The

Early Cretaceous The Early Cretaceous ( geochronological name) or the Lower Cretaceous (chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pro ...

Phu Kradung Formation is the lowest member of the

Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...

Khorat Group The Khorat Group is a Group (stratigraphy), stratigraphic group located within the Khorat Plateau in the Isan region of Thailand. It was first defined as the Khorat Series by Brown et al in 1953 and was redefined as the Khorat Group by Ward and B ...

which outcrops on the

Khorat Plateau The Khorat Plateau ( th, ที่ราบสูงโคราช) is a plateau in the northeastern Thai region of Isan. The plateau forms a natural region, named after the short form of Nakhon Ratchasima, a historical barrier controlling access ...

Isan Northeast Thailand or Isan (Isan/ th, อีสาน, ; lo, ອີສານ; also written as Isaan, Isarn, Issarn, Issan, Esan, or Esarn; from Pali ''īsānna'' or Sanskrit ईशान्य ''īśānya'' "northeast") consists of 20 provin ...

, Thailand. This

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

consists of micaceous, brown to reddish-brown

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, p ...

beds with minor brown and grey

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

and

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

beds. Occasional lime-noduled conglomerate occurs.Suteetorn and Jarnyahran (1986). "Geological Map of Thailand 1:250,000, Sheet NE 48-14 (Roi Et). The Phu Kradung Formation sediments were deposited in a lake-dominated floodplain cut by meandering and occasionally braided river channels.Racey and Goodall (2009). "Late Palaeozoic and Mesozoic Ecosystems in SE Asia". Geological Society. London. Special Publication 315 Pp 69-84. The Phu Kradung Formation is considered, on the basis of recent vertebrae fossil discoveries, to be

Late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

in age. However, new

palynology Palynology is the "study of dust" (from grc-gre, παλύνω, palynō, "strew, sprinkle" and '' -logy'') or of "particles that are strewn". A classic palynologist analyses particulate samples collected from the air, from water, or from deposit ...

and biostratigraphic data suggests an age of

for the upper section.

Dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

remains have been recovered from this formation, although none have yet been referred to a specific

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

.Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. . ''

Chalawan ''Krai Thong'' or ''Kraithong'' ( th, ไกรทอง, ) is a Thai folktale, originating from Phichit Province. It tells the story of Chalawan, a crocodile lord who abducts a daughter of a wealthy Phichit man, and Kraithong, a merchant from No ...

'', an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

of pholidosaurid

mesoeucrocodylia Mesoeucrocodylia is the clade that includes Eusuchia and crocodyliforms formerly placed in the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day. Diagnosis It was long known that M ...

n, is currently known solely from its

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, a nearly complete

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...

collected in the early 1980s from a road-cut near the town of

Nong Bua Lamphu Nong Bua Lam Phu () is a town in Thailand, capital of Nong Bua Lamphu Province. It is on the central eastern border of the province, approximately 45 kilometers south-west of the city of Udon Thani and from there, accessed by route 210. The town ...

in the upper part of the Phu Kradung Formation. This single specimen is the most well preserved vertebrate fossil that has been found from the formation. It contains a single species, ''Chalawan thailandicus''.

Fossil content

Amphibians

Reptiles

Dinosaurs

Pseudosuchians

Pterosaurs

Turtles

Fish

Bony fish

Cartilaginous fish

Multiple fin spines have been found in the Phu Kradung Formation which cannot be precisely identified.

Plants

References

{{Reflist Geologic formations of Thailand Lower Cretaceous Series of Asia Cretaceous Thailand Berriasian Stage Sandstone formations Mudstone formations Paleontology in Thailand Jurassic System of Asia Tithonian Stage