Here we report a new iguanodontian dentary found from the Lower Cretaceous Khok Kruat Formation,Nakhon Ratchasima,northeast Thailand.A unique character,which is an elongated and flat shape of the dentary ramus,makes i...Here we report a new iguanodontian dentary found from the Lower Cretaceous Khok Kruat Formation,Nakhon Ratchasima,northeast Thailand.A unique character,which is an elongated and flat shape of the dentary ramus,makes it possible to assign the specimen to the new genus of non-hadrosaurid iguanodontian,Ratchasimasaurus suranareae gen.et sp.nov.R.suranareae shows both primitive and derived characters,such as a caudally inclined coronoid process and alveolar trough with a primitive crown impression,and a derived buccal shelf between tooth row and coronoid process.The discovery of a new iguanodontian from the Indochina Terrene,considering that the previously reported 'Probactrosaurus-like' iguanodontian,points out a great diversity of this group in the late Early Cretaceous in Thailand,and corresponds to the Asian iguanodontian diversity at that time.展开更多
A sedimentary profile exposed in soil quarries a few kilometers north of Noen Sa-nga district,Chaiyaphum province,NE Thailand,reveals a Quaternary geological history.The lower part of the soil profile is a gravel depo...A sedimentary profile exposed in soil quarries a few kilometers north of Noen Sa-nga district,Chaiyaphum province,NE Thailand,reveals a Quaternary geological history.The lower part of the soil profile is a gravel deposit characterized by sub-angular to well-rounded pebbles representing an abandoned river sedimentary deposit.The gravel bed in some places is coated by iron oxide as a thin layer of ferricrete at the uppermost part.The upper part of the soil profile is a bright reddish brown structureless sand deposit with fining upward sedimentary structure at the basal portion,the Yasothon soil series.A piece of tektite was discovered at the contact boundary between the two sedimentary units.It is characterized by an irregular shape with a smooth concaved surface regarding as an external mold of a piece of well-rounded pebble.This piece of tektite indicates that a solidified tektite had fallen from high sky then was remelted into a plastic form prior to reach and partly cover a piece of well-rounded pebble.These evidences suggest that there was a meteoritic or cometary impact on our earth surface somewhere in the region then catapulted numbers of melted silica ejecta with vast volume of dust into the sky.The melted silica ejecta were solidified into splash-form tektites with various shapes while they were in the high sky.After that the tektites had fallen down and remelted into a plastic form prior to reach the ground surface and then solidified as a tektite deposit followed by larger-sized sediments and angular quartz fragments forming a fining upward sedimentary structure.The finer sediments were gradually settled down forming a bright reddish brown structureless sand deposit,the Yasothon soil series.This meteoritic impact event occurred at about 0.77 Ma ago as the evidence of the previous tektite radiometric dating.展开更多
基金the Japan-Thailand Dinosaur Project 2007-2009,which is a collaborative research project between the Fukui Prefectural Dinosaur Museum(FPDM) and the Northeastern Research Institute of Petrified Wood and Mineral Resources,Nakhon Ratchasima Rajabhat University(NRRU)
文摘Here we report a new iguanodontian dentary found from the Lower Cretaceous Khok Kruat Formation,Nakhon Ratchasima,northeast Thailand.A unique character,which is an elongated and flat shape of the dentary ramus,makes it possible to assign the specimen to the new genus of non-hadrosaurid iguanodontian,Ratchasimasaurus suranareae gen.et sp.nov.R.suranareae shows both primitive and derived characters,such as a caudally inclined coronoid process and alveolar trough with a primitive crown impression,and a derived buccal shelf between tooth row and coronoid process.The discovery of a new iguanodontian from the Indochina Terrene,considering that the previously reported 'Probactrosaurus-like' iguanodontian,points out a great diversity of this group in the late Early Cretaceous in Thailand,and corresponds to the Asian iguanodontian diversity at that time.
基金the Northeastern Research Institute of Petrified Wood and Mineral Resources,Nakhon Ratchasima Rajabhat University,for financial and logistical supports throughout the research project
文摘A sedimentary profile exposed in soil quarries a few kilometers north of Noen Sa-nga district,Chaiyaphum province,NE Thailand,reveals a Quaternary geological history.The lower part of the soil profile is a gravel deposit characterized by sub-angular to well-rounded pebbles representing an abandoned river sedimentary deposit.The gravel bed in some places is coated by iron oxide as a thin layer of ferricrete at the uppermost part.The upper part of the soil profile is a bright reddish brown structureless sand deposit with fining upward sedimentary structure at the basal portion,the Yasothon soil series.A piece of tektite was discovered at the contact boundary between the two sedimentary units.It is characterized by an irregular shape with a smooth concaved surface regarding as an external mold of a piece of well-rounded pebble.This piece of tektite indicates that a solidified tektite had fallen from high sky then was remelted into a plastic form prior to reach and partly cover a piece of well-rounded pebble.These evidences suggest that there was a meteoritic or cometary impact on our earth surface somewhere in the region then catapulted numbers of melted silica ejecta with vast volume of dust into the sky.The melted silica ejecta were solidified into splash-form tektites with various shapes while they were in the high sky.After that the tektites had fallen down and remelted into a plastic form prior to reach the ground surface and then solidified as a tektite deposit followed by larger-sized sediments and angular quartz fragments forming a fining upward sedimentary structure.The finer sediments were gradually settled down forming a bright reddish brown structureless sand deposit,the Yasothon soil series.This meteoritic impact event occurred at about 0.77 Ma ago as the evidence of the previous tektite radiometric dating.
