Mesozoic vertebrates from Thailand 83 The biogeographical significance of the Mesozoic vertebrates from Thailand

Eric Buffetaut1 and Varavudh Suteethorn2 1UMR CNRS 5561, Université de Bourgogne, France# Present address: 16 cour de Liégat, 75013 Paris, France 2Geological Survey Division, Department of Mineral Resources, Rama VI Road, Bangkok 10400, Thailand

Key words: Thailand, Mesozoic, vertebrates, amphibians, reptiles, biogeography

Abstract brates, ranging in age from Late Triassic to late Early Cretaceous (for a recent review of the di- Mesozoic non-marine vertebrate faunas from Thailand nosaurs, see Suteethorn et al#, 1995), This is by (mainly from the Indochina block) range in age from Late Triassic to late Early Cretaceous The oldest known assem- far the best record for that time interval in SE blage, from the Huai Hin Lat Formation, is Norian It in- Asia, and it allows a reconstruction of vertebrate cludes fishes, amphibians and reptiles very similar to those faunal history in that part of the world over a from the Upper Triassic of Central Europe, and indicates period of more than 100 million years, The pur- that dispersal of continental vertebrates across Eurasia was pose of this brief review is to discuss the easy in the Late Triassic A slightly younger (Rhaetian) prosauropod dinosaur is biogeographically less significant, palaeobiogeographical significance of the vari- although it may be related to Chinese forms Jurassic verte- ous Mesozoic vertebrate assemblages hitherto brates are known from both the Indochina block (Phu discovered in Thailand, Kradung Formation) and the Shan-Thai block Resem- blances between the assemblages from both areas suggest that they were already in contact in the Jurassic Similarities with Jurassic vertebrates from China indicate links with General geological setting more northerly parts of Asia The Lower Cretaceous (pre- Aptian) Sao Khua Formation contains a vertebrate fauna It is now generally accepted that Thailand con- which seems to be older than most Cretaceous assemblages sists of two continental blocks or microconti- known from other parts of Asia, and probably corresponds to a phase of relative isolation of Asia It includes dinosaurs nents (Fig,1), the eastern part (with, notably, the which may be close to the ancestry of groups which later Khorat Plateau where most Mesozoic vertebrate played an important part in Asian and North American as- localities are) belonging to the Indochina block, semblages, such as tyrannosaurids and ornithomimids while the western part (including the southern Some of the Sao Khua sauropods may be related to the poorly known Upper Cretaceous sauropods of Mongolia peninsula) is part of a terrane variously called and China The Aptian-Albian Khok Kruat Formation has ‘Shan-Thai’ or ‘Sibumasu’ (see Metcalfe, 1996, yielded a freshwater shark also known from the Lhasa block for a recent review), The Indochina block seems of Tibet, as well as the ceratopsian dinosaur Psittacosaurus, to have sutured to South China in the Carbonif- which was widespread in Asia during the Early Cretaceous erous (Metcalfe, 1996), The timing of the colli- It also contains remains of iguanodontid dinosaurs which are probably immigrants from Europe and show that by the sion of the Shan-Thai block with Indochina and late Early Cretaceous the isolation of Asia had ended South China is still debated (Late Permian to Triassic according to Metcalfe, 1996; as late as Late Jurassic according to Stokes et al#, 1996), Introduction The Mesozoic non-marine vertebrates found in Thailand (Table 1) can thus provide some evi- In the last twenty years, Thailand has yielded a dence concerning the late stages of the accre- number of Mesozoic non-marine fossil verte- tion history of these terranes,

Biogeography and Geological Evolution of SE Asia, pp 83-90 Edited by Robert Hall and Jeremy D Holloway © 1998 Backhuys Publishers, Leiden, The Netherlands 84 E# Buffetaut and V# Suteethorn

Upper Triassic: the vertebrate assemblage from the Huai Hin Lat Formation

The Huai Hin Lat Formation of the Khorat Pla- teau consists mainly of lacustrine bituminous limestones and shales, It is Upper Triassic, prob- ably Norian, on the basis of plant macro-remains (Konno and Asama, 1973), palynomorphs (Haile, 1973; Racey et al#, 1996), conchostracans (Kobayashi, 1975) and vertebrates (review in Buffetaut et al#, 1993), The vertebrate assemblage from the Huai Hin Lat Formation, which consists of both isolated elements and partly articulated skeletons, in- cludes actinopterygian fishes (Martin, 1984), lungfishes (Martin and Ingavat, 1982), amphib- ians (Cyclotosaurus: Ingavat and Janvier, 1981; plagiosauroid indet: Suteethorn et al#, 1988), tur- tles (Proganochelys: Broin et al#, 1982, Broin, 1984), and phytosaurs, including a Belodon-like form and Mystriosuchus (Buffetaut and Ingavat, 1982; Buffetaut et al#, 1993), From a biogeographical point of view, the freshwater vertebrate assemblage from the Huai Hin Lat Formation is remarkable in that it closely resembles the classic vertebrate fauna from the Norian of Germany (Stubensandstein), Genera of fishes, amphibians, turtles and phytosaurs are common to the Stubensandstein and the Huai Hin Lat Formation, This clearly suggests that in the Norian, dispersal of non-marine vertebrates was possible across Eurasia between Central Europe and the Indochina block of SE Asia, In- terestingly, no assemblages closely similar to Fig1 Map of SE Asia showing approximate limits between that from the Huai Hin Lat Formation are cur- the Shan-Thai and Indochina blocks, and the location of rently known from China (where, admittedly, fossiliferous areas or localities mentioned in text (in italics) Upper Triassic vertebrates are very poorly repre- sented; Sun, 1989), Possible dispersal routes across Late Triassic Eurasia are still poorly known, but they must have existed, hitherto found in the Nam Phong Formation consists of the fused distal ends of the ischia of a large prosauropod dinosaur (Buffetaut et al#, Upper Triassic: a prosauropod dinosaur from the 1995), A more accurate identification is not pos- Nam Phong Formation sible on the basis of the available material, As prosauropods had a nearly world-wide distribu- The Nam Phong Formation, which unconform- tion, on both Gondwana and Laurasia, in the ably overlies the Huai Hin Lat Formation, con- Late Triassic and Early Jurassic, the occurrence sists of sandstones and mudstones of mainly flu- of an indeterminate prosauropod on the vial origin, It has yielded very few fossils, and its Indochina block in the Rhaetian is not especially age has long remained uncertain, Racey et al# surprising or significant, Abundant prosauropod (1994, 1996) reported palynomorphs indicating remains, belonging to several taxa, have been an age no younger than Rhaetian and no older found in the Lower Lufeng Beds of Yunnan in than Ladinian, Since the underlying Huai Hin Lat southern China, but, after much controversy Formation is well dated as Norian, a Rhaetian over their age (for a recent review, see Dong, age is likely for the Nam Phong Formation, 1992), the Lower Lufeng Beds are now usually The only recognisable vertebrate element dated as Lower Jurassic (on the basis of paly- Mesozoic vertebrates from Thailand 85

Table 1 Main Mesozoic vertebrate-bearing formations of northeastern Thailand with their possible ages and significant fossils

Khok Kruat Formation Aptian-Albian Thaiodus, Psittacosaurus, Iguanodontidae Phu Phan Formation Barremian? Theropod footprints Sao Khua Formation Valanginian-Hauterivian? Siamotyrannus, Phuwiangosaurus, Ornithomimosauria Phra Wihan Formation Berriasian? Theropod footprints Phu Kradung Formation Late Jurassic Temnospondyls, euhelopodid sauropods Nam Phong Formation Rhaetian Prosauropods Huai Hin Lat Formation Norian Lungfish, Cyclotosaurus, Proganochelys, phytosaurs

nomorphs and molluscs), although their lower the Khorat Plateau, Among them are the first di- part is sometimes referred to the Rhaetian, In nosaur remains from the Jurassic of Thailand, this connection, it is worth mentioning that an which consist of isolated teeth of sauropods and especially large prosauropod from the lower theropods, The theropod teeth do not exhibit part of the Lower Lufeng Beds has been de- any particular features which could point to scribed as Jingshanosaurus xinwaensis by their biogeographical affinities, The sauropod Zhang and Yang (1994), who consider it to be teeth are broad and spoon-shaped, and com- Upper Triassic, Whether the apparently even pletely different from those referred to larger prosauropod from Thailand was more or Phuwiangosaurus, the most frequent sauropod less closely related to Jingshanosaurus is uncer- in the Lower Cretaceous Sao Khua Formation of tain on the basis of the available material, the Khorat Plateau (see below), They are more reminiscent of those of the euhelopodid dino- saurs from the Jurassic of China, such as Jurassic: vertebrates from the Phu Kradung Euhelopus (Wiman, 1929) or Mamenchisaurus Formation of the Khorat Plateau and similar (Russell and Zheng, 1993), Although the evi- formations of the Shan-Thai block dence is admittedly still slight, these teeth sug- gest that the Jurassic sauropods of SE Asia be- The Phu Kradung Formation of the Khorat Pla- longed to the same group as the Chinese ones, teau was once dated as Lower Jurassic, Because Other interesting vertebrate fossils from the all the overlying formations of the Khorat Group Phu Kradung Formation are vertebral elements are now considered as Lower Cretaceous of temnospondyl amphibians (Buffetaut, Tong (Racey et al#, 1994, 1996), rather than Jurassic and Suteethorn#, 1994), Temnospondyls were and Cretaceous as previously supposed, con- long believed to have become extinct at the end straints on the age of the Phu Kradung Forma- of the Triassic, until they were discovered in the tion have changed, Palynological evidence from Jurassic of Asia (China, Mongolia) and Australia, the Phu Kradung Formation is inconclusive, and in the Lower Cretaceous of Australia, Al- Racey et al# (1996) conclude that the Phu though the Thai temnospondyls cannot be iden- Kradung Formation is “probably Late Jurassic or tified with great accuracy on the basis of the Early Cretaceous in age”, but there is no factual available material, their occurrence is probably palynological evidence for that conclusion, On further evidence of faunal links with more the basis of its vertebrate fauna, a Late Jurassic northerly parts of Asia in the Jurassic, since there age seems likely, is no evidence of faunal links between the One of the first vertebrates to be reported Indochina and Shan-Thai blocks and Australia in from the Phu Kradung Formation was the the Mesozoic, The SE Asian temnospondyls crocodilian Sunosuchus thailandicus (Buffetaut could also be considered as relicts of a distribu- and Ingavat, 1980, 1984), which belongs to a tion predating the collision of the SE Asian genus previously known from the Upper blocks with mainland Asia, Jurassic of Gansu, northwestern China, Besides Interestingly, temnospondyl vertebral ele- supporting a Late Jurassic age for the Phu ments have also been found in rocks of roughly Kradung Formation, the occurrence of the same age as the Phu Kradung Formation in Sunosuchus can be considered as evidence for western Thailand, i#e,, in areas which belong to faunal links with North China in the Jurassic, the Shan-Thai block, One was found in north- More recently, other potentially important, al- western Thailand, near Chiang Rai, in rocks very beit fragmentary, vertebrate remains have been similar in lithology to the Phu Kradung Forma- collected from the Phu Kradung Formation on tion, Several others were found at Mab Ching, in 86 E# Buffetaut and V# Suteethorn the southern peninsula, in lacustrine beds which blage hitherto found in Thailand, It contains have been dated as Middle Jurassic on the basis freshwater hybodont sharks, actinopterygian of charophytes (Buffetaut, Raksaskulwong, fishes, turtles, crocodilians, and dinosaurs Suteethorn and Tong, 1994), Although, again, (theropods and sauropods), the available material is too scanty to warrant The only crocodilian taxon so far described detailed comparisons and correlations, the from the Sao Khua Formation is Goniopholis widespread occurrence of temnospondyls in phuwiangensis, based on a lower jaw fragment Jurassic rocks in various parts of Thailand sug- (Buffetaut and Ingavat, 1983), A relatively com- gests that similar faunas were present on the plete skeleton, possibly of the same form, is cur- Indochina block and on the Shan-Thai block in rently under study, and apparently does not be- the Jurassic, which in turn suggests that these long to Goniopholis, An assessment of the real terranes were already in contact, Alternatively, biogeographical significance of the Sao Khua these vertebrae could be considered as unre- crocodilians will be possible only after the new lated fragments of a former vast distribution of skeleton has been fully described, temnospondyls, encompassing both Australia Some of the theropod dinosaurs from the Sao and Asia, More complete material will be Khua Formation have interesting biogeographi- needed before a definite choice can be made cal implications, Siamotyrannus isanensis, de- between these competing hypotheses, but cur- scribed on the basis of a pelvis and part of the rent geodynamic reconstructions seem to favour vertebral column (Buffetaut et al#, 1996), is con- the former, sidered as the oldest and most primitive known The Mab Ching locality has also yielded good tyrannosaurid, The Tyrannosauridae are other- turtle material (Buffetaut, Tong, Suteethorn and wise known from the Upper Cretaceous of Asia Raksaskulwong, 1994; Tong et al#, 1996), The and North America, No well-ascertained Lower Mab Ching turtles may be related to the Cretaceous tyrannosaurids have so far been re- Chengyuchelyidae, a family known from the corded outside Thailand, The occurrence of Jurassic of China (Sichuan and Xinjiang), which Siamotyrannus in the Sao Khua Formation sug- would indicate biogeographical links between gests that the family Tyrannosauridae probably the Shan-Thai block and the Chinese blocks in originated in Asia, and later spread to North the Jurassic, America (via Beringia), possibly at the end of the Early Cretaceous, during a phase of faunal interchange which has already been postulated Lower Cretaceous: vertebrates from the Sao Khua by Russell (1993), Formation The Sao Khua Formation has also yielded re- mains of a still unnamed new ornithomimosaur, Vertebrate fossils from the Phra Wihan Forma- This small ‘ostrich-dinosaur’ exhibits an interest- tion, which overlies the Phu Kradung Formation ing foot structure, with a proximally ‘pinched’ on the Khorat Plateau and is dated as Lower Cre- third metatarsal which is more advanced than taceous (Berriasian to Barremian) on the basis of those of the primitive ornithomimosaurs Harpy- palynomorphs (Racey et al#, 1994, 1996), are re- mimus okladnikovi (from the Aptian-Albian of stricted to dinosaur footprints, which have no Mongolia) and Garudimimus brevipes (from the clear biogeographical implications, Cenomanian-Turonian of Mongolia), in which The Sao Khua Formation, which overlies the the third metatarsal is less compressed proxi- Phra Wihan Formation, consists of red clays, mally, The Thai ornithomimosaur is however sandstones and conglomerates, indicating depo- slightly less advanced than Archaeornitho- sition in a floodplain with meandering rivers, mimus asiaticus (from the Cenomanian of Inner Although it was long considered as Upper Mongolia), in that the proximal end of the third Jurassic, its stratigraphic position above the metatarsal is still visible, as a thin sliver of bone, palynologically dated Phra Wihan Formation between the second and fourth metatarsals, shows that it is at least Lower Cretaceous, Since whereas in the Mongolian form it is hidden by the Aptian-Albian Khok Kruat Formation overlies the anterior contact between the second and the Phu Phan Formation, which itself overlies fourth metatarsals, This new ornithomimosaur the Sao Khua Formation (see below), the Sao suggests both that the group started to diversify Khua Formation must be pre-Aptian and Lower early in the Cretaceous, and that advanced Cretaceous, ornithomimosaurs may have originated in Asia, The Sao Khua Formation has yielded the rich- Their biogeographical history may have been est and most diverse Mesozoic vertebrate assem- similar to that of tyrannosaurids, since their Late Mesozoic vertebrates from Thailand 87

Cretaceous distribution also included Asia and saurids and ornithomimosaurs, with the excep- North America (reports of Upper Cretaceous tion that Asian sauropods apparently did not dis- ornithomimosaurs from other continents are de- perse to North America in the Late Cretaceous, batable), Sauropod dinosaurs are particularly abundant in the Sao Khua Formation, The best known of Upper Lower Cretaceous: vertebrates from the them is Phuwiangosaurus sirindhornae, de- Khok Kruat Formation scribed on the basis of an incomplete skeleton (Martin et al#, 1994), More complete specimens The only vertebrate fossils from the Phu Phan have now been discovered and provide some Formation, which overlies the Sao Khua Forma- additional evidence about this form, tion, are dinosaur footprints which do not pro- Phuwiangosaurus is clearly different from the vide any biogeographical information, The over- Euhelopodidae, a group of sauropods including lying Khok Kruat Formation has, however, such genera as Euhelopus, Mamenchisaurus yielded remains of various vertebrates which and Omeisaurus, which was widespread in can be compared with forms from other parts of China during the Jurassic, Its narrow, lanceolate the world, teeth (Suteethorn et al#, 1995) are unlike the The Khok Kruat Formation consists of red broad, spoon-shaped teeth of the Euhelopodidae clays, sandstones and conglomerates, and its (and unlike the above-mentioned teeth from the depositional environment is supposed to have Phu Kradung Formation), The post-cranial skel- been similar to that of the Sao Khua Formation, eton also shows many differences (Martin et The Khok Kruat Formation is relatively precisely al#,1994), in particular in the shape of the cervi- dated, The freshwater hybodont shark Thaiodus cal vertebrae, which are broad and dorsoven- ruchae is known only from the Khok Kruat For- trally compressed, whereas those of the mation and from the Takena Formation of the Euhelopodidae are narrow and laterally com- Lhasa block of Tibet, which is dated as Aptian- pressed, The neural spines of the posterior cer- Albian on the basis of foraminifera (Cappetta et vical vertebrae of Phuwiangosaurus are deeply al#, 1990), thus suggesting a similar age for the bifurcated, whereas those of the euhelopodids Khok Kruat Formation, This is consistent with only show a shallow bifurcation, There is there- the occurrence of Albian-Cenomanian paly- fore no evidence of close links between this nomorphs in the overlying Maha Sarakham For- Early Cretaceous form and the older Asian mation (Sattayarak et al#, 1991), sauropods, Phuwiangosaurus shows a combi- The vertebrate fauna from the Khok Kruat nation of characters which separate it from most Formation includes hybodont sharks, turtles, previously described families of sauropods, In crocodilians, theropods, ceratopsians and the shape of its teeth, however, it very closely ornithopods, As mentioned above, the resembles Nemegtosaurus mongoliensis, from hybodont shark Thaiodus indicates faunal re- the Upper Cretaceous of the Gobi desert semblances with the Lhasa block of Tibet, which (Nowinski, 1971), which is sometimes placed in is supposed to have collided with mainland Asia a family of its own, the Nemegtosauridae in the Late Jurassic, It is likely that Thaiodus, (Upchurch, 1994), However, Nemegtosaurus is being known both in Tibet and in SE Asia, had a known only by its skull, while Phuwiango- larger distribution in Asia during the late Early saurus is represented mainly by postcranial ele- Cretaceous, ments, so that comparisons are difficult, Further The remains of turtles, crocodilians and evidence concerning the possible affinities of theropods so far found in the Khok Kruat For- Phuwiangosaurus may be afforded by a re- mation are too fragmentary to warrant a biogeo- cently reported sauropod skeleton from the Up- graphical interpretation, Remains of orni- per Cretaceous of Shanxi, China (Pang et al#, thischians are more significant in this respect, all 1995), which is said to have Nemegtosaurus-like the more so that, curiously enough, no teeth, but detailed comparisons will have to ornithischian remains have so far been found await a more complete description of this Chi- among the abundant dinosaur material from the nese form, Although admittedly the position of Sao Khua Formation, Phuwiangosaurus in sauropod evolution is still The first ornithischian dinosaur to have been unclear, it may be close to the origin of at least reported from the Khok Kruat Formation is the some of the Upper Cretaceous sauropods of small ceratopsian Psittacosaurus (Buffetaut et Asia, which would point to a biogeographical al#, 1989), represented by jaws for which the history similar to the above-mentioned tyranno- species P# sattayaraki was erected (Buffetaut 88 E# Buffetaut and V# Suteethorn and Suteethorn, 1992), The genus Psittaco- non-marine bivalve Nippononaia ryosekiana saurus was previously known from a number of (Isaji, 1993), Although there are uncertainties localities in northern Asia (Mongolia, Siberia, concerning the exact age of some of the Lower northwestern and northeastern China, and pos- Cretaceous non-marine formations of Japan, the sibly Japan), The discovery of Psittacosaurus occurrence of marine intercalations makes cor- some 3000 km south of the Chinese localities relations easier than in the Gobi basin or north- has caused some surprise among palaeontolo- eastern Thailand, In addition, iguanodontid gists (Dodson, 1996), because the so-called teeth are known in Japan from a horizon lying Psittacosaurus fauna was generally held to be below a volcanic tuff which has been dated (by characteristic of a northern Asiatic faunal prov- fission-track studies) as 135 ± 7 Ma BP, which ince (Dong, 1993), but it is not surprising from a would indicate a Valanginian/Hauterivian age stratigraphic point of view, since Psittacosaurus (S, E, Evans, pers, comm,, 1997), If the dating of is a common dinosaur in the Lower Cretaceous the Japanese iguanodontids is correct, it would of Asia (Dong, 1992; Jerzyckiewicz and Russell, appear that this group of dinosaurs reached 1991), and the apparently considerable geo- eastern Asia well before the Aptian, in which graphical distance between the Thai and north- case their absence in the ‘Shinkhudukian’ locali- ern Asian localities mainly shows how little is ties of the Gobi basin, which Jerzykiewicz and known about the Lower Cretaceous dinosaurs of Russell (1991) consider as Aptian, and in the Sao southern China (Dong, 1993), It is likely that fur- Khua Formation of Thailand, is surprising, Ac- ther research on the Khok Kruat Formation will cording to Manabe and Hasegawa (1991) the increase the number of Lower Cretaceous verte- Iguanodontidae migrated to East Asia before the brate taxa common to SE Asia and northern Asia, Berriasian, The Thai and Mongolian records sug- This has been confirmed to some extent by gest a later immigration, because iguanodontids the recent discovery in the Khok Kruat Forma- were apparently not present in those regions at tion of iguanodontid remains, The material is the very beginning of the Cretaceous, Obvi- still scanty, consisting of a caudal vertebra and a ously, uncertainties remain about the date of ar- few shed and worn teeth, The latter, however, rival of iguanodontids in various parts of Asia, are quite typical of iguanodontids, The Iguano- In connection with the discussion of the fauna dontidae had a wide geographical distribution from the Khok Kruat Formation, it should be in the Early Cretaceous, both in Laurasia and mentioned that the dinosaur localities of south- Gondwana, However, their history in Asia ern Laos first reported by Hoffet (1936, 1942, seems to be relatively complex, In the Gobi ba- 1944) are probably in an equivalent of the Khok sin, according to Jerzykiewicz and Russell Kruat Formation on the east side of the Mekong, (1991), iguanodontids do not appear until their and are not Upper Cretaceous, contrary to Khukhtekian ‘Age’, which they consider as up- Hoffet’s original interpretation (Buffetaut, 1991), per Aptian to lower Albian, at a time when The ornithopods ascribed by Hoffet (1944) to faunal interchange between ‘Central Asia’ the Upper Cretaceous genus Mandschurosaurus (which probably meant most of central and east- are in fact more primitive (Buffetaut, 1991), and ern Asia) and both North America and Europe probably iguanodontids (Taquet et al#,, 1995) became possible again after a fairly long period and the sauropod, contrary to Hoffet’s opinion, of isolation of Asia (Russell, 1993), The Thai is not a titanosaurid (Buffetaut, 1991; Taquet et record is in general agreement with what has al#, 1995), This poorly known Lao assemblage been observed in the Gobi basin: the Sao Khua seems to suport the faunal history outlined faunal assemblage, which is pre-Aptian, con- above, in which iguanodontids did not reach SE tains no ornithopods, whereas the Aptian-Albian Asia until relatively late in the Early Cretaceous, Khok Kruat assemblage contains iguanodontids, However, the Japanese record suggests a some- what different chronological pattern, There, Conclusion iguanodontids are present in the Tetori Group (Manabe and Hasegawa, 1991), which is The Thai record of non-marine Mesozoic verte- Neocomian, Iguanodontid teeth resembling brates is, at least stratigraphically, one of the those from Thailand have been described best in Asia, covering as it does a long time in- (Hasegawa et al#, 1995) from the upper part of terval extending from the Late Triassic to the the Itoshiro Subgroup, which is overlain by the end of the Early Cretaceous, The main biogeo- Kitadani Formation, considered as upper graphical conclusions to be drawn from that Barremian to lower Aptian on the basis of the record can be summarised as follows: Mesozoic vertebrates from Thailand 89

In the Late Triassic, links between the verte- cheloniologica 1: 87-97 brate fauna of the Indochina Block and the Broin, F de, Ingavat, R , Janvier, P and Sattayarak, N 1982 Triassic turtle remains from northeastern Thailand Jour- western part of Eurasia are clearly apparent, Be- nal of Vertebrate Paleontology 2: 41-46 cause of the dearth of Upper Triassic vertebrate Buffetaut, E 1991 On the age of the Cretaceous dinosaur- faunas from China, dispersal routes across Eura- bearing beds of southern Laos Newsletters on sia are not easily reconstructed, but they must Stratigraphy 24: 59-73 have existed, Buffetaut, E and Ingavat, R 1980 A new crocodilian from the Jurassic of Thailand, Sunosuchus thailandicus n sp Resemblances between the Jurassic assem- (Mesosuchia, Goniopholididae), and the palaeogeogra- blages from the Indochina Block and the Shan- phical history of Southeast Asia in the Mesozoic Geobios Thai Block strongly suggest that these terranes 13: 879-889 were already in contact at that time, The SE Buffetaut, E and Ingavat, R 1982 Phytosaur remains (Rep- Asian assemblage shows some resemblances to tilia, Thecodontia) from the Upper Triassic of northeast- ern Thailand Geobios 15: 7-17 Chinese Jurassic faunas, Buffetaut, E and Ingavat, R 1983 Goniopholis phuwian- The Lower Cretaceous fauna from the Sao gensis nov sp , a new mesosuchian crocodile from the Khua Formation represents a period which is Jurassic of northeastern Thailand Geobios 16: 79-91 otherwise very poorly known in Asia, It seems Buffetaut, E and Ingavat, R 1984 The lower jaw of to correspond to the late stage of a period of Sunosuchus thailandicus, a mesosuchian crocodilian from the Jurassic of Thailand Palaeontology 27: 199-206 isolation of Asia, and includes forms which may Buffetaut, E and Suteethorn, V 1992 A new species of the be ancestral to (or close to the ancestry of) dino- ornithischian dinosaur Psittacosaurus from the Early Cre- saur groups which became prominent in later taceous of Thailand Palaeontology 35: 801-812 Cretaceous assemblages both in Asia and North Buffetaut, E , Raksaskulwong, L , Suteethorn, V and Tong, H 1994 First post-Triassic temnospondyl amphibians America (in particular, tyrannosaurids and from the Shan-Thai block: intercentra from the Jurassic of ornithomimids), The sauropod Phuwiango- peninsular Thailand Geological Magazine 131: 837-839 saurus may be related to some of the poorly Buffetaut, E , Sattayarak, N and Suteethorn, V 1989 A known Late Cretaceous sauropods of Asia (such psittacosaurid dinosaur from the Cretaceous of Thailand as Nemegtosaurus), and its implications for the palaeobiogeographical his- tory of Asia Terra Nova 1: 370-373 The upper Lower Cretaceous (Aptian-Albian) Buffetaut, E , Suteethorn, V , Martin, V , Chaimanee, Y and assemblage from the Khok Kruat Formation is Tong-Buffetaut, H 1993 Biostratigraphy of the Mesozoic characterised by the presence of Psittacosaurus, Khorat Group of northeastern Thailand: the contribution a dinosaur which is widespread in Asia at that of vertebrate palaeontology In Proceedings of the time, and iguanodontids, The latter seem to International Symposium on Biostratigraphy of Mainland Southeast Asia: Facies and Paleontology, pp 51-62 have been absent in older Cretaceous forma- Edited by T Thanasuthipitak Department of Geological tions such as the Sao Khua Formation, and they Sciences, University of Chiang Mai probably indicate dispersal from Europe after Buffetaut, E , Suteethorn, V , Martin, V , Tong, H , Chaimanee, the isolation of Asia ceased some time during Y and Triamwichanon, S 1995 New dinosaur discoveries the Early Cretaceous, in Thailand In Proceedings of the International Confer- ence on Geology, Geotechnology and Mineral Resources of Indochina, pp 157-161 Edited by L Wannakao Department of Geotechnology, Khon Kaen University Acknowledgements Buffetaut, E , Suteethorn, V and Tong, H 1996 The earliest known tyrannosaur from the Lower Cretaceous of Thai- land Nature 381: 689-691 This work was supported by the Department of Buffetaut, E , Tong, H and Suteethorn, V 1994 First post- Mineral Resources, Bangkok, and by the French Triassic labyrinthodont amphibian in South-East Asia: a Ministry of Foreign Affairs (Mission paléonto- temnospondyl intercentrum from the Jurassic of Thai- logique française en Thaïlande), We thank all land Neues Jahrbuch für Geologie und Paläontologie Monatshefte 7: 385-390 the Thai and French participants who took part Buffetaut, E , Tong, H , Suteethorn, V and Raksaskulwong, in our field work in Thailand, as well as all the L 1994 Jurassic vertebrates from the southern peninsula colleagues in various institutions who made of Thailand and their implications A preliminary report specimens in their care available for compari- In Proceedings of the International Symposium on Stratigraphic Correlation of Southeast Asia, pp 253-256 son, Thanks to Anne-Marie Lézine and Sylvain Edited by P Angsuwathana, T Wongwanich, W Duffaud for help in the preparation of the map, Tansathien, S Wongsomak, S and J Tulyatid Depart- ment of Mineral Resources, Bangkok Cappetta, H , Buffetaut, E and Suteethorn, V 1990 A new hybodont shark from the Lower Cretaceous of Thailand References Neues Jahrbuch für Geologie und Paläontologie Monatshefte 11: 659-66 Broin, F de 1984 Proganochelys ruchae n sp , Chélonien Dodson, P 1996 The horned dinosaurs Princeton du Trias supérieur de Thaïlande Studia Palaeo- University Press, Princeton 90 E# Buffetaut and V# Suteethorn

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