Protocytidium gen. nov., a new anomalocystitid mitrate from the Victorian latest Ordovician and evolution of the Allanicytidiidae

24 Pages·1999·11.2 MB·English

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PR()rOCYTIDJUMC>L^. NOV. ANEW AN0MAL0CYSTIT1D MITRATfc FROM HI
VICTORIAN LATESTORDOVICIAN AND EVOLUTION OF THE
ALLAN1CYTIDIIDAE
MARCELLO RUTA AND PETER A. JELL
Ruta, M. St Jell. PA. 1999 Oft 30: Proioivlidiunt gen. now. a new anomalocystitid milrtUe
thtm the Vici: u>vician and evolution ofthe AUanicytidiidae. Memoirs uj the
QueenslandMuseum AM 353-376 Brisbane. ISSN 0079*8835.
I I:
IhcanoniiiloLvsIUilImiWHtePtvtocyfidiumc/iioUae^n.elsp.mn.isdescribedfromdieup-
permostOrdovicianDarraweilGuim Mudsioneincentral Victoria Protocyfidiltrn has: 1)12
plateson(hecon\e\surface,wilhonly3indistalrow andtheremaining9asinErutplottm\ 2
remarkablyasymmetrical lateral^nd medianorificeplatesot'plano-concavesurface dold<d
intoa 'thecal1 portion framing the body orificeand a 'lip' projected distallybeyond iheori-
ticc: 3] much reduced plate B failing to contact right LOP; 4) narrow, elongate plate A
sutured with proximal 2/3-3/4Ofmedial margin oflefl intermediate lateral marginal plates:
S) short, slender, almost straight left spineand longer, more robust, convex., sickli-shaped
rightspine; ft)caneellaletohoneycomb-likestereom,oftenreplaced by radiatingtrabecular
i peripher> oi plates; 7)styloidtrapezoidal,bcaringsemicirculai styloidblades withradi-
ating trabecular; S) proximal blade about halfas large as distal blade. Proiocvtidiwn is
intermediate between Efiopfowapopei <inel thebasal allanicytidiid Occuhocystts koertem.
Ihe AUanicytidiidae are reviewed in the light "I this new find D Protoevtulium.
tnamaiocyxtuida^ AUanicytidiidae BulinJian, Victoria.
.
Marcello Hula, Department oj Palaeontology, The Natural History Museum ( 'nmnw/l
Road, LondonSV7591MXLUnitedKingdom Jetl, Queensland in ?JD
3300. South Brisbane4 Australia: HiJune tffUH
During field mapping o\ the Kiltnorc 1 :5Q,QO0 Edition I -AAS ( 1979). it is in thetype section of
sheet (Vandcnberg, 1992). which included a the Darrawcu Guim Mudstone which consists of
study ofOrdovician/Silunan bcrundaiy sections medium to thick bedded massive calcareous
in the Deep Creek and Ben Dluii Creek areas mudstonc\ Themudstone is black when fresh but
(Vandcnbcrg et al., 1084), numerous specimens surface exposures are usually decalcified,
of a small miirate were discovered at weathered and grey or green as at NMVRL660.
NMVPL660 in Ben Dhui Creek (Vandenberg et The associated fauna, which is preserved m mill
al.. 1984, figs I. 2A). This species has a includes the trilobite Songxitcs dawotyeitensis
combination of skeletal features making it (Campbell), the graptolite Climacogropttts
transitional between Enoplaura Wetherby, 1879 angtiftus Pernerand nautiloids. This isathin unit
from Ihe Middle to Late Ordovician of North (20m in the type section) precisely dated by the
America ((aster, 1952; Parsley, 199!) and the widespread gr iptolite Climacograptusl
allanicytidiidOccuUocystis ko&neni Haude, 995 e:\troorduunius (Sobolcvskayu) which occurs m
1
fromthe LowerDevonian ofArgentina. The new die youngest Ordovician Zone at the top of the
taxon is the oldest and only Ordovician member Bolindian Stage.
ofthe AUanicytidiidae. In thispaperwedescribe
and reconstruct the taxon. a phylogci. SYSTEMATIC PALAEONTOLOGY
position and discuss its bearingon the origin and
evolution ofthe AUanicytidiidae.
Anatomical terminology and plate
GEOLOGICAL-SETTING nomenclature(Appendix) follow Ruta on press),
Ruta & BaTtds ( I99fr, fig. 5A,H) and Rula &
The materia! described herein comes from 1999a,b.c). Specimens are housed in the
(
NMVPL660 (Vandenberg et al,, |?84, fig. 2A< Museum of Victoria, Melbourne (NMVP)
appendix 2). It is in the bed ofBen Dhui Creek, wherein the locality is also registered (NMVPL).
750m N of ihe Wallan to Woodeud road, about All photographic illustrations are of latex casts
[0km W ofWallan at AMG3 740-5860360 on taken from decalcifiedmouldsandwhitenedwith
1 1
ibeKilmore :5(),000 sheet 7S23-1 Series R 754. ammonium chloride sublimate.
1 I
5
354 MEMOIRS OFTHE QUEENSLAND MUSEUM
_*-
toeytidium elliottae gen. et sp. nov A. insideofproximal part ofconvex surfaceanddistalpart of
pIaiio-concavesarlaceo!NMVPIiH).|3lJ. -5. LUipartialplano-concavcsuriaceaiiddetailofadjacentisolated
spaie(probabl\ right spinel ol NMVPI00424. -5 and 7. respectively. C. Iraaniciu o[marginal plate from
plano-concave surface showing stereom fabric, NMVP10Q405, 11. D, partial plano-concave surface and
amaprpgeinndaalgep.latNeMiVroPi1n0pl0a4n0o-Lcon<5c,a5v,eEs,urpfaarcteiaslhpolwainnog-cstoenrceaovniefsaubrrfiac.ceNoMfVNPMUHVMPOt1)0.04«1U,a *9 I' fragmentof
A NEW VICTORIAN ANOMALOCYST1TID MITRATE 355
Class STYLOPHORA Gill & Caster, 1960 convex, sickle-shaped. Stereom cancellate to
Order MITRATAJaekel, 1918 honeycomb-like, often replaced by radiating
Suborder ANOMALOCYSTITIDA trabeculae near periphery of plates. Styloid
Caster, 1952 trapezoidal, with semicircular blades with
Family ALLANICYTIDIIDAE radiating trabeculae; proximal blade c.1/2 as
&
Caster Gill, 1967 large as distal blade.
DIAGNOSIS (modified from Caster & Gill, REMARKS. The phylogenetic position of this
1967;Caster, 1983;Haude, 1995; Ruta, inpress). new genus is discussed after the specific
Median orifice plate (MOP) longer than each treatment below but simple distinguishing
lateral orifice plate (LOP). Spines longer than features are as follows: it differs from all
distal margin of plano-concave surface. Distal anomalocystitids in the arrangement of the
partofconvex surface of3 or, more frequently, 2 median and lateral orifice plates of the
plates with transverse thickening along inside of plano-concave surface, shape of the spines and
theirdistal margins. Distal styloid blade inclined elongateplate Awith tinyplate B. Enoploura has
proximally, sometimes with lateral ear-like 5 plates in the distal row on the convex surface,
projections. Sharp, longitudinal keel on external largerC21, differentornamentandlessexpanded
surfaceofstyloid, failing to reach free margin of styloid. Occidtocystis has C21 isolated from the
proximal blade (only in basal allanicytidiids). proximal body margin, very few plates in the
Proximal blade semicircular. convex surface and Cll and C13 as marginal
REMARKS. Ruta (in press) amended and pAllaltaensi.cytMiodsitidaoefartehdeisatdivngaunicsehdedgbeynhearvainogfontlhye
expanded the diagnosis of the Allanicytidiidae, C1 andC5inthedistalrowontheconvexsurface,
formalising Haude's (1995) proposal to include by having straight spines and more elaborate
Occidtocystiskoeneni. Asdiscussedbelow,some
surface ornament.
characters supporting the sister-group
relationship between the new anomalocystitid Protocytidium eliiottae sp. nov.
and the Allanicytidiidae sensu Haude (1995) are (Figs 1-14)
diagnostic of the latter (Ruta, in press). Our
diagnosis is, therefore, more generalised than ETYMOLOGY. For Tracey Elliott ofthe Palaeontology
those of Haude (1995) and Ruta (in press) and DepartmentattheNatural HistoryMuseum, London.
aims to avoid the problem of defining the MATERIAL. Holotype: NMVP100401. Paratopes:
Allanicytidiidae mainly on the basis of the NMVP100390-100400, 100402-100403, 100405-
simplified plating of the convex surface in the 100406, 100408-100419. 100421-100436, 100438-
most derived representatives of the group 100439, 100487-100488all fromNMVPL660.
&
(Caster, 1956, 1983; Caster Gill, 1967; Philip,
& & DIAGNOSIS. As for genus.
1981; Ruta Theron, 1997; Ruta Jell, 1999c).
However, reversal of some of the characters DESCRIPTION. EXTERNAL. Measurements.
listed above occurs to some extent within the Holotype (Fig. ID): 11mm long, 6mm wide.
Allanicytidiidae. Largest specimen (Fig. 7C): 14mm long, 7mm
wide.
Protocytidium gen. nov.
Plano-concave surface (Figs 1A-B,D-E, 2B-D.
TYPESPECIES. Protocytidium eliiottaesp. nov. 4A-B,6D,7A,D, 8A,9B, 10D, 13A). Mostly flat,
ETYMOLOGY. Greek proto, the first and tytidhmu a elaxtceerpatl fmoarrgsilnigahltlyplraatiesseddilvaitedreadl mmaorrgeinso,r wlietshs
small box. Neuter.
equally into subhorizontal and vertical parts.
DIAGNOSIS. Body subelliptical to pyriibrm. Lateral body walls ofuniform depth, except for
rarely subrectangular. Convex surface of 12 rapidtaperingnearproximal anddistalends(Fig.
plates, with 3 in distal row. Medial and lateral 13C-E).PM usually 1.5 timesaswideproximally
orifice plates of plano-concave surface as distally, with straight to concave lateral
asymmetrical, divided into a 'thecal' portion margins on eitherside ofslight lateral projection
framing the body orifice and a 'lip' projected justproximaltomidlcngth,withproximalmargin
distally beyond the orifice. Plate B reduced, not strongly embayed for insertion of appendage.
in contact with right lateral orifice plate. Plate A PLM with subhorizontal part subtriangular, with
narrow, elongate. Left spine short, slender, convex lateral margin and straight or broadly
almost straight; right spine longer, more robust, concave distal margin. 1LM as long as PLM,
.
156 MEMOIRS OF THE QUEENSLAND MUSEUM
FIG.2.ProtocytidiimeltiottaegerLttsp.nov.A distalviewofdistolateraIconierofbodyNMVP100391»xl2.B
partial plano-concave surface of NMVP10i0397. xlO. C, plano-concave surface incomplete d:istallvs
NMVP100410. x10. D,partial plano-concavesurfaceofNMVP100403. -<1
A NEW VICTORIAN ANOMALOCYSTIT1DMITRATE 351
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FIi1innG2sii^13dtsetlPiovrllfdoiiipno^lmrapilondsioiic-tuicimMoodannltciaeaondvtdeptlsWaaiuelir<lKf£ivaZaccVbeo\anipcnieacLbvasaelpcs.ksungurorrrvfo.aauccnAeed-o,orcfNNoSMntMV)vPVelHoxPiidsi1uJi0rVnf0ial3lco9ew0,o-eif1<1Nr6.i.M5g,hVDtCI,t.'iNpHnasMHritMdViexaPlxo1lp.r(pKo-lMx7ain1mio7al*-l*cd1coi1ons-cnU5avi-\leeaxtsseuurrnuflaacccoecmwweiinlt>hhf
158 MEMOIRSOFTHE QUEENSLAND MUSEUM
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B
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FSsur™fanceSof2NM?Wa10?M''/l/""T""™' 8?p\keml°s"pconnocavveAs'uPl''f0eMclelloafl^apVpePnda'«geWa8n.d p*a'r"t•iaCl=plmasn.od-ecoonfcpalvaenosu-rcfoancceavoef
A NEW VICTORIAN ANOMALOCYST1TID MITRATE 359
subrectangular, with medial margin ofright ILM Distal 1/3 ofconvex surface poorly preserved in
sigmoidal and medial margin of left ILM availablematerial, butapparently consisting of3
similarly sigmoidal distal to itsjunction with the large plates in a transverserow (=C1, C3 and C5
A-C suture and proximally straight, with lateral based on comparison with Enoploura and
anddistal marginsstraight.DLM aslongasILM, Occuliocystis). C5 (Fig. 3A) subrectangular,
subrectangular to subtrapezoidal, with shallow slightlylongerthan wide. C3 slightly longerthan
distal surface deepening laterally, with C5, subpentagonal.
subcentral tubercle for spine articulation. LOP Bodystereom andsculpture. External surface of
MOP
and remarkably asymmetrical, at least coarsestereomic fabric formingradial pattern on
twice as long as wide, divided into proximal 2/3 each plate. Terrace-likeridges and riblets absent.
articulated with rest of plano-concave surface, Stereom ofthick, generally straight, sometimes
and distal 1/3 projectingbeyond distal margin of bifurcating trabeculae often connected by
transverse orifice, usually givingriseto irregular irregularly spaced, short transverse bar-like
process. Irregular gaps between distal parts of connections; trabeculae and connections delimit
adjacent margins of orifice plates. Right LOP deep pits and become more irregular and
generally slightly shorterand narrower than left randomly branching near plate margins, where
LOP or MOP. the pits are smaller, more numerous and
Plate B subtrapezoidal (based on shape of polygonal. Trabeculaeofproximal 1/2 ofconvex
available plate margins), sutured to left LOP, surface generally thickerthan elsewhere.
MOP, AandC. PlateAatleast5timeslongerthan C20-C22 (Figs 3A,C-D, 5C) with trabeculae
wide, oblique to longitudinal body axis, almost parallel to each other, rarely bifurcating,
sometimes remarkably shortened, with medial gently arcuate or straightnear lateral and medial
margin either gently convex or strongly convex margins of C20 and C22, becoming confluent
in distal 1/2 and gently concave to straight in nearcentreofproximal 1/2ofexternal surfaceof
proximal 1/2, with pointed proximal wedged both plates, where they become slightly thicker
between C and left ILM. Plate C widening and irregularly sinuous, with trabeculaeondistal
proximally. in contact with MOP. 1/2 thinner, subparallel to body axis, converging
Convex surface. All plates except C21 and C3 to centre ofplates proximally. C21 with broadly
arranged in pairs (indicatedbyplate margins and arcuate trabeculae separated by granular fabric
by mirror image arrangement of medial and on proximal 2/3, with distal trabeculae straight,
lateralplatessuturedwithC20-C22);distal 1/3of bifurcating, in fan-like arrangement. Remaining
convex surface invariably disrupted and poorly body plates with gradual changes in stereom
preserved. structure from centre to periphery (Figs
C21 with width 40% oflength, shield-shaped, IA-B,D-E, 2C-D, 4B, 7A-B,D, 8A-C, 9B, 10D);
with slightly convex longitudinal and transverse centre compact or honeycomb-like, with short,
profiles; margins very gently convex except anastomosing trabeculae; more peripheral
straight to weakly concave proximal margin, stereom of elongate trabeculae with transverse
connections; surface with cancellate or
extreme proximolateral section also with short
concave section, producing proximolateral honeycomb-like fabricproportional toplatesize.
projection. C20 and C22 subtrapezoidal, with Orifice plates with shallow pits and poorly
maximum width proximally; transverse profile defined, flat-topped trabeculae or coarse and
of plates strongly arcuate, especially near their without obvious surface pattern.
proximo-lateral angle, with thickening Proximo-distally elongate trabeculae near
iblmumnetdipartoxeilmyo-dliasttearlaltoanpgrleosx,imwailthmamredgiion-,diwsittahl pDrLoxMim(aFliga.nd1F-diGs)t.alExmtaerrgnianlssoufrfPacLeM.ofIALMandanBd
aCnIgl9esirprreogxuilmaarllytopleantetraog-doinsatall,anwgiltehs. gCre15ataensdt p(iFtisg.dIeDl)imiwtietdh lbayrget,hiwnidterlaybescpualcaeed. pPoMlygwointalh
dimension at 45° to body axis, with honeycomb fabric, with radiating peripheral
proximo-medial margins in contact with trabeculae, especially along distal margins.
latero-distal margins of C21, with sigmoidal Spines. Left spine straight or gently convex
medio-distal margins. CI and CI3 longer than externally, round in cross-section, with clavate
1
wide, irregularly hexagonal, sutured along proximal end, with hemispherical articular
straight median suture. C6 and C9 surface, tapering distally, with blunt terminus.
subtrapezoidal, smallest plates of convex Right spine slightly longer and twice as wide as
surface, lateral to Cll and CI3, respectively. left spine, sickle-shaped, flattened except for
;6o MEMOIRS OFTHE QUEENSLAND MUSEUM
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'TG 3. Pmtocviuhimi elliottae gen et sp. nov, A. styloid and proximal part ofplano-concave surface of
NMVPHKW24. *8. B. insideofplano-concavesurfaceOfNMVP100423, ><12. C, partial convex sufacewith
distal row removed to show inside of orifice plates of NMVP100398, "12. D. proximal appendage and
proximalplano-concavesurfaceofNMVP100396. • 12.
A NEW VICTORIAN ANOMALOCYSTITID MITRATE 361
A
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i
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fZ*.^
c D
PIG. &« Protacviidhtm elliottae gen el sp nov A3 inside of plano-concave surface of disarticulated
NMVP100398,*8 B,styloidofNMVPl00430 l2X,insideofplano-concavesurlaceofNMVP]00487 "
I).plano-concavesurfaceofNMVP1oo^M 'i •
362 MEMOIRS OF THE QUEENSLAND MUSEUM
1". ]_}. proximal parts of plano-concave surface and appendage ol NMVPHHM1-I. - 10. C, interior of
pNlMaVnol-cJlo0n0c4a(vr>e.su7rfadc,eplbuatnow-ictohncparvoexsiumraflacepawritthcoonrcifeiacleepdlabtvesCi2n0t-aCc2L2NMsVtiPll1Ui0n3p9l5a,ce«9o.f convex surface