Discovery of Seirocrinus (an Early Jurassic crinoid) from the Kuruma Group, Toyama
Prefecture, central Japan
journal or
publication title
Bulletin of the Toyama Science Museum
number 17
page range 91‑94
year 1994‑03‑25
URL http://repo.tsm.toyama.toyama.jp/?action=repos itory̲uri&item̲id=642
富山市科学文化センター研究報告第17号，pp､91‑94(199雑
DiscoveryofSeか0c】･加 （anEarlyJurassiccrinoid)fromtheKurumaGroun ToyamaPrefecture，CentralJapan
MichiharuGoto
ToyamaScienceMuseum
中部日本，富山県の来馬層群からSeirocrinus（ジュラ紀前期のウミユリ類）の発見
後 藤 道 治 富山市科学文化センター
Introduction
lnJulyl983theauthorcollectedaninterestlngcrinoidfromtheLowerJurassicKuruma GroupdistributedintheeasternpartofToyamaPrefecture,north‑centralJapanJurassic crinoidsweresouncommoninJapanthattheauthorsentthisspecimerltoDr､TatsuoOjiof theUniversityofTokyoforidentification，Asaresultitbecamecleal‑thatthisspeclmenls assignedtoaspeclesofSgか γ加況sGisl6n，1924
1nSeptemberl993，twoamateurcollecters；Mr・TakashiNakahashiandMr・Teruo Mizukami，foundadditionalspecimensofS γ γ""satanotherlocality，
AllthespeclmensarekeptinToyamaScienceMuseum．
Geologicalsetting
KurumaGrouplsathickseriesofclasticsedimentsconsistingofsandstoneand mudstonetogetherwithsomelayersofconglomerateandtuff，Thetotalthicknessexceeds 6,000m,andthisgroupisdivided,inascendingorder,intoJogodani,Kitamatadani,Negoya Teradani,Shinatani,Otakidani,MizukamidaniFormations(Kobayashietal,1957;Goto,1983
etc.)．
AccordingtoSato（1955)，latePliensbachianageisconfirmedbytheoccurrenceof Aが"んfssp・andCa"α"ααsp､fromtheTeradaniFormation,andlatestToarcianageby Gm加刀 mssp,fromtheOtakidaniFormatlon、
Brackishandmarinebivalvesandfossilsoflandplantsal‑ealsoknownatvarlous horizons．
0 urrenceandCharacteristicsofthespecimens
ThespeclmenshowninFi9.2a‑cwasobtainedfrommuddysandstoneoftheTeradarli Formationexposedattherightbankofthemalnstl‑eamoftheDairariver(Fig.1−A)．This
＊ContributionfromtheTovamaScienceMuseum,No.152
Michihal‑uGoto
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Fig．1Locatlonmapofthespeclmens
A：Sc"〔･ γmssp,fromtheTeradaniFormat1onattherightbankofthemaln
streamoftheDairal‑Iver
B:Sg"cγ和"ssp、fromtheNegoyaFormatlonattheKitadaniintheupperreaches
（)ftheDairarlve1‐
formationisintercalatedwiththinseamsofcoalandisassociatedwithseveral
Iormatlonls1ntercalatedw1ththlnseamsotcoalandlsassociatedwithseveralpiecesof
petrifiedwoodatthislocality，SomespeciesofammonoidssuchasAγ " mssp.§
A柳α"ん ssp・andQz" αγ sp・occuredfromthislocality・
Thesespecimenshavecharacteristicarticulum(facet)composedoffivelobeddivisions (petals)eachofwhichconslstsofagrooveofflool‑ofrosseteshapesurroundedbycrenulae (petalodium)．AndepifacetischaracterizedbythecreasesThebothspeclmenswere safelyassignedtoS うりcγ伽"ssp、becauseofthesecharacteristicfeaturesofcolumnalin additiontothealtematmgslzeofcolumnals・Anotherspecimen（Fig2d,e）wasobtained frommuddysandstoneoftheNegoyaFormatlonattheKitadani,intheupperreachesofthe
Dairarlver(Fig.1−B）
ThegenusS"γ 邦況slswellknownfromtheLowertoMiddleJurassicofEurope SoutheastAsiaandNorthAmerica(Alaska)(Rasmussen,1978).andthisisthefirstrecordof thisgenusfromJapan．
ｎ印﹀
D〕Ij!q／SeiI･ocrinus(E"ﾉ11'ノ/"wW(cﾉ伽ﾉ/")伽"ﾉ〃ﾉ(,K"ﾉ･"ﾉ"αGγ()ﾉゆ,nVαﾉ"αPノゼルCf"ﾉ℃,α"ﾉﾉ〃ルゆ
Acknowledgements
AuthorthanksDr､TatsuoOiiforcriticall‑eadingofthefirstdraftandgivingvaluable suggestionandmformation・AndMr,TakashiNakahashiandMr・Tel‑uoMizukamLmem‐
bersoftheTovamaAmateurFossilResearchSociety,fortheirkindsupplyofthespeclmens forthisrepol‑t．
References
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Jage1‑,M. 1985;DieCrinoidenausdemPliensbachium(mittlererLias)vonRottorfamKlei undEmDelde(Sud‑Niedersachsen)．Beγ､〃α""力赦G ､Htz""0" 128,71‑151．
Kobayashi，T,，Konishi，K,，Sato，T,，Hayami，I、andTokuyama，A,，1957ｹOntheLower JurassicKurumaGroupノリz".Ggo/,SOC,ノヒZPα",63,182‑194.(inJapanesewithEnglish abstract）
Moore，RCandTeichert，C（eds)，1978；Treatiseonlnvel‑tebratePaleontology，partT・
Echinodermata2(1)．刀zeG /(〕gj /S i 1㎡A"泥γi 〃 mgU"jzﾉ"s心qfKα"s BO"〃gγ，CO/0 JO L ()γg" ，Kα"s ．
Rasmussen，H、W,，1978；Articulata・T863‑T866，InMoore，RC・andTeichertC（eds)，
TreatiseonlnvertebratePaleontology，partT，Echinodermata2(3)．刀肥G /昭imj SOa鋤'Q／A"22γ/ α72〃がgU7" 滝加Q／K""s ，BO"〃〃CO/O7zz α" L 〔1ﾉw2 、 Ktz"sas・
Sato,T､,1955;LesammonltesrecueillisdanslegroupedeKuruma,nordduJaponcentral T> 2s.Pγoc.Rz血 S ノ α",〃S・ 20,111‑118,pll8．
&鐸
b
C
MichihaI･uGoto
識蕊藤織
e
94
a
C
l〔)calitそ Fi酉.2
Scﾉﾉ･()(､岬〃耐sp．fr()mthel唾
（a‑c）andB（｡.e）
a：ScattGl−edcolumnalsi犀 sandstone
b：AI･ticulaI−faceofcolum運 c：Extemalcasts（)fc()lum
mud〔h
c：Extemalcasts〔)fc()lumnalscu資 lonHitudinaⅡv
d:Columnalwithintern〔)dals(I･ubl〕el‐
mould）
e：Articulal‑facetofacolumn scale:a．。；lcmb，c，e；0.5cm
