Komsorn Lauprasert

A New Species of the Ginglymodian Fish Isanichthys from the Late Jurassic Phu Kradung Formation, Northeastern Thailand

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 pair of extrascapulars plus a small median one, the presence of few suborbitals (ca. 4 or 6) arranged in one row, and a median dorsal row of scales with spine. Comparisons with other ginglymodian taxa and a cladistic analysis indicates that Isanichthys (Lepidotes) latifrons from the Late Jurassic of England, as well as probably Isanichthys (Lepidotes) luchowensis from the Early or Middle Jurassic of Sichuan, China, form a clade with both Thai species of Isanichthys. The new species provides evidence of the high diversity of ginglymodian fishes in the Phu Kradung Formation and suggests a new hypothesis of phylogenetic relationships among extinct ginglymodians.

Gavialis from the Pleistocene of Thailand and Its Relevance for Drainage Connections from India to Java

Background The 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 Findings We 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/Significance Comparison 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.

Khoratosuchus jintasakuli gen. et sp. nov., an advanced neosuchian crocodyliform from the Early Cretaceous (Aptian-Albian) of NE Thailand

Abstract A new slender-snouted neosuchian crocodyliform, Khoratosuchus jintasakuli gen. et sp. nov., is described from the late Early Cretaceous Khok Kruat Formation of NE Thailand. This discovery represents the youngest and most advanced Mesozoic crocodyliform known in Thailand on the basis of the following cranial features: the secondary choanae are relatively posterior and almost enclosed by the pterygoid; the lateral margin of the maxilla is relatively straight without lateral constrictions; the dorsal surface of the skull lacks ridges and fossae; maxillary teeth are homodontous; the anterior end of the jugal and prefrontal terminate at the same level. The specimen bears resemblances to Chinese and European derived neosuchians and suggests a close relationship between the late Early Cretaceous neosuchians of China, Europe and SE Asia.

Strontium isotopes and the long-term residency of thalattosuchians in the freshwater environment

Abstract. 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 homogeneous 87Sr/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.

Revision of Isanodus paladeji (Elasmobranchii, Hybodontiformes) from the Lower Cretaceous of Thailand

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, Isanodusnongbualamphuensis 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.KurzfassungMikro-Überreste aus der Unterkreide von Phu Phan Thong Ort, Nong Bua Lam Phu Province, Thailand, ergaben zehn Zahnmorphotypen der Süßwasser Hai-Gattung Isanodus, die eine Revision dieser Gattung erlauben. Zwei neue Morphotypen besitzen gemeinsame Merkmale mit vorderen und hinteren Zähnen von Isanodus paladeji und werden als anterolaterale oder posterolaterale Zähne betrachtet. Die Zähne, die früher als anterolaterale oder posterolaterale Zähne von I. paladeji identifiziert wurden, scheinen in der Tat zu einer neuen Art, Isanodus nongbualamphuensis sp. nov., zu gehören. Zwei Morphotypen können nicht zu einer dieser beiden Arten gehören und zeigen die Anwesenheit einer dritten Art. Das Ornamentations-Muster in einigen Zähnen von I. paladeji und I. nongbualamphuensis sp. nov. ist ziemlich ähnlich dem in der Gattung Heteroptychodus beobachteten, was eine eng Verwandtschaft dieser beiden Gattungen andeutet.

New Evidence of Sauropod Dinosaurs from the Early Jurassic Period of 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.

Erratum to: Revision of Isanodus paladeji (Elasmobranchii, Hybodontiformes) from the Lower Cretaceous of Thailand

Kurzfassung Mikrofossilien aus der Unter-Kreide von Phu Phan Thong (Provinz Nong Bua Lam) in Thailand lieferten zehn Zahn-Morphotypen der Süßwasser-Haigattung Isanodus, die eine Revision dieser Gattung erlauben. Zwei neue Morphotypen besitzen gemeinsame Merkmale mit den vorderen und hinteren Zähnen von Isanodus paladeji und werden als anterolaterale oder posterolaterale Zähne betrachtet. Die Zähne, die früher als anterolaterale oder posterolaterale Zähne von I. paladeji identifiziert wurden, scheinen in der Tat zu einer neuen Art, Isanodus nongbualamphuensis sp. nov., zu gehören. Das Ornamentationsmuster einiger Zähne von I. paladeji und I. nongbualamphuensis sp. nov. ist dem der Gattung Heteroptychodus ziemlich ähnlich, was eine enge Verwandtschaft dieser beiden Gattungen andeutet.

A new species of Cuora (Testudines: Geoemydidae) from the Miocene of Thailand and its evolutionary significance

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.