Table Of Content

©Paleontological Research, vol.2, no.4, pp.279-282, 1 Fig., December 30, 1998 by the Palaeontological Society of Japan Devonian tentaculitids from Central and Northeast Japan SHUJI NIKO Department of Environmental Studies, Faculty of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima 739-8521, Japan Received 3 July 1998 Revised manuscript accepted 30 September 1998 ; Abstract Two Lochkovian (Early Devonian) species, Tractabilis? sp. and Gotlandellites fukujiensis sp. nov., from the Fukuji Formation, and an Eifelian (Middle Devonian) species, Tentaculites sp., from the Nakazato Formation, are described and comprise the first modem treatment of tentaculitids in Japan. This discovery of Gotlandellites fukujiensis extends the stratigraphie range of the genus, which was previously known from the Early Silurian. Key words: Devonian, Fukuji Formation, Gotlandellites fukujiensis sp. nov., Nakazato Formation, tentaculitids. Introduction Systematic paleontology Tentaculitidsfrom Japan have neverpreviouslyreceived a Phylum Incertae Sedis modern taxonomic treatment. Only Minato et al. (1959) has Class Tentaculitoidea Ljashenko, 1957 earlier pointed outthe occurrence of "Tentaculites" from the Order Tentaculitida Ljashenko, 1955 Devonian Nakazato Formation in the Southern Kitakami Family Tentaculitidae Walcott, 1886 Mountains, Northeast Japan. The purpose of this paper is Genus Tentaculites Schlotheim, 1820 to describe certain tentaculitid species, namely, Tractabilis? sp. and Gotlandellites fukujiensis sp. nov. from the Fukuji Type species.—Tentaculites scalaris Schlotheim, 1820. Formation and Tentaculites sp.fromthe Nakazato Formation, in order to provide taxonomic, biostratigraphic and Tentaculites sp. paleobiogeographic base data. Thus, the present work initiates the up-to-date description of tentaculitid faunas in Figures 1-1a,b,2,3a, b Japan. Description.—Medium-sized for genus, straight conchs The Fukuji species occur in Lochkovian (Early Devonian) with circular cross sections, attaining 17.0mm in length, 1.7 calcareous shale at locality FH-4 and FH-5, for which mm (slightly deformed) in distal diameter; angle of conch geographic and stratigraphie information are given in Niko expansion approximately4-6° proximal conch upto5.5mm ; (1996), in Gifu Prefecture, Central Japan. Specimens in length, with dense annulets, then closelyspaced symmet- examined from the Fukuji Formation are in the rical rings with 0-4 (usually 1 or 2) alternating annulets paleontological collections of the University Museum of the recognized in more distal conch ; ring size and prominence University of Tokyo (UMUT). increase progressively toward distal end, most distal rings The present Tentaculites sp. isbased onfivespecimensof have subtriangular profiles. external molds on a tuffaceous siltstone slab that was kept Discussion.—The present species is somewhat similar to in the Ofunato City Museum (OCM), Iwate Prefecture. Tentaculites bellulus Hall (1876, pi.26, figs.15-18; Hall, 1879, According to the accompanying label, this slab was col- pi.31, figs.15-18; reillustrated by Fisher, 1962, figs.55-1a, b ; lected as a float block in a tributary in the uppermost redescribed byYoderand Erdtmann,1975, pi.1,figs.1-3,6-8) reaches of the Higuchi-zawa valley, Ofunato City, Iwate from the Middle Devonian Hamilton Group in New York. Prefecture, Northeast Japan. This slab is thought to be This species, however, is represented by poorly preserved derived from the Eifelian (Middle Devonian) portion of the external molds, and knowledge ofthe interiorofthe conch is Nakazato Formation, based on its lithology and collecting necessary to characterize the species. site. Although "Tentaculites" (tentaculitid in Kato, 1979) was The classification and terminology of tentaculitids follows listed from the Nakazato Formation by Minato ef al. (1959), Larsson (1979). this species is still undescribed. Material and occurrence—OCM G-SN02—06 from the 280 Shuji Niko Devonian tentaculitids from Japan 281 Nakazato Formation. diameter near distal end angle of conch expansion ranges ; from 4.5° to 5.7°, usually approximately 5 rings strongly Genus Tractabilis Ljashenko, 1969 prominent, monotonous, symmetrical each; ring slopes ; towards convex side of conch with annular slope ofapproxi- Type species—Tractabilis arcticus Ljashenko, 1969. mately 8-20° ; crests round ; density of rings relatively low for genus, 2-3per corresponding conch diameter; inter- Tractabilis? sp. spaces flat to slightly concave, smooth or rarely bearing 1-2 Figures 1-4, 10a 0a.n0n2u-l0et.s05; mmminiimnumsectthiiocnkendesspaorfatcyopnecsh(wUalMlUTin PinWter2s7p4a6c2e,s cirDceulsacrricprtosisons—eScitnigolne,,dsitraamiegthetrcoonfcdhi,st6a.l9emnmd 1i.n8lmenmgth,rwiintghs 2w7i4d6e3)a;nniunltearrnalcosnucrafvaicteiessm;ooctohncohr fwoarlmls viemrpyunschtaaltleo;w ebnu-t ; monotonous, strongly asymmetrical, proximal slopes steeper docone and septal element not detected. than distal ones, with wide interspaces; weak annulets Discussion.—The curved conchs with monotonous and consisting of fine striations in interspaces. strongly prominent rings are characteristic of Gotlandellites, Discussion.—This species is represented by an external which has been reported only from the late Llandovery to mold of afragmentary specimen. The shape of the rings is early Wenlock (Early Silurian) of Baltica, Avalonia and Lau- similar to that of Tractabilis arcticus Ljashenko (1969, pi.1, rentia (Larsson, 1979). Among the known species of the figs.1-3) from the Middle Devonian of Novaya Zemlya, but genus, Gotlandellites fukujiensis sp. nov. mostcloselyresem- accurate comparison is impossible owing to limited mor- bles G. areolatus Larsson (1979, figs.66 Ä-F), from the early phological data for the Fukuji specimen. In addition to this Wenlock of Gotland, specially in regard to proximal conch specimen, a small straight conch (2.1 mm in length, Figure1- morphology. However, the present new species has a 10a), that has asymmetrical rings and weak longitudinal lirae, larger conch (7.4mm vs. maximum observed length 4.7mm) was also examined. There is a possibility that the smaller and a lower density of rings on the distal conch (2-3vs. 6-7 specimen represents the proximal portion of the present per corresponding conch diameter). Gotlandellites visbyen- Tractabilis? sp. sis Larsson (1979, figs.67 A-F) has asmall conch, atriangu- Material and occurrence.—UMUT PW 27453 and another lar profile of the rings and well-developed annules. specimen, UMUT PW 27454, questionably assigned to this Material and occurrence—Holotype, UMUT PW 27489; species, from Locality FH-5, in the Fukuji Formation. paratypes, UMUT PW 27462,27463,27473,27508,27517, 27522,27526,27528,27530. In addition, 76 other speci- Family Gotlandellitidae Larsson, 1979 mens (UMUT PW 27455-27461,27464-27472,27374- Genus Gotlandellites Larsson, 1979 27488, 27490-27516, 27518-27521, 27523-27525, 27527, 27529,27531-27539) were also examined. The locality for Type species.—Gotlandellites visbyensis Larsson, 1979. the specimens is as follows: FH-4 (UMUT PW 27455- 27505), and FH-5 (27506-27539), both in the Fukuji Forma- Gotlandellites fukujiensis sp. nov. tion. Figures1-5—9, 10b, 11—15 locEaltiytym,olFuokguyj.i.—The specific name is derived from the type Diagnosis.—Species of large-sized Gotlandellites with approximate 5° angle of conch expansion rings with Acknowledgments ; rounded crests, their density relatively lowfor genus, 2-3per corresponding conch diameter; annulets absent or rarely I thank E.L.Yochelson for suggestions on improving this present in interspaces. paper. T. Kamiya helped collect the present tentaculitids Description.—Large-sized for genus, curved conchs with from the Fukuji area. Thanks are also due to A. Kaneko circular cross sections, largest specimen (holotype) attains and E.Sato for allowing me access to the Ofunato City 7.4mm in distance between ends of conch, 0.9mm in Museum's collections. 1GPUp0a-MWbrS,aUNt21FT0y71ip3-4ge1P,6u,53rW.3,eUbG211M.o7:3Ut5l=O2T1a2CanX,,dP1Meb4Wl,X,lG12i-210,t7S,4e35Ns=1a310,0f6X:u,b5,k.p0uaxj,xr1i3aT0e1.ten,5nystpi8:aes4pc,:,ausprplU1a.ai0Mrttaaney.UtospTyves.p,pTeP.r5,U,aWcM:1UtaUap2Mba:7TiUr5lOaTi2PtsC8yW,P?pMeWs2X,Gp71.-240U,7S6,M452N12,U0:262T,Ux:,1MPh4x1oU.1bWl0To:,t2O1yP79-p4C1We:07,M,3p2,Ua17G2r4M,-ax5tUSs13yiN0T,pl,0ei5PX,c61,oWUn0:e,xM2pr1Ua73u,0r4Tbaa82bt9e:Py:,rpUWeOcX,MaC12sU0U7tM,5sTM,01GU83P1,,1TW,S1Nxi4P2n10:t70W4e4,,pr5na214ar7x0l,a5bt31m,yx7:op1,3lep0da,a.,xr:1Ua10tO3M5,y-C-Up17ge5MT,,,: longitudinal sections, 13,15, negative prints. 282 Shuji Niko References Coniconcha). Doklady Akademii Nauk SSSR, vol.117, p.1049-1052. (in Russian) Fisher, D.W., 1962: Small conoidal shells of uncertain affin- Ljashenko, G.P., 1969: Novyy paleozoyiskie konnikonkhi ities. In, Moore, R.C. ed., Treatise on Invertebrate Arktiki (New Paleozoic coniconchs from the Arctic). Paleontology, Part W, Miscellanea, p. W98-W143. Trudy Vsesoiuznogo Nauchno-lssledovatelskogo Geological Society of America, University of Kansas Geologo-Razvedochnogo Neftianogo Instituta, vol.93, Press, Lawrence, Kansas. p.102-108, pis.1-3. (in Russian) Hall,GJe.,ol1o8g7i6ca:lIllSuusrtrvaetyionsofof DtehevoniStaantefossoifls:NPetweropYoodrak,. MinatOon, tMh.e, vToalkceadnai,c rH.o,ckHsasinhitmhoetJoa,pTa.neasnedPKaaltaoe,ozMo.i,c.19519st: Palaeontology, V, PanII, p.1-52. (not seen) report: Gotlandian and Devonian. Journal of the Hall, J., 1879: Containing descriptions of the Gastropoda, Geological Society of Japan, vol.65, p.71-79. (in Pteropoda and Cephalopoda of the Upper Helderberg, Japanese with English abstract) Hamilton, Portage and Chemung Groups. Geological Niko, S., 1996: Pseudorthoceratid cephalopods from the Surveyofthe State ofNew York, Palaeontology, V, Part Early Devonian Fukuji Formation of Gifu Prefecture, II, p.1-492, pis.1-113. Central Japan. Transactions and Proceedings of the Kato, M., 1979 2d3) Palaeontology of Chapter 2d Middle Palaeontological Society of Japan, New Series, no.181, : Devonian. In, Minato, M., Hunahashi, M.,Watanabe,J. p.347-360. and Kato, M. eds., Variscan Geohistory of Northern Schlotheim, E.F. von, 1820: Die Petrefactenkundeaufihrem Japan: The Abean Orogeny, p.67-68. Tokai Univer- jetzigen Standpunkte durch die Beschreibung seiner sity Press, Tokyo. Sammlung versteinerter und fossiler Überreste des Larsson, K, 1979: Silurian tentaculitids from Gotland and Thier- und Pflanzenreiches der Vorwelt erläutert. 437 Scania. Fossils and Strata, no.11, p.1-180. p., 15pis., Gotha. Ljashenko, G.P., 1955: Novye dannye o sistematike tenta- Walcott, CD., 1886: Second contribution to the studies on kulitov, novakiyi i stiliolii (New data on the systematics the Cambrian faunas of North America. United States of tentaculitids, nowakids and styliolinids). Biulleten Geological Survey, Bulletin 30, p.1-225, pis.1-33. Moskovskogo Obshchestva Ispytatelei Prirody, Otdel Yoder, R.L and Erdtmann, B.D., 1975 : Tentaculites Geologicheskii, Novaia Seriia, vol.30, p.94-95, (in attenuatus Hall and 7. bellulus Hall : a redescription Russian) and interpretation ofthesespeciesasdimorphs. Jour- Ljashenko, G.P., 1957: Novye klass iskopaemykh mollyus- nal of Paleontology, vol.49, p.374-386, pi.7. kov Coniconchia (New class of the fossil molluscus FukujiME, Higuchi-zawaflPiR, Nakazato ^M, Ofunatoy^Hôig