PHARUS PRIMUNCINATUS (POACAE: PHAROIDEAE: PHAREAE) FROM DOMINICAN AMBER

2005·3.1 MB·English

by  George Poinar

PHARUSPRIMUNCINATUS(POACAE:PHAROIDEAE:
PHAREAE)FROMDOMINICANAMBER
GeorgePoinarJr. EmmetJ.Judziewicz
DepartmentofZoology DepartnnentofBiology
OregonStateUniversity UniversityofWisconsin-StevensPoint
Corvallts,Oregon97331U.S.A. StevensPoint,Wisconsin54481,U.S.A.
[email protected] [email protected]
ABSTRACT
AgrassspikeletwithacylindricaKsigmoidal,uncinatetloretinDominicanamberisdescribedas
thenewspeciesPharusprimuncinatusJudz.&Poinar(Poaceae:Pharoideae:Phareae).Thefossilcan
bedistinguishedfromallextantmembersofthegenusbythesmallC-).*-)mmlong),curvedfemale
floret;relativelyshortglumes;andtheuncinateportionofthefloretextendingdownwardstothe
middleorslightlybelowthemiddleofthelemma.TheclosestextantrelativemaybetheMesoameri-
canP.mczii.Thisistheearliestrecordofafossilgrassthatcanbeassignedtoanextantgenus;the
earliestrecordolamemberoithebasalsubfamilyPharoideae:andtheonlyknownfossilPharus
spikelet.
Khywords:fossilgrass,Pharus,P.lalijolius.P.mezu,Ppriinuncinalus,Poaceae,Pharoideae,Phareae,
Dominicanamber
RESUMHN
ef:snpebcaisee,aPuhnaaruesspipgruiimlluancfoisnialtcuosnJuundz[.lo&scuPlooicnialrin(dProiacco,easei:gmPohiardoeiydeuanec:inPahadroeasee)d,esdcerlibaemubnaarnduee\'laa
RepublicaDominicana.Sedilerenciadetodaslasespcciesdelgenerocxistentesporsuespiguilla
pistiladapequena(9.9mmdelargo);1losculopistiladocurvado;glumasrelativamentecortas;yla
porcionuncinadadellemaextendidadelamitadhastaelapice.Laespcciccxistentemasrelacionada
esposiblementeP.meziideAmericaCentral.Esteeselregistromasantiguodeunagramincafosil
quepuedeasignarseaungeneroexistente;elregistromasantiguodelmiembrodelasublamilia
Pharoideae;yelimicofosildeunaespiguilladePharus.
INTRODUCTION
Grassfossilsarerare.Thosethathavebeenreportedmostlyoccurinsedimen-
tarydepositsandtheiridentificationatthegenericlevelisproblematic.How-
ever,amberhasremarkablepreservativequalitiesforbothplantandanimalfos-
sils(Poinar1992)andanumberofangiospermremainsidentifiabletoextant
generaoccurinDominicanRepublicamber(Poinar&Poinar1999).Domini-
canamberoriginatedfromresinoftheextincttree,HymenaeaproteraPoinar
(Legummosae:Caesalpinioideae)thatthrivedsome20-40millionyearsagoin
Hispaniola(Poinar1991;Poinar&Poinar1999).Oneespeciallyinterestingfos-
silinthisamberwasaspikeletbelongingtothegrassgenusPharusP.Browne
whichwasassociatedwithmammalianhair(Poinar&Columbus1992).
SIDA21(4):2095-2103.2005
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PharuswaslongplacedintheBambusoideae(Judziewicz1987;Watson&r
Dallwitz1992),butrecentmolecularevidenceindicatesthatitismuchmore
basalthanthebamboosandindeedisthesecondearliest-divergingbasalclade
inthePoaceae(Clark&Judziewicz1996;Judziewiczetal.1999;GrassPhylog-
enyWorknigGroup2001).
Daghlian(1981)consideredatleast11reportedmacrok^ssilsastruefossil
grassesbutcautionedagainstassigningfossilpollengrainstothePoaceaesince
othermembersol the Poaleshavesimdar pollen types, hi hisreviewof
paleoagrostology,Thomasson(1987)hsted11publishedreportsoffossilgrasses,
butdeterminedonlythreeol thesetobeundoubtedrepresentativesofthe
Poaceae.Whiletheoldest-knownunequivocalfossilgrassisIromthePaleocene/
EoceneboundaryinTennessee(Crepet&Feldman1991),bambusoid-likemono-
cotsextendbackintotheEarlyCretaceous(Poinar2004),thustheoriginofthe
tamilymaybequiteancient.ThepresentstudydescribesthefossilfemalePharus
spikeletreportedearlier(Poinar&Columbus1992).
MATFRIAI.SANDMF.THODS
Thesmalltriangularpieceol amber(7gm,37mmlongestlength x25mm
longestwidth,15mmthick)containingthefossilcameIromLaTocamine,situ-
atedbetweenSantiagoandPuertoPlataintheCordilleraSeptentrionalolthe
northernportionol theDominicanRepublic.DatingofDominicanamberis
stillcontroversialwiththelatestproposedageof20-15myabasedonforamin-
ifera(Iturralde-Vinent&MacPhee1996)andtheearliestas45-30myabased
oncoccoliths(CepekinSchlee1999).ArangeofageslorDominicanambermay
belikelysincetheamberfossilsareassociatedwithturbiditicsandstonesol
theUpperEocenetoLowerMioceneMameyGroup(Draperctal.1994).Domini-
canamberissecondarilydepositedinsedimentaryrocks,whichmakesadeli-
nitcagedeterminationdilticult(Poinar&Mastalcrz2000).Observationsand
photographsweremadewithaNikonstereoscopicmicroscopeSMZ-10Rand
NikonOptiphotTMatmagnificationsupto600x.
RF.SULTS
Thelollowmgcharactersol thefossilplaceitinthegenusPhu)us:Asingle-
floweredfemalespikeletwithrelativelyshort,glabrousglumesandaninrolled,
cylindrical, tapering,7-nerved lemmacovered with uncinate(hooked)
macrohairs.
OrderPoales,FamilyPoaceae,SubfamilyPharoideae(StapQL.G.Clark&Judz.,
TribePhareaeStapf
PharusprimuncinatusJudz.&Poinar,sp.nov.(Figs. 1-3).Tm'h:DOMINICANRH-
I\'BL1C:LaTocaamberiniiu-locaiedbetweenSantiagoandPuertoI'lataintheCordillera
SeptentrionalolthemirthcrnportionottheOominicanRepublic.Aiemale.spikeletdepos-
POINARANDJUDZIEWICZ,PHARUSPRIMUNCINATUS,ANEWGRASSSPECIESINDOMINICANAMBER 2097
r
ii 1
Fig.1.SpikeletofPharusprimuncinatusinDominicanamber.Bar=860(im.
2098 BRIT.ORG/SIDA21(4)
Figs.2-S.PharusprimuncinatusinDominicanamber(elongatestrandsinallphotosaresegmentsofmammalianhair).
2.Tipoflemmashowingbeardedportion(delineatedwitharrows)coveredwithuncinatemacrohairs.Bar=36|.im.3.
Upperportionoflemmashowingrangeinsizeofuncinatemacrohairs.Bar=278|nm.4.Lowerportionoflemmaand
twoglumes(arrows).Notepapillosesurfaceoflemma.Bar=450j^im.5.Detailofuncinatemacrohairs.Noteonestrand
ofmammalianhair(arrow)enclosedbytheplantmacrohairs.Bar=56|.im.
POINARANDJUOZIEWICZ,PHARUSPRIMUNCINATUS,ANEWGRASSSPECIESINDOMINICANAMBER 2099
itedmtheGeorgePomarambercollection(accession#M-1-4)maintainedatOregonState
University,Corvallis,OR97331,
Fossilfemalespikelet9.9mmlong(withoutpedicel)and2.3mmwidesub-
tendedbyashortpedicel(0.93mmlong),consistingoftwoglumesandasingle
floret.Firstglume5.2mmlong;secondglume3.3mmlong(thetipbentback
andcouldhavebeendamaged,thusitmayhavebeenlonger);lemmaapproxi-
matelytwicethelengthoftheglumes,somewhatsigmoid,taperedapicallyinto
abeak,7-nerved,withstronglyinroUedmargins;withadiscretearea,begin-
ningapproximately2/5fromthebaseofthelemmaandextendingalltheway
tothetip,denselycoveredwithuncinatemacrohairs,thehairsextendingfrom
thetip1/3ofthelengthofthelemmaontheventralside(3.5mmfromapex),
butoverhalfthelengthofthelemma(5.4mmfromtheapex)onthedorsal
side;macrohairs0.22-0.56mminlength;basalportionofthelemmacovered
withnumeroussmallpapillae(Fig.4).
Currently,sevenextantspeciesofVharusarerecognized;theyrangefrom
MexicoandFloridatoArgentinaandUruguay.Usingthekeysprovidedby
Judziewicz(1987,1991),thefossilfallsintoagroupofthreespecieswithcurved
tosigmoidfemalelemmas:PlatijoliusL.,P.meziiProdoehl,andP.\iitatusLem.
Pharusvittatushasfemalelemmas19-26mmlong,muchlongerthanthoseof
thefossil,whichhasamaturelemma9.9mmlong.TheextantspeciesPlatijolius
athnedfPlomreetzi(9i.9(Tmabmlel1o,nFgiga.n6d)h2.a3vemsmmawlliedre)feamnadlefirssptikgelluetmset(h5a.2nmPmvitltoantgus),obfuPt
primuncinatusaresignificantlyshorteryetwiderthanthoseofPlatijolius[flo-
rets(12-)13-17('-19)mmlong,1-2.3mmwide,firstglume9-13mmlonglandP.
mezii[florets10.5-13.5mmlong,0.9-T8mmwide,firstglume5.3-7.3(-8)mm
long].Also,thefemalefloretofthefossilisbeardedwithuncinatemacrohairs
overthemajorityofitsexposed(i.e.,notcoveredbytheglumes)surface,while
inP.latijoliusandPmeziithebeardisrestrictedtotheapexofthefloret(Fig.6).
Etymology—ThespecificepithetprimuncinatusisfromtheLatin"firstunci-
nateone,"alludingtothefirstfossilrecordofhookedmacrohairsonaspikelet.
DISCUSSION
Presently,fourspeciesofPharusoccurmHispaniola,includingP.lappulaceus
Aubl,Platijolius,P.parvijoliusNash,andPvirescensDoell.Pharusmezii,per-
hapstheclosestrelativeofthefossilspecies,isaMesoamericanandnorthern
SouthAmericanspeciesofseasonallydryforests.Themorphologicalevidence
doesnotexcludethepossibilitythatP.primuncinatusisdirectlyancestralto
bothPlatijoliusandPmezii.
Themannerbywhichthefemalespikeletarrivedmamberhasalready
beencitedasthefirstexampleofepizoochoryinthefossilrecord(Poinar&
Columbus1992).Thisconditionisobviousfromthenumberofmammalian
hairsassociatedwiththespikelet,oneofwhichisstillattachedtothelemma
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Table1.ComparisonofPharusprimunnnatustotwocloselyrelatedspecies.
Pharuslatifoliui Pharusprimuncinatusspnov. Pharusmezii
Distribution Widespreadinwet Fossil(EocenetoMiocene) Seasonallydryforests,
forestsinthe fromHispaniola mostlyalongthe
Neotropics,including Pacificcoastfrom
Hispaniola MexicotoPanama;
rareindryforestsof
Colombia,Venezuela,
andEcuador;notin
theWestIndies
Femalefloret (12-)13-17(-19) 9.9 10.5-13.5
length(mm)
Femalefloret 1-2.3 2.3 0.9-1.8
width(mm)
Femalefloret: 7.5-12 4,3 7.5-10
Length/width
ratio
Femalefirstglume 9-13 5.2 5.3-7.3(-8.0)
length(mm)
Femalefirstglume: 0.6-0.8(-0,9) ca.0.5 0.5-0.6
Femalefloret
ratio
Distributionof Restrictedto Foundovermostofthe Restrictedtoapical
uncinatehairs apical10-20%; exposedsurface 15-25%;
onthefemale rarelysparsehairs (33-60%) rarelysparsehairs
elsewhere
bytheuncinatemacrohairs(Fig.5).Thesehairswereidentifiedasrlieguard
hairsofacarnivore(Poinar&rColumbus1992).
Thereiscircumstantialevidencethatmanyspeciesofmammalsdisperse
theadhesivefemalefloretsofPharusspecies,asattestedbysuchlocalcommon
namesofP.latifoliusandPlappulaceus(Judziewicz1987:296-297,387-388)as
1rutadeperro"Ifruitofthedog](Cuba),"rizchien''Idogrice](FrenchGuiana),
"alcusa"[doginQuichua](Ecuador),"barbadepuma"and"barbadetigre"[beard
ofthejaguar](Peru),"yagua-arrozIjaguarnee](Paraguay),"barbadepaca"]beard
ofthepaca,alargerodent](Brazil),and"barbademacuco"[loeardofthemon-
key](severalBraziliancollections).Thegenusmayapparentlybedispersedby
birdsaswell;commonnamesinclude"pegapolio"Istick-to-the-chicken](Do-
minicanRepubhc),andherbariumspecimenswithfeathersadheringtothe
inflorescencehavebeenobserved.
Thepresentreportistheearliestrecordofafossilgrassthatcanbeassigned
toanextantgenus,theearliestundoubtedrecordofamemberofthebasalsub-
familyPharoideaeandtribePhareae,andtheonlydescribedfossilspikeletofa
memberol thePharoideae.In1986,thesecondauthoralsoexaminedaplastic
POINARANDJUDZIEWICZ,PHARUSPRIMUNCINATUS,ANEWGRASSSPECIESINDOMINICANAMBER 2101
mm
10
FiG.6.SpikeletpairsoftheextantspeciesPharuslatifolius(left)andP.mezii(right).Thepistillatespikeletsarelargeand
curvedandthestaminatespikeletssmallandpedicellate.IllustrationbyJudziewicz.
t
2102 BRIT.ORG/SiDA21(4)
castotaleafbladeofanundoubtedlypharoidgrass(.presumablyLcptaspisR.
Br.,sistergenusofPharus),frommid-Miocene(12millionyearsold)volcanic
ashnorthwestofLakeBarmgo,Kenya(ca.1°N,36°E)kindlyprovidedbyChris-
tineKabuyeandBonnieF.Jacobs;aduplicatecastisondepositattheUniver-
sityofWisconsin-Madisonherbarium(Judziewicz1987;Clark&Judziev^acz
1996).
ACKNOWLF.DGMHNTS
Theauthorsthankj.TravisColumbusfororiginallyidentifyingthefossilgrass
andlendingassistancetothisstudy,andthankhimandLynnG.Clarkfortheir
helpiulreviews.
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