Early Silurian phacopide trilobites from central Victoria, Australia

2006·30 MB·English

by  Andrew C Sandford

MemoirsofMuseumVictoria63(2):215-255(2006)
ISSN 1447-2546(Print) 1447-2554(On-line)
http://www.museum.vic.gov.au/memoirs/index.asp
Early Silurian phacopide trilobites from central Victoria, Australia
AndrewC. Sandford1 andDavidJ. Holloway2
'POBox2682,Chf.ttf.nham,Victoria3192,Australia(andrewsandiord@hotmailcom).
2Museum Victoria,POBox666,Melbourne,Victoria3001,Ausiraha([email protected]).
Abstract Sandford,A.C.andHolloway,D.J.2006.EarlySilurianphacopidetrilobitesfromcentralVictoria,Australia.Memoirsof
MuseumVictoria63(2):215-255.
AdiversecomponentoftrilobitefaunasinlowerSilurianmarinestrataofcentralVictoriaaremembersofthesuborder
Phacopina,hereassignedto 19specieswithinthePhacopidae,DalmanitidaeandAcastidae.Newgeneraarerepresented
bytheblindacastidBerylacasteberylaegen.etsp.nov. andthephacopidIvopswallanensisgen. etsp.nov. Othernew
speciesarethephacopidsAcernaspisgeorgeiandAnanaspiskenleyi,andthedalmanitidsPreodontochilespringfieldensis
and Struverialplinthourgos. Two previously described species, Ananaspis typhlagogus Opik, 1953 and Dalmanites
athamasOpik, 1953 [=‘Dalmanitina(EudolatitesYaborigenumOpik, 1953],arerevised.Otherspeciesareassignedto
Bessazoon, Phacopidellal and indeterminate phacopid and dalmanitid genera. These trilobites are a significant
representationofearlySilurianPhacopinaontheworldscale.
Keywords Trilobita,Silurian,Phacopidae,Dalmanitidae,Acastidae,Victoria,Australia,systematics,newtaxa
Introduction graptolites of the late Llandovery (Telychian) Spirograptus
turriculatus-Monograptus crispus biozones (Rickards and
TrilobiteassemblagesoccurinlowerSilurian(Llandoveryand Sandford, 1998). Furthernorth,onDeepCreekatSpringfield,
Wenlock) sedimentary sequences at various localities in the uppermost part of the Springfield Formation, which is
central Victoria, between Costerfield in the north and correlatedwithbedscontaininggraptolitesoftheMonoclimacis
Camberwell in metropolitan Melbourne in the south (fig. 1). crenulata Biozone, has yielded a low diversity deep water
Despite the occurrence in these sequences of at least 45 fauna of Phacopina dominated by Preodontochile
trilobitetaxa, 19ofwhicharemembersofthePhacopina,only springfieldensis sp. nov. The overlying sandstones of the
nine species have been described previously (Table 1). These Chintin Formation contain several more diverse trilobite
include ‘Phacops’ typhlagogus Opik, 1953, Dalmanites faunas including three representatives of the Phacopina,
athamas Opik, 1953, D. wandongensis Gill, 1948 and Acernaspis georgei sp. nov., Ananaspis typhlagogusl (Opik,
‘Dalmanitina (Eudolatites)' aborigenum Opik, 1953. Fossil 1953) andBessazoon sp., suggesting anagerangefortheunit
collections inMuseumVictoriapermittherevision ofOpik’s oflatestLlandovery-earlyWenlock.
poorly known species and the description of the 16 other KnownfromasinglespecimenfromCamberwell Struverial
,
speciesofPhacopinarecorded. plinthourgossp.nov.ispartofapoorlysampledtrilobitefauna
occurringhighintheAndersonCreekFormationintheeastern
Strataandages suburbs of Melbourne, at similar horizons to those yielding
graptolites ofthelateWenlock(earlyHomerian) Cyrtograptus
Stratigraphic terminology employed here follows Rickards and lundgreni-TestograptustestisBiozone(RickardsandSandford,
Sandford(1998),anddifferssignificantlyfromthatofVandenBerg 1998).The only othertrilobitesknownfromtheformation are
etal.(2000)andVandenBerg(2003,figs5.2,5.7). three specimens of the blind illaenid Thomastus jutsoni
Trilobites of the suborder Phacopina occur at many (Chapman, 1912)andoneofanundescribedhomalonotid.
horizons in the Llandovery and Wenlock strata of central Opik(1953)documentedatrilobitefaunafromconcretion-
Victoria. The stratigraphically lowest, and one ofthe earliest bearing mudstones of the so-called ‘Illaenus band’ in the
recorded trilobites from Victoria (as Asaphus, see Selwyn, Costerfield area. Following Thomas (1937) this unit was
1863), is Phacopidellal sp. from a siltstone underlying the traditionally regarded as defining the base of the Wapentake
Lintons Creek Conglomerate Member of the Springfield Formation,butEdwardsetal.(1998)placedthe‘Illaenusband’
Formation at Keilor, at a similar horizon to beds yielding at the top of the underlying Costerfield Siltstone. Although
216 AndrewC.Sandfordand DavidJ. Holloway
Table 1.ListoftrilobitetaxaintheLlandoveryandWenlockbedsofcentralVictoria.TaxafromtheYanYeanFormationmarkedwithfoccur
onlyintheupperhorizonsoftheunit,whichareearliestLudlowinage.
YanYeanFormation(lateWenlock-earliestLudlow) WapentakeFormation(cont.)
Proetidaeindet. DalmanitesathamasOpik,1953
Decoroproetussp.f Struveriasp.2
Maurotarioneuryceps(McCoy,1876) Odontopleuridaeindet.
Encrinuridaeindet.
Sthenarocalymenesp.f ChintinFormation(latestLlandovery-earlyWenlock)
Trimerus(Trimerus)vomer(Chapman, 1912)f Proetidaesp.
Ananaspiskenleyisp.nov.f Decoroproetussp.
Phacopidaegen.indet1.f Radnoriasp.
DalmaniteswandongensisGill, 1948 Encrinuridaeindet.
KettneraspishollowayiSandford,2000f Calymenesp.
Calymenellasp. 1
AndersonCreekFormation(Wenlock)
Trimerus(Ramiotis)rickardsiSandford,2005
Thomastusjutsoni(Chapman, 1912) Acernaspisgeorgeisp.nov.
Trimerus?sp. Ananaspistyphlagogus(Opik, 1953)
Struveria?plinthourgossp.nov. Bessazoonsp.
Odontopleuridaeindet.
BylandsSiltstone(Wenlock)
SpringfieldFormation(mid-lateLlandovery)
ThomastusaopsSandfordandHolloway,1998
Proetidaeindet. Encrinuridaeindet.
Homalonotidindet. Hadromeros?sp.
Ananaspissp. 1 Calymenellasp.2
Ivopswallanensisgen.etsp.nov. Phacopidella?sp.
Ananaspistyphlagogus?(Opik, 1953) Phacopidaegen.indet.2
Struveriasp.2 Phacopidaegen.indet.3
Berylacasteberylaegen.etsp.nov. Preodontochilespringfieldensissp.nov.
Dicranurussp.
CosterfieldSiltstone(lateLlandovery?)
Selenopeltinaesp.
Odontopleuridaeindet. Dalmanitidaeindet.
WapentakeFormation(Wenlock) DeepCreekSiltstone(early-midLlandovery)
ThomastusthomastusOpik,1953 Calymenidaeindet.
Maurotarionsp.
Trimerus Ramiotis tomczykowaeSandford,2005 Uncertainstratigraphicassignment
( )
Ananaspistyphlagogus(Opik,1953) Ananaspissp.2
Acernaspis?sp.. Struveriasp. 1
EarlySilurianphacopidetrilobitesfromcentralVictoria,Australia 217
Thomas (1940, 1941, 1956) mapped the ‘Illaenus band’ as a
distinct horizon extending around most of the Costerfield
Dome,Edwardsetal.(1998:50)statedthatitisnotanextensive
mappable unit. As noted by Rickards and Sandford (1998),
fossils are notconfinedto anarrow horizoninthis part ofthe
sequence; indeed at localities on the western side of the
Heathcote-Nagambie road both Thomastus (attributed to
Illaenus by Thomas, 1937) and concretions occur 200 m
stratigraphically below and 100 m above the band as mapped
by Thomas (see fig. 9). Hence several concretion-rich beds
seem to be present over a fairly wide stratigraphical interval,
andasthereis otherwiseno distinctlithological changeinthis
partofthe sequenceitseemsaninappropriateleveltodefine a
lithostratigraphical boundary. Rickards and Sandford (1998)
defined the base of the Wapentake Formation at the top of
sandstoneslowerinthesequence(theCosterfieldSandstoneof
Reeder, 1990), andthatis the boundary accepted here. We do
not recognise the ‘Illaenus band’ as a distinct unit of the
Wapentake Formation, andweusetheformertermonly when
referringtopoorlylocalisedmaterialfromoldcollections.
The fauna of the Wapentake Formation is dominated by
theillaenidThomastusthomastus(seeSandfordandHolloway,
1998) but Opik also described three species of Phacopina,
namely ‘Phacops’ typhlagogus, Dalmanites athamas and
‘Dalmanitina (EudolatitesY aborigenum. Opik considered
that shelly elements ofthe fauna indicated a late Llandovery
age butnotedthe post-Llandovery aspect ofcertain elements
including D. athamas. From a sandy concretion within the
beds Thomas in Opik (1953: 12) identified the graptolites
Monograptus cf. jaculum and Climacograptus hughesr,
however, these identifications cannot be confirmed as the
specimens are lost, so the postulated late Llandovery age
cannotbe verified. Rickards and Sandford (1998) considered
that the presence ofAnanaspis indicated a Wenlock age for
thefauna,andnotedthe similarityofthetrilobiteassemblage
tothatoftheWenlockAnderson CreekFormation, withboth
faunas having Thomastus as the dominant element and also
containingdalmanitidandhomalonotidspecies.
At Wallan Rickards and Sandford (1998) distinguished a
massive siltstone from the underlying Chintin Formation and
namedittheBylandsSiltstone.Theunitcontainsseveralspecies
of Phacopina including the blind acastid Berylacaste berylae
gen.etsp.nov.,thephacopidsIvopswallanensisgen.etsp.nov.
andAnanaspis typhlagogus?,the dalmanitidStruveria sp. and,
at aslightly higherhorizon,Ananaspis sp. 1.As inthe case of
theWapentakeFormationassemblage,thepresenceofAnanaspis
and the similarity ofthe Wallan faunato that oftheAnderson
CreekFormationindicatesaWenlockagefortheunit.
Dalmanites wandongensis dominates a low diversity
trilobite fauna from the middle horizons of the Yan Yean
Formation at Wandong and Kilmore. Graptolites from these
horizonsbelongtothelatestWenlockColonograptusludensis
Biozone. D. wandongensis ranges into the upperhorizons of
the Yan Yean Formation, of earliest Ludlow age
Figure1.A,mapofsouth-easternAustralia;approximateareaoffig. (Neodiversograptus nilssoni Biozone), where it dominates a
IB is indicatedby arectangle. B, map ofcentral Victoriashowing morediversefaunaincludingthephacopidAnanaspiskenleyi
localitiescitedinthetext;theareascoveredbymapsinfigs.4and9 sp. nov. FarthersouthatStrathewentheupperbedsoftheYan
areindicated. YeanFormationhaveyieldedasingle specimenofaphacopid
218 AndrewC.SandfordandDavidJ. Holloway
(Phacopidae gen. indet. 1 herein)withsmall eyes, acondition homalonotidsanddalmanitids,andinthepresenceofscutelluids
thatmay be associatedwithlifeinadeep-waterenvironment and illaenids. These differences may reflect biogeographical
(ForteyandOwens, 1997: 267;Whittington, 1997: 163). provincialism or environmental preferences. Rickards, Wright
and Sherwin {in Pickett et al., 2000: 131) noted an analogous
Faunalcomparisons contrast between the Llandovery graptolite faunas of north
QueenslandandthoseofcentralVictoria,thelatterhavingmuch
Trilobites are poorly represented inthe Victorian Llandovery stronger European affinities (98% of species) than the
(Table 1). None are knownfromRhuddanian strata, and only Queenslandfaunas(75%ofspecies).Rickardsetal. considered
Hadromeros,Phacopidella?,anindeterminateflexicalymenine
thatthe compositionoftheVictorian graptolitefaunas indicate
and an indeterminate encrinurid from the Aeronian-lower stronger interaction with the Americas rather than with the
Telychian, making comparison difficultwithfaunas fromthis Uralian-CordilleranProvince.
interval elsewhere. Trilobites are more abundant in upper TrilobitesrepresentedinthelowerandmiddleWenlockof
Telychian strata. Calymenella occurs in the Calton Hill central Victoriainclude species of Thomastus, Maurotarion,
Sandstone Member of the Springfield Formation. The low Decoroproetus, Trimerus {Ramiotis), Ivops gen. nov.,
diversityPreodontochilefaunafromtheuppermostbedsofthe Ananaspis, Dalmanites, Struveria, Berylacaste gen. nov.,
Springfield Formation on Deep Creek compares only to the Dicranurus, and indeterminate Encrinuridae and
monospecific Preodontochile fauna from the Llandovery of Odontopleuridae. Faunas of similar age are present in the
Spain. These Preodontochile faunas are interpreted as Rosyth Limestone and the laterally equivalent Boree Creek
atheloptic assemblages representing a deep water biofacies Formation inthe Orange district, central western New South
whoserelationshiptootherLlandoverydeepwaterassemblages Wales, but ofthe 29 genera from those formations listed by
is unclear. Edgecombe and Sherwin (2001) interpreted the Holloway {in Pickett et ah, 2000: 163) only Ananaspis,
Aulacopleura-Raphiophorus Biofacies as inhabiting cold, DecoroproetusandDicranurusalsooccurincentralVictoria,
deep-water, offshore environments, and Chatterton and anddalmanitids,homalonotidsandacastidsareconspicuously
Ludvigsen (2004) regarded the Maurotarion-dalmanitid absentfromtheNew SouthWalesfaunas.
Biofaciesasadeepwaterfaunarepresentingdepthsnotasgreat DifferencesinfaunalcompositionbetweencentralVictoria
as the Aulacopleura-Raphiophorus Biofacies. The latter is and more northerly regions continued into the late Wenlock
representedinAustraliabyalow-diversityfaunafromtheearly and earliest Ludlow. The only trilobite genus in common
Telychian Cotton Formation in central New South Wales betweentheYanYeanFormationandtheWalkerVolcanicsof
(Edgecombe and Sherwin, 2001), containing Aulacopleura, theCanberraarea(seeHollowayinPickettetal.,2000: 164)is
Raphiophorus and Odontopleura (Sinespinaspis), and bears Sthenarocalymene{=Gravicalymene?ofHolloway’slist),and
nosimilaritytotheLlandoveryfaunasofcentralVictoria.The the latterfaunalacks phacopids and dalmanitids butincludes
late Telychian to Sheinwoodian Chintin Formation yields the scutelluids,illaenids,harpetids,cheiruridsandstaurocephalids
oldestdiversetrilobitefaunasintheSilurianofcentralVictoria. thatareabsentfromtheYanYean. Diversetrilobitefaunas of
EleventaxaarepresentincludingAcernaspisgeorgeisp. nov., mid-Wenlock to early Ludlow or possibly even late Ludlow
Ananaspistyphlagogusl(Opik,1953),Bessazoonsp.,Trimerus age occurinthe Orange-Molong districtinlimestone bodies
(Ramiotis) rickardsiSandford, 2005,Radnoria sp., Calymene within the Mirrabooka Formation, and in the laterally
sp.,Decoroproetussp.andCalymenellasp.Incompositionthe equivalent Borenore and Molong limestones. Illaenids and
ChintinfaunaiscloselycomparabletothatofthelateTelychian scutelluids dominate the fauna, which otherwise resembles
Richea Siltstone in south-west Tasmania (Holloway and that from the underlying Boree Creek Formation except that
Sandford, 1993), which also contains species ofAcernaspis, phacopids areabsent(HollowayandLane, 1998).
Bessazoon, Trimerus {Ramiotis) and Decoroproetus. Taxa Thegeneralabsenceofphacopidanddalmanitidtrilobites
representedintheRicheafaunabutnotknownfromtheChintin in the Wenlock faunas ofthe Canberra and Orange districts
fauna include Maurotarion, Dicranurus, Gravicalymene, (apartfromthe occurrence ofAnanaspis inthe Boree Creek
AnacaenaspisandLatiproetus? Formation and Rosyth Limestone) is at least partly due to
The only other Llandovery trilobite faunas known from environmental preferences. The Silurian sequences of those
AustraliaoccurintheBrokenRiverregionofnorthQueensland. districts were deposited on a series of offshore highs and
TheearlyTelychianfaunaofthePoleyCowFormationcontains troughs whereas those of central Victoria were deposited on
Gaotania,Gravicalymene?,Prostrix,Batocara,Coronocephalus, thecontinental margin. ThefaunaoftheBorenoreLimestone
Kosovopeltis, Proetus, Warburgella?, Otarion, Maurotarion, anditsstratigraphicalequivalentsissimilartothoseoccurring
Scharyia, Youngia, Sphaerexochus, Sphaerocoryphe and in lithologically similar pure limestones of Silurian age
Ceratocephala(Holloway, 1994). Fromthelaterallyequivalent elsewhere in the world (see Lane, 1972; Thomas and Lane,
Quinton Formation, Lane and Thomas (1978) described 1998).Mikulic(1981)reportedthatinmiddleandlateSilurian
Rhaxeros,Sphaerexochus,Encrinurusl,apossiblewarburgelline reeflimestones ofNorthAmericathe reefcore is dominated
andanindeterminatecalymenid,andOpik(inWhite, 1965: 43) by illaenids, scutelluids, lichids and cheirurids, and the reef
listedEncrinurus,Proetus? OnycopygeorSphaerexochus, and fringes are characterised by assemblages of cheirurids,
b
undeterminedscutelluids.Thesefaunasthusshowlittlesimilarity calymenidsandencrinurids.Heinterpretedrarephacopidand
ingenericcompositiontotheLlandoveryfaunasofVictoriaand dalmanitidtrilobitesinthereeffringesastemporarymigrants
Tasmania, and they further differ in lacking phacopids, fromnon-reefareas.
EarlySilurianphacopidetrilobitesfromcentralVictoria,Australia 219
After the Wenlock members of the Phacopina were a (1967) and later workers as diagnostic of Ananaspis, are
significant component oftrilobite faunas in New SouthWales expressedtodifferingdegreesandinavarietyofcombinations
asinVictoria.ThefaunaofthelateLudlowRosebankShalein in the species assigned. Ramskold and Werdelin (1991)
the Yass district includes both phacopids and dalmanitids restrictedAnanaspisto asmall numberofspecies ofLudlow
[Ananaspiscrossleii(EtheridgeandMitchell,1896),Dalmanites and Lochkovian ages [A. orientalis (Maksimova, 1968), to
meridianus (Etheridge and Mitchell, 1896)]. In the Early which Ramskold and Werdelin ascribed a possible Ludlow
Devonian,Echidnops,Paciphacops,Lochkovella, Odontochile, age, is from the Kokbaital Horizon of Central Kazakhastan,
several generanotbelongingtothePhacopina,andatleastone now known to be early Lochkovian; Talent et al., 2001: 61].
species (Sthenarocalymene sp.A, see Chatterton,Johnsonand SeveralotherspeciespreviouslyassignedtoAnanaspis,andof
Campbell, 1979; Holloway and Neil, 1982) were present in late Llandovery-late Wenlock age, were referred to by
bothcentralVictoriaandNewSouthWales;however,continuing RamskoldandWerdelinas Ananaspis’ orincertaesedis, and
limitations on faunal exchange is evident in the absence of said to represent ‘...a number ofmonospecific (or nearly so)
homalonotids and acastids in New South Wales, and in the genera...betweenAcernaspisandAnanaspis"(Ramskoldand
absenceofharpetidsincentralVictoria. Werdelin, 1991: 56). We are not in complete agreement
betweenourselves ontherelationships ofthesespecieswhich
Systematicpalaeontology include‘Phacops’typhlagogusOpik, 1953,redescribedbelow.
With the exception of the partly mineralized exoskeletons However, itis difficultto identify any consistently developed
charactersthatcouldbeusedtodistinguishsuchspeciesfrom
preserved in concretions of the Wapentake Formation, all
trilobite specimens figured here are preserved in mudstones others assignedtoAnanaspis s.s. byRamskoldandWerdelin,
ortobesurethatthelatterspecies aremorecloselyrelatedto
and sandstones as internal and external moulds. For
eachotherthantosomeofthespeciesexcludedfromAnanaspis
photography, internal moulds were coated with colloidal
graphite,latexpeelsweremadefromexternalmoulds,andall by those authors. Consequently Ananaspis is more broadly
were whitened with ammonium chloride. Specimens housed conceivedhereinthanbyRamskoldandWerdelin.
inMuseumVictoriaareregisteredwiththeprefixNMVP,and
AcernaspisCampbell, 1967
those housed in the collections of Geoscience Australia,
Canberra, are registered with the prefix CPC. Two missing =Eskaspis Clarkson et ah, 1977; -Murphycops Lesperance,
specimens of Ananaspis typhlagogus are documented with 1968
registrationnumbers oftheoldGeological SurveyofVictoria Typespecies. Phacops orestes Billings, 1860fromtheJupiter
collection, prefixed GSV. Trilobite localities with the prefix
PL are documented in the Museum Victoria invertebrate Formation (Llandovery), Anticosti I., Quebec, by original
designation.
palaeontologylocalityregister.
Remarks. Chatterton and Ludvigsen (2004: 39) discussed the
OrderPhacopidaSalter, 1864 possible synonymy of Acernaspis with Portlockia McCoy,
SuborderPhacopinaRichter,RichterandStruve, 1959 1846 (type speciesP. sublaevis) fromtheWenlockofwestern
SuperfamilyPhacopoideaHawleandCorda, 1847 Ireland and gave notice of their intention to apply to the
FamilyPhacopidaeHawleandCorda, 1847 International Commission of Zoological Nomenclature to
suppressthelattergenericnameasanomenoblitum.Wewould
Remarks. Inhis seminalreviewofthePhacopidaeinwhichhe support such an application as being in the best interests of
established the genera Acernaspis and Ananaspis, Campbell nomenclatural stability.
(1967)proposedaclassificationofthefamilythatheconsidered Chatterton and Ludvigsen (2004) considered Acernaspis
tobe ‘horizontal’inthesenseofSimpson(1961).Hisapproach mimicaLesperanceandLetendre, 1982tobeasynonymofA.
was criticised by some workers (e.g. Eldredge, 1973: 292) as orestes,andalsonotedthatA.superciliexcelsisHowells, 1982
creating paraphyletic and polyphyletic taxa, an outcome that differs onlyinveryminorrespectsfromorestesandmightbe
was acknowledged by Campbell (1977: 26). Nevertheless, consideredsynonymous.Theseconclusionsareinaccordwith
Acernaspis andAnanaspis have been universally recognised, the cladistic analysis of Acernaspis presented by Ramskold
and the former has come to be accepted as monophyletic and Werdelin (1991, fig. 5), in which these three taxa are
(RamskoldandWerdelin, 1991: 61). groupedtogether.CurtisandLane(1998)consideredanumber
Ananaspis continues to present more problems than of other species to be synonyms of orestes including A.
Acernaspis because it embraces greater variability in quadrilineata(Angelin, 1851),A. konoverensisMannil, 1970,
characterssuchasthewidthofthecheeksinrelationtothatof A.elliptifrons(Esmark, 1833)andA.sororiaRamskold, 1985;
theglabella,therelativelengths(exsag.)ofL2andL3,thesize however, Ramskold and Werdelin’s cladistic analysis shows
oftheeyeandthepositionofitslowermargininrespecttothe thesespeciesandorestesgroupedquiteseparately. Chatterton
lateralborderfurrow,thedepthofthevincularfurrowmedially andLudvigsenarrivedatasimilarconclusion,rejectingCurtis
andthestrengthofitsnotchinglaterally,theglabellarsculpture and Lane’s synonymy and listing a number of characters
(but in relation to this character see remarks on Acernaspis distinguishing orestes and quadrilineata, emphasising minor
below),andthewidthanddegreeoftaperofthepygidialaxis. differences in the lens formula and the proportions of the
These characters,many ofwhichwereregardedby Campbell glabella.
220 AndrewC.SandfordandDavidJ. Holloway
Acernaspis rubicundula Ramskold, 1985, from the lower Description.Cephalonsemicircular,infrontalviewwithanterior
Wenlock of Sweden, was interpreted by Ramskold as margin weakly arched. Glabella weakly convex (sag., tr.), not
intermediatebetweenAcernaspisandAnanaspiswithrespect reaching anterior cephalic margin in dorsal view, maximum
to morphological trends that he recognised between his late widthacrossfrontallobeapproximatelyequaltocephaliclength,
LlandoveryspeciesAcernaspissororiaandAnanaspisstokesii 50% maximum cephalic width and 160% occipital width (tr.).
(Milne Edwards, 1840) from the British Wenlock. He Axial furrow wide and very deep, weakly converging between
emphasisedthe glabellarwidth,the short (exsag.) L2 andthe posteriormarginandLI divergingat60°betweenLIandapoint
,
glabellartuberculationascharactersofrubicundulatypicalof opposite midlength of palpebral lobe, thereafter diverging
Ananaspis,andremarkedthatstokesiidiffersfromrubicundula forward at 20°. Anterior margin gently rounded in front of
infewfeaturesofwhichonlythestronglyforwardlyexpanding glabella,formingarccentredonposteriormargin. Occipitalring
glabellaanddeeplateralborderfurrow (onthefixigena) were with length (sag.) 15% cephalic length and width (tr.) 33%
mentioned. Neotenic changes significant in the evolution of cephalic width, with exsagittal furrow impressed in anterior
AnanaspisfromAcernaspis,includingadecreaseinthelength margindefiningobliquelydirectedlaterallobes.Occipitalfurrow
(exsag.) ofL2andthedevelopmentofglabellartuberculation, deeplyimpressed.LIhigh,lateralnodeisolatedbydeepexsagittal
were outlined by Ramskold (1988). In this context he furrow.SIdeeplaterally,weakacrossmedianpartofglabella.S2
interpretedrubicundulaasasister-taxontoallotherAcernaspis andS3moderatelyimpressedonexternal surface. S2directedat
species, exhibitingthefirstoftheseneotenicchanges. Intheir about 10° to transverse, straight, its innerend situated more or
cladistic analysis of Acernaspis, Ramskold and Werdelin less opposite 40% glabellar length from posterior. Posterior
(1991) discovered that their consensus tree was essentially branchofS3withanteriormostpointmoreorlessopposite55%
unresolvedwiththeinclusionofrubicundulabutonitsremoval sagittal glabellar length from posterior. Anterior branch of S3
an almost fully resolved consensus tree was obtained. oriented at40° to exsagittal line, weakly sigmoidal. L2 and L3
NeverthelesstheyretainedrubicundulainAcernaspis,andwe equal in length (exsag.). Anterior border furrow moderately
agreethatthemajorityofitscharactersclearlyallythespecies impressed. Anterior border wide. Eye placed with midlength
withthat genus. However, inview ofits unusual features, we opposite 38% sagittal cephalic lengthfrom posterior. Palpebral
assignrubicundulatoAcernaspiswithquestion,togetherwith areahigh,convex.Palpebrallobesteeplyinclined,flat(tr.),raised
asomewhatsimilarspeciesdescribedbelowasA.lsp. abovepalpebral area. Visual surfacelarge,withupto71 lenses,
formula(NMVP138259,fig.2D,H)556555555545543.
Acernaspisgeorgeisp.nov. Posterior border furrow deep adaxially, terminating abruptly
abaxially at a point in line (exsag.) with distal margin of eye.
Figures2,3A-B,D-E,H-I Posterior border narrow adaxially, widening slightly abaxially.
Acernaspis.—RickardsandSandford,1998:750. Librigenalfieldconcavebelow eye,notdistinctly differentiated
Type material. Holotype NMV P515 (cephalon) from PL1964, from lateral border furrow. Posterior branch of facial suture
GeologicalSurveylocalityB25,Springfield.ParatypesNMVP138259 skirting posterior margin of eye abaxially, crossing genal area
(cephalon), NMV P138262 (pygidium), NMV P138278 (pygidium), directed anterolaterally at about 25° to transverse, reaching a
NMVP147765(cephalon),NMVP147766(cephalon),NMVP147796 pointopposite33%sagittalcephaliclength,deflectedbackwards
(pygidium),NMVP312816(cephalon)fromPL256,Wallan.Paratype atsameangleabaxially. Cephalicdoublurewithvincularfurrow
NMV P138271 (cephalon) from PL598, type section ofthe Chintin deep throughout and strongly notched laterally. Cephalic
Formation,Springfield. sculpturefinelygranulate.
NMV NMV NMV
Othermaterial. P138260-P138261, P147764, Pygidium lenticular in dorsal outline. Axis comprising
P147767-P147768,NMVP147788-P147795,NMVP147797-P147806 85% sagittal pygidial length and 30% maximum pygidial
from PL256, Wallan. NMV P139447-P139453 from ‘Lancefield’ widthanteriorly,with6ringsthatarewell definedinanterior
(unknownlocalityintheParishofGoldie).ForlocalitiesseeThomas part of axis and poorly defined in posterior part, terminal
(1960), VandenBerg (1991), Sandford and Rickards (1999) (fig. 1), piece merging with postaxial region. Pleurae with 5 pleural
Sandford(2005)(fig. 11)and(fig.4). furrows, anterior one narrow (exsag.), deep, reaching 75%
Derivationofname.AfterACS’slatefather. distance to margin, remaining pleural furrows successively
shallower, posteriormostone very weak. Interpleuralfurrows
Diagnosis. Anterior cephalic border comprising 2.5% sagittal
veryshallow. Borderandfurrownotdefined.
cephalic length in dorsal view. Lateral glabellar furrows
moderately impressed, S2 extending close to axial furrow, Remarks.Acernaspisgeorgeioccurs atseveral localities inthe
posteriorbranchofS3 weakly convexforward, anteriorbranch Chintin Formation, although its relative abundance, faunal
placed posteriorly, with midlength opposite anteriormargin of associates,preservationandassociatedlithologyvarymarkedly.
palpebrallobe.Palpebralfurrowmoderatelytodeeplyimpressed, In Slab Hut Creek at PL256, Wallan, the species is common
distinctpalpebral rimfurrow, eye length (exsag.) 45% sagittal (relativeabundance44%) andtogetherwithCalymene(relative
cephaliclength,postocularareawithlength(exsag.)5%sagittal abundance35%)dominatesthefaunapreservedalmostentirely
cephaliclength,visualsurfacewith 15filesoflenseswithupto as fragmentary cephala and pygidia. The trilobites at PL256
6 (mostly 5) lenses per file. Genal angle obtusely angular, occur within bioclastic sandstone coquinas which contain
lacking prominent point or genal spine. Second and third abundantdisarticulatedcrinoidelements,gastropods,bryozoans
pygidialpleuralfurrowsmoderatelyimpressed. andclastsofsiltstoneincorporatedintothecoquinaintheplastic
EarlySilurianphacopidetrilobitesfromcentralVictoria,Australia 221
Figure2.Acernaspisgeorgeisp.nov.A-C,E-F,holotypeNMVP515,cephalon(fragment),fromPL1964,Springfield;A-C,x5;E,x6.5;F,x6.D,
H,paratypeNMVP138259,cephalon,fromPL256,Wallan;D, x5;H, x4. G,paratypeNMVP138261,pygidium, x8,fromPL256,Wallan. I,
paratypeNMVP138271,cephalon(fragment),x7,fromPL598,Springfield.(C,Dareinternalmoulds).
state,presumablyasrip-upclasts.Thecoquinas arebeddedbut differsfromtheTasmanianoneinhaving alongerpostocular
formlargeirregularbodieswithinmassivesiltstones,withwhich area,adeeperpalpebralfurrowandalongeranteriorcephalic
they have sharp contacts. At ‘Lancefield’ the species occurs border. ‘Phacops’ macdonaldiFletcher, 1950,fromtheupper
(relative abundance 14%) in afauna dominated by Bessazoon Llandovery to lower Wenlock of the Orange district, New
sp. and Calymene sp., preserved as isolated and generally South Wales, was tentatively assigned to Acernaspis by
undamagedexoskeletalelementsinmedium-grainedsandstone. Sherwin (1971), butis now assignedtoAnanaspis along with
The species can be confidently assigned to Acernaspis. its junior subjective synonym AcernaspisT oblatus [sic]
Significant characters in this assignment include the low Sherwin(seediscussionofAnanaspistyphlagogus).
glabellar profile, non-tuberculate cephalic ornament, long Acernaspisgeorgeiis most similarto the type speciesA.
(exsag.)L2(equalinlengthtoL3),wideanteriorbordervisible orestes. Thetwo species sharearelativelylong (sag.) anterior
in dorsal view, poorly defined lateral cephalic borderfurrow, cephalic border, a long postocular area and a non-spinose
shortpostoculararea, strong notching ofthe vincularfurrow genal angle. A. georgei has one fewerlens file in the eye but
laterally andthe weak expression ofthe pygidial interpleural otherwise shares asimilarlensformulato small-eyedmorphs
furrowsandthefourthandfifthpleuralfurrows. oforestes,whichhave 16files ofupto six(mostlyfive)lenses
A poorly known, unnamed species of Acernaspis was perfile.Thespeciesdiffermostnotablyinthearrangementof
described by Holloway and Sandford (1993) from the late the lateral glabellar furrows and in the deeper palpebral
LlandoveryRicheaSiltstoneofTasmania.Thepresentspecies furrowsofgeorgei.
222 AndrewC. Sandfordand DavidJ. Holloway
Figure3. A-B, D-E,H-I,Acernaspisgeorgei sp. nov. A, paratype NMV P147766, incomplete cephalon, x4,fromPL256, Wallan. B, NMV
P139448,damagedcephalonwithcephalicdoublureexposed,x3.25,from‘Lancefield’.D,I,paratypeNMVP312816,incompletecephalonfrom
PL256;D,x5;I,x4.5.E,NMVP139451,pygidium,x4,from ‘Lancefield’.H,paratypeNMVP138262,pygidium,x5,fromPL256,Wallan.C,
F-G,J-K,Ananaspistyphlagogus(Opik, 1953)fromPL6361,Springfield.C,G,J-K,NMVP312813,cephalon;C,J,Kx3.75,Gx4.75.F,NMV
P312814,thorax,x5.(A-B,Hareinternalmoulds).
Species less closely related to A. georgei and A. orestes Acernaspis? sp.
includeMannil’s(1970)EstonianspeciesA.semicircularis,A. Figures5A-D
estonica, A. sulcata, A. rectifrons and A. incerta, and the
Scottish A. xynon Howells, 1982, all of which are easily Material. NMV P139804 (incomplete cephalon) from PL385,
distinguished inhaving acutely angular genal angles orshort Costerfield.WapentakeFormation.Forlocalityseefig.9.
genal spines. In the depth and lateral extension of S2 (to a Description. Anterior and anterolateral cephalic margins
point close to the axial furrow), A. georgei resembles A. moderatelyarchedupwardsmediallyinanteriorview. Glabella
besciensisLesperanceandLetendre,1982fromtheRhuddanian weakly convex (sag., tr.), low anteriorly, sides of composite
ofAnticostiIsland,Canada{-A.salmoensisLesperance, 1988 lobedivergingatabout55°betweenlevelofS2andouterendof
fide Chatterton and Ludvigsen, 2004), the oldest known preglabellar furrow. SI curving forward adaxially, connected
species ofthe genus. A. besciensis differs fromA. georgeiin medially by wide (sag.), shallow depression. S2 moderately
manyotherfeatures,notablyinhavingfewerlensesperfilebut impressed, convexforwards, subparalleltoposteriorbranchof
morefilesintheeye(uptofourlensesin16files),ashorter(tr.) S3,itsinnerendconnectedto SI by shallow exsagittalfurrow.
andmoreforwardlyconvexS3,anarrowpreoccipitalringand L2 about 75% length (exsag.) of L3 adaxially. S3 distinctly
ashallowerpreglabellarfurrow. shallowerthan S2; posteriorbranch ofS3 notextending asfar
EarlySilurianphacopidetrilobitesfromcentralVictoria,Australia 223
adaxiallyandabaxiallyasS2;anteriorbranchnotquitemeeting
posteriorbranch,orientedatabout60° to sagittallineandvery
weakly curved, meeting axial furrow anteriorly. Preglabellar
furrow moderately impressed, continuous medially. Anterior
cephalic borderofalmostuniformlength (sag., exsag.) except
abaxially. Preserved portion of eye (more than anterior half)
with 12filesoflenses,formula(fromanterior)456767666
6 7 6 ..., sclera depressed. Palpebral lobe raised high above
palpebral area, with shallow but distinct rim furrow; anterior
part of palpebral furrow deep and narrow. Librigenal field
concave below eye and merging with lateral border furrow.
Anterior branch of facial suture cutting across anterolateral
comer of glabella (fig. 5B-C). Vincular furrow moderately
impressedmedially,deeplaterallywithstrongnotching.Medial
part of cephalic doublure not raised as high above vincular
furrow anteriorly as posteriorly, giving doublure a step-like
profileor‘bevelled’morphology.Compositeglabellarlobewith
sculptureoflow,perforatetuberclesofsmalltomoderatesize.
Remarks. The species is represented by a single, incomplete
cephalon lacking the posterior portion more or less behind a
transverse line through the medial part of SI. The specimen
differsfromAnanaspis typhlagogusfromthe sameformation
inthattheglabellaismuchmoreweaklyconvex,notasstrongly
curved in anterior outline and does not overhang the anterior
border;theanteriorborderiswider(sag.,exsag.); S2isdeeper,
morestronglycurved(nottransverseadaxially),runssubparallel
totheposteriorbranchofS3,andis connectedto SI adaxially
by a shallow exsagittal furrow; the posterior branch of S3 is
narrower (tr.) andthe anteriorbranchlonger; the preglabellar
furrow and preserved portion of the palpebral furrow are
deeper; and the visual surface does not overhang the lateral
border as strongly in dorsal view and is higher, with more
lenses perfile (up to seven instead offive as in typhlagogus).
Althoughitcouldbesuggestedthatthelowglabellarprofileof
thespecimenisduetotectonicflattening,weconsiderthatthis
is unlikely because ofthe otherdifferences fromtyphlagogus
listed,especiallythoseintheeyes.
Acernaspis? sp. differs from most species of Acernaspis
exceptA.lrubicundulaRamskold,1985,fromthelowerWenlock
of Sweden, in having tuberculate sculpture on the composite
glabellar lobe (see discussion above under genus). A.l
rubicunduladiffersfromA.?sp.inthatS2isnotascurved,does
notextendasclosetothesagittallineandisnotconnectedtoSI
adaxially by a weak longitudinal furrow; L2 is much shorter
(abouthalflengthofL3 adaxially); S3 is deeper,withashorter
Figure 4. Fossil localities of the Springfield Formation, Chintin anteriorbranch not extending as close to the posteriorbranch;
Formation and Riddell Sandstone in the Springfield area, 65 km and S2 and S3 have weakly raised rims. These differences
NNEofMelbourne;theareacoveredbythemapisindicatedonfig. suggestthattheVictorianspeciesmaynotbemostcloselyrelated
1.ThegeologyofthisareagivenbyRickardsandSandford(1998) torubicundula,despitethesimilarityinglabellarsculpture.
(fig. 6) is incorrect. The presumed faunal similarities with the
Bylands Siltstonearenotsubstantiatedondescriptionofthefauna AnanaspisCampbell, 1967
herein. On lithological and apparent faunal similarities Rickards
andSandforderroneouslycorrelatedthesiltstoneatPL1369withthe Type species. Phacops fecundus Barrande, 1846 from the
BylandsSiltstoneandshowedtheChintinFormationunderlyingit. KopaninaFormation(Ludlow),Kolednfk,Bohemia,byoriginal
AdditionalfieldobservationsshowthattheChintinFormationcrops designation.
out upstream from and hence overlies PL1369, which lies in the
uppermost beds of the Springfield Formation, as mapped by Diagnosis. Glabella moderately to strongly convex (sag., tr.),
VandenBerg(1991). vertical or slightly overhanging anteriorly in dorsal view.
224 AndrewC. Sandfordand DavidJ. Holloway
Figure5.A-D,Acernaspislsp.,NMVP139804,cephalon,x4,fromPL385,Costerfield.E-G,Phacopidaegen.indet.3,NMVP139353,enrolled
exoskeletonfromPL1369,Springfield;E,x4.0;F,x4.5.
Composite lobe expanding strongly forward, maximum width butdiffersnotonlyinhavingcharacteristicoccipitalandthoracic
twice width at LI or a little more. L2 commonly significantly axialspinesbutalsoamuchmoredeeplyincisedvincularfurrow
shorter (exsag.) than L3. Eye ofmoderate to large size, lower medially. Paciphacops Maksimova, 1972 is distinguished
edgesituatedinorslightlyabovelateralborderfurrowanteriorly especiallybythestronglyraisedscleraonthevisualsurfaceand
anddistantfromlateralborderfurrowposteriorly,visual surface the perforate glabellar tubercles, but in addition LI is more
lackingstronglyraisedsclera(maybeslightlythickeneddorsally). depressedmedially,theglabellaismoreraisedandsubquadrate
Palpebralareaashighasorhigherthanpalpebrallobe.Fixigenal in anterior profile, and the vincular furrow is deep medially.
portion of lateral border furrow deep and continuous with Lochkovella Chlupac, 1972 (see also Sandford, 2004) differs
posteriorborderfurrow. Vincularfurrow shallowto moderately fromAnanaspisinthatthecephalictuberculationisfinerandof
impressedmedially, commonly ratherweaklynotchedlaterally. more uniform size, the eye is situated very low on the cheek
Glabellarsculptureofbimodaltubercleslackingperforationsand with its lower edge indenting the lateral cephalic border, the
with superimposed and interspersed granules, doublure finely hypostomehasalong(sag.)posteriorborderwithfivemarginal
and densely granulate. Hypostome with short (sag.) posterior denticles,thepygidialinterpleuralfurrows arenotas deep,and
border having 3 angular points on margin. Pygidial pleural the pygidial granulation is coarser. Similar distinctions can be
furrowsdeepandwide(exsag.),interpleuralfurrowsdistinct. made with Nephranomma Erben, 1952 (see Sandford, 2003)
which further differs from Ananaspis in lacking a vincular
Remarks.ThisdiagnosisdistinguishesAnanaspisfromanumber furrow medially and in having adistinctive scaly sculpture on
ofcloselyrelatedgenerarecognisedsincetheworkofCampbell the cephalic doublure. See the remarks on Ivops gen. nov. for
(1967). Echidnops Sandford, 2002 is the closest toAnanaspis comparisonofthatgenuswithAnanaspis.