Vertebrate Palaeodistributional Patterns and Continental Drift Author(s): C. Barry Cox Source: Journal of Biogeography, Vol. 1, No. 2 (Jun., 1974), pp. 75-94 Published by: Blackwell Publishing Stable URL: http://www.jstor.org/stable/3037956 Accessed: 01/09/2010 19:51 Your use of the JSTOR archive indicates your acceptance of JSTOR's Terms and Conditions of Use, available at http://www.jstor.org/page/info/about/policies/terms.jsp. JSTOR's Terms and Conditions of Use provides, in part, that unless you have obtained prior permission, you may not download an entire issue of a journal or multiple copies of articles, and you may use content in the JSTOR archive only for your personal, non-commercial use. Please contact the publisher regarding any further use of this work. Publisher contact information may be obtained at http://www.jstor.org/action/showPublisher?publisherCode=black. Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. Blackwell Publishing is collaborating with JSTOR to digitize, preserve and extend access to Journal of Biogeography. http://www.jstor.org Journalof Biogeography(1974) 1, 75-94 Vertebratepalaeodistributional patterns and continentaldrift C. BARRY COX merica' (Asia plus westernNorth America) and Zoology Department,King's College,Strand, London 'Euramerica' (easternNorth Americaplus Europe). A barrierappears to have formedbetween Asia and westernNorth America in the UppermostCretaceous. Bothmarsupials and condylarthplacental mammals Abstract appear to have crossedbetween Laurasia and Gond- wanaland in the Upper Cretaceous; their route is The patternsof distributionof vertebrates(primarily uncertain,but a trans-Caribbeanisland sweepstakes terrestrialforms) are analysed from the Silurian route seems the most likely. Marsupials probably onwards,using palaeogeographical maps whichshow enteredAustralia from South America via Antarctica, epicontinentalseas as well as intercontinentaloceans. placentalsevolving later and being unable to follow Silurian vertebrates(fish) are known almost thembecause theSouth America-Antarcticalink had exclusivelyfrom Euramerica. Many Devonian fish by thenbroken. whichare normallyfound in fresh waters seem to have The apparent areas of origin of the different been able to cross interveningseas between one mammalianorders are shownin Venndiagrams. The continentand another.It is suggestedthat this ability historyof the faunal relationshipsof the mammal maybe physiologicallyrelated to theircapacity to use faunas of thedifferent land massesduring the Tertiary aerial respiration.There is some evidencefor a is outlined. separate Devonian osteostracanfish fauna in China. Amphibiansare first knownfrom the uppermost Devonian of the Euramericancontinent, and land Introduction vertebratesare knownalmost exclusivelyfrom that continentuntil the Mid Permian.It is suggestedthat Much of biogeographyis at presentin a state of tetrapodsmay have evolvedin Euramerica,and were adjustmentto the new frameworkof plate tectonics. only able to colonize Asia and Gondwanalandafter Geophysicistshave almostliterally taken the ground continentaldrift had linked these areas with Eur- from under old theories. Much biogeographical america, causing the Uralian and Alleghanian interpretationin even comparativelyrecent literature orogenies. has tended to accept the old hypotheses,based on The tetrapodfauna of the Upper Permian and static geography,and to seek new justificationsfor Triassic appears to have been cosmopolitan.Though them in the shiftingpatterns of plate tectonics.A Pangaea started to break up in the Jurassic,land fresh start should instead be made, plotting the vertebrateswere still able to dispersebetween Eur- distributionalpatterns on palaeogeographicalassem- americaand Asia (probablyvia theBering region) and blages and tryingto see whatthe implications are for between the Northernand Southern Hemispheres intercontinentalbiological connections.These new (probablyvia southernEurope). ideas formthe rationalebehind thispaper. In many Thereis littleevidence that dinosaurs were able to cases, palaeogeographicaldata are now morefirmly cross the Cretaceous Tethyansea barrierbetween establishedthan the data of palaeodistributions,and Laurasia and Gondwanaland. Lower Cretaceous should be used to generate-questions to ask the dinosaurs were able to disperse throughoutthe palaeobiological world. In some cases, however, NorthernHemisphere, presumably by a continuation distributionaldata are still the betterknown, and of theBering link. In the UpperCretaceous, the Mid- may help to indicatethe most likelysolution for the ContinentalSeaway of NorthAmerica, together with palaeogeographers.Of course, where there is an theTurgai Straits between Europe and Asia, separated apparentinconsistency between the implicationsof two land areas withdistinct dinosaur faunas: 'Asia- the two sets of data, both must be regarded as 6 75 76 C. BarryCox meriting reconsideration until an interpretation data of thisperiod indicatethe approximatepalaeo- acceptableto both disciplineshas been reached. latitudeof each fragment,it should be notedthat the There are many factors which can bias our palaeolongitudinal(east-west) distances between the knowledgeof the fossil record. Obviously enough, fragmentsare unknown.For a moredetailed discuss- fossilscan only be foundin a particulararea if they ion ofthese points, see Smith,Briden & Drewry,1973. were deposited in sediments laid down in the The maps presentedherein extend over 270? of appropriate environment,which are themselves longitude. Where they lie within a reassembled revealed by erosion or earth movement,in an area supercontinent,or at some distancefrom the edge of thatis physicallyaccessible and is visitedby a suffi- the continentalshelf, present day coastlines are cientlycurious or trainedobserver or collector.The shown as interruptedlines. Details of the shallow, absence of fossilsfrom a particularstretch of geo- epicontinentalseas have been added, mainly after logical time,from a particulargeographic area or Kummel (1970), as thesewere almost as effectiveas fromdeposits of a particularcharacter, may be due oceans in actingas barriersto thespread of terrestrial to the absence of any of thesenecessary conditions. organisms.Though the extentof theseseas, and the Such an explanation is probably often,even nor- width of the oceans, will have varied somewhat mally, correct.Nevertheless, this should not blind duringthe period of timecovered by each map, the us to the possibilitythat a taxon may not have been basic biogeographicalpatterns will not have been found in a particulararea because, quite simply,it affected.The locations of the major sites at which neverexisted there. vertebrateshave been found have also been added, Our new understandingof palaeogeographyalso to givesome idea of theextent of thefactual basis for reveals new possible anomalies. As will be seen statementswhich relate to biogeographicalpatterns later, the presence of a new taxon in a particular of distribution. continenthas in some cases been suggestedon the basis of somewhat unconvincingevidence, which does not includethe critical diagnostic features of the Silurian-Devonianpatterns (Fig. 1) taxon. One's doubts of thesesuggestions are streng- thenedif it now appears thatthey are the only basis In the Palaeozoic period, Gondwanaland seems to forbelieving the taxon to be presentnot merelyin a have had a historyquite differentfrom that of the single modern continent,but in an entire super- restof the world (Briden,1973). It seems alreadyto continentsuch as Gondwanaland. have been complete in the Ordovician, as it is Though ideally one should take into account all traversedby no orogenic belts youngerthan 500 the organicdistributions of any givenperiod of time million years. In contrast,North America,Europe when tryingto evaluate patternsof life,the record and Siberia were all separatefrom one another,and of the vertebratesis comparativelywell known,and the Palaeozoic whereabouts of China are still in particularthe normallyterrestrial mode of life uncertain(Smith, Briden & Drewry,1973). of tetrapodsprovides a good test of land connec- That NorthAmerica, Europe and Asia wereall in tions; accordingly,it is the palaeodistributional relativemotion duringthe Palaeozoic is suggested patternsof these groups from the Silurian period not only by the fact that theydid meet in the late onwards which are to be examined in the present Palaeozoic, but also by the orogenicactivity along study. Maps prepared for a 1971 Symposium in their margins. The fusion of the Canadian and Cambridge, England (Smith, Briden & Drewry, Baltic Shields took place in the Upper Silurian to 1973) have been used as a palaeogeographicbasis for Mid Devonian,judging by thedate of theCaledonian the study,with a few minormodifications noted in and Acadian orogenies which signal that meeting thelegends. For the Mesozoic period,these maps are (McKerrow & Ziegler,1972). Partlybecause of this based upon data from three independentlines of erosional-sedimentaryactivity in theNorth American enquiry-palaeomagnetism,sea floorspreading and