Terebellid polychaete burrows from the lower Palaeozoic

17 Pages·1998·8.6 MB·English

by  A T Thomas

TEREBELLID POLYCHAETE BURROWS FROM THE
LOWER PALAEOZOIC
by a. t. thomas andm. p. smith
Abstract. Trachyderma, as established by Phillips for specimens from the Upper Silurian ofthe Welsh
Borderland,wastriplypreoccupied.ChapmandescribedsupposedlycongenericmaterialfromtheSilurianof
Victoria, but that material is generically distinct and Keilorites Allan was erected to accommodate it.
Oikobesalonnom.nov.iserectedasareplacementnameforTrachydermaPhillips,whichhasbeenregarded
variouslyaseitherabodyfossiloratracefossil.Basedonitsdistinctivestructure,itisinterpretedhereasthe
thinorganicliningofaterebellidpolychaetedwellingburrow.Newillustrationsanddescriptionsaregivenboth
ofPhillips’ original specimens and ofO. citrimorion from England and Canada. Chapman’s material of
Keiloritesisalsoredescribedtoincludeburrowswithathicksedimentwall.PutativegillplumesofKeilorites
describedbyChapmaninalaterpaperarereinterpretedasichnofossilscomparablewithcertainZoophycos.
Unliketypicalmodernterebellids,theagentresponsibleforOikobesalonmayhavebeenabletoproduceanew
burrowafterexhumation,orwhenrequiredduringgrowth.Thiscapacityexplainsthemorphologicalcontrasts
betweenOikobesalonandpreviouslydescribedterebellidburrows.
TheMuchWenlockLimestoneFormationofWren’sNest(Dudley,WestMidlands)iswellknown
for its diverse and well-preserved body fossil biota. The best, articulated, material comes from
obrutiondepositswhichoccuratcertainlevels,particularlytowardsthetopoftheNodularBeds
Member(seeDoming(1983)forformalizationofButler’s(1939)lithostratigraphy). Tracefossils
alsooccurintheformation,butthesehavebeenstudiedless,andnonehasbeenformallydescribed.
MrR.FoxalloriginallybroughttheDudleyspecimenofOikobesaloncitrimorion(PI. 1,figs2-3)to
us foridentification, but it remained undetermined until Dr A.W.A. Rushton suggested that it
might have affinities with Keilorites or Trachyderma (=Oikobesalon nom. nov.): the latter
suggestionprovedto becorrect. However, studyofthe type specimensandtherelated literature
revealed a number of problems concerning the interpretation of the material and matters of
nomenclature.
The taxa dealt with here have been variously interpreted by previous authors: some have
consideredbodyfossilstoberepresented,otherstraces. Infirstdescribingspecimensnowreferred
to Oikobesalon, Phillips (1848, p. 331) erected two species of Trachyderma to include annelid
remainsdifferingfromthoseofserpulidsinhavingalarge, longandflexiblefreeexternaltubeor
covering which is membraneous or ‘coriaceous’ (=leathery) rather than calcareous: clearly,
Phillipsconsideredhisspecimenstobeichnofossils.Bycontrast,Williams(1916,p. 17)thoughtthat
herecognizedasmallheadin T. coriacea,interpretingthatspeciesasasmall,butmorecomplete,
formofT.squamosa,andthelatterasanadultlackingtheheadandtail.Chapman(1910,p. 103)
considered his Australian material to be congeneric with Phillips’, and interpreted it as the
parchment-liketubeofapolychaete. ItwasforthismaterialthatthenameKeiloritesAllan, 1927
waserected. Chapman(1919)laterreinforcedhisinterpretationbydescribingwhatheconsidered
to be the ‘gill plumes’ of the same animal. Howell (1962, p. W155) dealt with Keilorites
(Trachydermawasnotrecognizedasanindependenttaxon), and KeiloritidaeAllan, 1927, in the
section ofthe Treatise dealing with worms, diagnosing those taxa to include worms producing
perpendicular or diagonal burrows lined with membraneous material. It is therefore not clear
whether Howell regarded Keilorites as a body fossil or as a trace. Neither Trachyderma nor
KeiloriteswasmentionedinthesecondeditionoftheTreatisedealingwithtracefossils(Hantzschel
[Palaeontology,Vol.41,Part2,1998,pp.317-333,3pis) ©ThePalaeontologicalAssociation
318 PALAEONTOLOGY,VOLUME4
1975),presumablybecausetheywerebelievedtobebodyfossils. Brood(1980,p. 279)considered
Keiloritestorepresentthemucoustubeofasedentaryannelid. Studyofthetypematerialofboth
taxa, and its re-interpretation in the context ofcomparable Pleistocene and Recent specimens,
demonstatesunequivocallythattheyareichnofossils.
TERMINOLOGY
Forconvenience,theterm‘lining’isusedhereinarestrictedsensetorefertothelayeroforganic
materialformingtheburrowwallinOikobesalon.‘Wall’isusedtorefertotheconstructofsediment
externally bounding Keilorites burrows. Simple excavated burrows, where no construction has
occurredatburrowboundaries,aretermed‘unwalled’.SeeKeighleyandPickerill(1994,p.306)for
ageneraldiscussionofburrowterminology.
SYSTEMATIC PALAEONTOLOGY
Ichnogenusoikobesalonnom. nov. \protrachydermaPhillips, 1848]
«o«1829 TrachydermaLatreille,p.7[acoleopteran],
«onl829 TrachydermaGravenhorst,p.283[ahymenopteran].
«o«1829 TrachydermaWiegmann,p.421 [areptile].
Derivationofname. FromtheGreek‘oikos',houseand‘besalon',brick;alludingtotheinferredmethodof
burrowformation.Neutergender.
Remarks.Phillips(1848,p.331)proposedthegenus TrachydermaforT.coriaceaand T.squamosa
from the Ludlow of the Welsh Borderland. Chapman (1910, p. 102) described supposedly
congeneric material from the Silurian ofVictoria, Australia, assigning his material to the new
speciesT.crassitubaandto T.cf.squamosa.Allan(1927,p.240)notedthatthename Trachyderma
wasajuniorhomonymonthreecounts:theseniorhomonym(seealsoWiegmann(1834,pp.7,23);
Sherborn (1932, p. 6554)) was used by Latreille (1829) for a genus ofColeoptera. Allan (1927)
consideredPhillips’andChapman’sspecimenstobecongenericandthishasbeenfollowedbymost
subsequentauthors(e.g. Howell 1962,p. W155;Brood 1980,p.279). Re-examinationofPhillips’
andChapman’stypes,however,indicatesthattheyarenot.
BothofPhillips’ speciescompriseelongatetubes,atleastpartlysediment-filled,butwithathin
blackliningofcarbonizedorganicmaterialpreservedlocally(e.g.PI. 2,fig. 3).Theoutersurfaces
ofthespecimensshowtransverselyfusiformwrinkles. Onrelativelyunweatheredspecimens, fine,
sometimes bifurcating extensions ofthe organic layerextend outwards into the sediment. These
extensions are orientated at right angles to the tube axis (PI. 2, fig. 3). By contrast, Chapman’s
specimens have a thick sediment wall (PI. 2, figs 1-2, 8) and, although some are transversely
corrugatedexternally,theylackanorganicliningwithfusiformmarkings,andthereisnotraceof
fine lateral projections into the surrounding sediment. These differences are here regarded as
sufficienttojustifyseparateichnogenera.
Ichnopecies included. O. coriaceum Phillips, 1848; O. citrimorion sp. nov.; O. liljevalli (Brood, 1980); O.
squamosumPhillips, 1848; O.cf.squamosumPhillips(ofBrood 1980).
‘Type’ichnospecies.TheCodeoftheICZNstatesthatgenus-groupichnotaxadonotrequireatypespeciesand
thatanytypedesignationshouldbedisregarded[Articles42(b),67(m);Rideetal.(1985)].Thishasnotbeen
followeduniversally[e.g.KeighleyandPickerell(1994)],however,becauseichnologistscanfindtheconceptof
atypespeciesjustasusefulasthosewhostudybodyfossils.Thefollowingnotesconcerningthe‘type’species
ofOikobesalonareincludedshouldtherelevantarticlesbechangedinthefuture.
;
THOMASAND SMITH: POLYCHAETEBURROWS 319
FollowingAllan’s(1927,p.240)erectionofKeiloritesfor TrachydermasensuChapman, Bather(1927,p.
286)nominatedT.squamosaasthetypespeciesofTrachydermaPhillips.However,Williams(1916,p. 17)had
implicitlyselected Trachydermacoriaceaasthetypespeciesofthegenus(ICZNArticle69aiv),aselection
overlookedbysubsequentauthors.
Diagnosis.Burrow(upto30mmacrossincompressedspecimensstudied)withthinorganiclining.
Locally, lining is linearly thickened to define transverse fusiform bands. Marginally, branched
extensionsoforganicmaterialextend outwardsinto thesedimentfromthethickenedzones.
Remarks.ItisthestructureoftheliningthatisparticularlycharacteristicofOikobesalon.Noother
ichnogenus possesses an organic lining offusiform construction, while lacking a differentiated
sedimentary wall. On the basis ofGotland material, Brood (1980, fig. 3, p. 281) reconstructed
Oikobesalonasblind-endedandJ-shaped.Noneofourspecimensiscomplete,sowedonotknow
ifthatshapeischaracteristicoftheichnogenus.Weregardtheliningstructureasmoresignificant
thanoverallshape,however,becauseburrowsthoughttohavebeenproducedbysimilarmeansvary
considerably in gross morphology. Like Brood’s material, none of our specimens shows any
indication of branching, so we are satisfied that an unbranched morphology is typical of
Oikobesalon.
In hisreconstruction ofthe burrow, Brood (fig. 3, p. 281) did not showthecharacteristicfine
extensions ofthe organiclayerinto the surroundingsediment, thoughtheseareveryclearin his
photographs(figs 1a,e,2a-b). BroodalsoarguedthattheliningofO. liljevalliwasvesicularclose
to its blind end. The absence of such structures from our specimens could be due to their
fragmentarycondition.
The morphology ofthe organic lining, and its likely mechanism offormation, are discussed
separatelybelow.
Distribution.LowerCambrian,Oxfordshire;WenlockandLudlowseriesoftheWelshBorderland,Gotland
andOntario.
repOonrttehdefarsosmumspetdiimoenntofartyheroscyknsornaynmgiyngoffrToramcChaymdberrmiaanPhtiollSiiplsurainadniKneialgoeri:tefse,wOpiukbolbiesshaeldonrehcaosrdbseseenemwiindgellyy
refertomaterialcloselyresemblingPhillips’species,however.InanearlydetaileddiscussionofTrachyderma
Williams(1916,pp. 17-18) noted theorganicliningandfusiform bandsofT. coriaceaandindicatedtheir,
absencefrommanyspeciesreferredbyhimtothegenus.Wehavenotattemptedamonographicrevisionof
theichnogenus,butfaunallists(e.g. Hollandetal. 1963,p. 156)suggestthatitiswidelydistributedinthe
regressiveLudfordianfaciesoftheWelshBorderland.Theonlynon-Silurianspecimenwehavestudiedwhich
is certainly referable to Oikobesalon is BGS BDF9523 (PI. 1, fig. 5), from the Lower Cambrian ofthe
WithycombeFarmBorehole,Oxfordshire.
OikobesaloncoriaceumPhillips, 1848
Plate 1,figures 1,4;Text-figure 1a-c
1839 SerpuliteslongissimusSowerby,inMurchison,p.608,pi.5,fig. 1.
v*.1848 TrachydermacoriaceaPhillips,pp.230,331,pi.4,figs 1-2.
11898180 TT.raccohryiadceeramaPhiclolriipasc;eaChPahipllm.a;nE,thpe.ri3d1g6e.,p. 37[list],
1916 TrachydermacoriaceaPhillips;Williams,p. 17.
v.1938 TrachydermacoriaceaPhillips;Stubblefield,p. 30[referredtoKeiloritesl].
Typematerial.T.coriaceaisbasedontwofiguredsyntypes,bothfromthe‘UpperLudlow’(=WhitcliffeBeds)
ofHillsideFarm,WoodburyHill,Abberleydistrict,HerefordandWorcester. BGSGSM38370(PI. 1,fig. 1
Text-fig. 1b) comparesquitecloselywith theoriginal illustrations(Phillips 1848, pi. 4, fig. 2-2a), and this
specimenishereselectedaslectotype.StubblefieldidentifiedBGSGSM38369asthesecondfiguredsyntype.
Thatspecimenisaslabwithnumerousfragmentaryspecimens,noneofwhichresemblesPhillips’plate4,figure
1, although the lithology suggests that theprovenance is correct. Mr S.P. Tunnicliffinforms us that the
.
320 PALAEONTOLOGY,VOLUME41
specimencanbetracedbacktothe1865BGScatalogue,whereitbearsatabletnumberadjacenttothatfor
GSM38370.ThisisgoodcircumstantialevidencethatGSM38369wasavailabletoPhillips,andmaywellhave
formedpartofthetypeseries,butwedoubtthattheslabincludesthefiguredsyntype.Theparalectotypestatus
ofthematerialisthereforesubjectto somedoubt. Phillips’collectionincludesadditionalspecimens(BGS
GSM105335-105337)fromthetypelocality.Thesemayalsobeparalectotypesbut,again,nonematcheshis
plate4,figure 1
Othermaterial. BGSGSM661,blockwithnumerousspecimens, ‘UpperLudlow(DowntonPassageBeds)’
(presumably=WhitcliffeBeds/DowntonCastleSandstonetransition),northofChancesPitch,Malvernarea.
BGSGSM105333;WhitcliffeBeds,Whitcliffe,Ludlow.
Description.Specimens2-8-4-9mmwide,andpreservedasinternalandexternalmouldsinbrownweathering,
decalcifiedsiltstone.Alllieparalleltobeddingandareinterpretedasexhumedfragments.Mostarestraight
or only gently curved, but occasional specimens are flexed more strongly. The specimens are crossed
transverselybyfinelinesdelimitingfusiformbands.Theselinesoccurassharpnegativeimpressionsonexternal
moulds,andasslightlymoreround-toppedpositivefeaturesoninternalones.Hencetheyapparentlyrepresent
places where the original organic lining, now largely weathered away, was thicker. Counting along the
longitudinalmid-line,20-24bandsoccurin10mm.Disruptionofthebandsinstronglyflexedspecimens(Text-
fig. 1a,c)impliesbreakage.Themaximumsagittallengthofthebandsremainsessentiallyconstantacrossthe
sizerangeofmaterialstudied.Locally,atspecimenmargins,branchedextensionsoforganicmaterialextend
outwardsintothesedimentfromthethickenedzones(Text-fig. lc).There,theextensionsareseeninsection:
inthreedimensions,theywouldformtransverselyorientatedflanges.
Remarks.TheexhumednatureofthespecimensimpliesthattheOikobesalontubewasquiterobust
whenfresh. Breakageofthe stronglyflexed specimens suggestssignificantrigidity. Seebelowfor
comparisonswithotherspecies.
OikobesalonsquamosumPhillips, 1848
Plate2,figures3-4
v*.1848 TrachydermasquamosaPhillips,pp.230,332,pi.4,figs3^4.
vnnoonn11981880 TTrraacchhyyddeerrmmaac(fs.qsuqaumaomsoaseaPhPihlill.liapfsf;.)C;hLaipndmsatnr,omp,.p1.046,p[i=.2O7.,fliigl.je5val[lib\u.rrowpossessesneitheran
organicliningnorathicksedimentone].
1927 T.squamosaPhillips;Allan,p.286.
v.1938 TrachydermasquamosaPhillips;Stubblefield,p.32[referredtoKeiloritesl].
non1979 K.squamosusPhillips;Brood,p.252[=O.liljevalli].
Typematerial. Bather(1927,p. 286)selectedBGSGSM38371 (figuredPhillips 1848,pi.4,fig. 3),fromthe
Upper Ludlow (presumably Whitcliffe Beds) ofGorstley (common north-east ofLinton), Hereford and
EXPLANATIONOF PLATE 1
Figdsist1r,ic4t.,HOeirkeofboersdalaonndcWoorricaecsetuemr.Ph1,illleicptso,ty1p8e4,8B;GWShitGcSlMif3f8e3B7e0d.s,4,HpiolslssiibdleeFpaarraml,ecWtootoydpeb,uBryGSHiGllS,MAb1b0e5r3l3e5.y
FigBsot2-h3,x6.2.Oikobesaloncitrimorionsp.nov.2-3,holotype,DUDMGG14076;looseblockfromNodularBeds
MemberofMuchWenlockLimestoneFormation(Wenlock,Homerian),Wren’sNestInlier,Dudley,West
Midlands; x1-5and x36,paratype,NHMP6938;NiagaraGroup(Wenlock),Ontario,Canada; x1-5.
Fig.5.Oikobesalonsp.indet.;BGSBDF9523;LowerCambrian,WithycombeFarmBorehole,Oxfordshire;
x4.
Specimensshowninfigs1and4whitenedwithammoniumchloridesublimate;otherspecimensphotographed
underalcohol.
PLATE
1
THOMASand SMITH, Oikobesalon
322 PALAEONTOLOGY,VOLUME41
text-fig.1.CameralucidadrawingsofOikobesaloncoriaceumPhillips,1848.A,c,twoprobableparalectotype
specimensonBGSGSM661;notethedisruptedbandingontherightsideofa,suggestingbreakageofthetube
duringflexure,andthelateralextensionsoftheorganiclayerpreservedlocallyinc.Thespinosestructureat
theleftofcisataslightlyhigherlevelinthesedimentandprobablyrepresentsafortuitouslysuperimposed
fragment,b,portionoflectotype(BGSGSM38370)toshowfusiformbanding. Scalebarsrepresent5mm;
stipplingindicatessedimentcover.
Worcester,aslectotypeofT.squamosa.BGSGSM38372(figuredPhillips 1848,pi.4,fig.4),fromtheUpper
Ludlow,HillsideFarm,WoodburyHill,Abberleydistrict,HerefordandWorcester,isthustheparalectotype.
Description. Thefollowingisbased on thelectotype, andfocusesoncomparisonswith O. coriaceum. The
specimenismuchlessstronglycompressed,havinganoval(c.4x10mm)crosssection,reflectingpreservation
inamorecompetentcalcareoussiltstone[uncompressedspecimensofanOikobesalonspecies(PI.3,fig.4),from
theLudlowofIreland, showthattheburrowwasoriginallycircularincrosssection]. Transversefusiform
annulationsareapparent,butaredifficulttomeasure.Alongthemid-line,andparalleltothetubeaxis,band
widthrangesbetweenc.0-5—1-0mm.Phillips(1848,pi.4,fig.3)reconstructedthelectotypeascomprisinga
singleburrowshapedlikeashepherd’scrook.Itis,however,justaslikelythattwoseparatespecimensare
THOMASANDSMITH: POLYCHAETEBURROWS 323
represented on the slab (PI. 2, figs 3-4). The carbonized lining is more extensively preserved, and lateral
extensionsintothesedimentareseenlocally(seearrowedareaonPI.2,fig.3).Theparalectotypeshowsathin
carbonizedlining,withfinetransversewrinklesontheexternalmould(PI.2,fig.7),butthesearefiner,much
morecloselyspacedthaninthelectotype,andarenotclearlyfusiforminshape.
Remarks. Because of the contrasts described, we consider it unlikely that the lectotype and
paralectotypearecongeneric,andthereforebaseourconceptionoftheichnotaxonontheformer
specimen.
O. squamosum differs from coriaceum in its greater tube width and coarser-scale transverse
banding.Itispossiblethatonlyasingleichnospeciesisrepresented,andthatthesecontrastssimply
reflectdifferencesinthesizeoftheproducingorganism.Becauseofthepreservationalcontrastsand
thenomenclaturalconfusionwhichhassurroundedthesetaxainthepast,wethinkitprudentto
deferthequestionofpossiblesynonymyuntilmorematerialofsquamosumbecomesavailable.
O.liljevalli,fromtheWenlock(HogklintFormationandSliteGroup)ofGotland,isknownfrom
better, and more completelypreserved, material. It resembles squamosum in overall dimensions.
Brood (1980, p. 280) distinguished liljevalli by its thicker lining and by the presence of large
sediment-filledvesiclesposteriorly. Boththesecontrastscouldbeduetodifferencesinqualityand
completeness of preservation, however. Those specimens recorded as Keilorites cf. squamosus
(Broodp.281,figs 1a,4),fromtheLudlow(HemseGroup)ofGotland,morecloselyresemblethe
lectotypeofsquamosuminpreservation.Thetransverseextensionsoftheorganicliningarelonger
intheGotlandspecimensbut, again, thiscouldbeattributedtomorecompletepreservation.
Oikobesalon citrimorion sp. nov.
Plate 1,figures2-3,6;Text-figure3d
Derivation ofname. From the Latin ‘citrinus’, ofcitron, and Greek ‘morion', piece or portion; fancied
resemblancebetweentheholotype(PI. I,fig.2)andagrapefruitororangesegment.Nouninapposition.
Material.Holotype,DUDMGG14076;looseblockfromNodularBedsMemberofMuchWenlockLimestone
Formation,Wren’sNestInlier,Dudley,WestMidlands.Paratype,NHMP6938;NiagaraGroup(Wenlock),
Ontario,Canada.
Description.TheBritishspecimen(PI. 1,figs2-3)isapproximately20mmwide.Thisislikelytoapproximate
to the originaltube diameter(BriggsandWilliams 1981). Large-scale fusiformbands occur; these have a
maximumlengthof1-6-1-7mmmeasuredparalleltothetubeaxis.Eachoftheselargerbandsincludessmaller-
scalecomponents,alsotransverselyfusiforminshapeandtypically5-8mmwide.TheCanadianspecimenis
sslciaglhetlfyusmiofroermwbeaatnhdesre1d-,6-3b-u2tmismsilmoinlga.rAingaailnl,estsheensteiaclornetsapienctst.racItessmoafxfiinmeru-mscawliedbtahnidsicn.g3w0itmhmin,.withlarger-
Remarks. These specimens are substantially bigger than any of those assigned to previously
describedOikobesalonichnospecies:thisprobablyaccountsforthelargerscalebanding.However,
specimensofO. citrimorionaredistinguishedbyhavingthelargerbandsmadeupofsmaller-scale
subunits.
IchnogenuskeiloritesAllan, 1927
Remarks.Allan(1927,p.240)erecteithegenusKeilorites,withTrachydermacrassitubaChapman
as type, and includeditwithinhis family Keiloritidae. Bather(1927, p. 286) questioned whether
KeiloriteswasintendedfortheAustralianmaterialaloneorforallspecimenspreviouslyreferredto
TrachydermaPhillips.However,astraightforwardreadingofAllan’s(1927)noteindicatesthathe
basedhistaxonontheAustralianspeciesandnottheEnglishspecimens.Themainpurposeofthis
paperistoclarifythemorphologyandnomenclatureofOikobesalon.Wethereforeredescribeand
diagnose Keilorites on the basis of the original material, without attempting a comprehensive
revisionoftheichnogenus.
.
324 PALAEONTOLOGY,VOLUME41
Diagnosis.Unbranched,J-shapedburrow,withthicksedimentwall.Transverserugationspresent
externally.
Keiloritescrassitubus(Chapman, 1910)
Plate2,figures 1-2,8-9
v*p.l910 TrachydermacrassitubaChapman,p. 103,pi.27,figs la-b,2-3,nonpi.29,fig. 1 [=unwalled
burrow],
1927 TrachydermacrassitubaChapman;Allan,p.240[referredtoKeilorites].
1927 T.crassitubaChapman;Bather,p.286.
CTyhpaepmmaatneri1a9l1.0,Hopil.ot27y,pefigs.pelac-ibm)e;nYbarrorkaenimipnrtoovtewmoenptorwtioornkss,(PSI.ou2t,hfiYgasr8r-a9.),PaNraMtVypePs1:0N33M0-VP1P013033133(f(iPgIu.re2d,
fig.2),betweenHoyte’sPaddockandPuntRoad,SouthYarra;P10332(PI.2,fig. 1),P10343(PI.2,fig. 10),
type locality; respectively figured Chapman (1910, pi. 27, figs 2-4; pi. 29, fig. 1). All from Melbourne
Formation(LowerLudlow,nilssonigraptoliteBiozone),excavationsalongYarraRiver,SouthYarra,2-3km
eastofMelbournecitycentre,Victoria.
Description.TheholotypeisshapedoveralllikearecliningJ,withashortverticaltubeandalongerhorizontal
ponaer.atTyhpeestsuhbeowisacidricsutlianrctinsecdriomsesnstecwtailoln,,<wit5hmammathxiickmuinmtdhieahmoeltoetrypoefa(PbIo.u2t,1fi7gsmm1-.2,T8h)e.Ahnolootthyeprepaanrdattywpoe
differs in beingunlined (PI. 2, fig. 10). Externally, the tube surface bears coarse and irregular transverse
rugations(PI.2,fig.9).
Remarks.Thelackofasedimentwallsuggeststhatoneparatypebelongstoadifferentichnospecies
from the remainder ofthe type series. Material compared by Chapman (1919, p. 317) with K.
crassitubusandbyChapman(1910,p. 104)withO.squamosum(PI.2,figs5-6, 11)similarlyshows
neither sediment wall nor organic lining, and we would not assign these specimens to either
ichnogenus. Chapman (1910, p. 104) noted the absence of a wall in some of his specimens,
attributing this to dissolution ofa tube wall that he regarded as originally membraneous and
compressible.Whenpresent,theburrowwallisclearlycomposedofsediment,sothisexplanation
isincorrect.
EXPLANATIONOF PLATE 2
Figs 1-2, 8-9. Keilorites crassitubus (Chapman, 1910); Melbourne Formation (Lower Ludlow, nilssoni
graptoliteBiozone),excavationsalongYarraRiver, SouthYarra,2-3kmeastofMelbournecitycentre,
Victoria. 1,paratype,NMVP10332;Yarraimprovements,SouthYarra; x2.2,paratypeNMVP10333;
betweenHoyte’sPaddockand Punt Road, SouthYarra; x2. 8-9, holotype(brokeninto twoportions)
NMVP10330-P10331;localityasfig.1.8,dorsalviewoftheverticalportionoftheburrowandtheproximal
partofthehorizontalportion.9,ventralviewofthehorizontalportionofthetube;triangularsectionofwall
attopleftcorrespondswithtriangularexfoliatedsectionatbottomrightoffig. 8.Both x1-5.
Figs 3-4. Oikobesalon squamosum Phillips, 1848; lectotype, BGS GSM38371; Upper Ludlow, Gorstley
(commonnorth-eastofLinton),HerefordandWorcester; x1.Arrowinfig.3pointstolateralextensions
oforganiclining.
Figs5-6, 10-11.Unassignedunwalledburrows.5-6,NMVP10334(Trachydermacf.squamosaofChapman
R1i9v1e0r,,pci..5207,kfmig.ea5s)t;oHfuMmeelvbaoluernFeorcmitaytcieonntr(eL;oxwe1r-5.De1v0,onNiaMnV),Pj1u0nc3t4i3on(poafraWtoyopreiofYaT.llcorcakssCitruebeakCahnadpmYaanr)r;a
Melbourne Formation(Lower Ludlow, nilssonigraptolite Biozone), Yarraimprovements, SouthYarra,
excavationsalongYarraRiver,2-3kmeastofMelbournecitycentre,Victoria; xF5.11,NMVP10335(T
cf.crassitubaofChapman 1910,pi.27,fig.4);localityasfig. 10; x2.
Fig.7.Unassignedburrowwithcarbonizedlining;BGSGSM38372(paralectotypeofO.squamosum)-.Upper
Ludlow,HillsideFarm,WoodburyHill,Abberleydistrict,HerefordandWorcester; x2.
Specimenshowninfig. 3photographedunderalcohol;otherspecimenswhitenedwithammoniumchloride
sublimate.
PLATE2
THOMASand SMITH, Keilorites, Oikobesalon, unassignedburrows
326 PALAEONTOLOGY,VOLUME41
K.crassitubusdiffersfromO.coriaceuminlackinganorganicliningoffusiformconstructionand
inpossessingathicksedimentwall.
GenuszoophycosMassalongo, 1855?
Zoophycos!sp.
Plate3,figures 1-3,5-7
v.pl919 Trachyderma,sp.cf.crassituba,Chapm.,etaliispecierumChapman,p.317,pi. 13,figs1-3,pi.
14,figs6-12,nonfig. 5[tubularburrow].
Material.NMVP140079;SpringfieldFormation(Llandovery,turriculatus-crispusgraptolitebiozones),north
ofeasternend ofold Keilortownshipreserve, Maribyrnong River, Keilordistrict. NMVP13118—P13119,
respectivelyfiguredChapman(1919,pi. 14,figs6, 10),P13120(Chapman 1919,pi. 13,fig.2;pi. 14,fig.7),
PI3121 (Chapman1919,pi. 13,fig. 1;pi. 14,fig. 11);DeepCreekSiltstone(Llandovery),Jackson’sCreek,4
mi3F2imo)lpr.ermsNeas(tMs6ii-Vo4onnkPm(5lS)o8ic2lan1ulor4irit,yat)nPh,)-1,w4Sen0yse0dta7er6on;fShcsaKoaemtim.clehoNsrmeaMc(ntp’Virosonb,PCar1cb.e3le12yk3,k5J,maMmudfelisogg’wrusnrasevwdteo.rrCeNmhaamMip(mVmeparasePtns1ss4o(i0u1o0t9nh81-19le,;oacsaAptlin)i.dtoye1f;r4sO,sorenfegi’gaJ.sna5CmP)rei;epseeAsk1n9(d2oJe0ra,rmMsepeos.l’ns3b3oCw0ur,orerpneimek.
formations(UpperWenlock-LowerLudlow),PlentyGorge,southofMorang.GSV(GeologicalSurveyof
Victoria,housedatNMV)38945;probablylowerpartofDargileFormation(Wenlock-Ludlow),Parishof
Redcastle, Heathcote district, central Victoria, mine dumps c. 1 mile (c. 1-6km) north-east oftownship.
MelbourneFormation(LowerLudlow, nilssonigraptoliteBiozone),excavationsalongYarraRiver, South
Yarra,2-3kmeastofMelbournecitycentre:NMVP58217-P58218,P58229-P58230,(103feet(31m)below
surface,DomainRoadsewer);P13122-P13123,figuredChapman(1919,pi.14,figs9,8),(DomainRoadsewer,
South Yarra Sewerage Works); P13117, figured Chapman (1919, pi. 13, fig. 3; pi. 14, fig. 12), P58242,
(Hawthornmaindrain); P140082, (Yarraimprovements); P140080, P58237, (Melbournedistrict). Silurian
(exactageuncertain):P140077(Russell’sOrchard, Ifmiles(2km)north-north-eastofLangwarrin(railway)
Station, Keilor district); PI40078 (Russell’s Ground, pipetrack 1| miles (2-4km) north-north-east of
LangwarrinStation).
Remarks.Chapman(1919,p.315)describedputativegillplumes(cephalicprostomialappendages),
possibleeyes,andothersoft-partstructures,attributedtoKeilorites.Inmostspecimensthatwehave
studied,thefossilsappeardarkerthanthematrix(e.g.PI. 3,figs 1-2, 5).Theyarenotcarbonized,
however,butratherconsistofdarker,finergrained,sediment,whichcontrastswiththepalerhost
material. Otherspecimens occurin bleached sediment, andthese arepalerthanthe background
insteadofdarker.Mostofthematerialismore-or-lesscompletelyflattened,butreliefispreserved
insomeandthisfacilitatesreinterpretationofthespecimensasichnofossils.
EXPLANATIONOF PLATE 3
Figs 1-3, 5-7. Zoophycos?sp. indet. 1, P58242; Melbourne Formation(LowerLudlow, nilssonigraptolite
Biozone),excavationsalongYarraRiver(Hawthornmaindrain),SouthYarra,2-3kmeastofMelbourne
cLiutdylocwen)t,reP;lenxt2y.G2o,rgNeM,Vs1o4u0t0h8o1f;MoArnadnergs;onx’s1.C3r,e7e,kNoMrVMePlIb4o0u0r7n6e;fDoerempatCiroenek(USpipltesrtonWeen(lLloacnkd-ovLeorwye)r,
JhSaoycrdkiesznoohnn’asams;Cfriteg.heek1,m;acx.in21-5kb.mu6r,drNoowwMnsVistriPen1at4en0r0p(7ree9ats;et-dSnpoarrsitnhag-feihaeyslptdi)cShoanfniOdasrltgroainndegPe(i;Lpleaxsn1d(-oJ2va5em.reys5,)’,sNnwMoorVrthmPoi1fm3pe1ra1se7ts;esrinloonecanlldoictaoylfiatoynl)dd,
Keilortownshipreserve,MaribyrnongRiver,Keilordistrict;thegroovesareinterpretedasnaturalmoulds
Figo.f4h.yOpiikchonbieaslalroindgseps.;inxd2et..;BGSGSM105334;UpperLudlow,CroaghMartin,Doonquin,Dingle,western
Ireland; x2.
Specimensshowninfigs1-2,5and7photographedunderalcohol;otherspecimenswhitenedwithammonium
chloridesublimate.