[Paleontology • 2026] Indosinosuchus peninsularensis • A new teleosaurid (Crocodylomorpha: Thalattosuchia) from the Sibumasu Terrane of Southeast Asia and A Taxonomic Reassessment of Indosinosuchus

 

Indosinosuchus peninsularensis 

Lauprasert, Nilpanapan, Martin, Claude, Kamonlak Wongko, Kantanat Trakunweerayut, Dobutr, Manitkoon, Bhuttarach & Nonsrirach, 2026

DOI: doi.org/10.7717/peerj.20944  

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Abstract 

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.

Keywords: Indosinosuchus, Khlong Min Formation, Sibumasu, Phu Kradung Formation, Indochina

Indosinosuchus peninsularensis sp. nov. from the Khong Min Formation, Ban Nam Pun, southern Thailand. Photographs and interpretive drawings of Indosinosuchus peninsularensis sp. nov. from the Khong Min Formation, Ban Nam Pun, Nakhon Si Thammarat Province, southern Thailand.
PRC-205: anterior rostrum in dorsal view (A, B) and dorsal vertebrae in ventral view (C, D). PRC-206: osteoderms and dorsal vertebrae in dorsal view (E, F) and ventral view (G, H).

Abbreviations: dv, dorsal vertebrae; en, external nares; mx, maxilla; n, nasal; ost, osteoderm; pmx, premaxilla.

CROCODYLOMORPHA Hay, 1930

THALATTOSUCHIA Fraas, 1901

NEOTHALATTOSUCHIA Young et al., 2024a; Young et al., 2024b

TELEOSAUROIDEA Delfino & Dal Sasso, 2006

TELEOSAURIDAE Geoffroy Saint-Hilaire, 1831

Genus Indosinosuchus Martin et al., 2019

Indosinosuchus peninsularensis 

Holotype: PRC 205 and PRC 206, comprising an anterior portion of the rostrum, osteoderms, and dorsal vertebrae.

Type locality: Ban Nam Pun, Bang Khan District, Nakhon Si Thammarat Province, southern Thailand.

Stratigraphic occurrence: Lower part of the Khlong Min Formation, Thung Yai Group, late Middle Jurassic to early Late Jurassic.

Diagnosis. Indosinosuchus peninsularensis, PRC 205, is characterized by the following combination of characters (autapomorphies denoted with*): (1) four premaxillary alveoli; (2) moderately laterally expanded premaxilla with subequal length and width, producing a broad yet unflared outline; (3) margin of premaxillary-maxillary suture is concave between the 4th premaxillary –1st maxillary alveoli; (4) the external narial opening is subcircular or slightly ‘8-shaped’ in dorsal view; (5) absence of incisive foramen at medial contact of premaxillae*; (6) anterior tip of nasals reaching the level of the 18th maxillary alveolus*.

Locality, lithostratigraphy, and petrographic characteristics of the fossiliferous limestone within the Khlong Min Formation at Ban Nam Pun, southern Thailand.
(A) Tectonic subdivision map of Thailand (modified after Udchachon et al., 2022), illustrating the distribution of Jurassic sedimentary rock units (based on Meesook & Saengsrichan, 2011). The Khlong Min Formation, including the Ban Nam Pun locality, is situated within the Sibumasu Terrane, whereas the Phu Kradung Formation and its equivalents are located within the Indochina and Sukhothai Terranes. (B) Simplified geological map of the Krabi–Khlong Thom–Trang region (adapted from Thailand Department of Mineral Resources, 1999; Meesook & Saengsrichan, 2011), with the study site marked by a red star.
(C) Field photograph of the fossiliferous limestone outcrop intercalated with mudstone. The rock hammer (circled) is 30 cm in length for scale. (D–F) Close-up view of fossiliferous limestone rich in bivalves, (D) Modiolus sp. assemblage, (E) Actinostreon sp. (F) Protocardia sp. (G) MF1: Bioclast wackestone characterized by shell fragments, benthic foraminifera (f), and peloids (p). The yellow arrow indicates a bivalve shell with geopetal fabric: the lower portion infilled with micritic matrix and peloids, and the upper portion filled with sparry calcite cement. (H) MF2: Bioclast-peloidal packstone to grainstone, dominated by peloids (p) and benthic foraminifers (f) with minor ostracod shells (o).

 Komsorn Lauprasert, Apirut Nilpanapan, Jeremy E. Martin, Julien Claude, Kamonlak Wongko, Kantanat Trakunweerayut, Nuntida Dobutr, Sita Manitkoon, Supanut Bhuttarach and Thanit Nonsrirach. 2026. A new teleosaurid (Crocodylomorpha, Thalattosuchia) from the Sibumasu Terrane of Southeast Asia and A Taxonomic Reassessment of Indosinosuchus. PeerJ. 14:e20944. DOI: doi.org/10.7717/peerj.20944 [2026-03-20]

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[Paleontology • 2024] Varanosuchus sakonnakhonensis • New Cretaceous neosuchians (Crocodylomorpha) from Thailand bridge the evolutionary history of atoposaurids and paralligatorids

Varanosuchus sakonnakhonensis 

Pochat-Cottilloux, Lauprasert, Chanthasit, Manitkoon, Adrien, Lachambre, Amiot & Martin, 2024

วาราโนซูคัส สกลนครเอนซิส  || DOI: 10.1093/zoolinnean/zlad195

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Abstract

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.

Atoposauridae, CT scan, Neosuchia, Phu Sung, Sao Khua, Thailand

Varanosuchus sakonnakhonensis gen. nov., sp. nov.

 

Yohan Pochat-Cottilloux, Komsorn Lauprasert, Phornphen Chanthasit, Sita Manitkoon, Jérôme Adrien, Joël Lachambre, Romain Amiot and Jeremy E Martin. 2024. New Cretaceous neosuchians (Crocodylomorpha) from Thailand bridge the evolutionary history of atoposaurids and paralligatorids. Zoological Journal of the Linnean Society. zlad195. DOI: 10.1093/zoolinnean/zlad195

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วาราโนซูคัส สกลนครเอนซิส  🐊🐊

จระเข้ทรงเหี้ย จระเข้ดึกดำบรรพ์ชนิดใหม่ชนิดที่ 12 ของประเทศไทย  

 จากหมวดหินเสาขัว ต้นยุคครีเทเชียส จ.สกลนคร 

[Paleontology • 2014] ชาละวัน ไทยแลนดิคัส • Chalawan thailandicus • A Large pholidosaurid in the Phu Kradung Formation of north-eastern Thailand; former 'Sunosuchus' thailandicus

Chalawan thailandicus (Buffetaut & Ingavat 1984)
Chalawan gen. nov. Martin, Lauprasert, Buffetaut, Liard & Suteethorn 2013
syn: Sunosuchus thailandicus Buffetaut & Ingavat 1984

illustration: satorsaurus.deviantART.com

ชาละวัน ไทยแลนดิคัส Chalawan thailandicus

ซูโนซูคัส ไทยแลนดิคัส Sunosuchus thailandicus

Abstract

In the early 1980s, the remains of a large crocodilian, 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 mandibular 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 goniopholidid Sunosuchus is discarded. A new genus name Chalawan 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 analysis confirms the inclusion of both Goniopholididae and Pholidosauridae 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, Oceanosuchus, 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 freshwater pholidosaurid in a continental formation of the Indochinese block suggests that early in their evolutionary history, these crocodilians, already known from Europe, Africa and South America, were more widely distributed along the northern margin of the Tethys than previously recognized.

Keywords: crocodilia; Coelognathosuchia; Pholidosauridae; Mesozoic; Phu Kradung Formation; Thailand

SYSTEMATIC PALAEONTOLOGY

This published work and the nomenclatural act it contains have been registered in Zoobank: http://zoobank.org/References/EC1507EB-0C95-48A0-B675-56141C9393FC

Order CROCODILIA Gmelin, 1789

Suborder COELOGNATHOSUCHIA tax. nov.

Derivation of name. In reference to the depression or concavitylocated on the posterodorsal surface of the maxilla, close or par-ticipating to the jugal. The name translates from the Greek jοιkος (concave), cmάhος (jaw) andrο~tvος (crocodile).

Diagnosis. Coelognathosuchia is characterized by the fol-lowing combination of features: presence of a depressionon the posterodorsal region of the rostrum (autapomorphic), located either fully on the maxilla or on both themaxilla and jugal; subcircular supratemporal fenestrae larger than orbits; maximum frontal width as wide or widerthan the diameter of one orbit; anterior process of nasal excluded from posterior margin of external nares; in dorsalview, marked notch at the premaxillary–maxillary junction;reduced or absent antorbital fenestra; more or less developed spine at anterolateral corner of postorbital; exoccipitaland quadrate not in contact posterior to otic area; pendu-lous quadrate medial hemicondyle; posteroventrally pro-jected retroarticular process; insertion for m. pterygoideusposterior restricted to medial margin of angular.

Definition. The sister group to the most derived neosuchians (Bernissartia fagesiiand Eusuchia), incorporatingthe family Pholidosauridae and all taxa more closelyrelated to it than to Bernissartia fagesiiand Eusuchia. Under the present phylogenetic hypothesis, the family Goniopholididae is paraphyletic.

Family PHOLIDOSAURIDAE Zittel and Eastman, 1902 

Derivation of name: ชาละวัน, Chalawan, a gigantic crocodile in the epic story of the crocodile hunter Khrai Thong written by King Rama II (1768–1824).

Type species: Sunosuchus thailandicus Buffetaut and Ingavat, 1980; CAS42-20 in Sirindhorn Museum, Kalasin province (formerly TF1370 in DMR, Bangkok); a nearly complete mandible lacking only a part of the right ramus from the Phu Kradung Formation near Nong Bua Lamphu, north-eastern Thailand.

Referred specimen: PRC102-143, Skull and mandibular elements of a single individual comprising parts of the rostrum, braincase and skull table as well as various parts of the mandible from Kham Phok, Mukdahan Province.

Type locality: Nong Bua Lam Phu, Nong Bua Lam Phu Province.

Type stratum: Phu Kradung Formation.

Jeremy E. Martin, Komsorn Lauprasert, Eric Buffetaut, Romain Liard and Varavudh Suteethorn. 2013. A Large pholidosaurid in the Phu Kradung Formation of north-eastern Thailand. Palaeontology. DOI: 10.1111/pala.12086

Buffetaut, E.; and Ingavat, R. 1984. The lower jaw of Sunosuchus thailandicus, a mesosuchian crocodilian from the Jurassic of Thailand. Palaeontology. 27 (1): 199–206.

[PaleoIchthyology • 2014] อีสานอิกธิส เลิศบุศย์ศี | Isanichthys lertboosi • A new species of the ginglymodian fish Isanichthys (former Lepidotes) (Actinopterygii, Holostei) from the Late Jurassic Phu Kradung Formation, northeastern Thailand

อีสานอิกธิส เลิศบุศย์ศี | Isanichthys lertboosi 

Deesri, Lauprasert, Suteethorn, Wongko & Cavin 2012

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 (circa 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.

Key words: Holostei, osteology, braincase, phylogeny, Late Jurassic, south-east Asia.

ตัวนักล่าสายพันธุ์ใหม่ “อีสานอิกธิส เลิศบุศย์ศี | Isanichthys lertboosi” ปลานักล่าแห่งจูแรสสิก

http://www.dailynews.co.th/thailand/163661

Deesri, U., Lauprasert, K., Suteethorn, V., Wongko, K. and Cavin, L. 2014. A new species of the ginglymodian fish Isanichthys (Actinopterygii, Holostei) from the Late Jurassic Phu Kradung Formation, northeastern Thailand. Acta Palaeontologica Polonica. 59 (2): 313–331. doi: http://dx.doi.org/10.4202/app.2012.0013

 New species of Ginglymodian Fish from the Late Jurassic of northeast Thailand

http://sciencythoughts.blogspot.com/2012/09/new-species-of-ginglymodian-fish-from.html