TT 81-52170
A LIST OF VERTEBRATE FOSSILS FROM SHIMANE PREFECTURE, JAPAN
K. Hirota*
*
Original citation: Hirota, K. 1979. Shimane-ken San Sekitsuidobutsu Kaseki Mokuroku. Fossil Club Bulletin
12:21–27. Translated for the Smithsonian Institution Libraries and the National Science Foundation , Washington,
D.C., by Amerind Publishing Co. Pvt. Ltd., New Delhi, 1983. Transferred to electronic copy and edited by Mark
Uhen and Michell Kwon, Smithsonian Institution, 2008.
VERTEBRATE FOSSILS FROM SHIMANE PREFECTURE
K. Hirota*
*Department of Geology and Mineralogy, Faculty of Science, Kyoto University.
INTRODUCTION
In the deposits of Shimane Prefecture, Mesozoic and Paleozoic formations are found in
the southwest region while Tertiary and Quaternary formations are distributed in the belts
parallel to the coastline (Nishiyama and Miura, 1963). The strata in which vertebrate fossil occur
are the Hata Formation (early Miocene), Masuda Group, Togane Formation, Bihoku Group,
Tadaura Formation, Josoji Formation, Kuri Formation and Aijiro Formation (middle Miocene),
Furue Formation, Fujina Formation, Dogo Formation and Matsue Formation (late Miocene) and
Tsunozu Group (Pliocene–Pleistocene). However, only one fossil Desmostylus japonicus has
been identified so far. The majority of vertebrate fossils from Shimane Prefecture have not been
listed. Hence the author undertook the work of listing the fossils under the guidance of Dr. T.
Okuba and presented the same in the form of a diploma project at Shimane University (Hirota ,
1979 MS).
Here, the author presents a summary of his thesis and gives a list of the fossils. This
paper does not give details of the fossils or the stratigraphy of the region where the fossils were
found. For want of space, only a few representative photographs of fossils are presented in the
plates.
Fig. 1 shows the geographical regions where the fossils were collected. The number
indicates the sites. Fig. 2 is in the form of a table of the fossils. Instead of numbers which might
create confusion, codes are used for the different fossils.
The exact sites of fossil discoveries are not shown in the figure. Odontaspis cuspidata
Agassiz (Nino, 1934) and Paleoloxoden nauman (Makiyama (Kamei, 1967) have been obtained
from the floor of the Sea of Japan off Senei.
20 21 22
Fig. 1. Localities where the fossils were found (Shimane Prefecture).
• – fossil site, o – city or town.
Key: 1 – Masuta; 2 – Hamada; 3 – Oda; 4 – Izumo; 5 – Matsue; 6 – Kaikyo.
During the course of this study, the author received valuable data on Chondrichthyes
from Dr. Coto (Tsurumi University), Dr. Itoigawa (Nagoya University), Mr. Kuge (Kyoto
University) and also regarding Pterygopodites from Dr. Hasegawa (Yokohama University), Mr.
Nishikatsu (Saitama University) and Drs. Kamei and Okazaki (Kyoto University). The author
expresses his thanks to all of them. The author is very grateful to Dr. Okubo (Shimane
University) for his valuable guidance in this study and to Dr. Kamei for reviewing the
manuscript.
Place
Period
Pliocene
Miocene
Masuda
Hamada
Gotsizu
®◊
Izumo
Yado
Raiji
Matsue
Shimane
Hanto
Ara
saki
late
middle
∆O
∆◊
◊∆
◊∆
∆ ◊O
◊
◊O
O
O
◊O
∆ ◊O
∆
early
∆ Chondrichthyes O Osteichthyes ® Reptilia ◊ Mammalia
Fig. 2. Fossils – a general view.
SITES AND FOSSILS
Site No. 1. Hoda, Mihonoseki, Yataba-gun
Strata. Black shale layer with well-developed lamination – Cone layer (middle Miocene).
Fossils. Clupeidae, gen. et sp. indet. Most of the fossils were obtained in the form of
loose bones. Complete specimens measured less than 10 cm in length.
Collector. Yamamoto (1978 MS).
Site No. 2. Chikumi, Mihonoseki, Yataba-gun
Strata. Sandstone layer rich in shale (middle Miocene).
Fossils. 1 – Cetacea, gen. et sp. indet. Vertebra 3 cm in diameter and about 10 cm in
length. The vertebra had a neural spine.
2 – Cetacea, gen. et sp. indet. Three vertebrae measuring 15 cm in diameter and about
100 cm in length. Neural spines 30 cm in length.
3 – Cetacea, gen. et sp. indet. Skull, about 22 cm long and about 18 cm wide. The skull
was cracked almost vertically in the center.
4 – Odontoceti, gen. et sp. indet. Skull, about 70 cm long and about 50 cm wide, along
with teeth, ribs and other bones.
Collector. Okubo, Fujita and Hirota (1978).
Site No. 3. Mitsu, Kashima-machi , Yataba-gun.
Strata. Clay stone embedded in a calcareous rock layer in the form of lenses (middle
Miocene).
Fossils. Osteichthyes, gen. et sp. indet. According to Hitachi (1970 MS), vertebrae of
fishes were found in the clay stone. However, the report does not mention the site.
Collector. Hitachi (1970 MS).
Site No. 4. Gito, Higashi Nagae-machi, Matsue-chi.
Strata. Furue Formation (upper Miocene).
Fossils. Cetacea, gen. et sp. indet. The fossils were of caudal vertebrae filled with quartz.
Seven vertebrae were collected. The largest of them measured 10 cm in diameter and 10 cm in
length.
Collectors. Nakashima, T. and Nakashima, E. (1967).
Site No. 5. Hataketani, Nishinagae-machi, Matsue.
Strata. Black shale - Cone layer (middle Miocene).
Fossils. Clupeidae, gen. et sp. indet. Several skeletons and scales. However, these were
not well preserved.
Collectors. San’i Geology Hiking group.
Site No. 6. Koizu-Machi,, Hirata-shi.
Strata. Black shale - Cone layer - Seisoji Formation (middle Miocene).
Fossils. Fossils of fish scales measuring about 2 mm in diameter. Pattern on the scales
was indistinct.
Collector. Okubo (1976).
Site No. 7. Tadauchi, Shiozu-machi, Hirata-shi.
Strata. Black shale (middle Miocene).
Fossils. Clupeidae, gen. et sp. indet. Fish scales 2–4 mm in diameter. Lateral grooves
well developed.
Collectors. Suahiro and Hirota, 1978.
Site No. 8. Uchida and other places, Kawashita-machi, Hirata-shi.
Strata. Calcareous sandstone - Sodai Formation (middle Miocene).
Fossils. Mammalia, gen. et sp. indet. Bone identified as femur. While the head was very
distinct the shaft was almost missing.
Collector. Not known.
Strata. Black shale (mid-Miocene).
Fossils. Clupeidae, gen. et sp. indet. A complete fossil of a fish. It is yet to be excavated,
but appears to be well preserved.
Collectors. Students of Shimane University (1978).
Site No. 9. Sakita, Higashi Izumo-machi, Yataba-gun.
Strata. Sandstone - Fujina Formation (upper Miocene).
Fossils. Cetacea, gen. et sp. indet. Although excavated no definite specimen was present.
Collector. Takebayashi (1970 MS).
Site No. 10. Umagata-cho, Yahata-machi, Matsue-shi.
Strata. Calcareous siltstone with lamination Matsue Formation (upper Pliocene).
Fossils. Xenocypris sp. Several pieces found lying one above the other. The fish fossils
excavated are well preserved. External features of the skeletons are clear. A few other forms
have also been reported (Sato, 1974).
Collectors. Students of Shimane University.
Site No. 11. Neighborhood of the valley in Agenoki-machi, Matsue-shi.
Strata. Fine grains of sandstone - Fushina Formation (upper Miocene).
Fossils. 1 – Isurus hastalis (Agassiz), 2 – Isurus retroflexus (Agassiz), 3 -– Isurus sp., 4 –
Carcharhinus priscus (Agassiz), 5 – Pristis sp., 6 – Carcharhinus sp. and 7 – Galeocerdo
aduncus Agassiz. Specimens 1-7 were obtained in the form of fossil teeth (Same); there were
more than 300. While some of these were intact and complete others lacked roots. 8 – Pinnipedia
gen. et sp indet. Cheek teeth resembling those of Eumetopias jubata were excavated. 9 – Cetacea
gen. et sp. indet. Mostly bony parts including cervical vertebrae were excavated. Teeth were also
collected.
Collectors. Specimens 1 to 7 were found by students of Shimane University, specimen 8
by Tanabe and specimen 9 by Hirota.
Site No. 12. Yagumo-mura, Yataba-gun.
Strata. Black shale (middle Miocene).
Fossils. Clupeidae, gen. et sp. indet. A few fossils are said to have been excavated.
Collector. Not known.
Site No. 13. Nokifuji-machi, Matsue-shi (Anamichi Chogan).
Strata. Fujina Formation (upper Miocene).
Fossils. Desmostylus japonicus Tok. et Iwa. Molars excavated. Site located by Sakei
(1935).
Collector. Iwasa in 1890.
Site No. 14. Nokifuji-machi, Matsue-shi (in front of the power station).
Strata. Medium-grained sandstone - Fujina Formation (upper Miocene).
Fossils. Isurus hastalis (Agassiz). Only one tooth
excavated.
Collector. Tanabe, 1978.
Site No. 15. Jakuzan, Fujina, Tamagata-machi, Yataba-gun.
Strata. Blue-ash colored siltstone - Fujina Formation (Upper Miocene).
Fossils. 1 – Carcharhinus pristis (Agassiz). Two upper molars were located. 2 –
Pinnipedia gen. et sp. indet. Incomplete conical teeth with a maximum diameter of 13 mm and a
height of 28 mm. Appear to be canines.
Site No. 16. Fujina, Tamagata-machi, Yataba-gun.
Strata. Nodules in medium-grained sandstone layers – Fujina Formation (upper
Miocene).
Fossils. Rib-like fossil bones measuring about 2 cm in width and about 15 cm in length.
Collector. Kawaguchi, 1977
Site No. 17. Nakaya, Daito-machi , Ohara-gun.
Strata. Fine sandstone – Hata Formation (lower Miocene).
Fossils. Carcharhinus sp. Only the snout found with a few minute teeth (denticles?).
Collectors. Oto et al. (1974); Galeocerdo aduncus Agassiz.
Site No. 18. Iwayamae, Gogata-machi, Yataba-gun.
Strata. Calcareous shale - Kuri Formation (middle Miocene).
Fossils. Clupeidae, gen. et sp indet. Fish scales about 3 mm in diameter.
Collectors. Hiking group of San-i geology.
Site No. 19. Sakura, Yado-machi, Yatsuka-gun.
Strata. Calcareous shale Kuri Formation (middle Miocene).
Fossils. Clupsidae, gen. et sp. indet. Fish scales 2–3 mm in diameter.
Collectors. Hiking group of San-i geology.
Site No. 20. Yanai, Tamagata-machi, Yatsuka-gun.
Strata. Fujina Formation (upper Miocene).
Fossils. Pisces; according to Takeuchi (1961 MS) fish teeth excavated.
Collector. Takeuchi (1961 MS).
Site No. 21. Kagani, Yadtaba-machi, Yataba-gun.
Strata. Fragments of fine-grained sandstone ash or dark ash in color – Fujina Formation
(upper Miocene).
Fossils. 1 – Isurus retroflexus (Agassiz) – central teeth, 2 – Carcharhinus priscus
(Agassiz) – upper jaw teeth.
Collector. 1 and 2 were found by Hirota, 1977.
Site No. 22. Kyochoji , Yado-machi , Yataba-gun.
Strata. Fine grains of sandstone – Fujina Formation (upper Miocene).
Fossils. Carcharhinus priscus (Agassiz). Intact upper jaw tooth.
Collector. Kuga, 1978.
Site No. 23. Kudo - Shiraseki (stone bed) , Yado-machi, Yataba-gun.
Strata. Raiji sandstone – lower part-of Fujina Formation (upper Miocene).
Fossils. 1 – Carcharodon megalodon (Agassiz) , Pl. 1, Figs. 1a and 1b. The specimen
was of dark blue ash color and almost in the shape of an equilateral triangle. Cutting edge of the
tooth was clearly visible. There is also a report on this specimen by Goto (1972). 2 – Isurus
hastalis (Agassiz). Fossil of central tooth; broad and blunt; triangular in shape. 3 – Isurus
retroflexus (Agassiz). Central tooth; thick, long and narrow. 4 – Dicrocerus aff. furcatus Hensel.
Pl. 1, Figs. 2a and 2b. Lower jaw bone in which P2, P3, P4, M2 and M3 were intact.
Collectors. Specimen No. 1 was found by students of Shimane University. Finder of
specimens 2, 3 and 4 – not known.
Site No. 24. Nenami, Mikaya, Nanseki-gun.
Strata. Contrasting to Kawagoshi layer (middle Miocene).
Fossils. Carcharhinus sp. Reported by Okamoto (1959).
Collector. Okamoto (1959).
Site No. 25. Maida, Koimiya-machi, Izumo-shi.
Strata. Fujina Formation (upper Miocene).
Fossils. Odontoceti, gen. et sp. indet. Several bones including ribs in the nodule. It
appears to be the fossil remains of a dolphin.
Collector. Nakanishi.
Site No. 26. Sakamoto, Nishikani Nishi-machi, Izumo-shi.
Strata. Lumps of fine-medium grains of sandstone – Fujina Formation (upper Miocene).
Fossils. 1 – Mammalia gen. et sp. indet. Cross sections of fossil tooth. 2 –
Carcharhinus sp. A few fossil teeth.
Collector. Onishi.
Site No. 27. Oike, Oshioriku-machi, Arakawa-gun.
Strata. Not known – Fujina Formation?
Fossils. Mastdon, only fossil tooth measuring 12 cm in length and 5 cm in diameter and
weighing 700 g. (Maini-chi Shimbun dated September 2, 1969.)
Collector. Akumara, 1966.
Site No. 28. Takahara, Mizuho-machi, Ouchi-gun.
Strata. Coarse grains of sandstone – Bihoku Formation (middle Miocene).
Fossils. 1 – Hexanchus serratissimus (Agassiz). Incomplete specimen. Five acrocephalic
crowns were present. There was no lower acrocephalic tooth in front of the upper. 2 –
Carcharhinus sp. Only the acrocephalic part of the tooth crown was excavated.
Collector. Sakae.
Site No. 29. Tsunozu, Ezu-shi.
Strata. Coarse grains of sandstone - Tsunozu Formation (upper Pliocene).
Fossils. 1 – Stegodon elephantoides (Clift). Part of the lower jaw and part of an incisor.
2 – Cervus (Deperetia) cf. praeonipponicus Shikama. Incomplete left lower jaw with P2 and
P3.
Collector. Specimen 1 in 1955 and specimen 2 in 1957 by Morimoto.
Site No. 30. Anekehama, Kokubu-machi, Hamada-shi.
Strata. Fine grains of sandstone – Karakane Formation (middle Miocene).
Fossils. 1 – Pinnipedia, gen. et sp. indet. Acetabulum Pl. 1, Figs. 3a and 3b) and ulna. 2 –
Cetacea, gen. et sp. indet. Ribs, etc. Many of the specimens appeared to have been decalcified.
Collectors. Miko, Matsuhiro and Hinota in 1978.
Site No. 31. Tagaura, Kokubu-machi, Hamada-shi.
Strata. Fine to coarse grains of sandstone – Karakane Formation (middle Miocene).
Fossils. 1 – Odontaspis macrotus (Agassiz). Acrocephalic part of crown of the specimen
was narrow and long and bent along the hyoid region. The central process in the tooth root
prominently protruded out. 2 – ?Carcharhinus sp. Only the root of a tooth excavated. 3 –
Myliobatis sp. Only a tooth about 10 mm long and 5 mm wide was excavated. 4 – ?Zalophus sp.
(Pl. 1, Fig. 4). An incomplete left lower jaw. Although the shape has not been distorted much,
the symphysis part and the articular process are missing. Canine and premolar (PC2 and PC5)
were intact. 5 – Cetacea, gen. et sp. indet. Skull, ribs, vertebrae, etc.
Collectors. Specimen 1 was found by Terakatsu (1976 MS); Isurus sp. Specimens 2–5
were found by Okubo, Inoue, Tomita and Hirota in 1976.
Site No. 32. Okuda, Yasutomi-machi, Masuta-shi.
Strata. Silt mixed with fine grains of sandstone – Masuta Formation (middle Miocene).
Fossil. Myliobatis sp. Fossil tooth about 3 cm long and about 2 cm thick.
Collectors. Mizutsu, Okubo and Hirota (1979).
Site No. 33. Oku, Nishigo-machi, Arasaki-gun.
Strata. Dogo Formation (upper Miocene).
Fossil. Osteichthyes, gen. et sp. indet. Fossil fish excavated (Takebayashi).
Collector. Takebayashi.
Site No. 34. Torikoshi, Nishigo-machi, Arasaki-gun.
Strata. Black shale - Dogo Formation (upper Miocene).
Fossils. ? Clupeidae, gen. et sp. indet. The skeleton was broken in several pieces and very
badly preserved.
Collector. Kumata et al. (1977 MS).
Site No. 35. Kumi, Gokomura, Arasaki-gun.
Strata. Medium - coarse grains of sandstone - Dogo Formation (upper Miocene).
Fossils. Isurus sp. Tooth with entire root decalcified, only the crown was left.
Collectors. Hirota and Yamazaki in 1979.
Site No. 36. Kotani, Tomanmura, Arasaki-shun.
Strata. Medium grains of sandstone - Dogo Formation (upper Miocene).
Fossils. Cetacea, gen. et sp. indet. Three pieces of bone.
Collector. Yasuzu in 1978.
Site No. 37. Nakazato, Tomanmura, Arasaki-gun.
Strata. Lumps of brownish color, medium grains of sandstone – Dogo Formation (Upper
Miocene).
Fossils. 1 – ?Isurus sp. One specimen was reported. 2 – Cetacea, gen. et sp. indet. Ribs
and some vertebrae.
Collectors. Specimen 1 was found by Idoya and specimen 2 by Hirota (1978).
Site No. 38. Nakamura, Hatamura, Arasaki-gun.
Strata. Dogo Formation (upper Miocene).
Fossils. Osteichthyes, gen. et sp. indet. Fish scales.
Collector. Yesuzu, 1978.
LIST OF FOSSILS
Phylum VERTEBRATA
Class CHONDRICHTHYES
Order Selachii
Family Hexanchidas
1. Hexanchus serratissimus (Agassiz). Site 28.
Order Galeifotmis
Family Odontaspidae
2. Odontaspis macrotus (Agassiz). Site 31.
Family Lamidas
3. Isurus hastalis (Agassiz). Sites 11, 14, 21, 23.
4. I. retroflexus (Agassiz). Sites 11, 23.
5. Isurus sp. Sites 11, 31.
6. Carcharodon megalodon (Agassiz). Site 23.
Family Carcharhinidae
7. Carcharhinus priscus (Agassiz). Sites 11, 15.
8. Carcharhinus sp. Sites 11, 31.
9. Galeocerdo aduncus Agassiz. Site 11.
Order Rajiformis
Family Pristidae
10. Pristis spp . Site 11.
Family Myliobatidae
11. Myliobatis spp. Sites 31, 32.
Family Dasyatidas
12. Dasyatis sp. Site 11.
Class OSTEICHTHYES
Order Cyprinida
Family Cyprinidae
13. Xenocypris sp. Site 10.
Order Clupeida
Family Clupeidae
14. Clupeidae, gen. et sp. indet. Sites 1, 5, 6, 7, 8, 18, 19, 34.
Class REPTILIA
Order Chelonia
Family ?Trionychidae
15. ?Trionyx sp. Site 29.
Class MAMMALIA
Order Desmostylia
Family Desmostylidae
16. Desmostylus japonicus Tok. et Iwa. Site 13.
Order Proboscidea
17. Elephantidae, gen. et sp. indet. Site 27.
18. Stegodon elephantoides (Clift). Site 29.
19. Palaeoloxodom naumanni (Makiyama). Site (floor of Sea of Japan).
Order Artiodactyla
Family Cervidae
20. Dicrocerus aff. furcatus Hensel. Site 23?
21. Cervus (Deperentia) cf. praeonipponicus Shikama, Site 29.
Suborder Suines
22. Sus sp.
Order Carnivora
Suborder Pinnipedia
23. Pinnipedia, gen. et sp. indet. Sites 11, 15, 30.
Family Otariidae
24. ?Zalophus sp. Site 31.
25. Cetacea, gen. et sp. indet. Sites 2, 4, 9, 11, 16, 30, 31, 36, 37.
CONCLUSION
In the present study, a list of fossil vertebrates from Shimane Prefecture has been
compiled. The author regrets that several fossils have been left out as their systematic position
was not known.
Regarding the occurrence of fossils, it was found that the fish scale fossils occurred
mostly in shale; fossil teeth of sharks were mostly found in medium grains of sand stone - fine
glauconite; bone fossils were found in fine-medium-grained sandstone.
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PLATE 1
Figs. 1a, 1b - Carcharodon megalodon (Agassiz).
Figs. 2a, 2b - Dicrocerus aff. furcatus Hensel.
Figs. 3a, 3b - Pinnipedia, gen. et sp. indet.
Fig. 4.
- ? Zalophus sp. (Enaliarctos)