Tertiary Ostracoda from the Lindi area, Tanzania

96 Pages·1991·41.5 MB·English

by  M Ahmad

Bull. Br. Mus. Nat. Hist. (Geol.)46(2): 175-270 Issued31 January 1991
Tertiary Ostracoda from the Lindi area,
Tanzania
MANZOOR AHMAD
Customs Co-operation Council, RuedeVIndustrie26-38, B-1040Brussels, Belgium
(on secondment from the CentralBoardofRevenue, Islamabad, Pakistan).
JOHN W. NEALE
DepartmentofGeology, The University, Hull, England, HU6 7RX
QADEER A. SIDDIQUI
DepartmentofGeology, StMary's University, Halifax, NovaScotia, Canada, B3H3C3
CONTENTS
Introduction j78
Stratigraphy I79
PreviousworkonTanzanianostracods I79
Systematicdescriptions:SubclassOstracodaLatreille,OrderPodocopidaMuUer 179
SuborderPlatycopaSars I79
FamilyCytherellidaeSars I79
GenusCytherellaJones I79
Cytherellalindiensissp.nov I79
Cytherellamediocalvasp.nov 182
GenusCytherelloideaAlexander 184
Cytherelloideagemellatasp.nov 184
Cytherelloideapatagiatasp.nov 184
Cytherelloideasp.A 187
Cytherelloideasp.B 187
SuborderPodocopaSars 187
SuperfamilyBairdiaceaSars 187
FamilyBairdiidaeSars 187
GenusBairdiaM'^Coy 187
Bairdiaamygdaloides(Brady)oblongatavandenBold 187
Bairdiacf.attenuataBrady 188
Bairdiacf.schulzi(Hartmann) 188
GenusParanesideaMaddocks 188
ParanesideafracticorallicolaMaddocks 188
Paranesideanigrescens(Ruggieri) 188
Paranesideacf.fortificata(Brady) 188
Paranesideasp.A 191
GenusTriebelinavandenBold 191
Triebelinahowei(Stephenson) 191
SuperfamilyCytheraceaBaird 191
FamilyCytheridaeBaird 191
SubfamilyCytherinaeBaird,TribePaijenborchelliniDeroo 191
GenusPaijenborchellaKingma 191
SubgenusPaijenborchellaKingma 191
Paijenborchella{Paijenborchella)cf.iocosaKingma 191
SubgenusEopaijenborchellaKeij 192
Paijenborchella(Eopaijenborchella)quasimalaiensissp.nov 192
Paijenborchella(Eopaijenborchella)quasimalaiensisdilatasubsp.nov 192
Paijenborchella(Eopaijenborchella)disaduncasp. nov 194
MorphotypesA-D 194
FamilyLeptocytheridaeHanai I94
GenusLeptocythereSars I94
Leptocythereamoenasp.nov I94
Leptocytherefastigatasp.nov 196
GenusCallistocythereRuggieri 196
Callistocytherejugosasp.nov 198
^4q(^'^
9,(\^
111
176 AHMAD,NEALE&SIDDIQUI'
GenusTanellaKingma 198 'I
Tanellasp.A 198
Tanellasp.B 198
FamilyCytherideidaeSars 201
SubfamilyCytherideinaeSars 201
GenusClithrocytherideaStephenson 201
Clithrocytheridealsemilunasp.nov 201
GenusRostrocytherideaDingle 201
Rostrocytheridealsp 201
FamilyKrithidaeBrady&Robertson 201
SubfamilyKrithinaeMandelstam 201
GenusKritheBrady,Crosskey&Robertson 201
Kritheburdigaliasp.nov 201
Kritheliebauisp.nov 202
Krithemedioelatasp.nov 205
GenusOmmatokritheAhmad 205
OmmatokritheprolataAhmad 205
GenusParakrithevandenBold 205
Parakrithecicatricosasp.nov 205
FamilyTrachyleberididaeSylvester-Bradley 206
SubfamilyTrachyleberidinae,TribeTrachyleberidiniSylvester-Bradley 206
GenusTrachyleberisBrady 206
Trachyleberisduplexsp.nov 206
GenusGujaratellaKhosla 206
Gujaratellaltanzaniensissp.nov 206
GenusHaughtonileberisDingle 209
HaughtonileberisradiataDingle 209
Haughtonileberisrastapuriensissp.nov 209
GenusAcanthocythereisHowe 209
Acanthocythereispostcornis(Siddiqui) 211
GenusFalsocythereRuggieri 21
Falsocytheremaccagnoi(Ciampo) 211
TribeCostainiHartman&Puri 21
GenusCarinocythereisRuggieri 21
Carinocythereissp 211
GenusCostaNeviani 211
Costalhullinasp.nov 211
CostatrudisAhmad 212
GenusTrachyleberideaBowen 212
Trachyleberidea?cirratasp.nov 212
GenusStigmatocythereSiddiqui 215
Stigmatocytherebornhardtisp.nov 215
Stigmatocythereintextasp.nov 215
TribePterygocythereidiniPuri 217
GenusIncongruellinaRuggieri 217
Incongruellinatonsasp.nov 217
TribeEchinocythereidiniHazel 217
GenusHenryhowellaPuri 217
Henryhowellasentosasp.nov 217
SubfamilyBuntoniinaeApostolescu 217
GenusBuntoniaHowe&Chambers 217
Buntoniasp 217
GenusAmbocytherevandenBold 218
Ambocytheresp 218
GenusOccultocythereisHowe 218
Occuliocythereisafricanasp.nov 218
GenusIdiocythereTriebel 220
Idiocytheresp.A 220
SubfamilyCampylocytherinaePuri,TribeLeguminocytheriniHowe 220
GenusLeguminocythereisHowe{inHowe&Law) 220
Leguminocythereisdingleisp.nov 220
GenusRuggieriaKeij 220
SubgenusRuggieriaKeij 220
Ruggieria(Ruggieria)furcillasp.nov 222
FamilyHemicytheridaePuri 222
SubfamilyHemicytherinaePuri,TribeAuriliniPuri 222
GenusAurilaPokorny 222
TERTIARYOSTRACODAFROMTHELINDIAREA,TANZANIA 177
Aurilaconcentricasp. nov 222
MorphotypesA-B 224
GenusProcythereisSkogsberg 224
Procythereisaligerasp.nov 224
Procythereisradialasp.nov 224
SubfamilyThaerocytherinaeHazel,TribeThaerocytheriniHazel 225
GenusHermanitesPuri 225
Hermanitescarchesiumsp.nov 225
Hermanitesmongoensissp.nov 225
MorphotypesA-B 227
Hermanitespercultussp.nov 227
TribeBradleyiniBenson 229
GenusBradleyaHornibrook 229
Bradleyalsp.A 229
Bradleya?sp.B 229
GenusQuadracythereHornibrook 231
Quadracytherearcana(Lubimova&Guha) 231
Quadracytherearcanacornigerasubsp.nov 231
Quadracythere?acutasp.nov 231
Quadracytheredistentasp.nov 231
Quadracytherekentisp.nov 233
QuadracytheresubquadraSiddiqui 233
QuadracytheretrijugisHolden 233
Quadracytherevangasp.nov 233
Quadracytheresp. A 235
GenusCrenaleyanov 235
Crenaleyatuberissp.nov 237
Crenaleyasp.A 237
Crenaleya?sp 237
GenusUrocythereisRuggieri 237
Urocythereissalebrosasp.nov 237
Urocythereis?apolegmasp.nov 238
SubfamilyOrionininaePuri 238
GenusAnterocythereMcKenzie&Swain 238
Anterocytheresp.BofSwain&Gilby 238
GenusCauditesCoryell&Fields 240
Cauditessp 240
Cauditescf.rosaliensisSwain 240
FamilyLoxoconchidaeSars 240
SubfamilyLoxoconchinaeSars 240
GenusLoxoconchaSars 240
SubgenusLoxoconchaSars 240
Loxoconcha(Loxoconcha)mbanjaensissp.nov 240
SubgenusLoxocorniculumBenson&Coleman 243
Loxoconcha{Loxocorniculum)postnodosasp.nov 243
MorphotypesA-B 243
Loxoconcha{Loxocorniculum)tricomissp.nov 243
Loxoconcha{^Loxocorniculum)cf.longispinaKeij 245
SubgenusMyrenaNeale 245
Loxoconcha{Myrena)loculussp.nov 245
SubgenusPalmoconchaSwain&Gilby 246
Loxoconcha{Palmoconcha)pinguissp.nov 246
GenusPhlyctocythereKeij 246
Phlyctocytherereniformissp.nov 246
FamilyParacytherideidaePuri 246
GenusParacytherideaMiiller 246
ParacytherideaanapetesAhmad 246
Paracytherideaculmensp.nov 248
MorphotypeA 248
FamilyCytheruridaeMiiller 248
SubfamilyCytherurinaeMiiller 248
GenusTanzanicythereAhmad 248
Tanzanicytherepterota(Ahmad) 248
GenusHemicytheruraElofson 250
Hemicytherurasubulatasp.nov 250
GenusSemicytheruraWagner 252
Semicytheruraemphysemasp.nov 252
178 AHMAD,NEALE&SIDDIQUI
Semicytheruraopeatasp.nov 252
Semicytherurasp.A 252
SubfamilyCytheropterinaeHanai 253
GenusCytheropteronSars 253
Cytheropteronepelyxsp.nov 253
Cytheropteroncf.nipeensisvandenBold 253
Cytheropteronsp.A 253
GenusKangarinaCoryell&Fields 253
Kangarinasp 253
FamilyXestoleberididaeSars 255
GenusUroleberisTriebel 255
Uroleberiskymasp.nov 255
Uroleberis!sp 255
FamilyBythocytheridaeSars 255
GenusBythoceratinaHornibrook 255
Bythoceratinalasteriasp.nov 255
Bythoceratinasp. A 257
SuperfamilyCypridaceaBaird 257
FamilyMacrocyprididaeMiiller 257
GenusMacrocyprisBrady 257
Macrocyprislsp.A 257
Macrocyprissp.B 257
Incertaesedis 258
GenusAsp 258
GenusBsp 258
GenusCsp 258
Palaeoecology 259
Faunalassemblages 259
Ostracodbiozones 263
Conclusions 263
FCRMsampledata 264
Acknowledgments 265
References 265
Index 268
Synopsis. Ostracods from the Upper Eocene-Lower Miocene of the Lindi area of Tanzania, East Africa, are
described. 114speciesand2subspeciesarerecognized,ofwhich51 speciesand2subspeciesarenew. Anewgenus,
Crenaleya, isproposed.
The stratigraphical distribution of the ostracod faunas indicates a close relationship with regional geological
events, the faunas becoming less diverse during the Oligocene regression and more diverse during the Miocene
transgression. Thesedimentationratededucedfromvalve/carapaceratiosshowsahigherrateofsedimentationfor
the Upper Eocene and Lower Miocene than for the Oligocene. The faunas, in general, are indicative of warm
shallowshelf-seaswithnearbyreefs,withtemperaturesvaryingbetween 10°-25°Candwaterdepthsofabout50m.
Three ostracod biozones are recognized; the presence ofa deep water fauna in the Lower Miocene ofthe South
Mtweroregionisalsorecorded.
TheTanzanianostracodsshowaffinitieswiththoseofIndia,PakistanandSouthAfrica;thereareafewspeciesin
commonwiththeMediterranean,CaribbeanandIndo-Pacificregions.
during the Chattian was followed by transgression, resulting
INTRODUCTION in widespread deposition of Lower Miocene beds, a wide
occurrence recognized by Eames & Kent (1955). The Pliocene
is not well known in this area though farther north in the
The fossil ostracods described in this paper come from the synclinal areas and seaward of the Dar-es-Salaam embay-
Lindi area, which lies in the Southern Province ofTanzania ment,post-Miocenesedimentsamounttothousandsoffeetin
and is bounded by latitudes 9° 50' S and 10° 05' S, and thickness.
longitudes 39° 40' E and 39° 45' E. The position of the area The whole succession dips gently to the ENE, the dip not
relative to the remainder of coastal East Africa is shown in exceeding 10°. According to Eames et al. (1962), the late
Fig. 1. Cretaceous to Pliocene marine sediments are known Eocene to early Miocene was a time oflow tectonic activity
from the area, but the present study is concerned only with and the region seems to have undergone gentle overall
those ranging from Upper Eocene to Lower Miocene. These subsidence with no apparent violent movement; the whole
Palaeogene beds are in continuity with, or sometimes rest sequence of Cretaceous-Tertiary sedimentation seems to
with slightunconformityon, the UpperCretaceousrocksand have been associated with the various cycles ofbroad gentle
have been laid down continuously from late Eocene times warping. Kent {in Burk & Drake 1974) mentions a period
into the overlying Oligocene. A small break in deposition of peneplanation, occupying most of the Cretaceous and
ERTIARYOSTRACODAFROMTHELINDIAREA,TANZANIA 179
representedby about 5 m ofsoftbuffsiltysandstones, which
become increasingly calcareous upwards and contain some
lensesofgypsiferousclay. In the areaimmediatelytotheeast
of Lindi Town (Kitunda Cliff) the silty sandstones pass
upwardsintomassive reeflimestones, but north ofLindi Bay
clays and silts appearto replace part ofthe limestones.
BP-Shell surveyshave shown that LowerMiocene bedsare
brought in on the downthrow side of the Lindi Fault in
Lindi Bay, showingevidence oflarge-scalecontemporaneous
movement ofthe fault. At RasTapuri a brecciaofvery large
blocks of Miocene limestone is developed 400 m from the
easternmost Eocene limestones.
PREVIOUS WORK ON TANZANIAN
OSTRACODS
TheearliestdescriptionofostracodsfromTanzaniawasgiven
bySars(1910), whodescribed29Recentspeciesbelongingto
seven genera, all from the fresh-water Lake Tanganyika.
Rome (1962) monographed the Lake Tanganyika fauna,
establishing two new genera, one new subgenus and 47 new
species. Short papers by Vavra, Klie, Lowndes and others
also deal with the Recent ostracods of this general area.
Ramsay (1968) described three late Cretaceous species of
Cytherelloideafrom the Mikaramu Stream,Tanzania. Ayear
later, Bate {in Bate & Bayliss 1969) described22 newspecies
from Cretaceous sediments and later Bate (1975) described
52 species ofwhich 24were new, and four new genera, from
Fig. 1 MapofEastAfrica,showingthepositionofLindi. the MiddleJurassicsediments ofTanzania. The firstTertiary
species described from the Lindi area (sample FCRM 1648,
'alaeocene, which was disturbed by activation of the Lindi Upper Eocene) was Phalcocytherecf. spinosa Siddiqui, com-
auksystem duringOHgocene andearlyMiocene times. pared with P. spinosa Siddiqui 1971 from the Upper Eocene
ofPakistan. Theonly otherTertiaryostracod describedfrom
Tanzania, the Triebelinacf. howei(Stephenson, 1946)ofKeij
(1976), isfrom the mid-Oligocene sample FCRM 1576 and is
;tratigraphy here regarded as identical with T. howei from the Caribbean
region: see p. 191.
|Tie marine Cretaceous succession in the Lindi area consists
1 general of clay with subordinate sandstones and lime-
tones. There was no break in deposition between the SYSTEMATIC DESCRIPTIONS
Cetaceous and the Palaeocene but there was a change in
nvironment.
(a) Palaeocene. Outcrops of Palaeocene deposits are All type and figured specimens mentioned in this paper are
umerousbutsmallandfrequentlydisturbed. Atthebaselies depositedin thecollectionsofthePalaeontologyDepartment
rown sandy detrital limestone followed by a chain of reef- of the British Museum (Natural History); register number
noils, the lithology ofwhich varies considerably. Formation prefixOS. Referenceismadetoothermaterial heldattheBP
!f reef-knolls was followed by a series of silts, clays and Research Centre, Sunbury-on-Thames.
[npersistentthin limestones.
(b) UpperEocene. Sandyreeflimestoneswith interbedded SubclassOSTRACODA Latreille, 1806
Ilyers of soft marly clays lie at the base and are overlain by OrderPODOCOProA Miiller, 1894
indy reef limestones in a series of interbedded buff-grey SuborderPLATYCOPA Sars, 1866
lays, buff siltstones and thin, hard, sometimes siliceous, FamilyCYTHERELLmAE Sars, 1866
Jraminiferal limestones. The thickness is estimated to be Genus CYTHERELLA Jones, 1849
Imost70 m.
(c) OHgocene. Distribution of Oligocene deposits is limited,
5presenting a further stage in the early Tertiary regression, TypeSPECIES. Cytherinaovata Roemer, 1840.
he rocks are generally impersistent, being rubbly and silty
i;umfefsstioltnse.sT,hseofetstmiamraltyedlitmheisctkonneesss,isbuafbfo-ugtre8y0mma.rly clays and Cytherellalindiensissp. nov. PI. 1,figs4-9
(d) Lower Miocene. The early Lower Miocene is Name. Afterthe Lindi area, thetype localityinTanzania.
180 AHMAD,NEALE&SIDDIQUIij
9°50'-
5 km
Fig.2 GeologicalmapoftheLindiarea,Tanzania(afterKentetal., 1971).
ERTIARYOSTRACODAFROMTHELINDIAREA,TANZANIA 181
Fig.3 Samplelocationmap,Lindi,Tanzania. #approx. positiononly. FCRM 1963liesoffthesouth-eastcomerofthemap.
T Tr
,
182 AHMAD,NEALE&SIDDIQUl!
Diagnosis. A species of Cytherella with females egg-shaped Dimensions (nm). L H W
and males subovate in lateral view. Surface completely Holotype, female rightvalve OS 8025 550 370 170
smooth. Sexual dimorphism pronounced. Paratype, malecarapace OS 8027 710 415 275 1
Paratype, male rightvalve OS 8026 690 410 170
HOLOTYPE. A female right valve, OS 8025. Ten paratypes, Remarks. C. ovata (Roemer, 1840) and C. tumidosa\
OS 8026-35. Sample FCRM 2033, Lindi Creek, east shore; Alexander, 1934 are the closest in shape to C. lindiensis. €.]
UpperEocene. ovata differs in having the anterior and posterior margins;
Other material. 50 specimens, from FCRM 1711, 2033, tmhoeregreaartcehsetd;heCi.ghttumpoisdtoesraioisrltaorgtehretmhiadn-lCe.ngltihn.diensis, andhajsim
2034, 2045.
Description. Carapace medium-sized with greatest width Cytherellamediocairasp. nov. PI. 1,figs1-3
just behindthe mid-length andgreatest height in the anterior Name. Latin medio, middle -1- calvus, bald; with referenceto;
halfofthe valve. Sexual dimorphism pronounced; presumed the smooth central areaofthe valves.
femalesmore egg-shaped, malesmoreelongate. Dorsal margin
convex, ventral margin slightly concave. Anterior margin Diagnosis. Elongate, subquadrate in lateral view. Dorsal
broadlyrounded, posteriorcomparativelynarrowlyrounded. margin gently arched, ventral almost straight. Anterior
Rightvalve overlapsleft. External lateral surface smooth. symmetrically rounded, posterior rather narrowly rounded.
Internally, central muscle scars form a pinnate impression Carapace strongly pitted except for an inverted T-shaped
with 14 elongate scars in the anterior row and 10 in the smooth central area.
posterior; the axis slopes from dorsal to posteroventral in Holotype. A carapace, OS 7994. 10 paratypes, OS 7995-
females and is almost perpendicular to the length in males. 8004. Sample FCRM 1745, Mbanja River; LowerMiocene.
The scarsareatapproximatelymid-lengthinmales,posterior
tomid-length infemales. Other material. 28 specimens, from FCRM 1566 (e.g.
FEET METRES
0-r
Quaternary Raised reef linnestone
Unconformity
Rubbly sandy coral limestone (Mtanda Hill)
Pliocene ca.lOOft. Sands and mottled clays with Oyster Bed
/'Unconfornnity at base (Mikindani Beds)
II Massive mostly sandy reef limestone
I
100 Lower Miocene TT
(500ft. at west ' I
incMrtewaseersorabpuitdly ~1— Grey-buff clay with silty limestone and
siltstone increasing upwards.
to east)
500 I I
M ill
200 Grey-buff clay.
>Unconfornnity
I I I I I I I
lzl Rubbly silty limestones, calcareous
I I I I
Oligocene(290ft) siltstones and some clay.
—
I I I ~i rr
300 I I I I
I I ' I I ' I
1000 Thin hard limestones, clay and silt.
Upper Eocene I I I I I I
IIII II I I I
l~T~T Sandy reef limestone.
V I- I--I--I
400 Middle Eocene 'I'.'i ' i'l ' l Limestone often laterally impersistent,
and silt and silty marl.
Paleocene
I 1
—
(300
ft.) T
1500 -J
Fig.4 StratigraphicalsuccessionintheLindiarea(fromunpublishedBP-Shellreport, 1957).
'
ERTIARYOSTRACODAFROMTHELINDIAREA,TANZANIA ^ 183
37' 4r
100 Km 100 Km
I I "8"0 M /I 80 M 6-
'
^Dar-es-Salaam
Msangai^ Msanga«y
INDIAN
OCEAN
8- 8-
Present-day limit of
Marine Miocene
Palaeocene Possible former
Shoreline extent
Oligocene Marine Pliocene Mtwara
Shoreline Outcrop
end-Jurassic
peneplain
end-Miocene end-Cretaceous ? —
—
peneplain __ __ peneplain ^— —
^^Mt<r<a, \
Erosional history - uplift and peneplanation
>0)
ii>d_n; \i£c>Qn_n)n ticaiiCQ_nnn)D IOi£aic-n_n <i£d>_nn; 'EgaCc TiiCo>3nn "oC(_ iCLsioc-
(OQT)) OU(D.iif>n) qc(:U IC£0-_) -at0u-)j Dcc<Cbn (oc(JU i(nD q<:u oE
c c ^ au; U CQ) -?! g c c
Ou(U L-aDl 2-o^.^ _-oaMJ;I(oc-- Oog) a^oo.3u.o;.: —O0I) i£c_nn occ_ iD O 5<a^oc
J
lig.5 Tanzania,coastalregion, a,positionsofearlyTertiaryshorelines, b,distributionofNeogenerocks, c,geologicalhistoryofthearea.
(a,bfromKentetal, 1971;cfromKent,inBurke&Drake 1974.)
S 8005-17), 1746 (e.g. OS 8076-83), 1989 (e.g. OS 8024), Anterior margin symmetrically rounded, posterior compara-
110(e.g. OS8018-24). tively narrower but the carapace is thicker here than at the
anterior margin. Dorsal margin arched, passing smoothly
ESCRIPTION. Shell medium to thick; shape elongate, sub- into anterior and posterior margins; ventral margin almost
ladrate to subovate, with greatest height in the middle straight. Right valve larger than left and overlaps it all
id widest just behind the mid-length. Sexual dimorphism round. Surface ornamentation consists of circular pits con-
esent, presumed males being more elongate than females. centratedinanteriorandposteriorportionsandalongventral
|;
184 AHMAD, NEALE & SIDDIQUl:
KENT'SESTIMATE VALVE/CARAPACE posterior half. Anterior margin symmetrically rounded, pes-
10''YEARS1D0U'RYAETAIORNS c2m/140R^A6TYEEA8RS V1a0l0v-esRATCIaO—rpa-c1e0s0 ttehreiovrenntortalsomasrygmimne.trDiocrasla,lbmeairngginoblsitrqauieglhytiinnclainnteedritoorwaharldfs,'ii
then sloping down posteriorly. Ventral margin slightly con-
PLIO-
PLEISTOCENE cave. Rightvalveoverlapsleft,theoverlapbeingconspicuous
along mid-dorsal and mid-ventral borders. Externally a
UPPER
MIOCENE strong ridge runs along all margins. Two longitudinal ridges,
1
MIDDLE parallel to the dorsal and ventral margins, run from the|
MIOCENE posterior margin to just before the anterior end. Entire
surface finely reticulate.
LOWER
MIOCENE Dimensions (lam). L H W
Holotype, carapace OS 8088 500 280 160
OLIGOCENE Paratype, rightvalve OS 8089 540 300 105
Remarks. The two lateral ridges in C. gemellata are longer
than in any other Tanzanian Cytherelloidea species. How-
UPPER
EOCENE ever, the present species resembles Cytherelloidea sp. B, and
C
it is possible that gemellata is the male and Cytherelloidea
Figs.e6dimeAntcaotmipoanrriastoen. (ofEstthiemavtalevdeb/cyaKraepnatceetraalt.i,o1w9i7t1h.)the aspl.soBretsheembfleemsalCe.dainmdoerrspohniofanthdeCs.awmaeyesnpseicsi,esb.otCh dgeesmcerlilbaetda!^
by Sexton (1951); however, the upper ridge in C. andersoni'
margin. There is a smooth central area in the form of an bendCs at an obtuse anglejustbefore the mid-length, andthat
invertedT. of wayensis is concave, while the upper ridge of C.
Dimensions (jtm). L H W gemellata iscomparativelystraight.
Holotype, male carapace OS7994 835 515 360 Cytherelloideapatagiatasp. nov. PI. 2,figs1-4,
Remarks. C. mediocalva differs from C. cretensis Sissingh Name. 'Ornamentedwith a border'.
mql1au9ota7red2rerailacntoseinutsrstfpdhaioaccrenus.oaCulA.sllvsymioee,rdwaiitaoshnceedda.laivnnCta.enraovitnaodrnbdemteihannerbggosipllidnotiptoeeSfdiosoCfs.vieintrcgsrheipttisoesnsestmnietosrirorie-es tmDaiorawggainrnodasslitshr.eidAmgie.dsdpTleecw.ioeTsswohoforCtmyotrrhieedrgesehlsolrrotuidnreiafdrgwoeismthotrhaiengipnaoalstmteoesrftirooermntetinrhdee
dorsal margin isdifferent. dorsal margin; the anterior one runs more or less parallel to
the anterior margin and the median one runs obliquely'
towards the middle ofthe anterior margin. Left valve with a
Genus CYTHERELLOIDEA Alexander, 1929 distinct hinge tooth.
Holotype. A male left valve, OS 8085. Two female left
TYPESPECIES. Cythere williamsonianaJones, 1849. valves, OS8086-7, are paratypes. SampleFCRM2033,Lindi
Creek, eastshore; Upper Eocene. Noothermaterial.
Cytherelloideagemellatasp. nov. PI.2,figs9-10 Description. Leftvalve elongate, subrectangularwith great-
Name. 'Paired' or 'double', with reference to the pair of est height at anterior cardinal angle and greatest width near
longitudinal ridgeson the lateral surface. posterior end. Sexual dimorphism is extremely pronounced,
presumed females being swollen ventrolaterally, and males
A
Diagnosis. species of Cytherelloidea characterized by a being comparatively slender. Anterior margin symmetrically
strong marginal ridge and two longitudinal ridges running rounded; posterior rounded in the upper half but obliquely!
parallel to the dorsal andventral margins, from the posterior inclined towards ventral border in the lower half. Dorsal
margin tojust behindthe anteriormargin. margin concave anteriorly but uniformly convex from mid-
pHaorlaottyypep.e.NAocaortahpearcem,atOerSia8l0.88.SaAmprlieghtFvCalRveM,O2S03830,89L,inisdia lfievnegtehxtteornpaolstreirdigoers;entdh;e vleonntgreaslt,maargsitnroncgonvmeaxr.ginTahlerreidager,e
runs subperipherally along the anterior margin, becomes
Creek, eastshore; UpperEocene.
peripheral ventrally, is inflated posteriorly and is reduced,
Description. Carapace medium-sized, subrectangular, with along the dorsal margin. A short median ridge originates
greatest height behind anterior margin and greatest width in from the inflated posterior end, runs for about one-third of
PLATE
1
Figs 1-3 Cytherellamediocalvasp. nov. Holotype, malecarapace, OS7994; 1, lateralviewfrom left, x54;2, lateralviewfromright, x54;3,
dorsal view, x56.
Figs4-9 Cytherellalindiensissp. nov. Figs4-6,holotype,femalerightvalve, OS8025;4,musclescars, x350;5,externallateralview, x72;6,
internal lateralview, x69. Fig.7, paratype, malecarapace, OS8027, x66. Figs8,9,paratype, male rightvalve, OS8026;8,externallateral
view, x62;9, internallateral view, x64.
Figs10-12 ParanesideafracticorallicolaMaddocks, 1969. Rightvalve,OS8114; 10,external lateralview, x57; 11, musclescarpattern,
internallateralview, xl40; 12,internallateralview, x59.