Two new anomalocystitid mitrates from the Lower Devonian Humevale Formation of central Victoria

24 Pages·1999·9.6 MB·English

TWO NEW ANOMALOCYSTITID MITRATES FROM THE LOWER DEVONIAN
HUMEVALE FORMATION OF CENTRAL VICTORIA
MARCELLO RUTAANDPETERA. JELL
Ruta, M. & Jell, P.A. 1999 06 30: Two new anomalocystitid mitrates from Ihe Lower
Devonian Humevale Formation ofcentral Victoria. Memoirs ofthe Queensland Museum
43( 1): 399-422. Brisbane. ISSN 0079-8835.
The anomalocystitid mitrates Victoriacystis kolmesorwn sp. nov. and Pseudovictoriacystis
problematicagen. etsp. nov.aredescribed fromtheLowerDevonian HumevaleFormation
ofcentral Victoria. V. holmesorumvariesconsistently from thetype species, V. wilkinsi, in
the size (larger), shape and proportions ofsome body plates, the largermore robust spines
and the shape ofossicles ofdistal part ofappendage. Some specimens have a sinuous to
crook-shaped right spine; others have a proximally geniculate right spine; the left spine is
more robustthan the right and cigar-shaped. Pseudovictoriacystisproblematica has an
unusualplateconfigurationonconvexsurface,whichconsistsof14plates,withoutinterven-
ingrowII,apparentlywithoutCI6andCI8,andwithagreatlyelongateCI7.Otherwiseil is
verysimilarto V. holmesorum,especiallyindistributionofterrace-likeridgesandshapeand
G
proportions of plates on plano-concave surface. Anomulocystitida. Victoriacystis,
Pseudovictoriacystis, Devonian, Australia.
Mareello Ruta, Department ofPalaeontology, The Natural History Museum. Cromwell
Road, London SW75BD, UnitedKingdom; PeterA. Jell, Queensland Museum, P.O. Box
3300, South Brisbane4J01, Australia; received2 March 1998.
Victoriacystis was the first anomalocystitid known from a single, partially disrupted
described from Australia (Gill & Caster, 1960). individual, is similar to the new species of
Thetype species, V wilkinsiGill & Caster, 1960, Victoriacystis in the plano-concave surface, but
redeseribed by Ruta (1997), occurs in the lower has an unusual plating pattern on the convex
Ludlovian of the Dargile Formation near surface.
Heathcote and the Melbourne Formation at
GEOLOGICAL SETTING
Hawthorn, Melbourne. Although the material
from the Melbourne suburb of Hawthorn has Material described, about 30 partially to fully
been considered Lower Silurian (Gill & Caster, articulated specimens, comes from NMVPL252
1960; Talent, 1967; Ruta, 1997), it occurs in the (=Davies Quarry (Gill, 1948); =Middendorjfs
Melbourne Formation ofVandenberg(1988) and Quarry (Williams, 1964)) on the western branch
is thus Ludlovian. Its age is, therefore, similar to ofStonyCreek, about .6km N ofKinglake West
that of the specimens from Heathcote. An State School and 40km1 NNE ofMelbourne; the
incomplete and poorly preserved mitrate site is Lochkovian (Gill & Caster, 1960; Strusz,
(NMVP16880, 16881)fromtheLowerDevonian 1972; Vandenberg, 1988; Vandenberg et al.,
pWaersttowfatsheatHtruimbeutveadlbeyFGoilrlma&tiCoanstneera(r19K6i0n)gltaokVe a1r9e76f;ouHnodlilnoawsatyee&lyJegllr,ey19p8y3ri;tJieclls,il1t9s8t3o)ne.aFnosdsailrse
aff. wilkinsi. Ruta (1997) considered it insepar- concentrated in a few thin bands interspersed
able from the type species. However, additional, through about 30m exposed in the quarry wall.
morecomplete specimensfromthe same locality The diverse fossil faunas areconsideredtobe \..
show that the Lower Devonian Victoriacystis is pockets oforganic debris ... that do notrepresent
specifically distinct. natural assemblages" (Jell, 1983: 210) based on
disrupted bedding, attitude of various fossilised
Herein, we revise the diagnosis of Victoria-
& individuals and the great concentration of
cystis(Gill Caster, 1960;Ruta,inpress),taking animals in a few thin beds.
accountoftheLowerDevonianspeciesandnewly
availablespecimensofUpperSilurian V. wilkinsi Analysis of Gillocystis runcinata (ophio-
whicharetreatedelsewhere(Ruta&Jell, 1999b). cSipshtaiogiodb),laHsitlulsocyasdteicstautsra(cbtlaas(troihdo)mb(iJfeelrl,an)19a8n3d)
A second Lower Devonian anomalocystitid suggests that the animals were probably buried
mitrate genus from the Humevale Formation, when they were still alive and were flattened or
400 MEMOIRS OF THE QUEENSLAND MUSEUM
slightly crushed by pressure from overlying Few specimens retain intact appendages, and
sediment, depending upon the degree ofrigidity even in those cases, only proximal and inter-
o\^ their thecae. Plate dislocation is minimal or mediatepartsarestillinplace;ossiclesandpaired
doesnotoccuratall. Almostcompleteabsenceof platesofdistal partarenotpreserved.Usually,the
skeletal disruption, fractured individual plates, tetramerous rings of the proximal part are
preservation oforal andaboral sidesas internally complete but collapsed while retaining their
contiguous surfaces (e.g.jaw apparatus ofGillo- telescopic arrangement. Separation of ring
cystis against inner aboral surface) and collapse elements is rare as is their preservation as fully
ofperiproctal plates onto internal side ofdorsal undeformed structures. In some specimens,
thecal surface (e.g. Hillocystis) indicate that
sediment did not usually enter the body cavity paired plates and ossicles of the distal part are
and that geostatic compression of skeletons preserved intact and undeformed, albeit rarely
occurred soon after burial and before soft tissue articulatedwitheach other. Frequently,platesare
decay. disarticulated, collapsed onto the abapical
surface of ossicles or missing altogether.
Mode ofpreservation ofseveral individuals of
Sometimes, paired plates (especially proximal)
bV.uthomlamyesdiofrfuermfirsosmimtihlaatrotfotGhialtloocfySstpihsagaonbdlHaisltluos- are found detached from ossicles while still
cystis. Most mitrate specimens are preserved as overlapping each other proximo-distally. The
external moulds,oftencoveredwiththin layersof ossicles frequently maintain their alignment.
iron oxides. As in Sphagoblastus, the theca of Proximal and distal articular surfaces are
lictohacystis is a rigid structure composed of observed in at least one individual.
tightly sutured polygonal plates. In most cases,
both its convex surface and its plano-concave Although rare and largely incomplete in their
surface are found almost completely articulated. proximal 1/2, internal moulds are sometimes as-
Disruption is minimal and affects mainly LOP, sociatedwith partially disrupted external moulds.
MOP and C1-C9. Such plates generally lie in UnlikeotherLowerDevonianechinoderms from
closeproximitytoeachotherandlotherestofthe the Humevale Formation, Victoriacystis has a
skeletonandtheirmutualspatial relationshipsare relatively large, transversely elongate distal
often almost unchanged. orifice through which tine sediment could easily
Fractures occur usually along lateral margins enterthe body cavityduring burial. Similarpres-
ofthepiano-concavesurfaceandonplatesPLM, ervation is known in othercarpoids, both solutes
C and C20-C22 and are more numerous in the (Jefferies, 1990) and cornute stylophorans
proximal 1/3 ofthebody, where, as in the caseof (Jefferies, 1968; Woods & Jefferies, 1992).
other mitrates, the skeleton reaches maximum
thickness and greatest curvature (Parsley, 1991 ). SYSTEMATIC PALAEONTOLOGY
Fractures are sometimes visible at junctions
betweenhorizontalandsubverticalprojectionsof
plates DLM, 1LM and PLM. In these cases, External skeletal terminology and plate
subvertical projections often lie flush with con- nomenclature follow Ruta (in press) with
vex surface plates while retaining their mutual modifications as in Ruta & Jell (1999a).
contacts with them. In some specimens, the con- Descriptionofinternal bodyanatomy is basedon
vex surface is collapsed onto the plano-concave Ubaghs (1968, 1969). Morphological term-
surface and disruption occurs mainly at level of inology ofossicles is that ofJefferies & Lewis
sutures between lateral plates ofconvex surface (1978) and Ruta & Theron (1997). The terms
and subvertical projections of DLM, ILM and
'apical1 and 4abapicaF indicate the position of
CPIL8M.inC1co7ntirsaosfttewnitfhoutnhde ssuittuuarteidonwiotbhseCrIv6edanidn structures close to or away from the ossicular
other anomalocystitids in which, when present, process (or apex) respectively. Specimens are
&thisLeplwaitse,is1r9a7r8e;lyKionlpaltaace&(DJoelhlime,, 11993822;;JPeafrfselreiye,s dtheeposNiatteidonianlthMeuPsaelauemontoofloVgiicctaorliaC,ollMeecltbioonusrnoef
1991; Ruta, 1997; Ruta & Bartels, 1998). In a (NMVP) and the locality is registered in the
numberofspecimens,oneor.exceptionally,both locality registerat the same Museum (NMVPL).
distal spinesare foundarticulatedto DLM,orata Study and illustration of skeletal details was
short distance from the body. More frequently, made on latex casts whitened with ammonium
both spines are missing. chloride.
NEW ANOMALOCYSTITID MITRATES FROM VICTORIA 40
TfOetra1meIr'oiucstorriinagcsv,stsits\hlooildma&nsdorpurmoxispm.alnoosvsicAllels.pAl.anNoM-VcoPn1c0a0ve36s1ur.fialceNsMsVhPoLwi0n0g38t7erbr,aceC-.liNkMeVrPidIg0e0s,3Ssp5i.neDs,.
NMVP100369.E, NMVP100373. All 3
402 MEMOIRS OF THE QUEENSLAND MUSEUM
-" # 1
I
^R I 4?
V-
FrG.2. 1/c7oi7'acv\v//.v/7o/mcj5o;7/;7/sp.nov.A,EJateralandplano-co
Nx3M, VrePsp10ec8t6i2v7e.ly-.2.B1.).applpaneon-dcaognecaivnesluartefraacleovfiNewMVofPN10M0V3P718b0.03*27,1, x7. C, plano-concave surface of
NEW ANOMALOCYSTUIDMITRATES FROM VICTORIA 403
FIG
NMMVVPPI100371, -7 C, right spine mid articulation of NMVP100367, <5, D, plano-concave surface ol
NMMVVP110Q38l!x3. E, plaho-concavesurfaceofNMVP100384, -3.
404 MEMOIRS OF THE QUEENSLAND MUSEUM
^•v
Nm[VMGmV4;.P,I>I0tyc0it3°oi7nia8>cbuy^sd2usV.h^Do.llmdic(sp"asroAtri-ualmNJsMpNW,MKnVoJP\10.U3A0l6l328c,5o.n<v3>e.Gx.BsF.u.rNfNaMMcVeVsPP,11s00h0o03w3i67n36g(the<or3rlaocFtey.-pN1ei)Mk,eV-Pri21.d0gec0sj3&7sjp4itnate*als2lhlyitedtarmamaegreodu)s
KEV lAlOCYSTTTlD MURATES FROM VICTORIA
Superorder STYLOPHORAGill & Caster. I960 DIAGNOSIS. Cllf Ci: and C14 larger than
Order M1TRATAJaekel. 191 trnalanddistalplates. Proximal half
SuFbaomridleyrAPLNAOCMQACLYOSCTYISTTI1DTAIEDCAasCtaesrt,er1.9512M2 oinfCco1n6taacntdwCi.t1h8 neaitrhreorweprrotxhiamnadlisatanlglhealfo.fCC1172nocmt
REMARKS. Family groupings in the Auon^alo- dSitsrtoanlgalnygalrecuoaftCe2orI-gAenilcarugleartethsaunruLreOPbeotrweMeOnPA
cystitidaarenotsatisractory{Parsley, 1991; Ruta and C. Distal portion of app, not
& Theron. 1997. Ruta. in press: Ruta & Battels, differentiated. Styloid largeand robust. Proximal
1998). Analysis ofcharacter distribution (Ruta.
ossicular blades strongly recurved. Paired plates
in prieisiise)ytsiudgigiedasctsCatshtate,r&witGhillt,he19e6x8c,epatlliofnamoifltyh.e dsipsitnaellryobuinst,apcpigeanrd-asghaepewdi.th-o1u.t2 atsubleorncgleass.hoLdefvt
ding Placocystitidae as defined by Pai With lateral cutting edge; right spine n
(1991).arenot monopl I arsley(1991)and slender, sigmoid to geniculate, without cuttinIg
Ruta (in press) concur in recognising \)\ - edges.
lord!. rcr taxon to {Piacocysvt:
i
RhenucyStls). However, the allanicytidiids DESCRIPTION. EX TLRNAL. MeasHremtrnts,
aot closely related to these 3 genera. As Parsley Holotype: body c.28mm long. 15mm wide.
( 19^1: 16) pointedout,their '...assignment ti Smallest specimen (Figs IC, 4D): body c.21mm
lIiMguhclocoyfsttiheudareeviissaeddmfianmcidllyycsopneccuelpattiovfe'.PaiIn the bloondgs. c1350mmmmwildoneg..La7rgmemstwsipdee.cimen (Fig. 11
(199]). we restrict this family to PiacOi 1
:.....,.
only. Plano-concave surface, PI trface
SLibrcctangula:. slightly wider thill C03
Victoriaeystis Gill &. L aster, I960 surface,withsharp lateral marginsof1 1 marginal
l VPf I earlyi Ludlow GraptotiteGBaelds&, D< a a}2nAd,)2,swuibtchenmtraaxiipmlautmesw(iFditghs aIiA.-E. 2C-iEtl.y1p1rox-
Formation, Victoria; by or agnation. imal to laterodistal angles of PLM.| PM flat,
almost as wide proxnnally as disially. with
DIAGNOSIS. Rows I-V with 5,4.3.5.3 plates, convex lateral maigftjs evcept for abrupt curve
respectively CI andCfsmallerthanCl'- before joining proximal margin. Curvature of
ellipi,and CI 8 oSuuntduerde,s bee.Lt'w2eeans Clo1n5gaansdCad1j6aand iIgmhatrPgMit(iFiofgslefItAP-FM, u2sAu.aCl-r; hi
between C\S and C19 medially convex. C21 12A). PLM, ILM and DLM with Oat horizontal
shield-shaped to rhomboidal, deeply bui not projeetp ell-developed, subvertical
completely inserted between C20 and C22. B projectionsi with.gently convex cn.v, a and
absent. A-C suture oblique Robusl. transverse meeting phmo-eoncave surface at o0: (Fig.
tareirdracPe-LliVIk.e rLiadtgeersamlaimnalrygicnonsfion(edPtMo C2c0o-nvCe2x2 12D-Ei)m.aPllLyM, mwoirtehthsaunbtvweircteiacsawlidperdoijsteaclt\-ioni
laterally. Tetramerous rings wider proxtmally subtrapezoidal of uniform depth in distal
than distally, with fold ofpolyplated integm decreasing m depth proximalh (Fius IA-B, 2I A.
ngs. Styloid With median longitudinal F, 5A-C, 12B>. ILM tTapezp
proximal blade elliptical iti section, distal | ". aortef than PLM, with distally
• spine-like. Successive ossicles decreasing diverI ging, gently concave medial margins;
rapidly in size. subvertical pr lar,
Victoriacvstis holmtsorum sp. no\ comparable m size with those ofDLM and PILM.
with sutural margin in 2 shallow embayments of
,- .(.Fi.g-s'1 -i '., about same size. DLM irregularly pentagonal
p( ||l, figs With convex medial margins, with loll
: | I .1 ' I .-:." ;:il;i [9: ' mcaonrvgeixn ltatheircalkemnaerdginasn,dwistlihgmhteldyiadlo2n/n3
vertical projections subpentagonal, with SU1
vIOLOGY. For Frank and Laid Holmes, tor their margin in 2 embayments, Distal surface of 0\
1 : tance in cullcctiflg ih£ m&tH vertical or sloping distally towards coi
L. HOLOTVTE. NMY710U363. R\RAXYPE& surface, subtnangulur, shallower peripherally.
VP10036W subcentrai vertical!) elongate narrow
H i ;
.ill fromNlvlVPL252 toroidal process lor spine insertion sitting on
406 MEMOIRS OF THE QUEENSLAND MUSEUM
FIG 5. / ictoriacystis hotmesonm sp now Convex surfaces showing terrace-Eke ridges, spines, teirameraus
rings.A,NMW300387a.Bjproximalpart
D.exlenialofplano-coiieavesurf^ -3
NEW ANOMALOCYSTtTID MITRATES FROM VICTORIA 407
FIG 6. lictoriacvstis holmesofum sp. nov, Spines (A-D). plano-concave surface (CD) and proximal body
excavatiott(E).AJeftspmeNM^
<5. 1).right spine MMVPI00361. \ 5. E, NMVP100370, *7.
408 MEMOIRS OF THE QUEENSLAND MUSEUM
slightlyraised, lens-shapedprojection. Small gap above convex surface (Figs 4A-C,E-F, 5A- C.
between lateral margin of each LOP and 8D, 12C). C21 shield-shaped, subhexagonal,
DLM
medio-distal margin of each (Figs 1A-B, withgentlyconvexorrarely straightlatero-distal
2A.C 3D. 4A-B,F, 5A, 11A, 12A). MOP and margins meeting at obtuse angle, with
LOP forming almost transverse row along distal proximo-lateral marginsstraight indistal 1/2and
mhoarrigzionn.taVlerptriocjaelctpiroonjse.ctMiOonPsaabboouutt1t/w3icaselaasrwgiedaes cIoOnCv,e1x2iCn).prCo2x0iamnaldC12/22 l(aFriggesst4pAl-aFt,es5oAn-cCo,nv8eDx,
as each LOP, rectangular, with straight distal surface, almost twice as long as wide, with
margin. LOP c.3/5 size ofDLM, subpentagonal, oblique distal margins, with convexity oflateral
with bluntround latero-distal angles (Figs 1A-D, margins increasing slightly proximally (Figs
2C-D, 6A-B,D, 7A, 2A). PlateAgenerallysub- 4A-CE-F, 5A-C, 7B, IOC, 12C).
1
pentagonal to shield-shaped, c.1.5 times as large Sculpture. Terrace-like ridges on PLM (Figs
as each DLM, wedged between left ILM and C, 1A-E, 2A, C-E, 3D-E, 5D, 11C 12A) and C20-
with medial margin arcuate or geniculate, with C22 (Figs 4A-F, 5A-C, 8D, IOC, 12A-C),
lateral margin twice as long as latero-distal transverse, mostly uniform distance apart, never
margin. Plate C largest plate in body, e.1/2 as anastomosing, interrupted abruptly at interplate
long and wide as plano-concave surface, with sutures. Ridges near proximo-lateral angles of
medio-distal margin almost 1.5 times as long as PLM,C20andC22andnearproximal marginsof
latero-distal margin. Small, round tubercles C20 andC22 usually short, interrupted medially,
subcentrallv on A and on distal 1/3 ofC (Figs sometimes bifurcating, more crowded together
IA,D,2C, 3D. 6B,D, 7A). than elsewhere. Bifurcations of ridges rare, in
eitherdirection. RidgesonPLMmorerobustthan
Convex surface. 20 plates in 5 transverse rows.
ewR1aio2ctCwhh).s.51RpIoMl-aVwatgexseIiInetmawlciuyhtm.choRn4cocoawpnvlsvaeteIdeIxisIsitat(anFlydliyg.cVs.R24wo/Aiw3-tsFh,oI3fa5pnAlwda-atCIey,Vs dposilrnsiotgxaChlit2llmy0ya.-lcCRo2isn2dlv,goeepexsw,ioptwnrhiotCxshi2limIgadhilvtslaltyryailaadbnesldeleop,pgeeewrnittaalhlnymd5oc-sso6ttnemcefoalpsvaetter,
proximallyalongC20andC22'(Fig. 12B). Plates proximal ridgesrarelytransverse(Fig. 5B), more
often convex distally (Figs 4A-C, 8D), with
generally decreasing in size distally, except C15
and C19, which are smaller than CIO and C14. convexity decreasing in straighter more distal
ridges, with subcentral ridges straight or
C2-C4 subpentagonal, subequal, larger than
chevron-shaped with apex of chevron pointing
subrectangular CI and C5 andjust smaller than
hexagonal C7 and C8. Distal margins ofC1-C5 proximally, with lateral 1/2 of chevron arms
broadly convex. Lateral margins of C3 usually transverse or slightly diverging distally, with
most distal ridges transverse.
concave, sometimes straight (Figs 4A-F, 5A,C,
12C). Proximo-medial and proximo-lateral Bodystereom. Uniformlycompact(Fig.6E)orof
margins ofC7 and C8 and proximal margins of minuteperforations with irregularoutlineandno
C6 and C9 convex. C6 and C9 subpentagonal, evident distribution pattern (Fig. 8D).
often more expanded transversely than Perforations absent or very small along plate
proximo-distally (unlike C2-C4), with sub- margins, frequently replaced by narrow band of
parallel laterally diverging (rarely converging) short close spaced straight striations. Stereom of
proximal and distal margins (Figs 4A-F, 5A,C, centre of plates rarely coarser than peripheral
12C). CIO and C14 wider than long, stereom, with more widely spaced larger pores
subhexagonal, with very short medio-distal and and thicker trabeculae especially on MOP, LOP,
medio-proximal margins. C12 hexagonal, A and C (Fig. IA,D). Stereom of terrace-like
slightly wider proximally than distally (Figs ridgesonconvexsurfacegranular,morecompact
4A-F, 5A-C, 12C). CI5 and C19 subtrapezoidal, at free margins. Stereom of ridges on
with convex margins, much wider distally than plano-concave surface compact along free
proximally (Figs 4A-C, D-E, 5A-C, 12C). C16 margins, coarse and irregularly perforated by
and C18 with lateral margins strongly diverging small pores on distal 1/2, giving rise to faint
proximally, with latero-distal margins 1/2-1/3 striations on proximal 1/2. Striations at c.45° in
length ofmedio-distal margins. Suture between medio-lateral direction.
C16 and CI8 extremely short distally, slightly Spines. Leftspinestraight, massive, 1/2-5/8body
longer in proximal section. C17 subrounded to length, cigar-shaped, tapering to a blunt end in
subelliptical. <l/2 as longas C16andCI8,never distal 1/3, with cross-section of proximal 2/3
incontactwith C12orC21, flatorslightlyraised asymmetrical, with semicircular medial margin.