Available online at www.sciencedirect.com ScienceDirect Palaeoworld 23 (2014) 200–208 Theropod and possible ornithopod track assemblages from the Jurassic–Cretaceous boundary Houcheng Formation, Shangyi, northern Hebei, China a,∗ b b c a Li Da Xing , Yong Qing Liu , Hong Wei Kuang , Hendrik Klein , Jian Ping Zhang , d b b a Michael E. Burns , Jun Chen , Ming Wei Wang , Jian Hu a School of the Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China b Institute of Geology, Chinese Academy of Geological Science, Beijing 100037, China c Saurierwelt Paläontologisches Museum, Neumarkt, Germany d Department of Biological Sciences, University of Alberta, 11455 Saskatchewan Drive, Edmonton, Alberta T6G 2E9, Canada Received 11 July 2013; received in revised form 19 September 2013; accepted 11 October 2013 Available online 21 October 2013 Abstract Dinosaur track assemblages from the Houcheng Formation in the small continental Shangyi Basin of northern Hebei Province, China bridge a gap in the record of vertebrates from this unit and enrich our knowledge of ichnofaunas from the Jurassic–Cretaceous boundary. Their stratigraphic position between the Middle Jurassic Yan-Liao Biota and the Lower Cretaceous Jehol Biota gives them a special importance. New discoveries allow a re-assessment of theropod and possible ornithopod tracks that are present with several trackways. Seventy-three footprints were exam- ined and documented. Despite their smaller size, the tridactyl mesaxonic theropod tracks show morphological similarities with the ichnogenus Therangospodus known from the Upper Jurassic deposits of North America, Europe, and Central Asia. The possible ornithopod tracks lack an associated manus imprint, suggesting a bipedal trackmaker. These possible ornithopod tracks from the Houcheng Formation provide evidence for the presence of small basal ornithopods or basal Cerapoda in the Upper Jurassic–Lower Cretaceous in this region. The depositional environment was the margin of an extensive shallow lake with fluctuating water levels under seasonally dry climate. © 2013 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved. Keywords: Theropod tracks; Possible ornithopod tracks; Jurassic–Cretaceous boundary; Houcheng Formation; Shangyi 1. Introduction To date at least ten tracksites have been discovered in Houcheng/Tuchengzi Formation strata (Houcheng Formation Vertebrate fossils from the Upper Jurassic–Lower Cretaceous from Hebei Province = Tuchengzi Formation from Liaoning Houcheng Formation (= Tuchengzi Formation) are rare; there- Province). Abundant dinosaur tracks have been described, fore, the dinosaur tracks from these strata are important (Zhang including those of theropods such as Anchisauripus isp. et al., 2012) specifically because of their stratigraphic position (Sullivan et al., 2009), Grallator type (Yabe et al., 1940; between the Middle Jurassic Yan-Liao Biota (comprising the Jiu- Shikama, 1942; Young, 1960; Zhang Y.Z. et al., 2004; longshan and Tiaojishan formations) and the Lower Cretaceous Matsukawa et al., 2006; Fujita et al., 2007; Xing et al., 2011; Jehol Biota (comprising the Zhangjiakou, Dabeigou, Yixian, and Zhang J.P. et al., 2012), Megalosauripus isp. (Xing et al., 2011), Jiufotang formations). Both biotas are famous for their feath- Menglongipus (Xing et al., 2009), and Therangospodus isp. ered dinosaurs, primitive birds, mammals, pterosaurs, fishes, and (Xing et al., 2011). Other known ichnofossils are rare theropod insects. swim tracks (Xing et al., 2011) and a crouching trace (Xing et al., 2012), as well as the avian ichnite Pullornipes (Lockley et al., 2006). In 2012, hundreds of thyreophoran (cf. Deltapodus isp.), theropod, ornithopod, and sauropod tracks were discovered in ∗ Yanqing, Beijing (Zhang et al., 2012) (The present study shows Corresponding author. Tel.: +86 139 107 33464. that these thyreophorans can be interpreted as poorly-preserved E-mail address: [email protected] (L.D. Xing). 1871-174X/$ – see front matter © 2013 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights reserved. http://dx.doi.org/10.1016/j.palwor.2013.10.002 L.D. Xing et al. / Palaeoworld 23 (2014) 200–208 201 sauropod tracks; these specimens will be published elsewhere). Description Other theropod and questionable sauropod (possible ornitho- Originally upon discovery, there were 71 theropod tracks at pod, too; see section 4.2. in this paper) track assemblages were the tracksite (Liu et al., 2012). However, with more than one described from Shangyi, Hebei Province (Liu et al., 2012). These year of weathering, some tracks are now indistinct and bro- abundant dinosaur and bird track assemblages have bridged the ken. Furthermore, new tracks were discovered in April 2013 on gap in the vertebrate fossil record of the Houcheng/Tuchengzi which the descriptions herein are based. Except for four speci- Formation. In 2013, the first author and Liu Y.Q.’s team inves- mens (SYT43–46), the theropod tracks at Shangyi tracksite are tigated the Shangyi tracksite again. Here we redescribe these generally of the same size and morphology. tracks based on the newly collected data. SYT53 (Fig. 4) is the best-preserved imprint. The digit III trace is directed anteriorly and the longest, whereas that of digit 2. Institutional abbreviations II is shorter than digit IV. Digit II possesses two phalangeal pad traces, and digits III and IV, three phalangeal pad traces. Claw IVPP = Institute of Vertebrate Paleontology and Paleo- marks are distinct. The metatarsophalangeal region lies nearly in anthropology, Chinese Academy of Sciences, China. line with the long axis of digit III. SYT53 has two distinct circular SY = Shangyi tracksite, Zhangjiakou City, Hebei Province, metatarsophalangeal pad traces, a smaller one corresponding to China. YQS = Yanqing tracksite, Beijing City, China. digit II and the other, larger one corresponding to digit IV. The metatarsophalangeal pad trace of digit II is connected to the trace 3. Geological setting of the first pad of digit II via an inter-pad space and also in contact with the metatarsophalangeal pad of digit IV. The divarication ◦ ◦ The Shangyi tracksite (GPS: 40 56 36 N, 114 15 44 E) lies angle between digits II and III is almost equal to that of digits III 7 km north of Xiaosuangou Town in Shangyi Country, Zhang- and IV. SYT51–53 constitute one distinct trackway (Fig. 3C). ◦ jiakou City, northwestern Hebei Province (Fig. 1). The Shangyi The mean pace length is 108 cm and the pace angulation 166 . Basin has been a small continental basin since the late Mesozoic The specimens SYT7, 14, 20, 30, 34, 40, 50, and 52 (Fig. 5) and includes the Archean–Proterozoic, Mesozoic and Cenozoic are well-preserved, similar to SYT53. The metatarsophalangeal strata. pad of digit IV is nearly in line with the axis of digit III, such as Historically, the Upper Jurassic to Lower Cretaceous stratal in T14, 34, 40, but in others it is slightly displaced. The borders sequences in the Western Hills of Beijing and in Hebei Province between the metatarsophalangeal pad traces of digits II and IV have been assigned to the Houcheng Formation, whereas those are shallow. in Liaoning Province have been referred to as the Tuchengzi For- The mean divarication angle between the traces of digits II ◦ ◦ mation. The term Houcheng is preferred in the present paper. The and IV of the Shangyi theropod tracks is 54 , ranging from 43 ◦ age of the aeolian sand bed mixed with tuff of the third member to 61 , and the divarication angles between digits II and III are on (dinosaur track layer) of the Tuchengzi Formation in Beipiao average larger than those between digits III and IV. The imprints and Chaoyang, in the northern Liaoning Province, is 137 Ma have a mean length width (L/W) ratio of 1.66 (N = 38), and the based on SHRIMP zircon U-Pb (Xu et al., 2012). Swisher et al. mean L/W ratio of the anterior triangle is 0.69 (N = 36) (Fig. 4), (1999) have dated the plagioclase Ar-Ar from the tuffs under the indicating moderate mesaxony, unlike the strong mesaxony typ- dinosaur track layer from Beipiao in the northwestern Liaoning ical of the Grallator type (Lockley, 2009). Province at 139 Ma. The dinosaur tracks were found in the rhyth- SYT43–46 (Figs. 3B, 6) are tracks that were likely revealed mically deposited siltstone and fine sandstone from the upper by recent weathering because Liu et al. (2012) did not report member of the Houcheng Formation. Its age is probably early them. The average length of SYT43–46 is 4.9 cm. The four Early Cretaceous (Liu et al., 2012). footprints constitute one trackway. SYT45 (Fig. 6) is the best- Irregularly and cresentic ripples are also developed within the preserved and similar in morphology to the large-sized theropod footprint layer (Fig. 2E) along with different sized mud cracks, tracks represented by SYT53. The border between the metatar- raindrop imprints, and invertebrate burrowing traces and bur- sophalangeal region and digits II and IV is indistinct. Distinct rows. The sedimentary facies indicate that they were formed claw marks are preserved. The L/W ratio of the anterior triangle near the edge of an extensive, shallow lake within a seasonal, is 0.62, the mean pace length 30 cm, and the pace angulations ◦ drought environment (Liu et al., 2012). range 173 . Comparison and discussion 4. Ichnology Tridactyl tracks such as those from Shangyi were typically left by bipedal theropods. 4.1. Theropod tracks In size, the Shangyi theropod tracks (mean length 16 cm) are similar to Anchisauripus isp. (Sullivan et al., 2009), Grallator Material. At least 54 complete natural molds cataloged as morphotype type B and C (Fujita et al., 2007), and Theran- SYT1-54 (Figs. 2C, D, 3A–C, 4–6; Table 1). These original gospodus isp. (Xing et al., 2011) from the Tuchengzi Formation. tracks were not collected and are still in situ. However, the materials of Anchisauripus isp. from the Nan- Locality and horizon. Houcheng Formation, Lower Cre- shuangmiao tracksite described by Sullivan et al.