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

Bull. Kitakyusku Mus. Nat. Hist., 9: 123-126. December 31, 1989
An occurrence of fossil bony-toothed bird
(Odontopterygiformes) from the Ashiya
Group (Oligocene), Japan
Yoshihiko Okazaki
Kitakyushu Museum of Natural History, Nishihonmachi 3,
Yahatahigashiku, Kitakyushu 805, Japan.
(Received October 31, 1989)
Abstract An incomplete humer bone of odontopterygid bird is reported from the
Oligocene AshiyaGroup, Northern Kyushu,Japan. The length of humer bone is very
large, suggesting the wing span of about 6 meters. The affinity of marine bird
assemblage of the Ashiya Group to the Iwaki Group, Northeastern Honshu, is empha
sized as they both yield plotopterygid and odontopterygid birds.
Introduction
On December 27 1988, one bone fossil specimen from the Ashiya Group, North
Kyushu was brought to the Kitakyushu Museum of Natural History. That was a
large humer bone ofa bird, reaching 60cmlong, with several fragmental wing-bones.
The specimen had been stored by Mr. Masayuki Sadasue, Principal of the Asagi
Primary School, Onga-cho. He obtained the specimen from a quarry worker of
Mizumaki-cho, through his geological research along the Onga River (mainly sur
veyed in 1974). From the same district, several fossil specimens of plotopterygid
bird have been reported (Hasegawa et al., 1979). But the present specimen is much
larger than plotopterygid humer, that is less than 25 cm. The large size and thin
bone wall indicates the humer to be included in the odontopterygid bird.
The presence of the odontopterygid bird in the Japanese Tertiary has been
reported from five localities (Table 1), from the Oligocene to Pliocene. As the
geological age of the Ashiya vertebrate Fauna (Okazaki 1988, etc.) is Oligocene,
specimens of the Iwaki City are of thesame age among theJapanese odontopterygid
birds.
Table 1. Japanese fossils ofodontopterygid birds
Location Part Age Reference
Mizumaki, Fukuoka Pref. humerus Oligocene present report
Iwaki, Fukushima Pref. rostrum, radius Oligocene Hasegawa et al., 1986
Chichibu, Saitama Pref. quadrate M. Miocene Ono, 1989
Mizunami, Gifu Pref. no report M. Miocene Ono, 1989
Maesawa, Iwate Pref. humerus Pliocene Ono et al., 1985
Kakegawa, Shizuoka Pref. femur Pliocene Ono et al., 1985

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

126 Yoshihiko Okazaki
the estimation of the wing span is attempted. Preserved shaft of the present humer
(61.9 cm, including mould) has weak expansion in its anterior proximal part,
correlated as distal end of the doltoid crest. Lost length of proximal part ofhumer is
estimated as 19.3 cm, calculated from the figure of presented by Lartet, 1857
(Pelagornis miocaenus). Howard (1957) estimated the ratio of wing span against
humer to be 7.29 {Osteodontornis orri; 16 feet/ 593 mm plus 3 inches). The wing span
of the present bird, therefore, is estimated as 592 cm. Internal periodical ridges seen
in the present specimen may serve as reinforce structure of the bone.
As already noted, there are five localities of odontopterygid fossils in Japan.
Among them, Iwaki Formation also yields many plotopterygid birds, and there is
close similarity between these two sediments in this viewpoint. This similarity can
not been traced in cetacean faunas (Okazaki 1988), because the Iwaki Formation
yields scarce cetacean fossils.
Reference
Alexander, R. M. (1989) Dynamics of Dinosaurs and other extinct Giants. Columbia Univ. Press, 150—
151.
Feduccia, A. (1980) The Ageoj Birds. Harvard Univ. Press, 80-81.
Harrison, J. O. and Walker, C. A. (1976) A Review of the bony-toothed birds (Odontopterygiformes):
with descriptions of some new species. Tertiary Res., Spec. Pap. 2: 1-62, pis. 1-10.
Hasegawa, Y. etal. (1979) Preliminary Noteson the Oligo-Miocene Penguin-like Birds from Japan
(Parts 1-7). Bull. Kitakyushu Mus. Nat. Hist. 1: 41-60, pis. 12-19. (inJapanese)
Hasegawa, Y., Ono, K. and Koda, Y. (1986) Odontopterygid bird from the Oligocene Iwaki
Group. Abslr. 1986 Ann. Meeting Palaeontol. Soc. Japan, 24. (inJapanese)
Howard, H. (1957) A gigantic "toothed" marine bird from the Miocene ofCalifornia. Santa Barbara
Mus. Nat. Hist., Dept. Geol. Bull. 1: 1-23, 8 figs.
Howard, H. and Walter, S. L. (1969) A new species of bony-toothed bird (Family Pseudodontornithidae)
from the Tertiary of New Zealand. Proc. Canterbury Mus. 8 (4): 345-357.
Lartet, E. (1857) Note sur un humerus fossild d'oiseau, attribue a un tres grand Palmipeda de la
section des Longipennes. C. r. hebd. Seanc. Acad. Sci., Paris, 44, 736-741, pi. 45.
Okazaki, Y. (1988) Oligocene squalodont (Cetacea: Mammalia) from the Ashiya group, Japan.
Bull. Kitakyushu Mus. Nat. Hist. 8: 75-80, pi. 1.
Ono, K. (1980) Pliocene Tubinare Bird from Kakegawa, Shizuoka Prefecture, Japan. Mem. Natn.
Sci. Mus. 13: 29-34, pi. 2.
Ono, K. (1989) A Bony-toothed Bird from the Middle Miocene, Chichibu Basin, Japan. Bull. Natn.
Sci. Mus., Ser. C, 15 (1): 33-38.
Ono, K., Y. Hasegawa, and T. Kawakami (1985) First record of the Pliocene bony-toothed bird
(Odontopterygiformes) from Japan. Bull. Iwate Pref. Mus. 3: 155-157, pis. 1, 5. (in Japanese with
English Summary)
Scarlet, R. J. (1972) Bone of a presumed Odontopterygian bird from the Miocene of New
Zealand. N. Z.Jour. Geol. Geophys. 15 (2): 269-274.

An occurrence of fossil bony-toothed bird
(Odontopterygiformes) from the Ashiya
Group (Oligocene), Japan
Yoshihiko Okazaki
Plate 1

Explanation of Plate
Plate 1
fig. 1.
fig. 2.
fig. 3.
fig. 4.
Odontopterygiformes, gen. et sp. indet.
KMNH VP 000, 013
Left humerus from Mizumaki-cho, Fukuoka Prefecture,
anconal view
X0.25
section in near deltoid crest
X0.5
close view of distal part
X0.5
palmar view of articulation
X0.5

Okazaki, Y. Bony-toothed bird from the Ashiya Group Plate 1