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Cervical vertebra of Yunganglong datongensis (SXMG V 00001). (A)-Cranial view. (B)-Right lateral view. (C)-Dorsal view. (D)-Caudal view. (E)-Left lateral view. (F)-Ventral view. Abbreviations: dia, diapophysis; par, parapophysis; poz, postzygapophysis; prz, prezygapophysis. Scale bar = 6 cm. doi:10.1371/journal.pone.0077058.g004 

Cervical vertebra of Yunganglong datongensis (SXMG V 00001). (A)-Cranial view. (B)-Right lateral view. (C)-Dorsal view. (D)-Caudal view. (E)-Left lateral view. (F)-Ventral view. Abbreviations: dia, diapophysis; par, parapophysis; poz, postzygapophysis; prz, prezygapophysis. Scale bar = 6 cm. doi:10.1371/journal.pone.0077058.g004 

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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 Ameri...

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... and vertical pendent portions of the paroccipital processes are set caudal to the occipital condyle, with their ventral tips slightly below the ventral edge of the occipital condyle. The occipital condyle is formed by the basioccipital and describes a crescent in caudal view. Its caudal surface is vertical and slightly bulging, while its ventral surface is strongly convex. The surface is generally smooth, and one groove is visible on the left half of the caudal surface (Fig. 2C). A short neck divides the occipital condyle and the basal tubera. The basal tubera seem to be formed more by the basisphenoid than by the basioccipital, and those two bones are well fused to each other. The basal tubera are separated by a longitudinal median recess, and a delicate ridge appears along the midline. A round craniolaterally facing fossa exists on the cranial surface of each side of the basal tubera. The braincase is broken along a line through the exits of the cranial nerves. The positions of these cranial nerve exits are conventional compared to other hadrosauroids, and generally correspond to those in closely related taxa, such as Levnesovia . Three foramina pierce the fused opisthotic and exoccipital laterally for cranial nerves X-XII. The rostral two foramina for cranial nerves X and XI are merged, giving a larger appearance than the caudal one for cranial nerve XII. The auditory recess, which includes the fenestra vestibule (fenestra ovalis of [6]), exit for cranial nerve IX, and foramen for the jugular vein, is bounded by the fused basisphenoid and parasphenoid ventrally, the prootic dorsally, and the fused opisthotic and exoccipital caudally. Rostral to the auditory recess is the large, round trigeminal foramen. Two cervicals (ZY007-40, -41) are preserved, and ZY007-40 is almost complete (Fig. 4). The centrum is strongly opisthocoelous, with the round cranial articular condyle more than half the length of the centrum. The cranial-most protruding point is above the midlevel of the centrum. The caudal articular surface is deeply concave and elliptical in caudal view, being wider than high. The lateral side of the centrum is slightly higher than long, and is divided by a midlevel ridge into dorsal and ventral depressions. The large parapophysis occupies the cranial half of this ridge. The ventral surface is slightly convex, especially at the caudal half. The neural canal is large and round, about half the height of the centrum. The prezygapophysis starts from the dorsolateral corner of the cranial half of the neural arch and does not protrude beyond the cranial edge of the articular condyle. The dorsomedially facing smooth articular facet is large, oval, and flat. The short stem of the prezygapophysis also gives rise to the diapophysis, which projects caudoventrolaterally. The robust postzygapophysis is directed more caudally than laterally, with its entire articular facet beyond the caudal edge of the centrum. The neural spine is not well preserved, but seems to have been delicate. A partial dorsal neural arch and neural spine are preserved (ZY007-36) (Fig. 5A, B). The diapophysis projects dorsolaterally and slightly caudally and has a triangular cross section. The long, oval, and flat postzygapophysis articular facet faces lateroventrally. Only the basal portion of the neural spine is preserved; it is plate- like and thin transversely. One proximal (ZY007-27) (Fig. 5 C, E) and one middle (ZY007- 19) (Fig. 5 D, F) caudal are preserved. The proximal caudal’s centrum is narrow and slightly amphicoelous. The articular surfaces are elliptical with relatively narrow ventral ends. The partial right transverse process starts at the neurocentral junction and projects laterally. The neural spine is tall, almost double the height of the centrum. The cross section of the neural spine is rectangular, with the transverse width less than half the longitudinal length. The tip of the neural spine expands slightly. The centrum of the middle caudal is dorsoventrally lower but proximodistally longer than that of the proximal caudal, with hexagonal articular surfaces. The transverse process is not present, and the neural spine projects caudodorsally. The distal portions of both ischia are preserved (ZY007-11 left, - 12 right) (Fig. 6). The preserved shaft is triangular in cross section, with a flat medial surface to contact its counterpart. This flat surface continues to the distal end. The craniolateral surface bears a shallow longitudinal depression, while the caudolateral surface is flat. The distal end slightly expands craniolaterally to form a hemispherical expansion. The expanded distal end is about double the width of the shaft diameter. The distal end of the left femur is preserved (ZY007-32). The cross section of the preserved proximal end of the shaft is elliptical, and its transverse width is twice its craniocaudal width. The intercondylar extensor groove of the femur is deep, U-shaped, partially enclosed by expansion of medial and lateral condyles. The medial condyle is slightly larger than the lateral. The medial surface of the medial condyle is flat, while the lateral surface of the lateral condyle bears a stout longitudinal ridge. The caudal condyles are strongly developed, fan-shaped, and longer proximodistally than craniocaudally in lateral and medial views. In caudal view, the medial condyle is more expanded than the lateral, about three times wider transversely. On the lateral surface of the medial condyle, a small longitudinal ridge develops close to the shaft (Fig. 7D). The proximal portion of the right tibia (ZY007-1) (Fig. 8 A–F) and the distal portion of the left tibia with astragalus (ZY007-2) (Fig. 8 G–K) are preserved. The cnemial crest is well developed and protrudes craniolaterally. Two laterally-projecting condyles exist on the caudal half of the proximal end. The midshaft is ovate in cross section. The distal end of the left tibia is articulated with the astragalus. In cranial view, the astragalus is triangular, with a clear short ascending process. In caudal view, the astragalus is also triangular, with a delicate ascending process at its proximolateral corner. Phylogenetic analysis recovered 303 MPTs (most parsimonious trees) of 294 steps, with a CI (consistency index) of 0.534 and a RI (retention index) of 0.858. The strict consensus tree recovered Yunganglong , Jintasaurus , Protohadros , Nanyangosaurus , Shuangmiaosaurus , Levnesovia , Bactrosaurus , Tanius , and Telmatosaurus in an unresolved polytomy between Probactrosaurus and ( Aralosaurus + Hadrosauridae) with poor bootstrap frequencies and bremer supports (Fig. 9). In the strict consensus tree, the Hadrosauroidea clade is supported by 7 unambiguous synapomorphies (40[1], parietal sagittal crest long, more than 2/3 ...

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... The morphology of the anterior caudal vertebrae of CMP-MS-04 resembles those of Iguanodon bernissartensis in having caudal centra that are platycoelus and parallel-sided neural spines ( Figure 4B). In contrast, the anterior caudal centra of Barilium dawsoni and Mantellisaurus atherfieldensis are amphyplatyan, whereas, in Jinzhousaurus yangi, Ouranosaurus nigerensis and Yunganglong datongensis [34], the centra are amphicoelus. ...
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Iguanodon bernissartensis is the most frequently and widely cited styracosternan ornithopod in Western Europe during the Early Cretaceous, although some of these assignments likely need to be revised to establish the true distribution of the taxon. Here, we describe a new specimen of I. bernissartensis from the upper Barremian of the Iberian Peninsula. Based on the unique combination of shared characters, the new specimen from the Arcillas de Morella Formation at Morella locality (Castellón, Spain) can be confidently referred to Iguanodon bernissartensis. These characters include parallel-sided anterior and posterior margins of the dorsal and the caudal neural spines as well as the presence of a ventral keel in the posterior dorsal centra and a broad ventral sulcus in the midline of the central surface of the most posterior sacral vertebrae. This new evidence of Iguanodon bernissartensis reinforces the knowledge about styracosternan ornithopods as the most frequently recorded dinosaur group in the Arcillas de Morella Formation.
... Remarks: We place these specimens in Candona declivis according to Ye et al. (2002): small shell, trapezoidal lateral view, upper posterior margin considerably inclined towards posterior end, narrow and round lower posterior margin, round anterior margin and smooth surface. This species has been reported from the Cretaceous-Paleogene deposits in China including the Sifangtai Formation (Campanian) and the Mingshui Formation (upper Campanian-Danian) in the Songliao Basin, the Zuoyun Foramtion (upper Lower Cretaceous) and Zhumapu Formation (lower Upper Cretaceous) in Shanxi Province, the Dalangshan Formation (Upper Cretaceous-?Paleocene) and the Sanshui Formation (Upper Cretaceous) in Guangdong Province, the Funing Group (Paleocene) in Jiangsu Province, and the lower Jiaozhou Formation (Campanian-Maastrichtian) in the Jiaolai Basin(Hou et al., 2002;Ye et al., 2002;Zhang, W.T. et al., 2003;Qu et al., 2014;Wang et al., 2013;Wang et al., 2019). ...
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... Two species seem to have similar structures. The only specimen of Yanganglong (Wang et al., 2013) is badly eroded, yet there exists two prominent bulges symmetrically placed about the dorsal margin of the supraoccipital. No overlapping extension is seen on this specimen, however, such overlap is seen on Jintasaurus (You & Li, 2009, fig. ...
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... The basioccipital participates in the rostral portion of the sphenooccipital tubercles (or basal tubera) (Figure 15(E), (G)). A ridge extends between both sphenooccipital tubercles in Jintasaurus ( You & Li 2009), Eolambia (McDonald et al. 2012b), and Yunganglong ( Wang et al. 2013), unlike in MPG-SCH-3. As already noted by Sanz et al. (1984), the sphenooccipital tuber- cles are small and underdeveloped compared with those of Lurdusaurus (Taquet & Russell 1999), Ouranosaurus (Taquet 1976), Eolambia (McDonald et al. 2012b), and Telmatosaurus (Nopcsa 1900), more closely resembling the smaller tubercles in I. bernissartensis (Norman 1980), Mantellisaurus (Norman 1986), and Bactrosaurus ( Godefroit et al. 1998). ...
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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).
... No other scientific works have been dedicated to the description of this taxon since 1976, although a few papers referred to it (Rasmussen, 1998;Dean-Carpentier, 2008;Taquet, 2012). Despite the difficulty of gaining access to study the original holotype material, it is always included in cladistic analyses of iguanodontian dinosaurs (e.g.,Sereno, 1986;Norman, 2004;Norman, 2015;McDonald, Barrett & Chapman, 2010;McDonald, Wolfe & Kirkl, 2010;McDonald et al., 2012b;Wang et al., 2013;Tsogtbaatar et al., 2014). Since 1975, a nearly complete mounted skeleton of O. nigeriensis has been exhibited at the Museo di Storia Naturale (Natural History Museum) of Venice, Italy. ...
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... Camptosaurus dispar was designated as the outgroup. The components of the revised analysis are available as Supporting Information files (S1 and S2 Spreadsheets, S1 Document and S1 File). the rostral and caudal margins); ventral margin of maxillary tooth row concave in lateral view (also in Iguanacolossus [4], Dakotadon (SDSM 8656) [66], Fukuisaurus [60], Iguanodon [61], Mantellisaurus (NHMUK R5764) [62], Proa [41], Ouranosaurus [59], Altirhinus [67], Equijubus [68], Probactrosaurus [65], Shuangmiaosaurus [11], and Zhanghenglong [16], but different from Bolong [63], Xuwulong [69], Siamodon [70], Protohadros [21], and Jeyawati [22], in which it is straight); dentary teeth with a primary ridge and single mesial accessory ridge (present in holotype CEUM 9758; also in Protohadros [21], Levnesovia [13] Tethyshadros [71], Huehuecanauhtlus [23], Zhanghenglong [16], and some specimens of Bactrosaurus [72]); straight shaft of ischium (also in Uteodon [26,73], Mantellisaurus (IRSNB 1551, NHMUK R3741), Bolong [63], Altirhinus [67], Bactrosaurus [72], Gilmoreosaurus [74], and Yunganglong [15]); straight distal half of femoral shaft (also in Hypselospinus (NHMUK R1629 [58]), Iguanodon [61], Proa [41], Ouranosaurus [59], Gongpoquansaurus [75,76], Nanyangosaurus [9], Bactrosaurus [72], Gilmoreosaurus [74], Tanius [77], and Tethyshadros [71]); dorsally-directed flange along the dorsal margin of the ilium, extending from above the acetabulum to the postacetabular process (also in hadrosauroid material from the Lewisville Member of the Woodbine Formation of Texas [78]). ...
... The centrum of the caudal cervical vertebra is strongly opisthocoelous, with the cranial surface forming a hemispherical bulge and the caudal surface a deep concavity (Fig 2F-2H); this morphology is present in many styracosternans, including Hippodraco [4], Lurdusaurus [79], Lanzhousaurus [80], Barilium [81], Hypselospinus [58], Iguanodon [61], Mantellisaurus [62], Ouranosaurus [59], Jinzhousaurus [82], Bolong [63], Equijubus [68], Probactrosaurus [65], Jeyawati [22], Bactrosaurus [72], Gilmoreosaurus [74], Tanius [77], Huehuecanauhtlus [23], Yunganglong [15], Claosaurus [83], and hadrosaurids [7]. The right lateral surface of the centrum is damaged and the left is missing, precluding description of the parapophyses. ...
... The proximal end is craniocaudally expanded; however, the iliac and pubic peduncles are missing and only the base of the obturator process is present. The shaft is straight, as in the dryosaurid Valdosaurus [42], Uteodon [26,73], Mantellisaurus (IRSNB 1551, NHMUK R3741) [62], Altirhinus [67], Bolong [63], Bactrosaurus [72], Gilmoreosaurus [74], and Yunganglong [15]. The distal end of the ischium is a cranially-expanded boot (Fig 9H). ...
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... Therefore, Datonglong does not belong to Hadrosauridae, and our comparison will focus on nonhadrosaurid hadrosauroids, especially those from the Late Cretaceous of China. Based onWang et al. (2013),Xing et al. (2014), andTsogtbaatar et al. (2014), 15 Late Cretaceous nonhadrosaurid hadrosauroid genera have been reported, with eight from China (recovered from the Upper Cretaceous red beds of Guangxi in southern China, was originally reported as a lambeosaurine hadrosaurid ...
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A new non-hadrosaurid hadrosauroid dinosaur (Datonglong tianzhenensis gen. et sp. nov.) is reported. The new taxon is recovered from the Upper Cretaceous Huiquanpu Formation of Tianzhen County, Shanxi Province in northern China, and represented by an almost complete right dentary with dentition. Different from all other hadrosauroids, Datonglong possesses two functional teeth in each alveolus, and the pattern of ridge development on the lingual surface of its dentary crown shows a unique combination of character states (for example: distally offset primary ridge; well-developed secondary ridge; no additional ridge(s); slightly distally curved apical half of primary ridge). Comparative studies indicate advanced non-hadrosaurid hadrosauroids experienced a complex pattern in the evolution of their dentary, especially dentary dentition. Derived hadrosaurid features occurred frequently in these taxa, such as high height/width ratio of tooth crown in Bactrosaurus, one primary and one faint ridges in Gilmoreosaurus, median placed primary ridge in Zhanghenglong, rostrally inclined coronoid process in Nanningosaurus, and two functional teeth in each alveolus in Datonglong. This implies incredible diversities and attempts close to the origin of Hadrosauridae and difficulties to elucidate their phylogenetic relationships.
... Therefore, Datonglong does not belong to Hadrosauridae, and our comparison will focus on nonhadrosaurid hadrosauroids, especially those from the Late Cretaceous of China. Based on Wang et al. (2013), Xing et al. (2014), and Tsogtbaatar et al. (2014 , 15 Late Cretaceous nonhadrosaurid hadrosauroid genera have been reported, with eight from China (Tanius Wiman, 1929; Bactrosaurus Gilmore, 1933; Gilmoreosaurus Brett-Surman, 1979; Nanyangosaurus Xu et al., 2000; Shuangmiaosaurus You et al., 2003; Nanningosaurus Mo et al., 2007; Yunganglong Wang et al., 2013; Zhanghenglong Xing et al., 2014), three from North America (Claosaurus Marsh, 1890 ; Eolambia Kirkland, 1998; Protohadros Head, 1998), two from Europe (Telmatosaurus Nopcsa, 1903; Tethyshadros Dalla Vecchia, 2009), one from Central Asia (Levnesovia Sues & Averianov, 2009), and one from Mongolia (Plesiohadros Tsogtbaatar et al., 2014). Among these eight Chinese taxa, three (Tanius, Nanyangosaurus, and Yunganglong) do not preserve comparable parts with Datonglong. ...
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A new non-hadrosaurid hadrosauroid dinosaur (Datonglong tianzhenensis gen. et sp. nov.) is reported. The new taxon is recovered from the Upper Cretaceous Huiquanpu Formation of Tianzhen County, Shanxi Province in northern China, and represented by an almost complete right dentary with dentition. Different from all other hadrosauroids, Datonglong possesses two functional teeth in each alveolus, and the pattern of ridge development on the lingual surface of its dentary crown shows a unique combination of character states (for example: distally offset primary ridge; well-developed secondary ridge; no additional ridge(s); slightly distally curved apical half of primary ridge). Comparative studies indicate advanced non-hadrosaurid hadrosauroids experienced a complex pattern in the evolution of their dentary, especially dentary dentition. Derived hadrosaurid features occurred frequently in these taxa, such as high height/width ratio of tooth crown in Bactrosaurus, one primary and one faint ridges in Gilmoreosaurus, median placed primary ridge in Zhanghenglong, rostrally inclined coronoid process in Nanningosaurus, and two functional teeth in each alveolus in Datonglong. This implies incredible diversities and attempts close to the origin of Hadrosauridae and difficulties to elucidate their phylogenetic relationships.
... 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]. ...
... The configuration of the supratemporal fenestra is varied in iguanodontians (Fig 13). The rostrocaudally elongated oval-shaped supratemporal fenestra of Sirindhorna (Fig 13A and 13B) is similar to that in Mantellisaurus [38], Proa [44], Probactrosaurus [5] and Levnesovia [12], but different from the rostrolaterally directed oval-shaped supratemporal fenestra in Lurdusaurus arenatus [45], Ouranosaurus nigeriensis [46], Equijubus [47], Jinzhousaurus [48], Xuwulong [11], Jintasaurus [8] and possibly in Yunganglong [1], and the transversely wide one in Gongpoquansaurus [40]. However, the transversely straight frontoparietal sutural line of Sirindhorna is exceptional among those non-hadrosaurid styracosternans that having a "V"-shaped or rostrally excavated frontoparietal sutural line at the center (Fig 13). ...
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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 the oldest age of the Late Cretaceous (Cenomanian), one Asian (Yunganglong) and two North American (Eolambia and Protohadros) basal hadrosauroids have been discovered (Head 1998; Kirkland 1998; Wang et al. 2013). Here, we report a new taxon, Zuoyunlong huangi gen. ...
... Each MPT has a length of 1019 steps, a consistency index of 0.484 and a retention index of 0.855. The strict consensus of Ischium is the only overlapping element of Yunganglong and Zuoyunlong, both from the same locality and horizon (Wang et al. 2013 ). There are in fact several notable morphological differences in the ischium between these two taxa: the elongate, subtriangular lateral profile of the distal boot in Zuoyunlong presents a striking contrast to the relatively short, subcircular one in Yunganglong (Figures 3(A), (B) and (G)); the distal part of the ischial shaft in Yunganglong is very robust, with the slightly caudally divergent lateral and medial sides, while the equivalent structure in Zuoyunlong is mediolaterally constricted, and has the roughly parallel lateral and medial sides (Figures 3(C), (D) and (H)). ...
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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.