Bulletin of the Geological Survey of Japan，vo1．49（12），p．621－631，1998

On some躍ec童es of Sh醜膿擁eεms（Ammonoi磁ea）from塩e Cre晦eeo鵬o登翌ok：ka畳磁o，No臆hぬ：pan

（Studies of the Cretaceous ammonites from Ho：kkaido and Sakhalin－LXXXIV）

Tatsuro MATsuMoTo＊and Seiichi TosHIMITsu＊＊

Tatsuro MATsuMoTo and Seiichi TosHIMITsu（1998）On some species of Sh召脚σo醐ε（Ammonoidea） from the Cretaceous of Hokkaido，North Japan（Stu（iies of the Cretaceous ammonites from Hokkaido and Sakhalin－LXXXIV）．B％IJ．Gεol．S％γ∂．ノ吻α％，voL49（12），p．621－631，2figs．，2tables．，3plates．

Abst聡ct：Two ammonite species，Sh召ゆ6吻名8sガo名魏6α6Spath and Shαゆ6吻昭s郷ooα彫6勿％6ηs6 （Choffat）are（iescribed as the first records of their occurrences in the Cretaceous of Hokkaido． The former，which has been known as fairly widespread，is now exten（1e（i its distribution further to Hokkaido of the North Pacific region and can be called a cosmoplitan in the early Cenoman－ ian time．Sh卿6初郷窺oo翻6蜘6刀s6，which was solely recorded from Mozambique，is now recog－ nized to occur in the Lower Cenomanian of much distant Hokkaido．Further investigations wou1（1 improve our knowledge on the taxonomy and distribution of various species of Shαゆ6魏名αs so that they would become good indices of the Lower Cenomanian for the global correlation．

GSJ： Geological Museum，Geological Survey of Japan，Tsukluba，305－8567 1．亙ntroduct量on YCM：Yokosuka City．Museum，95Fukada－dai， The Cretaceous ammonite gems S肋ゆ痂6撚includes Yokosuka，238－0016 several species which occur in much separated areas Details of the geographic and stratigraphic setting of the world，whereas a few others of the same genus of the describe（1a㎜onites are described in the pre－ have been recor（1ed from a limited place．Shαゆ厩6盟s viously published papers，which are to be indicated た伽α6Matsumoto and Kawashita，1995is，so far，an in the items of〃i薦吻l and O66π耀no6in the palae－ example of the latter case，whereas S．別翻6α翻窺 ontological descriptions．To supplement them Fig－ （B6se，1928）is that of the former case，since it has ures l and2are shown in this paper． been recently foun（1from Japan in addition to its oc－ currences in Mexico，Texas and Angola（Matsumoto くじ 2．Palaeontolo9量caldescri夢tions and Kawashita，1998）．Whether the recor（1from an isolated place implies really an endemic（iistribution Class Cephalopoda or is merely due to insufficient investigation is a Order Ammonoidea problem to be clarified． Subor（ier Ammonitina In this paper we describe a（1ditional two Shαゆ6初燃 Family Acanthoceratidae Grossouv：re，1894 species from Hokkaido which may be concemed Subfamily Mantelliceratinae Hyatt，1903 with the above problem of distribution． Genus Shαゆ6」66昭s Hyatt，1903 The repositories of the specimens described below are as fo110ws，with the abbreviation of the institu－ 現）6砂66づ（gs．一／1盟zηzo％露6s彪あo乙召zノ勿s Sharpe，1855 tion at the heading： （P．31，P1．14，fig．1）by original designation of Hyatt GK： Department of Geology（so－called previ－ （1903，P．111）． ously，but now change（i to the Department R6解α娩s．一For the generic diagnosis and the gen－ of Earth and Planetary Sciences），Faculty eral accounts of Shα勿6廊6郷readers may refer to of Science，Kyushu University，Fukuoka， Wright and Kemedy（1984，p．126）and Wright（1996， 812－8581 P．154）．

＊c／o Department of Ear仕しand Planetary Sciences，Fac－ ulty of Science，Kyushu University，Fukuoka，812－8581 Japan Keywords：Cenomanian，Cretaceous，correlation，distribu－ ＊＊GeologicaI Museum，GSJ tion，Hokkaido，North Japan，Shσゆ6づ06郷，Ammonoidea

一621一 Bz61」2劾z（ゾ渉h¢GεoJo9宛αl Sz47∂εlyげノ吻）α％，1Vol．49，〈b．ヱ2，ヱ998

354，fig．1565． Shαη）6勿6名薦 oo6乞46π如躊 Benavi（ies－Caceres， Renz， 1982，p．68，p1．21，fig．1；text－fig．48．

劾loゆ6．一 The specimen from Maputoland， ○ southeastem coastal area of Mozambique，described and illustrated by Spath（1925，P．198，P1．37（by origi－ na1（iesignation in the explanation of p1．37）． 〃iα云67宛乙一GK．H8499（Plate1），collected by Toshio Shimamki and Yoshitaro Kawashita on Apri115， 1997 from a boulder of the rivulet calle（i Chennai－ zawa，a tributary of the River Monbetsu，southem central Hokkaido （Fig．1）．One of the plaster casts prepared by Toshimitsu is kept at GSJ（F l5199）and others were sent to the persons who donated the 44。N specimen to GK． も も Z）6s6吻！ズo％．一The specimen is wholly septate and about170mm in diameter．Its hreserved end is pre－ sumably at or near the last septum．The outer whorl is fairly well preserved on the right side，but its left side is distorted and shows only a part of the whorl A． ・1㊥二・ flank and the depresse（i ornament． The outer whorl expands with a low ratio，encir－ 璽）0・ cling the umbilicus of moderate width（U／D＝0．34）． θ

’薗，一 ロ The umbilical wall is low but nearly vertical to the Y ● 齢 ， plane of coiling．The whorl is subrectangular in a re－ stored cross section．It is parallel sided an（i slightly higher than broad（in the intercostal part）or nearly as high as broa（i across the costal part． M’ The outer whorl is omamented by rectiradiate simple ribs，which become distant with growth． Each rib has nearly e（luidistant three tubercles on the flank，the bullate one at the umbilical end，rather 42。N rounded or elliptical one at the mid－flank and larger 0 50km imer ventrolateral one．In addition to them there is 142。E a clavate outer ventral tubercle．Although the two ventrolateral tubercles are close to each other，they Fig．1Map of the main part of Hokkaido，indicating the are not united into a large protuberance．The inner outcropping areas of the post－Aptian Cretaceous by dots． ventrolateral tubercle has a thick dome like elevation Three areas where described．Shα勿6」66履s specimens were at its base an（l is stretched laterally ra仕しer廿lan uf）ward， collected：A：Ashibetsu（Hachigatsu－zawa），M：Mon－ forming a short hom． betsu（Chennai・zawa），Y l Yubari Mts．（River Shirakin）． Sutures are exposed here and the女e，following the general pattern of the genus． S肋η）6あ6名αs／Zoz6nαz6Spath，1925 D枷6％sズo％．一See Table1． （Plate l） Co彫勿7まso％．一This specimen shows the characters 助ηo剛脚。一 that conform well those of the holotype and other 且6催孟ho66名鷹1αあ61σ加κ窺（Sharpe）l Douvill6，1904，p． typical examples of Shα勿6魏郷刀oz6％6磁Spath．It is， 239，pl．31，fig．3． hence，identified with this species，although its mode Sh6z厚）6ズ66名鷹ノ：Zo76％6召6Spath，1925，P．198，P1．371Co1－ of preservation is somewhat incomplete．In the early 1ignon，1933，p．67，p1．6，fig．51Matsumoto，1959，p． part of the outer whorl and the preceding portion of 69，fig．281Howarth，1985，p．86，figs．15－19． the inner whorl of the holotype，ribs are mostly simple Shσゆ6初昭sgol磁h Haas，1942，p．7，fig．7． as those of the adult stage，but they are more crowded ？丁励πα121066郷吻h％α1づlo6％s6Kellum and Mintz， in earlier stages．The same feature is observable in 1962，p．276，pl．6，fig．11p1．7，figs．1，21p1．8，fig．1． the specimen from Hokkaido，although the ribs on Shαゆ8乞6θz硲sohh6ε陀7づHyatt l Collignon，1964，P．102， the younger part are sho㎜rather indis丘nctly on account p1．353，fig．1564． of poor preservation． Sh（zηう6乞6（ヲ名αs ∂oh勿）α187zsε Collignon， 1964， P． 104， P1． Z）客s6z5ss乞oη．一The holotype of this species is probably

一622一 Shごzゆ6づ66名αsノテo％z∬o々彦8づ40（皿ごz云sz6郷o渉06zgz4710shづ〃z露s％ブ

Table l Measurements of Sh卯6初燃ガo紹ηo召6Spath．

Specimen D U Uの H H圧） B B圧） B涯｛ H丑1 R

GK。H8499（E，ic） ～170 58 ．34 58 ．34 ～52 ．31 ．90 9 Holotype（E，c） 220 69 ．31 86 ．39 1．32 9 〃 （LS，ic） ～165 56 ．34 63 ．38 54 ．33 ．86 1．37 13 Howarth，fig．17 195 56 ．29 78 ．40 58 ．30 ．74 1．32 11

D＝diameter，U＝width ofumbilicus，H＝whorレheight，B＝whor1．breadth，h＝whorl．height at halfa whorl adapically from H，R＝number ofribs perhalfa whorl，～＝approximatel Eニnear the preserved end，c＝costa1，ic＝intercostal，LS＝at omearthe last septum； Howarth，fig．17＝H：owarth，1985，fig．17．Linear dimension inmm．

adult，but only an adapical part of the body chamber p．102，p1．353，：fig．1564）is certainly S．〆Zozのzoσ6be－ is preserved，as shown by the illustration of Spath cause of the configuration of its omament and the （1925，p1．37）．Originally it may have exceeded280mm umbilical ratio（0．33）．The holotype of S．∂oh勿α16多zs8 in diameter，provided that the body chamber occupied Collignon （1964，P．104，P1．354，fig． 1565），another at least half a whor1． specimen from Madagascar，is undoubtedly identified We agree with Howarth（1985，p．88）in regarding with S．刀o名召ηo磁．Its umbilical ratio estimated from Sh召ゆ6づ66郷801磁hHaas（1942，p。7，fig．7），from Angola， the figure is O．32at the intercostal diameter145mm as a synonym of S．刀076％6召6．It exceeds300mm in This specimen is similar to the holotype of S．πo彫％6召6 size and may exemplify a completely preserved adult in size and also in showing the adult type distant ribs example，as Howarth has interpreted． with strong imer ventrolateral tubercles on its pre－ Shαゆ6乞6召z偽oco乞4ε蛎α1丞Benavides－Caceres of Renz served last quater whorl．The size of its full grown （1982，p．68，pL21，fig。11text－fig．48），from Venezuela， original shell is，however，hardly estimate（i because is probably a synonym of S．刀o名2％o磁，as Howarth（1985） the position of its last septum is not clearly indicated has pointed out，although Renz7s（1982）illustration on the figure．At any rate，whether S．刀o名6％6召6was was only for the inner whorl detached from a large dimorphic or not is hardly decided from the available but incomplete outer whor1．Likewise，a large holotype material in spite of the situation that the specimens （368mm diameter）of TZ4h襯121006郷オ1αh鷹1乞lo6％s6 referable to this species are comparatively numerous Kellum and Mintz（1962，p．276，p1．6，fig．11pl．7， and that some of them are very large（368mm）．In figs．1，2），from the Indidura Formation of Coahuila， other words，no example of undoubted microconch Mexico，is very close to S．刀o耀惚，as Matsumoto has been confirmed． 6齢よ（1969，p．260）mentioned．Its compressed whorl Although several specimens from England were re－ is certainly due to secqndary deformation． ferre（1to S．プZoアのzoαεby Klenne（ly（1971，P．67，pl．25， The holotype of S．oo6毎6％如16Benavides－Caceres， fig。2），we hesitate to approve the occurrence of this 1956（p．465，p1．54，figs．5，6），from Peru，is probably species there．At least one of them（oρ．碗．，pL25，fig． referable to S．s6hh昭彪万 Hyatt，1903，0n the ground 2）has been altered to Shα膨ズ06撚sp．by Wright and of the disposition of moderately coarse ribs which Kennedy（1987，p．129，pL41，fig．21text－fig．34B）， are separated by interspaces slightly wider than the because S．πo紹郷α6at the yomg stage as small as ribs．In this respect we would agree with Wright and that specimen has more crowded and less stout ribs Kemedy（1987，p．129）to regard it as a synonym of S。 and probably more compressed whor1．That specimen s6hl鷹云副Hyatt，1903．However，the umbilical ratio rather resembles the young shell of S．soh伽孟痂，as of S．060乞4伽妬6（U／D＝0．33）is considerably lower represented by the imer whorl of the we11－preserved than that of the lectotype of S．s6hl膨ホ6万（U／D＝0．40） example figuredbyKaplan6砿（1984，p1．2，fig．1）．We estimated from the figure of Sch1盤ter（1871，p1．7，figs． are at present unable to give remarks on the affinities 4，5）．This may be due to a change with growth，for of this and certain other specimens，including S． that lectotype is very large（about350mm diameter）． ho錫go Matsumoto，Muramoto and Takahashi（1969， In fact，from the illustration of the French specimen p．261，pL 29，fig，11 pL 30，fig，エl text－figs。3，4） （Wright and Kennedy，1987，text－fig．33」）U／D is es－ from Hokkaid．o，with Shαゆε魏z偽ヵlloあ（Collignon， timated as O．33at D（ic）＝135mm（the same size as 1931，p．81，p1．8，figs．9－12）．The problem is，however， Benavides－Caceres specimen）and．0．38at D（ic）＝175 important for getting more reliable knowledge on mm at the preserved end of the still septate specimen． taxonomy and distribution of the species concerned． On the other hand S．sohlz昭彪7！J of CoIlignon（1964， We are，hence，anxious to look at relevant specimens

一623一 B％Jl6蕗7z（ゾ孟h6Gεolo9∫oαJ Sz67∂εly（ゾノ4φα％，▽101．49，ハb．ヱ2，ヱ998

of successive growth stages from oversea regions． S加吻魏郷aff．S．∂oh吻伽s¢Collignonl Matsumoto Ooo鋸解％66．一The sole example of this species from and Suekane，1987，p．3，p1．1，figs．1－3． Hokkaido is from the lower Cenomanian mudstone 刀∂♂o顔6．一A single specimen from Conducia， along the Chemai－zawa，a small branch rivulet of the northeastem coastal area of Mozambique，described River MonbetsuatHirotomi．Theareaisinthegeological and illustrated as／16α多z云hoα3名とzs l6zガoJごzz疹％盟z （Sharpe） sheet map of“Biu”（Yoshida6彪乙，1959），but the locality var．ηzoαz錫zわ勿z紹％s丞 Choffat （1903， z疹46 szφ名召） （by was not indicated in that map．The Upper Cretaceous monotypy）． of the area was subsequently sub（1ivide（1into the 〃1伽吻1．一The following two specimens from Members A1，A2to D by Akitoshi Inoma（personal Hokkaido：（1）GSJ F5151，collected by K．Tanaka communication to T．M．），as shownby Matsumoto6砿 in l951at Locality52，0n a branch rivulet in the upper （1997，fig．1）．Theunit ofmudstone alongtheChemai－ reaches of the Hachigatsu－zawa，a tributary ofthe River zawa istheMemberA1，whichhasyielded，inadditionto Ashibetsu，from thelower part ofthe Mikasa Fomlation this speciesうShごzη）6廊醐鷹窺ε％乞o召％π彫（Bδse），D6s窺066郷 （see Shimizuαごz乙，1953，route map2an（i also geological （Psεz6ゴoz6hl歪921」α）ブの）oアz乞6z6甥Yabe，Gα6配ooε劣偽』yε90ε多zs（3 sheet map of Kamiashibetsu forthelocation）．According Shigeta and Pα吻。側667オ611α肋磁花吻襯Matsumoto． to the subsequent work by Matsumoto and Okada The＆ssemb1＆ge indicates the e＆rly Cenomanian age． （1973，P．289，figs．9，10），its precise horizon is referred Outside Japan，S．プ70名ozαz6 haε been－reported to to the basal part of the middle member（marked as occur in Mozambique，Madagascar，Angola，Vene－ Mkm）oftheMikasaFomation（seeFig．20f面spaper）． zuela，Mexico，Texas and Ira耳．Thus，it is distrib－ （2）YCM、713，collected by T．Suekane at loc．S9010n uted worldwide，although the studie（i specimens in the left side of the River Shirakin［＝Hakkin－zawa respective regions are not numerous（see references by some authors］in the Yubari Mountains（Fig．11 in the synonymy list）． see Matsumoto and Suekane，1987，text．fig．1，for the locality and pL1，figs．1－3for the much reduced i1－ Sh卿6づ6獺s彫oo翻6蜘6％s6（Choffat，1903） Iustration of this specimen）．The plaster cast of this （Plates2，3） specimen is GK．H9647． Z）6so吻渉20％．一The two specimens are similarly large． Synonymy．一 At about the last septum the intercostal diameter of ／1αzn孟ho66名とzs如あo乙σzノづz御z（Sharpe）var．盟zo6α解扉（～z66％s乞s YCM．713is265mm．The body chamber of YCM．713 Choffat，1903，P．25，P1．4，fig．3a，b an（1P1．7，fig．1a，b． is incompletely preserved l namely its ventral half Shσゆ（3づ66名薦aff．S．乙6zガo乙ごzz7づz6〃z var．わz4ぢ6召Kossmat l and its last portion are destroyed away．On the as－ Shimizuαごzl．，1953，P．14（1isted only）． sumption that its body chamber was half a whor1，as

／ ’ 1㊥Loc・52

1 Mkm ／ 1 42。25730FF ＼ ＼ Mku 訟45 ＼ ￥ ＼ ＼4・ ￥ ＼45 1＼42 4 ￥ 、 ＼35 My ￥ ￥ ＼Mkl￥ ￥ 、 ！35 ＼ 覧 ￥ ￥ 0 300m 142。5’

Fig．2 Geological route map of the・Hachigatsu－zawa（part），indicating Loc．52．Chain：Boundary of lithostratigrahic mits．My：Main part of the Middle Yezo Subgroup。Mk1，Mkm，Mku：Lower，Middle and Upper Members of the Mikasa Formation．Broken line：fault．（Adapted from Matsumoto and Okada，1973，fig．9）．

一624一 Sh（zゆ召廊επzsノテo粥πo為たα♂40佛α孟sz4ηzo渉o（z多z4Tosh♂窺砿s％フ

Table2Measurements of Sh召膨魏郷彫06召解δ吻6ηs6（Choffat）and Sh召卿吻郷s6hJ襯6η’ Hyatt（1ectotype）（at the bottom）．

Specimen D U UID H H！D B B／D B／H Hlh R

GSJ F5151（E，ic） 255 85 ．33 104 ．41 ～70 ．27 ．67 1．58 11 〃 （E，c） 260 83 ．32 110 ．42 ～78 ．30 ．71 1．62 12 YCM．713（E－150。） 265 85 ．32 108 ．41 1。50 11 Holotype（E－1500） 350 100 ．29 132 ．38 96 ．28 ．73 12

S．s6hlμε∫8r∫ 348 135 ．39 123 ．35 102 ．29 ．83 1．37 13

E－1500ニat the point1500adaptically from E（preserved end）．Other symbols as forTable1．

Measurements of the holotype ofS．〃200α励∫gμ6nsεdepend on Choffat（1903，p。26，pl．4，且g． 3a，bandpL7，丘g，1a，b）；those of3。sohl惚67∫arecitedfromWrightandKemedy，1987，p．130． in other better preserved examples of Sh6z厚）6づ06名召s， the imer ventrolateral shoulder which stretches side－ the entire shell di註meter of this specimen would have ways，and（5）the clavate outer ventrolateral one． been nearly as large as420mm． The tubercles also strengthen with growth along GSJ F5151is wholly septate，but its preserved en（1 with the ribs，although some of the tubercles appear is presumably at or near the last septum．Its earlier to be blunt on accomt of weathering． part of the preserved outer whorl is again incomplete， The sutures are well exposed on the surface of but owing to the regular disposition of tubercle，the YCM．713．They are similar to those of the illustrated outline of the missing Part can be reconstructed． large specimen of S．観づ6伽伽窺（Wfight and Kemedy， Thus，the intercostal diameter near the preserved 1987，text－fig．30）． end（markedMinPlate2）isestimatedas255mm Z）珈6％s歪o銘．一See Table2． andthecostaldiameterimmediatelybehindMis Co彫勿7乞so％．一The described two specimens are best about260mm．This size is，thus，quite similar to that referable to Shごzηり6勿6矧sηzo6召％z房（1z彪ns6（Choffat，1903）， of YCM．713at the last septum． because of their very large size，rather low umbilical In both specimens the rate of whorl expansion is ratio（U／D about O．3），comparatively compressed fairly high（H／h：about1．5）and the width of umbilicus whor1（B／H about O。7），simple long ribs disposed at is about one third of the shell diameter．The specimens fairly wide intervals on t血e outer whorl and tubercles in may be secondarily compresse（1，but from the less de－ five rows，of which those on the outer flank are weaker formed part（the left side in YCM．713and the right than others but independent and dispose（1at midway side in GSJ F5151）the ratio B／H is estimated as between the mid－1ateral and imer ventrolateral ones slightly less than O．7 at the intercostal part an（i and those at the ventrolateral shoulder are strong somewhat more than O．7in the costal section．The and stretch sideways． whorl section is subrectangular．The flank is very GSJ F5151was listed as Shαゆ6吻槻s aff．Z誠6伽勉彫 weakly convex in GSJ F5151and nearly flat in var．初4初Kossmat by Shimizu6短乙（1953，p．14）， YCM．713．As the latter specimen was embedded in but it does pot fit the form described by Kossmat mudstone，its original shape may have been secon－ （1895，P．199，P1．24，figs．5，6），for the latter is smal1 darily flattened．The umbilical ed．ge is abruptly bent ＆nd has intercalated or brαnched ribs frequently． to the steep wa11，which in tum is overhanging and F6rster（1975，p．247，pl．16，fig．5）regarded Kossmat’s gently convex rather than strictly flat二 （1895）species as掘α多z云611廊6名os勿z4歪o％窺（Kossmat）． The omament of the outer whorl is characteristic． In the previous work of Matsumoto and Suekane It consists of long ribs，which have tubercles in five （1987，p．3，p1．1，figs．1－3），the specimen YCM．713 rows．The ribs are weakly prorsiradiate with a very was described under Shαゆ6吻鵤s aff．S．∂ohゆ認6ηs6 gently concave curvature on the flank of the early Collignon．This was misleading．They（1id not notice part of the outer whorl and become nearly rectiradiate the outer lateral tubercles，which are weak but shown in the later part．They are separated by much wider on the photograph．As has been mentioned already～S。 interspaces and gradually strengthen with growth． ∂oh勿ごzl6％s6 is a synonym of S．プZoz即zαz6 Spath （see The five tubercles are（1）the bullate umbilical one， also discussion below）． （2）the subromded or elliptical one of moderate in－ ．ρゑs6鋸ss加．．一S．郷oo召励名卿鷹isalliedtoS．刀o欄鷹 tensity at about the middle of flank（somewhat inside in that the two species commonly show a fairly narrow of the strict mid－flahk），（3）the weaker one on the umbilical ratio（U／D around O．3），that the ribs become outer part of flank（midway between the second and increasingly distant and strong with growth whereby the fourth ones），（4）the larger and stronger one at the inner ventrolateral tubercles stretch si（lew＝ays in

一625一 βz6116訪z（ゾオh6G60109乞αzl Sz67％yの‘ノめり磁z，▽lol．49，2Vo．12，ヱ998

a style of homs．The two species，however，can be Ando（1990）suggested that the basal part of the Mikasa distinguished l namely in S．πo紹％6磁the ribs are Formation along this route is referable to the Upper more crowded in earlier part and become separated Albianontheevidenceofa㎜o撮tewbchistenta廿vely more rapidly later．Although there may be some extent called Cαη励塵飽s aff．s励sズ吻忽Spath（Matsumoto of variation，S．ノZo名6％6α6has generally broader whorls α磁，1991）．YCM．713is withintheunit ofthe mudstone with a larger ratio of B／H and also coaser and more expose（1along the upPer course of the River Shirakin． robust ribs in comparison with S．卿ooα郷6勿％6％s6． It is associated with a species allied to肋oo6昭窺鷹（s．1．） The existence of the outer lateral tubercles at midway o吻卿Mantell and its horizon is reasonably below between the mi（1－1ateral and the imer ventrolateral the horizon of C観％初g云on乞66郷如hαh4s鰭（Matsumoto）， tubercles throughout the outer full whorl is charac－ a middle Cenomanian ammonite．Because of a folde（1 teristic of S．盟zoαz盟z擁（～z6卯zs6，although they are not stmcture what comes below the horizon of YCM．713 strong。 is not known．At any rate，the described two speci－ Wright andKemedy（1987，p．129）1isted、46翻ho66燃 mens came from somewhere in the lower part of the 乙6z渉勿1αz7伽ηz var．ηzoαzηz扉（7z6ωzs釣Choffat，1903［publi曲e（i Cenomanian． in January］as a synonym of Sh4ゆ6初解s s6hl％吻7乞 The age of the holotype of S．窺ooα卿6勾％6％s6is not Hyatt，1903［published in May or later］，though with precisely recorded．Undoubted examples of the same a query．In our opinion the two species can be distin－ species have not been reported from other regions． guished．Namely，S．解06α窺吻％6％sεkeeps to have a As Hokkaido，northem Japan，is much separated comparatively narrow umbilicus even in the late from Mozambique，the species can be expectedto occur growth stage，showing U／D about O．3in contrast to widely in other regions of the wor1（1． about O．40f S．s6h伽彪nl The ribs become more distant with growth in the former than in the latter．As a result 3． S盟m灘ma買y o≦！置es題亘ts the ribs on the large outer whorl are less numerous in S．盟zooα盟z6勾z6のzs6than in S．s6hh6（払674for instance In this paper two ammonoi（1species，Shσゆ砒6z薦 220r23in the former compared with280r29in the 〆Zoz6多z6α6Spath，1925and Shごzηり6づ66名召s〃zo6α％z扉（7z昭％s6 latter．This difference would be more pronounced on （Choffat，1903）are described on the specimens from the the adult body chamber of about half a whor1，a1－ Lower Cenomanian of Hokkaido．The former is based though completely preserved examples are not avai1－ on a recent acquisition fromthe Monbetsu area，south－ able at present。 central Hokkaido，whereas the latter（1epends on the Accordingto W士ightandKemedy（1987，p．130），there two specimens previously reported under different are some British examples of S．sohl膨診副in which names，one from the Ashibetsu area and the other an outer lateral Ulbercle apPears at dianleters of290㎜． from the Yubari Mountains of central Hokkaido． Without seeing the specimens or good illustrations， S．刀o形η6α6is known to distribute worldwide，a1－ we hesitate to give adequate remarks on this infor－ though some specimens have been reported under mation．We expect，as a possibility，thatthose British several dissimilar names which should be regar（ied specimens could be referable to Shσゆ厩6鰯h貌襯6 as synonymous with S．刀oz6％oσ6． Matsumoto and Kawashita，1995（see revised descrip－ S．別ooo：彫δ勿％％s6was previously reported solely tion of Matsumoto and Kawashita，1998，p．92，figs．3， from a locality in northem Mozambique．This paper 4）。S．庖肋磁indeed resembles S．sohl％漉万in the gives the first record of its occurrence outside that large size（D＝410mm near the apertural end of the area．There is，however，an opinion（Wright and adult holotype），fairly wide umbilicus（U／D＝0．42）， Kemedy，1987，p．127）thaガit might be included in and the coarse ribs on the outer whor1，except for the better known species，S．s6hl％吻万Hyatt，1903．At the finer flange on the apertural margin．However， present we do not agree with廿亘s view and suggest that the former has a distinctrow of outer lateral tubercles S．観襯6Matsumoto and Kawashita，1995，recently in contrast to no record of such a character for the established on a specimen from Hokkaido，is more latter in the descriptions of Sch1Uter（！871）a．nd Hyatt closely allied to，if not identical with，S．s6hlπ碗π． （1903）．At any rate，we should make the true state At any rate，further investigations on sufficient more clearly by further examination of sufficient material are required to make clear the true state． materia1． Species of Shαゆ6初燃would，thus，becomegood indices Oooκ％％66．一See material for the geographical of the Lower Cenomanian for the global correlation． locations ofthe twosp㏄im㎝sfrom Hokkaido．GSJ F5151 came from the lower part of the Mikasa Formation． Ack亙琶ow亘e哩geme醜ts：We appreciate the laborious It was in the sandy siltstone（or silty fine－grained field works of Dr．Keisaku Tanaka（former staff sandstone）atthehorizonabout130mabovethebase member of GSJ），Messrs．Tetsuro Suekane，Yoshitaro of the Mikasa Formation．P6s彫oo6燃（A6雇o％hl忽61勿 Kawashita and Toshio Shimanuki，who・collected and ノのo％加吻occurs from this and other levels（above an（1 supplied the valuable specimens of Shα勿痂6名偽for below）showing a long range through the Cenomanian． this study．Thanks are（1ue to Dr．Yasumitsu Kanie

一626一 Shαゆε乞oεzαsノケoηz五乙oたゐα疹40（7屡ζz6s％ηzo孟o（z多z4Tosh乞窺魔s％ク for providing a photograph of YCM specimen and Kennedy，W．」．（1971）Cenomanian ammonites also Dr．Yukio Yanagisawa for careful improvements from southern England．助60．1R砂．P痂ごz60窺．， of the manuscript． 8，H33，pls．1－64． Kossmat，F．（1895）Untersuchmgen Uber die sUdindische Kreideformation．B魏7．P励Oo短． Re£ere醜lces G60乙0鉱一砺9．07競差，9，97－203，Pls．15－25． Ando，H．（1990）Stratigraphy and shallow marine Matsumoto，T．（1959）Upper Cretaceous ammordtes sedimentary facies of the Mikasa Formation， of California．Part II．躍6彫．Eα6．S6ぎ．κ夕z6shz6 Middle Yezo Group（Upper Cretaceous）．力解． 0励．．S6飢D，G60乙5勉，％乙1，1－172，Pls．1－41． G601．So6．ノの6z％，96，279－295．（in Japanese Matsumoto，T．and Kawashita，Y．（1995）A new with English abstract） ammonite species of Shα勿切66郷from the Benavides－Caceres，V．E．（1956）Cretaceous system Oyubari area．メo％7．Eα6．E4％o．Sα9αU痂”。， 玉n northern Peru．βz611．ノ1ηz6飢ノ匠z6s．皿zゑπ廊差， 42，186－187，p1．5． 108，353－494，pls．31－66． Matsumoto，T．and Kawashita，Y．（1998）Two B6se，E。（1928）Cretaceous ammonites from Texas ammonite species of the genus Shαゆ6初燃 and northem Mexico．β％ll．0勉∂．7セ％αs，Bπ7． from the Cretaceous of Hokkaido．Pとzl607z差． E60％．G601．T66hηo乙，2748（for1927），143－312， R6s6απh，2，89－95． pls，1－18． Matsumoto，T．，Muramoto，T．and Takahashi，T． Choffat，P。（1903）Contributions a la connaisance （1969）Selected acanthoceratids from Hokkaido． g6010gique des Collonies portgaises（1フAfrique． κ6万z．Eα6．Soづ．，瓦yz6shz6乙秒zづ∂．．S67．1）．G601。， 1．La Cr6tacique de Conducia．Co窺解乞ss歪o％ 19，251－296，pls．25－38． 伽S6吻6606010g蜘64πPo吻即1．32P．，9pls． Matsumoto，T．，Noda，M．and Maiya，S．（1991） Collignon，M．（1931）Pa160ntologie de Madagascar， Towards an integrated ammonoid，inoceramid－ XXI．La faune du C6nomanien a fossiles pyhteux and foraminiferal biostratigraphy of the du nort de Madagascar．∠4朋．46．P鷹o鋭．，29， Cenomanian and Turonian（Cretaceous）in 43－104，pls．5－9． Hokkai（io．ノリz67．06097．To々yo，100，378－398． Collignon，M．（1933）Fossiles C6nomaniens d’Ant－ （in Japanese with English abstract） satramahavelona （Province d7Analalava， Matsumoto，T．and Okada H．（1973）Saku For－ Ma（iagascar）．／1％％．（劾乙S励．躍伽8s1嫌】㎎ mation of the Yezo geosyncline．SoJ．ノ～の孟s． 716z％αηごz万z76，3，53－79，pls．5，6． 1）砂ム G601．．幻％shκ Un吻．，2，275－309．（in Collignon，M．（1964）∠4伽伽ヵs吻soα名伽6溶吻鰯 Japanese with English abstract） 46漁磁飾催64郷窺o競6s2，ll（C6nomanien）， Matsumoto，T．and Suekane，T．（1987）Some 1－152，Pls．318－375． acanthoceratid ammonites from the Yubari Douvi116，F．（1904）Pa160ntologie，mollusques fossiles． Momtains，Hokkaido－Part1．SoJ．Rのム 動Morgan，」．de，ed．，〃i癬o銘so勧孟物麗㎝ん鷹 ∬o左osz6た召C才砂ノ匠z6s6z6％z，no。35，1－14，Pls．1－4． 3，191－380，pls．25－50． Matsumoto，T．，Yokoi，K．and Kawashita，Y． F6rster，R．（1975）Die geologische Entwicklung （1997）Further notes on the ammonoid genus von SUd－Mozambique seit der Unterkreide Pα吻側わ6吻llα．勘160窺．1～6s卿6h，1，188－199． und die ammoniten－Fama von Unterkreide Renz，0．（1982）71h6α飽660鷹翻窺o勉孟6sげ und Cenoman．060乙力h地，B12，3－324，pls．1－17． 距％6z麗61α．Maraven，Caracas，132p．，40pls． Haas，0．（1942）Some Upper Cretaceous ammon－ Sch1Uter，C．（1871）Die Cephalopoden der oberen ites from Angola。∠4耀7．〃傭．・鋤∂菰，1182，1－24． deutschen Krei（1e．Pα」ごzεo多z60g名αゆh乞6α，21，1－24， Howarth，M．K．（1985）Cenomanian and Turonian pls．1－8． ammonites from the Novo Redondo area， Sharpe，D．（1855）Description of the fossil remains Angola．β鋸ll．β7魔〃初s．餉ム撚劫（弛o乙s8z， of Mollusca found in the Chalk of England． 39，73－105． Part2，Cephalopo（ia．勘舵o多zオ09吻）h勿σl So6勿顔， Hyatt，A．（1903）Pseu（10ceratites of the Cretaceous． London，（1854），27－36，pls．11－16． 〃’o勉og7．U．S．G601．S躍∂．，44，1－351，pls．1－47． Shimizu，S．，Tanaka，K．and Imai，1．（1953）盈一 ：Kaplan，U．，Keller，S．and Wiedmam，J．（1984） ／）乙ごz％6z渉o勿ソ7セ％≠6ゾ孟h6G60109乞66zlノ砿64）q〆ノ砿）6zη． Ammoniten－und Inoceramen－Gliedermg des ヱr50000，Kα％zゑ硲hあ6ゑsπ，Geo1．Surv．Japan， nor（ideutschen Cenoman． S6h7舜7626h6 467 78p．（in Japanese）十21p．（r6sum6in English）． Ezゴ”客ss6％s6hl乞6hのz κoηzηz乞ss乞o多z， 7， 307－347， Spath，L．F．（1925）OnUpperAlbianA㎜onoidea Pls．1－8． from Portuguese East Africa，witぬan appendix Kellum，L B．and Mintz，L．W．（1962）Cenomanian on UpPer Cretaceous ammonites from ammonites from the Sierra de Tlahualilo， Maputoland．！生槻．丁瓢襯s∂．ハ4％s．，11，179－200， Coahuila，Mexico．Coπ7．〃1％s．勘♂60砿U％初． pls．28－37． κ乞6h．，13，267－287，pls．1－8． Wright，C．W．（1996）SuborderA㎜onitinaHyatt，

一627一 Bz6116あアz（ゾ云hθ（3！60109ガ6αl Sz67z2砂（～プノψごz珍 Viol．49，ハ入o．ヱ21ヱ998

1889．動Wright，C．W．with CalIomon，J．H． Ammonoi（1ea of the Lower Chalk．Part2． and Howarth，M．K．丁翅伽o銘動∂6吻6鰯6 」40％09先jp痂6傭o野Soo，partofl39for1985， 」％160螂ology，磁πL，〃’oll麗S6α4．Z～6薦畷∂0乙 127－218，pls．41－55． 4r C㎎如060郷∠4郷〃zoηo歪46α，GeoL Soc．Amer．， Yoshida，T。，Matsuno，K．，Satoh，H．and Yamaguchi， Boulder and University of Kansas，Lawrence， S．（1959）Z助り彪％ζz孟o老y 7セκ！（ゾ差h6 G6010g勿α1 9－206。 躍の（ゾノ吻）朋．ヱ」5000αB伽Geo1．Surv．Japan， Wright，C．W．and：Kemedy，W．J．（1984）The 47p。（in Japanese）十7p．（abstract in English）． Ammonoidea of the Lower Chalk，Part1． ハ40％09飢P痂εo吻9飢Soα，partof137for1983， Received August25，1998 1－126，pls．1－40． Accepted October16，1998 Wright，C．W．and Kemedy，W．J．（1987）The

北海道白亜系産アンモナイトSharpeicerasの若干種について （北海道・サハリン産白亜紀アンモナイトの研究一84）

松本達郎・利光誠一

要 旨

アンモナイトのS勉ゆ就θzαsガ07伽oαεSpathとS勉ゆ厩εz偽別oo翻6匂％％sθ（Choffat〉が北海道の 白亜系からも産出することを，はじめて記載した．前者は従来かなり広い分布を示すことが知られてい たが，北太平洋地域の北海道にも認められ，セノマニアン初期におけるコスモポリタンと言うことがで きる．後者はモザンビクだけから記録されていたが，今回甚だ遠隔の北海道のセノマニアン下部から産 出が認められた．今後の研究により，この属の諸種の分類と分布がもっと明確になり，セノマニアン下 部の有効な示準種として世界各地の対比にいっそう役立つようになるであろう．

一628一 8ノ～π7伽1‘1〔～7・硲1）’o〃2五10々々αi40‘〃認s〃ア㍑認o召アz4Toshi規i！szO

A

c

D

照

鐵畷．

鑛、

畷難難鐸

Plate1 Shαηりcガ（｝（～ηzs．〃（〃で躍cαピSpath． GK．H8499，collected by T。Shimalluki and Y．Kawashita from the Chemai－zawa，Mollbetsu area． A：rightside；B：venter；C：1atepartofventer；D：leftside．Scalebar二3cm． （photo by S．T．without whitenillg）

629 B～4セだηげ！12εG8010g乞ごα！S2〃∂のンqん勉／）‘脚，レbl．49，ノ〉o．12，1998

納弘

欝、・ 、難

A

Plate2 Sh召厚）6廊6ηzs n’zo66〃ηわi（1π6ηs召（Choffat）． GSJ F5151，collected by K．Tanaka from loc．520f Hach1gatsu－zawa，Kamiashibetsu area．A： natural frontal section；B：right side．M：positioll of measuremellt of diameter．Scale bar＝3cm． （photo by S．T．without whitening）

一630 Shαゆ顔－6耀s∫〉η〃z」厚ohた厩40‘〃1観s多〃刀o！oαn4Toslz乞解πsz∂

蘇 聾

馨 、難蓬

辮5雛、 灘繍・

，鞭難饗鐘灘

難灘 馨織薦

獅拓’ 灘難、 垂．舅難 雛 鵠 1騰綴萎 麗灘鞭 嫌 ．鰯縫態 撚 鐵 撚霧、 、繊 z蟹 睡蕪． 麟． 灘駿，，騰騒

．墾 澱簸3 纂 簿

霧、 毎蔀 籔匿 、鱗 灘 嚢 繊購 灘蟹 雛 垂、

霧、，鰍渥． 醗騒欝 麟籔 購 羅 驚廃霧 萎、 難、描 欝繍，響、鰯、轟

汚、霧r雍

萎議麟懸騰．懸購，， 鶴艶’ 轟灘 難鞭講 難難彗曽詫灘．騨

難・懸． 、綴雛 灘 が 「、，． 蟹叢…翻鰭

・、壁ll

1）late3 Shごzノプ）6i66箔とzsη70αz1麗わ！（1κ8㌶s6（Choffat）． YCM．713，collected by T．Suekane from loc．S9010n the left bank of the River Shirakin，Oyubari area．Left side．Scale bar二3cm． （photo by courtesy of Y．Kanie）

一631一