DoesthemiddleEoceneRíoPichileufú florafromPatagonia,Argentina record
initialfloristicresponsetoglobalcoolingandSouthAmericanIsolation?
ClaireCleveland
DepartmentofGeosciences,PennsylvaniaStateUniversity,UniversityPark,PA16802
[email protected]
Introduction
SampleofLeafDiversity
SouthernHemispherefossilplantsindicatearainforestbiomeacrossmuchofLateCretaceous
andEarlyPaleogeneGondwana,butglobalcoolingandseparationofSouthAmericaand
AustraliafromAntarcticaarelinkedtosignificantecologicalchangeinthemiddleEocene
throughtheOligocene.TheRíoPichileufú fossilflora(RP)fromRíoNegroProvince,Argentina
(Fig.1)offersanexceptionalopportunitytoobservetheearliestsignalsofecologicalchange
inmiddleEocenePatagonia.TheprincipalrecordofPatagonianfossilplantsduringtheEarly
EoceneClimaticOptimum(EECO)istheLagunadelHunco fossilflora(LH)inChubutProvince,
Argentinadated52.22(±0.22)Ma(Wilf,2012).RPisdatedca.3MaaftertheEECOat47.74
±0.05Ma(Wilf2012),duringtheveryfirststagesofcoolingandseparationofSouthAmerica
fromAntarctica(Fig2).Althoughthe1938E.W.BerryRPmonographstillrepresentsthemost
diversedescribedCenozoicfossilflorafromSouthAmerica,itprovidesonlyaqualitative
accountoftheassemblageandjustafractionofitsspecimenshavereceivedmodern
paleobotanical treatment.AcomprehensiveupdateoftheRPassemblagecombinedwith
quantitativedatafromrecentunbiasedcollectionswillprovidethedataneededtocompareRP
withLHandtestforsignalsoffloralresponsetocoolinginPatagoniaandSouthAmerican
biogeographicisolation.
Objectives
Toprepareforquantitativetestsofpaleofloral responsetocoolingandbiogeographicchange,I
beginwithanupdateoftheRPflora.RPdiversitywillbeestimatedusingmorphotypes and
systematiccomparisonswithtypematerialtoimproveourunderstandingoffloralcomposition.
Figure5.Asamplingoffloral
diversityandpreliminary
identificationsfromtheRío
Pichileufú collections
(Preliminaryidentification,
Morphotype No.,SpecimenNo.).
A. Retrophyllum sp.,RI097,
BAR_4705
B. Unidentified,RI086,
BAR_4595
C. Unidentified,RI039,
RP3_0827
D. Unidentified,RI073,
BAR_4639
E. Cochlospermum previtifolium
Berry,RI071,RP3_0942
F. Unidentified,RI071,
RP3_0942
G. “Banera”prehernandiensis
Berry, RI082,BAR_4622
H. “Villaresia”congonhifolia
Berry,RI080,RP3_1111
I. “Nectandra”prolifica Berry,
RI048,BAR_4450
J. Myrtaceae,RI012,BAR_4356
K. Myrtaceae with
infructescences attached,
RI087,BAR_4706
L. Fabaceae,RI052,RP3_0739
B
• 400+RPspecimensfromtheEWBerry1938TypeandCohort
collectionattheSmithsonianNationalMuseumofNatural
History
Figure1.RíoPichileufú
andLagunadelHunco
locationsmappedonto50
Mapositionsofmodern
coastline.Figureadapted
fromWilfetal.,2005.
C
D
Río Pichileufú
(47.74±0.05Ma)
Laguna del Hunco
(52.22±0.22Ma)
• Allcollectionsquarriedfromtuffaceous caldera-lake
sedimentsofHuitrera Formationindicatingsimilar
paleoenvironments
RíoPichileufú LeafDatabase
E
Figure2.Siteagesplacedon
globaldeep-seaoxygenisotope
recordsadaptedfromZachos et
al.,2001.
Specimens
F
H
I
LeafArchitecture
F
Berry(1938)originallyassignedtheRPfloratoaMioceneageand
highlighteditsaffinitiestobothextantSouthAmericanandAustralasian
floras.Incontrast,recent40Ar/39Ardatesshowthatthefloraisearliest
middleEocene(Wilf,2012),andsystematicrevisionsofangiospermsand
conifers(Fig.4)havegreatlystrengthenedAustralasianlinks.Severalof
theconifertaxa,suchasPapuacedrus andDacrycarpus,provideevidence
supportingahumidandeverwet environmentwithlinkstoextantWest
Pacificmontaneforests(Wilfetal.,2009;Wilf,2012).Theflowerofbasal
Asteraceae Raiguenrayun cura fromanotherRíoPichileufú locality
(Barreda etal.,2010;Barreda etal.,2012)representsa
paleobiogeographic linkbetweenSouthAmericaandAfrica(Bandoni De
Oliveiraetal.,2009).Insightsfromawell-developedunderstandingofRP
anditscomparisonwithLHwillbeusedtoinvestigatetransitionfrom
AncientGondwanantoextant-SouthAmericanaffinitiesandtestthe
proposedpaleogeographic explanations.
Figure4.SomeRíoPichileufú taxathathavebeenrevisedsinceBerry’s1938monograph.A.Acmopyle engelhardti (Berry)Florin1940;
specimenRP3_1068.B.Papuacedrus prechilensis (Berry)Wilfetal.2009;specimenBAR-4742a. C.Dacrycarpus puertae Wilf2012;USNM.
40381. D.Agathis zamunerae Wilf2014;USNM-40378.E. Atherospermophyllum guinazui (Berry)CLKnight2013;USNM-40403.
F.Ginkgoites patagonicus Villar deSeoane etal.2015;specimenRP3_1112.
.
PreviousworkindicatesthatalthoughmanyplanttaxaarefoundatbothRPandLH,including
gymnospermssuchasDacrycarpus andAgathis,RPlackstaxaabundantatLH,including
angiospermsEucalyptus andGymnostoma.Also,taxaobservedatRParenotrepresentedatLH,
includingAsteraceae flowers(Barreda etal.,2012).Thisworkwillprovidethefoundationfora
comprehensiveupdateofBerry’sRPmonographandquantitativecomparisonoftheRPandLH
assemblagesinthecontextofglobalcoolingandSouthAmericanbiogeographicisolation.I
predictnetlossofancientGondwananrainforestassociationsandnetgainofcladeswith
affinitiestoextantSouthAmericaflorasaswellasshiftsinrelativeabundance.
LiteratureCited
Figure3.Aprojectdatabase,developedusingFileMakerPro
Advancedv.14.0.4,organizesleafdatainarelationalframeworkand
generatesautomateddescriptionstoassistmanuscriptpreparation.
TerminologyfromtheManualofLeafArchitecture,2009(Ellisetal.,
2009)isusedtoensureconsistenttraitcomparisons.
L
Discussion
Images
Morphotypes
K
J
G
FloralChangeinEocenePatagonia
A
• 4300+LHspecimensintherecentlypublishedcollectionat
theMuseo Paleontológico Egidio Feruglio (Trelew,Argentina)
D
C
E
A
Materials
• 1200+RPspecimensfromtheunbiased2002and2005
collectionsattheMuseo Paleontólogico Bariloche (Bariloche,
Argentina)
B
Bandoni deOliveiraF, CassolaME,Marroig G(2009).In:GarberPA,EstradaA,Bicca-MarquesCJ,
Heyman EW,Strier KBeds.NewYork:SpringerScience,55-68.
Barreda VD,Palazzesi L,Katinas L,Crisci JV,Telleria MC,etal.(2012).AnnalsofBotany109:127134.
BerryEW(1938).GeologicalSocietyofAmericaSpecialPapers12:1-140.
EllisB,DalyDC,HickeyLJ,JohnsonKR,MitchellJD,etal.(2009).ManualofLeafArchitecture.
CornellUniversityPress,Ithaca,NewYork216pp.
FlorinR (1940).Svensk Botanisk Tidskrift 34:117-140.
KnightCL andWilfP(2013).Palaeontologia Electronica16:29A-39.
Villar deSeoane L,Cúneo NR,Escapa I,WilfP,GandolfoMA(2015).InternationalJournalofPlant
Sciences176:346-363.
WilfP,JohnsonKR,Cúneo NR,SmithME,SingerBS,GandolfoMA(2005).AmericanNaturalist
165:634-650.
WilfP,LittleSA,IglesiasA,DelCarmenZamaloa M,GandolfoMA,etal.(2009).AmericanJournal
ofBotany96:2031-2047.
WilfP (2012).AmericanJournalofBotany99:562-584.
WilfP,Escapa IH,Cúneo NR,Kooyman RM,JohnsonKR,IglesiasA(2014).AmericanJournalof
Botany101:156-179.
Zachos JC,DickensGR,Zeebe RE(2008).Nature451:279-283.
Acknowledgements
FundingprovidedbytheNationalScienceFoundation(NSF
DEB-1556666andGraduateResearchFellowshipProgram),
theEvolvingEarthFoundation,theGeologicalSocietyof
America,ThePaleontologicalSociety,andthePaulD.Krynine
MemorialFund,PennStateGeosciences.Manythanksfor
accesstothecollections,labspace,andabundanttechnical
supportprovidedbytheMuseo Paleontólogico Egidio
Feruglio (MEF)andMuseo Paleontólogico Bariloche (BAR).
MysincereappreciationtoAnnaWhitakerforherassistance
attheMEFandforAaronCleveland’sassistancewith
photography.Thisworkwouldnotbepossiblewithoutthe
supportofmyadvisor,PeterWilf.