Plate Motions, Gondwana Dinosaurs, Noah's Arks, Beached Viking Funeral Ships, Ghost Ships ...

20 Pages·2011·1.08 MB·English

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AnaisdaAcademiaBrasileiradeCiências(2011)83(1):3-22
(AnnalsoftheBrazilianAcademyofSciences)
PrintedversionISSN0001-3765/OnlineversionISSN1678-2690
www.scielo.br/aabc
Plate Motions, Gondwana Dinosaurs, Noah’s Arks,
Beached Viking Funeral Ships, Ghost Ships, and Landspans
LOUIS L. JACOBS1, CHRISTOPHER STRGANAC1 and CHRISTOPHER SCOTESE2
1RoyMHuffingtonDepartmentofEarthSciences,SouthernMethodistUniversity,Dallas,TX,75275,USA
2DepartmentofGeology,UniversityofTexasatArlington,Arlington,TX,76019,USA
ManuscriptreceivedonNovember10,2009;acceptedforpublicationonAugust16,2010
ABSTRACT
Gondwanalandmasseshaveservedaslarge-scalebiogeographicNoah’sArksandBeachedVikingFuneralShips,as
definedbyMcKenna. ThelatitudinaltrajectoriesofselectedGondwanadinosaurlocalitiesweretracedthroughtime
in order to evaluate their movement through climate zones relative to those in which they originally formed. The
dispersal of fauna during the breakup of Gondwana may have been facilitated by the presence of offshelf islands
forminglandspans(sensuIturralde-VinentandMacPhee)intheEquatorialAtlanticGatewayandelsewhere.
Keywords: biogeography,dinosaur,Gondwana,latitude.
INTRODUCTION Ark as a segment of continental crust with its biota,
riftedandmovedawayfromitscontinentoforigin. He
In 1973 Malcolm C. McKenna published a paper
viewedNoah’sArksaspermittingone-waydispersalof
titled, “Sweepstakes, Filters, Corridors, Noah’s Arks,
a balanced biota during which “the transported biota
andBeachedVikingFuneralShipsinPalaeogeography”.
would evolve, and latitudinal components of motion
His purpose was to reconcile the biogeographic princi-
wouldconceivablyaffectavailableecospaceviatheef-
ples elaborated by William Diller Matthew (e.g. Mat-
fects of climatic change” (McKenna 1973, p. 302). In
thew 1915, 1939) and George Gaylord Simpson (e.g.
the same paper, McKenna also defined biogeographic
Simpson1940,1943,1946,1947a,b,1952,1953),devel-
Viking Funeral Ships as continental crust rifted away
opedunderastableEarthperspective,withthethenwell
fromonelandmassandtravelledtoanadjacentlandmass,
accepted framework of plate tectonics. His fundamen-
carrying fossils from the first area, where the popula-
talconclusionwasthatthedispersalistprincipleselabo-
tionshadlived,tothesecondareawhereaFuneralShip
ratedbyMatthewandSimpsonwerestillrelevantwith-
beachedandwherethefossilbiotahadneverlived. The
incertainmobilistcaveats: sweepstakesroutesarethose
formationofNoah’sArksandVikingFuneralShipsare
in which odds of dispersal success are low, as in true
features of divergent plate boundaries. Docked Noah’s
rafting; filters are those which allowed the dispersal of
Arks and Beached Viking Funeral Ships are features
some but not other species, usually due to the adapta-
of convergent plate boundaries and accreted terranes.
tionsofthespeciesinvolvedandtheenvironmentalcon-
Their effects on historical biogeography occur on the
ditions of the route; and corridors are those in which
spatial and temporal scales at which lithospheric plates
movementwasthemostfreeofall.
arecreated,subsumed,andmoveabout.
McKenna (1973) defined a biogeographic Noah’s
McKenna (1983) added more mobilist biogeo-
ProceedingsoftheThirdGondwananDinosaurSymposium graphic concepts derived from his plate tectonics per-
Correspondenceto:LouisL.Jacobs
spective. One was “Escalator Counterflow”, which en-
E-mail:[email protected]
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4 LOUIS L. JACOBS, CHRISTOPHER STRGANAC and CHRISTOPHER SCOTESE
visioned a rejuvenating volcanic pile at a spreading ever, if the concept of landspans is expanded to allow
center without appreciable geographic displacement of subaerialconnectionpunctuatedbyshortwatergapsbe-
theislandscreated,inwhichterrestrialorganismsessen- tweenoff-shelfislands(i.e.,thosedevelopedonoceanic
tially moved “up the down escalator” through geologic crust) and two adjacent continents, then the concept of
time. Anotherwas“HopscotchontheEscalator”result- landspans becomes relevant when considering the dis-
ing from colonization of progressively younger islands persal of Gondwana dinosaurs, and elaborates the mo-
along a hotspot trace, as exemplified by the Hawaiian bilistconceptspresagedbyMcKenna.
Islands and Emperor Seamounts. The older islands Wehavetwopurposesinthispaper. Thefirstisto
move with the plate away from the hotspot, erode, and tracethelatitudinaldriftofselectedGondwanadinosaur
subsidebelowsealevel. Thebiotaskipsfromtheolder localities (Fig. 1, Table I) through time from the Trias-
eroding and subsiding island to newly formed islands sic (220 Ma, Carnian), when continents were united in
attheintraplatehotspot. SomeoftheplantsofIceland, Pangea,untilthepresentday. Thisisusefulforcompar-
which have a fossil record going back to the Miocene ing where fossil localities were formed to where they
origin of the islands (Grímsson et al. 2007), provide a are now in terms of the climate zones they traversed
possible example of Escalator Counterflow. The Gala- because,torepeatagainMcKenna’swords,“latitudinal
pagosbiota(Christieetal.1992,Grehan2001)ispossi- components of motion would conceivably affect avail-
blyanexampleofHopskotchontheEscalator. Another ableecospaceviatheeffectsofclimaticchange”. Gen-
example might be living coelacanths on the slopes of eral Circulation Models (GCMs) consistently indicate
underwater volcanoes near the Comoro Islands (Fricke high global temperatures and low latitudinal tempera-
and Hissman 1990). The volcanos formed much later turegradientsduringtheMesozoic(SellwoodandValdes
thantheclade. Greenseaturtlesthatbreedonislandsof 2006). Nevertheless, GCMs are tested by the rock and
theMid-AtlanticRidge(CarrandColeman1974,Bowen fossil records, so unless otherwise determined, the first
et al. 1989) may also represent hopscotch. However, order causes of climate zonation should have been ap-
neitherconcepthasseenmuchapplicationtonon-avian plicable in the Mesozoic as they are now, modified by
dinosaurs. higherorderclimaticinfluencesincludedinthemodels.
More recently, historical biogeography of islands Non-aviandinosaurlocalities,Gondwanadinosaur
was revitalized with the introduction of landspans, de- localities in particular, are ideal for this sort of review
finedbyIturralde-VinentandMacPhee(1999,p.52)as because they reflect the breakup of Gondwana into its
“asubaerialconnection(whethercontinuousorpunctu- constituentcomponentsandtheirdispersaltotheirpres-
ated by short water gaps) between a continent and an ent positions on the globe. The breakup of Gondwana
off-shelf island (or island arc)”. This stands opposed brought about first-order biogeographic change for all
to land bridges, which Iturralde-Vinent and Macphee itscomponentterrestrialbiota. Africa, SouthAmerica,
(1999,p. 52)restrictedtomean“landlinkagesbetween Madagascar, India, Australia, and Antarctica were, in
continental regions”. A significant difference between effect, verylarge-scaleNoah’sArks. Thetectonicdrift
the two is the dispersal of organisms between lands on of these arks through latitudinal climate zones was the
oceanicandcontinentalcrustintheformer,andlandson first-ordercauseofenvironmentalchangestowhichthe
continentalcrustonlyinthelatter. Iturralde-Vinentand biota living on the drifting Gondwana fragments was
MacPhee (1999) applied the concept of the GAARlan- subjected. EachfragmentofGondwanamovedthrough
dialandspan,whichisdefinedasalandmasscomprising climatic zones at different rates and crossed climatic
the conjoined Greater Antilles and Aves Ridge islands, boundariesattimesspecifictotheplace.
and then examined dispersal mechanisms in the light Our second, more speculative purpose is to iden-
of sea-level change, tectonic evolution, and vicariance tify where and when landspans may have most greatly
of the Carribean fauna (Iturralde-Vinent and MacPhee affected Gondwana dinosaur dispersal in the context
1999). The purpose of Iturralde-Vinent and MacPhee of continental movements. The relationships of land-
(1999) was to explain the biota of the Antilles; how- massesincloseproximitytoeachotherastheyconverge
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GONDWANA LATITUDINAL BIOGEOGRAPHY 5
or diverge in tectonically active terranes deserve atten- 2003),frommodeling(SellwoodandValdes2006,Hay-
tion as biogeographic landspans because those settings woodetal. 2000),andfromspecificexamples(e.g.,the
createislandarcsandhotspottraces,whichbydefinition AtacamaDesertalongthewestcoastofSouthAmerica,
areoff-shelfislandsandthereforepotentialparticipants Hartley et al. 2005) where deserts associated with the
inlandspans. descendinglimbsoftheHadleyCellshaveremainedap-
In addition to first-order influences on historical parentlyatthesamelatitudethroughtime. Therelative
biogeographycausedbyplatemotions,eustaticsea-level stabilityofHadleyCellsdoesnotimplyastableclimate.
fluctuation(Haqetal. 1987,1988)hasamajorinfluence Rather, it provides predictability for the distribution of
onthedistributionoforganismsandtheameliorationof climaticzones.
climate. A major cause of global sea level fall is the
sequestering of water in continental glaciers. Presum- METHODS
ably this was not an important factor in the Cretaceous We traced the path over the globe of selected dinosaur
as that was a period of globally warm temperatures, a localities (Fig. 1, Table I) using the Point-Tracker pro-
low pole-to-equator temperature gradient, and high sea gram published by the PALEOMAP Project (Scotese
level (Bice et al. 2003, 2006, Bice and Norris 2002, 2008), in which the present-day latitude and longitude
Jacobsetal. 2005). Thereisnoconvincingevidenceof coordinates of 51 localities are reconstructed back into
permanentpolaricecapsduringtheCretaceousPeriod. their paleolatitudinal positions at progressively older
It has been proposed that large-scale sea level change 10 Ma intervals back to 100 Ma, and in 20 Ma inter-
andclimatechangearedirectlyrelatedtoplatetectonic vals between 100 Ma and 220 Ma. Latitude was plot-
events(Scotese2004, Mülleretal. 2008), andthusare ted because climate changes with latitude, and latitude
tiedtothebreakupofGondwana. Duringtimesofcon- canbedeterminedmoreaccuratelythanlongitude. We
tinentaldispersalandrapidsea-floorspreading,suchas display these trajectories as simple plots with time on
the Cretaceous Period, the volume of ocean basins de- thex-axisandwithpaleolatitudeonthey-axis(Figs.2-
creasesresultinginhighersealevels(Scotese2004). 6). The sites were selected because together they help
Atmospheric Hadley Cells, which affect regional elucidate the history of specific regions, and individu-
climate,arecausedbyinsolationstrikingthecurvedsur- allytheyareillustrativeofthegeneralprinciplesoutlined
faceoftheEarth,leadingtowarmmoistairrisinginthe by McKenna (1973). Each of these localities is only a
tropics and cool dry air descending between about 15 single point on the continents being tracked, and does
and 30 degrees latitude in both the northern and south- not represent the entire continent as a unit. Therefore,
ernhemispheres.Therotationof theEarthimposedupon rotation of a single continental landmass can become
atmospheric cells leads to zonal wind patterns such as obvious through the convergence or crossing of trajec-
the Intertropical Convergence Zone, which marks the tories. Localities are plotted with reference to ocean
equatoriallimitofHadleyCells,andthedrytradewinds basins because the oceans are formed through rifting
characteristic of the arid zones at the poleward limits and seafloor spreading and provide a natural focus for
oftheHadleyCells. Thereisshort-termlatitudinalvari- the discussion of movement of the bordering regions
ation in the position of these boundaries and in the in- withtheirentombedfossils.
tensity of the cells due to the orientation of the Earth Scotese (2004) lists the following sources of data
(DiazandBradley2004,Sachsetal. 2009). Additional for the construction of paleogeographic maps: (i) lin-
complexityisaddedtothepatternbythelocation,orien- ear magnetic anomalies of the sea floor; (ii) paleomag-
tation,andgeographyofland,mountains,shallows,and netism,(iii)hotspottracksandlargeigneousprovinces,
oceans. However, overgeologictime, atthescalecon- (iv) tectonic fabric of the ocean floor, (v) lithologic in-
sidered here, the latitudinal limits of the Hadley Cells dicatorsofclimate,and(vi)thegeologicrecordofplate
have remained relatively stable. This is based on ev- tectonic history. For the Cretaceous, the latitudinal er-
idence from the distribution of climate-sensitive sedi- ror associated with the localities chosen for this study
mentaryrocks(Scoteseetal. 1999,Ziegleretal. 1981, islessthan 5◦ (BocharovaandScotese1993). Inad-
±
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6 LOUIS L. JACOBS, CHRISTOPHER STRGANAC and CHRISTOPHER SCOTESE
TABLEI
Dinosaurlocalitiesexamined.NumbersasinFigure1anddiscussedintext.DatafromWeishampeletal. 2004.
# Formation Location Taxa Age Lat Lon
1 Gresd’Assaouas Départmentd’Agadez,Niger therapodtracks LateJurassic-Hauterivian 18 –9
sauropodtracks
2 ArgilesdeI’Irhazer Départmentd’Agadez,Niger therapodtracks LateJurassic-Hauterivian 18 –9
euornithopodtracks
3 TiourarenFormation Départmentd’Agadez,Niger Therapoda Hauterivian-Barremian 18 –9
Tetanurae
Afrovenatorabakensis
4 ElhrazFormation Départmentd’Agadez,Niger Therapoda lateAptian 18 –9
Spinosauridae
Suchomimustenerensis
Cristatusauruslapparenti
?Spinosauridaeindet.
Tetanuraeindet.
Therapodaindet.
Sauropoda
Diplodocoidea
Nigersaurustaqueti
undescribedtitanosaurian
Sauropodaindet.
Ornithopoda
Iguantodontia
Valdosaurusnigeriensis
Ouranosaurusnigeriensis
Lurdosaurusarenatus
5 “Continentalintercalaire” Départmentd’Agadez,Niger Therapoda Albian-earlyCenomanian 18 –9
Avetherapodiaincertaesedis
Bahariasaurusingens
Allosauroidea
Carcharodontosaurussaharicus
Therapodaindet.(=Inosaurus
tedreftensis,Elaphrosaurus
iguidiensis,E.gautieri)
Sauropoda
Sauropodaindet.(=Astrodonsp.,
Rebbachisaurustamesnensis,
Aegyptosaurusbaharijensis)
Ankylosauria
Nodosauridaeindet.
6 AntenorNavarroFormation EstadodoCeará,Brazil therapodtracks pre-Aptian –5 –39
euornithopodtracks
7 SantanaFormation EstadodoCeará,Brazil Therapoda ?Albian –5 –39
Spinosauridae
Irritatorchallengeri
Angaturamalimai
unnamedcompsognathid
?Tyrannosauroidea
Santanaraptorplacidus
?Oviraptorosauridaindet.
?Ornithischiaindet.
8 TadiBeds Iembe,Angola Diplodocoidea Turonian-Coniacian –8 13
9 MocuioFormation Bentiaba,Angola Dinosauriaindet. Campanian-Maastrichtian –14 12
10 HiddenLakeFormation JamesRossIsland, Therapodaindet. Coniacian-Santonian –64 –56
AntarcticPeninsula
11 SantaMartaFormation JamesRossIsland, Ankylosauria lateCampanian –64 –56
AntarcticPeninsula Nodosauridaeindet.
12 LópezdeBertodanoFormation VegaIsland, Ornithopoda lateCampanian- –64 –56
AntarcticPeninsula Euornithopoda earlyMaastrichtian
undescribedeuornithopodan
Hadrosauridaeindet.
13 Knollenmergel Switzerland Prosauropodaindet. lateNorian 48 8
14 ObereBunteMergel Switzerland Theropodaindet.(=cf. lateNorian 48 8
Liliensternussp.)
Prosauropoda
Plateosauruscf.longiceps
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GONDWANA LATITUDINAL BIOGEOGRAPHY 7
TABLEI(continuation)
# Formation Location Taxa Age Lat Lon
15 Zanclodonmergel Switzerland Prosauropoda lateNorian 48 8
Plateosaurussp.
16 unnamedunit Switzerland Therapoda ?lateNorian-Hettangian 48 8
?Tetanuraeindet.
Prosauropoda
Plateosaurussp.
?Ornithopoda
?Heterodontosauridaeindet.(=
?Abrictosaurussp.)
17 unnamedunit Switzerland Therapodaindet. ?Oxfordian 48 8
18 unnamedunit Switzerland Therapodaindet. Oxfordian 48 8
19 unnamedunit Switzerland Stegosauriaindet. lateOxfordian 48 8
20 unnamedunit Switzerland Therapodaindet. earlyKimmeridgian 48 8
21 ReuchenetteFormation Switzerland therapodtracks Middle-lateKimmerdgian 48 8
sauropodtracks
22 VilligenFormation Switzerland Stegosauriaindet. lateOxfordian 48 8
23 ReuchenetteFormation Switzerland Therapoda Middle-lateKimmerdgian 48 8
Tetanuraeindet.(=
Megalosaurusmeriani)
therapodtracks
sauropodtracks
24 UpperSchrattenkalkFormation Switzerland euornithopodtracks lateAptian 48 8
25 SanGiovanniRotondoFormation RegionePuglia,Italy therapodtracks lateHauterivian- 41 16
?ornithopodtracks earlyBarremian
26 CalcarediAltamura RegionePuglia,Italy ?sauropodtracks lateSantonian 41 16
?ankylosaurtracks
hadrosaurtracks
27 TeganaFormation Ksar-es-souk,Morocco Therapoda Albian-Cenomanian 32 –4
Allosauroidea
Carcharodontosaurussaharicus
Sauropoda
Diplodocoidea
Rebbachisaurusgarasbae
28 UpperKem-KemBeds Ksar-es-souk,Morocco Therapoda Cenomanian 32 –4
Carnosauria
Carcharodontosaurussaharicus
Coelurosauriaincertaesedis
Deltadromeousagilis
Dromaeosauridaeindet.
theropodtracks
Sauropoda
undescribedsauropods
Sauropodaindet.(=
Rebbachisaurussp.)
sauropodtracks
Ornithopoda
undescribediguantodontian
euornithopodtracks
29 ContinentalRedBeds Ksar-es-souk,Morocco Therapoda Cenomanian 32 –4
Ceratosauria
Abelisauridaeindet.(includingcf.
Majungasaurussp.)
Tetanuraeincertaesedis
Sigilmassasaurusbrevicollis
Sigilmassasaurussp.
Spinosauridae
Spinosaurusmaroccanus
Spinosauruscf.aegyptiacus
Spinosaurussp.
Carnosauria
Carcharodontosaurussaharicus
Carcharodontosaurussp.
?Carcharodontosaurussp.
Theropodaindet.(includingcf.
Elaphrosaurussp.)
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8 LOUIS L. JACOBS, CHRISTOPHER STRGANAC and CHRISTOPHER SCOTESE
TABLEI(continuation)
# Formation Location Taxa Age Lat Lon
29 ContinentalRedBeds Ksar-es-souk,Morocco Sauropoda Cenomanian 32 –4
Lithostrotiaindet.(=
Titanosauridaeindet.)
Sauropodaindet.(including
Rebbachisaurussp.)
30 unnamedunit MechoozYerushalayim,Israel therapodtracks earlyCenomanian 32 35
31 TendaguruFormation MkoawaMtwara,Tanzania Therapoda Kimmeridgian –11 39
Ceratosauria
Elaphrosaurusbambergi
Ceratosaurussp.(=Ceratosaurus
roechlingi,Labrosaurusstechowi)
Allosauroidea
?Allosaurustendagurensis
Therapodaindet.(=
Megalosaurusingens)
Sauropoda
Sauropodaincertaesedis
Tendaguriatanzaniensis
Diplodocoidea
Dicraeosaurushansemanni
Dicraeosaurussattleri
Tornieriaafricanus
Barosaurusbrancai
Titanosauria
Janenschiarobusta
Stegosauria
Stegosauridae
Kentrosaurusaethiopicus
Ornithopoda
Iguantodontia
Dryosauruslettoworbecki
?dinosaureggs
32 IsaloIIIFormation FaritanyMajunga,Madagascar Therapoda Bathonian –16 47
?Allosauroideaindet.
Sauropoda
Titanosauriformes
Lapparentosaurusmadagascarensis
Sauropodaindet.(=Bothriospondylus
madagascarensis)
33 AnkarafantsikaFormation FaritanyMajunga,Madagascar Sauropodaindet. Cenomanian –16 47
34 Ankazomihaboka FaritanyMajunga,Madagascar Therapodaindet.(including Coniacian –16 47
Majungasauruscrenatissimus)
Sauropoda
Lithostrotia
“Titanosaurus”madagascarensis
35 MaevaranoFormation FaritanyMajunga,Madagascar Therapoda Campanian –16 47
Ceratosauria
Majungasaurusatopus
Masiakasaurusknopfleri
Majungasauruscrenatissimus
?Spinosauridaeindet.
Sauropoda
Lithostrotia
Rapetosauruskraussei
“Titanosaurus”madagascarensis
undescribedlithostrotian
Lithostrotiaindet.(=
Titanosauridaeindet.)
?Ornithischiaindet.(=Stegasaurus
madagascarensis)
36 TikiFormation MadhaPredesh,India Therapodaindet. Carnian 23 84
37 KaladongarFormation Gujarat,India Dinosauriaindet. Aalenian-Bathonian 22 77
38 PatchamFormation Gujarat,India dinosaureggs Bathonian 22 77
39 ChariFormation Gujarat,India Sauropodaindet. Callovian 22 77
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GONDWANA LATITUDINAL BIOGEOGRAPHY 9
TABLEI(continuation)
# Formation Location Taxa Age Lat Lon
40 LametaFormation Gujarat,India Therapoda Maastrichtian 22 77
Ceratosauria
Rajasaurusnarmadensis
Ceratosauriaindet.(=
Majungasauruscrenatissimus)
undescribedabelisaurids
Therapodaindet.(=
Megalosaurussp.)
Sauropodaindet.(=Titanosaurus
rahioliensis)
sauropodtracks
Ankylosauria
undescribed?ankylosaurid
dinosaureggs
41 WagadFormation Gujarat,India ?sauropodtracks Maastrichtian 22 77
?euornithopodtracks
42 AnjarFormation Gujarat,India undescribedsaurischians Maastrichtian 22 77
undescribedornithischians
dinosaureggs
43 KatrolFormation Gujarat,India ?sauropodtracks Maastrichtian 22 77
?euornithopodtracks
44 BhujFormation Gujarat,India ?sauropodtracks Maastrichtian
?euornithopodtracks
45 HansonFormation TransantarcticMountains,Antarctica Therapoda Sinemurian-Pliensbachian –84 166
Carnosauria
Cryolophosaurusellioti
Allosauroideaindet.
Therapodaindet.
Prosauropodaindet.
46 WonthaggiFormation Victoria,Australia Therapoda Valanginian-Aptian –38 146
Allosauroideaindet.
Ornithomimosauriaindet.
Dromaeosauridaeindet.
Therapodaindet.
Ankylosauriaindet.
Ornithopoda
Euornithopoda
Fulgurotheriumaustrale
Qantassaurusintrepidus
Fulgurotheriumsp.
?Ceratopsia
?Neoceratopsiaindet.(=
Serendipaceratopsarthurclarkei)
47 EumerallaFormation Victoria,Australia Therapoda earlyAlbian –38 146
Ornithomimosauriaindet.(=
Timimushermani)
?Oviraptorosauriaindet.
?Dromaeosauriaindet.
ornithischiantracks
Ornithopoda
Euornithopoda
Leaellynasauraamicagraphica
Atlascoposaurusloadsi
dinosaurtracks
48 TahoraFormation NorthIsland,NewZealand Therapodaindet. Campanian –39 176
Sauropodaindet.
Ankylosauria
Nodosauridaeindet.
Ornithopoda
Iguantodontiaindet.
49 HornofAfrica,Somalia 11 51
50 Karachi,Pakistan 25 67
51 Peshawar,Pakistan 34 71
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10 LOUIS L. JACOBS, CHRISTOPHER STRGANAC and CHRISTOPHER SCOTESE
Fig. 1–ModerndistributionofGondwanadinosaurlocalities(listedbynumberinTableI)usedinthisstudy.
ditiontospatialuncertainties,imprecisionintheageof the Paraná-Etandeka flood basalts (Renne et al. 1996),
a fossil locality is also inherent in the plots, although whichareassociatedwiththemodernTristandeCunha-
thisisnotconsideredtobeamajorproblemforcurrent Walvishotspot. Theoldestmagneticanomalyfoundin
purposes. Where an age range is reported (Weisham- oceanic crust adjacent to the Kwanza Basin along the
peletal. 2004), weusethemid-pointoftheagerange AfricancontinentischronM3(Candeetal. 1989,Mar-
inconstructingtheplots. Wehavenotupdatedthefau- ton et al. 2000), about 128 Ma following Gradstein et
nal lists from Weishampel et al. (2004), nor have we al. (2004;butcouldbe5-6myyounger;seeChannellet
made detailed comparisons of the taxonomic composi- al. 1995,Heetal. 2008,Torsviketal. 2009). Although
tionbetweenlocalities.Anyattemptatphylogeographic rifting began earlier, the complete separation of South
analysisisbeyondthescopeofthispaper. America and Africa occurred between 115 Ma and
90 Ma with the completion of the Equatorial Atlantic
Gateway(BrownfieldandCharpentier2006,Jacobsetal.
RESULTS
2009). By 90 Ma (Turonian), a deepwater passage de-
Figure 2 shows the opening of the South Atlantic by velopedbetweenthesouthernNorthAtlanticandSouth
tracingpointsthatnowfallinconjugatebasinsinSouth Atlantic(Handohetal. 1999). Africawasclearlymov-
America and Africa. The two lines at 220 Ma repre- ingnorthrelativetoSouthAmerica,asindicatedbythe
sentthereconstructedpositionsoftheSergipe(Brazil)- divergingcontinentaltrajectoriesinFigure2. LateAp-
Gabonconjugatebasinsalongthemorenortherly(lower tian (115-112 Ma; Gradstein et al. 2004) marine in-
latitude) line, and the Campos (Brazil)-Kwanza (An- vertebrates are found in the Sergipe Basin (Bengtson
gola)conjugatebasinsalongthemoresoutherly(higher and Koutsoukos 1992, Koutsoukos 1992), which may
latitude)line. Theparallelarchingtrajectoriesontheleft have remained marine continuously since then (Kout-
ofFigure2indicateuniformmovement,thelinesbeing soukosetal. 1991),althoughthereisevidence(including
parallel because the movement of the single land mass fossil fish, Maisey 2000) for two broader marine trans-
wasdirectionallyhomogeneousinPangea. gressionsoverBrazilduringthelateAptianandAlbian
The South Atlantic opened with a counterclock- (Valençaetal. 2003). Thus,theopeningoftheAtlantic
wise rotation of Africa. At the paleolatitudes repres- atthelatitudesoftheCampos-Kwanzaconjugatebasins
ented in Figure 2, the rifting between South America isbetween132and128Ma, whiletothenorth, theev-
and Africa occurred between 132 1 Ma, the age of idence for marine conditions is no older than 115 Ma.
±
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GONDWANA LATITUDINAL BIOGEOGRAPHY 11
Fig. 2–RelativemotionsofconjugatebasinsthatdivergedduringtheopeningoftheSouthAtlantic. TheconjugatebasinsaretheSergipe
(Brazil)-GabonandtheCampos(Brazil)-Kwanza(Angola). TheAlbianfossillocalitiesoftheSantanaFormation,Brazil,arenorthwestofthe
CamposBasin. TheKwanzaBasincontainstheTuronianlocalityofIembe. Theinsetmapshowsthepositionofbasinsduringtheearlyphase
ofopeningoftheSouthAtlanticOcean. ThegrayshadingindicatesriftingatthepaleolatitudeoftheKwanzaBasin(132-128Ma);thedashed
verticallineonleft(115Ma)indicatesmarinesedimentsintheSergipeBasinandinitiationofashallowEquatorialAtlanticGateway;vertical
dashedlineat90MaindicatescompletionofadeepAtlanticEquatorialGateway.
Thedivergingcurvesafter115MainFigure2reflectthe Figure 2 has no significance as far as rotation, but it
northward drift of Africa relative to South America as emphasizesthenorthwarddriftofAfrica.
theSouthAtlanticwidened. Figure 3 tracks the famous Santana Formation lo-
Thisexampleservestodemonstratetheusefulness calitiesofAraripe(6)andtheoldersitesoftheAntenor
of the method of plotting latitude trajectories through NavarroFormation(7)inthestateofCearáwestofthe
timeusingpaleolatitudescalculatedbythePoint-Tracker SergipeBasininBrazil. WechosetheseBraziliansites
program of PALEOMAP (Scotese 2008). The opening becausetheywereproximaltothelastpointofconnec-
oftheSouthAtlanticisperhapsthebestdocumentedof tion with Africa. The fossil sites of Antenor Navarro
all the major oceans because the Walvis Ridge and St. were formed essentially at the Equator, at lower lati-
Helenahotspotscanbeusedtopreciselymodeltherel- tudethanthelakebedsoftheAlbianSantanaFormation.
ativemotionsbetweentheSouthAmericanandAfrican BothunitsweredepositedasSouthAtlanticriftingwas
plates (O’Connor and Duncan 1990, O’Connor and Le initsearlyphases,priortotheestablishmentofthedeep
Roex1992,O’Connoretal.1999). Thecrossingofthe water Equatorial Gateway (90 Ma) between the south-
Kwanza basin trace with that of the Sergipe Basin in ernNorthAtlanticandtheSouthAtlantic. Allofthese
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12 LOUIS L. JACOBS, CHRISTOPHER STRGANAC and CHRISTOPHER SCOTESE
Fig. 3–LatitudinaltrajectoriesofGondwanadinosaurlocalities(listedbynumberinTableI)intheSouthAtlanticregion.
Braziliansiteshaveremainedinthesouthernhemisphere Two localities from Angola were selected, not be-
tropics ever since, close to the latitudes at which they cause they are well represented by dinosaurs (they are
wereformed,duetothefactthatSouthAmericahashad not), but because their ages are well constrained and
littlenorthwarddrift. LocalitiesfarthersouththanBrazil they were both formed under arid coastal conditions.
in South America (not plotted) would show essentially Bothlocalitiesformedinthesouthernaridbelt. Anew
thesametrajectoryasthoseofBrazil, offsetbythelat- Turonian sauropod was found at Iembe (locality 8),
itudinaldistancebetweensites,becauseSouthAmerica which now lies in tropical latitudes (8◦S; Jacobs et al.
sincetheEarlyCretaceousmovednearlyduewestwith 2006, 2009, Mateus et al. 2011). Only a few bones
verylittlechangeinlatitude. of dinosaurs have yet been found at Bentiaba (locality
ThedinosaurlocalitiesofNiger(localities1-5)re- 9), which currently lies at the northern extreme of the
cordthehistoryofAfricafromthepre-riftLateJurassic, Skeleton Coast or Namib Desert. These two localities
throughtotheEarlyCretaceousphaseofSouthAtlantic illustrate the importance of recognizing the position of
Ocean basin formation. None appears as young as the astationaryclimatezonethroughwhichadriftingconti-
LateCretaceouscompletionof thedeepEquatorialGate- nentpasses. Iembe,althoughtropicalnow,wasactually
way(90Ma). AlloftheNigerlocalitieswereformedat formedinthedesertundersimilarconditionstothosein
thenorthernedgeofthetropics. whichtheBentiabalocalitywasformed. Onemightinfer
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