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 were mentioned or preliminarily described from two Jurassic localities in Thailand, yet they were not assigned to a given taxon. Thanks to recent fieldwork, 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 SE 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 other freshwater reptiles such as turtles and temnospondyls.

The osteology of Thaiichthys buddhabutrensis, nov. gen., from the Late Jurassic -Early Cretaceous of Thailand is described on the basis of a collection of well-preserved specimens. The mode of preservation of the material allows describing the external anatomy, as well as some elements of the internal anatomy (braincase, elements of the vertebral column). Most of the cranial and postcranial skeleton shows a rather conservative anatomy for 'semionotiformes', but the jaw apparatus displays specializations. Variations observed in the ossification pattern of the skull roof and of the cheek, in the morphology of the median dorsal scales and in fin rays' count indicate that caution should be applied when these characters are used in diagnoses and in phylogenetic analyses. A phylogenetic analysis including a set of gars, of 'semionotiformes', of Macrosemiiformes and of Halecomorphi shows the following features: (1) the monophyly of Holostei; (2) sister-pair relationships between Tlayuamichin ⁄ Semiolepis, Isanichthys ⁄ 'Lepidotes' latifrons and Araripelepidotes ⁄ Pliodetes; (3) the latter pair, together with Thaiichthys and possibly 'Lepidotes' mantelli, are resolved as stem Lepisosteiformes; and (4) the 'semionotiformes' (a group gathering species of Semionotus and Lepidotes) do not form a clade.

A revision of the freshwater shark fauna from the Phu Kradung Formation in NE Thailand allows the recognition of a new species of Acrodus, which represents the youngest occurrence of the genus and confirms its displacement in freshwater environments after the Toarcian. The rest of the shark fauna includes teeth of Hybodus sp., aff. Hybodus sp., hybodontid dermal denticles, Jiaodontus sp., Lonchidion sp. A, Lonchidion sp. B, Heteroptychodus cf. H. kokutensis and dorsal fin spines. The presence of Jaiodontus and of unusual hybodontid dermal denticles suggests a Jurassic age for most of the Phu Kradung Formation, whereas the presence of Heteroptychodus suggests an Early Cretaceous age for the top of the Formation. However, the age of the Phu Kradung Formation is still uncertain, with contradictory signals coming from palynology, detrital zircon thermochronology and vertebrate palaeontology. In any case, it appears that this is the oldest occurrence of the genus Heteroptychodus, and suggests a Thai origin for this genus, which may have replaced Acrodus in the Thai freshwater palaeoecosystems. Together with Acrodus, the presence of Lonchidion sp. A suggests some European affinities for the shark fauna from the Phu Kradung Formation.

A new ginglymodian fish, Isanichthys lertboosi, is described from the Phu Kradung

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.

This first overview of the bony fish record from the Jurassic and Cretaceous continental deposits of Thailand reveals a significant diversity, with 16 taxa in four formations (the Khlong Min, Phu Kradung, Sao Khua and Khok Kruat Fms). Four of these taxa have already been diagnosed and described, and a couple of others are sufficiently well preserved to be diagnosed in the future. The other taxa are represented at present by fragmentary and isolated remains. The highest diversity is observed among ‘semionotids’, which occur in the four formations. Sinamiids are represented by at least three taxa that occur only in the Sao Khua and the Khok Kruat Formations. Pycnodont fishes are known by rare and isolated dentitions and teeth in the Khlong Min and Sao Khua Formations, and lungfishes referred to Ferganoceratodus occur in the Khlong Min and the Phu Kradung Formations. The assemblages provide few palaeogeographical indications at present, except for evidence of relationships with China and Central Asia. However, it is expected than once the phylogenetic relationships of these taxa are resolved, we will be able to reconstruct precise palaeogeographical scenarios.

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A new genus and new species of primitive eucryptodiran turtle, Phunoichelys thirakhupti gen. et sp. nov., is described on the basis of shell remains from the lower part of the Phu Kradung Formation, at Phu Noi locality, Kalasin Province, NE Thailand. It is assigned to Xinjiangchelyidae on the basis of the marginals covering the lateral end of the costals and the anal scutes invading the hypoplastra. The new taxon is further characterized by a low and rounded carapace without a cervical notch; the whole carapace and plastron covered with a clear ornamentation consisting of tiny irregular vermiculated furrows; a complete neural series that reaches the suprapygal; a very wide and short cervical scute; relatively wide vertebral scutes; and a long first thoracic rib that extends along the full width of the first costal. The sutured plastron/carapace connection and the marginals covering the lateral end of the second to seventh costals suggest that the turtles from Phu Noi may be related to some primitive xinjiangchelyids from the Sichuan Basin. The discovery of a xinjiangchelyid turtle in the lower part of the Phu Kradung Formation supports a Late Jurassic age for that part of the formation.