Table Of Content;
CHELODES AND CLOSELY RELATED
POLYPLACOPHORA (MOLLUSCA) FROM THE
SILURIAN OF GOTLAND, SWEDEN
by LESLEY CHERNS
Abstract.SilicifiedassemblagesofSilurianchitons(polyplacophorans)fromGotland,Swedenaredominated
quantitativelybyanew,Wenlockspeciesofthelong-ranginggenusChelodes',C.actinissp.nov.isdescribed
herein.Headsclerites,previouslyunknownforChelodes,arerecognizedforthisspecies,butnotailsclerites
are identified. Other Gotland Chelodes species, including the type species C. bergmani, are revised.
Spicuchelodespilatis, acloselyrelatednewgenusandspecies,isalsodescribed. Silicificationtookplaceby
delayedreplacement,beforesignificantcompaction.GrowthpatternsofscleritesinthelargepopulationofC.
actinisdemonstrateallometry,andareusedasthebasisforcomparisonwiththosepatternsdeterminedfrom
growthlinesonindividual scleritesofC.gotlandicusand C. cf. bergmani. Variationofindividual sclerites
interpretedasbelongingtoasingleanimalofC.actinisiscomparedwiththatinRecentChiton.Sculptingof
theventralsurfaceinthickenedscleritesofthesepaleoloricatechitonsprovidesevidenceforthemusculature
thisisincontrasttoliving,neoloricatechitonswhichrarelyshowmuscleattachmentfeaturesbuthavesutural
platestoprovidephysicalarticulationofsclerites.
Early Palaeozoic polyplacophorans (chitons) have a sparse geological record, being confined
mostlyto limited occurrences ofisolated plates. Thelong-ranging genus ChelodesDavidson and
King, 1874 (Ordovician to Devonian) is unusual in having fairly large, massive plates, and a
relativelywidespreadgeographicaloccurrence.ItwasfirstdescribedasC.bergmaniDavidsonand
King, 1874 from the Silurian ofGotland, from where a second species was also described by
Lindstrom (1884). This Gotland material, from collections in the Naturhistoriska Riksmuseet,
Stockholm(RM),wasre-examinedandrevisedbyBergenhayn(1943, 1955),whoestablishedtwo
additionalspeciesofChelodesandalsoerectedthenewgenusGotlandochiton.Now,newcollections
of silicified chitons from Gotland have been recovered from acid-isolate residues of extensive
silicified limestone samples collected by Dr Lennart Jeppsson (Lund University, Sweden). The
chitons form a relatively minor part ofthe total skeletal material from these samples, but are
neverthelessnumerousbycomparisonwithmostotherPalaeozoicchitonassemblages. Moreover,
theirpreservationisverygood,andincludesawiderangeofscleritesizes.Quantitativelydominant
amongtheseassemblagesisanewspeciesofChelodes.ThispaperdescribesalltheGotlandspecies
ofChelodes and closely related forms, based on the new material and on the existing museum
(RM) collections; the remainder ofthe Gotland chitons, mostly from the new collections, will
be described in another paper. All the new collections are deposited in the Naturhistoriska
Riksmuseet, Stockholm(RM).
TheSilurian(LlandoverytoLudlow)successiononGotlandcomprisesstableplatformcarbonate
sequencesoflimestonesandmarls,withminorsiliciclasticunits,strikingnorth-east-south-westand
dippingverygently(1-2°)towardsthesouth-east.Thebedsarerichlyfossiliferous,withmostlevel-
bottom shelly assemblages dominated by brachiopods, and organic reefs that have coral-
stromatoporoid-calcareousalgalassemblages. Silicifiedhorizonsoccuratmanylevels, commonly
associatedwithbentonites(LaufeldandJeppsson 1976). Jeppssoncollected samplesfrom several
hundredlocalitiesthroughthesuccession,withmultiplesamplesfromthemoreproductivelocalities
IPalaeontology,Vol.41,Part3,1998,pp.545-573,7pis] ©ThePalaeontologicalAssociation
546 PALAEONTOLOGY,VOLUME41
? 77
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\ '
eeJtLi sj
0K\ hm\
1/0°^
2I
SundreFormation
HamraFormation
BurgsvikFormation
EkeFormation
HemseGroup
KlintebergFormation
MuldeFormation
HallaFormation
SliteGroup
ToftaFormation
HogklintFormation
L+UVisbyformations
text-fig. 1. Forcaptionseeopposite.
A
CHERNS: SILURIANPOLYPLACOPHOR 547
tWteexrt=m-ifwniiogdl.tohg2;y. iSAncLhdeo=mrasatapliicc(laedlfit)al,gernvgeantmthr;oaflHi(rn=itgehhrtem)iegdahinta;dtepAossc=tleerraiiptoiercao(lfmiaCdnhdgellele)o;dveJise=wssh.jougLwail=ngalnesgntlgaetn;hd;aarMldL=mae=natsmeuerrodleiamatenenrtallsengaatnnhdd;
pi=posterolateralportionsoflateralmargins;cf=centralshellfield;If=lateralshellfield.
(‘ProjectonSilicifiedFossilsfromGotland’). Chitonsoccurinsamplesfromonlyfourlocalities:
threefromtheWenlock, at Mollbos (Mollbos-1, Grid Reference Riketsnat RN 637645 165970;
L1i;lRjeNdah6l381098240),16K7l2i9n5t;ebFysry(kKlmiannte1b9y8s9)1,;RanNd6o3n6e51f5ro1m64t6h8e5L;uLdaluofwe,ldat1A97n4g)vaarnddsK(rAankgfvoatrd(sK-r4a,kfRotN-
631953 164607).These,andallotherlocalitiesonGotlandthathaveyieldedchitons,areshownin
Text-figure1.ChelodesinmuseumcollectionscomefromKlinteberget,Gannvik,BursvikandRone
(butprobablynotAtlingbo-seediscussionofC.gotlandicus).
Terminologyandmeasurements (Text-fig. 2). Standard measurementswere taken with the dorsal
medianlinemountedhorizontally; length,medianlength, andwidthweremeasuredindorsal or
lateralview,heightintransverseprofile,andapicallengthalongthemedianlength.Theplatesof
the chiton shell are referred to here as sclerites rather thanvalves, since the latter term is more
appropriateto organismswithpairedshellsthatenclosesoftparts. Thetotalandmedianlengths
differ by the amount of embayment of the anterior margin; the term anterior sinus is not
appropriate in these chitons, which lack the sutural laminae ofmodern forms. Apical andjugal
angles were measured in dorsal and posterior views, respectively. Where the posterior apex is
roundedthroughabrasion,theapicalangleistakenastheanglebetweentheposterolateralmargins.
Changingshapeofthescleritesthroughtheirprogressiveelongationresultsinconvexposterolateral
margins; forlarger shells, estimates ofapical angles in worn specimens are typically lower than
measurementsobtainedfrombetterpreservedspecimens.Thejugumisthedorsalmedianridgeor
roundedarea,andthejugalangleisthatformedbythesideslopeareas(HoareandSmith 1984).
(
text-fig. 1.GeologicalmapofGotlandshowingstratigraphicalunitsandlocalitiesyieldingchitons with
italicizednames)frombothpreviousmuseum(RM)andnewsilicifiedcollections.
;
548 PALAEONTOLOGY,VOLUME41
The term anterolateral margin is used here to describe the posteriorly directed corners and
continuationoftheanteriormarginaroundtothepointwheretheanteriorgrowthlinescrosson
totheventralsurface.Theposterolateralmargincontinuesfromthatpointtotheposteriorapex;
alongthismargin,growthlinescrossalongtheentirelength.Shellfieldsaretriangularareasofthe
dceonrtsraallsfuirefladcfeldaenlkiemditbeydlbayteraalrafdiieallds,riadngedotrhefoflodrfmrerommaadyjaicnecnltudaereaasm;edifiaplre,sjeungt,althfieerled.isusuallya
Inthesystematicdescriptionsthatfollow,themeasurementsandratiosgivenaremeans,unless
statedotherwise.
SYSTEMATIC PALAEONTOLOGY
Classpolyplacophorade Blainville, 1816
SubclasspaleoloricataBergenhayn, 1955
OrderchelodinaBergenhayn, 1943
FamilymattheviidaeWalcott, 1886
GenuschelodesDavidsonandKing, 1874
Type species. Chelodes bergmani Davidson and King, 1874, p. 167, pi. 18, figs 14, 14a-d, by original
designation,fromtheSilurian(Wenlock)ofGotland.
Reviseddiagnosis(emendedfromRunnegaretal. 1979,p. 1388).Wedge-shapedtocordate,arched
intermediate sclerites with posterior apex; becoming elongate, massive. Ventral apical area
flattened, up to more than halfthe length, anterior rim elevated slightly above smooth ventral
surface. Growth lines across dorsal surface and ventral apical area, sometimes with ridged and
granulatedorsalornament. Shellfieldslackingtowell-defined.
Remarks. Runnegaretal.(1979)incorporatedthemolluscanclassMatthevaYochelson, 1966into
the Polyplacophora, and the family Chelodidae Bergenhayn, 1943, including Chelodes, into the
family MattheviidaeWalcott, 1886. Alsoincludedin Mattheviidaewere the genera Calceochiton
Flower,1968,HemithecellaUlrichandBridge,1941andMattheviaWalcott,1885.SmithandHoare
(1987,p.7)retainedthefamilyChelodidaetoincludeotherpaleoloricatetaxanotassignedtomore
narrowly defined familiesin the orderChelodina, e.g. EochelodesMarek, 1962. Stinchcomb and
Darrough(1995)questionedthepolyplacophoranaffinitiesofCambrian-Ordovicianhemithecellids
fromtheOzarkareaoftheUSAanderectedanewmolluscanorder, Hemithecellitina theyalso
suggested that some elongate species ofChelodes might be included therein. Matthevi;ids differ
fromgotlandochitonidsinhavingscleriteslongerthanwide(Bergenhayn 1943, 1955;Smith 1960;
Smith and Toomey 1964; Runnegaretal. 1979). Furtherconsiderationoftaxonomyamongthe
EXPLANATIONOFPLATE 1
Figs 1-2. ChelodesbergmaniDavidsonandKing, 1874;KlintebergFormation,upperWenlock(Homerian),
lSaitleurraila,n;poKsltienrtieobreragnedt,aGntoetrliaonrd.vi1e,wshorleostpyepcet,ivRelMy;Mxo36.022,7;RiMnteMrom6e0di2a8t;esicnlteerritmee;diaa-te,edsocrlesrailt,e;vean-tcr,ald,orrsiaglh,t
FigvK.elni3tn.rtaeClbhyaesnl-1do,daeGnsotetcrfl.iaonrbdev;rigeimwnastnerirem;sepdReicMattievMeslcoyl;e1r6ix0te.3;0;5ad6-,;e,dHedtaoalrilslaaol,fFodvroemrnatsratalilo,snur,rifgauhcptep,leasrtheroWawle,innlpgooscgtrkearni(uoHlroamarenrodirananna)tme,erniStoi;rluvrxiiea1wn5s;.
respectively; x3.
Fig. 4. Chelodesgotlandicus Lindstrom, 1884; RM Mo6029; Hamra Formation, upper Ludlow, Silurian;
Gannvik,Grotlingbo,Gotland;intermediatesclerite;detailofdorsalsurfaceshowinggranularornament
x15.
PLATE
1
CHERNS, Chelodes
550 PALAEONTOLOGY,VOLUME41
paleoloricates will await description of the remainder of the Gotland chitons. As currently
understood,Chelodesisabroadlydefinedgenusofwidemorphologicalvariabilityandwithalong
stratigraphicalrange(lowerOrdovician-upperSilurian/LowerDevonian)andwidegeographical
distribution(Sweden,Britain,CzechRepublic,NorthAmerica,Australia).Runnegaretal's(1979)
emended diagnosis forthe genusincluded a deep anteriorembayment on body sclerites, and an
apicallengthofone-thirdtoone-halfofthescleritelength.However,thetypespeciesofChelodes,
C. bergmaniDavidsonandKing, 1874,ischaracterizedbyastraightanteriormargin.TheNorth
AmericanSilurianspecies C. raaschi(Wenlock-Ludlow; Kluessendorf1987)hasanapicallength
greaterthanhalftheshelllength.
ChelodesbergmaniDavidsonandKing, 1874
Plate 1,figures 1-2
v*1874 ChelodesbergmaniDavidsonandKing,p. 167,pi. 18,figs 14, 14a-d.
v.1884 ChelodesbergmaniDavidsonandKing;Lindstrom,p.51,pi.2,figs 1-8, 16-17.
1885 ChelodesbergmaniDavidsonandKing;Fischer,p.878.
1897 ChelodesbergmaniDavidsonandKing;Etheridge,p.68.
vp.1943 Chelodesbergmanni[sic]DavidsonandKing;Bergenhayn,p.298.
vp.1955 Chelodesbergmanni[sic]DavidsonandKing;Bergenhayn,p. 12,pi. 1,figs3a-b;pi.2,fig.2
[reconstruction].
1960 ChelodesbergmaniDavidsonandKing;Smith,p. 149,fig. 34, 5a[reconstruction],5b-c[cop.
Bergenhayn 1955],
1975 ChelodesbergmaniDavidsonandKing; Van Belle,p. 123, pi. 1,fig. la-b [cop. Bergenhayn
1955],
1977 Chelodes bergmani Davidson and King; Sirenko and Starobogatov, p. 31, figs la-b, 2a
[reconstruction;cop. Bergenhayn 1955].
1987 ChelodesbergmaniDavidsonandKing;SmithandHoare,p. 15.
Materialandlocality.Twointermediatesclerites(onebroken):RMMo6027holotype(bymonotypy)andRM
Mo6028; Klinteberget, Gotland; Klinteberg Limestone Formation, upper Wenlock (Homerian), Silurian;
Inassa/ludensisbiozones.
Reviseddiagnosis(emendedfromBergenhayn1955,p. 12).Wedge-shaped,lowarchedintermediate
scleriteswithtransversetoweaklyembayedanteriormargin,elongatebecomingmassive. Ventral
apicalareanearlyhalfoflength,anteriormarginrounded,concave,slightlyraised.Weakgranular
ornament, strong, roundedgrowthlines. Shellfieldslackingorweak.
Description(withmeasurementsforholotype).Large(length18-2mm),wedge-shaped,elongate(length/width
ratio1-47)andmassiveintermediatescleriteswithlowarching.Anteriormargintransverse,straighttoweakly
embayed(medianlength/length0-99),roundingstronglyintoshort,straight,slightlydivergentanterolateral
margins,taperingalonglongposterolateralmargins,morerapidlyfromaroundmid-lengthtobluntposterior
apex(apicalangle58°;PI.1,fig-la).Roundedgrowthridges,weakgranularornamentpatchilypreserved(PI.1,
fig.2d).Shellfieldsabsent,orveryweakwithnarrow,downward-slopinglateralfields(?P1. 1,fig. lc).Apical
length/lengthatleast0-44,withroundedconcaveanteriormarginandgrowthlines;marginraisedslightly
abovesmooth,thickenedventralsurface(PI. 1,fig. lb). Longitudinalmediallowfurrowinanteriorpartof
ventral surface, flanked by thickened lateral shell pads (PI. 1, fig. lb). Longitudinal profile gently convex
dorsally,withslightgeniculationataroundmid-length(PI. 1,fig. lc),sideslopesfairlyshallow.Transverse
profilerounded,lunate,withmarkedventralthickening(PI. 1,figs ld-e,2c);jugalangle124°,height/length
0-28.
Remarks. Davidson and King (1874)’s description was based only on the holotype, supplied by
Lindstrom,andwasappendedtoadescriptionoftrimerellidbrachiopods,althoughtheirpreferred
assignment was to an operculate rugose coral. Lindstrom (1884) subsequently described C.
1
CHERNS: SILURIANPOLYPLACOPHORA 551
bergmaniasachiton(withintheGastropoda),figuredboththeKlintebergspecimens(Lindstrom
1884,pi.2,figs 1-8)andnotedalsoonespecimenfromGrotlingbo(Gannvik;?HamraFormation,
upperLudlow).Bergenhayn(1955),alsoincludedinthespeciesother,youngerspecimens,whichin
hisearlierpaper(Bergenhayn1943,p.298)henotedascomingfromGannviken(=Gannvik;RM
Mo6029, Mo6030; Hamra Formation, upper Ludlow), and later (Bergenhayn 1955, p. 12) from
Burgsvik(‘Bursvik’, RM Mo6025, Mo6030; upperBurgsvik/HamraFormation,upperLudlow),
but hedidnot identify Lindstrom’sGannvik specimen. Lindstrom (1884, p. 51) noted ‘traces of
punctuateornamentation’onthegrowthlines,indicatedonthefigureoftheholotype(Lindstrom
1884,pi. 2,fig. 1).Thatspecimenshowscoarsesporadicpittingneartheanterior,althoughthisis
apparentlya secondary, solution feature. However, onthe otherKlintebergspecimen(Mo6028),
thereisweak,finegranularornamentpatchilypreservedparalleltogrowthlinesneartheanterior
(PI. 1, fig. 2d).
C.bergmaniischaracterizedbyanelongate,wedge-shapedform,almoststraightanteriormargin
with no more than very slight medial embayment, only gentle transverse arching, and an apical
lengthclosetohalfthelength. Thesespecificcharactersareevidentonlyintheholotypeand the
topotype. From Bergenhayn’s (1943, 1955) younger material, specimen RM Mo6030 was not
ffiiggsur1e8d-2a1n;dPiIs.n2,owfigm.is2)s.inRg,MbuMto6M0o26502i9s viseraysswiogrnne,d tionclCu.dignogtliatnsdiacnutser(ioLrineddsgter,ombut188a4,sppeic.ifi2c,
assignmentto C. bergmaniseemsquestionable; although growthlinesarepoorlypreserved, they
showsomeanteriorembayment(medianlength/length0-90),andtheapicallength/lengthis0-39.
Onmuseumlabels,BergenhaynidentifiedtwofurtherscleritesfromGrotlingboasC.bergmani(RM
Mo6033, Mo6034); although both are worn and small, they lack features characteristic ofthat
species.Anextendedstratigraphicalrangeforthespeciesbeyondthatofthetypelocality(i.e.upper
Wenlock)throughthe Ludlowcannotthereforebeconfirmed.
Chelodescf. bergmaniDavidsonand King, 1874
Plate 1,figure3
Material and locality. One silicified intermediate sclerite, RM Mo160.056; Klintebys, Gotland; Halla
Formation,upperWenlock(Homerian),Silurian.
Description.Small(length11-5mm),wedge-shapedandelongate(length/width1-58)intermediatescleritewith
blunt posterior apex (apical angle 74°), anterior margin straight, transverse (median length/length 0-98).
Roundingstronglyintoshort,straightanterolateralmarginsthatareparalleltoweaklydivergent,long,gently
tapering,posterolateralmargins,slightlyconvex.Ornamentofgrowthlinesonly.Shellfieldslacking.Apical
length/length 0-32, with rounded to V-shaped, concave anterior margin; ventral surface smooth, little
thickened. Lateralprofilestraightdorsally,sideslopesshort,taperingtoapex.Jugalangle 100°;transverse
profilewithjugalridgeflatteninganteriorly,becomingrounded;height/length0-26.
Remarks.Thisspecimenissimilarto C.bergmaniinitswedge-shaped,elongateform,whichlacks
theanteriorembaymentofotherGotlandChelodesspecies,inhavingabluntapex,relativelyshort
sideslopes,andafairlylongapicalarea.However,thisapicalareaisshorterthaninC.bergmani,
the anterolateralmarginscorrespondingly somewhat longer, and the specimen is small and little
thickened. A length-width graph (Text-fig. 6) ofgrowth stages in this specimen illustrates the
narrowform(length/width1-58)comparedwithC.gotlandicus(length/width1T6).OtherChelodes
specimens from the same locality, all ofwhich are beekitized and poorlypreserved, include two
broad cordate sclerites, probably Chelodes actinis sp. nov. (described below). The Klintebys-
localityisintheHallaFormation(lateWenlock),andthusissimilarinageoronlyslightlyolder
thantheKlintebergLimestoneatKlinteberget.
1
552 PALAEONTOLOGY,VOLUME41
ChelodesgotlandicusLindstrom, 1884
Plate 1,figure4;Plate2;Text-figure3
vp*1884 ChelodesgotlandicusLindstrom,p. 51,pi.2,figs9-27.
1897 ChelodesgotlandicusLindstrom;Etheridge,p.69.
vp.1943 ChelodesgotlandicusLindstrom;Bergenhayn,p.298.
v.1955 ChelodesgotlandicusLindstrom; Bergenhayn, p. 9, pi. 1, figs 1, 2a-b;pi. 2,fig. 1 [lectotype
selected].
v.1955 ChelodesvariegatusBergenhayn,p. 13,pi. 1,fig.4;pi.2,fig. 3[reconstruction],
v.1955 GotlandochitonlaterodepressusBergenhayn,p. 17,pi. 1,fig. 8;pi.2,fig. 5[reconstruction].
v.1955 GotlandochitontroedssoniBergenhayn,p. 19,pi. 1,fig.9;pi.2,fig.7[reconstruction].
1960 GotlandochitonlaterodepressusBergenhayn;Smith,p.150,fig.34,8[cop.Bergenhayn 1955],
1960 GotlandochitontroedssoniBergenhayn;Smith,p.150,fig. 34,7[cop. Bergenhayn1955],
1975 GotlandochitontroedssoniBergenhayn;VanBelle,pi. 1,fig.7[cop.Bergenhayn 1955].
1977 ChelodesgotlandicusLindstrom;SirenkoandStarobogatov,p.31.
1977 ChelodesvariegatusBergenhayn;SirenkoandStarobogatov,p.31.
1977 Gotlandochiton laterodepressus Bergenhayn; Sirenko and Starobogatov, p. 31, fig. 2b [cop.
Bergenhayn 1955],
1977 GotlandochitontroedssoniBergenhayn;SirenkoandStarobogatov,p.31.
71987 MorphotypeBKluessendorf,p.439,pi. 1,fig.4.
1987 ChelodesgotlandicusLindstrom;SmithandHoare,p.30.
1987 ChelodesvariegatusBergenhayn;SmithandHoare,p. 58.
1987 GotlandochitonlaterodepressusBergenhayn;SmithandHoare,p.38.
1987 GotlandochitontroedssoniBergenhayn;SmithandHoare,p. 56.
Materialandlocality.Twenty-sixintermediatescleritesfromGrotlingbo(Gannvik),Burgsvik(Bursvik)and
Rone, Gotland; upper Hemse Group-lower Hamra Formation, upper Ludlow, Silurian; lectotype RM
Mo5098fromGannvik,lowerHamraFormation,upperLudlow. SyntypesRM Mo5099-6001, 6003-6011,
6015-6020,6025-6026,6029,6032-6034,6036.
Diagnosis(emendedfromBergenhayn 1955,p. 9). Cordateandarchedintermediatescleriteswith
anterior embayment and blunt posterior apex; dorsal low radial folds defining broad elevated
centralshellfieldflankedbynarrowerlateralfields;ornamentofroundedridgesandgrooves,and
growthlines, sometimes fine granularornament; ventralapical area around one-third ofsclerite
length.
Description. Large, heart-shapedand arched,fairlybroadintermediatesclerites(lectotypelength 19-3mm;
meanlength12-65mm,s.d.=3-63mm,n=22;length/width 1-16,s.d.=0-27,n=19)withmarkedanterior
embayment(medianlength/length0-91,s.d.=0-04,n=22),roundinganterolaterallyintofairlyshort,convex,
divergenttoparallelanterolateralmargins,thenintolonger,gentlyconvexposterolateralmarginsthattaper
tobluntposteriorapex;apicalangle80°(s.d.=17°,n=18).Dorsalshellfields;broad,elevatedandtriangular
claetnetrraallffiieelldds;fcleanntkreadlbfiyelldowwitrhadwiealakfollodsw,f0o-l6d6seolfewvaitditnhg(asj.du.ga=lf0i-e1ld,innR=M15)M,on6a0r2r9ow(ePrI.a2n,dfigd.o2wa-ncw)a.rOdrnsalompeinntg
EXPLANATIONOFPLATE 2
Figs1-4.ChelodesgotlandicusLindstrom,1884;upperLudlow,Silurian;Gotland.1,holotype,RMMo5098;
GaHrnaodmtrlainantegFrboioro;mravati-ideo,wns;droGerasspnaenlc,vtiivkvee,nltyGr;raolxt,l3il.enf2gt,bolR;atMienratMleor6ame0nd2di9a;ptoesitsncetlreeirroimrteed;viiaae-tewe,ssdcorlererssipatelec,;tviHevnaetlmryar;la,xrF3io.grhmt3a,ltaitReornMa;l,GMpao0ns6tnOevrOii6ko;,r
intermediatesclerite;HamraFormation;Burgsvik(Bursvik);a-c,dorsal,rightlateralandanteriorviews
respectively; x3.4,RMM06OIO;intermediatesclerite;?upperHemseGroup;Rone;a-b,dorsalandleft
lateralviewsrespectively; x3.
PLATE2
CHERNS, Chelodes
554 PALAEONTOLOGY,VOLUME4
vptHeoiexsemttw-es;freiixgoG.rr3.o3v.uicepC-whF;se,,lRoRordneMesesp;egMcvotoetin6lvta0ernl3adyl6i;;cvuixseHw5La;.imngrxd-as3ht.,rFBo,oRmrR,mMMa1t8Mi8Mo04on6;6;O0uIp2GIp0a;e;nrn?HvLHaiuakmd,mrlroaGwarF,ooFtSrolimrilaumntragiibtaooinn;o;;nGd;Gooart?snlGanalavn,ndin,kvve,ian,kGtr,rRaoltMG,lriorMntioglgbhi6ton0;g0lba9lote;.fetr?aGllua,ptaeplrneeafdrlt
lateralview; x3.H,detailofornament; x15.
ofgrowthridgesandfurrows,andgrowthlines,mostlybetterpreservedinlateralshellareas(PI.2,figslc,3b,
4b). Fine granular ornamentparallel to growth lines well preserved in M06OII (Text-fig. 3g-h), patchily
pnr=ese5)rv;eadntearnidorwmeaarkgiinnrRouMndeMdoa6n0d2c9on(cPIa.ve1,tofiVg.-s4h)a.peAdp,icsallighltelnygetlhe/vlaetendg.thVeanptprraolxsiumraftaecelysm0o-o3t3h,(s.tdh.ic=ke0n-e0d5,,
developingshallowmedialanteriorfurrowflankedbylateralshellpads.Lateralprofileslightlyconvexdorsally,
cdheeoeinpgv.hetxT/rlaaennntsgevtrehiro0sr-et4o4prao(nsf.tidel.ero=alra0ct-he0er8da,l,nmrao=rugn1id8n)e,.dp;ojsutgearlolaantgelreal84m°ar(sg.id.n=les1s7c°,onnve=x,19t)a,pjeurgianlgf;iseilddefslaltotpeensinfgaiarlnytedreieorplyt;o
Remarks.C.gotlandicuswasdescribedbyLindstrom(1884),basedonmoreextensivematerialthan
C.bergmani,usingatypeseriesofspecimensfromGrotlingbo(Gannvik),BurgsvikandRone,and
fromVisby(Kalenskvarn;HogklintFormation,lowerWenlock).HenotedthatbothC.bergmani
and C.gotlandicusoccurredatGrotlingbo (Gannvik), althoughitisnotknownwhichspecimens
fromthislocalityheassignedto C. bergmani(seeabove). Bergenhayn(1943,p. 298)selectedtwo
ofLindstrom’sspecimensasthetype(RMMo5098,Mo5099),andlater(Bergenhayn 1955)oneof
