A New Large Beaver (Mammalia, Castoridae) from the Early Miocene of Japan

ABSTRACT A new early Miocene large castorid, Minocastor godai gen. et sp. nov., from the Dota locality, Gifu Prefecture in central Japan, is described on the basis of dentaries and teeth. The material comes from the Kani basin, where limnofluviatile clay and sandstones of the Nakamura Formation (Mizunami Group) are exposed on the southern (left) bank of the Kiso River. It represents the richest sample of a Miocene small mammal in the Japanese fossil record thus far known. Based on jaw and tooth morphology, this new castorid most likely represents a primitive anchitheriomyine. However, it lacks the marked striations on the incisors that are characteristic of the advanced large, middle Miocene anchitheriomyines like Anchitheriomys and Amblycastor. The new castorid shares this dental feature with other primitive anchitheriomyines from Asia and North America, like Propalaeocastor, Oligotheriomys, and Miotheriomys. For these genera, a new tribe, Minocastorini, is proposed as sister group to the Anchitheriomyini. The incisor enamel microstructure of the new castorid largely exhibits plesiomorphic characters but also apomorphic features such as pseudo-pauciserial Hunter-Schreger bands. Additionally, the outer portion of the enamel band is rather thick in comparison to that of other beavers. Based on the rodent taxa associated with Minocastor godai gen. et sp. nov., Dota can be correlated with European Neogene mammal units MN 3/4. Magnetostratigraphic studies and radiometric dates obtained from the Mizunami Group indicate that Dota is more likely correlated with MN 3, with an absolute age of around 18.5 Ma.

[1]  J. Samuels,et al.  New Rodent Material from the John Day Formation (Arikareean, Middle Oligocene to Early Miocene) of Oregon , 2015 .

[2]  L. Grande,et al.  A New Miocene Amiid Fish, Amia godai from Kani, Gifu, Central Japan , 2013 .

[3]  K. Miyata,et al.  Miocene Land Mammals and Stratigraphy of Japan , 2013 .

[4]  Zhaohao Zhang,et al.  Neogene Land Mammal Stages/Ages of China , 2013 .

[5]  Y. Tomida.  New Species of Alloptox (Lagomorpha, Ochotonidae), First Record of the Genus in Japan, and Subgeneric Distinction , 2012 .

[6]  S. Kawano,et al.  X-Ray Computed Tomography Examination of a Fossil Beaver Tooth from the Lower Miocene Koura Formation of Western Japan , 2011 .

[7]  Y. Chaimanee,et al.  First Castorid (Mammalia, Rodentia) from the Middle Miocene of Southeast Asia , 2011, Naturwissenschaften.

[8]  Y. Tomida.  A new species of the genus Megapeomys (Mammalia, Rodentia, Eomyidae) from the Early Miocene of Japan , 2011 .

[9]  T. Mörs,et al.  Anchitheriomys Roger, 1898 or Amblycastor Matthew, 1918 (Rodentia, Castoridae)? Taxonomic Implications of a Mandible from the Miocene of Florida , 2010 .

[10]  K. Miyata,et al.  Anchitherium (Mammalia, Perissodactyla, Equidae) from the Early Miocene Hiramaki Formation, Gifu Prefecture, Japan, and its Implication for the Early Diversification of Asian Anchitherium , 2010, Journal of Paleontology.

[11]  T. Mörs,et al.  The Castorid Steneofiber from NW Germany and Its Implications for the Taxonomy of Miocene Beavers , 2010 .

[12]  L. W. H. Ostende,et al.  A revision of Late Oligocene associations of small mammals from the Aral Formation (Kazakhstan) in the National Museum of Georgia, Tbilissi , 2009 .

[13]  T. Mörs,et al.  The Beaver Anchitheriomys from the Miocene of Central Europe , 2008, Journal of Paleontology.

[14]  L. Jacobs,et al.  Evolution of Tertiary Mammals of North America: Castoroidea , 2008 .

[15]  N. Rybczynski.  Castorid Phylogenetics: Implications for the Evolution of Swimming and Tree-Exploitation in Beavers , 2007, Journal of Mammalian Evolution.

[16]  Deng Tao.  CHINESE NEOGENE MAMMAL BIOCHRONOLOGY , 2006 .

[17]  W. Korth.  Beavers (Rodentia, Castoridae) from the Runningwater Formation (Early Miocene, Early Hemingfordian) of western Nebraska , 2004, Annals of the Carnegie Museum.

[18]  W. Korth.  Comments on the Systematics and Classification of the Beavers (Rodentia, Castoridae) , 2001, Journal of Mammalian Evolution.

[19]  Xijun Ni,et al.  Propalaeocastor (Rodentia, Mammalia) from the Early Oligocene of Burqin Basin, Xinjiang , 2004 .

[20]  P. Dodson,et al.  A PROPOSAL FOR A STANDARD TERMINOLOGY OF ANATOMICAL NOTATION AND ORIENTATION IN FOSSIL VERTEBRATE DENTITIONS , 2003 .

[21]  C. Stefen,et al.  Trogontherium (Euroxenomys) minutum (Castoridae: Mammalia) from Petersbuch 50, Miocene, South Germany , 2003 .

[22]  Y. Yanagisawa,et al.  An unconformity in the early Miocene syn‐rifting succession, northern Noto Peninsula, Japan: Evidence for short‐term uplifting precedent to the rapid opening of the Japan Sea , 2002 .

[23]  T. Mörs,et al.  The enamel microstructure ofAnchitheriomys (Rodentia, Mammalia) in comparison with that of other beavers and of porcupines , 2001 .

[24]  Gertrud E. Rössner,et al.  The Miocene : land mammals of Europe , 1999 .

[25]  Y. Tomida,et al.  NEW EOMYID GENUS AND SPECIES FROM THE EARLY MIOCENE (MN ZONES 3-4) OF EUROPE AND JAPAN RELATED TO APEOMYS (EOMYIDAE, RODENTIA, MAMMALIA) , 1998 .

[26]  W. Korth,et al.  The skull of Anchitheriomys and a new subfamily of beavers (Castoridae, Rodentia) , 1997, Journal of Paleontology.

[27]  W. Korth.  A new genus of beaver (Mammalia: Castoridae: Rodentia) from the Arikareean (Oligocene) of Montana and its bearing on castorid phylogeny , 1996, Annals of the Carnegie Museum.

[28]  T. Setoguchi,et al.  A New Record of Youngofiber (Castoridae : Mammalia) from the Early Miocene of Kani City, Central Japan , 1995 .

[29]  O. Hiroyuki,et al.  DISCOVERY OF THE OLIGO-MIOCENE RODENTS FROM WEST JAPAN AND THEIR GEOLOGICAL AND PALEONTOLOGICAL SIGNIFICANCE , 1995 .

[30]  Chuangjiu Li,et al.  Rodent and Lagomorph families of Asian origins and diversification : proceedings of Workshop WC-2, 29th International Geological Congress, Kyoto, Japan , 1994 .

[31]  Xiaofeng Xu.  EVOLUTION OF CHINESE CASTORIDAE , 1994 .

[32]  T. Setoguchi,et al.  TERTIARY RODENTS FROM JAPAN , 1994 .

[33]  M. Torii,et al.  Paleomagnetism of the Early Miocene Kani Group in southwest Japan and its implication for the opening of the Japan Sea , 1991 .

[34]  D. Mayhew.  Reinterpretation of the Extinct Beaver Trogontherium (Mammalia, Rodentia) , 1978 .

[35]  H. Freye.  Deskriptive Anatomie des Craniums vom Elbe-Biber (Oastor fiber albicus Matschie 1907) , 1959 .

[36]  H. E. Wood,et al.  Late Miocene beaver from southeastern Montana. American Museum novitates ; no. 1299 , 1945 .

[37]  R. A. Stirton.  A new species of Amblycastor from the Platybelodon beds, Tung Gur Formation, of Mongolia. American Museum novitates ; no. 694 , 1934 .

[38]  W. Matthew,et al.  Contributions to the Snake Creek fauna ; with Notes upon the Pleistocene of western Nebraska, American Museum Expedition of 1916. Bulletin of the AMNH ; v. 38, article 7. , 1918 .

[39]  H. E. Wood.  LATE MIOCENE BEAVER FROM SOUTHEASTERN MONTANA BY , 2022 .