<i>Polymerichthys</i> sp. (Aulopiformes, Polymerichthyidae) from the Middle MioceneIseyama Formation in Ueda City, Nagano Prefecture, central Japan

<p>A fossil palatine identifiable as the fossil genus Polymerichthys (Aulopiformes, Alepisauroidei, Polymerichthyidae) is reported from the Middle Miocene Iseyama Formation (Serravallian), Ueda City, Nagano Prefecture, central Japan. The palatine arranges six well preserved palatine teeth, and the teeth have a close affinity in morphology with other fossil Polymerichthys specimens. As diagnostic compared the other fossil specimens on the basis of a possible palatine tooth morphology, the tooth is strongly similar to that of Polymerichthys nagurai in the following characteristics: the appearance is slender and saber-like; the tooth tapers toward an apex and inclines anteriorly; and each cutting edge does not possess a barb. The tooth is noteworthy for being anteriorly inclined, a characteristic shared only with Polymerichthys and Anotopterus (Paralepididae), and for not being found anywhere in other teleosts. Polymerichthys sp. from the middle Miocene of Nagano Prefecture represents the second record of polymerchthyid fish from Japan as well as the fifth record from the world. The present fossil evidence concisely suggests that Ueda City and the vicinity in Nagano Prefecture, that is located in the central part of the northern Fossa Magna Region, faced the northwestern Pacific Ocean, at least during the depositional age of the lowest part of the Iseyama Formation. </p>