88 Proc. Japan Acad., 64, Ser. B (1988) [Vol. 64(B),
23. The Silurian Trilobites of the Asian-Pacific Areas
By Teiichi KOBAYASHI, M. J. A.
(Communicated April 12, 1988)
In the Silurian period trilobites were distributed widely from the Mon- golian geosyncline to Bohemia through Central Asia whence Bumastus barriensis f erganensis, Pseudocheirurus and Encrinurus konghsaensis are reported from Trukestan. In South Asia they are found through the Tethys from place to place, namely in the Central Himalayas, Afghanistan, Iran and Amons and Bithynia of Turkey whence 11 genera in 8 families including the Wenlockian Encrinurus are reported. The Llandoverian is present in Pamir and so the Llandoverian and Ludlovian in Turkey. In the North early and middle Silurian trilobites in 15 genera of 9 families are known in the Siberian platform, the Taimyr peninsula and the New Siberian Islands. Scutellum, Bumastus, Proetus, Cheirurus, Encrinurus, Caly- mene, Phacops and Acanthalma (or Leonaspis) are common genera between the two faunas of Northern and Central Asia. The Arcto-boreal trilobites are traceable easterly to Greenland through the Arctic Canadian islands where the Wenlockian and Ludlovian trilobites have flourished. Recently these faunas were amplified by Norf ord (1981) and Chatterton and Perry (1983). In Southeast Asia the Burmese-Malaysian geosyncline through Thailand is the main route of migration between the Asian and Australian trilobites. Gravicalymene and Burmeisteria are reported to occur in New Zealand. In Victoria, Australia Dalmanitina is Llandoverian, if not Ashgillian. The next younger is the so-called Illaenus band containing endemic Thomastus which is a blind illaenid of late Llandoverian age. Recently Chatterton and Campbell (1980) have described copious faunas of trilobites including 18 Wenlockian species and 8 Ludlovian species from the Yassa-Bowning area, New South Wales among which Goldillaenus, Prantlia etc. are in the former and Scharyia and Staurocephalus in the latter. Strusz (1980) recognized Encrinurus, Corono- cephalus and a new genus, Batocara. In South America the Silurian trilobites of 8 families are known from Bolivia, Argentina and Urguai, but the Scutelluidae, Illaenidae, Encrinuridae and Lichidae, all present in Australia are absent in South America where Andinacaste is an endemic genus of the Calmonidae. Latiproetus is a Pacific genus known widely in the Lower and Middle Silurian rocks in China, Japan, Australia and California, but unknown from South America and also the Arctic region. Chiozoon, Encrinurus (Frajiscutum), Hyrokobe, Ligiscus and Pseudo- proetus are Arcto-boreal genera distributed from Greenland to Canada and the last further westerly into Siberia. Returning to Eastern Asia the Silurian trilobites indigenous to the Mon- golian, Tethyan and the Burmese-Thailand-Malaysia geosynclines are as follows : 1. Mongolian geosyncline : Calmonidae : Dalmaniturus 2. Tethys geosyncline : Homalonotidae : Pamirites No. 4] Siluri an Trilobites Asian-Pacifi c Areas 89
Table I. Distribution of Silurian trilobite families in Asian, Pacific and Arctic areas
3. Burmese-Thailand-Malaysian geosyncline : Proetidae: Malayaproetus Dalmanitidae : Prodontochil, (?) Langgonbole In Moore's Treatise of Invertebrate Paleontology, 1959 the Silurian trilobites of 75 genera of 15 families are distributed among which 44 genera are cosmo- politan or European-N. American genera. There are 16 local genera within Europe. In the remainder Cheirurus (Coronocephalus) and Dalmaniturus are contained as a Chinese and a Central Asiatic genus. As the result of the recent advancement the Chinese genera and subgenera became so numerous as cited below. 1. Scutelluidae : Leioscutellum 2. Illaenidae : Meitanillaenus, Wuchianella 3. Proetidae Cyphoproetinae : Oidalaproetus Warburgellinae : Latiproetus (Latiproetus, Chuanqianoproetus, Xiu- shuiproetus), Prantlia (Zheijiangoproetus) Cornuproetinae : Luo jiashania 90 T. KOBAYASHI [Vol. 64(B),
Tropidocoryphinae: Hypaproetus Aulacopleuridae : Son gkania Cheiruridae : Shichiania Encrinuridae : Tewania Coronocephalinae : Senticucurus (Senticucurus, Coronocephalina, Rong- xiella, Kailia, Coronocephalus Homalonotidae : Liangchiashania Lichidae : Tungilichas Odontopleuridae: Gaotaia Finally 10 endemic genera in 5 families in the Chichibu geosyncline of Japan are as follows : Scutelluidae: Japonoscutellum, Tosacephalus, Illaenoscutellum Proetidae: Gomites, Hitoeganella Sphaerexochidae : Sphaerexochus (Onukia) Encrinuridae : Ichiyamella Lichidae : Apolichas, Metaleiolichas, Paraleiolichas. These indigenous genera define the above areas as biological provinces or regions in Eastern Asia.
References
Branisa, L. (1965) : Index fossils of Bolivia, I. Paleozoic. Serv. Geol. Bolivia, Boll. no. 6, 282 pp., 80 pls. Campbell, K. S. W. (1973) : A species of the trilobite Dalmanitina (Dalmanitina) from Australia. Geol. For, i Stockho]lm Forh., 95, pt. 1, 69-77. Chatterton, B. D. E. (1971) : Taxonomy and ontogeny of Silurian-Devonian trilobites from near Yass, New South Wales. Palaeontogr., 1,37-A, 108 pp., 24 pls. (1983) : Silicified Silurian odontopleurid trilobites from the Mackenzie mountains. Palaeontogr. Canadiana, no. 1, 127 pp., 36 pls. Chatterton, B. D. E., and Campbell, K. S. W. (1980) : Silurian trilobites from near Canberra and some related forms from the Yassa basin. Palaeontogr. Abt., A-167, lief. 1-3, 77-119, 16 pls. Chatterton, B. D. E., and Perry, I). C. (1984) : Silurian Cheirurid trilobites from the Mackenzie mountains, Northwestern Canada. ibid., A-184, 78 pp., 15 pls. Holloway, D. (1980) : Middle Silurian trilobites from Arkansas and Oklahoma, U.S.A. Partl. ibid., A-17'0, 1-85, 20 pls. Holloway, D., and Heil, J. V. (1982) : Trilobites from the Mount Ida Formation (late Silurian-early Devonian), Victoria. Proc. Roy. Sac. Vict., 94-3, 133-154, pls. 136-151. Kobayashi, T. (1985a) : On two Silurian trilobite genera, Prantlia and Latiproetus. Proc. Japan Acad., 61B, 419-421. (1985b) : The Silurian Proetidae (Trilobita) in Eastern Asia, ibid., 61B, 422-425. (1986) : On the change of provinciality of the Early Palaeozoic trilobites in South America. ibid., 62B, 221-223. Kobayashi, T., and Hamada, T. (1976) : A new Silurian trilobite from Ofunato, North Japan, ibid., 52, 367-370. Lane, F. D. (1972) : New trilobites from the Silurian of Northeast Greenland with a note on trilobite faunas in pure limestones. Palaeontology, 15(2), 337-364. (1979) : Llandovery trilobites from Washington Land, North Greenland. Gr¢n- lands Geol. Unders. Bull., 131, 5-37, 6 pls. (1984) : Silurian trilobites from Hall Land and Nyeoe Land, eastern North Green- land. Rapp. GrOnlands geol. Unders., 121, 53-75, 3 pls. Lane, F. D., Dawes, F. R., and Peel, J. S. (1980) : A new Silurian Hemiarges (Trilobita) No. 4] Silurian Trilobites Asian-Pacific Areas 91
from North Greenland and the question of the Polaris Habour Formation. Rapp. GrOnlands geol. Unders., 101, 45-53. Lane, F. D., and Owens, R. W. (1982) : Silurian trilobites from Kap Schuchert, Washington Land, western North Greenland. ibid., 108, 41-69, 5 pls. Lane, F. D., and Thomas, A. T. (1978) : Silurian trilobites from NE Queensland and the classification of effaced trilobites. Geol. Mag., 115(5), 351-358. Norford, B. S. (1981) : The trilobite fauna of the Silurian Attawpiskat Formation, Northern Ontario and Northern Manitobe. Geol. Surv. Canada, Bull., 327, 37 pp., 11 pls. Perry, D. G., and Chatterton, B. D. E. (1977) : Silurian (Wenlockian) trilobites from Baillie-Hamilton Island, Canadian Arctic Archipelago. Canadian H. Earth Sc.,14(2), 285-317, 7 pls. Strusz, D. L. (1980) : The Encrinu ridae and related trilobite families with a descrip- tion of Silurian species from Southeastern Australia. Palaeontogr., 168, Lief. 1-4, 68 pp., 6 pls. Thomas, A. T., and Narbonne, G. M. (1979) : Silurian trilobites from Arctic Canada. Geol. Mag., 116(1), 1-80, 5 pls. Zhang Wen-tang (1983) : On the subfamily Coronocephalinae (Trilobita). Palaeon- tology of Cathayana, no. 1, pp. 195-257, 9 pls.