A Second Specimen of the Crossognathiform Fish Apsopelix miyazakii from the Cretaceous Yezo Group of Mikasa Area, Central Hokkaido, Japan

Abstract

The specimen collected from the Cretaceous Yezo Group of Mikasa area, central Hokkaido, Japan by T. Matsumoto and T. Omori in 1955, deposited in the University Museum, the University of Tokyo is determined as a second specimen of Apsopelix miyazakii, which is the crossognathid fish described from Teshionakagawa area, northern part of Hokkaido in 2012. Some characters unconfirmed in the holotype, including the dorsoventrally long opercle and subopercle; the well-preserved preopercle having many radial openings of the sensory canal; the sensory canal of the second infraorbital bone having many branches; the presence of the forth infraorbital bone; the large supracleithrum; and the scale-like postcleithrum are preserved in the second specimen. An estimated standard length of the second specimen is more than about 10 cm larger than that of the holotype. The emended diagnosis is proposed for A. miyazakii based on the holotype and the second specimen. The discovery of the second specimen extends the range of A. miyazakii throughout the Upper Turonian. Also, Apsopelix miyazakii possibly lived in a shelf environment near the open ocean.