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A New Iguanodontian Dinosaur from the Lower Cretaceous Khok Kruat Formation, Nakhon Ratchasima in Northeastern Thailand
Abstract
: 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.
... Although the exact genus or species has not yet been identified from the Late Jurassic Phu Kradung Formation, material of stegosaurids and basal neornithischians were excavated (Buffetaut et al. 2001. By contrast, the late Early Cretaceous Khok Kruat Formation (Aptian-Albian) yields abundant neornithischian dinosaurs comprising three taxa of iguanodontians, Siamodon nimngami (Buffetaut and Suteethorn 2011), Ratchasimasaurus suranareae (Shibata et al. 2011), and Sirindhorna khoratensis , plus one taxon of basal ceratopsian, Psittacosaurus sattayaraki (Buffetaut and Suteethorn 1992). The Khok Kruat Formation of Thailand is considered the lateral equivalent to the Grès Supérieurs Formation of southern Laos (Cappetta et al. 1990;Buffetaut et al. 2005b;Racey 2009;Allain et al. 2012). ...
... Previous study. R. suranareae is a hadrosauroid (Madzia et al. 2020; and the material comprises a complete toothless left dentary with 18 alveoli (Shibata et al. 2011). One autapomorphy of R. suranareae is its elongated and dorsoventrally shallow dentary ramus, with a ratio of length (from the rostral to the caudal margin)/height (at the middle of the dentary) of 6.9 (Shibata et al. 2011). ...
... R. suranareae is a hadrosauroid (Madzia et al. 2020; and the material comprises a complete toothless left dentary with 18 alveoli (Shibata et al. 2011). One autapomorphy of R. suranareae is its elongated and dorsoventrally shallow dentary ramus, with a ratio of length (from the rostral to the caudal margin)/height (at the middle of the dentary) of 6.9 (Shibata et al. 2011). It shows both primitive and derived characters for iguanodontians, such as a caudally inclined coronoid process and alveolar trough with a primitive crown impression, and a derived buccal shelf between the tooth row and the coronoid process (Shibata et al. 2011). ...
Ornithischian dinosaurs have been discovered in Thailand, Laos, and Malaysia. These bird-hipped herbivores remain relatively rare by comparison with saurischian dinosaurs. In the Late Jurassic, stegosaurs and basal neornithischians from Thailand showed similarities to Middle-Late Jurassic taxa from China. Ornithischians appeared in the fossil record again during the late Early Cretaceous (Aptian-Albian) of Thailand and Laos. They are represented by non-hadrosaurid iguanodontians and basal ceratopsians. A few specimens have been reported from poorly dated Early Cretaceous rocks of Malaysia. Here, we illustrate the diversity of ornithischian assemblages in Southeast Asia and discuss their palaeobiogeographical implications.
... Sha (2007) and Allain et al. (2012) consider that the upper part of the Khok Kruat and the Gr es sup erieurs formations could be Albian in age on the basis of the Trigonioidacea fauna. In both formations iguanodontid, sauropod and spinosaurid dinosaurs are present, but they belong to distinct genera (Allain et al. 1999(Allain et al. , 2012Buffetaut & Suteethorn 2011;Shibata et al. 2011). In the Khok Kruat Formation, dinosaur remains are accompanied by a diverse assemblage of sharks (Cuny et al. 2008), turtles (Tong et al. 2009) and crocodiles (Kubo et al. 2018) but, strangely enough, the Gr es sup erieurs Formation has yielded very few nondinosaurian vertebrates. ...
... The excavation from Ban Saphan Hin, Thailand, a village close to the city of Nakhon Ratchasima in the province of the same name, occurs in a small outcrop of the Khok Kruat Formation. It is one of the richest assemblages from the Khok Kruat Formation in terms of diversity of vertebrates, comprising dinosaurs, turtles, crocodiles, hybodont sharks and fishes (Cappetta et al. 1990;Lauprasert et al. 2009;Tong et al. 2009;Buffetaut & Suteethorn 2011;Shibata et al. 2011;Kubo et al. 2018). The material of this assemblage consists mostly of fragmentary remains, which are embedded in a reddish conglomeratic sandstone. ...
A new genus and new species of ginglymodian is described from the Aptian Grès supérieurs Formation of the Savannakhet Basin, Laos (Lao People's Democratic Republic), found at the Ban Lamthouay locality. The fish is known from a single isolated head, which shows enough diagnostic characters to characterize a new taxon. It represents the first named actinopterygian fish from the Mesozoic of Laos. Among the derived characters are a very short and deep head, a series of very deep anterior infraorbitals, and a mosaic arrangement of the suborbitals. Recognition of this new form led us to identify isolated bones previously found in the Thai Khok Kruat Formation in Thailand, a lateral equivalent of the Grès supérieurs Formation. Two localities, Ban Saphan Hin and Khok Pha Suam, have yielded remains, in particular bones of the skull roof and of the circumorbital series as well as a partial postcranial body, assignable, with caution, to the new genus. When included in a cladistic analysis, the new taxon is placed at the base of the lepisosteoid lineage, together with Isanichthys known from an older formation in Thailand. The phylogenetic pattern obtained differs in some details from previous analyses and points out the pivotal role that some taxa play in the reconstruction of the phylogenies of ginglymodians. This new taxon enriches the diverse Late Jurassic–Early Cretaceous ginglymodian assemblage in South-east Asia, which surprisingly shows no evidence of teleosts.
http://zoobank.org/urn:lsid:zoobank.org:pub:70564BE0-939C-4217-9D82-9E51AA298A8C
... Fossil records of non-hadrosaurid hadrosauriform dinosaurs in Asia have been accumulated in this century [1][2][3][4][5][6][7][8][9][10][11]. Although these discoveries mainly came from China and Mongolia, new findings have been known from Uzbekistan [12] Kazakhstan [13], Japan [14,15] and Thailand [16,17]. However, well-preserved iguanodontian specimens were restricted in China and Mongolia; for instance, Jinzhousaurus yangi was known as the almost complete articulated skeleton The Khok Kruat Formation usually does not crop out in Nakhon Ratchasima and thin reddish soil usually covers over those rocks. ...
... Two hadrosauroids have been previously known from the Khok Kruat Formation: Siamodon nimingami [16] and Ratchasimasaurus suranareae [17] (Fig 15). Siamodon was based upon an isolated maxilla. ...
A new basal hadrosauroid dinosaur from the Lower Cretaceous Khok Kruat Formation of Thailand, Sirindhorna khoratensis gen. et sp. nov is described. The new taxon is based on composite skull and mandible including premaxilla, maxilla, jugal, quadrate, braincases, predentary, dentaries, surangular, and maxillary and dentary teeth. It is diagnostic by such characters as, sagittal crest extending along entire dorsal surface of the parietal and reaching the frontoparietal suture (autapomorphy), transversely straight frontoparietal suture, caudodorsally faced supraoccipital, no participation of the supraoccipital in the foramen magnum, mesiodistally wide leaf-shaped dentary tooth with primary and secondary ridges on the lingual surface of the crown, perpendicularly-erected and large coronoid process of dentary, and nonvisible antorbital fossa of the maxilla in lateral view. Phylogenetic analysis revealed S. khoratensis as among the most basal hadrosauroids. Sirindhorna khoratensis is the best-preserved iguanodontian ornithopod in Southeast Asia and sheds new light to resolve the evolution of basal hadrosauriforms.
... In Southeast Asia, more recently diverging neornithischians have been described, including iguanodontian ornithopods and basal ceratopsians such as Mandschurosaurus laosensis from the Grès Supérieurs Formation of Laos [14]; Siamodon nimngami [15], Ratchasimasaurus suranareae [16], Sirindhorna khoratensis [17], and Psittacosaurus sattayaraki [18] from the Khok Kruat Formation of Thailand; all of these cerapodan neornithischians (ornithopods and marginocephalians) are Early Cretaceous (Aptian-Albian) in age. However, no valid taxon had been described yet from an older formation. ...
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 this
dinosaur is among the most basal neornithischians. This study provides a better understanding of the early evolution and taxonomic diversity of ornithischians in Southeast Asia.
... Paleontologists have excavated more than 16 types of dinosaur bone fossils in Thailand, of which 12 are unique worldwide, with the dinosaur taxonomy discovered in Thailand shown in Figure 3 (Buffetaut et al., 1996(Buffetaut et al., , 2000(Buffetaut et al., , 2009Buffetaut and Ingevat, 1986;Buffetaut and Suteethorn, 1992, 1993, 2011Chokchaloemwong et al., 2019;Samathi et al., 2019Samathi et al., , 2022Shibata et al., 2011Shibata et al., , 2015. KKGp is of global importance in paleontology because of five dinosaur species identified here, which are described as follows ( Figure 4a): ...
Khon Kaen Geopark (KKGp), located on the Mesozoic sandstone syncline of the Khorat Plateau, northeastern Thailand, is distinguished by spatially small-scale (100–10,000 m²) forms of geodiversity (rocks, fossils, structures, landforms, landscapes, and minerals). Field investigations and classification suggest that paleontological sites present the first dinosaur species in Thailand and confirm the existence of five dinosaur species: Phuwiangosaurus sirindhornae, Kinnareemimus khonkaenensis, Siamotyrannus isanensis, Siamosaurus suteethorni, and Phuwiangvenator yaemniyomi. The geomorphological sites feature representative sandstone landforms, including waterfalls, cliffs, caverns, honeycombs, pedestal rocks, and rugged surfaces with irregular features. In addition, the mineralogical site has a Uranium Field (Cu–U-related ore deposit). This work proposes four geoeducation models: a geodiversity one-day trip, a geomorphological study trail, a geoethical study site, and the Phu Wiang Dinosaur Museum for geoconservation development for school and university students. According to the geoeducation assessment, KKGp has considerable educational value based on the Accessibility, Safety, Invulnerability, Observation condition, and Didactic (ASIOD) framework for geology and geography. Our findings suggest ways to broadly transform and enhance the geoeducation concept through a storytelling narrative of the geopark.
... Various workers have investigated the fossil record of southeast Asia (Thailand, Laos, Cambodia) as a means to better understand and decipher this complex record; however, conflicting hypotheses about the paleobiogeography of many clades, particularly terrestrial vertebrates (e.g., dinosaurs) remain unresolved (Russell and Zheng, 1993;Russell, 1995;Rich and Young, 1996;Buffetaut and Suteethorn, 1998;Barrett et al., 2002;Upchurch et al., 2002;Lockley et al., 2006;Fernandez et al., 2009;Brusatte et al., 2010;Prieto-Marquez, 2010;Shibata et al., 2011). Poor age control for many of these faunas is particularly problematic. ...
We describe the sedimentology, geochronology, and geochemistry of the Early Cretaceus Sao Khua Formation of the Khorat Basin, northeastern Thailand, and report a temporal range adjustment for its dinosaurian assemblage. Facies analysis and architectural studies reveal that sedimentation occurred within a floodplain setting fed by large meandering bedload-rich channels. Interfluve areas comprised freshwater lakes and emergent areas subject to pedogenic modification. Multiple paleosol types are identified and geochemistry is indicative of a stable humid subtropical climate regime. Based on radiometric dating of detrital zircons (via LA-ICP-MS), we interpret that the middle part of the Sao Khua Formation was deposited no later than 133.8 (±1.8) Ma (late Valanginian), and grain ages collected from the overlying lowermost Phu Phan Fm constrain sedimentation of the upper part of the Sao Khua Formation to no earlier than 132.4 (±2.0) Ma (early Hauterivian). In consideration of the Early Cretaceous regional tectonic framework, we interpret that youthful igneous zircon grains are derived from the adjacent South China-Vietnam South Borneo Volcanic Arc. We establish that the entombed dinosaur biota (including members of the Ornithomimosauria, Spinosauridae, Megaraptora, and Somphospondylia) is ~5–9 million years older than previously recognized and that these records are among the oldest known globally for these clades. Constraining the age of the Sao Khua Formation indicates that the shift from sauropod-dominated, ornithischian depauperate ecosystems of the Sao Khua Formation to iguanodontian-rich ecosystems of the Khok Kruat Formation occurred sometime between the early Hauterivian and Aptian on the Khorat Plateau.
... Three taxa of hadrosauroids have been described from the Khok Kruat Formation in Nakhon Ratchasima Province, including Siamodon nimngami (Buffetaut and Suteethorn 2011), Ratchasimasaurus suranareae (Shibata et al. 2011), and Sirindhorna khoratensis (Shibata et al. 2015). Material of S. nimngami and R. suranareae encompass only a left maxilla and a left dentary, respectively. ...
The Khok Pha Suam locality in the province of Ubon Ratchathani, northeastern, Thailand, is known as “the last home of Thai dinosaurs”, because it belongs to the Lower Cretaceous Khok Kruat Formation (Aptian-Albian) which is currently the youngest Mesozoic vertebrate fossil producing formation in the Khorat Group. Here, we describe a diverse vertebrate assemblage, including hybodonts, ray-finned fishes, turtles, crocodyliforms, pterosaurs, and dinosaurs from the Khok Pha Suam locality. The updated data on the Khok Kruat fauna provides a better understanding of the variety and distribution of Early Cretaceous continental ecosystems, which are useful for palaeoenvironmental reconstruction. In addition to consolidating unincorporated data on fauna, this study also provides the palaeontological data necessary to illustrate the palaeoecosystem to the general public, as well as improving the academic value of the Pha Chan-Sam Phan Bok Geopark.
... In the last decade, Thailand has yielded a huge number of Mesozoic non-marine fossil vertebrates, ranging from the Late Triassic to the late Early Cretaceous [16]. Nevertheless, dinosaur remains from the Lower Cretaceous Khok Kruat Formation have hitherto been scarce, and only iguanodontian ornithopods have been described based on isolated remains [17][18][19]. In this study, a new theropod taxon is described based on extensive cranial and postcranial materials collected in a locality of the Khok Kruat Formation of the Japan-Thailand Dinosaur Project (abbreviated as JTDP [19]; Fig 1). ...
The isolated fossil remains of an allosauroid theropod from the Lower Cretaceous Khok Kruat Formation of Khorat, Thailand, are described in this study. Detailed observations support the establishment of a new allosauroid, Siamraptor suwati gen. et sp. nov. This new taxon is based on a composite cranial and postcranial skeleton comprising premaxilla, maxilla, jugal, surangular, prearticular, articular, vertebrae, manual ungual, ischium, tibia, and pedal phalanx. It is distinguished from other allosauroids by characters such as a jugal with straight ventral margin and dorsoventrally deep anterior process below the orbit, a surangular with a deep oval concavity at the posterior end of the lateral shelf and four posterior surangular foramina, a long and narrow groove along the suture between the surangular and the prearticular, an articular with a foramen at the notch of the suture with the prearticular, an anterior cervical vertebra with a pneumatic foramen (so-called ‘pleurocoel’) excavating parapophysis, and cervical and posterior dorsal vertebrae penetrated by a pair of small foramina bilaterally at the base of the neural spine. The presence of a huge number of camerae and pneumatopores in cranial and axial elements reveals a remarkable skeletal pneumatic system in this new taxon. Moreover, the phylogenetic analyses revealed that Siamraptor is a basal taxon of Carcharodontosauria, involving a new sight of the paleobiogeographical context of this group. Siamraptor is the best preserved carcharodontosaurian theropod in Southeast Asia, and it sheds new light on the early evolutionary history of Carcharodontosauria.
... The Khok Kruat Formation has yielded dinosaur remains including the theropods reviewed below, sauropods, the ceratopsian Psittacosaurus sattayaraki (Buffetaut et al., 1989;Buffetaut and Suteethorn, 1992;, and three iguanodontian ornithopods. These are Ratchasimasaurus suranarii (Shibata and Jintasakul, 2008;Shibata et al., 2011), Siamodon nimngami (Buffetaut et al., 2005b;Buffetaut and Suteethorn, 2011), and Sirindhorna khoratensis . Dinosaur footprints also have been reported from the formation (Buffetaut et al., 2005b). ...
Several non-avian theropod dinosaurs, as well as some Mesozoic birds, have been reported from Southeast Asia. The fossils are dominantly found in northeastern Thailand, however, one bizarre theropod has been described from Laos, one theropod has been reported from Malaysia, and some avian and non-avian theropods have been recently reported from Myanmar. The temporal distribution of Southeast Asian theropods ranges from the Late Jurassic to the mid-Cretaceous. All non-avian theropod faunas from Southeast Asia consist of non-maniraptoran tetanurans. They show similarity to Chinese plus Japanese theropods during the Early Cretaceous in broad systematic terms. During this time, megaraptorans can be found only in Japan, Australia, Brazil, and possibly Thailand, whereas tyrannosauroids can be found in China, Europe, possibly Brazil and Australia. Spinosaurids, carcharodontosaurians, and some coelurosaurs such as ornithomimosaurs were almost cosmopolitan. Metriacanthosaurids, on the other hand, were endemic to Europe and Asia including China and Thailand during the Middle to Late Jurassic.
... Mainly, the tracks of small-sized theropod were recognized on the same bedding plane. On the basis of the track directions, the theropod tracks can be separated into two groups, Group A (tracks indicating a NW movement direction) and Group B Buffetaut et al., 2009;Buffetaut and Suteethorn, 2011;Meesook, 2011;Shibata et al., 2011Shibata et al., , 2015Kozu et al., 2016). ...
The Khok Kruat Formation is the upper part of the Khorat Group, which consists of upper Lower Cretaceous non-marine sedimentary rocks in northeastern Thailand. Many dinosaur footprints have been known from the upper Lower Cretaceous (Aptian–Albian) Khok Kruat Formation at the Huai Dam Chum (Tha Uthen) site, northeastern Thailand. Approximately 600 tracks occur in thin mudstone layer of the northern part of the outcrop at the Huai Dam Chum track site. Two types of footprints, small-sized theropod and crocodylomorph are imprinted with mud cracks and ripple marks on the thin mud layer. Most of footprints are referred to cf. Asianopodus, and are imprinted by small-sized theropoda, probably ornithomimosauria. Theropod tracks are mainly separated into two groups, Group A and Group B. From ichnological viewpoints, the small-sized theropod track assemblage indicates the herd behaviour and its idiosyncratic group composition. In particular, the histogram of size-frequency measurements of Group A shows the anomalous bimodal distribution. We consider that there are two hypotheses; the first one is due to the male-female difference, and the second is a result of the different growing stage.
... The diagnosis of this taxon does not include any autapomorphic states, which suggests that until more material is collected and described, this taxonomic name should be considered a nomen dubium. It is possible that this material is referable to Ratchasimasaurus, which was described (almost simultaneously) by another group of researchers (Shibata, Jintasakul & Azuma, 2011). However, the latter authors suggest (based upon undescribed maxillae) that there may have been two distinct taxa in the Khok Kruat Formation. ...
The history of discovery and interpretation of several dinosaurs collected from quarries near the town of Hastings during the latter half of the 19th century is more complicated than it should be. Samuel Husbands Beckles and Charles Dawson collected several large ornithopod skeletons from this area, but just a few bones from these skeletons were subsequently described and interpreted (principally) by Richard Owen and Richard Lydekker. All these specimens merited recognition because they had the potential to contribute to an on-going debate about the anatomical structure and relationships of the iconic Wealden dinosaur Iguanodon. Unfortunately, no detailed description of these important skeletons was published in later years. Furthermore, previously known associations of bones and even provenance information, linked to the specimens that were gradually acquired by the Natural History Museum, are unclear. Confusion may have arisen because Richard Lydekker used the private collector Charles Dawson as a voluntary curatorial assistant. This account documents the past work on the osteology of material that can be attributed to Hypselospinus fittoni. Nearly all such material is described here for the first time, and every effort has been made to re-establish associations between bones as well as provenance information. A skeletal reconstruction of Hypselospinus is attempted on the basis of the hypodigm. Most of the on-going confusion concerning the affinity of this material with either Hy. fittoni or its sympatric contemporary Barilium dawsoni has been resolved. Hypselospinus fittoni (Lydekker, 1889) is rediagnosed on the basis of this new and relatively comprehensive anatomical description, and this animal is compared with known contemporary and closely related taxa. Some recently published accounts claiming to be revisions of the taxonomy of Wealden ‘iguanodonts’, including material belonging to the hypodigm of Hy. fittoni, have failed to adhere to basic taxonomic principles and have caused more confusion than was strictly necessary. The systematic position of Hypselospinus is reassessed cladistically. The cladistic analysis forms the basis for a revised hierarchical classification of derived ornithopods. The consensus topology generated by the systematic analysis has been used to explore the phylogenetic history of these dinosaurs and create an internally consistent classificatory hierarchy (phylogenetic definitions and Linnaean diagnoses are given for critical positions in the topology). This analysis suggests that there is a fundamental split amongst the more derived (clypeodontan) ornithopod ornithischians into the clades Hypsilophodontia and Iguanodontia. There is evidence for anatomical parallelism and convergence (homoplasy) particularly between large-bodied representatives of both clades. Hypselospinus is one of the earliest known styracosternan iguanodontians and displays anatomical characteristics that presage the evolution of the extraordinarily abundant and diverse hadrosaurs of the latest Cretaceous (Campanian−Maastrichtian). These observations cast fresh light on the phylogeny, classification, diversity, and biology of derived ornithopods. There is little doubt that Hy. fittoni could have been understood far better more than a century ago. That this statement is undoubtedly true is reflected in the century of doubt and confusion that has surrounded this taxon and its original incarnation as Iguanodon fittoni. © 2014 The Linnean Society of London
... The coronoid process of right dentary is directed posterodorsally, identical to the holotype of Bolong (Wu and Godefroit 2012). This morphology is similar to that seen in Ratchasimasaurus (Shibata et al. 2011) and many nonankylopollexian ornithopods, such as Hypsilophodon (Galton 1974), Orodromeus (Scheetz 1999) and in Hypacrosaurus, the embryonic dentary is similar in morphology to the corresponding adult element (Horner and Currie 1994). ...
We describe an early juvenile specimen (ZMNH M8812) of Bolong yixianensis from the Yixian Formation (Lower Cretaceous) of Ningcheng County, Nei Mongol, China. The specimen consists of an almost complete skeleton preserved two-dimensionally on a slab. The short and deep skull proportions and unfused neurocentral sutures in most preserved vertebrae suggest that the ZMNH M8812 is a juvenile individual. Osteohistological study confirms a very early developmental stage. The study reveals the ontogenetic changes of Bolong for the first time. The specimen revealed one additional autapomorphy for Bolong yixianensis: the lingual face of the maxillary crown is bounded by thickened mesial and distal margins and bisected by a prominent median principal ridge. The study revealed the following ontogenetic trends of Bolong: increased tooth rows in both maxilla and dentary, increased robustness of the jugal and scapula, the radius and ulna become more robust and shorter relative to the hindlimb and the metatarsals become proportionally shorter. ZMNH M8812 represents the first juvenile non-hadrosaurid iguanodontian specimen described from the Lower Cretaceous of eastern Asia.
... Lateral to the symphysis, a narrow groove for articulation with the corresponding lateral process of the predentary extends caudodorsally along the rostrolateral surface of the rostral ramus (Fig. 4D). There is a short diastema between the caudal end of the predentary groove and the rostralmost alveolus, as in Ouranosaurus [26], Altirhinus [32], Jinzhousaurus [45], Equijubus [33], Ratchasimasaurus [46], Xuwulong [35], Probactrosaurus gobiensis [13], Protohadros [10], and Jeyawati [11]. ...
Eolambia caroljonesa is known from copious remains from the lower Cenomanian Mussentuchit Member of the Cedar Mountain Formation in eastern Utah; however, the taxon has been only briefly described. Thus, we present herein a complete osteological description of Eolambia.
The description of Eolambia presented here is based upon the holotype partial skeleton (CEUM 9758), paratype partial skull (CEUM 5212), and abundant disarticulated elements from two bonebeds that contain juvenile individuals. These remains allow the skeletal anatomy of Eolambia to be documented almost fully and a revised diagnosis to be proposed.
The description provided here facilitates comparisons between Eolambia and other iguanodontians and allows Eolambia to be coded for additional characters in phylogenetic analyses. The close affinity between Eolambia and Probactrosaurus gobiensis from the Early Cretaceous of China supports previous hypotheses of faunal interchange between Asia and North America in the early Late Cretaceous.
... NHMUK R3741 (cf. Mantellisaurus in McDonald [21]; considered to represent a possible distinct taxon by Carpenter and Ishida [22]) was coded as a separate OTU, and four new taxa were added: Delapparentia [23], Ratchasimasaurus [24], Xuwulong [25], and Glishades [26]. Finally, the coding of character 112 (ilium, morphology of dorsal margin of postacetabular process dorsal to ischial peduncle) for Iguanacolossus was changed from 1 (laterally bulging eminence dorsal to ischial peduncle, no modification of dorsal margin) to 2 (mediolaterally thickened dorsal margin compared to dorsal margin above pubic peduncle) upon reconsideration of the morphology of the ilium [following discussion with J. I. Kirkland, pers. ...
The precise phylogenetic relationships of many non-hadrosaurid members of Iguanodontia, i.e., basal iguanodonts, have been unclear. Therefore, to investigate the global phylogeny of basal iguanodonts a comprehensive data matrix was assembled, including nearly every valid taxon of basal iguanodont. The matrix was analyzed in the program TNT, and the maximum agreement subtree of the resulting most parsimonious trees was then calculated in PAUP. Ordering certain multistate characters and omitting taxa through safe taxonomic reduction did not markedly improve resolution. The results provide some new information on the phylogeny of basal iguanodonts, pertaining especially to obscure or recently described taxa, and support some recent taxonomic revisions, such as the splitting of traditional "Camptosaurus" and "Iguanodon". The maximum agreement subtree also shows a close relationship between the Asian Probactrosaurus gobiensis and the North American Eolambia, supporting the previous hypothesis of faunal interchange between Asia and North America in the early Late Cretaceous. Nevertheless, the phylogenetic relationships of many basal iguanodonts remain ambiguous due to the high number of taxa removed from the maximum agreement subtree and poor resolution of consensus trees.
Khon Kaen Geopark, representing an area of dinosaur fossil diversity, was selected for investigations to reveal the origin and tectonic setting of the Khorat Group. The area occupied by Mesozoic sedimentary rocks of four formal formations of the Khorat Group, namely the Phra Wihan Formation (PWF), Sao Khua Formation (SKF), Phu Phan Formation (PPF), and Khok Kruat Formation (KKF). A field investigation and macroscopic observations suggested that the immature sedimentary rocks of the study area are mainly clast-supported, pebbly sandstone and siltstone with few calcretes. The 50 rock samples that were selected for petrographical and geochemical investigations revealed that the sandstones of the PWF and PPF are quartz arenite and sublitharenite, with some subarkose, whereas those of the SKF are mainly subarkose and sublitharenite. In addition, the KKF dominantly presents sub-litharenite with pebbles and calcretes. Mesozoic sandstones contain quartz, feldspars, various types of rock fragments, and accessory minerals (biotite, muscovite, zircon, and tourmaline), with siliceous, ferrous, and calcareous cement.
The skull of the hadrosauroids is the most complex structure of its anatomy, with features of systematic and phylogenetic
importance. Recent discoveries have increased the anatomical diversity, causing confusion to recognize unique
characters or derivatives, by using different terms for the same structures. This situation is more complex when Spanish-
speaking researchers and students need to make a detailed description. This work represents the second part of the
anatomical guide of the hadrosauroids, which includes an updated and illustrated introductory compendium of their
cranial anatomy. The purpose is to facilitate the handling of new data of phylogenetic importance and the taxonomic
identification of isolated or associated remains, using morphotypes
This work aims to investigate the geodiversity of the Khorat Geopark area, northeastern Thailand, and assess the geological sites that are connected to biological and cultural heritage, as well as community activities that enhance geoconservation and sustainable development. The geological diversity of Khorat Geopark dates back to the late Jurassic period and continues to the present day, resulting from the deposition of terrestrial sedimentary rocks from the Khorat Group. The Khorat rock group has been uplifted and eroded to form the Khorat Plateau with a unique landscape and important geological features of the cuesta landform on the western part of the Khorat Geopark. On the four corners of Nakhon Ratchasima City, there are numerous fossils of outstanding Early Cretaceous dinosaurs and other reptiles and Cenozoic fossils of both flora and fauna, mainly mammalian remains and, in particular, ancient elephants. Geological sites in the Khorat Geopark area were weighted and scored based on their scientific value (SV), potential value for education (EV), potential value for tourism (TV), and degradation risk variables (DV). According to the assessment, the Khorat Geopark's 24 geosites are of moderate to high value, with 7 sites having 301–400 scores and 5 sites having a high level of international value. Most of them are related to fossils and cuestas. Thus, the fossil diversity of the Khorat Geopark is of international scientific significance. Khorat Geopark is managed under the conservation, education, and sustainable development initiatives using a bottom-up method with multiple networks, both local communities and local governments, especially through the Home-Temple-School (HTS) model.
Is an up-date review of the postcranial osteology of hadrosaurs
Iguanodon galvensis is the second valid species in the European and Barremian large-ornithopod genus Iguanodon. In the present work, the I. galvensis holotype and referred material from the lower Barremian of Spain are described and discussed in detail. As a result, emended diagnoses of Iguanodon, I. galvensis and I. bernissartensis are proposed; I. galvensis can now be identified by three autapomorphies in the dentary, ischium and femur as well as a unique combination of characters. Moreover, I. galvensis is compared with other European Early Cretaceous large styracosternans. Finally, a new phylogenetic hypothesis is proposed that resolves Iguanodon (I. bernissartensis, I. galvensis) with the Valanginian Barilium dawsoni into a monophyletic clade (Iguanodontoidea).
A second basal hadrosauroid dinosaur, Zuoyunlong huangi gen. et sp. nov. is reported from the early Late Cretaceous Zhumapu Formation in Zuoyun County, Shanxi Province, northern China. Zuoyunlong preserves a partial right ilium and ischium, and is unique in having a very short postacetabular process 50% as long as the iliac central plate. Our cladistic analysis recovers Zuoyunlong as the most basal Late Cretaceous hadrosauroid, with a sister-taxon relationship with Probactrosaurus from the late Early Cretaceous of Inner Mongolia. Including Zuoyunlong, four Cenomanian basal hadrosauroids have been recorded, and the two taxa in North America (Eolambia and Protohadros) represent the earliest known hadrosauroids outside of Asia. In the light of the proposed phylogenetic topology and biogeographic data, the discovery of Zuoyunlong indicates that the first dispersal of hadrosauroids from Asia to North America probably happened around the boundary between the Early and Late Cretaceous.
New specimens of two non-therian (non-tribosphenidan) mammals are described from the Lower Cretaceous Kitadani Formation in the upper part of the Tetori Group, Katsuyama, Fukui Prefecture, Japan. Despite their poor preservation, these specimens represent undescribed species from Japan, suggesting additional mammalian diversity in the Tetori Group. Previously, four mammal taxa had been formally described from this rock unit: a spalacotheriid ‘symmetrodont’, two eobaatarid multituberculates and a eutriconodont mammal. One of the new specimens is a damaged left p4 of a ‘plagiaulacidan’ grade multituberculate assignable to the family Eobaataridae. The Kitadani eobaatarid is a large species distinguished from the two previously described eobaatarids, Tedoribaatar and Hakusanobaatar, which are known from the stratigraphically lower Kuwajima Formation of the Tetori Group, Hakusan, Ishikawa Prefecture, Japan. It also differs from Sinobaatar, Heishanobaatar and Liaobaatar described from the Early Cretaceous of China. Another specimen, a partial right dentary with a faint Meckelian groove, is assigned to a eutriconodontan that is larger than and morphologically distinguishable from the eutriconodont Hakusanodon from the Kuwajima Formation. The Kitadani eutriconodontan is potentially related to the family Triconodontidae. The additional specimens from the Kitadani Formation shed new light on Early Cretaceous mammalian faunal change and dispersal in East Asia.
The vertebrate assemblage from the Early Cretaceous non-marine Xinlong Formation of the Napai Basin, in the south-western part of Guangxi Zhuang Autonomous Region (southern China), is reviewed. The assemblage includes chondrichthyans (at least six species of hybodont sharks including
Hybodus, Thaiodus, Heteroptychodus
and
Acrorhizodus
), actinopterygians (Halecomorphi and Ginglymodi), turtles (the adocid
Shachemys
and the carettochelyid
Kizylkumemys
), crocodilians (cf.
Theriosuchus
) and dinosaurs (the sauropods
Fusuisaurus
and
Liubangosaurus
, carcharodontosaurid and spinosaurid theropods, iguanodontians and a possible psittacosaurid). This assemblage shows many similarities to those from non-marine formations of the Khorat Group of north-eastern Thailand. It seems to be particularly close to that from the Khok Kruat Formation, considered as Aptian in age, as shown especially by sharks and turtles and by the presence of iguanodontians. An Aptian age is therefore proposed for the Xinlong Formation. A study of the stable oxygen and carbon isotope compositions of reptile apatite suggests that this part of South China experienced subtropical arid conditions during the deposition of the Xinlong Formation. In its composition, the vertebrate fauna from the Xinlong Formation seems to be more similar to coeval faunas from SE Asia than to assemblages from northern China (including the Jehol Biota). Although this may partly reflect different depositional and taphonomic environments (fluvial for the Xinlong Formation versus lacustrine for the Jehol Biota) it seems likely that, during Early Cretaceous time, southern China and SE Asia were part of a distinct zoogeographical province, different from that corresponding to northern China. This may be the result of both climatic differences (with relatively cool climates in northern China versus a subtropical climate in the south) and geographical barriers such as mountain chains.
A new basal hadrosauroid, Koshisaurus katsuyama, from the Lower Cretaceous Kitadani Formation in Fukui, central Japan, is reported. The new taxon is distinguished by an autapomorphy and a unique combination of maxillary, vertebral, pubic and femoral characters. A phylogenetic analysis indicates that Koshisaurus is positioned as a basal member of Hadrosauroidea and is more derived than the contemporaneous Fukuisaurus, which is a non-hadrosauroid hadrosauriform. The presence of the antorbital fossa on the maxilla and at least three subsidiary ridges on the labial side of maxillary tooth crown implies that Koshisaurus was among the most basal hadrosauroids. This discovery indicates a higher diversity of hadrosauroids along the eastern margin of the Asian continent in the Early Cretaceous.
A new large-bodied theropod dinosaur, Datanglong guangxiensis gen. et sp. nov., was recovered from the Lower Cretaceous Xinlong Formation of the Datang Basin, Guangxi. It is unique in several features including: posteriormost dorsal vertebra with teardrop-shaped pneumatic foramen confined by enlarged pcdl, acpl and the centrum; posteriormost dorsal with well-developed, horizontal prpl; posteriormost dorsal with a parapophysis projecting more laterally than the diapophysis; brevis fossa shallow with short, ridge-like medial blade; and iliac pubic peduncle with posteroventrally expanded margin. Cladistic analysis supports the idea that this new taxon Datanglong guangxiensis is a primitive member of the Carcharodontosauria in possessing two unambiguous synapomorphies: large external pneumatic foramina and internal spaces present in the lateral surface of ilium, and a peg-and-socket ischiac articulation with the ilium. The presence of the new taxon from Guangxi further confirms that Carcharodontosauria were cosmopolitan large-bodied predators during the Early-mid Cretaceous.
We describe a new basal iguanodont, Proa valdearinnoensis, from the Lower Cretaceous (lower Albian) Escucha Formation of Teruel Province, Spain. The new taxon is known from abundant cranial and postcranial material belonging to several individuals, and is distinguished by an autapomorphy (predentary comes to a point at its rostral margin, with divergent lateral processes) and a unique combination of characters. Proa fills part of an otherwise lengthy temporal gap (early Aptian-Santonian) in the European fossil record of basal iguanodonts. A preliminary phylogenetic analysis places Proa in a polytomy with Iguanodon bernissartensis and more derived iguanodontians (Hadrosauroidea). Proa is more basal than the Valanginian Hypselospinus and late Barremian-early Aptian Mantellisaurus, suggesting a long ghost lineage leading to Proa.
In traditional Linnaean taxonomy, classifications are constructed and maintained principally as dichotomous hierarchies. In phylogenetic taxonomy, such hierarchies are restricted to monophyletic groups defined explicitly on the basis of common ancestry. A definitional configuration termed a node-stem triplet is described that stabilizes the relationship between a given taxon and its subordinate taxa. I outline a rationale within phylogenetic taxonomy for construction of a stable taxonomic framework, as demonstrated by application to the higher-level taxonomy of Dinosauria.
Background
Southwestern Henan Province in central China contains many down-faulted basins, including the Xixia Basin where the Upper Cretaceous continental sediments are well exposed. The Majiacun Formation is a major dinosaur-bearing stratigraphic unit that occurs in this basin.
Methodology/Principal Findings
A new basal hadrosauroid dinosaur, Zhanghenglong yangchengensis gen. et sp. nov., is named based on newly collected specimens from the middle Santonian Majiacun Formation of Zhoujiagou Village, Xixia Basin. Two transitional features between basal hadrosauroids and hadrosaurids are attached to the diagnosis of the new taxon, namely five maxillary foramina consisting of four small scattered ones anteroposteriorly arranged in a row and a large one adjacent to the articular facet for the jugal, and dentary tooth crowns bearing both median and distally offset primary ridges. Zhanghenglong also displays a unique combination of plesiomorphic and derived features of hadrosauroids, and is clearly morphologically transitional between basal hadrosauroids and hadrosaurids. Furthermore, some measurement attributes in osteology are applied to the quantitative analysis of Zhanghenglong. For these attributes, the partition of the dataset on most hadrosauroid species resulting from model-based cluster analysis almost matches taxonomic separation between basal hadrosauroids and hadrosaurids. Data of Zhanghenglong on selected measurement attributes straddle the two combinations of intervals of partitioned datasets respectively related to basal hadrosauroids and hadrosaurids. This condition is similar to mosaic evolution of morphological characters present in the specimens of the taxon. The phylogenetic analysis of Hadrosauroidea recovers a clade composed of Zhanghenglong, Nanyangosaurus, and Hadrosauridae with an unresolved polytomy.
Conclusions/Significance
Zhanghenglong is probably a relatively derived non-hadrosaurid hadrosauroid, based on the inferences made from the morphological comparisons, quantitative evaluation of measurements, and cladistic analysis. In combination with information on the stratigraphy, phylogeny and biogeography, the material of Zhanghenglong provides direct evidence for the hypothesis that hadrosaurids might have originated in Asia.
The origin of hadrosaurid dinosaurs is far from clear, mainly due to the paucity of their early Late Cretaceous close relatives. Compared to numerous Early Cretaceous basal hadrosauroids, which are mainly from Eastern Asia, only six early Late Cretaceous (pre-Campanian) basal hadrosauroids have been found: three from Asia and three from North America.
Here we describe a new hadrosauroid dinosaur, Yunganglong datongensis gen. et sp. nov., from the early Late Cretaceous Zhumapu Formation of Shanxi Province in northern China. The new taxon is represented by an associated but disarticulated partial adult skeleton including the caudodorsal part of the skull. Cladistic analysis and comparative studies show that Yunganglong represents one of the most basal Late Cretaceous hadrosauroids and is diagnosed by a unique combination of features in its skull and femur.
The discovery of Yunganglong adds another record of basal Hadrosauroidea in the early Late Cretaceous, and helps to elucidate the origin and evolution of Hadrosauridae.
The genus Probactrosaurus was first established for material discovered by a joint Russian/Chinese expedition to the Chinese autonomous region of Neimongol (Inner Mongolia). Fossils were collected at a site named Maorty (= Maortu). Material attributable to ornithopod dinosaurs was considered sufficiently distinct to permit the definition of two species of the new genus: Probactrosaurus gobiensis and P. alashanicus. The former species was based on a considerable quantity of skeletal material, much of which is still to be found in the collections of the Palaeontological Institute (PIN), Moscow. The latter was based on far less well-preserved specimens, including a holotype (a posterior skull roof) that can no longer be found in the collections of the PIN and which, along with other materials, was reportedly returned to the Institute of Vertebrate Palaeontology and Palaeoanthropology, Beijing. Some remnants of the original material attributed to P. alashanicus have been located in the PIN collections. Both taxa, established by A. K. Rozhdestvensky, are re-described using all of the available material collected during the early Sino-Soviet expeditions. Probactrosaurus alashanicus is considered to be a junior subjective synonym of P. gobiensis. Further comparisons are made with the recently described species Probactrosaurus mazongshanensis Lu, 1997. The latter does not appear to be referable to the genus Probactrosaurus. Probactrosaurus is a gracile ornithopod (ranging between 4 and 6 m in length). The skull is unadorned by any form of cranial crest; however, the premaxillary beak is deflected ventrally and the dentition is similar to that seen in more derived hadrosaurid ornithopods. The postcranial skeleton is notable for its gracility, in particular the elongate forearm and manus, and the retention of a small, conical pollex spine. Systematic analysis suggests that P. gobiensis is a derived non-hadrosaurid iguanodontian ornithopod and the basal sister-taxon to the clade Hadrosauridae. The phylogeny of currently known iguanodontians is reviewed. © 2002 The Linnean Society of London, Zoological Journal of the Linnean Society, 2002, 136, 113–144.
The right dentary of a new hadrosauroid dinosaur, Penelopognathus weishampeli, has been discovered in the Bayan Gobi Formation (Albian, Lower Cretaceous) of Inner Mongolia (P.R. China). This new taxon is characterised by its elongated, straight dental ramus, whose lateral side is pierced by about 20 irregularly distributed foramina. Its dentary teeth appear more primitive than those of Probactrosaurus, but more advanced than those of Altirhinus, both also from the Lower Cretaceous of the Gobi area. Non-hadrosaurid Hadrosauroidea were already well diversified in eastern Asia by Early Cretaceous time, suggesting an Asian origin for the hadrosauroid clade. To cite this article: P. Godefroit et al., C. R. Palevol 4 (2005).
A nearly complete right dentary originally noted by Mantell in 1848 is redescribed. The specimen, NHMUK 28660, was discovered in a quarry near Cuckfield, West Sussex, from the same formation as the original teeth of Iguanodon anglicus. Fresh examination reveals that NHMUK 28660 exhibits a single autapomorphy (a row of foramina extending from the ventral surface of the symphysis onto the lateral surface of the dentary) and a unique combination of characters that distinguish it from all other iguanodontian dentaries. In light of this and because I. anglicus is regarded as a nomen dubium to which additional material cannot be unambiguously referred, NHMUK 28660 is made the holotype of the new genus and species Kukufeldia tilgatensis.
The holotype of the Mongolian species of ornithopod dinosaur Iguanodon orientalis from the Early Cretaceous (Barremian-Aptian of Khamarin Khural) has been shown to have been established on holotype material that is non-diagnostic, but appears to be closely similar osteologically to the Western European species I. bernissartensis. Additional material collected from the locality known as Khuren Dukh (Dornogov', Mongolia), which had previously been referred to I. orientalis has been re-examined and shown to represent a new genus and species (Altirhinus kurzanovi gen. et sp. nov) of ornithopod dinosaur from the Early Cretaceous (Late Aptian/Early Albian). The anatomy of this new ornithopod is described it shows a number of similarities to the known species of Iguanodon, but also demonstrates features which are in some instances unique to this taxon, while others seem to be either convergent upon or transformational with respect to, the more derived hadrosaurid ornithopods of the Late Cretaceous. Palaeogeographic evidence is corroborative in that it suggests contemporaneous, albeit episodic, links between the Northern Hemisphere landmasses during the Barremian-Albian interval; these explain the appearance of very 'European' large ornithopods (Iguanodan) in Asia in Barremian/Aptian times as a consequence of land-based dispersal. Subsequent isolation of Asia from the European 'domain' during the late Early Cretaceous (Albian) may be responsible for the appearance of derived forms such as Altirhinus, and is suggestive of an Asian centre of origin for the family Hadrosauridae in middle Cretaceous times; this contradicts an earlier vicariance-biogeographic model of ornithopod evolution. The cranial anatomical modifications seen in this new taxon: vertical expansion of the dorsal nasal cavity, lateral expansion and lowering of the cropping beak relative to the jaw line, increase in the number of replacement teeth (but no significant miniaturization of the crowns) and the trend toward formation of a more integrated battery of cheek teeth, seen to var)ring degrees in several mid-Cretaceous ornithopods are commented upon; they can be interpreted within the context of an evolutionary trend culminating in the cranial complexity seen in the terminal lineage of ornithopods represented by the Late Cretaceous Hadrosauridae. Functionally, some of th;se changes can be correlated with what can be interpreted as 'improvements' to the efficiency of food gathering and processing which might represent increased niche partitioning and/or responses to increasingly tough and abrasive (xeric adapted) foliage; others, notably the modifications to the nasal cavity (perhaps associated with providing space for a countercurrent moisture conserving turbinal system), are suggestive of a biological response to increasingly seasonal/xeric conditions in the middle of the Cretaceous Period or changes in the floral composition of these times. (C) 1998 The Linnean Society of London.
Dinosaur jaw remains from the Early Cretaceous Khok Kruat Formation of northeastern Thailand, including a well-preserved dentary and a maxilla fragment, are described as belonging to a new species of the primitive ceratopian Psittacosaurus, P. sattayaraki. It differs from previously described species of Psittacosaurus from Mongolia and China in the morphology of its dentary. The Khok Kruat Formation is referred to the Aptian-Albian on the basis of palaeontological evidence, and this supports the hypothesis that faunal assemblages containing Psittacosaurus in other parts of Asia are late Early Cretaceous in age. This occurrence in the Early Cretaceous of the Indochina Block indicates that by that time the microcontinent had become accreted to mainland Asia. -Authors
Approximately half of existing dinosaur species belonging to the Order Ornithischia, or the 'bird-hipped' dinosaurs, which include such familiar forms as the stegosaurs, ankylosaurs, hadrosaurs, and ceratopsids. Although ornithischians are generally conceded to have descended from a common ancestor, little is known about the pattern of descent. Comparison of more recently discovered ornithischian fossils from China and Mongolia to better-known North American forms has shed light on the pattern of evolutionary diversification among ornithischians, a pattern that began approximately 200 My ago and ended abruptly nearly 140 My later at the end of the Cretaceous.-from Author
A new basal hadrosauroid, Koshisaurus katsuyama, from the Lower Cretaceous Kitadani Formation in Fukui, central Japan, is reported. The new taxon is distinguished by an autapomorphy and a unique combination of maxillary, vertebral, pubic and femoral characters. A phylogenetic analysis indicates that Koshisaurus is positioned as a basal member of Hadrosauroidea and is more derived than the contemporaneous Fukuisaurus, which is a non-hadrosauroid hadrosauriform. The presence of the antorbital fossa on the maxilla and at least three subsidiary ridges on the labial side of maxillary tooth crown implies that Koshisaurus was among the most basal hadrosauroids. This discovery indicates a higher diversity of hadrosauroids along the eastern margin of the Asian continent in the Early Cretaceous.
The history of discovery and interpretation of several dinosaurs collected from quarries near the town of Hastings during the latter half of the 19th century is more complicated than it should be. Samuel Husbands Beckles and Charles Dawson collected several large ornithopod skeletons from this area, but just a few bones from these skeletons were subsequently described and interpreted (principally) by Richard Owen and Richard Lydekker. All these specimens merited recognition because they had the potential to contribute to an on-going debate about the anatomical structure and relationships of the iconic Wealden dinosaur Iguanodon. Unfortunately, no detailed description of these important skeletons was published in later years. Furthermore, previously known associations of bones and even provenance information, linked to the specimens that were gradually acquired by the Natural History Museum, are unclear. Confusion may have arisen because Richard Lydekker used the private collector Charles Dawson as a voluntary curatorial assistant. This account documents the past work on the osteology of material that can be attributed to Hypselospinus fittoni. Nearly all such material is described here for the first time, and every effort has been made to re-establish associations between bones as well as provenance information. A skeletal reconstruction of Hypselospinus is attempted on the basis of the hypodigm. Most of the on-going confusion concerning the affinity of this material with either Hy. fittoni or its sympatric contemporary Barilium dawsoni has been resolved. Hypselospinus fittoni (Lydekker, 1889) is rediagnosed on the basis of this new and relatively comprehensive anatomical description, and this animal is compared with known contemporary and closely related taxa. Some recently published accounts claiming to be revisions of the taxonomy of Wealden ‘iguanodonts’, including material belonging to the hypodigm of Hy. fittoni, have failed to adhere to basic taxonomic principles and have caused more confusion than was strictly necessary. The systematic position of Hypselospinus is reassessed cladistically. The cladistic analysis forms the basis for a revised hierarchical classification of derived ornithopods. The consensus topology generated by the systematic analysis has been used to explore the phylogenetic history of these dinosaurs and create an internally consistent classificatory hierarchy (phylogenetic definitions and Linnaean diagnoses are given for critical positions in the topology). This analysis suggests that there is a fundamental split amongst the more derived (clypeodontan) ornithopod ornithischians into the clades Hypsilophodontia and Iguanodontia. There is evidence for anatomical parallelism and convergence (homoplasy) particularly between large-bodied representatives of both clades. Hypselospinus is one of the earliest known styracosternan iguanodontians and displays anatomical characteristics that presage the evolution of the extraordinarily abundant and diverse hadrosaurs of the latest Cretaceous (Campanian−Maastrichtian). These observations cast fresh light on the phylogeny, classification, diversity, and biology of derived ornithopods. There is little doubt that Hy. fittoni could have been understood far better more than a century ago. That this statement is undoubtedly true is reflected in the century of doubt and confusion that has surrounded this taxon and its original incarnation as Iguanodon fittoni. © 2014 The Linnean Society of London
The main features of the phylogeny program TNT are discussed. Windows versions have a menu interface, while Macintosh and Linux versions are command-driven. The program can analyze data sets with discrete (additive, non-additive, step-matrix) as well as continuous ...
After more than ten years of Thai-French research, the Thai dinosaur record, from the continental rocks of the Khorat Plateau, is, to date, the best in Southeast Asia. The oldest evidence consists of footprints of small dinosaurs from the Middle to Late Jurassic Phra Wihan Formation. The most varied dinosaur assemblage hitherto found in Thailand comes from the Late Jurassic Sao Khua Formation; it is dominated by sauropods, but also includes various theropods. Large theropod footprints are known from the Early Cretaceous Phu Phan Formation. Theropods and the primitive ceratopsian Psittacosaurus occur in the Aptian-Albian Khok Kruat Formation.
Protohadros byrdi, gen. et sp. nov., from the Cenomanian Woodbine Formation, Texas, is described on the basis of a disarticulated skull and isolated postcrania. The possession of the fewest synapomorphies among hadrosaurids places Protohadros at the basal position within Hadrosauridae. The combination of a derived maxillopalatal unit and a primitive quadrate indicate a level of cranial kinesis intermediate between primitive iguanodontians and other hadrosaurids. Both the phylogenetic and chronological distributions of these characteristics describe an evolutionary sequence of adaptations in which modifications for increased masticatory ability of the maxillary region precede the evolution of both streptostylic cranial kinesis and a more derived mandible in Hadrosauridae. The taxon is unique among hadrosaurids in possessing a ventrally deflected muzzle, including a deep, rostrally massive mandible, that is interpreted to represent an exclusively low-browsing pattern of food acquisition in a deltaic environment. At 95 Ma, Protohadros is the oldest definitive hadrosaurid. This plus the phylogenetic and biogeographic position of the specimen indicate that a North American origin of Hadrosauridae is equally as likely as the prevalent Asian origin hypothesis.
Dinosaurian biogeography may have been largely controlled by the Mesozoic fragmentation of Pangea and the reassembly of its fragments into a new, boreal supercontinent (Laurasia). Although Late Triassic and Early Jurassic dinosaurs were globally distributed, Chinese assemblages were dominated by endemic forms from Middle Jurassic into Early Cretaceous time. The affinities of Aptian - Albian immigrants to Asia were strongest with North America and Europe rather than Gondwana, indicating that the northern and southern hemispheres had by then attained their biogeographic identity. This distinctiveness was maintained through Cretaceous time. Europe seems to have been a buffer area between Paleolaurasia and Gondwana; of the northern continents it was the most strongly influenced by Gondwana dispersants. Late Jurassic dinosaur assemblages in North America exhibited Gondwana affinities, but by Late Cretaceous time they were dominated by forms of Asian ancestry.
A new taxon of ornithopod dinosaur is described as Siamodon nimngami nov. gen, nov. sep., on the basis of a well-preserved maxilla from the Khok Kruat Formation (Aptian) of northeastern Thailand. An isolated tooth and a braincase are referred to this taxon, and the status of other ornithopod specimens from Thailand and Laos is discussed. S. nimngami nov. gen, nov. sep. is considered as an advanced iguanodontian, apparently close to Probactrosaurus, from which it differs by various characters of the maxilla. Siamodon is an addition to the already long list of advanced iguanodontian taxa from the late Early Cretaceous of Asia. The diversity and abundance of these forms may suggest that advanced iguanodontians first appeared in Asia, before spreading to other parts of the world.
New palynological results are presented and integrated with previous data for the Mesozoic Khorat Group continental red bed succession of NE Thailand. The Khorat Group is traditionally considered to comprise, from bottom to top, the Nam Phong, Phu Kradung, Phra Wihan, Sao Khua, Phu Phan and Khok Kruat Formations. The group is unconformably overlain by the continental evaporitic Maha Sarakham Formation, which has been palynologically dated as mid-Albian-Cenomanian, therefore giving a minimum age for the underlying Khorat Group. Traditionally the Nam Phong Formation is considered to be Late Triassic, the Phu Kradung, Phra Wihan and Sao Khua Formations are assigned to the Jurassic, and the Phu Phan and Khok Kruat Formations to the Early Cretaceous. This age dating has mainly been based on plant macrofossil and vertebrate studies. Palynology supports the Late Triassic age for the Lower Nam Phong and underlying Huai Hin Lat Formations but suggests an Early Cretaceous (Berriasian-Barremian) age for the Phu Kradung, Sao Khua and Phra Wihan Formations, and an Aptian age for the Khok Kruat Formation. The Phu Phan has yet to yield useful age-diagnostic palynomorphs but must also be Early Cretaceous based on the age of the under- and overlying formations. The key palynomorph present for ascribing an Early Cretaceous age is Dicheiropollis etruscus, a taxon that is restricted to this age interval and has been found in the Phu Kradung (both at outcrop and in subsurface exploration wells), Phra Wihan and Sao Khua Formations. The lithostratigraphy and age of the Nam Phong Formation is, at present, still problematic. From subsurface seismic data it is clear that the Nam Phong Formation comprises two distinct units separated by an unconformity, referred to herein as the Lower and Upper Nam Phong Formations. The age of the Lower Nam Phong Formation based on palynology is Late Triassic (Rhaetian) whereas the age of the Upper Nam Phong Formation is poorly constrained but can be no older than Pliensbachian based on data from the Phu Horm-1 well. The absence of the Early Cretaceous marker D. etruscus may be taken as indirect evidence for a Jurassic age for the Upper Nam Phong Formation in the Phu Horm-1 well. This revised age dating suggests the presence of a significant depositional hiatus within the Nam Phong Formation, and consequently the Lower Nam Phong Formation should be removed from the Khorat Group. Overall the palynomorph assemblages of the Khorat Group are dominated by the gymnosperm pollen Corollina (synonymous with Classopollis) and Dicheiropollis, both of which belong to the Cheirolepidaceae and would indicate deposition in a warm, dominantly seasonally dry subtropical climate.
New geological data are presented and previously published information is reviewed to demonstrate that much of the Khorat Group (Phu Kradung to Khok Kruat Formations) of NE Thailand is Early Cretaceous in age. It is suggested that the Mesozoic red bed sequences of neighbouring Indochina are likely to be of similar age rather than spanning the entire Late Triassic to Early Cretaceous as previously assumed. Moreover, the Lower Nam Phong Formation dated as Late Triassic and previously included as the basal formation of the Khorat Group is now removed from this group, thus creating a hiatus within the Jurassic. There is therefore no clear relationship between the Indosinian Orogeny and the Triassic collision of the Sibumasu (also referred to as Shan-Thai) and Indochina Blocks and the subsequent deposition of the Khorat Group in a Late Triassic-Early Cretaceous thermal sag basin. It is now proposed that much of the sequence was deposited during the Late Jurassic-Early Cretaceous. Jurassic sediments may be absent across much of the Khorat Plateau whereas marine Jurassic sediments to the west and east show no sediments younger than Bajocian. Because sea levels were generally rising in the Middle and Late Jurassic it is likely that the Khorat region was uplifted at this time. It is suggested that the Khorat Group was originally deposited in a foreland basin setting rather than a thermal sag basin following Late Triassic rifting. Moreover, the original site of deposition was to the north in southern China, with the present-day location being the result of movement along the Red River Fault coupled with a clockwise rotation of the Indochina Block (on which the Khorat Group sits) with respect to the South China Block.
Abstract The Tibetan Plateau is a key factor in controlling the present-day climate and atmospheric circulation pattern in Asia. The pattern of atmospheric circulation after the uplift of the plateau is well known, whereas direct evidence is lacking regarding the nature of the circulation pattern prior to the uplift. The distribution of desert directly reflects the position of the subtropical high-pressure belt, and the prevailing surface-wind pattern recorded in desert deposits reveals the position of its divergence axis. Cretaceous eolian sandstone of the Phu Thok Formation is extensively exposed in the northern Khorat Basin, northeastern Thailand. We conducted a sedimentological study on this formation to reconstruct temporal changes in the latitude of the subtropical high-pressure belt in low-latitude Asia during the Cretaceous. Spatio-temporal changes in the paleo-wind directions recorded in the Phu Thok Formation reveal that the Khorat Basin mainly belonged to the northeast trade wind belt and subtropical high-pressure belt was situated to the north of the Khorat Basin during the initial stages of deposition, shifted southward to immediately above the basin during the main phase of deposition, and then shifted northward again to the north of the basin during the final stages of deposition. The paleomagnetic polarity sequence obtained for the Phu Thok Formation comprises three zones of normal polarity and two of reversed polarity, correlating to chrons M1n to C34n of the geomagnetic polarity time scale. This result suggests that the Phu Thok Formation is mid-Cretaceous in age (from c. 126 Ma to c. 99–93 Ma), similar to the age of eolian sandstone in the Sichuan Basin, southern China (the Jiaguan Formation). These results, in combination with paleo-wind direction data, suggest the development of low-latitude desert and an equatorward shift of the subtropical high-pressure belt (relative to the present-day) in Asia during the mid-Cretaceous.
Three classifications of the Dinosauria have been proposed, which differ from each other in the principles on which their authors proposed to make the divisions. First in time is Professor Cope’s classification (‘Philadelphia, Acad. Nat. Sci. Proc.,’ November 13th, 1866, and December 31st, 1867; ‘Amer. Phil. Soc. Trans.,’ vol. 14, Part I). He relied upon the characters of the tarsus and the ilium; and on their varied condition divided Dinosaurs into three orders named Orthopoda, Goniopoda, and Symphopoda. In the Orthopoda , the generic types associated are Scelidosaurus, Hylæosaurus, Iguanodon, and Hadrosaurus. And in this group the relations of the tibia and fibula are compared to those of modern Lizards, the proximal tarsals being distinct from each other and from the tibia. The ilium has a narrowed anterior prolongation.
A ponderously constructed ornithischian dinosaur, Lurdusaurus arenatus, nov.g., nov.sp., from the Aptian of Niger resembles extinct giant ground sloths in general body form. Details of its skeletal anatomy indicate a close affinity to European iguanodontids of Early Cretaceous age.
The holotype of the Mongolian species of ornithopod dinosaurIguanodon orientalisfrom the Early Cretaceous (Barremian-Aptian of Khamarin Khural) has been shown to have been established on holotype material that is non-diagnostic, but appears to be closely similar osteologically to the Western European speciesI. bernissartensis. Additional material collected from the locality known as Khuren Dukh (Dornogov′, Mongolia), which had previously been referred toI. orientalishas been re-examined and shown to represent a new genus and species (Altirhinus kurzanovigen.etsp. nov) of ornithopod dinosaur from the Early Cretaceous (Late Aptian/Early Albian). The anatomy of this new ornithopod is described; it shows a number of similarities to the known species ofIguanodon, but also demonstrates features which are in some instances unique to this taxon, while others seem to be either convergent upon, or transformational with respect to, the more derived hadrosaurid ornithopods of the Late Cretaceous. Palaeogeographic evidence is corroborative in that it suggests contemporaneous, albeit episodic, links between the Northern Hemisphere landmasses during the Barremian-Albian interval; these explain the appearance of very ‘European’ large ornithopods (Iguanodon) in Asia in Barremian/Aptian times as a consequence of land-based dispersal. Subsequent isolation of Asia from the European ‘domain’ during the late Early Cretaceous (Albian) may be responsible for the appearance of derived forms such asAltirhinus, and is suggestive of an Asian centre of origin for the family Hadrosauridae in middle Cretaceous times; this contradicts an earlier vicariance-biogeographic model of ornithopod evolution. The cranial anatomical modifications seen in this new taxon: vertical expansion of the dorsal nasal cavity, lateral expansion and lowering of the cropping beak relative to the jaw line, increase in the number of replacement teeth (but no significant miniaturization of the crowns) and the trend toward formation of a more integrated battery of cheek teeth, seen to varying degrees in several mid-Cretaceous ornithopods are commented upon; they can be interpreted within the context of an evolutionary trend culminating in the cranial complexity seen in the terminal lineage of ornithopods represented by the Late Cretaceous Hadrosauridae. Functionally, some of these changes can be correlated with what can be interpreted as ‘improvements’ to the efficiency of food gathering and processing which might represent increased niche partitioning and/or responses to increasingly tough and abrasive (xeric adapted) foliage; others, notably the modifications to the nasal cavity (perhaps associated with providing space for a counter-current moisture conserving turbinal system), are suggestive of a biological response to increasingly seasonal/xeric conditions in the middle of the Cretaceous Period or changes in the floral composition of these times.
