104 Proc. Acad., 55, Ser. B (1979) [Vol. 55(B),

21. Outline of the Carboniferous Trilobites in Japan*'

By Teiichi KOBAYASHI, M. J. A., and Takashi HAMADA University of

(Communicated March 12, 1979)

In the Carboniferous fauna of Japan trilobites have been a small group represented by only five species (Sugiyama, 1944; Okubo,1951; Endo and Matsumoto, 1912), but recently it was considerably am- plified with fresh materials from old and new localities. At present they attain as much as almost six times in specific number, beside some indeterminable forms. These trilobites are classifiable into two major groups which represent the Kitakami trilobite facies (Kt) in non-calcareous rocks in Northeast Japan and the Akiyoshi trilobite facies (Ak) in lime- stones in the Inner Zone of Southwest Japan. None has so far been discovered from the Outer Zone. The trilobites of these two biof acies belong to sixteen genera in two families and seven subfamilies in the Proetidae as follows :

I. Proetinae 1. Proetinae: Pudoproetus (Ak), Conophillipsia (Kt) 2. Cyrtosymbolinae: Archaegonus (Angustibole) (Ak), Waribole (Ak) Phillibole (Kt), Carbonocoryphe (Ak) 3. Phillipsiinae: Phillipsia (Kt) 4. Linguaphillipsiinae: Linguaphillipsia (Kt, Ak), Palaeophillipsia (Kt) 5. Cummingellinae: Cummingella (Ak) 6. Griflithidinae: Grifithidella (Ak), Thigriffides (Ak), Paragrif thides (Ak), Humilogriffithides (Ak) 7. Ditomopyginae: Paladin (Paladin, Weberides) (Kt) II. Brachymetopidae: Brachymetopus (Brachymetopus, Brachymetopella) (Ak) As listed above, the Phillipsinae is restricted to the Kitakami facies and so are the Cummingellinae, Grifithidinae and Brachymeto- pidae to the Akiyoshi facies, but the Proetinae, Cyrtosymbolinae and Linguaphillipsiinae are contained in the two facies. In the generic level, however, there is none common between the two facies. As tabulated here, twenty-nine species of trilobites are now recognized among which some new species were already described (Kobayashi and Hamada, 1978a and b ; Kobayashi and Tachibana, 1978). The remainder's description will be published through a mono- graph now nearly completed. Their source strata are as follows :

'`' Studies on Japanese Trilobites and Associated Fossils -XV. No. 3] Carboniferous Trilobites of Japan 105

I. Kitakami trilobite biofacies in the southern Kitakami mountains. Nagasaka district K : Karaumedate series Hikoroichi-Setamai district Hi : Hikoroichi series Ar : Arizu series On : Onimaru series II. Akiyoshi trilobite biofacies in the Inner Zone of Southwest Japan. A : Akiyoshi limestone in Mr : Marginatia toriyamai zone My : Millerella yowarensis zone M : Millerella zone Ps : Pseudostaff ella antiqua zone Pb : Pro f usulinella beppensis zone Hn : Hina limestone, Prefecture Om : Omi limestone in Prefecture C : Cummingella horizons F : Fusulinella zone The oldest of these trilobites would be Conophillipsia deciseg- menta which is a solitary species in the Karaumedate series, although it yields a few other indeterminable forms. The age of the trilobite is either Etroeungtian or lower Tournaisian. The Hikoroichi series which is generally considered lower Tournaisian contains Phillipsia Linguaphillipsia, Palaeophillipsia and Phillibole. Phillipsia aff, ohmo- rensis in the superjacent Arizu series may be about middle Tour- naisian. The oldest in the Inner Zone is the middle or upper Tournaisian faunule from the Hina limestone which comprises Pudoproetus, Car- bonocaryphe, Grifithidella, Thigrifides and Paragrif ithides. An in- determinable pygidium was collected from the Marginatia toriyamai zone of Akiyoshi-dai whose age is upper Tournaisian or lower Osagean. In the Kitakami mountains the Visean Onimaru series yields some trilobites at Yukizawa among which two species are referable to Paladin (Paladin and Weberides). They are accompanied by an unnamed species of Linguaphillipsia (Araki and Koizumi,1961) which is allied to the Australian species. Cummingella is the leading genus and Brachymetopus the next, both within the range from upper Visean to Bashkirian in the Akiyoshi limestone. Hence the name Cummingella faunule. Cum- mingella is known to occur three or more horizons. The above two genera occur also in the Omi limestone. Cummingella subovalis and Brachymetopus omiensis are two common species between the Omi and Akiyoshi faunules. In the Carboniferous system of Japan the latest trilobite horizon is the lower Moscovian Fusulinella zone of Nishiyama quarry in the Omi limestone which yields Humilogrif iithides taniguchii and Brachy- 106 T. KOBAYASHI and T. HAMADA [Vol. 55(B), metopus japonicus. Linguaphillipsia common in the Hikoroichi district warrants that the early Tournaisian faunule there belongs to the Eurasiatic-Aus- tralian province and the Tethyan sea was the route of the trans- Eurasiatic migration. Such a provinciality appears to have been No. 3] Carboniferous Trilobites of Japan 107 maintained also by the Visean Yukizawa trilobites. In the Nagasaka district adjacently to the west of Hikoroichi, however, occurs Cono- phillipsia which is known from Australia and Turkestan, but unknown from South Asia. Therefore the Mongolian geosyncline was probably its route from Japan to Central Asia. The middle or upper Tournaisian Hina f aunule contains T hi- grifJides typical of North America. GrifJIthidella and Pudoproetus also thrived in the Mississippian sea of the Mid-Continent, although they occur also in the Altai, Central Asia and the Urals on one side and in Australia on the other. Paragri fithides is a rare genus in England and probably in Tienshan. Carbonocoryphe is an important member of the Culm fauna and this is the first occurrence in Asia. The Hina faunule is such an admixture. Nevertheless, it is of great interest to find the faunal connection between Europe and North America through the Mongolian geosyncline. Beside these trilobites it is noted that a pygidium of Cummingella ? sp. is contained in the Hina collection. Cummingella and Brachymetopus are wide spread in the Akiyoshi and Omi limestones. While the latter is cosmopolitan, the former is unknown from North America. These two genera are totally absent in the Culm facies. Because it is well known that Cummingella is a Dinantian genus which, however, survived until the early Namurian in the Donetz basin and the Urals, the Japanese species in the Prof usulinella bep- pensis zone (middle Bashkirian) must be the latest relics. Likewise, the subfamily Cyrtosymbolinae is considered to have died out in the Urals in the early Namurian age. Therefore the authors were sur- prised to see in the collection from the Pseudostaf, f ella antiqua zone (lower Bashkirian) some trilobites which reveal close resemblances with Archaegonus (Angustibole) and Wan bole in their subconical glabellae and other aspects. Waribole and Angustibole are, however, considered to have disappeared before the Namurian age. Further- more, Carbonocoryphe, Waribole and Archaegonus (Angustibole) occur in Japan in limestones with marked contrast to their great development in the Culm facies in Europe. Therefore a further con- firmation is preferable for their generic identification with more materials. Finally, Humilogri fthides is an endemic Moscovian genus to the oriental region where it occurs in South Manchuria and Southwest Japan. Here it is concluded that six or more faunules are recognizable in the Carboniferous trilobites of Japan, namely (1) Karaumedate, (2) Hikoroichi-Arizu, (3) Hina, (4) Yukizawa, (5) Cummingella and 108 T. KOBAYASHIand T. HAMADA [Vol. 55(B),

(6) Humilogrifithides f aunules, beside the indeterminable trilobite of the Marginatia toriyamai zone and more than two trilobite horizons are distinguishable for the second and fifth faunules. They as a whole show the Mongolian and Tethyan geosynclines for the trans-Eurasiatic route of migration at one time and another.

References

Araki, N., and Koizumi, H. (1968) : Permo-Carboniferous trilobites from the Kitakami mountainland. Chigakukenkyu, 19, no. 6, 151-158, 2 pls.; no. 8, 211- 214. Endo, R., and Matsumoto, E. (1962) : Permo-Carboniferous trilobites from Japan. Sc. Rep. Univ., ser. B, 4, no. 2,149-172, pls. 8-10. Hahn, G., and R. (1969, 1970, 1972): Trilobitae carbonici et permici, I-III.. Animalium Catalogus, I, Animalia, pars 12, pp. 1-531. (1975) : Die Trilobiten der Ober-Devon, Karbon and Perm. Gurich und. Kr~mmelbein : Leitf ossilien, 2, 267 pp. Kobayashi, T., and Hamada, T. (1978a) : Lower Carboniferous trilobites from the Hina limestone, Okayama Prefecture, West Japan. Proc. Japan Acad., 54B,, 5-9. (1978b) : Advance Reports on the Carboniferous trilobites of Japan. Ibid.,. ;54B, 45-49. Kobayashi, T., and Tachibana, K. (1978) : A new Carboniferous trilobite from Nagasaka, and its bearing on taxonomy and biogeography.. Ibid., 54B, 262-267. Okubo, M. (1951) : Trilobites from Japan. Earth Sci., no. 4, 133-139, p1.1. Sugiyama, T. (1944) : On the Japanese Trilobites. Sci. Rep. Geol. Miner. Inst. Tokyo Bunrika-Daigaku, 1, 20-30, p1.1.