Increased excavation of dinosaurs from China over the last two decades has enriched the record of Asian titanosauriform sauropods. However, the relationships of these sauropods remain contentious, and hinges on a few well-preserved taxa, such as Euhelopus zdanskyi. Here we describe a new sauropod, Yongjinglong datangi gen. nov. et sp. nov., from the Lower Cretaceous Hekou Group in the Lanzhou Basin of Gansu Province, northwestern China. Yongjinglong datangi is characterized by the following unique combination of characters, including seven autapomorphies: long-crowned, spoon-shaped premaxillary tooth; axially elongate parapophyses on the cervical vertebra; very deep lateral pneumatic foramina on the lateral surfaces of the cervical and cranial dorsal vertebral centra; low, unbifurcated neural spine fused with the postzygapophyses to form a cranially-pointing, triangular plate in a middle dorsal vertebra; an “XI”-shaped configuration of the laminae on the arches of the middle dorsal vertebrae; a very long scapular blade with straight cranial and caudal edges; and a tall, deep groove on the lateral surface of the distal shaft of the radius. The new specimen shares several features with other sauropods: a pronounced M. triceps longus tubercle on the scapula and ventrolaterally elongated parapophyses in its cervical vertebra as in Euhelopodidae. Based on phylogenetic analyses Yongjinglong datangi is highly derived within Titanosauria, which suggests either a remarkable convergence with more basal titanosauriform sauropods in the Early Cretaceous or a retention of plesiomorphic features that were lost in other titanosaurians. The morphology and remarkable length of the scapulocoracoid reveal an unusual relationship between the shoulder and the middle trunk: the scapulocoracoid spans over half of the length of the trunk. The medial, notch-shaped coracoid foramen and the partially fused scapulocoracoid synostosis suggest that the specimen is a subadult individual. This specimen sheds new light on the diversity of Early Cretaceous Titanosauriformes in China.

Funding: Funding was provided by the National Natural Science Foundation of China and the Hundred Talents Project of the Chinese Academy of Sciences to YHL, and by the Gansu Bureau of Geology and Mineral Resources to Li DQ. The authors acknowledge the support of NSF EAR 1024671 to PD (YHL and LDQ co-PIs) for research in the Early Cretaceous of Gansu. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Copyright: © 2014 Li et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

In the upper picture the red star presents the fossil locations of Yongjinglong, Daxiatitan and Huanghetitan and also the green star shows the excavation location of Euhelopus. In the lower picture the exposed fossils are marked.

The earliest reported Chinese sauropod dinosaur, Euhelopus zdanskyi (originally Helopus zdanskyi) from Shandong Province, eastern China, was described in 1929 by the Swedish paleontologist Carl Wiman [1] ; additional material was described in 1935 by C.-C. Young [2] ( Fig.1 ). During the subsequent half century, the most famous sauropods found in China include Omeisaurus [3] , [4] , Shunosaurus [5] , [6] and Mamenchisaurus [7] – [11] , all of which come from the Middle to Upper Jurassic strata of the Sichuan Basin, southwestern China [6] , [10] . More recently, Cretaceous sauropods have been excavated in several areas of China, especially in Gansu Province, northwestern China. These include four Early Cretaceous taxa: Gobititan shenzhouensis [12] , Huanghetitan liujiaxiaensis [13] , Daxiatitan binglingi [14] , and Qiaowanlong kangxii [15] . Most of these sauropods were originally described as basal members of Titanosauriformes. In the latest studies, however, Qiaowanlong was recovered as a derived member of Somphospondyli, rather than in Brachiosauridae [16] – [18] , and has been assigned to Euhelopodidae, a newly defined clade of Somphospondyli comprising Euhelopus and possibly several other contemporaneous East Asian sauropods, including Daxiatitan [19] (though see [18] for a partly contrasting view). Here we describe another new sauropod, Yongjinglong datangi gen. nov. et sp. nov., from the Lower Cretaceous Hekou Group in the Lanzhou-Minhe Basin, Gansu Province, the same strata that yielded Huanghetitan liujiaxiaensis and Daxiatitan. The new taxon is based on a specimen that comprises three isolated teeth, eight vertebrae, the left scapulocoracoid, and the right radius and ulna. The bones are mostly dark brown and the principal matrix is dark red sandy mudstone with somewhat grayish mottling. The remains were collected in 2008 by two of us (DL and HY) along with the field team from the Fossil Research and Development Center, Gansu Provincial Bureau of Geo-exploration and Mineral Development. The localities that produced Yongjinglong, Daxiatitan, and Huanghetitan liujiaxiaensis are all near the town of Zhongpu ( Fig. 1 ). The Yongjinglong locality, beside the G75 Highway, is less than a kilometer from the quarries that produced Daxiatitan and Huanghetitan liujiaxiaensis. This new specimen adds to the growing number of recent Chinese sauropod finds and highlights the increasing understanding of the diversity of Titanosauriformes in the Early Cretaceous of Asia.

The terminology of laminae and fossae in this study follows the nomenclature system of Wilson [20] – [21] and Wilson et al. [22] ) with the exception that the terms “anterior, posterior” and their cognates are replaced by “cranial, caudal” and their cognates as required by adoption of standardized anatomical nomenclature for tetrapods, that is Nomina Anatomica Veterinaria (NAV) and the Nomina Anatomica Avium (NAA).

The electronic edition of this article conforms to the requirements of the amended International Code of Zoological Nomenclature, and hence the new names contained herein are available under that Code from the electronic edition of this article. This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information viewed through any standard web browser by appending the LSID to the prefix “ http://zoobank.org/ ”. The LSID for this publication is: urn:lsid:zoobank.org:pub:37C5C4B6-2009-462C-9FE4-9A9C3C9A3CBC. The electronic edition of this work was published in a journal with an ISSN, and has been archived and is available from the following digital repositories: PubMed Central, LOCKSS [ http://www.lockss.org ].

The holotype specimen described in this report was recovered by the field crew of the former Fossil Research and Development Center of the Third Geology and Mineral Resources Exploration Academy of Gansu Province for excavation and preparation of the specimens from the Early Cretaceous Hekou Group of the Lanzhou-Minhe Basin in southeastern Gansu Province, China in 2008. The team included Mr. Tao Wang and Mr. Huang and other workers, who carried out fieldwork and preparation. The specimen was recovered as a result of traditional, systematic field prospecting in sediments of the Hekou Group that had previously yielded a fauna comprising of sauropods and other dinosaurs. The fossils were jacketed in the field using standard plaster and burlap, and transported by truck to the Gansu Geological Museum in Lanzhou, where the fossils were extracted from their jackets and removed from the enclosing matrix using small pneumatic air scribes and dissecting needles. All specimens are curated in the collections of the Gansu Geological Museum, where they are available for comparative study to qualified researchers.

Long-crowned, spoon-shaped premaxillary tooth; large, deep lateral pneumatic foramina (pleurocoels) spanning the entirety of the lateral surfaces of the cervical and cervicodorsal vertebrae; a complex “XI”- and “IX”-shaped configuration of laminae on left and right lateral surfaces of the articulated middle dorsal vertebrae, respectively; low unbifurcated neural spine that, along with the postzygapophyses, forms a cranially-pointing, triangular plate in at least one middle dorsal vertebra; very long scapular blade with exceptionally straight cranial and caudal edges.

The location of Yongjinglong beside the G75 Highway is less than a kilometer from the quarries of Daxiatitan and Huanghetitan liujiaxiaensis, which are all located in the southeastern part of the Lanzhou-Minhe Basin ( Fig. 1 ), Gansu Province, P. R. China; upper Hekou Group, Lower Cretaceous (Editorial Committee of Chinese Stratigraphic Standard: Cretaceous 2000).

The generic name “Yongjing,” from ancient Chinese, refers to Yongjing County, which is close to the fossil location of the new sauropod and which also yields numerous dinosaur track fossils; and “long,” meaning dragon, all in Chinese. The specific name “datangi” refers to the Tang dynasty and also honors Mr. Zhi-Lu Tang from the Institute of Vertebrate Paleontology and Paleoanthropology, Beijing for his numerous contributions to the research of dinosaurs.

Description

Caudal Cervical Vertebra (Fig. 3A–F; Table 2) The caudal cervical vertebra has a well-preserved centrum and part of the neural arch, but lacks most of the neural spine and the postzygapophyses. Fragments of the tuberculum and capitulum are fused with the respective extensions of the diapophyses and parapophyses; this fusion is more obvious on the right side. The total combined height of the centrum and the preserved neural arch is not large (150 mm). The centrum is axially short, slender, and typically opisthocoelous. It bears a well-developed, hemispherical cranial condyle. The condyle is axially elongate and half the length of the centrum, from which it is strongly set off. The condyle is dorsoventrally compressed and asymmetrical in lateral view, with the ventral portion more bulbous than its dorsal counterpart. The caudal articular cotyle lacks the outer bone edge and appears as a shallow, concave surface with a distinctive camellate texture; the average diameter of a chamber is 5 mm and the thickness of the walls is less than 1 mm on average. The height and width of the cotyle are subequal. The ventral surface of the centrum is shallowly concave and lacks a keel. A deep, undivided lateral pneumatic foramen occupies the entire lateral surface of the centrum; its deepest (95 mm) point is close to cranial edge of the centrum. The lateral foramen may connect to its opposite counterpart. The upper margin of the foramen merges smoothly into the ventral margin of the neural arch. The ventral margin of the foramen is continuous with the base of the parapophysis; no fossa invades the dorsal surface of either parapophysis. The left parapophysis is better preserved than the right. The cranial base of the parapophysis is adjacent to the caudal edge of the condyle. The base of the parapophysis is remarkably long, spanning four-fifths of the ventrolateral margin of the centrum. The cranial edge of the parapophysis projects caudolaterally and the caudal edge projects craniolaterally; the two edges merge distally to form a tapered rib articulation. The preserved part of the neural arch is relatively low, only half the height of the centrum. The neural spine is missing, so its height and orientation cannot be determined. The prezygapophyses are supported from below by single, stout centroprezygapophyseal laminae (cprl); no pre-epipophyses are present. The preserved parts of the prezygapophyses are low and oriented dorsolaterally in cranial view. The shapes of the articular facets of the prezygapophyses are unclear due to damage. The caudal part of the neural arch is damaged; only a fragment of the left postzygapophysis remains and it extends beyond the caudal margin of the centrum without evidence of an epipophysis. The diapophysis lies near the neurocentral junction and projects cranially and ventrolaterally over the lateral margin of centrum. The attached tuberculum of the rib, which appears as a lateral continuous part of the diapophysis, has been largely weathered away and exposes a cross section of the rib, which has a distinct, camellate texture internally. In lateral view, parts of the cprl, the posterior centrodiapophyseal lamina (pcdl), and the centropostzygapophyseal (cpol) laminae combine to form a long, continuous plate that tapers caudally. The neural canal is subcircular; its width and height are 55 mm and 45 mm, respectively. A slender, needle-shaped structure is visible in dorsal view that begins above the caudal cotyle and narrows cranially. It is composed of matrix and represents an infilling of the neural canal.

Dorsal Vertebrae (Figs. 4–9; Table 2) Seven dorsal vertebrae are preserved. Among them, four are identified as the cranial dorsal vertebrae on the basis of the positions of their parapophyses. The presumed first cranial dorsal is referred to as Dv1; the remaining three are referred to as Cranial DvA, DvB and DvC. The remaining three articulated vertebrae (MD1–3) are identified as middle dorsal vertebrae based on the sizes, shapes, and relative positions of their parapophyses and diapophyses.

First Dorsal Vertebrae (Dv1) (Fig. 4A–F; Table 2) A massive vertebra preserves a parapophysis on the left lateral side of the centrum and has a relatively higher-positioned neural spine compared to the caudal cervical vertebra; it is here identified as the first dorsal vertebra. It comprises most of the centrum and neural arch. The ventral margin of the centrum is heavily damaged, but it retains the complete condyle. In cranial view, the condyle is dorsoventrally compressed and strikingly deformed as an asymmetric hemisphere: the left side is more expanded than the right side. Remarkably, the axial length of the bulbous condyle is half that of the rest of the centrum. As on the caudal cervical vertebra, the lateral pneumatic foramen occupies the entire lateral surface of the centrum and it shallows from cranial to caudal. Also as on the caudal cervical, the margin of the lateral pneumatic foramen coincides with the ventral surface of the pcdl. The ventral surface of the centrum appears to be nearly flat; it is damaged, but lacks any evidence of either a concavity or a ventral keel. In caudal view, the camellate texture on the cotyle surface comprises bony walls less than 1 mm in diameter (close-up in Fig. 4B). PPT PowerPoint slide

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larger image TIFF original image Download: Figure 4. The relatively complete first dorsal vertebra of the holotype specimen of Yongjinglong datangi (GSGM ZH(08)-04). A–E, photographs and interpretive line drawings in A, cranial; B, caudal; C, left lateral; D, right lateral, and E, ventral views. Scale bar equals 100 mm. Abbreviations as in Figure 3, plus: nsp, neural spine; pocdf, postzygapophyseal centrodiapophyseal fossa; podl, postzygadiapophyseal lamina; sdf, spinodiapophyseal fossa; sprl, spinoprezygapophyseal lamina; sprf, spinoprezygapophyseal lamina fossa. https://doi.org/10.1371/journal.pone.0085979.g004 The neural arch is slightly taller than its centrum, but is expanded laterally far more than in the caudal cervical vertebra. The neural spine is not well-preserved, but its base forms a small bump at the intersection of the spinoprezygapophyseal laminae (sprl) and the spinopostzygapophyseal laminae (spol) (Fig. 4A, B). The spol are robust and thick, but the sprl are virtually paper thin. The left prezygapophysis extends cranially beyond the condyle; its articular facet is rectangular and slightly convex transversely. The angle between the prezygapophyses is approximately 130° in cranial view (Fig. 4A). The left postzygapophysis bears a strong, ventrolaterally oriented articular facet, which is rectangular with a 135 mm-long major axis and 65 mm-long minor axis. In lateral view, the caudal margin of the postzygapophysis does not extend beyond the caudal edge of the centrum (Fig. 4C, D). The maximum distance between the dorsal tips of the postzygapophyses is nearly 460 mm, and the angle between them is close to 130°. The left diapophysis retains an airfoil-like cross section with a dorsoventral long axis. In lateral view, the prezygadiapophyseal lamina (prdl) is not thick but is wing-shaped. The postzygadiapophyseal laminae (podl) and the prezygadiapophyseal laminae (prdl) join to form a V-shaped structure in lateral view. The four laminae (prdl, sprl, podl, and spol) surround a large spinodiapophyseal fossa (sdf) that is 90 mm deep (Fig. 4B).

Middle Dorsal Vertebrae (Figs. 8–9) Three articulated dorsal vertebrae (from cranial to caudal: MD1, MD2, and MD3) are recognized as pertaining to the mid-dorsal column based on the sizes and shapes of the parapophyses and diapophyses, as well as the proximities of the processes to each other. Compared to the relatively low, transversely expanded neural arches of the cervical and cranial dorsal vertebrae, those of the middle dorsal vertebrae are much higher and closer to the midline. The lateral surfaces of these middle dorsals bear simple, undivided, and less-developed lateral pneumatic fossae, which are readily distinguished from the deep, prominent fossae in the cervical and cranial dorsal vertebrae. The three articulated middle dorsal vertebrae are rather massive. The three vertebrae are well-preserved on their left sides, but two of them lack neural spines. All are nearly equal to each other in the heights of the neural arches and the lengths of the centra (Figs. 8–9). MD1 has a well-preserved neural arch and centrum (Fig. 9). The centrum is much lower than the neural arch and is subequal to it in length. In lateral view the compressed,camellate condyle is not very prominent and is less hemispherical than those of the cervical vertebra and Cranial DvA and DvB. However, the articular surface of the condyle is larger than that of the cervical vertebra and similar in size to those of the cranial dorsal vertebrae. In cranial view, the condyle is taller than it is wide and its greatest width is below the midpoint. The shape of the cotyle is congruent with that of the condyle. The lateral pneumatic foramen is surrounded by a shallow fossa that occupies nearly half of the lateral surface of the centrum, but the foramen is relatively shallower and smaller than those of the cervical vertebra and the cranial dorsal vertebrae. The ventral surface of the centrum is more strongly concave transversely than the cervical vertebra and the previous dorsal vertebrae. The caudal part of the neural arch extends over the caudal rim of the cotyle. The neural spine is the only one well-preserved among all the preserved vertebrae of the holotype and is therefore of great importance for interpreting the relationships of this specimen. In dorsal view (Fig. 9E), the neural spine is fused with the postzygapophyses to form a cranially-pointing, trifid, triangular plate. This interesting trifid structure may reflect epaxial muscle tendon insertions associated with the postzygapophyses. The apex of the triangle is the summit of the neural spine, which is slightly higher than the diapophyses, craniolateral to the neural spine. The sprl, prdl, and spol surround a large, deep sdf. The sprl are slightly thicker than those of the cervical and cranial dorsal vertebrae; they subtend an angle of 110°. In cranial view, between the cprf of each side, lie clear, “stranded” [20] cprls dorsolateral to the neural canal (Fig. 9B). The prezygapophyses are slender and lie dorsal to the parapophyses. In cranial view, the parapophysis is situated high on the neural arch, lateral and slightly ventral to the prezygapophyses (Fig. 9B). In lateral view, the parapophyses project more cranially than the prezygapophyses (Figs. 9A, C). The parapophyses bear cupped, ovoid articular facets. In lateral view, the diapophysis lies farther caudodorsally than the parapophysis on the neural arch, below the neural spine; the articular facet on the right diapophysis is slightly concave and faces dorsolaterally. The right facet is larger than that of the parapophysis on the same side. A caudal centroparapophyseal lamina (pcpl) supports the diapophysis and connects with the acdl cranioventrally and pcdl craniodorsally. These three laminae thus frame a complex, “XI”-shaped configuration in left lateral view (or “IX”-shaped in right lateral view) (Fig. 8), in which two tiny, recessed accessory laminae lie below and parallel to the pcpl and acdl, respectively. The laminae of the XI-shaped complex surround four fossae of different sizes and shapes. In caudal view, a “stranded” postspinal lamina (posl) [20] is flanked by two parallel cpol without any sign of a hyposphenes; this absence is paralleled by the other two middle dorsal vertebrae. Ventrally, the posl bifurcates to form the roof of the neural canal. The neural canal is oval; its width and height are 50 mm and 40 mm, respectively. The two following articulated dorsal vertebrae in the series, MD2 and MD3, are similar to MD1 in most respects (Fig. 8). The neural arches on both are noticeably taller than on MD1. The lateral pneumatic fossa of MD2 is larger than that of MD3. The XI-shaped complexes of laminae have more simplified fossae and sublaminae surrounded by the three main laminae mentioned above. The neural spines are too damaged to provide any further information. The postzygapophysis of MD2 lies at the level of the preserved neural spine of MD3, and its round, dorsal edge is attached tightly to the prezygapophysis of MD3. The left parapophysis of MD2 is slightly higher than those of the adjacent vertebrae, and it is slightly larger than that of MD3 on the same side.

Rib (Fig. 10) The only costal element preserved in GSGM ZH(08)-04 is the proximal part of a heavy dorsal rib that is 678 mm long (Fig. 10). The maximum and minimum widths are 282 mm and 100 mm, respectively. The considerable distance between the capitulum and the fragmentary tuberculum suggests that the rib pertains to a cranial or middle dorsal vertebra. On the lateral surface, a robust ridge that begins near the caudoventral edge of the tuberculum runs diagonally across the midshaft and reaches the opposite edge distally (Fig. 10A). On both the ridge and the distal part of the rib, breakage has cleanly exposed a matrix infill of what could be either a simple medullary cavity or a pneumatic diverticulum. In medial view, a large groove occupies the whole middle surface of the preserved rib and gradually diminishes distally (Fig. 10B). The cross section of the plank-like rib through the robust ridge is triangular, with a breadth more than three time its thickness (Fig. 10C). In cross section the bone wall is thicker around the edge of the rib and thinner in the middle of the rib. The internal empty space, which is infilled with dark brown matrix (Fig. 10C), suggests the possibility of pneumaticity of ribs, though no pneumatic foramen is evident on the proximal end of the rib. PPT PowerPoint slide

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larger image TIFF original image Download: Figure 10. Proximal end of a dorsal rib of the holotype specimen of Yongjinglong datangi (GSGM ZH(08)-04). A–C, photographs and interpretive outline drawings in A, medial and B, lateral and C, the cross-section views. In views A and B the dashed outline drawings show the broken edges of the rib. In B, the red dashed line denotes the position of a natural break that exposes the interior structure of the element. In C, the grey area and line represent the bony wall or chamelle in the rib. Scale bar equals 100 mm. https://doi.org/10.1371/journal.pone.0085979.g010

Appendicular Skeleton Preserved appendicular skeletal elements include the left scapulocoracoid, and the right ulna and radius.

Scapula (Fig. 11; Table 3) The scapula accounts for approximately 80% of the total length of scapulocoracoid (Table 3). It has a short proximal plate and a craniocaudally slender blade (Fig. 11A, B). In lateral view, the cranial edge of the acromion ridge of the plate extends straight dorsoventrally, without a marked dorsal angulation or hook. The thickness of the plate gradually increases from cranial to caudal and dorsal to ventral, starting at 20 mm along the craniodorsal edge and reaching a maximum of 190 mm close to the glenoid. The acromion bears a relatively prominent deltoid crest lying close to the dorsal margin of the plate; the angle between the longitudinal axis of the scapular blade and the oblique ridge of deltoid crest is about 58° degrees. This oblique ridge forms the dorsal border of a single, large fossa for the origin of M. deltoideus scapularis [24]. The scapular portion of the glenoid faces caudoventrally, has a deep, eye-shaped, concave surface, and exhibits slight medial beveling. Strikingly, the scapular blade is more than twice as long as the plate but only half as wide. The length of the blade is about 4.5 times its minimum width. The distances from the dorsal edge of the acromion to the ventralmost point of the glenoid and to the mid-point of the blade are subequal. The cranial and caudal margins of the blade are straight and parallel to each other (Fig. 11A, B). Through the middle of the blade, the cross section is roughly D-shaped, slightly concave medially and convex laterally. In the broken cross section, the outer rim of the blade is made of dense cortical bone, but the interior is spacious and filled with sediment, indicating a large medullary cavity (Fig. 11). Close to the proximal end of the scapular blade, on the lateral surface, a shallow fossa bordered by a ridge may mark the origin for the M. scapulohumeralis and M. dorsalis scapulae [23], [24]. Dorsal to the glenoid and the acromion, on the caudal edge of the blade, lies a low but prominent triangular process (Fig. 11A, B). This process is considered an origin site of M. triceps longus [24] and we here name it the triceps longus tubercle (tlt). The middle of the blade is the thinnest portion mediolaterally, in contrast to both the proximal and distal portions. The minimum breadth of the slender blade (215 mm) is one-seventh of the scapular length. No ridges are developed on the medial surface of the blade, but a single, prominent ridge appears on the lateral surface of the blade. The ridge lies along, and is oriented parallel to, the midline of the blade and spans nearly its whole length. The distal end of the scapular blade is slightly expanded caudally, but retains a D-shaped cross section (Fig. 11D). On the distal end of the lateral surface, another fossa marks the probable origin of the M. teres major [23], [24].

Coracoid (Fig. 12; Table 3) Compared to the extremely long scapula, the coracoid is a small, square plate, only one-fourth the length of the scapula (Figs. 11, 12). The dorsoventral length of the coracoid is subequal to its width but only half that of the scapular plate. The planar coracoid portion of the glenoid faces caudodorsally and is smaller in outline than the concave elliptical scapular half of the glenoid. The coracoid is partially fused with the scapula: the fusion of the two elements apparently proceeded from cranial to caudal and was arrested in mid-fusion. The unfused part (40 mm width dorsoventrally) is close to the glenoid cavity and is filled with grey matrix (Fig. 12A, B), suggesting incomplete ossification consistent with subadult status. On the lateral side, the large, nearly circular coracoid foramen, the passage for N. supracoracoideus [26] and the supracoracoid artery [27], is shared almost equally by the scapula and coracoid (Fig.12A). On the medial side, however, though the synostosis is somewhat difficult to discern, but it appears that most of the coracoid foramen penetrates the adjacent plate of the scapula (Fig. 12B); its broad base rests in the coracoid but the keyhole-shaped foramen extends dorsally onto the plate of the scapula. PPT PowerPoint slide

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larger image TIFF original image Download: Figure 12. Coracoid of the holotype specimen of Yongjinglong datangi (GSGM ZH(08)-04). Elements in lateral (A) and medial (B) views. The red line denotes the coracoid foramen, and the green dashed lines demarcate the unfused region infilled with the grey matrix, Scale bar equals 100 mm. Abbreviations: s, scapula; c, coracoid; cf, coracoid foramen. https://doi.org/10.1371/journal.pone.0085979.g012

Ulna (Figs. 13–15; Table 4) The right ulna is a robust element, though the proximal end is much more robust than the distal end (the proximal mediolateral width divided by the total length is 0.57). The proximal end is triradiate, with craniomedial, craniolateral, and caudal processes (Fig. 14), which form a well-developed notch or groove on the cranial margin for receiving the radius. In proximal view, the strongly concave craniomedial process is longer and more slender than the craniolateral process. The craniolateral process, however, is more elevated and slopes gently cranially. The craniomedial and craniolateral processes subtend an angle of 70°. The caudal process, which is capped proximally by the olecranon area that marks the site of insertion of the triceps muscles, is round and slightly higher than the craniolateral process. It tapers gradually to merge into the craniolateral process, but forms a sharp step at the junction with the craniomedial process. The step corresponds to the boundary between the cranial processes that articulate with the humerus and the non-articular olecranon. In cranial view, the lateral process is much higher than the medial one. A robust ridge extends distally along the proximocaudal margin of the ulna. Both the lateral and the medial surfaces of the proximal portion of the ulna are strongly concave (Fig. 14A). The triangular shaft of the ulna tapers to a rugose, ovoid, caudally expanded surface at the distal end, though the distal end that expands caudally. The lower half of the ulna presents two well-defined interosseous ridges that bound a strong radial groove into which the caudodistal end of the radius articulates (Fig. 14B). As with the radius, in cranial view the distal end of the ulna bears rugose texturing that may correspond to attachments of the M. pronator quadratus [24] or ligamentous tissues, such as a syndesmosis binding the ulna to the radius. The minimum circumference of the ulna lies slightly below the midshaft. PPT PowerPoint slide

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larger image TIFF original image Download: Figure 14. Right ulna of the holotype specimen of Yongjinglong datangi (GSGM ZH(08)-04). Elements in cranial (A), caudal (B), lateral (C), proximal (D), medial (E), and distal (F) views. Scale bar equals 100 mm. Abbreviation: ole, olecranon. https://doi.org/10.1371/journal.pone.0085979.g014