Two New Ammonoid Genera of the Subfamily Gabbioceratinae from the Upper Albian (Lower Cretaceous) of Hokkaido, Japan
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208Paleontological Research, vol. 16, no. 3, pp. 208–218, SeptemberYasunari 30, 2012 Shigeta et al. © by the Palaeontological Society of Japan doi:10.2517/1342-8144-16.3.208 Two new ammonoid genera of the subfamily Gabbioceratinae from the Upper Albian (Lower Cretaceous) of Hokkaido, Japan 1 2 3 YASUNARI SHIGETA , MASAO FUTAKAMI AND RENÉ HOFFMANN 1Department of Geology and Paleontology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005, Japan (e-mail: [email protected]) 2Paleontological laboratory, Kawamura Gakuen Womanތs University, Abiko, Chiba 270-1138, Japan 3Institut für Geologie, Mineralogie und Geophysik, Ruhr-Universität Bochum, Universitätsstr. 150, Bochum D-44801, Germany Received October 14, 2010; Revised manuscript accepted March 13, 2012 Abstract. Two ammonoids of the subfamily Gabbioceratinae, Obataceras manjiense gen. et sp. nov. and Tanabeceras pombetsense gen. et sp. nov., are described from the Upper Albian of Hokkaido, Japan. The Gabbioceratinae evolved and radiated mainly in the Mediterranean area during Late Aptian to Middle Albian times, but thereafter disappeared from the region. The occurrences of Gabbioceratinae in Hokkaido VXJJHVWWKDWWKHLUJHRJUDSKLFDOGLVWULEXWLRQZDVH[WHQGHGWRWKH1RUWKZHVW3DFL¿FEHIRUHWKH/DWH$OELDQ ZKHUHWKH\WKHQÀRXULVKHGIURP/DWH$OELDQWR&HQRPDQLDQWLPH Key words: Albian, ammonoid, Cretaceous, Gabbioceratinae, Obataceras, Tanabeceras Introduction ceratinae have been reported from the Aptian and Albian LQWKH1RUWKZHVW3DFL¿F The subfamily Gabbioceratinae Breistroffer, 1953 of Although gaudryceratid ammonoids occur abundantly the family Gaudryceratidae Spath, 1927 is character- in the Albian of Hokkaido and Sakhalin, they are mainly ized by having highly depressed whorls with an angular restricted to the genera Anagaudryceras Shimizu, 1934 umbilical shoulder at certain growth stages. Two gen- and Zelandites Marshall, 1926 (Matsumoto, 1938; Obata era, Gabbioceras Hyatt, 1900 and Jauberticeras Jacob, et al., 1981; Futakami, 1982, 1996). There have been a 1907, have been traditionally recognized within the sub- IHZUHSRUWVRIVSHFLPHQVWHQWDWLYHO\LGHQWL¿HGDVPara- family (Murphy, 1967a; Klein et al., 2009; Hoffmann, jaubertella Matsumoto, 1943 from the Manji and Mikasa 2010). Gabbioceras lamberti (Breistroffer, 1937), the areas of central Hokkaido (Obata and Futakami, 1977; oldest member of the subfamily, from the lower Upper Futakami, 1996). However, Parajaubertella has a highly Aptian is considered to be an offshoot of Eogaudryceras depressed but rounded whorl section and is very similar Spath, 1927 (Wiedmann, 1962). The subfamily evolved to Gabbioceras, but it lacks a pronounced lateral angu- and radiated in the lower to middle latitudes during Late lation (Matsumoto, 1943). Wiedmann (1962) considered $SWLDQDQG$OELDQWLPHDQGLQWKH1RUWKZHVW3DFL¿FDQG the genus to be a synonym of Gabbioceras, but both Madagascar during Cenomanian time (Murphy, 1967a; genera can be clearly distinguished by the differences in Collignon, 1964; Shigeta, 1996). umbilical shape, suture line and other characters (Mur- In Hokkaido (Japan) and Sakhalin (Russia), two phy, 1967a; Jones, 1967; Matsumoto, 1995; Hoffmann, endemic species of Gabbioceras have been described 2010). from the Lower to Middle Cenomanian of the Yezo We recently examined the specimens assigned to Group (Shigeta, 1996; Nishida et al., 1997; Hayakawa Parajaubertella aff. kawakitana Matsumoto, 1943 by and Nishino, 1999; Kawabe, 2000; Yazykova et al., Obata and Futakami (1977) and Futakami (1996) from 2004). However, no specimens referable to the Gabbio- the Albian of Hokkaido, and we herein recognize them Albian Gabbioceratinae from Hokkaido 209 as members of the Gabbioceratinae. In this paper, we cation established by Klein et al. (2009). Morphologi- GHVFULEHWKHPDQGGLVFXVVWKHLUELRJHRJUDSKLFDOVLJQL¿- cal terms in the systematic description are those used in cance. the Treatise on Invertebrate Paleontology (Moore, 1957). 4XDQWL¿HUVXVHGWRGHVFULEHWKHVKDSHRIDPPRQRLGVKHOO Notes on stratigraphy replicate those proposed by Matsumoto (1954, p. 246) DQGPRGL¿HGE\+DJJDUW WDEOH The Cretaceous Yezo Group, ranging in age from Abbreviations for shell dimensions.—D = shell diame- Aptian to Maastrichtian, is widely distributed in a ter; U = umbilical diameter; H = whorl height; W = whorl 1000 km-long outcrop belt running in a north-south direc- width. tion in the central zone of Hokkaido, Japan and the West Suture line terminology and abbreviations.—We uti- Sakhalin Mountains, Russia (Matsumoto, 1954; Shigeta lize the suture line terminology and abbreviations of and Maeda, 2005). Their sediments are㻌thought to have Wedekind (1916). E = external lobe; L= lateral lobe; been deposited in the ancient Yezo forearc basin along U1 ¿UVWXPELOLFDOOREH82 = second umbilical lobe; U3 = the eastern margin of the paleo-Asian continent (Okada, third umbilical lobe; IS = septal lobe. See also Kullmann 1979, 1983). and Wiedmann (1970). In the Manji and Mikasa areas, the Yezo Group ranges Institution abbreviations.—NMNS = National Museum from the Albian to the Santonian and is subdivided into of Nature and Science, Tsukuba; MCM = Mikasa City the Hikagenosawa, Mikasa and Haborogawa formations, Museum, Mikasa. in ascending order (Takashima et al., 2004). The Hikage- nosawa Formation consists of laminated mudstone with Superfamily Tetragonitoidea Hyatt, 1900 sandstone-bed intercalations, while the Mikasa Forma- Family Gaudryceratidae Spath, 1927 WLRQLVFRPSULVHGPDLQO\RIKXPPRFN\FURVVVWUDWL¿HG Subfamily Gabbioceratinae Breistroffer, 1953 sandstone (Ando, 1990). Mudstones of the Hikagenosawa Formation contain rare, poorly preserved Albian mega- This group is characterized by highly depressed whorls fossils, but well preserved fossils are sometimes found with an angular umbilical shoulder at certain growth within calcareous concretions (Obata and Futakami, stages (Murphy, 1967a, 1967b). The suture shows 1975; Futakami, 1996). Much of the Mikasa Formation early gaudryceratid-type characteristics (see following is fossiliferous with Early Cenomanian to Late Turonian description and discussion). ammonoids and inoceramids occurring abundantly in Composition.—Four genera: Gabbioceras Hyatt, both the host rock and calcareous concretions (Matsu- 1900, Jauberticeras Jacob, 1907, Obataceras Shigeta, moto, 1965; Obata and Futakami, 1975; Ando, 1990). Futakami and Hoffmann gen nov. and Tanabeceras The Haborogawa Formation consists mainly of biotur- Shigeta, Futakami and Hoffmann gen nov. constitute the bated mudstone interbedded with white tuff layers and VXEIDPLO\7KH¿UVWWZRJHQHUDDUHEULHÀ\QRWHGDQGWKH spherical calcareous concretions, which contain well pre- latter two are newly described below. served Coniacian to Santonian ammonoids and inocera- Remarks.—Traditionally, two genera, Gabbioceras mids (Obata and Futakami, 1975). and Jauberticeras, have been recognized within the sub- One specimen assigned to Parajaubertella aff. kawaki- family Gabbioceratinae (Murphy, 1967a; Klein et al., tanaE\)XWDNDPL ZDVREWDLQHGIURPDÀRDWFDO- 2009; Hoffmann, 2010), but we herein propose the addi- careous concretion at Loc. Pn1032F along the middle tion of two new genera, Obataceras and Tanabeceras, reaches of the Pombetsu River in the Mikasa area. The based on distinct characters without intermediate forms. other four specimens, one of which was illustrated, were These characters include 1) a slightly convex or rounded H[WUDFWHGE\2EDWDDQG)XWDNDPL IURPÀRDW venter, 2) an aperture whose ventral portion is either blocks of cold-seep carbonate at Loc. SK1F11 and 1F31 convex or slightly concave, and 3) a suture with two or along the upper reaches of the Shikoro-zawa River in the WKUHHZHOOGH¿QHGXPELOLFDOOREHV )LJXUH ,QJHQHUDO, Manji area. Although it is uncertain from which horizons the apertural shape and suture line are stable among the the concretion and blocks came, judging from the locali- higher taxonomic groups of ammonoids (Wright et al., ties at which they were found and their matrix types, they 1996). almost certainly came from the Hikagenosawa Forma- Occurrence.—Upper Aptian to Middle Cenomanian. tion. Genus Jauberticeras Jacob, 1907 Paleontological description Type species.—Ammonites jaubertianus d’Orbigny, 6\VWHPDWLF GHVFULSWLRQV EDVLFDOO\ IROORZ WKH FODVVL¿- 1850. 210 Yasunari Shigeta et al. 1 Hungary, and Caucasus, Albian of Madagascar, South slightly convex rounded venter Africa, southern France and Caucasus (Wiedmann, 1962; venter Collignon, 1964; Drushchits, 1960; Murphy, 1967a; Sharikadze et al., 1974; Kennedy and Klinger, 1977; Szives et al., 2007). Genus Gabbioceras Hyatt, 1900 Type species.—Ammonites batesi Gabb, 1869 (non Trask, 1855) = Lytoceras (Gabbioceras) angulatum Anderson, 1902. Emended diagnosis.—Gabbioceratinae having rounded 2 venter, depressed whorls and moderately wide, funnel- shaped umbilicus with angular umbilical shoulder at pre- DGXOWJURZWKVWDJH*URZWKOLQHV¿QHULEVDQGFRQVWULF- convex tions project forward on venter. Remarks.—The suture line formula of Gabbioceras concave angulatum and G. lamberti is ELU2U1IS, showing early JDXGU\FHUDWLGW\SH FKDUDFWHULVWLFV ZLWK EL¿G ODWHUDO 3 VDGGOHDQGWZRZHOOGH¿QHGXPELOLFDOOREHV7KHODWHUDO angulation is located in the middle of U2 (Murphy, 1967a; L E L E Hoffmann, 2010). U2 U Occurrence.—Upper Aptian of southern France, U2 3 Hungary, Caucasus, and northern California, Lower U1 U1 Albian of Madagascar and southern France (Wiedmann, 1962; Collignon, 1964; Murphy, 1967a; Egoian, 1969; LA US LA US Szives et al., 2007). two umbilical