A new species of Dizoniopsis (Prosobranchia, Cerithiopsidae) from the Gulf of Guinea Islands

2007·2.8 MB·English

by  Emilio Rolán

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©SociedadEspañoladeMalacología Iberus,25 (1):33-36,2007
A new species of Dizoniopsis (Prosobranchia,
Cerithiopsidae) from the GulfofGuinea Islands
UnanuevaespeciedeDizoniopsis(Prosobranchia, Cerithiopsidae) de
lasislas del Golfo de Guinea
EmilioROLAN*
Recibidoel8-1-2007.Aceptadoel19-11-2007
ABSTRACT
AnewspeciesofDizoniopsisfromPrincipe,SaoToméandAnnobonisdescribedshowing
differenceswithothersimilarspecies.
RESUMEN
Se describe una nueva especie de Dizoniopsisde las islas de Príncipe, SantoTomé y
Annobón, mostrandosusdiferenciasconotrasespeciesconocidas.
KEYWORDS:Dizoniopsis,Cerithiopsidae,GuiñeanGulf,SaoTomé,Annobon,newspecies.
PALABRAS CLAVE: Dizoniopsis, Cerithiopsidae, Golfo de Guinea, SantoTomé, Annobón, nueva
especie.
INTRODUCTION
TheCerithiopsidaeofWestÁfricaare Withreferencetotheislandsofthe
scarcely known, except for the genus GuiñeanGulf,FernandesandRolan
SeilaA.Adams,1861,revisedbyRolan (1993)foundintheliterature6ñamesof
andFernandes(1990)andRolanand CerithiopsidaementionedforSaoTomé:
Pelorce(2006). TOMLIN AND SHACKLEFORD (1914)
IntheliteratureregardingtheCape recorded 4 Mediterranean taxa: 3
Verde Islands, Rolan (2005) found 4 presentintheEuropeanfaunaandone
ñames of European species of whichisadubiouslyvalidñame;allof
Cerithiopsidae,butthesearesupposed them probably are not present in Sao
to be incorrect for the fauna of this Tomé; Tomlin (1928) described
archipelago. Among the 11 species Cerithiopsis thomensiswhich,according
treated in that work, only one had a to Fernandesand Rolan (1991), is a
ñame, being an endemic species Metaxia.
recently described (Rolan and Fer- Inthecollectingtripstotheislands
nandes,1989). oftheGuiñeanGulf,materialofaDizo-
Gofas, Pinto Afonso and niopsis with a paucispiral protoconch
Brandáo (1985) recognized 7 unde- was found. This is the subject of the
scribedspeciesforAngola. presentpaper.
*MuseodeHistoriaNatural,CampusUniversitarioSur,15782SantiagodeCompostela,Spain.
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Iberus,25 (1),2007
TAXONOMICPART
FamilyCerithiopsidaeH.AdamsandA.Adams,1853
GenusDizoniopsisSacco,1895
Typespecies:Dizoniopsisbilineata(Hórnes,1848)(lectotypefiguredinLandau,LaPernaand
Marquet(2006,textfigure1).
Remarks: Goodinformationonthis twospiralrowsperwhorl.Thischaracter
genuscanbefoundinLandauetal. ismentionedasalsoappearinginJocula-
(2006),althoughtheyemployedonlythe torHedley,1909andinHorologicaLaseron,
genusñameCerithiopsistodesígnateall 1956,whichcanbedifferentiatedbyother
thespeciesshown.Theseauthorsnever- characters.Duetoallofthis,weusethis
thelessmentionedsomereasonsthatal- genusñameforthespeciesheredescribed
lowustoacceptDizoniopsisasavalid whichisverysimilartothelectotypeof
genus,basedmainlyonthepresenceof thetypespeciesofthegenus.
Dizoniopsisapexclarusspec.nov.(Figs. 1-10)
Typematerial:Holotype(Fig.1)intheMNCN(15.05/47033).Paratypesinthefollowingcollec-
tions:AMNH(1s);BMNH(1s);MCZ(1s);MNHN(1s);USNM(1s);ZSM(1s);CJH(3s);CER
(10s,4j),allfromthetypelocality.Paratypesfromotherlocalities:SaoTomé:LagoaAzul:CER
C(2E1Rs,(1156jso,r50f).j)P.rincipeIsland:SantoAntonio:CER(3s,2j).AnnobonIsland:SanAntoniodePalé:
Othermaterialexamined(notdesignatedparatypesduetotheirerodedcondition):SaoTomé:
PraiaMutamba:25jand28f(CER);PraiaMariaEmilia:3j(CER);LagoaAzul:10s,4jand9f;
Principe:SantoAntonio:6f(CER).Annobon:SanAntoniodePalé:20s,11j,4f(CER).
Typelocality:SaoToméIsland,PraiaMutamba,3-10m.
Etymology:Thespecificñameisformedbythewords"apex"andtheLatinñameclarus"light"
alludingtotheprotoconch,whichislighterincolour.
Description: Shell (Figs. 1-3)conical Teleoconch with up to 8 whorls
elongate,solid.Protoconchslightlyvari- (adultsapparentlyhavefrom5whorls
able(Figs.4-10)with2oralittleover2 up), with two spiral cords per whorl,
whorls,withadiameterofbetween250- crossed by axial ribs which form
300umandanucleusbetween90and nodulesontheintersections.Thelower
127 um; the microsculpture of the cordbeginsasacontinuationfromthe
nucleusbeginswithfewspiralthreads, cordoftheprotoconch. Theotherone,
whichcontinuéforashortdistance(less in an adapical subsutural position,
thanonewhorl);then, one spiralcord appears very cióse to the suture from
appears in the middle of the whorl, thebeginning,beingsmallerinthefirst
sometimesnarrow,sometimeswiderin whorl.Insubsequentwhorls,bothcords
someshells;atthesametime,curved, are equal in width and size of the
axial,almostorthoclineribs(exception- nodules, but from the fourth whorl
allyopisthocline)appearontheupper downwards,theupperoneislarger,and
part ofthe whorl. These ribs are very thenodulesmoreelongateaxially,being
variableinnumber,between8and15in on the last whorl clearly larger than
half a whorl. In the lower part of the thoseonthelowerportion. Inthelast
first whorl, below the spiral cord, whorl, there are three more cords
severalnodulousirregularfinethreads towards the base, narrower than the
arepresent, in the second whorl axial previous ones and scarcely nodulose,
oblique ribs appear. Thecolour ofthe except the uppermost one. Aperture
protoconchiswhite. ovoid,almostsubquadrangular,dueto
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ROLAN:AnewspeciesofDizoniopsisfromtheGulfofGuineaíslands
Figures 1-10.Dizoniopsisapexclarus. 1: holotype,3.0mm, PraiaMutamba, 5m(MNCN);2,3:
paratypes,SanAntoniodePalé,Annobon,2.9,2.2mm(CER);4-6:protoconchofparatypes,Sao
Tomé(CER);7-10:protoconchofparatypes,Annobon(CER)(allprotoconchsatsamemagnifica-
tion).
Figuras1-10. Dizoniopsisapexclarus. 1:holotipo,3.0mm, PraiaMutamba, 5m (MNCN);2,3:
paratipos, SanAntoniodePalé,Annobon,2.9,2.2mm(CER);4-6:protoconchasdeparatipos,Santo
Tomé(CER);7-10:protoconchasdeparatipos,Annobon(CER)(todaslasprotoconchasconlamisma
ampliación).
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Iberusy25 (1),2007
thecolumellabeingstraight; thereisa usuallynarrower.However,thesediffer-
visiblecolumellarcallousandapointed encescouldnotindicateacompletespe-
profile of the aperture in the upper cificdifferentiationandweprefertokeep
externalpart.Peristomanarrow,slightly bothpopulationsasbeingconspecific.
undulatingtowardstheendofthespiral ThemostsimilarspeciesisDizoniop-
cords.Siphonalcanalopenandshort. sis bilineata (Hoernes, 1848). Thelecto-
Thecolouroftheshellisdarkbrown typeofthisspecieshasabrokenproto-
in live collected shells, lighter in first conch,butitcanbeseenthatithasaxial
whorlsoftheteleoconch.Oídshellsare and spiral sculpture, being probably
light brown or yellowish. The brown multispiral.TheshellfiguredasD.bilin-
colour is not uniform being usually eatainGiannuzzi-Savellietal. (1999,
darkerontheuppercord,inthespaces fig. 76),hasashortprotoconchwiththe
betweenthenodulesandonthebase. firstwhorlwiderandtwocordsonthe
Dimensions: holotype is 5.6 mm; secondwhorl;thesecharactersaredif-
someparatypesmayreach7mm. ferentfromtheprotoconchofthelecto-
Distribution: Collected in three type, and probably correspond to an
islandsoftheGuiñeanGulf(Principe, undescribedMediterraneanspecies.
Sao Tomé and Annobon) where this D. coppolae(Aradas, 1870),fromthe
speciesispresumablyendemic. Mediterranean,hasalargershell,with
Remarks:Wehavefoundsomediffer- creamcolour.
ences between the protoconch of the D.herbertiJayandDrivas,2001,from
shellsfromSaoToméandthosefromAn- Reunión Island, is smaller and totally
nobon:thosefromSaoTomé(Figs.4-6) white;D. herosaeJayandDrivas,2001,
arealittlemoresharplypointed,theaxial fromthesamelocality,isalsoofwhite
sculpture is formed by narrower and colour,bothbeingendemicfromavery
morenumerous ribs; the spiralcord is distantregión.
ACKNOWNLEDGEMENTS
To Jesús Méndez for the SEM pho- a la Investigación (CACTI) of the
tographs of this species made in the UniversityofVigo.AntonioA.Monteiro
CentrodeApoyoCientíficoyTecnológico madecorrectionstotheEnglishlanguage.
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