fin and gill morphology of aulopiforms and their phylogenetic implication 　　Aulopoids are small marine pelagic fishes which distributed both in shallow and/or deep waters. Characteristics include presence of adipose fin,caudal fin forked, second pharyngobranchial greatly elongated and posterolaterally extended away from third pharyngobranchial, and presence of uncinate process of second epibranchial contacting third pbaryngobranchial. However, aulopoids have been believed the sister group of myctophoids. Rosen proposed that acanthomorpbs should be the sister group of myctopboids,while aulopoids are the sister group of the myctophoids and acanthomorphs, These two hypotheses lack convincible synapomorphic characters.The present study reveals seven synapomorphic characters to support the hypothesis indicating the monophyly of myctophoids and aulopoids, and they should be allocated in the Order Aulopiformes. Other evidences relevant to the interrelationships of aulopoid families were also found.Four monophyletic groups in the Aulopiformes are recommanded; A:Aulopodidae; B:Chlorophthalmidae; C: Synodontidae, Harpadontidae, Paralepididae; D:Myctophidae, Neoscopelidae. These results contradict with Johnson's proposal in the monophyly of Chlorophthalmidae, Myctophidae and Neoscopelidae. Further studies are needed to find out the interrelationships of the above mentioned four major aulopoid groups.