Wulagasaurus dongi, 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 : 60-65

publication ID	https://doi.org/ 10.4202/app.2008.0103
persistent identifier	https://treatment.plazi.org/id/E94887B3-ED32-A544-FFCC-FC3DFC4B0851
treatment provided by	Felipe
scientific name	Wulagasaurus dongi
status	sp. nov.

Treatment

Wulagasaurus dongi sp. nov.

Figs. 12–18 View Fig View Fig View Fig View Fig .

Derivation of the name: In honour of Dong Zhi−Ming, one of the most famous dinosaur specialists, for his fundamental contribution to the knowledge of dinosaurs in China.

Holotype: GMH W184 View Materials , a right dentary.

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

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

Material.—Braincases GMH WJ1, W384, W421; jugal GMH W166; maxillae GMH W233, W400−10; dentary GMH W217; scapulae GMH W267, W411; sternals GMH W194, W401; humeri GMH W320, W515−B; ischium: GMH W398−A.

Diagnosis.—As for the genus, by monotypy.

Description

Exoccipital−opisthotic complex (GMH WJ1, W384, W421; Figs. 12 View Fig , 13 View Fig ).—The exoccipital condyloids are rostrocaudally long, but mediolaterally compressed. They are pierced by four foramina. The caudal foramen is large and transmitted the hypoglossal nerve (CN XII). More rostrally, the foramen for the accessory nerve (CN XI) is the smallest of the three. The foramen for the vagus (CN X) and the glossopharyngeal (CN IX) nerves is the largest and is set more dorsally than the other two. Below this latter foramen, a fourth one is present in WJ1. It is always small and may represent either a separate passage for the glossopharyngeal nerve, assumed to be the smallest of the cranial nerves, or a rostral root of the hypoglossal nerve. The foramen for CN X is bordered rostrally by a prominent ridge extending from the ventral border of the paroccipital process to the rostroventral corner of the exoccipital condyloid. This pillar is not devel−

Parasaurolophus cyrtocristatus FMNH P 27393

Corythosaurus casuarius AMNH 5240 Prosaurolophus maximus ROM 787 Gryposaurus incurvimanus ROM 764 Edmontosaurus annectens DMNH 1493

oped in Kerberosaurus . Above this ridge, the rostrodorsal corner of the exoccipital condyloid is deeply excavated by the rostral margin of the auditory foramen. The paroccipital processes are broken off. They contact each other above the foramen magnum. At this level, their dorsal border is perfectly horizontal and forms a prominent caudal ridge below the supraoccipital. Between this ridge and the foramen magnum, the median surface of the exoccipital−opisthotic forms a basipterygoid process depressed area. However, it does not form an elongated shelf extending caudodorsally above the foramen magnum, as observed in Kerberosaurus and in derived North American hadrosaurines. It more closely resembles the condition observed in Maiasaura and Brachylophosaurus ( Horner 1992; Bolotsky and Godefroit 2004; Prieto−Marquez 2005). Lateral to the supraoccipital contact area, the dorsal border of the paroccipital processes steeply slopes dorsally, which contrasts with the more horizontal paroccipital processes of Sahaliyania .

Lateral wall of the braincase (GMH WJ1, W384, W421; Fig. 12 View Fig ).—Although this area is not finely preserved in the Wulagasaurus specimens at hand, several interesting characters can be observed. The crista otosphenoidalis is much less developed than in Sahaliyania . Although such a character is extremely difficult to quantify, it appears that this crest is usually better developed in lambeosaurines than in hadrosaurines. The foramen for CN VIII is rounded and nearly as large as the opening for the trigeminal nerve. A ventrally−directed sulcus for transmission of the ramus maxillaris (V 2) and ramus mandibularis (V 3) of the trigeminal nerve runs vertically from the latter opening. This sulcus is not developed in Kerberosaurus , but a deep pocket−like depression excavates the basisphenoid process of the prootic. The rostrally−directed horizontal sulcus for the ramus ophthalmicus (V 1) is better developed in Kerberosaurus than in Wulagasaurus .

Basioccipital–basisphenoid complex (GMH WJ1, W384, W421; Figs. 12 View Fig , 13 View Fig ).—This part of the skull is also incompletely preserved in Wulagasaurus . The basioccipital is relatively elongated and narrow. The sphenoccipital tubercles are not very prominent. Between the basipterygoid processes, there is also a well−developed median process, as observed in Sahaliyania . This process is apparently not developed in Kerberosaurus . The alar process of the basisphenoid, which conceals the carotid canal, is well developed and bilobate, as previously observed in the lambeosaurine Charonosaurus ( Godefroit et al. 2000) .

Supraoccipital (GMH WJ1; Fig. 13 View Fig ).—The straight basis of this pyramidal bone is inserted between the dorsomedial borders of the paired paroccipital processes. The dorsal surface of the supraoccipital is strongly sculptured, as usually described in hadrosaurids. Deeply depressed areas for insertion of the M. spinalis capitis and M. rectis capitis posterior circumscribe a prominent median promontorium laterally and ventrally. Lateral to these depressed areas, the caudolateral corners of the supraoccipital form a pair of prominent knobs, which insert in the notched caudoventral corners of the squamosals.

Parietal (GMH WJ1, W384, W421; Figs. 12 View Fig , 13 View Fig ).—The parietal of Wulagasaurus contrasts with that of Sahaliyania in being proportionally long and very narrow: the ratio “length/ minimal width” is>2.5. The sagittal crest is well developed on the caudal part of the parietal; on the other hand, the rostral half of the bone is devoid of a crest and its dorsal surface is regularly convex. This is the situation usually observed in lambeosaurines and in more basal forms, like Iguanodon , Probactrosaurus , and Bactrosaurus as well. In these forms, the parietal crest measures less than two−thirds the length of the parietal and less than half the length of the supratemporal fenestra. In typical hadrosaurines, on the other hand, the sagittal crest is longer, extending nearly along the whole length of the bone, and more than half the length of the supratemporal fenestra, as observed in Maiasaura (Albert Prieto−Marquez personal communication 2007), Brachylophosaurus ( Prieto−Marquez 2005: fig. 8, A), Gryposaurus ( Parks 1920: pl. 3: 2), Prosaurolophus ( Horner 1992) , Kerberosaurus ( Bolotsky and Godefroit 2004) , Saurolophus angustirostris (personal observation), Edmontosaurus ( Lambe 1920: fig. 4), and Anatotitan (personal observation). In Wulagasaurus , the rostral portion of the parietal is apparently not depressed around the contact area with the frontals, as it is described in Kerberosaurus ( Bolotsky and Godefroit 2004) . The caudolateral part of the parietal is notched to receive the large lateral knobs of the supraoccipital.

Jugal (GMH W166; Fig. 14A View Fig ).—Although it is incomplete, this partial jugal is clearly different from the specimens referred to Sahaliyania : it looks proportionally more elongated and more slender, with a more steeply inclined caudal process. It more closely resembles the jugals of non−edmontosaur hadrosaurines. For that reason, it is tentatively regarded as belonging to Wulagasaurus .

Maxilla (GMH W233, W400−10; Fig. 14B View Fig ).—Maxillae referred to Wulagasaurus are incompletely preserved in the Wulaga material: the specimens lack their rostral portion and the dorsal process is broken off. However, they display a typically hadrosaurine morphology: the base of the dorsal process is rostrocaudally elongated and the distal portion of the bone is very long and robust, contrasting with the more gracile condition observed in GMH W199 and in lambeosaurines. It may therefore be hypothesized that the complete maxilla of Wulagasaurus was roughly symmetrical when viewed laterally, as usually observed in hadrosaurines. Caudoventral to the dorsal process, the lateral side of the maxilla forms a short and low jugal process, which is very concave and slightly faces dorsally. This condition contrasts with the wide and prominent jugal process observed in Kerberosaurus and in a new hadrosaurine from Kundur. It more closely resembles the condition observed in Edmontosaurus (see Lambe 1920: fig. 12). However, this character cannot be adequately quantified and is therefore not really useful from a phylogenetic point of view. Ventral to the jugal process, the lateral side of the maxilla is pierced by a single foramen. Three to five foramina usually perforate the lateral surface of the maxilla in hadrosaurids, below and in front of the jugal process. It is also the case in the basal hadrosauroids Altirhinus ( Norman 1998) , Probactrosaurus ( Norman 2002: fig. 5), and Bactrosaurus ( Godefroit et al. 1998) . As is usual in hadrosaurids, the ectopterygoid ridge is very prominent and set very low on the lateral side of the maxilla. It is nearly horizontal; only the distal part is deflected ventrally. The ectopterygoid shelf is long, very wide and dorsoventrally concave. The caudal part of the dorsal border of the maxilla bears a large hook−like pterygoid process.

Maxillary teeth are typical for hadrosaurids and do not significantly differ from those described above in Sahaliyania .

Dentary (GMH W184, W217; Fig. 15 View Fig ).—These dentaries are proportionally much more elongated and slender than those of other hadrosaurids described to date. In GMH W184, the ratio “length of the dentary battery/maximum height of the dental ramus taken around the middle of the dental battery” is around 4.6. In Anatotitan copei , from the late Maastrichtian of western North America, the dentary also appears very elongated, but in this case it is the result of the extreme elongation of the diastema: the ratio “length of the dentary battery/maximum height of the dental ramus taken around the middle of the dental battery” = 3.16 in AMNH 5730. The slenderness of the dentary in Wulagasaurus is apparently not the result of allometric growth in hadrosaurids. Indeed, Lauters (2005) showed that there is a significant negative allometry between the height and the length of the dentary in Amurosaurus : it means that the dentaries of larger specimens look more slender than those of juveniles. On the other hand, GMH W184 (525 mm) and GMH W217 (> 535 mm) are more slender than the dentaries of larger advanced hadrosaurines. In medial view, the dental magazine is long, but unfortunately too eroded to estimate the number of alveolar coronoid process grooves. The height of the dental magazine regularly decreases rostrally. It means that tooth replacement was probably more limited in the rostral part of the dental battery that in the caudal part. In front of the dental magazine, the diastema forms an elongated notch on the dorsal border of the dentary. In Wulagasaurus , the diastema is about 4 times shorter than the dental magazine. In front of the diastema, the dorsal bor− der of the dentary slopes ventrally to form the concave articular surface for the predentary. The ventral border of the dentary is not strongly deflected ventrally, like in Sahaliyania , but it is smoothly concave in lateral view, as it is usually observed in hadrosaurines. As observed above, the degree of ventral deflection of the rostral part of the dentary is variable in hadrosaurids and difficult to estimate. Moreover, its polarity is also problematic. Pending more detailed studies on the variation of this character in North American hadrosaurids, we do not include this character in the phylogenetic analysis presented below. The lateral side of the dental ramus is smoothly convex dorsoventrally. There is no trace of vascular foramina, as those usually observed in other hadrosaurids. The coronoid process is broken off, but it is inclined rostrally, as in other hadrosaurids. The adductor fossa is very deep and both the mandibular groove and the angular facet are particularly elongated, extending further than the caudal third of the length of the dentary.

Scapula (GMH W267, W411; Fig. 16B, C).—These specimens significantly differ from the other scapulae discovered at Wulaga and more closely resemble hadrosaurine scapulae, with a long and narrow scapular blade ( Brett−Surman and Wagner 2007). Although it is heavily damaged and roughly restored with plaster, the proximal head appears less expanded dorsoventrally than in Sahaliyania . The acromial process is more laterally oriented and the deltoid ridge is more prominent. The deltoid fossa is narrower, but deeper. The long scapular blade is thicker, but appears less expanded craniocaudally.

Sternal (GMH W194, W401; Fig. 16A).—Although they are not completely preserved, these sternals are different from those described under Sahaliyania , rather displaying a typical hadrosaurine morphology ( Brett−Surman and Wagner 2007): the proximal plate is distinctly less expanded, both in length and in width, than in Sahaliyania . Consequently, the distal “handle” is longer than the proximal plate. The “handle” is very robust. Its ventral side is convex, whereas its dorsal side is flat. Its distal end is slightly expanded and bears longitudinal striations on both sides.

Humerus (GMH W320, W515−B; Fig. 17A View Fig ).—The deltopectoral crest of these humeri is distinctly less developed than in the other specimens of similar size found in Wulaga locality. It more closely resembles the condition encountered in hadrosaurines. For that reason, those humeri are tentatively associated with the Wulagasaurus material. The most striking character of these specimens is the orientation of their deltopectoral crest. Usually in hadrosaurids, the edge of the deltopectoral crest is oriented laterally, or slightly craniolaterally. In GMH W320 and W515−B, on the other hand, the edge of the deltopectoral crest is oriented quite cranially, at an angle of 90 ° to its usual orientation. Although these humeri are not completely preserved, it is unlikely that the unusual orientation of their deltopectoral crest is an artefact of preservation. Indeed, post−mortem deformation at this level would have completely destroyed the thin deltopectoral crest. But there is no breakage between the base of the deltopectoral crest and the shaft of the humerus either in GMH W320 or in GMH W515−B. Therefore, we consider that this orientation of the deltopectoral crest was present in the living animal. Of course, this configuration of the deltopectoral crest influences the whole morphology of the bone. The bicipital gutter is much deeper and, on the proximal side of the bone, the humeral head is more prominent than in other hadrosaurids. The articular head extends distally as a very long and prominent vertical ridge, much better developed

GODEFROIT ET AL.—LATE CRETACEOUS HADROSAURIDS FROM NW CHINA 65

proximal plate 50 mm 100 mm scapular blade 50 mm deltoid ridge deltoid ridge glenoid glenoid distal ‘handle’ acromial coracoid facet coracoid facet process

than in other hadrosaurids. Because of the concomitant cranial orientation of the deltopectoral crest and the important development of the caudal crest, the craniocaudal maximum diameter of the humerus is much more important than the mediolateral diameter, which is an uncommon character among hadrosaurids. Also contrasting with the normal hadrosaurid condition, the inner tuberosity is much better developed than the outer tuberosity on the proximal end of the humerus. The distal end of the humerus is slightly turned laterally, as usually described in hadrosaurids. It is unfortunately too crushed to be adequately described.

Ischium (GMH W398−A; Fig. 17B View Fig ).—Although it is very incomplete, this specimen significantly differs from the other ischia discovered at the Wulaga locality and described above under Sahaliyania . The ischial shaft is very slender, straight and rod−like. The minimum circumference of the shaft is 128 mm, for a total length greater than 1100 mm. This is very low, when compared to lambeosaurine specimens of similar size (compare with GMH W400−2: length = 1098 mm, minimum circumference of the shaft = 161 mm). This is the condition usually observed in hadrosaurines. For this reason, GMH W398−A is tentatively referred to Wulagasaurus .

Hadrosauridae indet.

The Wulaga locality has also yielded many other hadrosaurid isolated bones that do not display any diagnostic character. For that reason, it cannot be decided whether these bones belong to Sahaliyania , Wulagasaurus , or any other hadrosaurid. These bones are listed in Appendix 1. Pending the discovery of associated specimens, these bones are not described in the present paper and are referred to as Hadrosauridae indet.