Bull. Kitakyushu Mus. Nat. Hist., 15: 133-136, pi. 12. March 28, 1996

The First Discovery of a Pterosaur from the Cretaceous Mifune Group, Kyushu, Japan

Yoshihiko Okazaki1 and Naoshi Kitamura2 'Kitakyushu Museum and Institute of Natural History, Nishihonmachi 3, Yahatahigashiku, Kitakyushu 805, Japan 2KumamotoCity Museum, Furukyomachi 3-2, Kumamoto City, 860Japan (Received December 12, 1995)

Abstract A ptcrosaurian wing-finger phalanx is reported from the early Late Cre taceous Mifune Group, Central Kyushu, Japan. This is the first report of pterosaur remains from Southwest Japan, and only the second occurrence from Japan. The presence of the pterosaur adds to the richvertebrate fauna of the Mifune District, which includes carnivorous and herbivorous dinosaurs, turtles, crocodiles, mammals and fishes.

Introduction This report concerns the first record of pterosaurs from Kyushu,Japan. The specimen was collected by the junior author from the river floor, near the Amagimi Dam on Oct. 29, 1992. Although the fossil was included in a flow stone, the matrix is almost the same as that observed in an outcrop near here. The horizon of the fossil, therefore, is the Upper formation of the Mifune Group (presumably Upper Cenomanian-Turonian: Tamura 1990). The location of the present material differs from the localities of carnosaurian and herbivorous dinosaurs, reported by Tamura el al. (1991), but comes from almost the same horizon. The authors express their sincere thanks to Dr. Minoru Tamura, Professor Emeritus, Kumamoto University for his kind guidance of this study. Also, Dr. Yoshikazu Hasegawa, Gunma Museum of Natural History, Dr. Takeshi Setoguchi, Kyoto University, Dr. Makoto Manabe and Dr. Naoki Kohno, National Science Museum, Tokyo, gave us important information during the study. Dr. David M. Unwin, University of Bristol, read manuscript and poited out many suggestion to improve this paper. The members of the Educational board of Mifune-Cho, Kumamoto City Museum, and Kitakyushu Museum and Institute of Natural History also helped the authors with the study of this specimen. 134 Yoshihiko Okazaki and Naoshi Kitamura

Systematics

Pterodactyloidea, fam., gen. and sp. undetermined Material: Proximal part of the left first wing-finger phalanx. Found by Naoshi Kitamura on Oct. 29, 1992. Held at Kumamoto City Museum (KCM VP 000,120) Locality: Upper stream of the Amagimi Dam, 32°44'15'' N, 130°50'45" E. Horizon: Upper Mifune Group (presumably Upper Cenomanian-Turonian) Description: The material consists of a slender and straight shaft with proximal articulation, but broken at the distal end. The shaft is almost straight and has an oval cross-section. The surface of the shaft is almost smooth, but there are several longitudinal breaks caused by compaction. The proximal end is expanded and bares two concave articular facets, both elongated antero-posteriorly. The proximal projection is not preserved. The dorsal surface of the shaft adjacent to the articulation has a somewhat rugose surface. There is a shallow groove at one third anterior. The ventral surface of the shaft near the articulation is rather smooth, with a distinct foramen toward the posterior margin. The bone wall of the shaft is very thin. At the broken end, a smooth internal

Figure 1. Locality of the pterosaur fossil. O locality of the pterosaur X localities ofdinosaurs ®±itiiS!£S§fi:<7)25,OOOfrc7) 1 mm r«j r£ffi< First Cretaceous Pterosaur from Kyushu 135 surface with fine transverse grooves is observed. The grooves have somewhat similar intervals, sometimes bifurcating posteriorly.

Measurements (in mm) total length as preserved 121.3 anterior-posterior diameter of proximal end 25.7 dorsal-ventral diameter of proximal end 10.8 anterior-posterior diameter of distal end 10.0 dorsal-ventral diameter of distal end 4.4

Discussion

The present material is a bone of a pterosaur, as shown by its slender, straight shaft, and the very thin and compact nature of the bone walls. The proximal articulation baring two elongated facets indicates that the material is the first wing- finger pharanx. Although there is wide diversity in their size, wing-finger pharanges have a uniform morphology and are difficult to identify, even to the family level. The present material shows close similarity to several pterosaurids, including the Early Cretaceous Dsungariplems weii Young reported from the Jungar basin, Northwest China (Young 1964; Young 1973), and Pteranodon from the Late Cretaceous North America (Eaton 1910). Differences between the Mifune specimen and Dsungaripterus weii, such as the angle between the shaft and the articular facets, may fefrect postdepositional compaction and diagenesis of the fossil. The present material is ofjuvenile or sub-adult, because the proximal projection is an epiphysis, and is often lost in juvenile and sub-adult animals. The present material is too fragmcntal to suppose whole feature of the animal. If the profile of the present animals is similar to that of Dsungaripterus, the wing span of it may less than two meters. In Japan there is only one report of a pterosaurid. The specimen, from Hokkaido, includes a femur(?) and other bones, and is reported from the Santonian to Campanian Yezo Group of Mikasa City, Hokkaido (Obata, Hasegawa and Otsuka 1972). Thus, the Mifune specimen is the second occurrence of pterosaurs fossil from Japan. The Mifune Group has yielded many fossils of carnosaurian and herbivorous dinosaurs (Tamura, el al. 1991: Hasegawa el al. 1992), crocodiles, a mammal, turtles, and fishes and is the most significant vertebrate fauna among the Southwestern Japanese Mesozoic faunas. 136 Yoshihiko Okazaki and Naoshi Kitamura

References

Eaton, G. F. 1910. Osteology of Pteranodon. Mem. Acad. Arts Sci., vol. 2: 1-38, pis. 1-31, New Haven. Hasegawa Y., M. Murata, K. Wasada, and M. Manabe. 1992. The First Carnosaur (Saurischia; Thcropoda) from Japan: A Tooth from the Cenomanian Mifune Group of Kyushu. Sci. Rep. Yokohama Natl. Univ., Sec. II, No. 39: 41-49.; Yokohama Obata,I., Y. Hasegawa, and H. Otsuka. 1972. Preliminary report on the Cretaceous reptile fossils from Hokkaido. Mem. Natl. Sci. Mus., 5: 213-222; Tokyo. Okazaki, Y. and N. Kitamura. 1993. A pterosaur Fossil from the Mifune Group, Kyushu. Abstr. 142nd Regular Meeting Palaeontol. Soc. Japan, p. 27; Osaka, (inJapanese) Tamura, M. 1990. Stratigraphic and Palaeontologic Studies on Non-marine Cretaceous Bivalve Faunas in Southwest Japan. Mem. Fac. Educ, Kumamoto Univ., No. 39, Nat. Sci. Spec. Vol. 1- 47.; Kumamoto (in Japanese with English abstract) Tamura M., Y. Okazaki, and N. Ikegami. 1991. Occurrence of Carnosaurian and Herbivorous Dinosaurs from Upper Formation of Mifune Group, Japan. Mem. Fac. Educ, Kumamoto Univ., No. 40, Natural Sci., 31-45; Kumamoto (inJapanese with English abstract) Wellnhofer, P. 1991. The Illustrated Encyclopedia of Pterosaurs. 192 pp., Crescent Books, New York. Young, C. C. 1964. On a new pterosaurian from Sinkiang, China. Vertebrata PalAsiatica, 8: 221— 253, pis. 1-2.; Beijing (in Chinese with English Text) Young, C. C. 1973. Pterosaurs from Wuerho. Mem. Inst. Vert. Paleontol. Paleoanthropol. Acad. Sinica, No. 11. Reports of Paleontological Expedition to Sinkiang (II), Pterosaurian Fauna from Wuerho, Sinkiang. pp. 18-35, pis. 1-6. Beijing (in Chinese) The First Discovery of a Pterosaur from the Cretaceous Mifune Group, Kyushu, Japan

Yoshihiko Okazaki and Naoshi Kitamura

Plate 12 Explanation of Plate 12

Pterodactyloidea, fam., gen. and sp. undetermined Proximal part of the left first wing-finger pharanx. la: anterior view lb: ventral view lc: posterior view Id: dorsal view 2: structure of internal surface of the bone wall Okazaki, Y and Kitamura, X. First Cretaceous Pterosaur from Kyushu Plate 12