Plate Motions, Gondwana Dinosaurs, Noah's Arks, Beached Viking Funeral Ships, Ghost Ships PDF
Preview Plate Motions, Gondwana Dinosaurs, Noah's Arks, Beached Viking Funeral Ships, Ghost Ships
“main” — 2011/2/10 — 12:16 — page 3 — #1 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] AnAcadBrasCienc(2011)83(1) “main” — 2011/2/10 — 12:16 — page 4 — #2 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 AnAcadBrasCienc(2011)83(1) “main” — 2011/2/10 — 12:16 — page 5 — #3 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- ± AnAcadBrasCienc(2011)83(1) “main” — 2011/2/10 — 12:16 — page 6 — #4 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 AnAcadBrasCienc(2011)83(1) “main” — 2011/2/10 — 12:16 — page 7 — #5 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.) AnAcadBrasCienc(2011)83(1) “main” — 2011/2/10 — 12:16 — page 8 — #6 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 AnAcadBrasCienc(2011)83(1) “main” — 2011/2/10 — 12:16 — page 9 — #7 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 AnAcadBrasCienc(2011)83(1) “main” — 2011/2/10 — 12:16 — page 10 — #8 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. ± AnAcadBrasCienc(2011)83(1) “main” — 2011/2/10 — 12:16 — page 11 — #9 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 AnAcadBrasCienc(2011)83(1) “main” — 2011/2/10 — 12:16 — page 12 — #10 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 AnAcadBrasCienc(2011)83(1)
Description:The list of books you might like
