Cretaceous Research 65 (2016) 213e222 Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes A theropod track assemblage including large deinonychosaur tracks from the Lower Cretaceous of Asia * Lida Xing a, , Martin G. Lockley b, Hendrik Klein c, Guangzhao Peng d, Yong Ye d, Shan Jiang d, Jianping Zhang a, W. Scott Persons IV e, Ting Xu f a School of the Earth Sciences and Resources, China University of Geosciences, Beijing, 100083, China b Dinosaur Tracks Museum, University of Colorado Denver, PO Box 173364, Denver, CO, 80217, USA c Saurierwelt Palaontologisches€ Museum, Alte Richt 7, D-92318, Neumarkt, Germany d Zigong Dinosaur Museum, Zigong, 643013, Sichuan, China e Department of Biological Sciences, University of Alberta, 11455 Saskatchewan Drive, Edmonton, Alberta, T6G 2E9, Canada f Xiangnan Primary School, Guihua Township, Gulin County, Sichuan Province, 646527, China article info abstract Article history: A total of more than 40 tridactyl and didactyl tracks were preserved as natural casts on four fallen blocks Received 29 February 2016 of sandstone representing the Lower Cretaceous Jiaguan Formation of Gulin County in southeastern Received in revised form Sichuan Province, China. While several trackways can be distinctly followed, others are isolated imprints 5 May 2016 only. All have been flattened by overburden pressures. Tridactyl tracks are present with three size-classes Accepted in revised form 8 May 2016 being <10 cm, 10e20 cm and >20 cm in length. Morphologically they are similar to the ichnogenus Available online 10 May 2016 Eubrontes, considering the relatively weak mesaxony. Eight of the tracks on one of the blocks are clearly didactyl and are here interpreted as representing large and medium sized dromaeosaurids. The largest Keywords: Deinonychosaur track is about ~30 cm long and comparable in size to the type of Dromaeopodus (~28 cm), from the Lower Theropod Cretaceous of Shandong Province, which was the largest dromaeosaurid track previously reported. This Footprints report adds new data to the growing number of dromaeosaurid tracksites reports from China, and from Jiaguan Formation the Jiaguan Formation, suggesting that this theropod group had a preference for fluvial Lower Cretaceous paleoenvironments. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction dromaeosaurid and troodontid subclades, which are characterized by an enlarged and strongly curved claw on digit II. This claw could Lower Cretaceous theropod track assemblages with tridactyl be retracted and held in a raised hyperextended position (Turner representatives are common and widespread, whereas the pres- et al., 2012), and exquisitely preserved specimens of troodontids ence of didactyl (deinonychosaur) tracks are mostly considered a such as Mei long and Sinornithoides youngi reveal that digit II was peculiar feature. In this study we document both tridactyl tracks of held in this raised position even while a deinonychosaur was at rest the Grallator-Eubrontes plexus and didactyl forms co-occurring on (Xu and Norell, 2004). the same surfaces. The didactyl tracks have a great length indi- Most Cretaceous deinonychosaurian skeletal fossils from China cating the presence of large deinonychosaurs in the Jiaguan have been discovered from the Jehol Biota (Xu et al., 2003), in the Formation. area formerly called Jehol (now northern Hebei Province, western Deinonychosauria (Colbert and Russell, 1969) is a diverse clade Liaoning Province and eastern Inner Mongolia). The body fossil of theropod dinosaurs, and includes many famous Cretaceous record of deinonychosaurians is so especially rich in the Jehol re- predators like Troodon (Leidy, 1856), Velociraptor (Osborn, 1924), gion that the Shandong Tianyu Museum of Nature alone possesses Deinonychus (Ostrom, 1969), Utahraptor (Kirkland et al., 1993), and about 700 specimens (Xing et al., 2015b). However, owing perhaps Microraptor (Xu et al., 2000). Deinonychosauria is comprised of the to the relative small size of most deinonychosaurians, their fossil record is scarce in other parts of China. However, the fossil track record has provided an important supplement to the known di- * Corresponding author. versity and abundance of the Deinonychosauria throughout China, E-mail address: [email protected] (L. Xing). and suggests that the sickle-clawed predators were more prevalent http://dx.doi.org/10.1016/j.cretres.2016.05.003 0195-6671/© 2016 Elsevier Ltd. All rights reserved. 214 L. Xing et al. / Cretaceous Research 65 (2016) 213e222 than the skeletal record alone might suggest. For example, prior to Institutional abbreviations and acronyms this study Lockley et al. (2016a,b) identified at least 16 unequivocal L/R ¼ Left/right; T ¼ Theropod; LB ¼ Leibei tracksite, Gulin, examples of deinonychosaurian tracksites of which the majority (9) Sichuan Province, China. originate from the Lower Cretaceous of China. Whereas footprints of dinosaurs from the Jiaguan Formation are well-preserved and abundant, their skeletons are all fragmentary 2. Geological setting and extremely rare. Zhen et al. (1994) first reported dein- onychosaurian tracks from the Jiaguan Formation, in the E'mei The Sichuan Basin is known for its large exposures of thick Region of the Sichuan Basin. Since 1994, two sites in the Jiaguan Mesozoic continental red beds (Gu and Liu, 1997). The Cretaceous Formation with Velociraptorichnus isp. and Velociraptorichnus sedimentary sequences consist of the Jiaguan Formation and the zhangi (Xing et al., 2015b), and one site in the Feitianshan Forma- underlying Guankou Formation. Sandstones are prominent in the tion, southern Sichuan Basin, with cf. Dromaeopodus (Xing et al., former and mudstones in the latter. The majority of the Cretaceous 2016), have been reported. Both are in the Lower Cretaceous. tracks are known from the Jiaguan Formation. The Jiaguan Forma- These tracks are the only record of deinonychosaurians in the tion is comprised primarily of meandering river deposits inter- Sichuan Basin and the Mishi (Xichang)-Jiangzhou Basin. The Jia- bedded with occasional anastomosing river deposits in the upper guan and Feitianshan formations are Type 1 and Type 2 deposits member that was formed under semi-arid and semi-humid cli- respectively (sensu Lockley, 1991; Lockley et al., 1994) in which matic conditions in a tropical or subtropical climate (Chen, 2009; tracks represent the only tetrapod evidence (Type 1) or in which see also; Wang et al., 2008). A set of thick, brick-red, feldspathic, tracks dominate over body fossils (Type 2). quartz sandstones are highly characteristic of the Jiaguan Forma- In recent years, a number of dinosaur tracksites have been found tion (Sichuan Provincial Bureau of Geology aviation regional in the Gulin region, including the Hanxi tracksite which contains Geological Survey team, 1976). The large thick sandstones pro- the longest theropod trackway from East Asia, and a diverse duce large track-bearing blocks that contain well-developed sauropod-, theropod-, and ornithopod-track assemblage (Xing wedge-shaped cross-stratification. On the track-preserving sur- et al., 2015c). The Shimiaogou tracksite, which is 3.5 km away faces, mud cracks can be seen. Recent pollen studies indicate that from the Hanxi tracksite, also contains a diverse track assemblage, the Jiaguan Formation is BarremianeAlbian (Chen, 2009). The Lei- including theropod, sauropod, ornithopod, and pterosaur foot- bei tracksite (Fig. 2) is a collapsed sandstone locality in the upper prints. In fall of 2015, Xu Ting, a resident in Guihua Township of member of the Jiaguan Formation, and the collapsed blocks can be Gulin region, found another dinosaur tracksite in Leibei of Guihua traced to their original level. A more detailed list and overview of (GPS: 2814022.9100,10539014.4000; Fig. 1). In November of 2015, Xu Lower Cretaceous units in southwestern China and the present Ting and the Guihua Township Government invited some of the footprint taxa is given in Xing and Lockley, in press. authors (LX, GP, YY, and SJ) to conduct a formal scientific investi- gation on these newly discovered tracks. The Leibei tracksite 3. Materials and methods mainly yields tridactyl and didactyl theropod tracks, with unusual preservation. In the following we give a detailed description of this The Leibei tracksite is situated in Leibei, Hanxi Village, Gulin assemblage and discuss paleoecological implications. County, within Guihua River Valley. Many tracks have been found Fig. 1. Geographical setting showing the location (star icon) of the Leibei tracksite in Gulin County, Sichuan Province, China. L. Xing et al. / Cretaceous Research 65 (2016) 213e222 215 Fig. 2. General view of outcrop at the Leibei tracksite (A), close-up of the original track layer (B), arrows (C) indicate a thin muddy siltstone layer, outline drawing notes flattened track cast. on collapsed rocks along the Guihua Creek, and the original levels h ¼ hip height [based on the methods proposed by Alexander of the tracks can be traced on rock sections beside the road, 10 m (1976) and Thulborn (1990)]. Moreover, in order to determine away. whether the trackmaker was walking, trotting or running, relative Collapsed blocks are common at the Leibei tracksite and are stride length (SL/h) was calculated using the method of Thulborn scattered along the roadway on one side of the creek. Most of the (1990). blocks are covered with moss. At least four large blocks preserve Four well-preserved track-bearing blocks were