An updated mammal biochronology and biogeography for the paleocene and early eocene of Asia

Paleomammalogists often use a biochronological system of regional Land Mammal Ages (LMAs) to designate intervals of time defined by specific events in the evolutionary history of mammals. In North America and Europe, this biochronological framework is fairly well known and has been partially correlated to the global timescale (Secord et al. 2006; Smith & Smith 2003). The Asian early Paleogene mammal biochronology is less precise, due to our previously limited knowledge of these faunas. Moreover, the endemic nature of these Asian faunas and the few absolute ages available have made the correlation and dating of these faunas problematic. Wang et al. (2007) provided a recent synthesis of the Chinese Paleogene mammal radiations, but Ting (1998) was the last to provide a detailed study of the Paleocene and Early Eocene Asian LMAs (ALMAs). However, in the past decade research efforts have rapidly increased the available data on the Asian faunas, creating the need for a detailed update of the existing biochronological framework and its biogeographical interpretation. Faunal data from Asian early Paleogene mammal sites were analysed with Appearance Event Ordination to obtain a temporally ordered faunal succession. Faunal data and analysis results were studied in detail to define biochronological boundaries corresponding to major faunal turnovers, and to clearly characterise the different ALMAs. The new biochronology allows an improved correlation of ALMAs with North American and European LMAs, and to better understand the biogeography of Paleocene and Early Eocene Asian mammals. The poorly known Shanghuan represents the oldest Paleocene ALMA, and is characterised by an assemblage dominated by primitive gliriforms and pantodonts. The following Nongshanian ALMA is characterised by an endemic specialisation and diversification. Especially gliriforms radiate, with the diversification of Anagalidae and Pseudictopidae, the first appearance of the gliriform family Arctostylopidae, and, most notably, the appearance of true Glires, represented by Eurymylidae and Mimotonidae. The poor knowledge and primitive, endemic nature of the Shanghuan and Nongshanian faunas complicates their correlation, but the Shanghuan-Nongshanian boundary is often correlated with the Torrejonian-Tiffanian boundary in North America, and this hypothesis was recently magnetostratigraphically corroborated (Clyde et al. 2008). Both boundaries thus seem to represent independent but synchronous turnovers of endemic taxa, and were possibly triggered by the start of a period of global cooling. The Gashatan ALMA is characterised by the first appearance of rodents, prodinoceratids and hyaenodontids, all of which supposedly evolved in Asia. However, neoplagiaulacids, nyctitheriids, cimolestids and carpolestids also make their first appearance in Asia during the Gashatan, and represent North American immigrants (Missiaen and Smith 2008). Conversely, during this period Asian mammals were also able to invade North America, with a first wave consisting of arctostylopids and prodinoceratids arriving at the start of Tiffanian-5a, and a second wave consisting of rodents, tillodonts and coryphodontids at the start of the Clarkforkian (Secord et al. 2006). The start of the Gashatan is thus no younger than Tiffanian-5a, but may prove to be even older. Although it is not possible to constrain the exact timing or duration of these migration waves at the start of the Gashatan, available evidence is most consistent with two discrete dispersal intervals approximately 1.3 Ma apart. The Bumbanian ALMA is characterised by the first appearance of artiodactyls, perissodactyls and primates, similar to their appearance in North America and Europe at the start of the Eocene, and the Gashatan-Bumbanian boundary is traditionally correlated to the Paleocene-Eocene boundary. Contrasting with dispersal at the start of the Gashatan, dispersal during the Bumbanian seems to have been possible during a more extended period of time and was also possible directly between Asia and Europe (Ting 1998; Smith et al. 2006)

The Gashatan (late Paleocene) mammal fauna from Subeng, Inner Mongolia, China

The Paleocene–Eocene boundary is of particular importance for the evolution of mammals and the poorly known Asian mammal faunas from this period have received much attention. The late Paleocene Subeng site in Inner Mongolia (China) has come under study only recently, and here we present the first complete description of its mammal fauna. Two new species are described, the neoplagiaulacid multituberculate Mesodmops tenuis sp. nov. and the praolestine nyctitheriid Bumbanius ningi sp. nov., representing stratigraphic range extensions of the respective genera into the Paleocene. Previ− ously unknown parts of the dentition are described here for the eurymylid Eomylus bayanulanensis, the sarcodontid Hyracolestes ermineus, the cimolestid Tsaganius ambiguus, the carpolestid Subengius mengi, as well as the femur of the mesonychid Dissacus serratus. For most taxa, the new specimens from Subeng provide new phylogenetic and/or biostratigraphic information. We confirm the inclusion of Hyracolestes in the Sarcodontinae and elevate this group to the rank of family, the Sarcodontidae, separate from Micropternodontidae. In the case of Subengius mengi an updated cladistic analysis of carpolestids supports the hypothesis that Subengius is derived from an evolved Elphidotarsius−like ancestor in the early to middle Tiffanian of North America. A total of 17 species is identified, including well−known biostratigraphic markers for the late Paleocene Gashatan Asian Land Mammal Age such as Lambdopsalis bulla, Prionessus sp., Palaeostylops iturus, Pseudictops lophiodon, Tribosphenomys minutus, and Dissacus serratus.We pro− pose that the Gashatan faunas are less endemic than previously thought, and result from a significant exchange with North American faunas from the late Paleocene

Cymbalophus cuniculus from the early Eocene of Erquelinnes (Belgium), and its implications for basal Perissodactyl phylogeny

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New Basal Perissodactyla (Mammalia) From The Lower Eocene Ghazij Formation of Pakistan

http://deepblue.lib.umich.edu/bitstream/2027.42/109436/1/Contributions32No8-12082014.pdfDescription of Contributions32No8-12082014.pdf : Contributions Volume 32, Number

A new species of Archaeoryctes from the Middle Paleocene of China and the phylogenetic diversification of Didymoconidae

Didymoconidae are an enigmatic group of Asian endemic insectivorous mammals. We describe the new didymoconid species Archaeoryctes wangi sp. nov. from the Upper Member of the Wanghudun Formation (Middle Paleocene). This new species from the Qianshan Basin (Anhui Province, China) forms an interesting geographical intermediate between A. notialis from South China and A. borealis and A. euryalis from the Mongolian Plateau. To better understand the origin and evolutionary diversification of Didymoconidae, we performed a cladistic and stratocladistic study of the Didymoconidae and various outgroups. This study of dental material did not resolve the higher level affinities of Didymoconidae, but confirms the validity of the family and its distinctiveness from the morphologically similar Sarcodontidae. Moreover, our results corroborate the current didymoconid classification with the distinction of three subfamilies: “Ardynictinae”, Kennatheriinae and Didymoconinae; “Ardynictinae” are a paraphyletic stemgroup for the two other subfamilies. Our results suggest three distinct didymoconid radiations: (1) primitive ardynictines appeared in South China from the start of the Nongshanian; their evolution continues on the Mongolian Plateau with (2) the radiation of more evolved ardynictines and kennatheriines at the start of the Middle Eocene Arshantan and (3) the origin of didymoconines at the start of the Late Eocene Ergilian

High bat (Chiroptera) diversity in the Early Eocene of India

The geographic origin of bats is still unknown, and fossils of earliest bats are rare and poorly diversified, with, maybe, the exception of Europe. The earliest bats are recorded from the Early Eocene of North America, Europe, North Africa and Australia where they seem to appear suddenly and simultaneously. Until now, the oldest record in Asia was from the Middle Eocene. In this paper, we report the discovery of the oldest bat fauna of Asia dating from the Early Eocene of the Cambay Formation at Vastan Lignite Mine in Western India. The fossil taxa are described on the basis of well-preserved fragments of dentaries and lower teeth. The fauna is highly diversified and is represented by seven species belonging to seven genera and at least four families. Two genera and five species are new. Three species exhibit very primitive dental characters, whereas four others indicate more advanced states. Unexpectedly, this fauna presents strong affinities with the European faunas from the French Paris Basin and the German Messel locality. This could result from the limited fossil record of bats in Asia, but could also suggest new palaeobiogeographic scenarios involving the relative position of India during the Early Eocene