1. Trilobites O F Thailand and Malaysia

No. 1] Proc. Japan Acad., 57, Ser. B (1981) 1

1. Trilobites of Thailand and Malaysia

By Teiichi KoBAYASHl, M. J. A., and Takashi HAMADA

(Communicated Jan. 12, 1981)

In Thailand and Malaysia Reed (1920) was the first to describe two Carboniferous trilobites from Phattalung, followed by Stubblefield (1948) with another Carboniferous species from Kuantan. Then the senior author (1957, 1961) added several Cambrian ones from Taru- tao Island and a Carboniferous one from Wang Saphung. Subsequently he continued palaeontological studies with the junior author. As the result all of the six Palaeozoic systems were documented with trilobites and one or more trilobite horizons distinguished in each system as summarized below (1-12). 1) Late Upper Cambrian trilobites from the Tarutao sandstone on the west coast of Tarutao Island (1957). Shergold (1975) referred "Sinosaukia" buravasi to his new genus , Mictosaukia. Sun and Xiang (1980) found M. buravasi in the Paoshan shale in West Yunnan and the next older Kaolishania fauna in the Paoshan area. Thus the Feng- shanian age of the Tarutao fauna and its affinity to the Payntonian fauna of Australia are now warranted. The find of Saukiella in the Southern Shan State, Burma (Them, 1973) is a link between West Yunnan and South Thailand. 1-2. Fragmentary Lower Ordovician (?) asaphoids were found in bed- ded limestone at Ko Klong near Tarutao Island. Because of poor preserva- tion, the age of this trilobite horizon is not yet answered. No trilobite is contained in the upper Canadian-lower Chazyan Teiichispira-Discoceras (Hardmannoceras ?) horizon of Pulao Langgon, Langkawi Islands. 2) Middle Ordovician Satun fauna at Khao Sai Phet, Ban Tung Din Lun, near Satun, extreme south of Thailand (1964b). Basiliella satunensis suggests its correlation to the Llandeilian Basiliella yun nanensis fauna of Shihtien, Yunnan. 2-3. The Ormoceras langkawiense horizon of the lower Setul limestone as well as the Actinoceras-Armenoceras horizon extensive in West Thailand and Northwest Malaysia are near the Satun trilobite horizon in age, but they yield no trilobite. The former of the two cephalopod horizons may be a little older and the other somewhat younger than the Satun horizon. 3) Llandeilo-Caradocian Microparia fauna from Tambak, Kedah. (1970). 4) Upper Ordovician Telok Memplam trilobites from the top part of the lower Setul limestone of Pulao Langgon, Langkawi Islands (1978b). 2 T. KOBAYASHI and T. HAMADA [Vol. 57(B),

4a. The Geratrinodus levigatus horizon in the lower red limestone in the range from upper Caradocian to lower Ashgillian. 4b. The Geratrinodus perconvexus horizon in the upper grey limestone, middle Ashgillian in age. 5) Lower Llandeilian Dalmanitina malayensis horizon in the lower Detrital band, Pulao Langgon (1964a). Its correlative in Burma is the Panghsapyge beds yielding Dalmanitina hastingsi (Reed, 1915). Since the authors discussed the Dalm nitina beds near the Ordovician- Silurian boundary in Eurasia (1974) , Lee Yao-Hsi et al. (1975) reported Dalmanitina nanchangensis Lu from the base of the Lower Silurian Lungma shale in the western part of Tapashan, Central China. 6) Upper Llandovery-lower Wenlockian Prodontochile fauna from the basal part of the upper Setul limestone, Pulao Langgon (1971a) . It comprises some 15 species, 9 genera and 8 families of trilobites among which Prodontochile igoi, Sphaerexochus orientalis and Calymene scrivenori are three leading members. P'rodontochile, Malayaproetus and Langgonia are three new genera. Lonchodomas (Metalonchodomas) masjidi f ormis is an unusual relic species of the Raphiophoridae. This fauna is quite distinct from the Panghsapyge, Namhsim and other Silurian faunas. 7) Emsian-Eifelian Pseudotrinodus-Plagiolaria fauna in Thai- land and Malaysia. Plagiolaria (?) orientalis Maximova (1965) is known from the Eifelian of North Viet-Nam and Plagiolaria nandan- ensis Chang (MS) in Yi and Hsiang (1975) from the Eifelian of Kwangsi, China. 7a. The copious Kroh fauna in Kedah contains the above two key genera. Although Plagiolaria poothaii has normal eyes, though small, Pseudotrinodus aenigma (1971b), Blanodalmanites nubelania, Perakaspis trapezoidalis, P. (Krohbole) elongata and other leading members are either blind or de- generated eye bearers. Therefore their habitat was probably the transition from the dysphotic to the aphotic zone. Dismembered carapaces of an in- dividual are commonly found together at a spot but isolated from others in a slab. These carapaces are, however, not disturbed and little damaged by scavengers. Such a thanatocoenetic site must have been a moulting place in a quiet sea bottom (1972). 7b. Eifelian Plagiolaria poothaii horizon at a locality between Trang and Phattalung, Peninsular Thailand (1968). 7c. Pseudotrinodus eonstrictus collected in association with various other undescribed fossils on the Chong Kaep Yai ridge, Changwat Kanchana- buri, Thailand (1977). 8) Famennian-lower Tournaisian cyrtosymbolid horizons in the Langgon red beds in Northwest Malaysia (1966, 1973). There is no trilobite species common among the following three horizons. 8a. Early Famennian (?) Langgonbole vulgaris horizon of Pulao Lang- gon. No, 1] Trilobites of Thailand and Malaysia 3

Table I 4 T. KOBAYASHI and T. HAMADA [Vol. 57(B),

8b. Late Famennian (?) Waribole perlisensis horizon of Gunong Butan Haj ai, Penis. Waribole elliptica (Mansuy, 1912) is reported from Yiliang, Yunnan. 8c. Early Tournaisian (?) Phillibole kedahensis horizon of Kampong Jeluton, Kedah where it is accompanied by Diacoryphe ( ?) sp. Cyrtosymbole (Macrobole) R. and E. Richter, 1951 in which the above species was primarily located, was synonymized with Archaegonus (Phillibole) R. and E. Richter, 1937 whose range is from upper Devonian (to IV-VI) to Visean (eu III) , but flourished in the Culm f acies (G. and R. Hahn, 1975). 9) Pudoproetus and Linguaphillipsia represented in South Thailand by Proetus cf., coddonensis and Phillipsia aff, silesiaca of Phattalung, both by Reed (1920) . Pudoproetus as a genus is widely distributed in North America, Eastern and Central Asia, the Urals and Australia in the age from Etroeungtian to late Tournaisian with acmeic prominence in the early Tournaisian time. 10) Visean Linguaphillipsia terapaiensis horizon in the Sungei Terapai shale at Kuantan, east Pahang. 11) Upper Carboniferous or upper Moscovian Thaiaspis horizon at Huai Luang, Wang Saphung, L.oei district (1961, 1979). 12) Lower Permian or upper Sakmarian trilobites of the Rat Buni limestone at Tham Nam Maholan, Changwat Loei. This age is determined by f usulinids and brachiopods (Igo,1972 ; Yanagida,1967). Neoproetus as a genus is, however, more flourished in middle and late Permian in Eurasia. Paraphillipsia was known to be an Artinskian genus. Paraphillipsia levigata was recently described by the authors (1980) from the Shimoyama limestone, Sakawa, Shikoku, Japan which is now considered Middle Permian. Beside the above Sakmarian fauna, some pygidia resembling Neoproetus and Ditomopyge occur in the Middle and Upper Permian of Pahang (1979). As listed here, 48 trilobite species of 35 genera in the region are distributed in 18 families including 9 subfamilies in the Proetidae and 4 in the Dalmanitidae as follows : The Trinodidae, Pseudotrinodidae, Dikelocephalidae, Elvinidae, Pagodi- idae, Saukiidae, Remopleuridae, Asaphidae, Nileidae, Cyclopygidae, Cyrtosym- bolidae, Proetidae, Harpidae, Raphiophoridae, Cheiruridae, Calymenidae, Phacopidae and Dalmanitidae. The Proetinae, Leptoproetinae, Cyrtosymbolinae, Eodrevermanniinae, Prionopeltinae, Linguaphillipsinae, Griffithidinae, Ditomopyginae and Thai- aspinae in the Proetidae. The Dalmanitinae, Zeliszkelliinae, Langgoniinae, and Blanodalmanitinae in the Dalmanitidae. One new family and two new subfamilies are the Pseudotrino- didae, Langgoniinae and Blanodalmanitinae. Thirteen new genera are Geratrinodvs, Pseudotrinodus, Thailan,dium, Perakaspis, Lang gonbole, Bailielloides, Malayaproetus, Loeipyge, Thaiaspis, Prodontoehile, No. 1] Trilobites of Thailand and Malaysia 5

Lang gonia, Blanodalmanites and Tambakia and four new subgenera are Perakaspis (Krohbole), Neoproetus (Triproetus), Thaiaspis (Thaia- spella) and Lonchodomas (Metalonchodomas). The new family and subfamilies and many of new genera were instituted for new species of the Prodontochile fauna (6) and the Pseudotrinodus-Plagiolaria fauna (7), particularly the Kroh fauna (7a), the fact suggesting their high endemism. The remaining new genera and subgenera are contained in the three Cambro-Ordovician faunas (1, 3, 4) and another two Permo-Carboniferous faunas (11,12) . Langgonbole is a solitary genus in the 8a horizon. Of the other horizons (2, 5, 7b, c, 8b, c, 9 and 10) each contains only one or two species of trilobites, although there may be associate fossils of other kinds. Among new genera Tambakia is so aberrant that its taxonomic position is indeterminable, although it bears something allied to the Trilobita. Taxonomic comments were already given on a few genera, Pseudotrinodus and Malayaproetus for example (Bergstrom, 1973, 1977; Thomas and Owens, 1979). Beside the mentioned trilobites in the table there are some 30 indeterminable forms resembling scutellid, illaenid, cryptolithid, bulbaspid, odontopleurid, lichid, etc. The trilobites of the region will be enriched twice or more in future. For their more exact classification and also for the final rectification of certain aberrant taxa further explorations and studies are required.

References

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