第 卷 第 期 古 脊 椎 动 物 学 报 49 摇 1 pp.53-68 年 月 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 摇 2011 1 VERTEBRATA PALASIATICA 摇 figs.1-6

日本九州西部赤崎组和中甑组始新世 哺乳动物:初步结果及其与亚洲陆相 哺乳动物分期的对比

宫田和周1 富田幸光2 毕丛山3 4 摇 摇 摇 Gregg F. GUNNELL 鹈饲宏明5 广濑浩司5 日本福井县立恐龙博物馆摇 福井 (1 摇 摇 911-8601) 日本国立科学博物馆 东京 (2 摇 摇 169-0073) 美国卡内基自然历史博物馆 匹兹堡 (3 摇 摇 PA 15213) 美国密歇根大学古生物博物馆 安阿伯 (4 摇 摇 MI 48109-1079) 日本天草市立御所浦白垩纪博物馆 熊本 (5 摇 摇 866-0313)

摘要 日本已知时代最早的古近纪哺乳动物化石产自九州西部熊本县天草 地区始 : (Amakusa) 新世地层赤崎 组以及鹿儿岛县甑岛 相当层位的中甑 (Akasaki) (Koshiki Islands) (Nakakoshiki) 组 初步研究显示这两个组产出的哺乳动物分异度较高 包括 个目的至少 种动物 赤 。 , 9 18 。 崎动物群有 种 裂齿类 种冠齿兽科全齿类 种等脊貘科奇蹄类 种 3 trogosine 、2 、1 、2 dichobunoid 偶蹄类 种下齿兽科踝节类 种西瓦兔猴科灵长类 种未定食虫类以及 种可能的梳趾鼠 、1 、1 、1 2 类 中甑动物群包括 种冠齿兽科全齿类 种小型雷兽科奇蹄类 种高冠的下齿兽科踝节 。 1 、2 、1 类 种啮齿类和 种细齿兽科食肉类 这两个日本哺乳动物组合很接近早 中始新世界线 、2 1 。 - 。 由于出现了 裂齿类和雷兽 它们的时代要晚于伯姆巴动物群 极有可能与亚洲大陆 trogosine , , 阿山头期哺乳动物群相当 这两个动物群还包含了在亚洲大陆没有发现过的几个新种 并具 。 , 有独特的哺乳动物组合 。 关键词 日本九州 始新世 阿山头期 赤崎组 中甑组 哺乳动物 : , , , , , 中图法分类号 文献标识码 文章编号 :Q915. 87,P534. 613摇 :A摇 :1000-3118(2011)01-0053-16

EOCENE MAMMALS FROM THE AKASAKI AND NAKAKOSHIKI FORMATIONS, WESTERN KYUSHU, JAPAN: PRELIMINARY WORK AND CORRELATION WITH ASIAN LAND MAMMAL AGES

1 2 3 4 MIYATA Kazunori 摇 TOMIDA Yukimitsu 摇 K. Christopher BEARD 摇 Gregg F. GUNNELL 5 5 Fukui Prefectural Dinosaur Museum UGAI Hiroaki 摇 HIROSE Koji (1 Fukui 911-8601, Japan摇 k鄄miyata@ dinosaur. pref. fukui. jp) National Museum of Nature and Science (2 Tokyo 169-0073, Japan摇 y鄄tomida@ kahaku. go. jp) Carnegie Museum of Natural History (3 Pittsburgh, PA 15213, USA摇 beardc@ carnegiemnh. org) Museum of Paleontology University of Michigan (4 , Ann Arbor, MI 48109-1079, USA摇 ggunnell@ umich. edu) Goshoura Cretaceous Museum (5 Kumamoto 866-0313, Japan摇 g鄄mue01@ minos. ocn. ne. jp; g鄄mue02@ minos. ocn. ne. jp)

收稿日期 :2009-11-30 古 脊 椎 动 物 学 报 卷 摇 54 摇 摇 摇 摇 摇 摇 49

Abstract 摇 The earliest known Paleogene mammals from Japan are reported from the Eocene Akasaki Formation, Amakusa area, Kumamoto Prefecture and from the stratigraphically equivalent Nakakoshiki Formation, Koshiki Islands, Kagoshima Prefecture, western Kyushu. Preliminary work has revealed a high diversity of mammals from these formations, including at least 18 different species from nine or鄄 ders. The Akasaki fauna is represented by three trogosine tillodonts, two coryphodontid pantodonts, an isectolophid perissodactyl, two dichobunoid artiodactyls, a hyopsodontid condylarth, a sivaladapid pri鄄 mate, an unidentified insectivoran, and two possible ctenodactyloid rodents. The mammal fauna from the Nakakoshiki Formation includes a coryphodontid pantodont, two small brontotheriid perissodactyls, a hypsodont hyopsodontid condylarth, two rodents, and a miacid carnivoran. These Japanese mammal assemblages are from near the Early / Middle Eocene boundary, which is previously poorly known in Asia. Given the occurrences of trogosine tillodonts and brontotheriid perissodactyls, the Akasaki and Nakakoshiki faunas are younger than Bumbanian faunas and are most likely correlated with Arshantan faunas on the Asian mainland. The Japanese faunas contain several new taxa unknown from the Asian Kmaeiynlwanodr,dsand there are unique faunal combinations in the mammal assemblages. 摇 Kyushu, Japan; Eocene; Arshantan; Akasaki Formation; Nakakoshiki Formation; mammals

1摇 Introduction

Paleogene land mammals in Japan have bBeeranchdyeoscdruisbed jsappoornaidciucsally since the first report of an Oligocene anthracotheriid artiodactyl, “ 冶 Matsumoto ( Tokunaga, 1925). However, Paleogene mammal fossils from Japan are never abundant ( Appendix 1), and field work aimed at improving the Paleogene record of Japanese mammals has been intermit鄄 tent. In most cases, a rock unit has yielded a single or a few remains of one or two species, making it difficult to evaluate the biostratigraphic and biogeographic significance of such small samples. Among the known Paleogene mammal鄄bearing formations, the Eocene Akasaki Forma鄄 tion in Amakusa area, Kumamoto Prefecture and the coeval Nakakoshiki Formation in the Ko鄄 shiki Islands, Kagoshima Prefecture, have produced the most diversified and oldest known Ce鄄 nozoic faunas in Japan. The two formations represent the basal part of the Paleogene sequence in western Kyushu. One of us (K. Miyata) has investigated the stratigraphy and paleontology of the Akasaki and Nakakoshiki formations since 1992. The first mammal fossil from the Akasaki Formation was discovered at Akase鄄machi (Akase Town),HiUgtoothCeritiyu,mKhuympsaomdonto Prefecture in 1993, and it was described as a unique trogosine tillodont, Miyata & Tomida, 1998a. Later, seven specimens belonging to four orders (Tillodontia, Pantodonta, Perissodactyla, and Rodentia) were reported from the Akasaki Formation (Miyata and Tomida, 1998b). From the Nakakoshiki Formation, remains of mammals, including a coryphodontid pantodont and two brontotheriid perissodactyls, were found in 1999 (Miyata, 2003; Miyata and Tomida, 2003). Pending formal description of most of the fossil mammals from the Akasaki and Nakakoshiki for鄄 mations, this paper discusses the biochronological significance of these faunas with respect to the established sequence of Asian Land Mammal Ages.

2摇 Geological setting

The Akasaki Formation ( approximately 70 ~ 400 m in thickness) is distributed in the Amakusa area in the western part of Kumamoto Prefecture, while the Nakakoshiki Formation (approximately 890 m in thickness) outcrops on Kamikoshiki Island, which is part of the Ko鄄 shiki Islands in the northwestern part of Kagoshima Prefecture, western Kyushu, Japan ( Fig. 1). The fossiliferous horizons are concentrated in the upper and middle parts of the Akasaki Formation and in the middle part of the Nakakoshiki Formation. Both formations are basal units of the Eocene sequence unconformably overlying the Cretaceous Himenoura Group. 期 Miyata et al.:Eocene mammals from the Akasaki and Nakakoshiki formations, western 1 摇 55 Kyushu, Japan: preliminary work and correlation with Asian Land Mammal Ages

Fig. 1摇 Map showing the major fossil localities in the Amakusa area, Kumamoto Prefecture, and Kamikoshiki Island, Kagoshima Prefecture, western Kyushu, Japan The Akasaki Formation comprises fluvial deposits consisting mainly of conglomerate, red siltstone, and gray鄄blue siltstone. The Akasaki Formation is constrained to be no younger than early Middle Eocene on the basis of overlying marine strata, the Fukuregi and ShiraNtaukme mfourlmitae鄄s tionsD(isFciogc.y2cl)in,aboth of which bear various molluscan fossils and large foraminifera, and (Hanzawa and Urata, 1964; Miki, 1975; Miyata and Tomida, 1998a). The Fukuregi Formation and the stratigraphically higher Kyoragi (Kyouragi) Formation ( = Shikiya鄄 ma Formation in Okada, 1992) have yielded early Middle Eocene nannofossils pertaining to the Cp 13a subzone (approximately 47. 3 ~ 46. 1 Ma in Berggren et al., 1995; approximately 46. 6 ~ 45. 0 Ma in Luterbacher et al., 2004) ( Okada, 1992). Aside from these stratigraphic con鄄 straints, there is no direct chronological evidence bearing on the age of the Akasaki Formation and the length of the hiatus between the Akasaki Formation and the overlying marine strata (the Fukuregi and Shiratake formations). Miyata (2007) suggested that the age of the Akasaki Formation potentially could extend from the late Early to early Middle Eocene based on the paleomagnetic data provided by Miki and Matsueda (1985). The paleomagnetic results of Miki and Matsueda (1985) indicate that 古 脊 椎 动 物 学 报 卷 摇 56 摇 摇 摇 摇 摇 摇 49

Fig. 2摇 Simplified stratigraphic correlation of the Eocene strata discussed in the text and standard global chronostratigraphic scales (Berggren et al., 1995; Luterbacher et al., 2004) showing the magnetic polarities (MP) and the interval of Cp 13a subzone the Akasaki Formation preserves three magnetozones ( Fig. 2). Because the Cp 13a subzone correlates with the normal interval of Chron 21 (Fig. 2; Berggren et al., 1995; Luterbacher et al., 2004), the Akasaki Formation is potentially correlated with the older geomagnetic intervals of Chrons 21 and 22, assuming that the results of Miki and Matsueda (1985) are reliable. Ishi鄄 kawa (1997) recognized strata exhibiting stable reversed polarity from red beds of the Akasaki Formation, but he interpreted this as secondary chemical remanences based on a hypothetical derivational model of hematite in the red beds proposed by Miki and Matsueda (1985). Never鄄 theless, we hypothesize that the Akasaki Formation probably has preserved primarily reversed polarities in several red beds based on preliminary geomagnetic tests, and we further confirmed the presence of stable reversed polarities from red beds of the Nakakoshiki Formation, support鄄 ing a coeval relationship between the two formations. The Nakakoshiki Formation, the basal part of the Paleogene Kamikoshikijima Group, pri鄄 marily consists of conglomerate, sandstone, red, gray鄄blue, and brown mudstone. The Nakako鄄 shiki Formation consists of fluvial deposits, whereas the overlying Oshima and Segami forma鄄 tions are shallow and offshore marine deposits, respectively ( Inoue et al., 1979, 1982). Al鄄 though the geological age of the Kamikoshikijima Group is unclear, Inoue et al. (1982) con鄄 cluded that these rock strata represent a southwestern extension of the Eocene sedimentary basin in the Amakusa area. Inoue and his colleagues proposed that the Nakakoshiki, Oshima, and Segami formations are stratigraphically correlated with the Akasaki, Shiratake (plus Fukuregi), and Kyoragi formations in the Amakusa area, respectively ( Fig. 2; Inoue et al., 1982 ). Toshimitsu et al. (2004), however, reported fission鄄track dates indicating 39. 2 依 2. 5 and 36. 4 依 3. 2 Ma from two different tuff beds in the Nakakoshiki Formation. These radioisotopic dates are somewhat younger than the ages expected based on the stratigraphic relationships men鄄 tioned above (Toshimitsu et al., 2004) and from the mammal fossils from the Nakakoshiki For鄄 mation. We assume that the Akasaki and Nakakoshiki formations are roughly contemporaneous strata dating near the Early / Middle Eocene boundary, although further geochronological evi鄄 dence pertaining to these two mammal鄄bearing formations is needed. 期 Miyata et al.:Eocene mammals from the Akasaki and Nakakoshiki formations, western 1 摇 57 Kyushu, Japan: preliminary work and correlation with Asian Land Mammal Ages

3摇 Faunal elements

Based on our preliminary work, we have recognized a high diversity of mammals from the Akasaki and Nakakoshiki formations, consisting of at least 18 different species from nine orders (Table 1; Figs. 3, 4). Brief comments are summarized below, pending more detailed study, but precise locality data are omitted. Table 1摇 Tentative list of mammal taxa from the Akasaki and Nakakoshiki formations

Akasaki Formation Nakakoshiki Formation Tillodontia, Esthonychidae, Trogosinae Higotherium hypsodon 摇 Trogosus T. latidens 摇 cf. Trogosus 摇 Cf. sp. Pantodonta, Coryphodontidae 摇 Gen. et sp. nov. Gen. et sp. indet. Asiocoryphodon 摇 sp. Condylarthra, Hyopsodontidae Hyopsodus Hyopsodus 摇 sp. nov. A 摇 sp. nov. B Perissodactyla, Isectolophidae Brontotheriidae Isectolophus 摇 sp. nov. 摇 Gen. et sp. nov. A 摇 Gen. et sp. nov. B Artiodactyla, Dichobunoidea 摇 Gen. et sp. nov. A (large) 摇 Gen. et sp. nov. B (small) Primate, Sivaladapidae 摇 Gen. et sp. nov. Rodentia, Ctenodactyloidea 摇 Gen. et sp. indet. A 摇 Gen. et sp. indet. C 摇 Gen. et sp. indet. B 摇 Gen. et sp. indet. D Insectivora 摇 Gen. et sp. indet. Carnivora, Miacidae 摇 Gen. et sp. indet. Tillodontia 摇 Three tillodonts belonging to the subfamily Trogosinae Gazin, 1953 have been formally described from thHeigAotkhaesraiukmi Fhoyrmpsaotdion (Miyata and Tomida, 1998a,c; Miyata, 2007). The derived trogosine Trogo,sursepresented by a right mandibular frag鄄 ment with hypsodont m2鄄3 (Fig. 3A), and cf. sp., documented by seven fragTmroegnotasurys teeth, wereTrroegcosvuesred frTo.mlathtiedeunpspermost part of the formation. A large species of (Fig. 3B, cf. ), described from the middle part of the formation, is repre鄄 sented by 12 teeth including brachydont molars, mandibular fragments, and cervical vertebrae ( Miyata, 2007). These three Ktruoagonscihnueasnfiruosm the Akasaki FormaCtiohnuncgacnhibeeniraeadily distinguish鄄 ed from the smaller trogosine and the enigmatic from the Middle EocenPeanotfoCdhoinntaa. 摇 Coryphodontid specimens have been reported from the middle parts of both the Akasaki and Nakakoshiki formations ( Miyata and Tomida, 1998b; Miyata, 2003; Miyata and Tomida, 2004, 2005; Miyata et al., 2006). One of the two Akasaki species (gen. et sp. nov. ) is represented by the skull and mandible of a single juvenile individual and an adult mandible (Fig. 3C, D). It is a derived species with bilophodont, hypsodont molars differing fromHaeltlerkoncorwynphAodsioann corEyupdhiondoocnetriadss; its dental structure suWgugetusctsoraypchlosdeornaffinity with Arshan鄄 tan or than with Bumbanian (Miyata and Tomi鄄 da, 2005; Miyata et al., 2006). Another Akasaki species represented by a mandibular frag鄄 古 脊 椎 动 物 学 报 卷 摇 58 摇 摇 摇 摇 摇 摇 49

Fig. 3摇 Selected mammHailgsoptheecriimumenshyfrposmodothne Akasaki Formation A. right mandibular fragment with m2鄄3 of Miyata & Tomida, 1998a, lateral view; B. fragments of the right mandible and uTprpoegro(sursight PT4., lMat2id,enocsclusal view) and lower teeth (left i1, lingual view; right i3, p3鄄m3, lateral view) of cf. described by Miyata (2007); C鄄D. juvenile skull with mandible in matrix (C) and adult mandible (D) of an unnHamyoepdsohdyupssodont coryphodontid gen. et sp. nov., lateral view; E. right mandibular fragment with p3鄄m2 of sp. nov. A, lingual view; F. left mandible of an unnamed dichobunoid gen. et sp. nov. A (large species), lateral view; G. right mandi鄄 bular fragment with matrix of an unnamed dichobunoid gen. et sp. nov. B (small species), lingual view

Asiocoryphodon ment with p3鄄m1 is a smaller species of . These two coryphodontid species were recovered from nearly the same horizon of the Akasaki Formation on Makishima (Maki Island), Goshoura Town, Amakusa City (Fig. 1). A coryphodontid specimen from the Nakakoshiki For鄄 期 Miyata et al.:Eocene mammals from the Akasaki and Nakakoshiki formations, western 1 摇 59 Kyushu, Japan: preliminary work and correlation with Asian Land Mammal Ages mation includes a posterior lower pHretmeroolcaorraynphdoadnonanterEiourdlionwoceerramsolar, which resemble those of largeCanodndhyylpasrotdhornat taxa such as or . Hyopso鄄 dus 摇 Two species of hyopsodontid condylarths, which Hliykoeplysobdeulsong to , have been recognized (Miyata and Tomida, 2004). The Akasaki is represented by a right mandibular fragment with p3鄄m2 from the upper part of the formation (Fig. 3E); the mandible is robust, and the cheek teeth are brachydont with a clear enamel fold on the p4 trigo鄄 nid. Another species is known from two right mandibles with p4鄄m3 and m2鄄3, wHhiycohpswodeures found in the middle part of the Nakakoshiki Formation (Fig. 4A). The Nakakoshiki has hypsodont molars with stronger entoconid and hypoconulid than in the Akasaki species.

Fig. 4摇 Selected mammaHl ysoppescoidmuesns from the Nakakoshiki Formation A. incomplete right mandibEleotwitiatnhopp4s鄄m3 of sp. nov. B, lateral view; B. incomplete left mandible with p4鄄m3 of an unnamed 鄄like brontotheriid gen. et sp. nov. A, lateral view; C. left p3鄄m2 of an unnamed miacid carnivoran gen. et sp. indet., lingual view Hyopsodus Three or four species were previously described from Early Eocene strata in Mongolia and Early and Middle Eocene strata in China ( Dashzeveg, 1977; TongH,y1op9s8o9dau;s Huang, 1995; Kondrashov and Agadjanian, 1999). TheHA.kaosriaeknitaalnisd Nakakoshiki are relaHti.veflaynlgaxrgiaensepnesicsies differing from the BumHba.nihaunashigouensis and are more similar in size to from the Early Eocene or from the Middle Eocene of ChinaP.erissodactyla Oriento鄄 lophus 摇 Two upper molars of a small isectolophid, comparable in size to , were previously reported from the middle part of the Akasaki Formation ( Miyata and Tomida, 1998b). Some additional dental material of the same individual was recently recov鄄 ered, demonstrating thOartietnhteolAopkhausaski Hisoemctoogloaplahxid is cleCarhlyowdliisiatinguishable from all known spe鄄 cies of Early Eocene Isectoloph,us , and . It possibly represents a new species of Middle EoceneOrientolophus ,heanlgthdooungghenBsioswen et al. (2002) and Tsubamoto et al. (2004) listed it as “cf. 冶 without taxonomic justification. Two small brontotheriid specimens were recovered from different levels of the middle part of the Nakakoshiki Formation (Miyata and Tomida, 2003). One specimen (gen. et sp. nov. A) is represented by a left mandible with p4鄄m3 (Fig. 4B) and several postcranial elements includ鄄 ing atlas, ulna, femur, aMndicsrcoatiptaunlae. ThPeylgemngatehtitoafnthe lower molar series indicates that it is a Esmotailtlaenrobprsontothere than and from Asia, being comparable in size to of early Bridgerian age in North America. The other specimen (gen. et sp. nov. B) is represented by an isolated left P4 that was recovered from a stratigraphic leveEl oatbitoaunto3p0s 0 m higher than that of the mandible mentMioincerodtiatabnoveP. yTghmeaPet4itaisn larger Nthaanotihtatnopfs and differs morphologically fProamlaethoosysoeposf , , and ; it resembles that oAf rstmioadllacsptyelcaies of from the Bridgerian of North America. 摇 Two possible dichobunoid species were recognized from the upper part of 古 脊 椎 动 物 学 报 卷 摇 60 摇 摇 摇 摇 摇 摇 49 the Akasaki Formation ( Miyata and Tomida, 2004). One is represented by the upper cheek tooth series, left mandible with nearly complete dentition, and some postcranial mateGrioabli.ohTyhues mandible has long diastemata between the canine and p3 as in the Irdinmanhan (Fig. 3F), but the upper dental characters differ from those of all known Asian artiodactyls. The second taxon is a smaller species (25 percent smaller in tooth dimension) known from a right Pmrainmdaibteuslar fragment with p4 to m3 (Fig. 3G). 摇 An isolated, lower molariform tooth from the upper part of the Akasaki Forma鄄 tion is a right m1 or m2 of a sivaladapid primate, which belongs to a new genus and new spe鄄 cies. RItodisenthtieaeaIrnliseesct trievcoorrad ofanthde Cfaamrinlyiv. ora , , 摇 Rodent, insectivoran, and carnivoran speci鄄 mens remain unprepared, but these specimens will eventually become important for clarifying the biochronological framework. The rodent specimens were recovered from the upper and mid鄄 dle parts of the Akasaki Formation and the middle part of the Nakakoshiki Formation. Most of the rodent specimens are isolated molariform teeth, that clearly belong to four different species including two ctenodactyloids. An insectivoran specimen consisting of a mandibular fragment with p3鄄m1 was recovered from the uppermost part of the Akasaki Formation. A miacid carnivo鄄 ran specimen from the middle part of the Nakakoshiki Formation includes a lower canine and left p3鄄m2 (Fig. 4C).

4摇 Discussion

In East Asia, various modern mammalian orders appeared in the Early Eocene Bum鄄 banian, and this was followed by a period of perissodactyl dominance in the subsequent Arshan鄄 tan (Meng and McKenna, 1998). The perissodactyl families that are abundant in Arshantan faunas include Brontotheriidae, Hyracodontidae, Rhinocerotidae, and Deperetellidae ( Fig. 5; Meng and McKenna, 1998 ). The Arshantan has traditionally been correlated to the North American Bridgerian land mammal age (e. g., Li and Ting, 1983; Tong, 1989b; Tong et al., 1995), and both of these ages have been considered to extend from the late Early to the early Middle Eocene (Luterbacher et al., 2004; Woodburne, 2004). However, independent chrono鄄 logical evidence constraining the age of early Paleogene faunas in Asia is sparse (Wang et al., 2007). In fact, there seems to be almost no chronological data constraining the Bumbanian / Ar鄄 shantan and Arshantan / Irdinmanhan boundaries aside from the recent magnetostratigraphic data from early Paleogene strata in the Erlian Basin, Nei Mongol, China ( Wang et al., 2009, 2010). According to Sun et al. (2009), the Arshanto Formation in the Erlian Basin probably correlates with the reversed interval of Chron 21 and older geomagnetic intervals, supporting the idea that the Arshanto Formation traverses the Early / Middle Eocene boundary ( Wang et al., 2009, 2010). Further fossils and associated chronological data from the Akasaki and Nakakoshiki forma鄄 tions are required to clarify the position of the mammalian faunal samples from these formations with respect to Asian Land Mammal Ages. However, considering the available paleomagnetic data from the Akasaki Formation and the stratigraphic superposition of marine strata bearing Cp13a nannofossils mentioned before, the age of the Akasaki and Nakakoshiki faunas can be placed near the Early / Middle Eocene boundary. This correlation suggests that the Japanese fau鄄 nas are contemporary with early Bridgerian faunas in North America and Arshantan faunas in the Asian mainland. Given the occurrences of trogosine tillodonts and brontotheriid perissodactyls, the Akasaki and Nakakoshiki mammal faunas are apparently younger than Bumbanian faunas and most likely correlate with the Arshantan age, although the Japanese faunas lack the perisso鄄 dactyl dominance that seems to characterize Arshantan faunas in China and Mongolia (Miyata and Tomida, 2004). Several new taxa documented in the Japanese faunas enhance our under鄄 期 Miyata et al.:Eocene mammals from the Akasaki and Nakakoshiki formations, western 1 摇 61 Kyushu, Japan: preliminary work and correlation with Asian Land Mammal Ages

Fig. 5摇 Temporal distributions of Early and Middle Eocene herbivorous mammals ( tillodonts, coryphodontid pantodonts, hyopsodontid condylarths, perissodactyls, and artiodactyls) from China and Mongolia, that are related to Japanese taxa discussed here The distributions are derived from Tong (1989b), Lucas (1998, 2004), Meng and McKenna (1998), Ting (1998), Tong and Wang (1998, 2006), Bowen et al. (2002), Kondrashov (2004), Kondrashov et al. (2004), and M伢tais et al. (2004). Light gray area shows the preferred chronological and biostratigraphic zone related to the mammal taxa from the Akasaki and Nakakoshiki formations standing of East Asian mammalian assemblages of this age. Artiodactyls and hyopsodontid con鄄 dylarths are very rare elements in Arshantan assemblages on the Asian mainland. The Japanese faunas apparently sample a more coastal habitat or biome that differed appreciably from those which yield typical Arshantan assemblages from the Asian mainland. Acknowledgments 摇 We wish to express our appreciation to Drs. Qiu Zhuding, Li Chuankuei, Wang Yuanqing, and Wang Yuan, for critical comments and assistance in accessing the collec鄄 tions in the IVPP, Beijing, People爷s Republic of China. We thank Dr. Kazuto Kodama (Ad鄄 vanced Marine Core Research, Kochi University) for consulting and generous supporting for the geomagnetic tests. References

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Brachyodus Brachyodus B. ja鄄 p摇 on摇icuTshe taxonomic status of “ Desmato冶thesrpieucmimegnrsan(g“eri 冶 sp., no. 11; “ 冶 , no. 19 in the list) and “ 冶 (no. 10 in the list, see also Toku鄄 naga, 1933a, b; Takai, 19B4r4a)chyaordeuds ebatable. Dineur (1982 ) and Ducrocq and Lihoreau (2006) prEolpoomsedryxthat the “ 冶 specimens from Japan are “very probably冶 refeBra.blejato鄄 pthoenigceunsus , whereas Kato (1997) anBdotKhraitoodoand Otsuka (1999) noted that “ 冶D. grangeriis probably assignable to the genus . Takai (1944) described the “ 冶 specimen consisting right p2, p4, and a fragment of mC1olforodmonthe gUrbaengGeroiup, Yamagu鄄 chi Prefecture. Later, Russell and Zhai (1987) listed it as “ ?冶 based onDt.he gtarxaonngoemriic comments of Radinsky (1965) for the holotype and referred specimens of “ 冶 Desmatoftrhoemriuthme HgorsaanngeCrioalfieCldo,loNdoonrth Kgorarenage(riDemocratic People爷 s Republic of Korea). P“lesiocolopirus 冶 or “ ?冶 from North Korea is reassigned to the genus Schoch, 1989 by TomidDa.andgrLain(g2er0i04). However, Radinsky (1965) and later other workers have not examined the “ 冶 specimen from Ube Group directly (proba鄄 blDyemsmisastiontgh)eriuanmd ngortancglaerified its taxonomic status; thus, we retain it here as problematic “ 冶 . On the otherPlheasinodc,oloIiphirousshigraanndgNeraikaya (2010) recently reported a tapiroid specimen probably referable to (Tokunaga, 1933) from Hok鄄 kaido (no. 2 in thPe. ligsrta)n;gethrie.ir assignment is based on the comparison and the similarity with the North Korean

Locality map: the numbers (1-25) correspond to those of the list References in Appendix 1

130 1摇 Belyaeva E I, 1971. Novye dannye po aminodontam SSSR. Akad Nauk SSSR Tr Paleont Inst, : 39-61(in Russian) Entelodon orientalis 2摇 Dashzeveg D, 1965. n. sp. ( Suiformes) from the Oligocene of the Gobi Desert, Mongolia. Acta 10 Palaeont Pol, (2): 281-285 期 Miyata et al.:Eocene mammals from the Akasaki and Nakakoshiki formations, western 1 摇 67 Kyushu, Japan: preliminary work and correlation with Asian Land Mammal Ages Brachyodus 3摇 Dineur H, 1982. Le genre , Anthracotheriidae (Artiodactyla, Mammalia) du Mioc侉ne inf伢rieur d爷 Europe et 6 d爷Afrique. M伢m Sci Terre, Univ Paris, : 1-186 4摇 Ducrocq S, Lihoreau F, 2006. The occurrence of bothriodontines (Artiodactyla, Mammalia) in the Paleogene of Asia with Elomeryx 27 special reference to : paleobiogeographical implications. J Asian Earth Sci, (6): 885-891 5摇 Hasegawa Y, Suyama Y, Kameyama A, 2007. Fossil turtle from the Upper Oligocene, Taoyama Formation, Hioki Group, 11 in Tobou鄄cho, Shimonoseki, Yamaguchi, Japan. 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