The Sao Khua Formation () is a middle member of the Khorat Group. It consists of an alteration of pale red to yellowish-gray, fine to medium-grained sandstone and grayish-reddish brown siltstone and clay. Rare pale red to light gray conglomerates, containing carbonate pebbles, are also characteristic of this formation. This geological formation in Thailand dates to the Early Cretaceous age, specifically the Valanginian through Hauterivian stages.
Dinosaur remains are among the fossils that have been recovered from the formation.Weishampel, David B; et al. (2004). "Dinosaur distribution (Early Cretaceous, Asia)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 563-570. .
Depositional environment Based on paleosols and lithostratigraphy, the Sao Khua Formation is believed to have been deposited in a warm to slightly cool semi-arid climate by a meandering river system. Geochemistry is indicative of a stable humid subtropical climate regime, and sedimentation is thought to have occurred in a floodplain setting which was fed by bedload-rich large meandering channels. Paleocurrent analysis suggests the sand channels at the time of deposition of the formation probably formed a braided channel environment.
Fossil content
Amphibians Amphibians reported from the Sao Khua Formation Genus Species Presence Material Notes Images Anura indet.Indeterminate Nong Bua Lamphu province.Humeri (SHM-PT 529 and SHM-PT 530) and a pelvic girdle (SHM-HY 231). A frog
Reptiles
Dinosaurs Dinosaurs reported from the Sao Khua Formation Genus Species Presence Material Notes ImagesBrachiosauridae indet.IndeterminatePhu Wat B Locality, Phu Kao Mountain rangeDental remainsA brachiosaurid sauropod; similar to other brachiosaurid teeth.Carcharodontosauridae indet.IndeterminateLocality Phu Wiang 1a, Khon Kaen province.PRC-61, "Fragment of the posterior part of a right maxilla".A carcharodontosaurid theropodCompsognathidae? indet.IndeterminateA very small compsognathid theropodDicraeosauridae indet.Indeterminate Phra Prong Single tooth A dicraeosaurid sauropodDiplodocoidea indet.Indeterminate Two cervical vertebra from same individual A diplodocoid sauropodKinnareemimusK. khonkaenensisLocality Phu Wiang 5, Phu Wiang district, Khon Kaen province.Vertebral, pelvic and limb elements.An ornithomimosaurian theropodOrnithurae? Indet.IndeterminateKhok Kong, Kalasin province.A humerus fragment.A ornithurine ornithuran; may represent an early ornithurine, and probably is not an enantiornithine.PhuwiangosaurusP. sirindhornaeKhon Kaen province. Nong Bua Lamphu Province."Partial skeletons, juvenile - adult", & 2 additional vertebrae."Table 13.1," in Weishampel, et al. (2004). Page 268. A scapula and a partial skeleton have also been referred.A euhelopodid somphospondylianCeratosuchini Indet. (Phuwiang spinosaurid B)IndeterminatePW9 'Hin Lad Yao' locality site A and site B, Phu Wiang district, Khon Kaen province.Caudal vertebrae.A ceratosuchin baryonychinePhuwiangvenatorP. yaemniyomiPhu Wiang Site 9B, Phu Wiang Mountain, Khon Kaen province.Partial skeleton including vertebral and limb elements.A megaraptoran theropod SiamosaurusS. suteethorniIsolated teeth."Table 4.1," in Weishampel, et al. (2004). Page 78. A potentially dubious spinosaurine spinosaurid.SiamotyrannusS. isanensis"Pelvis, dorsal, sacral, and caudal vertebrae.""Table 4.1," in Weishampel, et al. (2004). Page 74.A avetheropodan tetanuranSomphospondyli Indet.indeterminateNong Sung locality, Phu Singha locality and Phu Kum Kao locality Dental remains A somphospondylian sauropod; wear facet on crown apex shows difference from PhuwiangosaurusVayuraptorV. nongbualamphuensisPhu Wat Site A1 Locality, Nong Sang, Nong Bua Lamphu province. Partial skeleton including pectoral, limb and pelvic elementsA megaraptoran theropod
Sauropoda indet. 1 and 2
Lizards Lizards reported from the Sao Khua Formation Genus Species Presence Material Notes ImagesAnguimorpha indet.Phu Phok (SK1), Sakhon Nakhorn Province.Fossilized eggs containing embryos.Eggs originally thought to be of theropods like Epidendrosaurus.
Pseudosuchians Pseudosuchians reported from the Sao Khua Formation Genus Species Presence Material Notes ImagesGoniopholisG. phuwiangensisPhu Wiang district.A dentary.Reassigned to Sunosuchus. SiamosuchusS. phuphokensis Phu Phok, Kok Prasil Sub-district, Phu Phan district, Sakon Nakhon province.A partly articulated skeleton (PPC-1). A goniopholidid neosuchian SunosuchusS. phuwiangensisPhu Wiang district.A dentary.A gobionopholid neosuchian; originally reported as Goniopholis phuwiangensis.TheriosuchusT. grandinarisPhu Phok, Kok Prasil Sub-district, Phu Phan district, Sakon Nakhon province."PPC-2, a nearly complete rostrum and dentary".A atoposaurid neosuchianVaranosuchusV. sakonnakhonensisPhu Sung locality near Mueang Sakon Nakhon district, Sakon Nakhon province.A nearly complete skull and skeleton (SM-2021-1-97/101), a nearly complete skull (SM-2023-1-16), and a partial skull table (SM-2023-1-17).A atoposaurid neosuchian
Pterosaurs Pterosaurs reported from the Sao Khua Formation Genus Species Presence Material Notes Images Anhangueridae Indet. Indeterminate Phu Phok, Sakon Nakhon province.An isolated tooth crown (SMP25). Most comparable to anhanguerid teeth from the Cambridge Greensand and Kem Kem beds.
Turtles Turtles reported from the Sao Khua Formation Genus Species Presence Material Notes ImagesIsanemysI. srisukiKalasin, Khon Kaen and Sakon Nakhon provinces.Over 20 shells & additional isolated shell plates.A adocid turtleKizylkumemysK. sp.Khon Kaen, Kalasin and Nong Bua Lamphu provinces.Abundant but very fragmentary shell plates.A carettochelyid turtle ProtoshachemysP. rubra Phu Din Daeng, Nakhon Phanom province.Shell material. A adocid turtle
Fish
Bony fish Bony fish reported from the Sao Khua Formation Genus Species Presence Material Notes Images SiamamiaS. naga Phu Phok. A sinamiid fish
Cartilaginous fish Cartilaginous fish reported from the Sao Khua Formation Genus Species Presence Material Notes ImagesHeteroptychodusH. steinmanniOver 130 fragmentary teeth.A hybodont sharkHybodontiformes Indet.Incertae sedis2 dermal denticles and a cephalic spines.A hybodont sharkHybodus"H." sp. A18 fragmentary crowns.A hybodontid hybodontH. sp. BOver 170 incomplete teeth.A hybodontid hybodontIsanodusI. paladejiPhu Phan Thong, Nong Bua Lamphu province.185 incomplete teeth.A lonchidiid hybodontLonchidionL. khoratensisPhu Phan Thong, Nong Bua Lamphu province.25 teeth.A lonchidiid hybodontMukdahanodusM. trisivakuliiNong Sung district, Mukdahan province.11 isolated crowns.A hybodont sharkParvodusP. sp.19 teeth.A lonchidiid hybodont Ganopristidae Indet. Indeterminate Base of Phu Kum Khao hill in Sahatsakhan, Kalasin province.A tip of rostral denticle (SM2012-1-021). A ganopristid sawskate. The denticle has a single barb similar to Onchopristis, Onchosaurus, and Pucapristis, but is distinguished from all other genera by having a row of enameloid "droplets" on each side. It is one of the earliest sclerorhynchoids, along with Celtipristis and Onchopristis which also appeared in the Barremian.
Invertebrates
Bivalves Bivalves reported from the Sao Khua Formation Genus Species Presence Material Notes Images PseudohyriaP. (Matsumotoina) somanai South of Phu Noi, Khon Kaen province.
See also List of dinosaur-bearing rock formations
References