A new tyrannosauroid from the Upper Cretaceous of Shanxi, China

Journal Pre-proof A new tyrannosauroid from the Upper Cretaceous of Shanxi, China Wu Xiao-chun, Shi Jian-Ru, Dong Li-Yang, Thomas D. Carr, Yi Jian, Xu Shi-Chao PII:

S0195-6671(19)30190-9

DOI:

https://doi.org/10.1016/j.cretres.2019.104357

Reference:

YCRES 104357

To appear in:

Cretaceous Research

Received Date: 9 May 2019 Revised Date:

25 November 2019

Accepted Date: 11 December 2019

Please cite this article as: Xiao-chun, W., Jian-Ru, S., Li-Yang, D., Carr, T.D, Jian, Y., Shi-Chao, X., A new tyrannosauroid from the Upper Cretaceous of Shanxi, China, Cretaceous Research, https:// doi.org/10.1016/j.cretres.2019.104357. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Crown Copyright © 2019 Published by Elsevier Ltd. All rights reserved.

A new tyrannosauroid from the Upper Cretaceous of Shanxi, China

Wu, Xiao-chun,1,* Shi, Jian-Ru,2 Dong, Li-Yang,2 Carr, Thomas D,3 Yi, Jian,4,5 Xu, Shi-Chao2

¹Canadian Museum of Nature, P.O Box 3443 STN ‘D’, Ottawa, Ontario K1P 6P4, Canada E-mail: [email protected] 2

Shanxi Museum of Geology, Binhexilu Zhongduan, Taiyuan, Shanxi 030024, P. R. China

E-mail: [email protected]; [email protected] [email protected] 3

Department of Biology, Carthage College, 2001 Alford Park Drive, Kenosha, WI 53140, USA,

E-mail: [email protected] 4

Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, P.

O. Box 643, Beijing 100044, P. R. China 5

University of Chinese Academy of Sciences, Beijing, China

E-mail: [email protected]

*Corresponding author: [email protected]; Tel.: 613-364-4035; Fax.: 613-364-4027

Abstract: Since 1983, only herbivorous dinosaurs and some isolated teeth of theropods have been described from the Upper Cretaceous of Shanxi Province, China. Here we report a new tyrannosauroid from the Upper Cretaceous of the province mainly based on a pair of maxillae and an associated dentary. This new dinosaur, named Jinbeisaurus wangi gen. et sp. nov., in addition to representing the first theropod dinosaur so far found in Shanxi Province it also adds to the known diversity of tyrannosauroids in Asia. J. wangi can be identified mainly by a broad interfenestral strut, a deep fossa on the broad base of the septum between the promaxillary recess and maxillary antrum, a low position of the dorsal row of dentary foramina, a similar number of denticles per unit length on both the mesial and distal carinae of the upper and lower teeth, and an acute angle of about 70 degrees between the posterior process of the foot and the shaft of the pubis. J. wangi is a small to medium-sized theropod and phylogenetically crowner than Suskityrannus of North America within Tyrannosauroidea, probably even more derived than Xiongguanlong baimoensis from Gansu Province, China.

Keywords: Dinosaur; Tyrannosauroidea; Upper Cretaceous; Shanxi Province; China

1. Introduction

The Huiquanpu Formation, previously considered to be Eocene, has been reassigned to the Upper Cretaceous since many dinosaur remains discovered in the formation in early 1980s (Chen et al., 1983). The formation, containing over 200 meter thick terrestrial deposits, covers an area about 150 square km wide around the boundary area between Tianzhen County of Shanxi Province and Yangyuan County of Hebei Province in northern China. In 1989 and 1991−1994, Shijiazhuang University of Economics, Shijiazhuang, Hebei Province (now Heber Geo University, HGU) excavated a large number of dinosaur specimens from the formation in Tianzhen County of the Shanxi side (Pang et al., 1996). Of this collection, three dinosaur taxa were described in late 1990s and at the beginning of this century, namely, the ankylosaurs Tianzhenosaurus youngi (Pang & Cheng, 1998) and Shanxia tianzhenensis (Barrett et al., 1998) and a sauropod Huabeisaurus allocotus (Pang & Cheng, 2000). In addition, this collection includes some theropod teeth and hadrosaurid remains. Pang and Cheng (2000) referred the former as cf. Szechauanosaurus campi Young, 1942 and the latter as cf. Shantungosaurus sp. of Hu (1973), but these two assignments were later disputed separately by other studies (Carrano et al., 2012; Xu et al., 2016). Recently, Xu et al. (2016) described a new hadrosaur, Datonglong tianzhenensis, based on an incomplete specimen from the same quarry as the other taxa, the Kangdailiang Quarry (KDLQ hereafter for convenience), of HGU. Here we describe a new tyrannosauroid represented by some skull bones and a few isolated postcranial bones. The Shanxi Museum of Geological and Mineral Science and Technology (now Shanxi Museum of Geology, SMG) collected these specimens from the Huiquanpu Formation near Yangjiayao, Tianzhen County in 2008 (Fig. 1). The new fossil quarry

is about five km northeast of the KDLQ from which the most of the dinosaur specimens of HGU came from. In addition to this theropod dinosaur, the new quarry also produces ankylosaur and hadrosaur remains as the KDLQ did. Our fieldwork of 2018 confirmed that the new quarry and KDLQ are both located in the same section of strata, close to the top of the formation (Fig. 2). Although the specimen of the new tyrannosauroid is incomplete, it shows a number of significant anatomical features, the striking of which include a broadened interfenestral strut that reaches over 85% of the cranio-caudal length of the maxillary fenestra in lateral view and a large promaxillary recess on the medial surface that bears three furrows. The narrow septum separating the promaxillary recess from the maxillary antrum on the medial surface bears a deep fossa and the dorsal row of dentary foramina positioned along the lateral midheight along the length of the dentary are also peculiar within tyrannosauroids. In addition, both anterior and posterior carinae possess 16 denticles in each five mm measured from the middle section of the tooth crown in the maxilla and dentary teeth. These unique characters allow us to establish a new taxon for the specimens, Jinbeisaurus wangi gen. et sp. nov. Our phylogenetic analysis suggest that the new theropod is a tyrannosauroid, crowner than Suskityrannus (Nesbitt et al., 2019) as evidenced by the derived state of some characters of the maxilla, such as the maxillary fenestra with a V-shaped caudal margin and the ventral margin of the maxilla convex.

2. Material and methods The material studied here is housed in the Shanxi Museum of Geology, Taiyuan, Shanxi Province, China. It was prepared with mechanical tools (airscribes) and photographed from various perspectives with a Nikon D610 digital camera. The figures were prepared on Adobe Photoshop CS6 and Illustrator CS6 software. Line drawings were made based on these photos

and checked against the original material. Measurements of selected body regions were taken directly from the original. Institutional abbreviations. CMN, Canadian Museum of Nature (Ottawa, Canada); HDU, Hebei Geo University (Shijiazhuang, Hebei Province, China); IVPP, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (Beijing, China); SMG, Shanxi Museum of Geology (Taiyuan, Shanxi Province, China).

3. Systematic Palaeontology

Dinosauria Owen, 1842 Theropoda Marsh, 1881 Tyrannosauroidea Walker, 1964 (sensu Holtz, 2004) Jinbeisaurus gen. nov.

Etymology. Generic name derived from the Chinese ‘jin’ (the abbreviation of Shanxi Province) and ‘bei’ (north)—the northern part of Shanxi, from which the material was recovered, with the suffix ‘saurus’ from the Latin for ‘lizard’. Diagnosis. As for type and only known species (see below)

Jinbeisaurus wangi sp. nov. LSID: urn:lsid:zoobank.org:pub:F8CA22F1-6323-462E-BF32-03C6A164C82E

(Figs. 3-7)

Etymology. Specific name is in honour of Mr. Suozhu Wang for his great contribution to the vertebrate paleontology of Shanxi Province, including organizing field explorations and discovering many Mesozoic fossils of reptiles within the province. Holotype. SMG V0003, including a pair of maxillae (nearly complete right bone and incomplete left bone) and an incomplete right dentary, associated with two cervical centra, five dorsal centra, and an incomplete right pubis. Comments: These disarticulated specimens were referred to as one theropod individual because (1) they came from the same quarry within an area less than eight square meters, (2) no duplicated bones were found in the quarry, (3) the sizes of these specimens match each other. Locality and horizon. Yangjiayao, Tianzhen County, Datong City, Shanxi Province, China; the upper part of the Huiquanpu Formation, Upper Cretaceous. Diagnosis. It differs from other tyrannosauroids in the following combination of derived characters: (1) in lateral view, the interfenestral strut (between the antorbital fenestra and maxillary fenestra) is broad and covers more than 85% of the cranio-caudal length of the maxillary fenestra; (2) in lateral view, the ventral part of the antorbital fossa, ventral to the antorbital fenestra at the point just posterior to the tooth row is deeper than the subcutaneous surface below it; (3) the posteroventral end of the promaxillary recess on the medial surface stops above the fifth maxillary alveolus; (4) in medial view, the narrow septum between the promaxillary recess and maxillary antrum becomes broad ventrally and bears a small but deep fossa on its base: (5) in medial view, the anterior part of the maxillary antrum is nearly as large as the maxillary fenestra; (6) in lateral view, the dorsal row of the dentary foramina extends along the midheight of the dentary; (7) both anterior and posterior carinae bear a similar number of denticles per unit length (about 16 measured from the middle section of the tooth crown) in

the maxilla and dentary teeth; and (8) the well-developed posterior process of the pubic foot forms an acute angle (about 70 degrees) relative to the shaft of the bone. Comments: in the known ontogenetic studies of tyrannosauroids, the relatively broad strut, greater than 55% of the anteroposterior length is an early ontogenetic state and a relatively narrow, less than 55%, represents a late ontogenetic stage in the tyrannosaurine D. horneri (Carr et al., 2017). This does not appear applicable to T. bataar, another tyrannosaurine, in which the ratio is nearly same, about 50% of the anteroposterior length of the maxillary fenestra, in a juvenile with a tooth row length of about 18 cm, young adult, and an adult with a tooth row length about 60 cm (Currie, 2003: fig. 3E-G). Compared with the aforementioned two tyrannosaurines, the strut is relatively much broader, over 85% of the anteroposterior length of the maxillary fenestra although its maxillary tooth row is much longer than that of the juvenile of T. bataar (Currie, 2003: fig. 3E). According to the above incongruent conditions of the character in tyrannosauroids, character (1) of the diagnosis is most probably true, representing an autapomorphy of the new taxon other than a juvenile character of a known taxon.

4. Description and Comparison

The right maxilla is more complete than the left (Fig. 3). The maxilla is a large, roughly triangular bone with a posteroventral and posterodorsal rami in life as in other tyrannosauroids, such as Albertosaurus libratus (Currie, 2003: fig. 3A) or Daspletosaurus torosus (CMN 8506). As preserved, the maxilla is 34 cm long, with the missing posterior tip about four cm long, and 13.5 cm tall. The preserved anterior facet for the premaxilla and nasal is about 19.5 cm long, and the height of the maxilla below the maxillary fenestra is about eight cm. The posteroventral

ramus reached the jugal, but its posterior tip is missing and the posterodorsal ramus, much of which is broken away, extended to the lacrimal. The two rami form the margins of the anterior part of the antorbital fenestra and fossa. In lateral view, the anterior edge of the maxilla is slightly convex and the ventral margin is distinctly convex. The posteroventral ramus tapers and slightly extends ventrally. The lateral surface bears numerous enlarged foramina in a row close to the ventral margin (alveolar row). The largest foramen measures around 10 mm long, though most are subcircular and only around 3 mm or smaller in diameter. A second row of foramina extends below the ventral margin of the antorbital fossa (circumferential row), which served for exits of trigeminal nerve branches and associated blood vessels (Carr et al., 2017). These foramina are smaller in diameter than those of the alveolar row. The lateral surface as a whole is weakly rugose, with faint flutes that extend posterodorso-anteroventrally toward the ventral margin of the bone. The ventral edge of the posteroventral ramus is weakly crenulated, with subtle concavities that correspond to the positions of the tooth sockets. The posteroventral ramus defines the shelf-like ventral edge of the antorbital fossa and forms the ventral margins of the maxillary fenestra and antorbital fenestra. Above the shelf-like ventral edge, the medially recessed strip of bone belonging to the antorbital fossa is about 23 mm high throughout the ventral edge of the maxillary fenestra (line 1 in figure 2). The recessed strip then becomes lower, about 17 mm high (line 2 in Fig. 3) below the ventral margin of the antorbital fenestra at the point before meeting the jugal or posterior to the tooth row. The anterior end of the recessed strip extends medial to the posterior edge of the posterodorsal ramus, and a furrow or fossa leads into the promaxillary fenestra (PMF). Accordingly, the posterodorsal ramus largely conceals the fenestra in lateral view, which was considered to represent a late stage of ontogeny in a tyrannosaurine (Carr et al., 2017). The maxillary fenestra is nearly midway

between the anterior margins of the antorbital fossa and antorbital fenestra as in A. libratus of any age (Currie, 2003: fig. 3A), Bistahieversor sealeyi with a maxillary tooth row length of about 50 cm (Carr & Williamson, 2010), and Appalachiosaurus montgomeriensis with a maxillary tooth row length of about 43 cm (Carr et al., 2005). This appears also the case in juvenile tyrannosaurine specimens, such as IVPP V 4878, the type of “Shanshanosaurus huoynshanensis” (Dong, 1977) that was later considered as a juvenile of T. bataar (Currie and Dong, 2001: fig. 1C; Currie, 2003: fig. 3E). In contrast, mature tyrannosaurines have greatly enlarged maxillary fenestrae with anterior margins that approach or reach the anterior margin of the antorbital fossa (see Currie, 2003: fig. 3D, G, H). The maxillary fenestra is roughly triangular in outline although its dorsal margin is incomplete, with an arc-like anterodorsal edge and nearly straight posterior and ventral margins. The maxillary fenestra is about 26 mm tall along its posterior margin and about 38 mm long across the center of the fenestra. The interfenestral strut (between the maxillary fenestra and antorbital fenestra) is minimally 32 mm wide (line 3 in figure 2), about 85% of the width of the cranio-caudal length of the maxillary fenestra. This is wider than that of a similar-sized adult specimen of A. libratus (with a maxillary tooth row of about 32 cm in length) and much broader than that of tyrannosaurines such as D. torosus, Tyrannosaurus rex, T. bataar, and Zhuchengtyrannus magnus (see Carr et al., 2005; Hone et al, 2011). As described earlier, the distance between the maxillary fenestra to the ventral margin of the antorbital fossa is about 25 mm (line 4 in figure 2), indicating that the maxillary fenestra is located farther from the ventral margin of the antorbital fossa in contrast to most tyrannosaurines such as D. torosus, T. rex, T. bataar, and Z. magnus. In the antorbital fossa below the antorbital fenestra, no foramen is present; this is a condition hypothesized as a late stage of ontogeny in a tyrannosaurine (Carr et

al., 2017: character 10 in Ontogenetic Character List of Supplementary Information). It is difficult to determine if an accessary maxillary fenestra is present or not due to poor preservation. In anterior view, the ventral portion of the weakly convex lateral border of the maxilla is further expanded posteriorly and slightly medially to form a thin-walled bulla-like structure (Figs. 3, 4), which is comparable to the vesicular bulla as described by Witmer (1997) for many other tyrannosauroids such as A. libratus. It is difficult to determine if the maxilla entered the posterior margin of the external naris between the premaxilla and nasal in life due to the damage along the lateral border of the bone. The dorsal half of the curved portion of the bone slightly expands anteriorly and medially as in D. torosus (CMN 8506) and A. libratus (see Carr et al., 2005: fig. 7). More ventrally, the lateral edge of the anterior surface of the maxilla is incomplete so that the presence of a substantial narial foramen as in some tyrannosaurids (Brochu, 2002) cannot be determined. The medial surface of the maxilla bears a narrow and anterodorsally oriented septum or shelf, which begins near the posterodorsal end of the articular facets of the palatal process for the vomer and the maxilla. This septum is less than four mm wide across its narrowest point which is in sharp contrast to the wide septum of T. rex (see Brochu, 2002: fig. 14B), and it is about 38 mm tall dorsoventrally (Figs. 2E, G; 3A, B). The septum fades as it extends posterodorsally and disappears dorsal to the maxillary antrum (MAT). The septum widens at its base, which is penetrated by a small but deep recess or fossa that is not present in T. rex or it has not been described in other tyrannosauroids when the relevant part is preserved. The promaxillary recess (PMR) anterior to the septum is large and triangular in outline. It is located above maxillary teeth 1 and 2 and ends above maxillary tooth 7 (see lines 5 and 7 in figure 2D). This differs from the condition seen in most tyrannosaurines such as D. horneri or D. torosus where the PMR locates

dorsally between maxillary teeth 3-4 and ends posteriorly dorsally between maxillary teeth 5-6, or above maxillary tooth 2 and ends dorsally between maxillary teeth 5-6, respectively (Carr et al., 2017: figure S2C in Supplementary Information). In T. rex, the PMR is also anteroposteriorly short, located dorsally between maxillary teeth 1-2 and ends dorsally between maxillary teeth 3-4 (Brochu, 2002: fig. 14). The anterior edge of the choana is positioned above maxillary tooth 5 as in D. torosus (line 6 in figure 2), but in contrast to dorsal to maxillary teeth 7 or 4 in D. horneri or T. rex, respectively (Carr et al., 2017; Brochu, 2002). There are three furrows or fossae within the PMR; the ventral and middle furrows are parallel to the anterior edge of the posterodorsal ramus while the dorsal one is in between the anterior edge and the septum (Fig. 4A, B). The medial exit of the PMF is located within the dorsal furrow. In addition, there are two small foramina within the PMR in the area between the middle furrow and the septum. Posterior to the septum is the MAT of the maxilla, which surrounds the maxillary fenestra. Compared with T. rex (Brochu, 2002:fig. 14), the MAT has a subtle dorsal edge (Fig. 3C, D). It is difficult to determine if the MAT had a distinct posterior rim (postantral pillar) due to the poor preservation of the region. The anterior part of the MAT is extensive, nearly as large as the maxillary fenestra. There is no fossa on the ventral part of the interfenestral strut in medial view. The medial surface of the maxilla dorsal to the PMR and MAT are weakly concave. The palatal process starts from the anterior end of the maxilla and extends posteriorly at the end of the preserved portion about 10 mm below the antorbital fenestra (Fig. 3C, D). Anteroventral to the base of the septum, the palatal process forms a sutural area for the contralateral maxilla and the underlapping vomer. The width of the palatal process in this region becomes narrower posteriorly, reducing from 15 mm to 11 mm. More posteriorly, the palatal process extends nearly parallel to the ventral border of the maxillary fenestra and sub-parallel to

the antorbital fenestra. It is not clear if the process maintained its width beyond this point or began to taper due to the damage of the posterior end of the posteroventral ramus. Regardless, it is evident that the posterior part of the palatal process did become subtle, although it is bent dorsally due to damage. In other words, this region of the process does not bulge out to obscure the roots of the posterior teeth as in some tyrannosaurids such as T. rex (Brochu, 2002: fig. 14) and A. sarcophagus (Currie, 2003: fig. 6B). Interdental plates are large and pentagonal. They clearly suture with the maxilla proper whereas they loosely contact each other. Most have fine grooves and ridges running irregularly across their surfaces. In position, the interdental plates nearly reach the ventral edge of the lateral surface of the maxilla, as is seen in adult individuals of T. rex (Brochu, 2002: fig. 14), showing a condition that was considered to represent a late stage of ontogeny in a tyrannosaurine (Carr et al., 2017: character 52 in Ontogenetic Character List of Supplementary Information). The preserved right dentary is about 30 cm long, although its anterodorsal edge and posterior end anterior to the external mandibular fenestra are damaged. It is relatively shallow, about 53 mm high at its lowest point. The dentary slightly bows laterally along its length and its posterior end is slightly expanded ventrally whereas it is strongly expanded dorsally so that its ventral edge is convex anteriorly and slightly concave posteriorly, whereas its dorsal margin is posteriorly deeply concave. The ventral margin of the dentary reaches a maximum width of 21 mm anterior to the middle of the preserved portion; it is 16 mm wide at the anterior end and narrows to just four mm posteriorly. The anterior end is slightly convex. The symphysis is narrow and stops posteroventrally below the third dentary tooth. The symphyseal surface is strongly rugose and beveled, with interlocking ridges and convexities, showing a late stage of

ontogeny as suggested for a tyrannosaurine (Carr et al., 2017: character 115 in Ontogenetic Character List of Supplementary Information). The lateral surface of the dentary is slightly convex dorsoventrally. As with the maxilla, the lateral surface of the dentary is weakly rugose, with faint flutes that are anterodorsoposteroventrally oriented relative to the dorsal margin and become more evident anteriorly (Fig. 4C, D). As in other tyrannosaurids, two distinct longitudinal rows of foramina are present on the lateral face, one dorsal and one ventral row. The ventral row is located along the ventral margin of the bone as in other tyrannosauroids whereas the dorsal row is very low in position, located at the midheight of the lateral surface. This is in sharp contrast with the condition of other tyrannosauroids such as A. montgomeriensis (Carr et al., 2005: fig. 12E), T. bataar (Maleev, 1955), T. rex (Brochu, 2002: fig. 40), and Z. magnus (Hone et al, 2011: Fig. 3) in which the dorsal row is close to the dorsal margin of the bone. It is also different from that of D. torosus (CMN 8506) and Bistahieversor scaleys (Carr and Williamson, 2010: Fig. 10A) in which the dorsal row is positioned on the dorsal half of the bone. The foramina of the dorsal row are normally larger compared to those of the ventral row in size. As in Z. magnus, neither the dorsal nor the ventral foramina have any obvious positional relationship to the spacing of the dentary teeth. The medial surface of the dentary is nearly flat dorsal or ventral to the narrow Meckelian groove, which becomes slightly dorsoventrally taller anteriorly and fades out not close to the symphyseal facet (Fig. 4E, F). The anterior end of the groove is closer to the ventral edge of the dentary than to the dorsal edge, but the groove slopes dorsally as it extends posteriorly and ultimately enters the Meckelian fossa. It is difficult to know whether or not a foramen intramandibularis oralis (see Brochu, 2002: Fig. 41) is present due to some damage of the area

around the anterior end of the Meckelian groove. The bone of the dentary adjacent to the base line of interdental plates is recessed, indicating the sutural surface for the intercoronoid (supradentary), which extends anterior to the 7th alveolus. The incomplete Meckelian fossa is dorsoventrally tall, tapering to a relatively acute end anteriorly, and bordered ventrally by a low rim and dorsally by a more robust ridge that represents the posterior end of the dentary shelf. A narrow and dorsally facing rugose area around the anterior margin of the fossa represents the articular facet of the splenial. The interdental plates are similar to those of the maxilla, although most of them loosely suture with one another. No information can be deduced for posteriorly adjacent bones due to damage. The complete dentition of the upper jaw consists of 13 teeth in life as indicated by the preserved teeth and alveoli of the right maxilla (Fig. 3A-D). The preserved tooth row extends over a distance of around 295 mm, with an estimated five mm of the anterior end missing. The first tooth, as represented by a broken and narrow alveolus, was smaller than the second tooth, which is represented by a broken tooth with an erupting tooth proximally (Figs. 2C, D; 3A, B). Posteriorly, teeth 3, 6, and 8 are complete; of them, the eighth just erupted and was not functional in life. Much of the crowns of teeth 7 and 10 are missing. The last tooth was just beginning to erupt although its crown tip is lost. In medial view, a replacement tooth occurs at the base of alveoli 4 and 11, just between the two adjacent interdental plates. According to the tooth alveoli, the first three teeth are gradually larger posteriorly, teeth 4-7 are similarly large, and the teeth after the seventh become smaller and smaller posteriorly. The tooth crowns are typical of large tyrannosauroids, being large, with relatively sharp tips and sub-oval cross section. The mesial (anterior) edges of the teeth are strongly convex, whereas the distal (posterior) edges are strongly concave at the end below midheight. The labiolingual width is about 85% of the

mesiodistal length, as measured at the midheight of the crown of maxillary tooth 3 (Fig. 3I, J). The complete dentition of the lower jaw is about 308 mm long and contained 16 teeth in life as indicated by the preserved teeth and alveoli of the right dentary. Teeth 5, 6, 8, 9, 11, and 14 are present; of these, the fifth has its top half crown broken away, the ninth was just erupting, and the fourteenth was not functional. The other 10 teeth are missing. The labiolingual width is about 80% of the mesiodistal length, as indicated by the broken crown of right dentary tooth 5 (Fig. 4E, F). In general, the tooth morphology of the dentary differs little from that of the maxillary teeth. Mesial and distal carinae are present in both the upper and lower teeth. As indicated by maxillary tooth 3 and dentary tooth 6, the mesial carina does not extend all the way to the crown base

fading out at one-third of the tooth height before reaching the root (Fig. 3I, J). Maxillary

tooth 3 shows that the mesial carina is subtly lingually positioned before it fades out, showing that the mesial and distal carinae are not symmetrical relative to each other, at least on the first three maxillary teeth. On the fourth and fifth dentary teeth, the carinae are symmetrical relative to each other. Most preserved teeth of the maxilla and dentary have denticles preserved on both mesial and distal carinae. The mesial and distal denticles are equal in size, with 32 per 10 mm as measured in the middle-apical portion of maxillary tooth 5 and dentary tooth 6 (Fig. 5A, B). The denticles become subtly apico-basally larger towards the apex, with 28.6 per 10 mm, whereas they become apico-basally slightly smaller towards the base, with 38 per 10 mm along the mesial carina in both teeth. In labial view, the denticles are oblique relative to the carinae in orientation and they are sub-rectangular in outline. All preserved vertebral centra are damaged in dorsal view (Fig. 6). The best-preserved one is probably the third cervical vertebra, based on the anteroventral position of the parapophysis for the tubercular process of its rib and the anterior location of its pneumatic

foramen (Fig. 6A, B, D, and E). This centrum is anteriorly narrow and posteriorly wide in diameter. In lateral view, the lateral surface bears a large fossa that is penetrated by a pneumatic foramen at its anterior end. The parapophysis for the capitulum of the rib is close to the anteroventral edge of the centrum. The anterior and posterior surfaces of the centrum are concave; the former is oblique, facing anteroventrally, whereas the latter bears a flange-like ventral process. In ventral view, the ventral surface is smooth and does not have a longitudinal ridge or a hypapophysis. The latter is present as a tuber in Xiongguanlong baimoensis Li et al., 2011 (Carr et al., 2017) and it is distinct in derived tyrannosauroids. In more posterior cervical vertebrae, three differences from the third cervical are seen: i.e., both anterior and posterior diameters are similar, the parapophysis is at the anterodorsal edge, and the pneumatic foramen is at the midlength of the centrum (Fig. 6C). As in the cervical vertebra 3, there is no ventral ridge along the midline (Fig. 6F). In the anterior dorsal vertebrae, the parapophysis is at the neural arch, and the pneumatic foramen is small and posterior to the midlength of the centrum (Fig. 6G). In addition, the ventral surface of the centrum is narrower than in the cervicals (Fig. 6J). In the middle-posterior dorsal vertebrae, the most distinct features include the presence of the ventral ridge along the midline and the posterior position of the pneumatic foramen (Fig. 6H, K, L, and I). It is uncertain if the foramen is present in all posterior dorsal centrae due to the absence of those vertebrae. The preserved pelvic bone represents the distal half of the right pubis (Fig. 7). The preserved part of the shaft is mediolaterally narrow and anteriorly concave. It becomes thicker distally. The distal foot, which is well-developed in many tyrannosauroids, is incomplete. The distal end of the posterior process of the foot structure is broken away, but it is evident that the process forms an acute angle, about 70 degrees, relative to the main shaft (Fig. 7H). This is in

contrast to the much wider angle (close to 90 degrees or more) in tyrannosaurids such as A. libratus (Russell, 1970), T. rex (Brochu, 2002), and T. bataar (Maleev, 1974) (Fig. 7 I, J). It is difficult to determine the size of the anterior process of the foot due to damage. According to the thickest places of the broken surfaces in the anterior and posterior processes, the foot appears to have extended from posterodorsally to anteroventrally. In lateral view, the preserved part is slightly convex and the crest for the attachment of the M. puboischiofemoralis externus extends ventrally and ends far from the foot. In medial view, the preserved part is somewhat concave, especially the foot portion.

5. Phylogenetic Relationships In order to establish the phylogenetic position of Jinbeisaurus, we coded Jinbeisaurus into the character matrix of Carr et al. (2017) and then added the newly described tyrannosauroid, Suskityrannus Nesbitt et al., 2019 into the data set. The data set was analyzed by using PAUP* v. 4.a (Swofford, 2003) under a branch-and-bound search with all characters equal weight and 49 characters ordered as in Carr et al. (2017). In the analysis, gaps were treated as missing, multistate taxa were interpreted as uncertainty, furthest addition sequence was applied, intitial maxtrees set was at 100, branches were collapsed if maximum branches had zero lengths, multrees option was in effect, and topological constraints were not enforced. Our analysis found 360 Most Parsimonious Trees (MPTs), each with a tree length of 808 steps, a CI of 0.55, and a RI of 0.81. The topology of the strict consensus of the 360 MPTs is consistent with that of Carr et al. (2017) where Aviatyrannis and Proceratosauridae form a basal polytomy within the monophyletic Tyrannosauroidea and relationships within Proceratosauridae

are resolved. Stokesosauridae and Tyrannosauridae are monophyletic, but the ingroup relationships are unresolved in the former. As in Nesbitt et al. (2019:fig. 4), Suskityrannus is just crownward of Stokesosauridae and forms the sister group of the clade including the mid-grade tyrannosauroids (Sensu Nesbitt et al., 2019) and Tyrannosauridae (Fig. 8). Our analysis considered Jinbeisaurus to be a mid-grade tyrannosauroid and are recovered, with other three medium-sized Asian taxa (Xiongguanlong, Timurlengia Brusatte et al., 2016, and Iren-Dabasu-taxon) and three large North-American taxa (Dryptosaurus, Appalachiosaurus, and Bistahieversor), in a polytomy, phylogenetically more basal than Tyrannosauridae, but crownward relative to Suskityrannus. This is supported by 12 synapomorphies including the following four unambiguously optimized character states, which are all seen in Jinbeisaurus. They include the maxillary fenestra with a V-shaped caudal margin (character 28.1), the convex ventral margin of the maxilla (character 39.1), the caudal region of the main body of the maxilla tapering in depth caudally in lateral view (character 48.1), and the antorbital fossa covering the 50 -60% of the main body under the midpoint of the internal antorbital fenestra in lateral view (character 50.1).

6. DISCUSSION

6.1. Size of the skull of Jinbeisaurus wangi As described earlier, the tooth row of the right maxilla is nearly complete, about 30 cm long (with the preserved length of 29.5 cm and a missing length of 5 mm). It appears evident that the length of the maxillary tooth row does not grow isometrically to that of the skull in

Tarbosaurus. The maxillary tooth row is proportionally shorter with growth; it occupies about 49% of the skull length in a juvenile with a skull length of 29 cm (see Tsuihiji et al., 2011: fig .2) and decreases to 45% into an adult skull with a skull length of 122 cm (Tsuihiji et al., 2011: fig. 1C). Following this comparison, the skull of Jinbeisaurus may have reached a length of about 66 cm, close to that of Xiongguanlong, representing another small to medium-sized theropod, much smaller than derived tyrannosauroids, such as Dryptosaurus, Appalachiosaurus, Bistahieversor, and Tyrannosauridae.

6.2. Adulthood of the holotype The uneven and broken dorsal surfaces of all preserved centra indicate that these centra most probably had their neural arches tightly sutured or even fused when complete, as in an adult. If these centra came from a juvenile individual, the neural arch should have loosely articulated with and be easily separable from the centra, leaving an evident sutural facet of a distinct pattern on the dorsal surface of each centrum. Therefore, the holotype probably represent an adult individual. The adulthood of the new taxon is also evident in some of other features, such as the following: in adults of D. horneri (Carr et al., 2017) and T. bataar (Currie, 2003: fig. 3G), the position of the PMF is hardly visible in lateral view, which is also true in the new taxon. The absence of the fenestrae in the ventral part of the antorbital fossa below the antorbital fenestra and in the dentary, the strongly rugose and beveled symphyseal surface with interlocking ridges and convexities, are adult features in D. horneri (Carr et al. (2017), which are seen in J. wangi. It is therefore reasonable to hypothesize that the holotype of the new taxon was an adult.

6.3. Phylogenetic comments Compared with some of the other more derived clades, the status of a mid-grade tyrannosauroid for Jinbeisaurus is relatively robust, supported by four unequivocal synapomorphies. As suggested by the Majority-Rule consensus of 360 MPTs, Xiongguanlong may have been phylogenetically the basalmost within the mid-grade tyrannosauroids as hypothesized by Carr et al. (2017). Jinbeisaurus is, with Timurlengia and the Iren-Dabasu-Taxon, a member of the derived mid-grade tyrannosauroids in that they share with the later ecologically dominant tyrannosaurids the ventrally convex alveolar margin of the maxilla and complementarily concave margin of the dentary, and the asymmetrical carinae of the teeth. The new taxon emphasizes the evolutionary importance, longevity, and wide distribution of this intermediate grade of small to medium-sized tyrannosauroids, which includes Asian taxa such as Xiongguanlong, Timurlengia, and the North American Moros (Zanno et al., 2019) that together form a clear morphological bridge between the basal-most Jurassic forms and the Late Cretaceous giants.

6.4. Comments on the gigantism of Tyrannosauroidea It appears that gigantism in tyrannosauroids first evolved in North America before the transgression of the Western Interior Seaway (WIS), which isolated populations in Appalachia (in the east) from those in Laurasia (in the west). Global oceanic drawdowns united Laurasia and Asia by ~80 million years ago, which resulted in dispersal of two ancestral stocks of tyrannosaurine from Laurasia to Asia that culminated in Alioramus, on the one hand, and the

Zhuchengtyrannus + Tyrannosaurus clade on the other. Intermediate grade tyrannosauroids are unknown from Late Cretaceous sediments of central Asia; presumably, they went extinct by the time when giant North American tyrannosaurines dispersed from Laurasia, replacing the allosauroids as top predators and effacing, momentarily, tyrannosauroids from the role of lowertier predators until the Alioramus lineage reached an apomorphically small adult size.

6.5. Comments on the assignment of theropod teeth from KDLQ of HDU. As mentioned earlier, Pang and Cheng (2000) considered the several theropod teeth from the KDLQ of HDU as cf. Szechauanosaurus campi based on similar morphology to those theropod teeth (IVPP V 756, V757-V761, V 764-V766, and V 783-785) from the Upper Cretaceous of Shandong Province. Young referred those Shandong teeth as cf. S. campi in 1958. Our examinations of those teeth from Shandong and the teeth of HDU did not support the assignments made by Young (1958) nor by Pang and Cheng (2000). Young (1942) erected S. campi originally based on six incomplete theropod teeth from the Upper Jurassic of Guangyuan (Kuangyuan), Sichuan Province. Unfortunately, we only found one tooth (IVPP V 235) in the IVPP collections and the others are reported missing. It is very clear that the teeth of J. wangi are different from those from the KDLQ of HDU although they both came from the similar horizons of two close localities within five km apart. Both upper and lower teeth of J. wangi have 16 to 16.2 denticles in five mm on both mesial and distal carinae of the mid-upper crown (Fig. 5A, B), while the teeth of the KDLQ of HDU separately have 15.8 mesial and 20.5 distal denticles in five mm of a similar portion of the crown (Fig. 5C). In the Shandong teeth of Young (1958), the five mm of a similar portion of the crown

have only 12 to 13 denticles on both mesial and distal carinae (Fig. 5. D, E), which differs from the teeth of J. wangi and the teeth from the KDLQ of HDU. The type tooth (IVPP V 235) of S. campi is different from those of all aforementioned; the mesial five mm have only 8.5 denticles in the mid-upper portion of the crown (Fig. 5F). The distal carina was incomplete in IVPP V 235, but as Young (1942) described, the distal denticles of other teeth are coarser than the mesial. This means that the mesial five mm should have had fewer than 8.5 in S. campi. The above comparison indicates that those teeth from Shandong cannot be assigned to S. campi of the Upper Jurassic and that the teeth of the KDLQ of HDU also cannot be referred to S. campi or a same taxon represent by the Shandong teeth. Finally, the theropod teeth from the KDLQ of HDU are also different from those of J. wangi, which suggests that there would have been two taxa of theropod dinosaurs in the Upper Cretaceous in Tianzhen and nearby. It should be mentioned here that Holtz et al. (2004) considered S. campi as a nomina dubia of Tetanurae.

7. Conclusions Discovery of J. wangi establishes the first diagnostic theropod dinosaur found in Shanxi Province. This discovery allows testing not only phylogenetic relationships of a grade of small to medium-sized theropods and also the evolutionary longevity and wide distribution of these tyrannosauroids. For a better understanding of J. wangi in morphology, additional and betterpreserved materials are crucial for future fieldwork. As suggested by the phylogenetic pattern of Tyrannosauroidea established in this study, J. wangi and X. baimoensis should have had filled two successive gaps within the grade of small to medium-sized tyrannosauroids. However, this cannot be confirmed in terms of the uncertain

relationships of the two Chinese taxa and other mid-grade tyrannosauroids within Tyrannosauroidea. To solve this problem have to wait for additional specimens of those poorly represented mid-grade tyrannosauroids to discover. As discussed above, there may have been two kinds of theropod dinosaurs in Tianzhen and neighboring areas in the Late Cretaceous.

Acknowledgments We are grateful to F. Zheng and B.-H. Geng of IVPP and Q.Q Pang and W.-S. Wu of HDU for their help during X.-C. Wu’s study of the relevant theropod teeth under their care. We also thank Z.-L. Tang of IVPP and S.-Z. Wang (SMG) for their assistance in the fieldworks and the paleontological crew of SMG for discovering, excavating, and preparing the specimen. D.W.E. Hone (Queen Mary University of London) provided us information on Zhuchengtyrannus. X.-C Wu wants to express his appreciation to the paleontological crew of SMG for their hospitality during his visits. We appreciate two anonymous referees carefully reviewed the manuscript, offering critical comments and suggestions that led to its great improvement. This work was supported by grants from the Department of Land and Resources of Shanxi Province and from the Canadian Museum of Nature (RS09 to X.-C.W.).

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Figure Captions Fig. 1. Geographic map of China. A, Showing the holotype locality of Jinbeisaurus wangi gen. et sp. nov. near Yangjiayao, Tianzhen County, Shanxi Province, China. B, A photo showing the quarry from which the holotype was collected. SCIS indicates South China Sea Islands. Fig. 2. Stratigraphic section measured in the locality of Jinbeisaurus wangi gen. et sp. nov. Stratum 9 is the level where the specimen was recovered. Fig. 3. Maxillae of Jinbeisaurus wangi gen. et sp. nov. A-D, The right maxilla in lateral and medial views, respectively. E-H, The preserved portion of the left maxilla in lateral and medial views, respectively. I, J, Maxillary tooth 3 in lingual view, showing the somewhat lingual positioned mesial carina. Zigzag lines indicate broken areas. Lines 1 and 2 show the vertical distances of the ventral part of the antorbital fossa ventral to the maxillary fenestra and posterior to the tooth row below the antorbital fenestra, respectively. Line 3 indicates the narrowest cranio-caudal distance of the interfenestral strut. Line 4 is the horizontal distance between the anterior-most edge of the maxillary fenestra and the anterior edge of the antorbital fossa. Lines 5 and 6 indicate the anterior limits of the promaxillary recess (sinus) and the choana, respectively. Line 7 indicates the posterior limit of the promaxillary recess. Abbreviations: anof, antorbital fossa; aof, antorbital fenestra; ifs, interfenestral strut; lth, last tooth; mat, maxillary antrum of maxilla; mc, mesial carina; mxf, maxillary fenestra; pmf, promaxillary fenestra; pmr, promaxillary recess; sbr, septum between promaxillary recess and maxillary antrum of maxilla; th3, maxillary tooth 3.

Fig. 4. Right maxilla and dentary of Jinbeisaurus wangi gen. et sp. nov. A, B, The anterior portion of the right maxilla in anterodorsomedial view. C-F, The right dentary in lateral and medial views, respectively. G and H, Close-up of the anterior portion of the right dentary in laterodorsal views, showing the first four alveoli. Zigzag lines indicate broken areas. Abbreviations as in figure 2 plus afn, anterior facet for nasal; ath 1-4, anterior teeth 1-4; dfpr, dorsal fossa of promaxillary recess; fvm, facets for vomer and maxilla; idp, interdental plates; mef, Meckelian fossa; meg, Meckelian groove; mfpr, middle fossa of promaxillary recess; rs, recess; rth. replacement tooth; sfd, symphyseal facet of dentary; sfsp, sutural line for splenial ; th, tooth; vb, vestibular bulla; vfpr, ventral fossa of promaxillary recess; vssd, ventral suture for supradentary. Fig. 5. Tooth denticles of some relevant theropod dinosaurs found in China. A, B, Maxillary tooth 5 and dentary tooth 6 of Jinbeisaurus wangi gen. et sp. nov., respectively. C, One of several theropod tooth crowns collected from KDLQ, as referred to cf. S. campi by Peng and Cheng (2001). D, E, Two (IVPP V 759, V 757) of the seven theropod teeth as referred by Young (1958) to cf. Szechuanosaurus campi Young, 1948. F, The type (IVPP V 235) of Szechuanosaurus Campi, 1948 (the only remaining tooth on which the taxon was established). Fig. 6. Some vertebrae of Jinbeisaurus wangi gen. et sp. nov. A-E, An anterior cervical vertebra in right lateral and ventral views, respectively. C and F, A posterior cervical vertebra in right lateral and ventral views, respectively. G and J, An anterior dorsal vertebra in left lateral and ventral views, respectively. H-L, Two mid-posterior dorsal vertebrae in left lateral and ventral views, respectively. Abbreviations: pap, parapophysis; pnf, pneumatic foramen.

Fig. 7. The preserved right pubis of Jinbeisaurus wangi gen et sp. nov. A-D, Lateral and medial views, respectively. E-G, anterior, distal, and posterior views, respectively. H, outline of A, showing the angle between the foot and the shaft; I, J, distal portions of the pubes of Tyrannosaurus rex (modified from Brochu, 2002: fig 90) in right lateral view, showing the angle between the foot and shaft. Zigzag lines indicate broken areas. Abbreviations: cpife, crest

for the attachment of the M. puboischiofemoralis externus; pu, pubis.

Fig. 8. The Majority-Rule consensus tree of 360 MPTs obtained by our analysis. Clades with a support higher than 50% are marked in parentheses and numbers by clades are Bootstrap support values. Jinbeisaurus was coded into the character matrix (386 characters) of Carr et al. (2017) (???????????????????00000?0?10?00??00?011010011?10100????????????????????????? ????????????????????????????????????????????????????????????????????????????????? ???????????????????????????????????????????????????????????????????????110?01110 ??????????????????????010100?????????????0?????0???????????????????????????????? ?????????????????????????1??????????????????????????????????????????). In character coding for Suskityrannus (0???00??????102001???001?0?0??00??0???0?0?0011?0?0??????????????????????????? ?????????????????????????????????????????????????????????????????????????00?0?10 010???????????????????0?????????????????????????????????????????????????????0??1 ?021??1????11???????1?10??0?0??????????1?0111??0010??????0???????????????????? ????????????????????????????1??????????????00110?11?0?1101?111110?1????), 366 characters are coded following those of Nesbitt et al. (2019) and 20 character are coded

based on the published figures of Nesbitt et al. (2019). Unequivocal synapomorphies, as optimized under accelerated (ACCTRAN) transformation assumption in tree 1 of the 360 MPTs, are listed for Maniraptoromorpha (characters: 21.0, 41.0, 66.0, 73.0, 90.0, 115.1, 350.0), Tyrannosauroidea (characters: 13.1,15.1, 18.2, 30.1, 103.1, 132.1, 164.1, 209.1, 233.1, 257.1, 259.1, 282.1, 311.1, 324.1, 343.1, 345.1, 358.1, 361.1, 362.1), Proceratosauridae (characters: 5.1, 16.1, 17.1, 49.1, 55.1, 157.1, 158.1, 234.1, 247.1, 330.1), Stokesosauridae (characters: 325.1, 330.1, 340.1, 342.1), Suskityrannus + more derived taxa (characters: 15.2, 370.1, 377.1, 378.1, 379.1, 382.1), ‘Mid-grade’ tyrannosauroids + (Dryptosaurus, Appalachiosaurus, and Bistahieversor) + Tyrannosauridae (Characters: 28.1, 39.1, 48.1, 50.1), Tyrannosauridae (characters: 31.1, 68.1, 100.1, 111.0, 124.1, 176.1, 182.1, 184.1), and Tyrannosaurinae (characters: 14.2, 40.1, 54.1, 81.1, 123.1, 125.1, 131.1, 174.1, 177.1, 178.1, 188.1, 216.1, 283.2, 295.1).

It is to certify that this work has no interests to declare.

Xiao-Chun Wu and co-authors