Small Mammal Fauna from Wulanhuxiu (Nei Mongol, China) Implies the Irdinmanhan—Sharamurunian (Eocene) Faunal Turnover Author(s): Qian Li, Yuan-Qing Wang and Łucja Fostowicz-Frelik Source: Acta Palaeontologica Polonica, 61(4):759-776. Published By: Institute of Paleobiology, Polish Academy of Sciences URL: http://www.bioone.org/doi/full/10.4202/app.00292.2016 BioOne (www.bioone.org) is a nonprofit, online aggregation of core research in the biological, ecological, and environmental sciences. BioOne provides a sustainable online platform for over 170 journals and books published by nonprofit societies, associations, museums, institutions, and presses. Your use of this PDF, the BioOne Web site, and all posted and associated content indicates your acceptance of BioOne’s Terms of Use, available at www.bioone.org/page/terms_of_use. Usage of BioOne content is strictly limited to personal, educational, and non-commercial use. Commercial inquiries or rights and permissions requests should be directed to the individual publisher as copyright holder. BioOne sees sustainable scholarly publishing as an inherently collaborative enterprise connecting authors, nonprofit publishers, academic institutions, research libraries, and research funders in the common goal of maximizing access to critical research. Small mammal fauna from Wulanhuxiu (Nei Mongol, China) implies the Irdinmanhan–Sharamurunian (Eocene) faunal turnover QIAN LI, YUAN-QING WANG, and ŁUCJA FOSTOWICZ-FRELIK Li, Q., Wang, Y.-Q., and Fostowicz-Frelik, Ł. 2016. Small mammal fauna from Wulanhuxiu (Nei Mongol, China) implies the Irdinmanhan–Sharamurunian (Eocene) faunal turnover. Acta Palaeontologica Polonica 61 (4): 759–776. Wulanhuxiu, a middle Eocene locality in the Erlian Basin, Nei Mongol (China) has been commonly regarded as belong- ing to the Ulan Shireh Formation, equated with the Irdin Manha Formation. We recognized two separate mammalian faunas of different age from the beds exposed at Wulanhuxiu. The lower fossiliferous horizon contains an anagalid, uncommon duplicidentate representatives (Gomphos progressus sp. nov., Mimolagus, Erenlagus, and Strenulagus), and diverse perissodactyls. This combination of taxa points to an Irdinmanhan age, but one element of the fauna (Schlosseria) may represent an Arshantan relic. Overall, the assemblage comprises “paleoplacental” mammals mixed with “neopla- centals”. The upper horizon is less species-rich and the only paleoplacentals present are scarce creodonts. However, this horizon is marked by abundant remains (including postcranial material) of the lagomorph Gobiolagus and by the presence of an advanced form of Gobiomys (Rodentia), and is most probably Sharamurunian in age. Thus, Wulanhuxiu documents replacement, albeit incomplete, of paleoplacentals by neoplacentals in the Chinese Eocene record. Key words: Mammalia, Rodentia, Duplicidentata, Anagalidae, Eocene, Ulan Shireh Formation, China, Erlian Basin. Qian Li [[email protected]] and Yuan-Qing Wang [[email protected]], Key Laboratory of Vertebrate Evolu- tion and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, China. Łucja Fostowicz-Frelik [[email protected]] (corresponding author), Institute of Paleobiology, Polish Academy of Sciences, ul. Twarda 51/55, PL 00-818 Warsaw, Poland. Received 5 May 2016, accepted 23 September, available online 17 October 2016. Copyright © 2016 Q. Li et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License (for details please see http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. (“Chimney Butte”) in 1928 (Radinsky 1964). The “Chimney Introduction Butte” locality (which includes the famous “Buckshot Quarry”) is now called Wulanhuxiu (Wang et al. 2012). The Erlian Basin lies in northern China, in the central part The most important CAE results concerning the “Chimney of Nei Mongol (Inner Mongolia). Its Paleogene deposits Butte” mammalian fauna include descriptions of pantodonts have yielded rich fossil mammal assemblages, especially such as Pantolambdodon inermis and P. fortis (Granger and of Eocene age, providing the basis for several Paleogene Gregory 1934), brontotheriids such as Des ma to titan tukhu- Asian Land Mammal Ages or ALMAs (see Holroyd and mensis, Epimanteoceras formosus, Pro titan grangeri (= bel- Ciochon 1994; Meng and McKenna 1998; Luterbacher et lus), and Microtitan mon go liensis (Granger and Gregory al. 2004). The eastern part of the basin in the vicinity of 1943), small tapiroids such as Breviodon and Rhodopagus Erenhot has been relatively well studied. However, the west- (Radinsky 1965), the creodont Sarkastodon mongoliensis ern part, including the area in the vicinity of the Shara (Granger 1938), the rodent Advenimus bohlini (Dawson Murun River, remains poorly known. The Central Asiatic 1964) and the lagomorph Shamolagus grangeri (Burke Expeditions (CAEs) of the American Museum of Natural 1941), the mesonychid ?Harpagolestes orientalis (Szalay History surveyed Baron Sog Mesa and North Mesa west of and Gould 1966), and the didymoconid Kennatherium shi- the Shara Murun River in the 1920s. In 1925 they collected rensis (Mellet and Szalay 1968). More material was col- intensively at two localities in the area of North Mesa, de- lected by a Sino-Soviet expedition in 1959, and by IVPP scribed as “4 and 8 miles north of Tukhum Lamasery”, and field-parties from 1975 onward (Chow and Rozhdestvensky they returned to the locality “eight miles north of Tukhum” 1960; Russell and Zhai 1987). However, no further infor- Acta Palaeontol. Pol. 61 (4): 759–776, 2016 http://dx.doi.org/10.4202/app.00292.2016 760 ACTA PALAEONTOLOGICA POLONICA 61 (4), 2016 mation on the mammalian fauna from this region has been 111 00' E A Wulanhuxiu B Erlian reported, apart from a review by Ye (1983). Basin North Viper Camp Here we focus on the fossil assemblage of small mammals Mesa from Wulanhuxiu based on new material collected from that CHINA locality over the past decade. In particular, the Glires (ro- 1040 Tukhum Lamasery dents, lagomorphs, and their closest relatives) fauna from this 1070 1010 locality provides new data on the age and paleoenvironment 10 km of the Ulan Shireh Formation (exposed only at North Mesa) and enhances our knowledge of the regional aspects of the 1040 1070 middle Eocene mammal fauna in the western Erlian Basin. 1130 In analyzing the Wulanhuxiu assemblage we found Lucas’s 1100 (2001: 230) proposed dichotomy between “paleoplacentals” Shara Murun River Ula Usu 42 30'N 1130 and “neoplacentals”, which stems directly from Osborn’s 1160 concept of mesoplacentals and cenoplacentals (Osborn 1894; Baron Sog Mesa Twin Oboes Osborn and Earle 1895), to be useful. The paleoplacentals (West Mesa) 1160 East Mesa 1100 Jhama Obo were understood by Lucas (2001) as mammalian groups of Baron Sog Lamasery a Paleogene radiation, all of which lack surviving descen- C dants and were characterized by an archaic tooth struc- ture and poorly developed brain. According to Lucas (2001) these groups included Anagalida, Condylarthra, Creodonta, Dinocerata, Mesonychia, Notoungulata, Pantodonta, and Tillodontia, whereas neoplacentals included all groups with extant representatives (“the placentals of modern aspect”). Neoplacentals would then include, for example, artiodac- tyls, carnivorans, chiropterans, lagomorphs, perissodactyls, primates, and rodents. Furthermore, a degree of parallelism existed between the paleoplacental and neoplacental radia- tions. Eurymylidae and Mimotonidae, for instance can be regarded as paleoplacental counterparts of modern Glires (Rodentia and Lagomorpha, respectively). The replacement D of the paleoplacentals by neoplacentals in Asian faunas con- layer 1 tinued through the Eocene; thus, the two groups coexisted mudstone layer 2 for some 20 million years, although the major turnover oc- sandstone curred most probably during the Arshantan–Irdinmanhan cross-bedding (Lucas 2001). At Wulanhuxiu, we document a remarkable fossil ocurrence 10 m replacement of some extinct “paleoplacental” clades (anaga- lids and mimotonids) by their modern “neoplacental” coun- terparts (lagomorphs and rodents), in addition to a decrease layer 3 in ungulate diversity. 0 layer 4 Institutional abbreviations.—IVPP, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Fig. 1. A. Location of the Wulanhuxiu mammalian fossil site in the western part of the Erlian Basin (elevations given in meters; modified from Russell Sciences, Beijing, China. and Zhai 1987). B. Map of continental China (Nei Mongol Autonomous Region in gray). C. Typical landscape at the Wulanhuxiu locality show- ing fossiliferous beds with the Irdinmanhan–Sharamurunian transition. D. Stratigraphic section of the studied sediment series at Wulanhuxiu (after Geological setting a field sketch by Bin Bai). The Wulanhuxiu locality lies in the western part of the (layer 1) lacks any fossil remains. Layer 2, located just be- Erlian Basin on the northern side of the North Mesa (Fig. 1). low, is the thickest in the profile and contains fossil bones According to Russell and Zhai (1987: fig. 54), a representa- and teeth. It is composed of white mudstone, which become tive section of the Ulan Shireh Formation (note that a type greenish towards the bottom. In the upper part of the layer a section has not been formally specified)