New Fossils of Sambar (Rusa Unicolor) from Bailong Cave, a Middle Pleistocene Human Site in Hubei, China T
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Quaternary International 550 (2020) 120–129 Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint New fossils of sambar (Rusa unicolor) from Bailong Cave, a Middle Pleistocene human site in Hubei, China T ∗ Bei Zhanga,b,c, , Haowen Tonga,b,c a Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 100044, China b CAS Center for Excellence in Life and Paleoenvironment, Beijing, 100044, China c University of Chinese Academy of Sciences, Beijing, 100049, China ARTICLE INFO ABSTRACT Keywords: The sambar (Rusa unicolor) is among the main elements of the Oriental Realm. The sambar fossils unearthed Antler from Bailong Cave site dated back to the Middle Pleistocene were better preserved than those from any other Bony labyrinth fossil site. We described these remains especially focusing on the deciduous teeth and petrosal bone as well as the Dentition bony labyrinth which have never been studied before. The measurements of antler and cheek teeth fall within East Asia the range of intraspecific variations of extant specimens. The sambar's antler and cheek teeth differ from other Petrosal bone allied cervids in having more rugose three-tined antlers, thicker enamel of cheek teeth, and in possessing tapered Rusa yunnanensis entostyles on upper molars and stout anterior ectostylid on dp4. The petrosal bone is similar to that of the extant sambar in 3D reconstructions, but different from those of Cervus nippon and Axis axis. The differences are mainly related to the size and overall shape of petrosal bone as well as the dorsolateral outline of tegmen tympani. There are variations in the shape of internal acoustic meatus and subarcuate fossa as well as the position of hiatus Fallopii between extant and fossil sambar specimen. The bony labyrinth of sambar resembles that of Javan deer (Rusa timorensis), while the shape of endolymphatic sac of sambar is paddle-like instead of funnel-like as in R. timorensis. R. unicolor maybe originated from southern China during Mid-Pleistocene Transition, and we pro- visionally regard Rusa yunnanensis rather than Rusa elegans as the direct ancestor of sambar based on the morphological characters of antler and tooth. 1. Introduction recognized currently (Mattioli, 2011; Hedges et al., 2015; MacKinnon et al., 2015; Timmins et al., 2015; Brook, 2016). There are a lot of fossil Cervidae is the second most diverse family among terrestrial artio- sites with Rusa fossils unearthed in China (Fig. 1). The earliest fossil dactyls with more than 50 extant species that widely distribute across record of Rusa in China was from the Mazegou Formation (Late Plio- Eurasia and the Americas (Groves and Grubb, 2011; Mattioli, 2011). cene) of Yushe Basin (Flynn et al., 1991; Tedford et al., 1991). The The systematics and phylogeny of Cervidae have been debated for over genus Rusa was distributed both in North and South China during the one century, and morphology and molecular biology failed to produce Early Pleistocene, but after that period they retreated to the southern the same results (e.g. Brooke, 1878; Pitra et al., 2004; Gilbert et al., part of Asia and became one of the dominant elements of the Oriental 2006; Hassanin et al., 2012; Mennecart et al., 2017; Heckeberg and Realm (Dong, 1993). In the fossil records, six species of Rusa (R. mi- Wörheide, 2019; Zurano et al., 2019). Among the Cervidae, the genus crota, R. stehlini, R. timorensis, R. elegans, R. yunnanensis and R. unicolor) Rusa is one of the most complex genera whose origin and evolution as were reported throughout China in the past (Dong, 1993), but the well as classification still remain unclear (Brooke, 1878; Pocock, 1942, former two lacked enough fossil materials and detailed stratigraphic 1943; Leslie, 2011). The number of species referred to this genus is information. Recent review studies indicated that R. unicolor rather different according to the various authors especially in regard to the than R. timorensis existed in Taiwan during the Pleistocene epoch (Wei, fossil forms (Di Stefano and Petronio, 2002). Four allopatric extant 2007; Kawamura et al., 2016). species (R. unicolor, R. timorensis, R. marianna and R. alfredi)(Fig. 1) are Bailong Cave (32°59′40.0′′N, 110°31′33.6′′E) (Fig. 1), an important ∗ Corresponding author. Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, 100044, China. E-mail address: [email protected] (B. Zhang). https://doi.org/10.1016/j.quaint.2020.03.048 Received 24 October 2019; Received in revised form 20 March 2020; Accepted 23 March 2020 Available online 04 April 2020 1040-6182/ © 2020 Elsevier Ltd and INQUA. All rights reserved. B. Zhang and H. Tong Quaternary International 550 (2020) 120–129 Fig. 1. Pleistocene sites* with Rusa fossils unearthed in China and the distribution map of the extant Rusa taxa. *The detailed information of fossil sites is listed in Table 1. Middle Pleistocene hominid site in China, is located in Yunxi County, collection of IVPP in Beijing. Living comparative specimens are de- Hubei Province (Wu et al., 2009; Liu et al., 2015; Dong, 2016; Han posited in the collection of IOZ and IVPP in Beijing. The classification et al., 2019; Kong et al., 2018; Tong et al., 2019; Dong et al., 2020). The system follows Mattioli (2011). The terminology for antler is after preliminary study of mammalian fossils reported five cervid species Bubenik (1990) and Groves (2003). The dental terminology is after including Elaphodus cephalophus, Muntiacus cf. reevesi, Muntiacus Heintz (1970), Janis and Scott (1987), Bärmann and Rössner (2011), muntjak, R. unicolor and Cervus grayi (Tong et al., 2019). The sambar Tong and Zhang (2019). Nomenclature follows O’Leary (2010) for fossils are dominant elements which include nicely preserved antlers, petrosal bone, Orliac et al. (2012) and Costeur et al. (2018) for bony mandible fragments, isolated teeth and an isolated petrosal bone. Pre- labyrinth. The measurements of antler and dentition are after Heintz viously, the study on the sambar fossils were mainly concentrated on (1970) . Measurements of each specimen were taken with a digital ca- the broken antlers and isolated permanent cheek teeth. Here, we liper. We scanned the petrosal bone at the IVPP and the bony labyrinth broadened the research scope by adding the almost complete antlers, was segmented using the Mimics 19.0. Linear, angular, and volumetric deciduous teeth and a petrosal bone as well as the bony labyrinth it measurements of the bony labyrinth were made in the Mimics 19.0. The houses. The intricate petrosal bone and the embedded bony labyrinth measuring method of bony labyrinth follows Ekdale (2013) and Macrini have received more and more attentions because these two regions et al. (2013). have considerable potential to elucidate the phylogenetic relationships Institution abbreviations: IOZ, Institute of Zoology, Beijing; IVPP, in many ruminants (Webb and Taylor, 1980; Vislobokova, 1990; Institute of Vertebrate Paleontology and Paleoanthropology; V, Prefix O’Leary, 2010; Costeur, 2014; Mennecart and Costeur, 2016a, b; in the catalog numbers for vertebrate fossils in IVPP. Mennecart et al., 2016, 2017; Costeur et al., 2018), and the present Abbreviations for the petrosal bone: ap, apex; aptt, anterior study on the petrosal bone of sambar will definitely contribute to stu- process of tegmen tympani; ca, cochlear aqueduct; ci, crista inter- dies on deer phylogeny. fenestralis; ew, epitympanic wing; fai, foramen acusticum inferius; fas, foramen acusticum superius; fc, fenestra cochleae; fsl, facial sulcus; ftt, fossa for tensor tympani; fv, fenestra vestibuli; hf, hiatus Fallopii; mr, 2. Materials and methods mastoid region; pr, promontorium; smf, stapedial muscle fossa; sf, subarcuate fossa; sff, secondary facial foramen; tt, tegmen tympani; va, All the fossil specimens described in this paper are housed in the 121 B. Zhang and H. Tong Quaternary International 550 (2020) 120–129 vestibular aqueduct. base of the main beam and forms an acute angle with the main beam. Abbreviations for the bony labyrinth: aa, asc ampulla; asc, The anterolateral tine is longer than the posteromedial tine. The dis- anterior semi-circular canal; ca, cochlear aqueduct; cc, common crus; tance between brow tine and anterolateral tine is large. The orna- co, cochlea; es, endolymphatic sac; fc, fenestra cochleae; fv, fenestra mentations are mainly developed longitudinal furrows and ridges as vestibuli; la, lsc ampulla; lsc, lateral semi-circular canal; pa, psc am- well as some small pearls. The cross section of the main beam is roughly pulla; psc, posterior semi-circular canal; sac, sacculus; ut, utriculus; va, rounded. The bifurcation part between anterolateral tine and poster- vestibular aqueduct. omedial tine is tabular. 3. Systematic paleontology 3.1.2. Upper teeth 3.1.2.1. Deciduous upper teeth. From DP2 to DP4 (Fig. 3 a-c), both the Cervidae Gray, 1821 size and molarization degree are increasing. In occlusal view, DP2 is Cervinae Goldfuss, 1820 quite elongated and moderately molarized; the second lobe is slightly Cervini Goldfuss, 1820 wider than the first lobe; the protocone separated from metaconule by a Rusa Hamilton-Smith, 1827 distinct lingual groove at the lingual side. There are some folds on the Rusa unicolor (Kerr, 1792) inner side of metaconule and the metaconule fold is prominent. The Referred materials: V26044.1, left antler with broken anterolateral parastyle, metastyle as well as paracone rib are robust. The tine; V26044.2, right antler with broken brow tine and posteromedial precingulum is developed. There are two roots on both lingual and tine; V26044.3, right antler with all tines broken off; V26044.4, prox- buccal sides, but all of them are broken. DP3 is almost molarized and its imal fragment of left antler; V26044.5, proximal fragment of left antler; first lobe is remarkably narrower than the second lobe.