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Giant tortoises have been found from the Plio-Pleistocene sediments of Tha Chang sandpits, Nakhon Ratchasima Province, Thailand. These tortoises are represented by several individuals and are described based on carapace, plastron, limb bones, and isolated plates. Three different morphotypes of epiplastral projection are recognized, pertaining to different sexes or different ontogenetic stages. Based on their large size, thick shell, single supracaudal, well-developed epiplastral projection, gulars covering anterior part of the entoplastron or in contact with the latter, and humeropectoral sulcus posterior to entoplastron, these Thai giant tortoises are assigned to the genus Megalochelys. Thai specimens show strong similarities with large tortoises from India as well as those from Flores and Timor, and are therefore very close morphologically to Melgalochelys atlas. Our study provides new evidence about polymorphism and additional information about distribution of Plio-Pleistocene fossil giant tortoises in South and Southeast Asia.

Two crocodilian anterior cranium parts from Takut Khon Village sand pit, Chaloem Phrakiat District, Nakhon Ratchasima Province, are presently described. Their morphology indicates that the specimens belong to a single species based on the presence of several similar characters such as a hole for the reception of the first dentary tooth at the anterior edge of the premaxillary bone; anterior tip of nasal elongate and projecting into the posterior margin of the external nares; wavy suture line between the posterior part of the nasal with the anterior margin of prefrontal and frontal processes. The cranium morphology is extremely close to Crocodylus siamensis Schneider, 1801 (Siamese crocodile) and conforming the existence of C. siamensis from the Middle Pleistocene in Thailand.

The oldest dinosaur assemblages of Thailand deposit in continental sedimentary rocks of the Nam Phong Formation. Not only Isanosaurus attavipatchi was discovered but at least two more species of basal sauropods were found. A partial skeleton from Phu Hin Tan locality refers to sauropod taxon A. It is different from Isanosaurus and shares some characteristics with basal sauropods in the Early Jurassic. The sauropod taxon B was found in Non Sra Ard locality. Base on postcranial skeleton, sauropod taxon B shares some characteristics of the family Vulcanodontidae. Moreover, several fragments of the sauropods specimen are also found in Pha Khok Wang Yang and Phu Noi localities. All of the evidences above indicate that there are a highly diversity of sauropods in the Nam Phong Formation. At least three sauropod species (including Isanosaurus) were found in the Nam Phong formation. The issue about the age of the Nam Phong has been debated for a long time between the Triassic and Jurassic age. All of sauropodomorphs, in this study, are more likely the Early Jurassic period dinosaurs than the Triassic period dinosaurs. And they have deposited in the upper part of Nam Phong Formation.

International audience; Skull and mandibular elements of a tomistomine crocodilian are described from the late Eocene to early Oligocene lignite seams of Krabi, peninsular Thailand. The Thai tomistomine is a longirostrine form characterized by a rostrum/skull ratio of about 0.6; a mandibular symphysis reaching the level of the eleventh alveolus; a deep participation of the splenial in the symphysis to the level of ninth alveolus; an enlarged fifth maxillary alveolus; long nasals reaching the premaxillae at the level of the fifth maxillary alveolus but not contributing to the external nares; undivided posterior processes of premaxillae; a short prefrontal, excluded by a longer lacrimal from the posteromedial margin of maxillae; vomers visible on the palate. A phylogenetic analysis recovers the Thai specimen among derived tomistomines, on the stem lineage of the extant Tomistoma schlegelii, as a close ally of Maomingosuchus petrolica, a late Eocene tomistomine from southern China. The present recognition of Maomingosuchus sp. in late Eocene Thai deposits expands the distribution of Eocene tomistomines from southern China to the tropics. The origin of Tomistominae in Asia is briefly discussed.; Des éléments crâniens et mandibulaires d’un crocodilien tomistominé sont décrits en provenance de niveaux à lignite de l’Eocène supérieur à Oligocène inférieur de Krabi sur la péninsule Thailandaise. Le tomistominé Thaïlandais est caractérisé par un crâne de type longirostre présentant un ratio rostre/crâne d’environ 0.6 ; une symphyse mandibulaire qui atteint le niveau du onzième alvéole ; une participation profonde du splénial dans la symphyse mandibulaire au niveau du neuvième alvéole ; un cinquième alvéole maxillaire élargi ; les os du nasal qui atteignent les prémaxillaires au niveau du cinquième alvéole maxillaire mais ne participant pas aux narines externes ; des processus postérieurs des prémaxillaires non-divisés ; un préfrontal court, exclu de la marge postéromédiale des maxillaires par un lacrimal plus long ; un vomer visible sur le palais. Une analyse phylogénétique place le spécimen Thaïlandais au sein des tomistominés dérivés, au sein de la lignée de l’actuel Tomistoma schlegelii, et proche de Maomingosuchus petrolica, un taxon de la fin de l’Eocène connu en Chine du sud. La présente découverte de Maomingosuchus sp. dans l’Eocène tardif de Thaïlande étend l’aire de répartition des tomistominés eocènes depuis la Chine du sud jusqu’aux tropiques. L’origine des Tomistominae en Asie est brièvement discutée.

International audience; The core of the fossil record of Teleosauridae, a family of thalattosuchian crocodylomorphs, is well known from western Tethyan marine deposits of the Jurassic. Outside this province, their fossil record is patchy and in need of revision, with specimens from Russia, Madagascar, and Asia. Peipehsuchus teleorhinus is known from the Early or Middle Jurassic of China and teleosaurid specimens have been mentioned or preliminarily described from two Jurassic localities in Thailand, yet they were not assigned to a given taxon. Thanks to recent field work, at least 10 individuals represented by cranial material were excavated and prepared from a single Jurassic locality known as Phu Noi in the lower Phu Kradung Formation of northeastern Thailand. Here, we describe these specimens, together with disarticulated postcranial elements, and erect a new taxon, Indosinosuchus potamosiamensis, gen. et sp. nov. Phylogenetic analyses confirm the teleosaurid affinities of the new species, which does not form an exclusive clade with the Chinese teleosaurid Peipehsuchus teleorhinus. The presence of teleosaurids at Phu Noi and a preliminary account of its faunal content favor a Middle to Late Jurassic age for the fossil-bearing horizon. In contrast, Cretaceous deposits in Thailand are characterized by goniopholidids and pholidosaurids, indicating a faunal turnover in Southeast Asia across the Jurassic–Cretaceous. As previously shown by isotope data, the new teleosaurid species was a resident of the freshwater environment and co-occurs with remains of exclusively terrestrial taxa such as sauropod, ornithopod, and theropod dinosaurs and freshwater tetrapods such as turtles and temnospondyls.

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Thalattosuchians are crocodylomorphs mainly known from marine strata of Early Jurassic to Early Cretaceous age. They represent the earliest crocodylomorph radiation to an aquatic habitat and their evolutionary history offers very few records from freshwater settings. Here, we report several exquisitely preserved thalattosuchian skulls attributed to a derived teleosaurid from a pedogenic horizon located at the base of a fluvial series of alternating silts and sandstones of the Phu Kradung Formation (Upper Jurassic) of northeastern Thailand. Using laser ablation multicollector inductively coupled mass spectrometry (MC-ICP-MS) on tooth enamel and dentine, we measured isotopic ratios of strontium (87Sr/86Sr) to test the habitat of these teleosaurids. In addition, Sr concentrations of the dental tissues were estimated from the calibrated signal intensities of the Sr isotope measurements. The dataset includes bioapatite (teeth or scales) of eight terrestrial and five aquatic vertebrates. Theropods exhibit lower Sr concentrations both in enamel and dentine compared to others groups, a pattern in accordance with the calcium biopurification process, which predicts that Sr concentrations in the body of vertebrates decrease up the trophic chain. It also excludes the possibility that diagenesis has completely overprinted the Sr isotope compositions of the fossil assemblage, which exhibits a homogeneous87Sr/86Sr signature above the Late Jurassic seawater value. Values for teleosaurid teeth are in the range of other values for vertebrates in the continental assemblage and imply that these crocodylomorphs did not migrate between freshwater and marine habitats at least in the time constraint of the mineralizing tooth. This result represents the first demonstration that a population of teleosaurids was established for a prolonged time in a freshwater environment. Whether the ability of teleosaurids to inhabit freshwater habitats is a secondary adaptation or whether it is plesiomorphic and inherited from freshwater ancestors is discussed.

Microremains from the Lower Cretaceous Phu Phan Thong locality, Nong Bua Lam Phu Province, northeastern Thailand, yielded ten tooth morphotypes of the freshwater shark genus Isanodus, which allow the revision of this genus. Two new morphotypes assigned to anterolateral and posterolateral teeth possess shared characters with anterior and posterior teeth of Isanodus paladeji whereas its former anterolateral and posterolateral teeth appear to belong to a new species, Isanodus nongbualamphuensis sp. nov. The pattern of ornamentation in some teeth of I. paladeji and I. nongbualamphuensis is quite similar to that observed in the genus Heteroptychodus, suggesting these two genera are closely related.

In the last ten years, several fossil localities in Nakhon Ratchasima Province (northeastern Thailand) have yielded late Neogene turtle and crocodile taxa. Although not always well dated, the age of all these fossils is constrained between Middle Miocene and Pleistocene. Several crocodile taxa have been discovered: Crocodylidae, Alligatoridae and Gavialidae. In particular, the presence of Gavialis is attested in northeastern Thailand during the Pleistocene. Fossil turtles belong to several families: Geoemydidae, Testudinidae, and Trionychidae. In addition to the discovery of giant continental tortoises, some large aquatic trionychid and geoemydid turtles are present. The latter are only found in larger river systems and no longer encountered in the Mun or Chi Rivers of northeastern Thailand. Most fossil forms correspond to modern species and reveal interesting changes in biogeographical distribution patterns. These changes are likely related to changes in the size of the drainage and direction of the Mun River system. We suggest that the Mun River was probably not flowing from west to east to the Mekong River system as today but that it was flowing from east to west to the Chao Phraya River system.

The Mesozoic vertebrate fauna from Kut Island includes hybodont sharks (Hybodus sp., Isanodus paladeji, a new species of Heteroptychodus), actinopterygians (Semionotiformes indet., Lepidotes sp.), indeterminate turtles, goniopholidid crocodiles, cf. Theriosuchus sp. and theropod dinosaurs. The new hybodont species is also present in the Sao Khua Formation and maybe also in the Phu Kradung Formation on the Khorat Plateau in northeastern Thailand. The occurrence of both I. paladeji and the new hybodont, together with heavily ornamented Semionotiformes teeth strongly suggest that this fauna is of the same age as the Sao Khua Formation one. Deposits from Kut Island are therefore younger than usually considered, and not older than Berriasian.

We describe a partial crocodilian skull from the Mesozoic non-marine sediments of the Khorat Plateau Sao Khua Formation (Berriasian-Barremian) in northeastern Thailand and assign it to Theriosuchus grandinaris sp. nov. An isolated dentary from the Phu Kradung Formation (latest Jurassic–Early Cretaceous) is also tentatively assigned to the genus Theriosuchus, and an isolated tooth from the Khok Kruat Formation (Aptian-Albian) may belong to this genus. The Thai fossils represent the first unambiguous evidence of presence of Theriosuchus outside Europe. Its occurrence in Thailand increases the known diversity of neosuchian crocodyliforms from Southeast Asia and suggests that Atoposauridae had a wide geographical distribution from the Late Jurassic to the Early Cretaceous.

Despite the report of fragmentary remains from China, the fossil record of primitive Alligatorinae is unbalanced with most of its members reported from North America and Europe. Here, we describe cranial, mandibular, and some postcranial elements of a new alligatorine taxon from the Late Eocene of Krabi Basin, southern Thailand. Krabisuchus siamogallicus gen. et sp. nov. was a small animal probably not surpassing 2 m in total length. Despite deformation, the remains show a dorsally elevated cranium similar to Arambourgia gaudryi and Osteolaemus tetraspis. The new alligatorine is characterized by a very short snout and a blunt dentition in the posterior region. Krabisuchus siamogallicusis the first fossil alligatorine from Asia to be incorporated into cladistic analysis. Results indicate a close relationship of the newtaxon to Procaimanoidea, Arambourgia gaudryi, and Allognathosuchus polyodon, all of them being sister groups to the Alligator clade. Alligatorine were widespread as early as the Late Eocene across the northern hemisphere. Scenarios of alligatorine dispersal during the Palaeogene are discussed in comparison with the European and North American alligatorine fossil record. Basal alligatorines were probably land-dwelling animals contrary to modern-day crocodylians. Such a mode of life may have allowed this group to colonize vast territories, especially during periods of global warm climates. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010, 158, 608–628.

A new taxon of a broad-snouted goniopholidid, Siamosuchus phuphokensis, gen. et sp. nov., was discovered in the Sao Khua Formation (ante-Aptian), northeastern Thailand. The specimen is described on the basis of an incomplete skeleton showing the premaxillae, maxillae, nasals, left lacrimal, frontal, left jugal, right postorbital, caudal part of the cranial table, most of the right part of the postcranial skeleton, and several heavily sculptured osteoderms. S. phuphokensis is distinguished from the other broad-snouted goniopholidids on the basis of the following characters: penetration of the nasals in the narial border; presence of a robust and high median ridge on the interorbital surface; lateral margin of the frontal forming the medial edge of the orbit; supraoccipital exhibiting a wide pentagonal shape. A phylogenetic analysis using 101 characters for 29 mesoeucrocodylian taxa and 3 outgroup taxa supports the monophyly of the family Goniopholididae. In addition, the Thai specimen forms a clade with the European Goniopholis. Based on our strict consensus tree, the generic name Goniopholis should be restricted to the European forms only.

In the early 1980s, the remains of a large crocodil- ian, consisting of a nearly complete lower jaw, were referred to a distinct species of Sunosuchus, S. thailandicus. The specimen was recovered from a road-cut near Nong Bua Lamphu, north-eastern Thailand, in the upper part of the continental Phu Kradung Formation, and then considered Early to Middle Jurassic in age. Since then, this age has been revised and most of the formation is now considered Early Cretaceous, although a Late Jurassic age is possible for its lowermost part. Here, we report for the first time cranial elements associated with man- dibular remains assignable to 'S'. thailandicus. An attribution to Pholidosauridae is proposed on the basis of premaxillary morphology, and the original referral of this taxon to the go- niopholidid Sunosuchus is discarded. A new genus name Chal- awan now designates the originally described material of S. thailandicus. Nevertheless, the newly described specimen shares a characteristic with both 'traditional' Goniopholididae and Pholidosauridae: the presence of a depression located on the lateral wall of the maxilla and jugal. A phylogenetic analy- sis confirms the inclusion of both Goniopholididae and Pho- lidosauridae into a common clade, Coelognathosuchia tax. nov. Although the new Thai skull is much fragmented, its original shape is reconstructed and is compared with other pholidosaurid genera, namely Elosuchus, Meridiosaurus, Oce- anosuchus, Pholidosaurus, Sarcosuchus and Terminonaris. The presence of the genus Sunosuchus being highly questionable in Thailand, it cannot be used as evidence to link the Chinese and Indochinese blocks. Instead, the recognition of a fresh- water pholidosaurid in a continental formation of the Indo- chinese block suggests that early in their evolutionary history, these crocodilians, already known from Europe, Africa and South America, were more widely distributed along the north- ern margin of the Tethys than previously recognized.

A new species of Cuora, Cuora chiangmuanensis sp. nov., is described on the basis of a nearly complete shell with limb bones from the late Middle – early Late Miocene Chiang Muan Mine, Phayao Province (Northern Thailand). C. chiangmuanensis is distinguished from other fossil and living Cuora species mainly on the basis of its plastral morphology. Among fossil and extant Cuora taxa, the new species appears to be a missing link between the taxa from Southeast Asia and those from East Asia. It represents the earliest record of the genus and demonstrates that by 11–12 Ma, Asian box turtles were already present in Southeast Asia.

BackgroundThe genus Gavialis comprises a single living but endangered species, G. gangeticus, as well as fossil species recorded in the Miocene to Pleistocene deposits of the Indian subcontinent. The genus is also represented in the Pleistocene deposits of Java by the species G. bengawanicus, which was recently recognized to be valid. Surprisingly, no detailed report of the genus exists between these two provinces and the recent evolutionary history of Gavialis is not understood.Methodology/principal findingsWe report new material consisting of skull and mandibular remains of Gavialis from the Early Pleistocene of Khok Sung, Nakhon Ratchasima Province, northeastern Thailand. The Gavialis material described herein is attributed to Gavialis cf. bengawanicus and sheds new light on the occurrence of the genus in mainland SE Asia.Conclusions/significanceComparison of this new material with other species referred to the genus Gavialis led us to preliminary restrict the content of the genus to three species, namely G. gangeticus Gmelin, G. bengawanicus Dubois and G. lewisi Lull. The occurrence of G. cf. bengawanicus in Thailand allows us to propose a scenario for the dispersal of Gavialis from Indo-Pakistan to Indonesia, thus bridging a geographical gap between these two provinces. Dispersal by sea appears a less likely possibility than dispersal through fluvial drainages.

A new ginglymodian fish, Isanichthys lertboosi, is described from the Phu Kradung Formation, north-eastern Thailand, a freshwater deposit of probable Late Jurassic age. The species is represented by four specimens, from the Phu Noi locality, associated with a rich fauna of sharks, turtles, crocodiles, and theropod and sauropod dinosaurs. One specimen is an isolated braincase, which provides characters rarely observed in extinct ginglymodians. The species is referred to the genus Isanichthys, a taxon originally described on the basis of a single specimen from the Phu Nam Jun locality, a slightly younger site approximately 75 km from Phu Noi. Isanichthys is mainly distinguished by frontals slightly narrower anteriorly than posteriorly, two anterior infraorbitals not in contact with the orbit, reduced preorbital region, and a small orbit and a cheek region completely covered by bones. The new species is characterized, among other characters, by a dermal component of the sphenotic visible on the cheek, one pa...