(Odontopterygiformes) from the Ashiya Group (Oligocene), Japan

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124 Yoshihiko Okazaki The author expresses his sincere thanks to Mr. Masayuki Sadasue for he kindly donated specimens to study, and Mr. Kuniomi Hirano, Kitakyushu Natural History Society who helped field activities; Also, Dr. Yoshikazu Hasegawa, Yokohama National University, Dr Keiichi Ono, National Science Museum, Osamu Sakamoto, Saitama Prefectural Museum of Natural History, and the persons of the Kitakyushu Museum of Natural History, for their suggestions and encouragements during the study. Systematic description order Odontopterygiformes Howard 1957 Family, genus, and species indet. Mizumaki specimen; left humerus with several fragmental wing bones. 000, 013 KMNH VP SMizumakifig. 1. Locality of the Mizumaki Specimen. X Mizumaki Speciman. 38 Orio Specimen (plotopterygid).
Bony-toothed bird from the Ashiya Group 125 Locality; Yoshida Miyao, near eastern boundary of the Mizumaki-cho, Fukuoka Prefecture, Japan. (130°42'44*E, 33°50'45*N) Horizon; Yamaga Formation, Ashiya Group. Discovery; by a quarry worker in about 1974. Description; Shaft and distal part of humerus preserved, but proximal end destroyed; shaft almost straight, depressed in anconal-palmar direction. Wall of bone shaft compact and very thin, about 2 mm and less than 1mm in thinner part. In articular part, inner surface of the bone wall with weak sponge structure, but in shaft part, inner surfacesmooth. At the brokenpart, where internal mould is observed, six periodical transverse inner ridges are seen in posterior part. Shaft somewhat diagonal in transverse section, with a ridge, compared to deltoid crest, along lateral margin near proximal end. In anconal view, entepicondyle and external condyle prominent. Olecranal fossa shallow. In palmar view, external condyle very prominent, internal condyle also prominent, intercondylar furrow shallow, entepicondyle very prominent. Beside the humer bone, several fragmental long bones are seen in the same slab; (1) Two long bones beside the distal end of the humerus, about 7 cm and 5 cm in length, circular section with shallow longitudinal furrow; may be parts of carpometacarpus. (2) A long bone fragment beside thecentral part ofthe humerus; may be thedigit 2, phalanx 1. Measurements; Followings are measured in mm. total length as preserved (including mould) 619 width of shaft at the narrowest part 33.7 width of shaft at the distal end of deltoid crest 38.6 anconal-palmar thickness at the distal end of deltoid crest 13.1 width of distal articulation 62.9 thickness of distal articulation 33.0 Discussion and conclusion The present specimen of bird humer bone from the Oligocene Ashiya Group is identified as the Odontopterygiformes. This identification is depended on the extraordinal large size of the bone, depressed shape of section in anconal-palmar direction, shallow olecranal fossa, and thin and compact bone wall of the shaft. Present report is the first record of odontopterygid bird from the Ashiya Group. The Ashiya Group yields many fossils of plotopterygid birds as already reported (Hasegawa etal., 1979), but plotopterygid humer is much smaller, with curved shaft and more improminent condyles in its distal articulation. The size of present humerbone is rather large even in the odonjopterygians, and
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(Odontopterygiformes) from the Ashiya Group (Oligocene), Japan

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