METRIACANTHOSAURIDS (DINOSAURIA: THEROPODA) FROM THAILAND AND PALEOBIOGEOGRAPHY OF METRIACANTHOSAURIDAE

PLOS ONE, 2019

Acta Palaeontologica Polonica, 2019

The Khok Kruat Formation, which is part of the non-marine Mesozoic Khorat Group of northeastern Thailand, is referred to the Aptian on biostratigraphical evidence. It has yielded an abundant and diverse dinosaur assemblage, comprising saurischians and ornithischians. Isolated theropod teeth indicate several forms of different sizes, including a Siamosaurus-like animal. A recently discovered partial theropod skeleton clearly belongs to a spinosaurid. Sauropods are represented by a form with peg-shaped teeth reminiscent of Phuwiangosaurus; no spoon-shaped teeth have so far been found. Ceratopsians are represented by a well-defined species of Psittacosaurus, P.sattayaraki. Ornithopods are abundant, with an advanced iguanodontian reminiscent of Probactrosaurus. Theropod and ornithopod footprints have also been found. The dinosaur assemblage from the Khok Kruat Formation is clearly different from that from the slightly older Sao Khua Formation, which is dominated by sauropods and in which no ornithischians have so far been found. Comparative studies on the dinosaur assemblages from Thailand may lead to a better understanding of the palaeobiogeographical events linked with faunal change during the Early Cretaceous in South-East Asia.

Annales de Paléontologie, 2019

2019

2019. Two new basal coelurosaurian theropod dinosaurs from the Lower Cretaceous Sao Khua Formation of Thailand. Acta Palaeontologica Polonica 64 (2): 239-260. Megaraptora is a clade of mid to large-sized theropods that are long-snouted, large-clawed, highly pneumatized, and have long and gracile metatarsals. The basal member was reported from the Barremian of Japan. A more derived clade, the Megaraptoridae, is known from the Cenomanian to Santonian of Gondwana. Here two new basal coelurosaurs from the Lower Cretaceous Sao Khua Formation of Thailand are described and named as Phuwiangvenator yaemniyomi gen. et sp. nov. and Vayuraptor nongbualamphuensis gen. et sp. nov. Phuwiangvenator is a megaraptoran coelurosaur and diagnosed by the ventrally flat sacral vertebrae with sulci in the anterior and posterior region of the centra and the anterior rim of metatarsal IV sloping proximolaterally to distomedially and being much lower than that of metatarsal III anteriorly. Vayuraptor is a basal coelurosaur and diagnosed by its astragalus which has two horizontal grooves, two fossae at the base of the ascending process, the ascending process being straight laterally and straight and parallel medially with the medial rim sloping to the tip laterally, and a long and slender astragalar ascending process. Although the position of the basal coelurosaur Vayuraptor remains unclear and must await further discovery, megaraptoran affinities are likely. The Early Cretaceous megaraptoran fossil record has been recovered from the Barremian to Aptian of Asia. All Asian megaraptorans might be a monophyletic clade or a paraphyletic series relative to the Megaraptoridae. Several specimens have been reported from the Aptian to mid-Cretaceous of Australia, and one report from the Albian of South America. These fossils show a high diversity of the Early Cretaceous megaraptorans and a wide distribution during that time. The clade then became more provincial in the Late Cretaceous.

Diversity

An exceptional articulated skeleton of a new basal neornithischian dinosaur, Minimocursor phunoiensis gen. et sp. nov., was discovered in the Late Jurassic Phu Kradung Formation at the Phu Noi locality, Kalasin Province, Thailand, a highly productive non-marine fossil vertebrate locality of the Khorat Plateau. It is one of the best-preserved dinosaurs ever found in Southeast Asia. Minimocursor phunoiensis gen. et sp. nov. shows a combination of both plesiomorphic and apomorphic characters resembling those of Late Jurassic to Early Cretaceous small-bodied ornithischians from China: a low subtriangular boss is projected laterally on the surface of the jugal, the brevis shelf of the ilium is visible in lateral view along its entire length, a distinct supraacetabular flange is present on the pubic peduncle of the ilium, the prepubis tip extends beyond the distal end of the preacetabular process of the ilium, and the manus digit formula is ?-3-4-3-2. The phylogenetic analysis shows that ...

Annales de Paléontologie, 2019

PLOS ONE, 2015

The ichnological assemblage of the PhraWihan Formation (early Early Cretaceous of northeastern Thailand) includes the first sauropod tracks ever found in Thailand. It is reminiscent of the fauna of the underlying Jurassic Phu Kradung Formation with theropods, small ornithischians of uncertain affinities (possibly Hypsilophodon-like ornithopods) and sauropods. It suggests that, in southeastern Asia, an important faunal change occurred in the Early Cretaceous among continental vertebrates, whereas little happened at the Jurassic–Cretaceous boundary.