Komsorn Lauprasert

Mamenchisauridae is a group of long-necked non-neosauropodan eusauropod dinosaurs that were abundant in East Asia during the Middle to Late Jurassic, but their diversity and geographic distribution outside China remain poorly documented. Here we describe Uragasaurus kalasinensis gen. et sp. nov., a new sauropod dinosaur from the Phu Kradung Formation of northeastern Thailand. The new taxon is based on a well-preserved anterior dorsal vertebra exhibiting a distinctive combination of characters, including a unique Y-shaped configuration formed by the intraprezygapophyseal and single intraprezygapophyseal laminae and a camellate internal pneumatic structure within the centrum revealed by computed tomography (CT). Phylogenetic analyses recover the new taxon as an early-diverging member of Mamenchisauridae. This discovery represents the first formally named mamenchisaurid from Thailand and expands the known geographic distribution of the clade in Southeast Asia. The occurrence of this taxon in the Lower part of the Phu Kradung Formation also contributes to understanding faunal succession within the unit, supports an Upper Jurassic age for the lower part of the formation, and improves understanding of sauropod diversity in Southeast Asia during the Jurassic-Cretaceous transition.

We describe teleosaurid remains from the Middle to Upper Jurassic Khlong Min Formation at Ban Nam Pun in southern Thailand and define Indosinosuchus peninsularensis sp. nov. This new species is diagnosed by a unique combination of cranial and postcranial features, including the nasal reaching anteriorly at the level of the 18th maxillary alveolus, absence of an incisive foramen, oval-shaped external nares, and broad ornamented osteoderms. Phylogenetic analysis positions I. peninsularensis within a polytomy alongside Mystriosaurus laurillardi and other Asian teleosaurids, supporting a monophyletic Teleosauroidea. In addition, the revision of Indosinosuchus kalasinensis as a junior synonym of I. potamosiamensis also strengthens the taxonomic framework of the genus Indosinosuchus . Indosinosuchus peninsularensis sp. nov., discovered in a low-energy lagoonal environment, offers significant insights on the ecological preferences of teleosaurids. In contrast to the fluvially deposited Phu Kradung Formation of northeastern Thailand, the lagoonal and marginal marine sediments of the Khlong Min Formation are considered indicative of a broad spectrum of habitat occupation by Asian teleosauroids. Based on these observations, a high degree of ecological plasticity has been inferred for Thai teleosaurids, and their extensive dispersal across both the Sibumasu and Indochina terranes during the Middle to Late Jurassic has been further substantiated. The recognition of I. peninsularensis sp. nov. contributes to our understanding of teleosaurid diversity and paleobiogeography in Southeast Asia.

In Thailand, the median-striped bullfrog, Kaloula mediolineata is a commercially important amphibian because it is a natural food source that is easily accessible in rural areas. However, there is currently a dearth of knowledge, especially on the population diversity of this species. This study, therefore, aims to evaluate the genetic variation of K. mediolineata in Thailand using the partial cytochrome b (Cyt-b) and 16S ribosomal RNA (16S rRNA) sequences. A total of 118 samples from 20 localities (Provinces) were collected. K. mediolineata has been classified into 52 and 31 haplotypes of Cyt-b haplotypes (Km1–Km52) and 16S rRNA haplotypes (Kr1–Kr31), respectively, which reflect high levels of genetic variation in this species. The 16S rRNA tree demonstrated a monophyletic group in our examined samples. Based on the Cyt-b sequence, the haplotype network and phylogenetic tree analyses showed that there are two separate genetic groups, which are named G1 and G2. These two divergent groups showed genetic differences with p-distance and F_ST values of 0.028 and 0.608 (p-value < 0.001), respectively. Genetic group G1 is strictly found in certain localities in the north, central, and east regions, whereas G2 is most widespread in this study. Two specimens showed high genetic differences from the others, which indicated that other cryptic genetic groups may exist. Thus, a comprehensive investigation of the biology, ecology, as well as genetic variation of K. mediolineata could be further conducted.

The origin of modern crocodylians is rooted in the Cretaceous, but their evolutionary history is obscure because the relationships of outgroups and transitional forms are poorly resolved. Here, we describe a new form, Varanosuchus sakonnakhonensis gen. nov., sp. nov., from the Early Cretaceous of Thailand that fills an evolutionary gap between Paralligatoridae and Atoposauridae, two derived neosuchian lineages with previously unsettled phylogenetic relationships. Three individuals, including a complete skull and associated postcranial remains, allow for a detailed description and phylogenetic analysis. The new taxon is distinguished from all other crocodylomorphs by an association of features, including a narrow altirostral morphology, a dorsal part of the postorbital with an anterolaterally facing edge, a depression on the posterolateral surface of the maxilla, and fully pterygoid-bound choanae. A phylogenetic analysis confirms the monophyly and taxonomic content of Atoposauridae and Paralligatoridae, and we underline the difficulty in reaching a robust definition of Eusuchia. Furthermore, we put forward further arguments related to the putative terrestrial ecology with semi-aquatic affinities of atoposaurids based on their altirostral snout morphology and osteoderm ornamentation.

Burrowing is one of the important seasonal behaviors in amphibians that could be related to physiological ecology and environmental factors. Burrowing characteristics and temporal variability in burrowing behaviors were explored and examined from three sampling surveys in northeastern Thailand in 2017–2018. Four species of burrowing frogs were identified with overwhelmingly abundant specimens in two species, Glyphoglossus molossus and Kaloula mediolineata. In general, K. mediolineata burrowed deeper than G. molossus although their body size were not different. There were no clear relationships between burrowing depth and frog body size in each species, although G. molossus showed larger SVL in dry seasons than that in rainy seasons. In contrast to K. mediolineata which preferred to burrow deeper in dry seasons, burrowing depth of G. molossus was almost stable among seasons. The results of this study highlighted an interaction between season and species in the burrowing depth of these two frog species in northeastern Thailand.

The Khok Pha Suam locality in the province of Ubon Ratchathani, northeastern, Thailand, is known as “the last home of Thai dinosaurs”, because it belongs to the Lower Cretaceous Khok Kruat Formation (Aptian-Albian) which is currently the youngest Mesozoic vertebrate fossil producing formation in the Khorat Group. Here, we describe a diverse vertebrate assemblage, including hybodonts, ray-finned fishes, turtles, crocodyliforms, pterosaurs, and dinosaurs from the Khok Pha Suam locality. The updated data on the Khok Kruat fauna provides a better understanding of the variety and distribution of Early Cretaceous continental ecosystems, which are useful for palaeoenvironmental reconstruction. In addition to consolidating unincorporated data on fauna, this study also provides the palaeontological data necessary to illustrate the palaeoecosystem to the general public, as well as improving the academic value of the Pha Chan-Sam Phan Bok Geopark.

The non-marine Mesozoic sedimentary rocks of Thailand, which consist of the Indochina block and the Sibumasu block, have yielded several terrestrial and aquatic vertebrate fossils, but only few amphibian remains have been reported. Here, we present an overview on the Thai amphibian palaeo-diversity based on the literature, re-examination of published material, new findings, and unpublished material. Thai amphibian fossil remains are assigned to Stereospondyli (Cyclotosauridae, Plagiosauridae, and Brachyopoidea) and Anura and were discovered from four formations, ranging from the Upper Triassic to Lower Cretaceous of Thailand. The occurrence of Brachyopidae in Thailand, which are related to Chinese forms, supports the previous hypothesis of physical connections between the Indochina blocks and the Sibumasu block during the Mesozoic era.

Glyphoglossus molossus, is one of the most economically important amphibians in the Khorat Plateau, north-eastern Thailand. It is categorised as a near-threatened species by IUCN due to over-exploitation. Here, we examined the genetic structure of G. molossus using partial mitochondrial cytochrome-b gene sequences from specimens collected at 11 localities. The sequence analysis revealed the presence of 15 haplotypes, 5 of which are shared by 2 or more populations, and 10 haplotypes that are confined to a single population. The relatively low haplotype (h) and nucleotide (π) diversities suggest that the Phu Phan Mountain Range is not high enough to act as an effective dispersal barrier between the Sakon Nakhon and Khorat Basins. However, AMOVA and phylogenetic analyses based on Maximum likelihood (ML) and Bayesian inference (BI) strongly supported the presence of two genetically divergent clades, Sakon Nakhon Basin and the northern part of the Khorat Basin (clade A) and the southern part of the Khorat Basin (clade B). These two lineages are separated by substantial geographical distance, which has putatively resulted in a reduction of gene flow. Further studies, with more extensive genetic sampling, especially from throughout the species range will aid in better interpreting our results.