Sahaliyania elunchunorum, Godefroit & Shulin & Tingxiang & Lauters, 2008

Godefroit, Pascal, Shulin, Hai, Tingxiang, Yu & Lauters, Pascaline, 2008, New hadrosaurid dinosaurs from the uppermost Cretaceous of northeastern China, Acta Palaeontologica Polonica 53 (1), pp. 47-74 : 49-59

Sahaliyania elunchunorum sp. nov.

Figs. 2–10 .

Derivation of the name: The Elunchun nationality is one of the smallest Chinese minorities. These hunters lived for generations in the Wulaga area.

Holotype: GMH W453 , a partial skull.

Type locality: Wulaga (Heilongjiang province, China). Coordinates of the site: N 48 ° 23’40.9’’ E 130 ° 08’44.6’’ .

Type horizon: Yuliangze Formation ( Wodehouseia spinata – Aquilapollenites subtilis Palynozone, Maastrichtian , Upper Cretaceous).

Material.—Braincase GMH W453; jugals GMH W200−A, W281, W400−5, 424, W unnumbered; maxillae GMH W199; quadrates GMH W31, W271, W342, W367, W394, W404, W476; dentaries GMH W33, W50−1, W105, W140, W153, W201, W227, W228, W290, W298, W324−A, W393, W418, W419−A, W424, W451, 457, W461, W465, W466, W501; scapulae GMH W1, W21, W31, W52, W148, W182, W202, W210, W214, W222, W272, W284, W286, W291, W309, W360, W373, W387, W392, W394, W400−1, W400−6, W422, W463, W473; sternals GMH W165, W246, W406−A; humeri GMH W15, W42, W58, W59, W110, W116, W154, W158, W168, W 192−A, W 192−B, W 201, W232, W240, W250, W271, W303, W317, W344, W367, W392, W402, W410, W411, W413−A; ilia GMH WJ1, WJ4, W23, W45, W51, W103, W173, W228, W243−A, W273, W301, W311, W359, W370, W421; ischia GMH W10, W13, W50−6, W51, W136−A, W146, W171, W177, W179, W180, W197, W233−B, W255, W270, W291, W310, W375, W400−13, W404, W415−A, W415−B, W471−D; pubes GMH W10, W13, W51, W136, W146, W171, W177, W179, W180, W197, W233, W270, W291, W 310, W375, W379, W 400−13, W404, W415−A, W 415−B, W471.

Diagnosis.—As for the genus, by monotypy.

Description

Exoccipital−opisthotic complex ( Figs. 2 , 3 ).—The basal part of the exoccipital condyloids is eroded, so the morphology of the foramina for cranial nerves IX–XII can not be adequately described. Around the foramen magnum, the dorsal surface of the exoccipital−opisthotic is slightly depressed. The left paroccipital process is complete dorsomedially: it is particularly long, but very slender. Its dorsal border is slightly convex, whereas its ventral border is slightly concave. Although the paroccipital processes are variable in shape, those of Sahaliyania are clearly different from those of other known lambeosaurines. In Charonosaurus , the paroccipital processes are much shorter and more robust ( Godefroit et al. 2001: fig. 5). In Amurosaurus ( Godefroit et al. 2004b: fig. 7), Jaxartosaurus (PIN 1/5009, personal observation), Tsintaosaurus ( Young 1958: fig. 1), Corythosaurus (AMNH 5240, personal observation), Hypacrosaurus (ROM 702, personal observation), Lambeosaurus (ROM 1218, personal observation), and Parasaurolophus ( Sullivan and Williamson 1999: fig. 16), the paroccipital processes are also more robust than in Sahaliyania and have a more pendant aspect: their mediodorsal border slopes dorsally, whereas their laterodorsal bor− der is strongly inclined ventrally.

Lateral wall of the braincase ( Figs. 2 , 3 ).—The different bones that form the lateral wall of the braincase are completely fused together, so their limits cannot always be adequately described. From the rostrolateral side of the paroccipital process, a broad and rounded crista otosphenoidalis runs along the lateral side of the lateral wall of the braincase. Below this crest, the foramen for CN VIII, is small and separated from the postotic foramina by a well−developed and rounded ridge that extends from the ventral border of the paroccipital process to the rostroventral corner of the exoccipital condyloid. However, the trigeminal foramen (for CN V) is very large, as in all hadrosaurids. From this foramen, both the rostrally−directed horizontal sulcus for the ramus ophthalmicus (V 1) and the ventrally−directed vertical sulcus for the ramus mandibularis (V 3) and ramus maxillaris (V 2) of the trigeminal nerve are less clearly marked than in Amurosaurus . Between the trigeminal foramen and the foramen for CN VIII, the lateral wall of the braincase is pierced by two foramina: the caudodorsal one transmitted the ramus hyomandibularis and the cranioventral one, the ramus palatinus of the facial nerve (CN VII). A small sulcus runs from the latter foramen ventrally along the lateral side of the prootic to the vicinity of the carotid canal; this channel housed the ramus palatinus of the facial nerve. It looks wider, but shallower than in Amurosaurus .

Basisphenoid ( Figs. 2 , 3 ).—The basisphenoid is eroded in GMH W453, so only a few interesting characters can be observed. In caudal view, a pair of concave processes, separated by a very deep incision, project laterally from the body of the basisphenoid to form the rostral part of the sphenooccipital tubercles. At the junction between the broken basipterygoid processes, a small median process projects caudoventrally. This process is much better developed in Amurosaurus . On the other hand, it is absent in Charonosaurus . In lateral view, the alar process of the basisphenoid is very developed and nearly symmetrical. This condition is also observed in Charonosaurus . In Amurosaurus , on the other hand, the alar process is asymmetrical in lateral view. The caudodorsal ramus of the alar process conceals the carotid canal, which carried the internal carotid artery from the lateral surface of the basisphenoid. The internal carotid artery penetrates the basisphenoid through a large canal, visible on the ventral side of GMH W473. The caudal aperture is concealed laterally by the rostroventral ramus of the alar process and the canal opens into the caudoventral part of the hypophyseal cavity.

Supraoccipital ( Figs. 2 , 3 ).—The supraoccipital is a pyramidal bone that extends rostrally above the occipital region, between the exoccipital−opisthotic and the parietal. Its external surface is unfortunately too eroded to be adequately described.

Parietal ( Fig. 2A ).—As usual in lambeosaurines, the parietal of Sahaliyania is proportionally short and wide. With a “length/minimal width” ratio = 1.5, it is proportionally much wider than in Amurosaurus (1.9 in AEHM 1/232). The rostral portion of its dorsal surface is very slightly convex. Caudally, it forms a low sagittal crest. Even if it is eroded, this crest appears much less developed than in Amurosaurus : in this genus, the sagittal crest forms caudally a high triangular process that overhangs the rostrodorsal part of the supraoccipital. The sagittal crest is similarly high in Jaxartosaurus , Tsintaosaurus , Corythosaurus , Hypacrosaurus , Lambeosaurus , and Parasaurolophus . In Charonosaurus , on the other hand, the sagittal crest is not developed at all and the dorsal surface of the parietal is, therefore, regularly convex ( Godefroit et al. 2001). However, given the eroded state of the dorsal aspect of GMH W479, it seems difficult to draw meaningful conclusions as to the autapomorphic nature of this feature.

Frontal ( Fig. 2A ).—The complete fusion of the frontals, as observed in this specimen, is unusual in lambeosaurines. It suggests that GMH W453 belongs to an old adult specimen. The dorsal surface of the caudal part of the frontal is perfectly flat in GMH W453. In numerous lambeosaurine specimens, on the other hand, the dorsal surface of the frontal forms a caudomedian doming, as observed in Hypacrosaurus (AMNH 5248, Fig. 2B ), “ Procheneosaurus convincens ” (PIN 2230) , “ Cheneosaurus tolmanensis ” ( Lambe 1917) , “ Tetragonosaurus erectofrons ” ( Parks 1931; Evans et al. 2005), Jaxartosaurus aralensis (PIN 5009), and Amurosaurus riabinini (AEHM 1/232). Study of the Amurosaurus collection suggests that the frontal doming is especially developed in juvenile specimens ( Godefroit et al. 2004b). Many large lambeosaurine specimens, like ROM 1940, also completely lack the median dome. Therefore, the absence of a median dome also confirms that GMH W453 does belong to an adult specimen. With a “caudal length/maximal width” ratio (see Godefroit et al. 2004b for a definition of this ratio) estimated at 0.6, the frontal of GMH W453 is much wider than in Amurosaurus (1.02 in AEHM 1/232; Godefroit et al. 2004b). As usual in lambeosaurines, the rostral part of the dorsal surface of the frontal is highly modified to form the base of the hollow crest. It forms a broad and strongly grooved platform that slopes forwardly and provides strong attachment of the nasals. In Sahaliyania , the rostral platform appears relatively short. Although GMH W453 does belong to an adult specimen, the platform does not extend far caudally. In comparison, it is much better developed in Charonosaurus and Parasaurolophus : in these genera, the rostral platform extends caudally above the rostral part of the parietal and of the supratemporal fenestrae ( Sullivan and Williamson 1999; Godefroit et al. 2001). Although it is short, the frontal platform of Sahaliyania is relatively wide, as also observed in adult specimens of Corythosaurus (ROM 1940)

Sahaliyania elunchunorum Amurosaurus riabinini Olorotitan arharensis and Hypacrosaurus ( Gilmore 1937: fig. 32): in these genera, the rostral platform is either wider than the caudal part of the frontal, or both parts have approximately the same width. However, it is probably an ontogenetic character: in smaller Corythosaurus and Hypacrosaurus specimens (e.g., AMNH 5248, AMNH 5433), in which the frontals are not fused together and the median doming is well developed, the frontal platform is much narrower than the caudal part of the frontal. In Amurosaurus , on the other hand, the rostral platform is always much narrower than the caudal part of the frontal, even in large adult specimens. In this genus, the prefrontal forms the greatest part of the platform that supports the base of the hollow crest ( Godefroit et al. 2004b). In Sahaliyania , the lateral margin of the frontal forms a thick and interdigitate contact area, rostrally for the prefrontal and caudally for the postorbital. The frontal therefore did not participate in the dorsal margin of the orbit. Between the rostral platform and the lateral contact area for the prefrontal, the dorsal surface of the frontal forms a pair of well−developed cup−shaped depressed areas. Depressions on the dorsal surface of the frontal near the prefrontal and postorbital joints have also been observed in other lambeosaurine taxa, including Amurosaurus (AEHM 1/232), Hypacrosaurus (AMNH 5248), and Corythosaurus (AMNH 5433). In these lambeosaurines, the frontal depressions are, in any case, much smaller than in Sahaliyania , and are found associated with the median doming of the frontal, characteristic for juvenile specimens. Frontal depressions have also been described in the hadrosaurine Brachylophosaurus ( Horner 1988; Prieto−Marquez 2005), but they are less developed than in Sahaliyania .

Jugal ( Fig. 4A ).—The jugal of Sahaliyania is proportionally short and robust. In lateral view, its rostral process is dorsoventrally expanded. It forms a high lacrimal process and a prominent, hook−like ventral region. The rostral margin of the jugal is convex: it is not perfectly straight, as observed in Olorotitan . The best preserved jugal from the Wulaga collection, GMH W200−A, is particularly robust when compared with other lambeosaurine jugals discovered in the Amur Region ( Fig. 4A ). However, the relative robustness of the jugal probably reflects the allometric growth of this bone ( Fig. 5 ). Pearson’s correlation coefficient between the total length of the jugal (in log 10) and the height of the jugal neck (in log 10), estimated from the Amurosaurus sample, is very high: r = 0.95. The allometry coefficient has been estimated using Teissier’s (1948) least squares formula. Indeed, both measurements are herein regarded as interdependent. Positive allometry exists between the length of the jugal and the height of the jugal neck in Amurosaurus (k = 1.625). This means that the jugal is proportionally more robust in larger than in smaller specimens. Moreover, two large jugals, respectively belonging to Olorotitan (AEHM 2/845) and Sahaliyania (GMH W200−A) are located exactly in the extension of the regression line. It indicates that GMH W200−A appears very robust, when compared with Amurosaurus specimens, only because it is very large. The apparent robustness of the jugal in Sahaliyania specimens at hand is therefore not a diagnostic character, but a consequence of the positive allometry of this character in lambeosaurines. In Sahaliyania , the postorbital process of the jugal is robust. Its rostral side is concave for reception of the ventral process of the postorbital. The caudal process is a broad plate that raises caudodorsally. Together with the postorbital process, it circumscribes the ventral margin of the infratemporal fenestra. This fenestra is somewhat narrower in Sahaliyania than in Amurosaurus or Charonosaurus . The ventral border of the caudal process is much expanded and salient, forming a ventral flange that resembles that observed in hadrosaurines.

Maxilla ( Fig. 4B ).—In lateral view, the maxilla of Sahaliyania is asymmetrical, with the dorsal process lying well behind the middle of the bone, as usually observed in lambeosaurines. The rostral part of the maxilla is elongated and slen− der; it regularly tapers rostrally. It is medially expanded to form a wide premaxillary shelf, characteristic for lambeosaurines and better developed than in Amurosaurus . The dorsal process and the caudal part of the maxilla are eroded, so only a few interesting characters can be observed on this part of the maxilla. Caudal to the maxillary shelf, a large ovoid neurovascular foramen penetrates the dorsal process to communicate with the excavated caudomedian area of this process. The caudal portion of the maxilla appears short and gracile. The medial surface of the maxilla is perfectly flat and pierced by a series of special foramina interconnected by a gently curving horizontal groove at the middle of the bone.

Several maxillary teeth are preserved on this specimen. However, the dental battery is too incomplete to estimate the minimal number of tooth rows. As usual in hadrosaurids, the maxillary teeth are miniaturised, very narrow, diamond−shaped, perfectly straight and symmetrical. The enamel forms a strong and perfectly straight median ridge on the lateral side of the crown. Their borders are rather coarsely denticulate.

Quadrate ( Fig. 4C ).—The general morphology of the quadrate of Sahaliyania is typical for lambeosaurines. It is proportionally low and robust, and distinctly curved caudally. Although such differences are difficult to quantify, typical hadrosaurine quadrates are usually proportionally more slen− der and straighter. The proximal head is subtriangular in cross−section and much flattened mediolaterally. The pterygoid wing is robust and rostromedially oriented. A prominent vertical ridge along the caudomedial side of the quadrate shaft marks the contact with the quadrate process of the pterygoid. The jugal wing is regularly rounded and slightly curved inwards. Beneath the jugal wing, the quadratojugal notch, located along the dorsoventral axis of the quadrate, is high and deep. Usually in lambeosaurines, the middle of the quadratojugal notch more or less coincides with the middle of the height of the quadrate. This situation can be observed in Corythosaurus (AMNH 5338), Hypacrosaurus (MOR 549), Lambeosaurus (TMP 66.04.01), Amurosaurus (AEHM 1/42), and Tsintaosaurus (IVPP K68). In Sahaliyania , on the other hand, the quadratojugal notch is distinctly displaced ventrally and the middle of the notch is always set well below the middle of the height of the quadrate. An elongated facet runs along nearly the whole height of the quadratojugal notch, indicating that it was completely covered by the quadratojugal and that the paraquadratic foramen was closed, as usual in hadrosaurids. The distal end of the quadrate forms a large hemispherical lateral condyle that articulated with the surangular component of the mandibular glenoid. A smaller medial condyle, which fitted into the articular component of the mandibular glenoid, is set more dorsally at the base of the pterygoid wing.

Dentary ( Fig. 6 ).—In lateral view, the most striking character that can be observed in the dentary of Sahaliyania is the important ventral deflection of its rostral part, which forms an angle of about 30 ° with the long axis of caudal part of the bone. In large adult specimens, the deflection of the ventral margin of the dentary usually begins somewhat caudal to the middle of the bone. On the other hand, the dorsal margin is deflected in front of the dental battery. Although it is variable, a ventral deflection of the rostral part of the dentary is a usual character in lambeosaurines. In Sahaliyania (r = 0.977) and Amurosaurus (r = 0.881), the length of the dentary (in log 10) and the height of the ventral deflection (in log 10) are strongly correlated ( Fig. 7 ). The allometry coefficient has been estimated in both genera from the slope of the regression line, because the length of the dentary can be regarded, in this case, as an independent variable ( Teissier 1948): k = 1.36 in Sahaliyania and k = 1.22 in Amurosaurus . Isometry (k = 1) can be rejected at p = 0.05. This means that the ventral deflection of the dentary is proportionally more important in larger than in smaller specimens. If the allometry coefficient is higher in Sahaliyania than in Amurosaurus , this difference is not significant at p = 0.05 ( Chassé and Pavé 1975: 287). The allometry coefficient has also been calculated using Teissier’s (1948) least squares method (both measurements are regarded, in this case, as interdependent). With this method, the coefficients are much higher: k = 1.57 in Sahaliyania and k = 1.41 in Amurosaurus . The rostral part of the dentary is more strongly deflected in Sahaliyania , Amurosaurus , and Tsintaosaurus than in other lambeosaurines from Asian and North American lambeosaurines ( Fig. 7 ). However, this observation needs to be confirmed by the statistical study of larger samples. As usual in hadrosaurids, the dental battery of Sahaliyania is long and, in larger specimens, the dental battery fits into around 42–44 narrow parallel−sided alveolar grooves, visible in medial view. The edentulous portion is proportionally very short. The rostral articular surface for the predentary is typically scoop−shaped and slightly inclined towards the sagittal axis of the mandible. In dorsal view, the dentary appears less curved externally than that of Charonosaurus , for example. The lateral side of the dentary is very convex. It is irregularly pierced by several foramina for vessels and nerves. The coronoid process is high and robust, with a flattened inner side. As is usual in hadrosaurids, it is rostrally inclined and slightly curved inwards; its lateral side bears an extended triangular surface along its dorsal part, marking the insertion of a powerful M. pseudotemporalis. In caudal view, the dentary is deeply excavated by the adductor fossa, which extends rostrally as a deep mandibular groove. Under this groove, the medial side of the dentary bears a very long angular facet. The caudoventral end of the coronoid process bears a large triangular facet for the splenial. A very thin bony plate conceals the dental battery. Its base is pierced by a series of special foramina arranged into a horizontal line. Each foramen strictly corresponds to one tooth row.

The dentary teeth are also diamond−shaped, like the maxillary ones. However, they look proportionally wider than the maxillary teeth, with a “height/width” ratio of about 3 for the teeth located in the middle of the dental battery. They appear proportionally wider than the dentary teeth of Charonosaurus . If the median carina is perfectly straight on the caudal and central dentary teeth, it is slightly sinuous on the rostral ones. This character is often observed in lambeosaurines ( Godefroit et al. 2001).

Scapula ( Fig. 8A ).—The Wulaga material includes 25 scapulae of different sizes that closely resemble those of Olorotitan . For that reason, they are tentatively referred to Sahaliyania . One single specimen from Wulaga is distinctly different from the others, more closely resembling the condition observed in hadrosaurines; this specimen is therefore tentatively referred to the hadrosaurine Wulagasaurus gen. nov. (see below). All scapulae are unfortunately very incomplete and roughly restored with plaster. In Sahaliyania , the ventral head of the scapula appears more robust and craniocaudally expanded than in Amurosaurus . The coracoid suture is large and cup−shaped. It is separated from the acromial process by a concave emargination of the cranioventral border of the scapula. The acromial process extends dorsally into the form of a short rounded deltoid ridge. Both the acromial process and the deltoid ridge appear distinctly less prominent than in other lambeosaurines from the Amur / Heilongjiang region, but this may be an artefact of preservation. The deltoid fossa is wider than in Amurosaurus . Caudally to the coracoid facet, a long crescentic depression represents the craniodorsal part of the glenoid. A prominent dorsal buttress that slightly faces laterally supports the scapular portion of the glenoid. Because of the great expansion of the ventral head, the scapular neck appears well contracted. The scapular blade is very thin and long; it is proportionally wider craniodorsally than in Amurosaurus . Its cranial and caudal borders are sub−parallel and gently curved caudally. The scapular blade is also smoothly curved inwardly. Its lateral side is slightly convex dorsoventrally, whereas its medial side is slightly concave.

Sternal ( Fig. 8B ).—As in other hadrosaurids, the sternal of Sahaliyania is typically hatchet−shaped. As in lambeosaurines, its proximal plate is enlarged both in length and in width. It is thinner laterally than medially. The proximal plate is distinctly longer than the distal “handle”. Although incompletely preserved, the thin lateral border of the proximal plate is distinctly convex. The distal “handle” of the sternal is relatively short, but massive and slightly curved dorsally; its distal end is slightly enlarged. The dorsal side of the “handle” bears many longitudinal striations. Both the proximal and distal borders of the sternal are very roughened, indicating the presence of cartilaginous caps. The ventral side of the sternal is slightly convex mediolaterally, whereas its dorsal side is slightly concave.

Humerus ( Fig. 9A ).—Twenty−five humeri from the Wulaga collection are typically lambeosaurine in shape, with a long and wide deltopectoral crest that is slightly turned medially, especially in larger specimens. In lambeosaurines, the width of the deltopectoral crest is significantly correlated (p>0.05) to the length of the humerus ( Fig. 9B ): r = 0.98 in Sahaliyania and 0.82 in Amurosaurus . But the width of the deltopectoral crest apparently develops isometrically when compared to the length of the humerus (k = 0.96 in Sahaliyania and 0.89 in Amurosaurus ). The globular proximal articular head forms a rounded buttress on the caudal side of the humerus. The inner tuberosity is less developed on the proximal end of the humerus than the outer tuberosity. On the caudal side of the humerus, a smooth rounded crest descends from the proximal articular head, but it is never as developed as in Charonosaurus (see Godefroit et al. 2000); on the cranial side of the humerus, the bicipital gutter is also less well marked than in Charonosaurus . Lateral to the humeral head, a large depressed area marks the insertion of a strong M. triceps humeralis posticus, as usually observed in lambeosaurines ( Godefroit et al. 2001, 2004b). Medial to the humeral head, a less markedly depressed area indicates the inserinner articular head

2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 Log length (x)

Amurosaurus Olorotitan Corythosaurus Sahaliyania Tsintaosaurus Parasaurolophus tion of the M. scapulo−humeralis. The distal portion of the humerus is slightly twisted laterally. The ulnar condyle is slightly more developed than the radial condyle.

Ilium ( Fig. 10A ).—Although they are crushed medio−laterally, the ilia in this sample closely resemble those of lambeosaurines attributed to the Corythosaurus lineage by Brett−Surman and Wagner (2007). The preacetabular process forms a long and tapering projection from the craniodorsal edge of the iliac blade. It is moderately deflected ventrally and very elongated, closely resembling the condition observed in Charonosaurus : in both taxa, the ratio “ilium length/preacetabular length” is around 2.1. The lateral side of the preacetabular process is perfectly flat. Its dorsal edge is very thickened and rounded, whereas its ventral edge is thinner. The caudal half of its medial side bears, at about the dorsal third of its height, a carina. The main blade of the ilium is very high. At the level of the ischial peduncle, its dorsolateral border is folded laterally to form a prominent and roughened antitrochanter. Because it is always crushed in the Wulaga material, the relative development of the antitrochanter, which is an important character in lambeosaurines, cannot be adequately compared with other hadrosaurids discovered in Amur / Heilongjiang region. A strong ridge medially thickens the dorsal part of the main blade of the ilium, in continuity with that on the medial side of the preacetabular process. It fuses caudally with the dorsal border of the ilium, at the level of the ischial peduncle. The preacetabular notch is well developed and rather open, because of the slight ventral deflection of the preacetabular process. The iliac portion of the acetabulum is shallow. The ischial peduncle is craniocaudally elongated. Its articular surface faces caudoventrally and is formed by two sub−rectangular protrusions separated by a well−marked depression. The postacetabular notch is only slightly marked. The postacetabular process is long, high, and sub−rectangular in shape, also resembling the condition described in Charonosaurus .

Ischium ( Fig. 10B ).—The ischia of Sahaliyania are typical for lambeosaurines: the ischial shaft is long and very robust, gently sigmoidal in lateral view, and it terminates into a prominent foot−like expansion. Between its dorsal and ventral margins, the medial side of the ischial shaft forms a deep sulcus. The medial side of the ischial foot bears many elongated striations, indicating strong ligamental attachment between paired ischia. The cranial region of the ischium is expanded and it tilts a few degrees laterally. The iliac peduncle is subrectangular and projects craniodorsally; its dorsal articular surface is slightly expanded both mediolaterally and dorsoventrally and is sub−ellipsoidal in cross section. The pubic peduncle is more slender and less differentiated than the iliac peduncle. It is very elongated craniocaudally and very compressed mediolaterally. The articular facet for the pubis is sub−rectangular in cross section. The obturator process is well developed, projecting ventrally lower than the pubic peduncle. Its ventral border is expanded to closely contact the pubic bar. It is prolonged caudally as a strong oblique carina along the medial side of the ischial shaft. The obturator process and the pubic peduncle limit an ovoid and ventrally open obturator gutter.

Pubis ( Fig. 10C ).—The pubes from the sample are intermediate in robustness between those of Corythosaurus casuarius and of Parasaurolophus cyrtocristatus ( Brett−Surman and Wagner 2007) . The prepubic neck is relatively short, but massive. The prepublic blade is well expanded. All the specimens discovered at Wulaga are characterized by a very asymmetrical expansion of the prepubic blade, with an important emphasis to the dorsal side. In Sahaliyania , the dorsal expansion of the prepubic blade is more important than its ventral expansion ( Fig. 11 ). Even if the prepubic blade is also slightly expanded dorsally in some specimens of Corythosaurus casuarius (ROM 1947) and Lambeosaurus magnicristatus (TMP 66.04.01; David C. Evans, personal communication 2007), the ventral expansion of the blade remains more important, as usually observed in hadrosaurids. The iliac process of the pubis is prominent and robust; its lateral side bears a strong, vertical and roughened ridge that limits rostrally the acetabular surface of the bone. Its medial side bears a well−marked triangular and striated surface, indicating a close contact with one of the first sacral ribs. The ischial peduncle is long and its articular surface with the ischium is expanded and rounded. The proximal part of the ischial peduncle bears a well−marked ventrolateral boss, also observed in a new hadrosaurine from Kundur (P.G. unpublished data). The postpubic rod is short, robust, mediolaterally compressed and straight. Table 1 summarises the main differences observed in the skeleton of Sahaliyania and of the other three lambeosaurines currently described in the Amur / Heilongjiang region: Charonosaurus jiayinensis , Amurosaurus riabinini , and Olorotitan arharensis .

Figures

Fig. 2. A. The hadrosaurid dinosaur Sahaliyania elunchunorum gen. et sp. nov., holotype GMH W453 from the Upper Cretaceous Yuliangze Formation at the Wulaga quarry, China. B. Hypacrosaurus altispinus Brown, 1913, specimen AMNH 5248 from the Upper Cretaceous Horseshoe Canyon Formation of Alberta, Canada. Braincases in dorsal (A1, A2) and left lateral (A3, A4) views; photographs (A1, A3) and explanatory drawings (A2, A4), with close−ups of the frontal region in S. elunchunorum (A5) and H. altispinus (B). Dotted lines indicate hypothetical sutures.

Fig. 3. The hadrosaurid dinosaur Sahaliyania elunchunorum gen. et sp. nov. holotype GMH W453 from the Upper Cretaceous Yuliangze Formation at the Wulaga quarry, China. Braincase in caudal (A, B) and right lateral (C, D) views. Dotted lines indicate hypothetical sutures. Photographs (A, C) and explanatory drawings (B, D).

Fig. 4. The hadrosaurid dinosaur Sahaliyania elunchunorum gen. et sp. nov. from the Upper Cretaceous Yuliangze Formation at the Wulaga quarry, China. A. GMH W200−A, left jugal in medial (A1) and lateral (A2) views. B. GMH W199, left maxilla in lateral (B1) and medial (B2) views. C. GMH W476, right quadrate in lateral (C1) and medial (C2) views.

Fig. 5. Relative growth of the height of the jugal neck (y) and of the jugal length (x) in lambeosaurine dinosaurs from the Amur/Heilongjiang region.

Fig. 6. The hadrosaurid dinosaur Sahaliyania elunchunorum gen. et sp. nov. from the Upper Cretaceous Yuliangze Formation at the Wulaga quarry, China. A. GMH W451, left dentary in medial (A1) and lateral (A2) views. B. GMH W153, right dentary in medial (B1) and lateral (B2) views, and detail of dentary teeth (B3).

Fig. 7. A. Relative growth of the ventral deflection of the rostral part (y) and of the length (x) of the dentary in lambeosaurine dinosaurs. B. Explanation of the measurements.

Fig. 8. The hadrosaurid dinosaur Sahaliyania elunchunorum gen. et sp. nov. from the Upper Cretaceous Yuliangze Formation at the Wulaga quarry, China. A. GMH W148, right scapula in medial (A1) and lateral (A2) views. B. GMH W165, right sternal in ventral view.

Fig. 9. The hadrosaurid dinosaur Sahaliyania elunchunorum gen. et sp. nov. from the Upper Cretaceous Yuliangze Formation at the Wulaga quarry, China. A. GMH W201, right humerus in caudal (A1) and cranial (A2) views. B. Relative growth of the width of the deltopectoral crest (y) and of the length of the humerus (x) in lambeosaurine dinosaurs.

Fig. 10. The hadrosaurid dinosaur Sahaliyania elunchunorum gen. et sp. nov. from the Upper Cretaceous Yuliangze Formation at the Wulaga quarry, China. A. GMH W103, right ilium in lateral (A1) and medial (A2) views. B. GMH W400−2, right ischium in lateral view. C. GMH W179, left pubis in lateral (C1) and medial (C2) views.

Fig. 11. Pubis shape in various hadrosaurids. A, original data; B–F, after Brett−Surman (1989).