Hipparion Material from Gaojiashan Locality in the Late Miocene of Linxia Basin, Gansu, China and Associated Mammalian Fossil Assemblage

Historical Biology An International Journal of Paleobiology

ISSN: 0891-2963 (Print) 1029-2381 (Online) Journal homepage: http://www.tandfonline.com/loi/ghbi20

Hipparion material from Gaojiashan locality in the Late Miocene of Linxia Basin, Gansu, China and associated mammalian fossil assemblage

Yikun Li, Wen He, Shanqin Chen, Shiqi Wang, Boyang Sun & Yu Li

To cite this article: Yikun Li, Wen He, Shanqin Chen, Shiqi Wang, Boyang Sun & Yu Li (2017): Hipparion material from Gaojiashan locality in the Late Miocene of Linxia Basin, Gansu, China and associated mammalian fossil assemblage, Historical Biology, DOI: 10.1080/08912963.2017.1315684 To link to this article: http://dx.doi.org/10.1080/08912963.2017.1315684

Published online: 19 Apr 2017.

Submit your article to this journal

View related articles

View Crossmark data

Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=ghbi20

Download by: [125.75.255.66] Date: 20 April 2017, At: 05:17 Historical Biology, 2017 http://dx.doi.org/10.1080/08912963.2017.1315684

Hipparion material from Gaojiashan locality in the Late Miocene of Linxia Basin, Gansu, China and associated mammalian fossil assemblage

Yikun Lia,b, Wen Hec, Shanqin Chenc, Shiqi Wanga,d, Boyang Suna,b and Yu Lia,b

aKey Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing, P.R. China; bUniversity of Chinese Academy of Sciences, Beijing, P.R. China; cHezheng Paleozoological Museum, P.R. China; dCAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, P.R. China

ABSTRACT ARTICLE HISTORY Two Hipparion species, H. forstenae and H. hippidiodus from Gaojiashan locality in the Linxia Basin, Gansu, Received 2 January 2017 China are described in this paper, with the first presence of the former in the Linxia Basin. The lower Accepted 2 April 2017 cheek teeth of Hipparion from Gaojiashan bear deep ectoflexids, and after comparisons to other Chinese KEYWORDS Hipparion fossils with deep ectoflexids, the mandibles with deep ectoflexids on the lower premolars Late Miocene; Linxia Basin; suggest their attributions to H. forstenae. The presence of a deep ectoflexid on p2 may be interpretable Hipparion; mammalian fossil as an intraspecifically variable feature in H. forstenae, and can also be found in H. dermatorhinum. Besides assemblage the Hipparion material, at least 8 species of large mammals occur at the Gaojiashan locality, including Adcrocuta eximia, Chilotherium wimani, Shansirhinus ringstroemi, Eucladoceros cf. proboulei, Palaeotragus cf. coelophrys, Giraffidae gen. et sp. indet., and the previously studied Promephitis hootoni and Eostyloceros hezhengensis. Although the sample from Gaojiashan shares five species with the Yangjiashan fauna, the Gaojiashan fossil assemblage may date to the Baodean because of the presence of H. forstenae. The overall taxonomic composition of the Gaojiashan assemblage at least suggests an approximate Baodean age, which would imply survival of C. wimani into the Baodean of the Linxia Basin.

Introduction Hezheng County. The Gaojiashan locality is labelled LX 0034 (35°21′21.3″N, 103°19′00.7″E) in IVPP geological surveys (Deng, The Linxia Basin is well known for yielding abundant and com- Qiu et al. 2013), and the locality is in highly vegetated cover pletely preserved large mammalian fossils. The fossiliferous because of increasing rainfalls in the West China during recent areas cover nearly the whole of Hezheng County, the western years. The geological setting and field photo of the Gaojiashan half of Guanghe County, the southern areas of Dongxiang locality are shown in Figure 1(A),(B). County and Linxia City, and the easternmost parts of Linxia and Jishishan counties. Fossil assemblages known from successive geological sequences in the region include the Late Oligocene Material, methods and abbreviations Dzungariotherium fauna, Middle Miocene Platybelodon fauna, Late Miocene Hipparion fauna and Early Pleistocene Equus The mammalian material from Gaojiashan is comprised of two fauna, and the Linxia Basin has notably produced fossil rodents, parts: specimens collected from the field expeditions, and those lagomorphs, primates, carnivores, proboscideans, perissodactyls housed at Hezheng Paleozoological Museum. The specimens and artiodactyls (Deng, Qiu et al. 2013). collected from the field expeditions, are deposited and accessi- Hipparion material is quite abundant in the Linxia Basin, ble in the collections of the Institute of Vertebrate Paleontology where H. dongxiangense, H. weihoense, H. chiai, H. dermatorhi- and Paleoanthropology, Chinese Academy of Sciences (142 num, H. platyodus, H. coelophyes, and H. hippidiodus were previ- Xizhimenwai Street, Beijing, China), including material of ously reported in the Liushu Formation (Deng, Qiu et al. 2013). Hipparion forstenae, lower cheek teeth row of H. hippidiodus, Only the Hipparion material from the Wangji and Shilei localities skull of Eostyloceros hezhengensis, antlers of Eucladoceros cf. were present with detailed descriptions (Qiu & Xie 1998; Pang proboulei, upper teeth of Palaeotragus cf. coelophrys, and tooth 2015). Two Hipparion species, H. forstenae and H. hippidiodus fragment of Giraffidae gen. et sp. indet. The specimens belonging occur at the Gaojiashan locality, with the first presence of the to Hezheng Paleozoological Museum contain skulls of Adcrocuta former in the Linxia Basin. Besides the Hipparion material, the eximia, Promephitis hootoni, Hipparion hippidiodus, Chilotherium associated mammalian assemblage is also present here. wimani, and Shansirhinus ringstroemi, and a metacarpal of Gaojiashan is administratively a part of Jinchanggou Hamlet, Palaeotragus cf. coelophrys. Compared to the well-preparations Xinzhuang Township (previously named Guantangou Township), of the material housed in the Institute of Vertebrate Paleontology

Figure 1. The Gaojiashan locality, Hezheng, China. (A) geological setting of the location follows Deng et al. (2014); (B) field photo of the fossil locality taken in 2016. and Paleoanthropology, many specimens preserved in the Systematic paleontology of Hipparion material Hezheng Paleozoological Museum are mounted for display and unprepared. This situation hampers confident identification and (1) Material assigned to H. forstenae detailed description of the material in question, but contributes Order Perissodactyla Owen, 1848 to public education and science outreach. Except that the mate- Family Equidae Gill, 1872 rial of Eostyloceros and Promephitis have previously been studied Genus Hipparion de Christol, 1832 by Deng et al. (2014) and Wang and Qiu (2004), morphologi- Subgenus Cremohipparion Qiu & Huang et al., 1987 cal descriptions of the other material are present in this paper. Hipparion (Cremohipparion) forstenae Zhegallo, 1971 The mandible of H. forstenae was CT scanned, using the 450 kV Hipparion richthofeni, Sefve, 1927: p. 20, pl. II, figs. 5–6; pl. industrial CT at the Key Laboratory of Vertebrate Evolution and III, figs. 7–10. Human Origins, Chinese Academy of Sciences. The measure- Hipparion richthofeni, Gromova, 1952. ments are taken with digital calipers with a precision of 0.1 mm. Hipparion plocodus, Forstén, 1968, in part. The morphological nomenclatures and measuring methods follow Hipparion richthofeni, Zhegallo, 1978. those of: Qiu, Huang et al. (1987) and Eisenmann et al. (1988) in Hipparion plocodus, Forstén, 1985, in part. hipparions, Werdelin (1988) and Werdelin and Solounias (1990) ‘Hipparion’ richthofeni, Bernor et al., 1987. in hyaenids, Guérin (1980) and Deng (2001, 2005) in aceratheres, Lectotype: PMU M 3873, skull of an old individual missing Dong (2008), Wang and Zhang (2011) and Deng et al. (2014) the snout (Sefve 1927; Pl. II, 5–6; Qiu, Huang et al. 1987), dis- in cervids, and Bohlin (1926) and Ríos et al. (2016) in giraffids. covered at Daijiagou, Baode County, Shanxi Province, China Abbreviations: IVPP V or V, specimen prefix of the Institute (Andersson’s Locality 30–2). of Vertebrate Paleontology and Paleoanthropology; LX, IVPP Referred material: V 23327.1, right facial fragment with P2– fossil locality number within the Linxia Basin; HMV, specimen M3; V 23327.2, fragmentary mandibles with left p2–m1 and right prefix of Hezheng Paleozoological Museum; PMU M, specimen p2–half p4; V 23327.3, right fragmentary mandible with p3–p4; prefix of the Evolution Museum of Uppsala University; THP, V 23327.4, right fragmentary mandible with m1–m3; V 23327.5, specimen prefix of the Licent Collection of Musee Hoangho left maxilla with DP2–DP4; V 23327.6, right dp4 (Figures 2,3(B); Paiho in Tianjin. Tables 1 and 2). HISTORICAL BIOLOGY 3

Figure 2. Hipparion fossils from Gaojiashan, Hezheng, China. H. forstenae: (A) right facial fragment, V 23327.1; (B) fragmentary mandibles, V 23327.2; (C) right p3–p4, V 23327.3; (E) right m1–m3, V 23327.4; (F) left DP2–DP4, V 23327.5; (G) left dp4, V 23327.6. H. hippidiodus: (D) left mandible, V 23328. Occlusal view. Scale bars = 5 cm, upper for A, B, lower for C–G.

Description rectangular, their lengths exceeding their widths. The presence of A complete series of cheek teeth, and part of the facial region are ridged main cusps and middle grooves indicates that V 23327.1 preserved in V 23327.1 (Figures 2(A) and 3(B)). The preorbital was still young at the time of death, and the difference in eleva- fossa is conspicuous and oval, with a posterior pocket. Its ventral tion between the cusps and the grooves is greater on the molars margin is smooth, and its posterior margin is prominent and than on the premolars. The protocone is buccally rounded and thickened. The major axis of the preorbital fossa is approximately lingually slightly convex on the premolars, but lingually flattened 45.0 mm in length and anteroventrally oriented. The infraor- on M1–M2. The protocone of the M3 is elongated, with angular bital foramen is situated at the level of the posterior part of the anterior and posterior ends and small wrinkles on the lingual P3. The anterior tip of the facial crest appears to lie at the level margin. A rudimentary, anterobuccally located spur is present of the boundary between P4 and M1. The maxillary tuberosity on P2. The lingual margins of the paracone and metacone are is partially preserved and positioned 8.9 mm posterior to the straight on P2, slightly convex on P3–P4, and distinctly convex posterior margin of the M3. The anterior palatine foramen is on M1–M3. The buccal walls of the paracone and metacone are situated at the level of the protocone of the M2. The position of flat on P2. On other teeth, the buccal wall of the paracone is con- the posterior palatine foramen, and that of the suture between vex, whereas that of the metacone is flat and deflected posteriorly. the lacrimal and orbital part of the frontal, indicate that the orbit The parastyle and mesostyle on cheek teeth are developed, and must have been very close to the preorbital fossa. protrude buccally. A clear middle groove is present on the par- The length of the dental series extending from P2 to M3 is astyle of the premolar but absent on the molar. The mesostyle is 135.5 mm. The occlusal outline of the P2 is triangular due to the wide and bifurcated on P2–P3 and M1–M2. However, the meso- elongated anterostyle. By contrast, the others cheek teeth are style of the P4 is weakly bifid, the anterior branch being merely 4 Y. LI ET AL.

Figure 3. Hipparion fossils from Gaojiashan, Hezheng, China. H. hippidiodus: HMV 0761 (A) skull, right lateral view; (C) mandible, right lateral view; (D),(E) upper teeth, occlusal view; (F),(G) lower teeth, occlusal view. H. forstenae: (B) right maxillary, V 23327.1, right lateral view. Scale bars = 5 cm; upper for A–C, lower for D–G. a small wrinkle. Usually one or two plications are present on the poorly developed. They are also longer and narrower, forming anterior border of the prefossette, although four are present in slenderer rectangles. The protocone is small, being rhombic on M2. In each case the lingualmost plication is robust and directed DP2, buccally rounded and lingually slightly convex on DP3, posteriorly. At most seven plications are present on the posterior and elongated triangular on DP4. An anterobuccal positioned border of the prefossette. Single pli protoconule present on P2 spur is present on DP2. The paracone, metacone, protoconule and M3, two on P4–M2, three on P3 are robust and long, and and hypocone are small relative to those on the permanent teeth. directed anterobuccally. Three to five plications are present on The hypocone is located posteriorly, lying nearly at the level of the anterior border of the postfossette, and are slender and evenly the lingual margin of the protocone. The anterostyle of the DP2 distributed. Except on M1 and M3, no plications are present on is narrow and elongate. The parastyles and mesostyles on the the posterior border of the postfossette. Except two on P3, the upper deciduous premolars are wide, and protrude buccally in pli caballine is single, but with bifurcated tips on M1, and with a small distance. The prefossettes and postfossettes on DP3–DP4 trifurcated tips on P4. The pli caballine is long, and nearly reaches are similar in size and outline, and the anterior horns of the the buccal margin of the protocone. The hypoconal groove is nar- postfossettes do not extend far beyond the posterior horns of row and moderately incised on P2, but wide and deeply incised the prefossettes in the buccal direction. One to three plications on P3–M2. The posterior border of the postfossette is open on are present on the anterior border of the prefossette, and up M3. Weak hypoconal constrictions are present on P2 and M3. to five plications are present on the posterior border. The plis The length of the teeth series DP2–DP4 in V 23327.5 is protoconule are stout, and two or three in number. Two or three 87.6 mm. The crowns of these teeth are much lower than in plications are present on the anterior border of the postfossette, the corresponding permanent premolars, and the cement is and one plication is present on the posterior border, except that HISTORICAL BIOLOGY 5 - - 69.7 73.2 67.8 64.3 55.3 52.5 66.4 67.6 46.6 88.9 83.2 77.4 77.2 69.2 71.9 59.0 60.7 61.4 57.7 52.1 45.6 40.4 59.3 61.6 57.5 41.0 59.1 62.4 57.8 59.0 55.8 57.1 55.6 43.2 52.4 length cone width cone Index of proto Index of metac onid-metastylid - - 19.6 24.3 26.7 23.7 25.7 30.0 13.6 19.9 21.7 19.9 20.7 31.3 32.3 34.3 33.2 35.5 35.9 32.6 32.2 33.6 33.4 – 40.8 50.3 45.8 31.4 41.4 52.1 46.2 47.6 28.8 28.2 32.8 32.2 27.3 cone length cone Index of proto flexid length flexid Index of post - 4.2 4.3 4.1 3.3 3.0 3.0 3.2 3.5 2.8 5.4 5.2 5.2 5.3 4.9 5.2 4.0 4.2 4.0 3.7 3.7 3.3 cone – 17.7 28.0 27.9 25.8 18.1 26.1 24.9 23.6 22.0 22.9 22.8 23.6 19.9 length Width of proto Width Index of preflexid Index of preflexid - 6.0 5.8 6.1 5.2 5.5 5.7 4.8 5.2 6.0 6.1 6.3 6.7 6.8 7.1 7.2 6.8 6.9 6.6 6.5 7.0 7.2 Length of Length protocone 8.9 9.7 6.2 12.1 13.8 13.3 11.8 12.0 13.4 13.8 13.3 11.0 10.5 10.1 flexid 1 2 1 1 1 1 1 2 1 1 1 1 1 1 1 1 1 1 1 1 1 gualflexid-ecto line Width across lin - across Width Pli(s) cabal - Pli(s) 11.8 14.9 14.2 12.5 11.9 14.8 13.9 12.6 12.1 11.6 11.3 10.6 10.1 14.7 knot 0 0 0 1 0 1 1 1 0 1 1 1 1 1 1 2 2 2 2 2 – Length of double Length - of postfossette

Plis on posterior border border on posterior Plis – 6.8 5.9 5.9 6.5 6.2 6.4 11.9 12.7 10.6 12.0 13.0 10.3 10.4 flexid Length of post Length 3 5 4 5 4 4 3 3 2 1 1 1 1 2 3 3 2 3 3 4 3 – 5.2 7.1 6.5 5.6 5.2 6.5 5.6 5.1 4.5 4.8 4.5 4.5 4.6 of postfossette preflexid Length of Length Plis on anterior border border on anterior Plis - 3 7 7 6 6 4 3 5 5 5 3 6 6 5 6 6 4 5 5 6 7 9.6 9.1 9.4 8.8 8.4 7.5 11.8 12.5 11.9 10.2 11.9 12.8 12.2 11.4 aojiashan, Hezheng, C hina (mm). aojiashan, Hezheng, enamel bands stylid-hypoconid stylid-hypoconid der of prefossette aojiashan, Hezheng, C hina (mm). aojiashan, Hezheng, Width across meta - across Width Plis on posterior bor on posterior Plis - - 2 1 1 2 4 2 2 3 1 4 4 1 1 1 1 1 1 3 – – – 9.8 7.7 10.3 12.9 12.6 12.0 10.7 13.3 13.6 12.6 11.2 10.8 11.5 10.5 der of prefossette Plis on anterior bor on anterior Plis toconid enamel bands toconid Width across metaconid-pro across Width 20.3 21.0 19.3 19.6 17.8 11.8 17.8 18.1 16.1 23.6 23.7 23.6 23.1 23.1 22.9 21.6 21.3 20.2 20.3 19.4 18.6 Width 29.2 25.2 23.1 21.8 28.9 25.0 22.3 21.7 20.5 20.7 19.9 19.1 23.3 28.1 Length 30.7 24.0 22.6 21.9 21.4 19.1 35.0 26.1 27.5 30.4 30.2 21.4 21.2 20.8 21.7 19.2 19.2 20.1 20.1 20.1 21.5 Length ndex of preflexid length = length of preflexid ndex of preflexid × 100/length length = length of postflexid tooth; index of of postflexid × 100/lengthindex of metaconid-metastylid = lengthof tooth; of metaconid-metastylid × 100/length of ndex of protocone length = length of protocone × 100/length of tooth; index of protocone width = width of protocone × 100/length of protocone. width = width of protocone × 100/length of protocone index of tooth; length = length of protocone × 100/length of protocone ndex tooth. fossils from G from of Hipparion fossils of upper cheek teeth 1. Measurements Table Specimen Notes: I Notes: V 23327.1 P2 P3 P4 M1 M2 M3 V 23327.5 DP2 DP3 DP4 HMV 0761 P2 L P2 R P3 L P3 R P4 L P4 R M1 L M1 R M2 L M2 R M3 L M3 R V 23327.2 L p2 L p3 from G from H. forstenae of cheek teeth of lower 2. Measurements Table Specimen I Notes: L p4 L m1 R p2 R p3 V 23327.3 R p3 R p4 V 23328 L m1 L m2 V 23327.4 R m1 R m2 R m3 V 23327.6 R dp4 6 Y. LI ET AL.

- no plis occur on DP4. The pli caballine is robust, and extending towards the protocone. The hypoconal groove is approximately rhombic, although wider anteriorly than posteriorly, and is more 49.7 50.3 69.2 69.3 63.2 65.9 60.1 62.1 61.1 57.4 47.0 45.5 59.0 55.8

length deeply incised than those on the permanent molars. Index of metac onid-metastylid The length of the lower premolar series of V 23327.2 is 77.1 mm, and that of the lower molar series of V 23327.4 is - 62.7 mm. The paraconid of the p2 is oval, and expands and protrudes anteriorly. The protoconid is directed posterobuccally, 18.3 18.7 24.7 24.4 35.4 35.1 26.1 28.0 30.3 28.6 25.9 25.4 28.8 28.2 and has a convex buccal margin. The hypoconid is slender, with flexid length flexid

Index of post pinched anterior and posterior ends. The buccal margin of the hypoconid is slightly convex on p2–p3, and convex on p4–m3.

- The double knots are rounded with short handles, and the metaconid is slightly larger than the metastylid. The metaconid and 18.0 17.6 34.1 33.4 26.8 25.3 28.4 26.8 27.2 26.8 24.8 24.3 22.0 22.9 metastylid are situated lingually, lying nearly at the same level as the entoconid. The entoconid is quadrangular, and so expanded flexid length flexid Index of pre that it almost contacts the metastylid to enclose the postflexid. The hypoconulid is small, short, and linguobuccally directed, - although the size of this structure increases posteriorly along the lower cheek teeth. The preflexid of the p2 is asymmetrical, not 9.5 9.9 9.7 8.4 7.6 8.9 9.7 11.5 12.0 12.9 12.2 11.1 10.4 10.0 projecting anteriorly. On p3–m3, the preflexid is almost sym- lingualflex id-ectoflexid Width across across Width metrical, the posterior horn is just slightly larger, and a small fold often projects from the middle of the preflexid’s posterior wall. The postflexid is slender, with a slightly wrinkled base. The anterior portion of the postflexid is anterolingually directed on 12.9 12.3 14.2 14.2 14.6 15.1 12.3 12.3 11.8 11.5 11.4 11.2 12.1 11.6 the lower premolars, approaching the base of the lingualflexid, ble knot but anteriorly directed on the lower molars. A small fold appears Length of dou - Length at the anterior portion of the postflexid on m2–m3. On p2–p3 the - lingualflexid is shallow, not reaching or even approaching the half

width of the double knots, and is V-shaped with a rounded base. 4.7 4.6 5.1 5.0 8.2 8.0 5.4 5.6 5.9 5.7 6.3 6.3 5.9 5.9 The lingualflexid of the p4 is U-shaped, and is deep in V 23327.2 flexid and shallow in V 23327.3. On m1–m3 the lingualflexid is deep

Length of post Length and U-shaped. The isthmus is inclined posterobuccally on p2–p4, but wide and buccally directed on m1–m3. The ectoflexids of the lower premolars are narrow and relatively deep. The ectoflexid 4.7 4.3 7.0 6.8 6.2 5.8 5.8 5.3 5.3 5.4 6.0 6.0 4.5 4.8 squeezes the anterior portion of the postflexid on p2, reaches the preflexid Length of Length posterior horn of the preflexid but remains on the vestibular side of the postflexid on p3, squeezes the anterior portion of the postflexid on p4 of V 23327.3, and penetrates the isthmus on p4 of V 23327.2. The ectoflexids of the lower molars are wide, penetrating 9.8 9.5 9.1 9.1 9.5 9.1 9.6 9.1 10.6 11.2 11.8 11.6 11.8

11.6 the isthmus and nearly contacting the base of the lingualflexid. On p2–m2 the pli caballinid is weak and situated at the half aojiashan, Hezheng, C hina (mm). aojiashan, Hezheng, enamel bands

stylid-hypoconid stylid-hypoconid width of the hypoconid, but on m3 the pli caballinid is stronger. Width across meta - across Width Protostylids are present on p3–p4 in V 23327.3, but absent in - V 23327.2. A protostylid is present on m1 in V 23327.2,4. The hypoconulid of the m3 is expanded posteriorly, with a lingual fold and buccal wrinkle at the midpoint of its length. 9.4 9.6 13.3 12.5 14.0 13.8 11.4 11.4 10.6 10.8 10.2 10.3 11.2 10.8 V 23327.6 is identified as a dp4, as this tooth bears little cement and has a low crown height (23.1 mm) that is much enamel bands onid-protoconid onid-protoconid

Width across metac across Width smaller than the crown length. The parastylid extends beyond able 2 . T the lingual margin of the metaconid. The metaconid is elongate, and the metastylid is rounded. The lingual walls of the metac- 25.9 24.4 20.5 20.4 23.1 22.9 20.5 19.8 19.3 20.1 24.2 24.7 20.5 20.7 onid and metastylid are wrinkled, as are the buccal walls of the Length protoconid and hypoconid. The protoconid and hypoconid are slender. The buccal margin of the protoconid is straight, whereas that of the hypoconid is slightly convex. The lingualflexid is deep and U-shaped, and the ectoflexid is also deep. The protostylid is well-developed, forming a strong buccal fold. The ectostylid is robust and low, situated just above the boundary between the G H. hippidiodus of from cheek teeth of lower 3. Measurements Table Specimen Note: For explanations of indices see of indices explanations For Note: HMV 0761 L p2 R p2 L p3 R p3 L p4 R p4 L m1 R m1 L m2 R m2 L m3 R m3 V 23328 L m1 L m2 crown and the root. HISTORICAL BIOLOGY 7

Figure 4. Images from CT scan of V 23327.2, in occlusal view: (A) without artificial wear; (B) worn 1.808 mm; C( ) worn 4.32 mm; (D) worn 7.665 mm; (E) worn 11.736 mm. Scale bar = 15 mm.

Comparison foramen is situated at the dorsoventral level of the posterior part Based on the dimensions of the cheek teeth, V 23327.1–6 belong of the P3; the orbit is positioned at the same dorsoventral level as to a mid-sized species within the genus Hipparion. The fossils the preorbital fossa; the maxillary tuberosity is poorly developed; also reveal cranial and dental features consistent with the diagno- the plis protoconule are long and robust, and extend towards sis of the subgenus Cremohipparion (Qiu, Huang et al. 1987). The the centre of the prefossette; the plis caballine are robust, and preorbital fossa is deep, located close to the orbit, and contains a extend towards the protocone; and the hypoconal grooves are posterior pocket. On the upper cheek teeth, the protocones are wide and deeply incised. The above characters are consistent with small and rounded, and the plications are moderately developed. the material assigned to H. forstenae, which is discovered from On the lower cheek teeth, the double knots are rounded, and the Baode, Shanxi and Nyalam, Tibet, and V 23327.1 resembles V buccal margins of the protoconids and hypoconids are at least 4660.1 most, founded in Huoxian, Shanxi, because of their rela- slightly convex. tive young age. The lower cheek teeth are thoroughly compared Hipparion licenti and H. forstenae are attributed to the subge- in the next part. nus Cremohipparion, whose nasal structure is distinctive (Qiu, Huang et al. 1987). Unfortunately, the nasal is not preserved in V (2) Material assigned to H. hippidiodus 23327.1. However, several characters indicate that the specimens Subgenus Hipparion de Christol, 1832 of V 23327.1–6 belong to Hipparion (Cremohipparion) forste- Hipparion hippidiodus Sefve, 1927 nae (Qiu, Huang et al. 1987; Deng et al. 2015). The infraorbital Hipparion richthofeni, Teilhard de Chardin, 1922. 8 Y. LI ET AL.

Figure 5. Hipparion mandibles with deep ectoflexids on lower premolars. H. dermatorhinum: V 8242 (A),(B); V 8243 (C),(D). H. forstenae: V 4660.4 (E),(F); V 4660.5 (G); V 4660.6 (H); V 4660.7 (I); RV27007 (J). H. guizhongensis: V 5195–5 (K),(L). H. insperatum: V 8204 (M),(N). H. cf. tchikoicum: V 8207 (O). All in occlusal view. Scale bar = 5 cm.

Lectotype: PMU M 3819, fragmentary skull of an old individ- of the paracone of the P4, and the nasal notch is situated at the ual with complete cheek teeth (Sefve 1927; fig. 7; Forstén 1968), level of the boundary between P2 and P3. The upper cheek teeth discovered at Mujiazuiguo, Qingyang County, Gansu Province, individually appear squared in occlusal outline, due to heavy China (Andersson’s Locality 115). wear. Measurements and numbers of plis for the upper cheek Referred material: HMV 0761, skull of an old individual; V teeth are present in Table 1. The protocone is buccally rounded, 23328, left fragmentary mandible with m1–m2 (Figures 2(D) with a lingual margin that is either straight or slightly concave and 3(A),(C–G); Tables 1 and 3). in the middle. The lingual margin of the metacone on the pre- Description molar is straight or slightly convex. The parastyle is wide and not The length of the row of upper cheek teeth is 135.2 mm, which bifurcated, and the mesostyle is narrow and buccally protruding. falls within the expected range for medium-sized Hipparion. Plications are scarce on the anterior border of the prefossette The snout is elongate and slender. The preorbital fossa is weak except on P2, and no more than seven plications are present on and egg-shaped in outline, with the long axis anteroposteriorly the posterior border. Up to three plications are present on the oriented. The dorsal margin of the preorbital fossa is distinctive, anterior border of the postfossette, and one or two plications are but the other margins of the fossa are faintly defined. The dis- present on the posterior border. The pli caballine is short and tance between the lacrimal-jugal suture and the posterior mar- single on P2–M3. The hypoconal groove is slightly or moderately gin of the preorbital fossa is 26.8 mm. The buccinator fossa is incised, and the hypoconal constriction is generally weak but well-developed. The infraorbital foramen is located at the level better-developed on M3. HISTORICAL BIOLOGY 9

Measurements and ratios between selected measurements V 23327.2–3 appears closely comparable to previ- for the lower cheek teeth are present in Table 3. The double ously described lower mandibular specimens of Hipparion knots are rounded with short handles, and are situated more (Cremohipparion) forstenae, except in the morphology of the lingually than the entoconid. The metastylid is subtriangular. ectoflexid on the lower cheek teeth. Qiu, Huang et al. (1987) The lingualflexid is shallow and V-shaped on p2–p3, but deep mentioned ‘the ectoflexid on lower premolar is shallow’ as a char- and U-shaped on p4–m3. The isthmus is wide. The ectoflexid acter of H. forstenae. The ectoflexids of the H. forstenae speci- reaches the posterior end of the prefossette on the lower mens V 4660.4–7 are indeed relatively shallow, especially on p2, premolars, and penetrates the isthmus and nearly contacts the but those of the Gaojiashan specimens V 23327.2–3 are deep. lingualflexid on the lower molars. The buccal margin of the In V 23327.2, the ectoflexid squeezes the anterior portion of protoconid is convex, although only slightly so on m1. The the postflexid on p2, reaches the posterior horn of the preflexid buccal margin of the entoconid is convex on p2 and m2–m3, but but remains on the vestibular side of the postflexid on p3, and straight or at most slightly convex on p3–m1. The hypoconulid squeezes the anterior portion of the postflexid and penetrates the of the m3 is expanded posteriorly, and is separated into two isthmus on p4. In V 23327.3, the p3’s ectoflexid is similar to that lobes in the case of the right tooth but not in the case of the left. of V 23327.2, and the p4’s ectoflexid is shallower than that of V A protostylid is present on p3–m2. No pli caballinid occurs on 23327.2, squeezes the anterior portion of the postflexid, and does the lower cheek teeth. not penetrate the isthmus. The lower molars of the Gaojiashan Comparison specimens have deep and wide ectoflexids that usually penetrate HMV 0761 can be excluded from H. forstenae based on the the isthmus, and nearly contact the base of the lingualflexid. poorly developed preorbital fossa, moderate or simple pli- Based on the images derived from CT scan (Figure 4), the mor- cations, and single and short plis caballine. Considering the phology of the ectoflexid is relatively stable during wear, except medium length of the dental series P2–M3, the specimens can in the heavy wear stage when the preflexid constricts, the ecto- be assigned to H. hippidiodus (Qiu, Huang et al. 1987; Bernor flexid gets slightly shallower. This finding is in accordance with et al. 1990) based on several cranial and dental characters. The the previous studies of sectioned lower premolars (Qiu, Huang preorbital fossa is shallow and close to the orbit. The infraor- et al. 1987; Pang 2011; Bernor & Sun 2015). bital foramen is situated relatively high, and at the dorsoventral Deng et al. (2016) considered that primitive Eurasian level of the P4. Except on P2, only one plication is present on Hipparion have deep ectoflexids on the lower premolars and the anterior border of the prefossette. The plications on the rounded double knots on the lower cheek teeth. At least five spe- posterior border of the prefossette number less than eight on cies found in China have relatively deep ectoflexids on lower pre-

each tooth, and the plications on the anterior border of the molars, including H. dermatorhinum, H. guizhongensis, H. licenti, postfossette number about three. The pli caballine is single H. insperatum and H. tchikoicum (Ji et al. 1980; Qiu, Huang et al. and short. The protocone is small and rounded. The hypoconal 1987; Liu 2013; Deng et al. 2016). Lower teeth of these five spe- groove is slightly or moderately incised. The lower premolars cies plus H. forstenae are depicted in Figure 5, although recently are much larger than the lower molars. The double knots are described specimens of H. insperatum and H. tchikoicum from rounded. The metaconid is larger than the metastylid, which is Inner Mongolia are omitted (Pang 2011; Deng et al. 2016). subtriangular. No pli caballinid is present on the lower cheek The mandibles V 8242 and V 8243 from Baode, Shaanxi teeth. are attributed to H. dermatorhinum (Qiu, Huang et al. 1987). HMV 0761 is clearly identifiable and comparable to the mate- According to Qiu, Huang et al. (1987), one character of this rial assigned to H. hippidiodus (Qiu, Huang et al. 1987; Bernor species is that ‘the ectoflexid reaches the buccal sides of the pre- et al. 1990; Pang 2015) based on the cranial and dental characters. and postfossettes’. In V 8242, the ectoflexid squeezes the anterior H. hippidiodus was previously reported in the Baode locality, portion of the postflexid and penetrates the isthmus on p2, and Shanxi, the Qingyang locality, Gansu, and even in the Shilei local- reaches the posterior horn of the preflexid but remains on the ity of the same basin. The morphology of HMV 0761 resembles vestibular side of the postflexid on p3–p4. In V 8243, the ectof- more similar to that of the Qingyang material, than that of the lexid is shallow and does not approach the posterior horn of the Shilei material, which is interpreted as the presence of derived preflexid on p2, approaches the posterior horn of the preflexid characters and indicates a younger age than that of the Shilei on p3, and squeezes the anterior portion of the postflexid on p4. locality (Pang 2015). However, the lower premolars of these specimens differ from V 23327.2–4 in being larger, and in that the metastylid is triangular (3) Comparison and discussion about the lower cheek teeth or subtriangular in shape with an acutely angled lingual corner. Some Gaojiashan specimens certainly pertain to H. hippidiodus, THP 10400 is attributed to H. licenti based on its consistency but others show morphological features that preclude their refer- in size with the holotype and on the form of the ectoflexid. This ral to this species. For example, the fragmentary mandibular structure approaches the posterior horn of the preflexid on p3, pair V 23327.2 can be excluded from H. hippidiodus based and reaches the posterior horn of the preflexid but remains on the on the following characters: the metastylid of lower premolar vestibular side of the postflexid on p4 (Qiu, Huang et al. 1987). rounded, not subtriangular; lingualflexid of p2–p3 U-shaped; However, V 23327.2–4 cannot be assigned to H. licenti because weak pli caballinid present. The teeth preserved in V 23327.2 of their previously mentioned similarities to H. forstenae. and the smaller mandibular fragment V 23327.3 are very similar V 5195–4, 5 were originally assigned to H. guizhongensis, in occlusal outline and structure to those of V 4660.5–7, which but later reidentified as H. forstenae (Ji et al. 1980; Qiu, Huang are identified as H. forstenae and collected in Huoxian, Shanxi et al. 1987). V 5195–5 differs from V 23327.2–4 in the following (Tung et al. 1975; Qiu, Huang et al. 1987). characters: metastylid on p3–p4 subtriangular; lingualflexid on 10 Y. LI ET AL.

p2–p4 shallow and widely U-shaped, with a wrinkle near the middle of the length; and pli caballinid on p2–p3 well-developed. Apart from the presence of strong pli caballinids on V5195–5, the teeth of V 5195–5 are similar to those of V 4660.4 in occlusal outline and structure. H. insperatum and H. tchikoicum belong to the subgenus Baryhipparion, which was established by Qiu, Huang et al. (1987). H. insperatum has been found in Yushe, Shaanxi, and Gaotege, Inner Mongolia (Qiu, Huang et al. 1987; Pang 2011). V 23327.2–4 can be excluded from H. insperatum, because in H. insperatum specimens V 8204 and V 16771.4 the metastylid on p3–p4 is subtriangular or quadrangular, the ectoflexid on p2 squeezes the anterior portion of the postflexid and penetrates the isthmus, and the double knots are buccally twisted on the lower cheek teeth. H. tchikoicum specimens have been recovered from Yushe, Shaanxi, and Baogeda Ula, Inner Mongolia (Qiu, Huang et al. 1987; Deng et al. 2016). V 8207, identified asH. cf. tchikoicum, is similar to V 8204 except that the ectoflexid on p2 is shallower. Thus, the presences of subtriangular or quadrangular metastylids and buccally twisted double knots can be used to distinguish H. cf. tchikoicum from V 23327.2–4. V 20208 was recently found in Inner Mongolia and attributed to H. tchikoicum (Deng et al. 2016). However, in this specimen the metastylid is subtriangular on p3–4, and the double knots are not clearly buccally twisted. Figure 6. Hyaenid fossils from Gaojiashan, Hezheng, China. A. eximia, HMV 1956, The teeth of the Gaojiashan specimen V 23327.2 are similar to skull: (A) left lateral view; (B) dorsal view. Scale bar = 5 cm. those of V 20208 in occlusal outline and structure, apart from having rounded metastylids on p3–p4 and a weak pli caballinid

on p2. In V 20208 the ectostylid approaches the posterior horn Table 4. Measurements of skull of Adcrocuta eximia from Gaojiashan, Hezheng, of the preflexid on p2, and the ectostylid is shallower than in V China (mm). 23327.2. Greatest width of occipital condyles 53.9 Greatest width of skull at zygomatic arches 179.1 Considering deep ectoflexids are also observed on p4 in V Least width of skull at post-orbital constructions 47.9 4660.7, and on p3–p4 in V 5195–5, V 23327.2–3 can be ascribed Width of skull between post-orbital processes 73.0 to H. forstenae. Particularly in the case of the p2, in which the Least width between orbits 63.8 Width of skull between buccal margins of P4 99.6 ectoflexid squeezes the anterior portion of the postflexid, the Width of skull between buccal margins of canines 69.7 lower molars of H. forstenae may sometimes bear deep ectoflex- Dorsoventral depth of mandible behind m1 52.1 ids. The presence of either a shallow or a deep ectoflexid on p2 Dorsoventral depth of mandible at diastema 40.7 Inclusive distance between p2 and m1 81.8 in H. forstenae can be seen as an intraspecific difference, as also Distance from dorsal margin of condyle to ventral margin of angular 41.2 be seen in the H. dermatorhinum specimens: V 8242 possessing process a deep ectoflexid on p2, whereas V 8243 with a shallow one. sagittal crest is relatively low. Upper incisors are preserved, and Systematic paleontology of associated mammalian the mesial two are similar in morphology whereas the third is assemblage more caniniform. The P2 and P3 are robust, with conical main cusps. The upper carnassial is elongate and robust, although the (1) Material attributed to A. eximia protocone is reduced. The lower cheek teeth are powerfully con- Order Carnivora Bowdich, 1821 structed, and the horizontal ramus of the mandible is robust and Suborder Feliformia Kretzoi, 1945 deep. The mental foramen is situated below p2. The well-devel- Family Hyaenidae Gray, 1821 oped masseteric fossa extends along the ventral margin of the Genus Adcrocuta Kretzoi, 1938 horizontal ramus, and also up to the ascending ramus. Adcrocuta eximia (Roth and Wagner, 1854) The size of HMV 1956 is large, similar to that of extant Referred material: HMV 1956, complete skull (Figure 6(A),(B); Crocuta crocuta, whereas HMV 1956 differs from C. crocuta in Table 4). the presences of p1, process of the nuchal ligaments, and more Description and comparison posteriorly placed infraorbital foramen. In considerations of the The skull is relatively broad and short. The orbit is relatively small, large size, short and broad proportions of the skull, as well as with a prominent postorbital process, and its anterior rim is at the robust premolars and powerful jaw, the specimen can definitely dorsoventral level of the boundary between P3 and P4. A frontal be attributed to Adcrocuta eximia (Werdelin & Solounias 1990, depression is present. The zygomatic arch is relatively short, and 1991). The species was firstly attributed to Hyaena eximia by expands at the rear to form the widest portion of the skull. The Roth & Wagner (1854), then to Crocuta eximia by Pilgrim (1931), HISTORICAL BIOLOGY 11

outline of an elongated rhombus, and appears concave in lateral view. The parietal crests are slightly separated, so that they do not form a sagittal crest, and their posterior ends curve slightly laterally. The zygomatic arch is comparatively narrow, and the anterior end of the arch reaches the dorsoventral level of the M1 in this young individual. The orbit is relatively low in position, and a strong supraorbital tubercle is present. The nasal is wide posteriorly, and forms an M-shaped suture with the frontal, but tapers in the cranial direction. The nasal notch is deep, and extends to the level of the boundary between P4 and M1. The premaxilla is reduced, and upper incisors are absent. The M3 was in the process of erupting at the time of death, and all teeth heights are relatively high. The mandible is extremely wide at the symphysial area, and this expansion reaches the level of the posterior margin of the p2. The mental foramen is located below p3, next to the ventral border. The region of the mandibular angle is wide, with a rough surface. The i2 is huge and upturned, with a rounded triangular cross section. HMV 0713 is a mid-sized acerathere, and the huge upturned i2, and retracted premaxiallae without upper incisors, place the specimen into the tribe Chilotheriini erected by Qiu, Xie et al. (1987). The relatively smaller size, trapezoidal occipital surface, unclear and shallow preorbital fossa, gradual constriction before the supraorbital tubercle, and wide mandibular symphysis further indicate that HMV 0713 is attributed to the genus Chilotherium (Qiu, Xie et al. 1987; Deng 2001). The slightly separated parietal crest, not forming a sagittal crest in HMV 0713 differs from the presence of the sagittal crest in C. primigenius, and the broadly

separated parietal crests in C. anderssoni and C. habereri (Deng 2001, 2006a). In addition, the material of Gaojiashan differs from C. primigenius in the relatively larger size, presences of the long diastema between i2 and p2 at the base, and concave ventral surface of the mandibular symphysis; it differs from C. habereri in the concave dorsal contour of the skull; and it differs from C. anderssoni in the concave dorsal contour and less devel- Figure 7. Acerathere fossils from Gaojiashan, Hezheng, China. C. wimani, HMV 1957, skull: (A) dorsal view; (B) right lateral view; S. ringstroemi, HMV 0713, skull: oped postorbital process (Ringström 1924; Deng 2001, 2006a). (C) dorsal view; (D) right lateral view. Scale bar = 5 cm. Furthermore, the mandibular symphysis is extremely wide and diagnostic, and thus this skull can be attributed to Chilotherium wimani. and finally removed to the new genus Adcrocuta Kretzoi, 1938 (3) Material attributed to S. ringstroemi (Werdelin & Solounias 1990). Because the Langebaanweg mate- Genus Shansirhinus Kretzoi, 1942 rial formerly classified as A. australis has been moved into the Shansirhinus ringstroemi Kretzoi, 1942 genus Chasmaporthetes, A. eximia is now regarded as the sole Referred material: HMV 1957, skull of an adult individual representative of the genus Adcrocuta, and the most common (Figure 7(C),(D); Table 5). hyaenid in the Late Miocene of China (Werdelin & Solounias Description and comparison 1990, 1991; Andersson & Werdelin 2005; De Bonis 2005). The premaxillae are retracted, and lack upper incisors. The nasal (2) Material attributed to C. wimani is short and concave in profile, with smooth and domed dorsal Family Rhinocerotidae Gill, 1872 surface. The anteriormost portion of the nasal is rounded and Subfamily Aceratheriinae Dollo, 1885 rough, and slightly elevated. The nasal is slightly constricted at Tribe Chilotheriini Qiu & Xie et al., 1987 the base, and slightly narrows down towards the tip with parallel Genus Chilotherium Ringström, 1924 lateral margins. The nasal notch is U-shaped, and extends to the Chilotherium wimani Ringström, 1924 dorsoventral level of the posterior edge of the P4. A depression is Referred material: HMV 0713, skull of a young individual (Figure present anterior to the orbit. The orbit is situated relatively low on 7(A),(B); Table 5). the side of the skull, and its anterior rim lies above the posterior Description and comparison part of the M2. A prominent supraorbital tubercle is present, and The occipital surface of the skull is trapezoidal in outline, and forms the widest portion of the skull. The zygomatic arch is more highly elevated in profile, with a deep occipital crest bearing a robust than that of Chilotherium wimani. The anterior end of the midline groove. The dorsal surface of the skull is narrow, with the zygomatic arch reaches the level of the boundary between M1 12 Y. LI ET AL.

Table 5. Measurements of skulls of Chilotherium wimani and Shansirhinus ringstro- Description and comparison emi from Gaojiashan, Hezheng, China (mm). This description is mainly based on V 23329.1, and measure- HMV HMV ments for all the antlers assigned to Eucladoceros cf. proboublei 1957 0713 here can be seen in Table 6. The antler is situated behind the orbit, 1. Distance between occipital condyle and premaxillary 537.3 532.6 and has two robust branches whose tips have broken away. The tip 2. Distance between occipital condyle and nasal tip 523.1 523.7 pedicle is relatively short, and the ridge between the frontal and 3. Distance between nasal tip and occipital crest 484.1 466.5 burr is poorly developed. The burr is well developed, and fringed 4. Distance between nasal tip and bottom of nasal 122.7 146.9 with bony tubercles. The burr is badly damaged, but when intact notch 5. Minimal width of braincase 57.8 95.7 was clearly oval or circular in cross-section. The antler base is 6. Distance between occipital crest and postorbital 238.0 213.3 thick, due to the overlapping between the anterior and posterior process branches at the low position. Relative to the distance between the 7. Distance between occipital crest and supraorbital 261.5 241.0 tubercle first segment and the burr, the point at which bifurcation begins 8. Distance between occipital crest and lacrimal 303.5 280.6 is quite low on the antler. The anterior branch is inclined slightly tubercle laterally, and both branches are slightly curved posteriorly. Both 9. Distance between nasal notch and orbit 80.2 60.4 13. Distance between occipital condyle and M3 265.5 – branches are oval in cross-section, with their cross-sectional long 14. Distance between nasal tip and orbit 196.8 205.3 axes slightly oblique but close to anteroposterior in orientation, 15. Width of occipital crests 88.3 132.8 and the minimum and maximum diameters of anterior branch 16. Width of mastoid processes 157.2 186.9 17. Minimal width between parietal crests 30.0 30.9 are larger than those of the posterior one. The angle of bifurca- 18. Width between postorbital processes 135.0 131.3 tion between the two branches is relatively small. Longitudinal 19. Width between supraorbital tubercles 153.6 151.8 grooves and ridges occur along both branches, but those on the 20. Width between lacrimal tubercles 155.6 163.5 21. Maximal width between zygomatic arches 225.3 257.5 medial surface of the anterior branch are most obvious. 22. Width of nasal base 82.0 87.4 Only two branches are preserved in each of the antlers from 23. Height of occipital surface 168.9 112.5 V 23329.1–5. Based on its size and outline, V 23329.1 can be 25. Cranial height in front of P2 140.3 121.3 26. Cranial height in front of M1 176.7 149.5 clearly differentiated from most Miocene cervids with two- 27. Cranial height in front of M3 193.1 – tined antlers, which were thoroughly discussed by Wang and 31. Width of foramen magnum 28.5 37.8 Zhang (2011). Large amounts of Late Miocene cervid material 32. Width between exterior borders of occipital – 111.8 condyles have been assigned to Cervavitus (Dong & Hu 1994; Dong & Ye 1997; Petronio et al. 2007; Wang & Zhang 2014). However, the

Gaojiashan antlers differ from those ofCervavitus and resemble and M2, and the posterior part of the arch is slightly expanded. those of Eucladoceros proboulei (Dong & Ye 1996) in the robust- The dorsal surface of the skull is slightly concave, and the occip- ness of the anterior branch and the low, medial position of the ital portion is highly elevated in profile. The parietal crests are area in which the branches converge. Several other characters of slightly separated, and slightly curved dorsally in profile. The the Gaojiashan antlers are also in accordance with diagnosis of DP1 is smaller than the other cheek teeth, which are moderately Eucladoceros proboulei, including the robust, slightly posteriorly worn. The mandibular symphysis may be moderately expanded curved morphology of the antler base branches, the small bifur- buccally, and the degree of expansion cannot be precisely deter- cation angle, and the ornamentation composed of longitudinal mined due to crushing. The mental foramen is located below grooves and ridges. In Eucladoceros the number of the branches is p3. The i2 is much smaller than that of C. wimani, and strongly usually at least four, but the two branches preserved in each of the upturned. Gaojiashan antlers are so robust that their unpreserved tips may HMV 1957 resembles that of Chilotherium wimani in a large have bifurcated to produce the expected branch number. Similar extent, including the retracted premaxillae lacking upper inci- distal bifurcation of the branches takes place in Pleistocene rep- sors, saddle-like dorsal surface of the skull, and concave ventral resentatives of Eucladoceros, such as Eucladoceros dicranios. surface of the mandibular symphysis. However, the seemingly However, the antler branches of Eucladoceros proboulei are moderately expanded mandibular symphysis, small i2, robust approximately rectangular or flattened in cross-section, whereas zygomatic arch, and anteriorly slightly raised and posteriorly those of V 23329.1 are oval. Thus, the antlers from Gaojiashan constricted nasal indicate that the specimen from Gaojiashan are designated Eucladoceros cf. proboulei. may not belong to the genus Chilotherium, and instead suggest (5) Material attributed to P. cf. coelophrys its referral to Shansirhinus ringstroemi (Deng 2005). More dif- Family Giraffidae Gray, 1821 ferences could be found at the dental morphologies after the Genus Palaeotragus Gaudry, 1861 well-preparation of the specimen. Palaeotragus cf. coelophrys (Rolder & Weithofer, 1890) (4) Material attributed to E. cf. proboulei Referred material: V 23330.1, left M3; V 23330.2, right DP3; Order Artiodactyla Owen, 1848 HMV 1955, left metacarpal (Figure 9(A–J); Tables 7 and 8). Family Cervidae Goldfuss, 1820 Description and comparison Subfamily Cervinae Baird, 1857 The upper cheek teeth from Gaojiashan assigned to giraffids in Genus Eucladoceros Falconer, 1868 this paper have bifurcated postmetaconule cristae, and inden- Eucladoceros cf. proboulei Dong and Ye, 1996 tations separating the lingual and buccal cusps, in contrast to Referred material: V 23329.1, right antler; V 23329.2–5, four the close crescentic features seen on the occlusal surfaces of antler fragments (Figure 8; Table 6). cervid and bovid upper cheek teeth. A left M3 and a right DP3 HISTORICAL BIOLOGY 13

Figure 8. Cervid fossils from Gaojiashan, Hezheng, China. E. cf. proboulei: right antler, V 23329.1, (A) lateral view; (B) medial view; (C) cranial view; (D) caudal view; (E) left antler, V 23329.2; (F) ?left antler, V 23329.3; (G) right antler, V 23329.4; (H) right antler, V 23329.5. E–H, medial view. Scale bar = 5 cm. were recovered, and measurements for these teeth fall into the well-developed, with a mesially positioned flange. The mesostyle range characteristic of P. rouenii (P. microdon) or P. cf. coelophrys protrudes buccally, together with the metastyle, to form a low (Bohlin 1926; Table 7). The M3 is square in occlusal outline, and fused common margin. A weak mesial cingulum and spur are increases its width towards the base. The tooth is in early wear, present. The entostyle is low and poorly developed. with a relatively high crown. The enamel is rugose and displays A left metacarpal, HMV 1955 is present in the Gaojiashan incremental lines, which are especially obvious on the buccal material. The metacarpal has a slender robustness index wall. The distal lobe is proportionally large, mesiobuccally and (RI = 0.97), and a medium length (434.9 mm), with an inter- distolingually inclined relative to the mesial one. The mesostyle is mediate-deep central trough (Ríos et al. 2016). The synovial well-developed, with a mesially positioned flange, and protrudes fossa is oval and nearly closed, and there is a deep and narrow buccally. The rib of the paracone is better developed than that of groove in the proximalmost median plane, separating the medial the metacone. A mesial cingulum is present. A buccally directed and lateral epicondyles. The medial epicondyle is smaller and spur is present on the lingual side of the distal fossette. fuller than the lateral epicondyle. There is a wedge extension The DP3 is rectangular in occlusal outline, and the crown of of the proximal articular surface onto the palmar surface of the this tooth is much lower than that of the M3. However, the DP3 lateral epicondyle. A longitudinal groove separates the lateral resembles the M3 in the topology of the occlusal surface. The epicondyle, and distally connects to the lateral ridge. The lateral mesial lobe is wide and proportionally large. The parastyle is and medial ridges extend almost the entire length of the shaft, 14 Y. LI ET AL.

Table 6. Measurements of antlers of E. cf. proboulei from Gaojiashan, Hezheng, China (mm). V 23329.1 V 23329.2 V 23329.3 V 23329.4 V 23329.5 Anteroposterior diameter of burr 68.9 >54.8 69.6 >60.0 >53.0 Mediolateral diameter of burr 66.3 >51.6 >49.3 >43.6 >38.5 Thickness of burr 11.0 9.2 9.9 11.0 6.8 Anteroposterior diameter of antler base 49.5 46.0 49.7 48.6 >40.0 Mediolateral diameter of antler base 42.7 42.3 >42.6 39.5 >37.3 Anteroposterior diameter of anterior branch just above first segment 29.9 23.7 – 25.0 25.3 Mediolateral diameter of anterior branch just above first segment 39.2 32.8 – 34.5 29.3 Anteroposterior diameter of posterior branch just above first segment 28.5 >25.6 – 24.3 26.0 Mediolateral diameter of posterior branch just above first segment 32.6 31.6 – >30.7 30.7 Anteroposterior diameter of pedicle near midpoint 32.5 31.2 31.8 – – Mediolateral diameter of pedicle near midpoint 38.1 >26.8 33.8 – – Distance between first segment and burr on the medial side of the antler 77.2 63.1 63.5 64.7 61.6 Height of starting point of bifurcation 14.6 15.6 7.6 18.8 10.9 Angle between anterior and posterior branches 28° 27° – 22° 21°

Figure 9. Giraffid fossils from Gaojiashan, Hezheng, China. P. cf. coelophrys: left metacarpal, HMV 1955, (A) proximal view; (B) palmar view; (C) dorsal view; (D) distal view. Right DP3, V 23330.2, (E) occlusal view; (F) buccal view; (G) lingual view. Left M3, V 23330.1, (H) occlusal view; (I) buccal view; (J) lingual view. Giraffidae gen. et sp. indet.: fragmentary upper molar, V 23331, (K) occlusal view; (L) lingual view. Scale bars = 5 cm, left for A–D, right for E–L. HISTORICAL BIOLOGY 15

Table 7. Measurements of upper teeth of P. cf. coelophrys from Gaojiashan, this partial tooth should be attributed to a larger giraffe than Hezheng, China (mm). Palaeotragus. Measurement M3 DP3 Length of occlusal surface 27.2 24.5 Width at base of mesial lobe 26.1 17.0 Discussion about Gaojiashan mammalian assemblage Width at base of distal lobe 25.1 17.5 Height at metacone 23.6 12.8 Hipparion forstenae, H. hippidiodus, Chilotherium wimani, Shansirhinus ringstroemi, Eucladoceros cf. proboulei, Palaeotragus cf. coelophrys, Giraffidae gen. et sp. indet., and Adcrocuta eximia Table 8. Measurements of metacarpal of P. cf. coelophrys from Gaojiashan, Hezheng, are reported from Gaojiashan in this paper, and Promephitis China (mm). hootoni and Eostyloceros hezhengensis were previously reported Measurement HMV 1955 from this locality (Wang & Qiu 2004; Deng et al. 2014). At least Length 434.9 ten species thus occur at the Gaojiashan locality. This sample Proximal transverse diameter 68.6 shares five species with the Yangjiashan mammalian fauna (Table Proximal anteroposterior diameter 47.5 9), which pertains to the Bahean, but may nevertheless represent Middle transverse diameter 42.2 Middle anteroposterior diameter 37.5 a fauna of Baodean given the presence of H. forstenae (Deng, Distal transverse diameter 68.4 Hou et al. 2013). Distal anteroposterior diameter 42.7 In fact, the first appearance of Hipparion forstenae is considered as the biostratigraphic marker of the beginning of the Baodean. The lower boundary of the Baodean has recently been and flatten close to the distal condyle. The lateral ridge is sharp, constrained to lie within the Chron C3Br.1r, implying an age whereas the medial ridge is relatively rounded. The pyramidal of about 7.25 Ma and a correlation with the base of the marine rise is present and faint at the distal shaft. The medial aspect Messinian Stage (Deng, Hou et al. 2013). The taxa known from of the medial distal condyle flares distally, whereas the lateral Gaojiashan are listed alongside those from some representative aspect of the lateral distal condyle is more vertical. The keels of early Baodean localities in Table 9. The mammalian assemblage the lateral and mesial distal condyles extend onto the palmar from Gaojiashan approximately resembles that of Jijiagou except shaft. Based on above characters, the metacarpal can be assigned the presence of Chilotherium wimani, which is thought to be to the genus Palaeotragus (Ríos et al. 2016). The length or RI of restricted in the Bahean (Deng 2001, 2006b; Deng, Qiu et al. HMV 1955 is larger than that of P. rouenii, and a plesiomorphic 2013). taxon such as P. coleophrys would be expected to have longer and The magnetostratigraphy of the Heilinding section located more robust metapodials than a relatively derived one such as P. about 2 km away from the Gaojiashan locality, and was studied rouenii (Solounias 2007). Thus, the metacarpal can be attributed by Wang et al. (2010). The fossiliferous layer at the Heilinding to Palaeotragus cf. coelophrys. We tentatively apply the same tax- locality is stratigraphically lower than that at the Gaojiashan onomic designation to the M3 and DP3. locality, and just below the base of the Baodean Stage (Deng, Qiu et al. 2013; Deng, Hou et al. 2013). This indicates that the (6) Material attributed to Giraffidae gen. et sp. indet. Gaojiashan mammalian assemblage may be later than 7.25 Ma, Giraffidae gen. et sp. indet. the approximate date of the beginning of the Baodean, under the Referred material: V 23331, fragmentary upper molar (Figure assumption that the strata in this area are relatively horizontal 9(K),(L)). and comformable. Comparison The paleoenvironment of the Gaojiashan locality chrono- The sample from Gaojiashan includes the distal lingual part of an logically corresponds to the transitional stage from a temper- upper molar that differs from the M3 identified as Palaeotragus ate steppe to a more arid steppe based on the data analysis of cf. coelophrys in being larger and possessing an entostyle. the fossil mammal cenograms (Deng 2009). Shansirhinus was Furthermore, the length of the metaconule is 18.3 mm, so that thought to be apt to an open and dry ecological environment this feature is much larger than in the M3 of P. cf. coelophrys because of possessing special dental morphologies (Deng 2005; (14.8 mm). The entostyle is stout and quite low, being situ- Lu et al. 2015). Together with the presences of Hipparion and ated near the boundary between the crown and the root. Thus, Chilotherium, thus, the paleoenvironment of the Gaojiashan

Table 9. Taxa present at Gaojiashan and other representative localities.

Yangjiashan Fauna, Linxia Lower fossiliferous layer, Basin, Gansu (Deng, Qiu Jijiagou, Baode, Shanxi Loc. 42, Lantian, Shaanxi Longgugou, Gyirong-Oma Taxa et al. 2013) (Deng et al. 2004) (Zhang et al. 2002) Basin, Tibet (Ji et al. 1980) Adcrocuta eximia ＋＋＋ Promephitis hootoni ＋＋ Hipparion forstenae ＋＋ Hipparion hippidiodus ＋＋＋ Chilotherium wimani ＋ Shansirhinus ringstromi ＋ Eostyloceros hezhengensis Eucladoceros cf. proboulei Palaeotragus cf. coelophrys ＋ Giraffidae gen. et sp. indet. 16 Y. LI ET AL. locality seems best to be interpreted as a steppe habitat, whereas Deng T, Hou S-K, Wang N, Lu X-K, Li Y-K, Li Y. 2015. Hipparion fossils on there are still small amount of woods or bushes for Eostyloceros the Dati Basin in Nyalam, Tibet, China and their paleoecological and and Eucladoceros living. paleoaltimetry implications. Quat Sci. 35:493–501. Deng T, Hou S-K, Xie G-P, Wang S-Q, Shi Q-Q, Chen S-K, Sun B-Y, Lu X- In sum, the assemblage from the Gaojiashan locality can be K. 2013. Chronostratigraphic subdivision and correlation of the Upper dated to the Baodean based on the presence of Hipparion forste- Miocene of the Linxia Basin in Gansu. China J Stratigr. 37:417–427. nae and the high stratigraphic level of the fossiliferous layer in Deng T, Qiu Z-X, Wang B-Y, Wang X-M, Hou S-K. 2013. Late Miocene the Liushu Formation, which modifies that the first occurrence biostratigraphy of the Linxia Basin, northwestern China. In: Wang X- of the genus Eostlyoceros is later than 7.25 Ma. Chilotherium M, Flynn LJ, Fortelius M, editors. Fossil mammals of Asia. New York (NY): Columbia University Press; p. 243–273. wimani, which was previously thought to be restricted to the Deng T, Wang S-Q, Shi Q-Q, Li Y-K, Li Y. 2014. A new species of Eostyloceros Bahean, therefore appears to have survived into the Baodean (Cervidae, Artiodactyla) from the Late Miocene of the Linxia Basin in age in the Linxia Basin. The presence of Shansirhinus ringstroemi Gansu, China. Zootaxa. 3893:363–381. at the Gaojiashan locality further confirms its prosperity in the Deng T, Wang H-J, Wang X-M, Li Q, Tseng ZJ. 2016. The Late Miocene Late Miocene of the Linxia Basin. The presence of Eucladoceros Hipparion (Equidae, Perissodactyla) fossils from Baogeda Ula, Inner Mongolia, China. Hist Biol. 28:53–68. cf. proboulei prolongs the geologic records of this species, and Deng T, Wang W-M, Yue L-P, Zhang Y-X. 2004. New advances in the enriches the cervid diversities in the Late Miocene. establishment of the Neogene Baode Stage. J Stratigr. 28:41–47. Dong W. 2008. A review on morphology and evolution of antlers. In: Dong W, editor. Proceedings of the Eleventh Annual Meetings of the Chinese Acknowledgements Society of Vertebrate Paleontology. Beijing: China Ocean Press; p. 127–144. Dong W, Hu C-K. 1994. The Late Miocene Cervidae from Hounao, Yushe We thank Dr Deng Tao for providing the material and guiding the research. Basin, Shanxi. Vert PalAsiat. 32:209–227. We thank Dr Corwin Sullivan for English improving and comments. We Dong W, Ye J. 1996. Two new cervid species from the Late Neogene of thank Dr Shi Qinqin for her assistance in the field. We thank Gao Wei for Yushe Basin, Shanxi Province, China. Vert PalAsiat. 34:135–144. his photographs and Hou Yemao for his CT scans. Dong W, Ye J. 1997. A morphological analysis on intraspecific variation of Cervavitus novorossiae. Acta Palaeontol Sin. 36:253–268. Eisenmann V, Alberdi MT, De Giuli C, Staesche U. 1988. Studying fossil Disclosure statement horses, volume I: methodology. Leiden: E. J. Brill; p. 1–71. Forstén A. 1968. Revision of the Palearctic Hipparion. Acta zool fenn. No potential conflict of interest was reported by the authors. 119:1–134. Guérin C. 1980. Les rhinocéros (Mammalia, Perissodactyla) du Miocène terminal au Pléistocène supérieur en Europe occidentale: comparaison Funding arec les espèces actuelles. Doc Lab Geol Lyon. 79:1–1182.

Liu Y. 2013. Late Miocene hipparionine fossils from Lantian, Shaanxi This work was supported by the National Natural Science Foundation of Province and phylogenetic analysis on Chinese hipparionines [doctor China [grant number 41402003], [grant number 41430102]; and Strategic degree dissertation]. Beijing: Chinese Academy of Sciences; p. 1–130. Priority Research Program of the Chinese Academy of Sciences [grant Lu X-K, Chen S-Q, He W. 2015. New skulls of Shansirhinus ringstroemi from number XDB03020104]. the upper Neogene of the Linxia Basin, and their paleoenvironmental context. Quat Sci. 35:539–549. References Ji H-X, Hsu C-Q, Huang W-B. 1980. The Hipparion fauna from Guizhong Basin, Xizang. In: Scientific Research Groups on Tibet Plateau of Andersson K, Werdelin L. 2005. Carnivora from the Late Miocene of Chinese Academy of Sciences, editors. Palaeontology of Tiber, I. Beijing: Lantian, China. Vert PalAsiat. 43:256–271. Geology Press; p. 18–32. Bernor RL, Qiu Z-X, Hayek L-AC. 1990. Systematic revision of Chinese Pang L-B. 2011. Fossils of Pliocene Hipparion (Equidae, Perissodactyla) Hipparion species described by Sefve, 1927. Am Mus Novit. 2984:1–60. from Gaotege locality, Nei Mongol and their implications. Vert PalAsiat. Bernor RL, Sun B-Y. 2015. Morphology through ontogeny of Chinese 49:210–222. Proboscidipparion and Plesiohipparion and observations on their Pang L-B. 2015. Hipparion (Equidae, Perissodactyla) fossils from the Shilei Eurasian and African relatives. Vert PalAsiat. 53:73–92. locality of the Linxia Basin, Gansu Province. Quat Sci. 35:502–512. Bohlin B. 1926. Die Familie Giraffidae. Palaeontol Sin C. 4:1–179. German. Petronio C, Krakhmalnaya T, Bellucci L, Di Stefano GD. 2007. Remarks on De Bonis L. 2005. Carnivora (mammalia) from the Late Miocene some Eurasian pliocervines: characteristics, evolution, and relationships of Akkasdagi, Turkey. In: Sen S, editor. Geology, mammals and with the tribe Cervini. Geobios 40:113–130. environments at Akkasdagi, Late Miocene of Central Anatolia. Qiu Z-X, Huang W-L, Guo Z-H. 1987. The Chinese hipparionine fossils. Geodiversitas 27:567–589. Palaeontol Sin New Ser C. 25:1–243. Deng T. 2001. New materials of Chilotherium wimani (Perissodactyla, Qiu Z-X, Xie J-Y. 1998. Notes on Parelasmotherium and Hipparion fossils Rhinocerotidae) from the Late Miocene of Fugu, Shaanxi. Vert PalAsiat. from Wangji, Dongxiang, Gansu. Vert PalAsiat. 36:13–23. 39:129–138. Qiu Z-X, Xie J-Y, Yan D-F. 1987. A new chilothere skull from Hezheng, Deng T. 2005. New cranial material of Shansirhinus (Rhinocerotidae, Gansu, China, with special reference to the Chinese “Diceratherium”. Perissodactyla) from the Lower Pliocene of the Linxia Basin in Gansu, Sci Sin Ser B. 545–552. China. Geobios 38:301–313. Ringström T. 1924. Nashörner der Hipparion-Fauna Nord-Chinas. Deng T. 2006a. A primitive species of Chilotherium (Perissodactyla, Palaeontol Sin Ser C. 1:1–159. Rhinocerotidae) from the Late Miocene of the Linxia Basin (Gansu, Ríos M, Danowitz M, Solounias N. 2016. First comprehensive China). Cain Res. 5:93–102. morphological analysis on the metapodials of Giraffidae. Palaeontol Deng T. 2006b. Neogene rhinoceroses of the Linxia Basin (Gansu, China). Electron. 19:1–39. Cour Forsch-Inst Senckenberg. 256:43–56. Sefve I. 1927. Die Hipparionen Nord-Chinas. Palaeontol Sin Ser C. 4:1–54. Deng T. 2009. Late Cenozoic environmental changes in the Linxia Basin Solounias N. 2007. Family Giraffidae. In: Prothero DR, Foss SE, editors. The (Gansu, China) as indicated by cenograms of fossil mammals. Vert evolution of artiodactyls. Baltimore (MD): Johns Hopkins University PalAsiat. 47:282–298. Press; p. 257–277. HISTORICAL BIOLOGY 17

Tung Y-S, Huang W-P, Qiu Z-D. 1975. Hipparion in Anlo, Hohsien, Shansi. Werdelin L. 1988. Studies of fossil hyaenas: the genera Thalassictis Gervais Vert PalAsiat. 13:34–47. ex Nordmann, Palhyaena Gervais, Hyaenictitherium Kretzoi, Lycyaena Wang J-Y, Fang X-M, Zhang W-L, Zan J-B, Miao Y-F, Li S-Y. 2010. Hensel and Palinhyaena Qiu Huang & Guo. Zool J Linn Soc. 92:211– Magnetostratigraphy and implications of the Heilingding section, the 265. Linxia Basin, Gansu Province,China. Mar Geol Quat Geol. 30:129–136. Werdelin L, Solounias N. 1990. Studies of fossil hyaenids: the genus Wang L-H, Zhang Z-Q. 2011. A new species of Euprox (Cervidae, Adcrocuta Kretzoi and the interrelationships of some hyaenid taxa. Zool Mammalia) from the Middle Miocne of Damiao, Nei Mongol, China. J Linn Soc. 98:363–386. Vert PalAsiat. 49:365–376. Werdelin L, Solounias N. 1991. The Hyaenidae: taxonomy, systematics and Wang L-H, Zhang Z-Q. 2014. Late Miocene Cervavitus novorossiae evolution. Foss Strat. 30:1–104. (Cervidae, Artiodactyla) from Lantian, Shaanxi Province. Vert PalAsiat. Zhang Z-Q, Gentry AW, Kaakinen A, Liu L-P, Lunkka JP, Qiu Z-D, Sen 52:303–315. S, Scott R, Werdelin L, Zheng S-H, Fortelius M. 2002. Land mammal Wang X-M, Qiu Z-X. 2004. Late Miocene Promephitis (Carnivora, faunal sequence of the Late Miocene of China: new evidence from Mephitidae) from China. J Vert Paleontol. 24:721–731. Lantian, Shaanxi Province. Vert PalAsiat. 40:165–176.