The dentary diastema of iguanodontians has been considered to be related to its unique jaw mechanism for herbivorous adaptation. The dentary and diastema lengths of iguanodontians were measured and compared to elucida...The dentary diastema of iguanodontians has been considered to be related to its unique jaw mechanism for herbivorous adaptation. The dentary and diastema lengths of iguanodontians were measured and compared to elucidate the evolution of iguanodontian diastema. A gap in ratios between most non-hadrosaurid iguanodontians and hadrosaurids was observed, suggesting that all non- hadrosaurid iguanodontians, expect for Ouranosaurus nigeriensis and Protohadros byrdi, lack a diastema or have a short diastema, although some other taxa have been considered to have a long diastema in previous studies. In non-hadrosaurid iguanodontians, some large-sized forms, such as Iguanodon bernissartensis, Shuangmiaosaurus gilmorei, and possibly Eolambia caroljonesa, had a short diastema through ontogeny, whereas Ouranosaurus nigeriensis and Protohadros byrdi developed a long diastema convergently. The development of a long diastema of hadrosaurine hadrosaurids may be different from that of lambeosaurine hadrosaurids. Some hadrosaurines （Edmontosaurus annectens, Edmontosaurus regalis, and Saurolophus angustirostris） may have developed a long diastema in the subadult stage and showed little elongation of dentary diastema through ontogeny. Lambeosaurines （Corythosaurus casuarius and Lambeosaurus lambei） tend to have a short diastema in the embryonic and subadult stages, and an elongated diastema from the subadult to adult stages.展开更多
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
文摘The dentary diastema of iguanodontians has been considered to be related to its unique jaw mechanism for herbivorous adaptation. The dentary and diastema lengths of iguanodontians were measured and compared to elucidate the evolution of iguanodontian diastema. A gap in ratios between most non-hadrosaurid iguanodontians and hadrosaurids was observed, suggesting that all non- hadrosaurid iguanodontians, expect for Ouranosaurus nigeriensis and Protohadros byrdi, lack a diastema or have a short diastema, although some other taxa have been considered to have a long diastema in previous studies. In non-hadrosaurid iguanodontians, some large-sized forms, such as Iguanodon bernissartensis, Shuangmiaosaurus gilmorei, and possibly Eolambia caroljonesa, had a short diastema through ontogeny, whereas Ouranosaurus nigeriensis and Protohadros byrdi developed a long diastema convergently. The development of a long diastema of hadrosaurine hadrosaurids may be different from that of lambeosaurine hadrosaurids. Some hadrosaurines （Edmontosaurus annectens, Edmontosaurus regalis, and Saurolophus angustirostris） may have developed a long diastema in the subadult stage and showed little elongation of dentary diastema through ontogeny. Lambeosaurines （Corythosaurus casuarius and Lambeosaurus lambei） tend to have a short diastema in the embryonic and subadult stages, and an elongated diastema from the subadult to adult stages.
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.
