Great American Interchange

The Great American Interchange was an important paleozoogeographic event in which land and freshwater fauna migrated from North America via Central America to South America and vice versa, as the volcanic Isthmus of Panama rose up from the sea floor and bridged the continents. The migration peaked dramatically around 3 million years (Ma) ago (in the Piacenzian, the first half of the Upper Pliocene).

It resulted in the joining of the Neotropic (roughly South America) and Nearctic (roughly North America) definitively to form the Americas. The interchange is visible from observation of both stratigraphy and nature (neontology). Its most dramatic effect is on the zoogeography of mammals but it also gave an opportunity for non-flying birds, arthropods, reptiles, amphibians and even freshwater fish to migrate.

outh America's endemic fauna

After the late Mesozoic breakup of Gondwana, South America spent most of the Cenozoic era as an island continent whose "splendid isolation" allowed its fauna to evolve into forms found nowhere else on earth. Its endemic mammals initially consisted of marsupials, xenarthrans (i.e., armadillos, anteaters and sloths, like the giant ground sloth "Megatherium"), and a diverse group of native ungulates: notoungulates (the "southern ungulates"), litopterns, astrapotheres (e.g. "Trigonostylops", "Astrapotherium"), and pyrotheres (e.g. "Pyrotherium").

Marsupials may have traveled (via Gondwanan land connections) from South America through Antarctica to Australia and/or vice versa in the late Cretaceous or early Tertiary. One living S. American marsupial, the Monito del Monte, is believed to be more closely related to Australian marsupials than to other South American marsupials. A 61-Ma-old platypus-like monotreme fossil from Patagonia may represent another Australian immigrant. It appears that ratites (relatives of S. American tinamous) migrated by this route around the same time, more likely in the direction from S. America towards Australia/New Zealand.cite journal
last = Briggs
first = J. C.
authorlink =
coauthors =
title = Fishes and Birds: Gondwana Life Rafts Reconsidered
journal = Syst. Biol.
volume = 52
issue = 4
pages = 548–553
publisher =
location =
year = 2003
url = http://www.jstor.org/sici?sici=1063-5157(200308)52%3A4%3C548%3AFABGLR%3E2.0.CO%3B2-L
doi = 10.1080/10635150390218385
id = ISSN: 1063-5157
accessdate = 2008-04-05
month = Aug
year = 2003] Other taxa that may have dispersed by the same route (if not by flying or floating across the ocean) are parrots, chelid turtles and (extinct) meiolaniid turtles.

The marsupials present in South America included didelphimorphs (opossums) and other small forms, but many larger predatory forms also existed, like the borhyaenids and the sabertooth "Thylacosmilus". The marsupials shared the ecological niches for large predators with fearsome flightless "terror birds" (phorusrhacids), whose closest extant relatives are the seriemas.cite web
last = Naish
first = Darren
authorlink =
coauthors =
title = Terror birds
work = Darren Naish: Tetrapod Zoology
publisher =
date = 2006-10-27
url = http://darrennaish.blogspot.com/2006/10/terror-birds.html
format =
doi =
accessdate = 2008-03-29] cite journal
last = Alvarenga
first = H. M. F.
authorlink =
coauthors = Höfling, E.
title = Systematic Revision of the Phorusrhacidae (Aves: Ralliformes)
journal = Papéis Avulsos de Zoologia
volume = 43
issue = 4
pages = 55–91
publisher = [http://www.usp.br/mz/ Museu de Zoologia da Universidade de São Paulo]
location = São Paulo
year = 2003
url = http://www.scielo.br/pdf/paz/v43n4/17491.pdf
doi =
id = ISSN 0031-1049
accessdate = 2008-03-29|format=PDF] (Terrestrial ziphodont sebecid crocodilians were also present at least through the middle Miocene. [cite journal
last = Paolillo
first = A.
authorlink =
coauthors = Linares, O. J.
title = Nuevos Cocodrilos Sebecosuchia del Cenozoico Suramericano (Mesosuchia: Crocodylia)
journal = Paleobiologia Neotropical
volume = 3
issue =
pages = 1-25
publisher = [http://www.paleobio.labb.usb.ve/index.html Laboratorio de Paleobiología]
location = Caracas
date = 2007-06-05
url = http://www.paleobio.labb.usb.ve/Paleobio03.pdf
doi =
id =
accessdate = 2008-09-28] [cite journal
last = Busbey
first = Arthur B. III
authorlink =
coauthors =
title = New Material of "Sebecus" cf. "huilensis" (Crocodilia: Sebecosuchidae) from the Miocene La Venta Formation of Colombia
journal = Journal of Vertebrate Paleontology
volume = 6
issue = 1
pages = 20-27
publisher =
location =
date = 1986-03-07
url = http://www.jstor.org/stable/4523070
doi =
id =
accessdate = 2008-09-28] [Citation
first = R.
last = Salas-Gismondi
author-link =
first2 =
last2 = et al.
author2-link =
editor-last = Díaz-Martínez
editor-first = E.
editor2-last = Rábano
editor2-first = I.
contribution = Middle Miocene Crocodiles From the Fitzcarrald Arch, Amazonian Peru
contribution-url = http://www.igme.es/4empsla/libro/62.pdf
title = 4th European Meeting on the Palaeontology and Stratigraphy of Latin America
year = 2007
pages = 355-360
place = Madrid
publisher = [http://www.igme.es/internet/default.asp Instituto Geológico y Minero de España]
url =
isbn = 978-84-7840-707-1
doi =
id = ] cite journal
last = Gasparini
first = Zulma
authorlink =
coauthors =
title = New Tertiary Sebecosuchia (Crocodylia: Mesosuchia) from Argentina
journal = Journal of Vertebrate Paleontology
volume = 4
issue = 1
pages = 85-95
publisher =
location =
date = Sept. 1984
url = http://www.jstor.org/stable/4522967
doi =
id =
accessdate = 2008-09-29] )

The notoungulates and litopterns had many strange forms, like "Macrauchenia", a camel-like litoptern with a small proboscis. They also produced a number of familiar-looking body types that represent examples of parallel or convergent evolution: one-toed "Thoatherium" had legs like those of a horse, "Pachyrukhos" resembled a rabbit, "Homalodotherium" was a semi-bipedal clawed browser like a chalicothere, and horned "Trigodon" looked like a rhino. Both groups started evolving in the Lower Paleocene, possibly from condylarth stock, diversified, dwindled before the great interchange, and went extinct in the Pleistocene. The pyrotheres and astrapotheres were also strange but were less diverse and disappeared earlier, well before the interchange.

The North American fauna was a pretty typical boreoeutherian one (supplemented with Afrotherian proboscids).

Island-hopping ‘waif dispersers’

The invasions of South America started at least 31.5 Ma ago (late Eocene/early Oligocene), when cavimorph rodents arrived. Their subsequent vigorous diversification displaced some of S. America's small marsupials and gave rise to – among others – capybaras, chinchillas, viscachas, and New World porcupines. (The independent development of spines by New and Old World porcupines is another example of parallel evolution.) This invasion most likely came from Africa. [cite journal
title=Recent advances in South American mammalian paleontology
author= J. J. Flynn, A. R. Wyss
journal=Trends in Ecology and Evolution
volume=13
issue=11
pages=449–454
year=1998
doi= 10.1016/S0169-5347(98)01457-8] The crossing from West Africa to the northeast corner of Brazil was much shorter then due to continental drift, and may have been aided by island-hopping (e.g. via St. Paul's Rocks, if they were an inhabitable island at the time) and westward oceanic currents. [cite journal
title= Low-Latitude Circulation and Mass Transport Pathways in a Model of the Tropical Atlantic Ocean
last = Fratantoni
first = D. M.
authorlink =
coauthors = Johns, W. E., Townsend, T. L., Hurlburt, H. E.
journal= Journal of Physical Oceanography
volume= 30
issue= 8
pages= 1944–1966
date = 2000-08
url= http://ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F1520-0485(2000)030%3C1944:LLCAMT%3E2.0.CO%3B2&ct=1
doi= 10.1175/1520-0485(2000)030<1944:LLCAMT>2.0.CO;2
format= abstract
year= 2000] Crossings of the ocean were accomplished when at least one fertilised female (more commonly a group of animals) accidentally floated over on driftwood or mangrove rafts. (Island-hopping cavimorphs would subsequently colonize the West Indies as far as the Bahamas).

A little later (at least 25 Ma ago) primates followed, probably from Africa in a fashion similar to that of the rodents. Primates capable of migrating had to be small. With little effective competition they also diversified widely, giving rise to the New World monkeys. (Not long after arriving, monkeys apparently most closely related to titis island-hopped to Cuba, Hispaniola and Jamaica.) The South American cavimorph rodents and monkeys are both believed to be clades (i.e., monophyletic).

Tortoises also arrived in South America in the Oligocene. It was long thought that they had come from N. America, but a recent comparative genetic analysis concludes that S. American members of "Geochelone" are actually most closely related to African hingeback tortoises.Ref_label|A|a|nonecite journal
last = Le
first = M.
authorlink =
coauthors = Raxworthy, C. J., McCord, W. P., Mertz, L.
title = A molecular phylogeny of tortoises (Testudines: Testudinidae} based on mitochondrial and nuclear genes
journal = Molecular Phylogenetics and Evolution
volume = 40
issue =
pages = 517-531
publisher =
location =
date = 2006-05-05
url = http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WNH-4JWFGYC-1&_user=4430&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000059594&_version=1&_urlVersion=0&_userid=4430&md5=17737ababb8f6b572a3a44a520001dc6
doi = 10.1016/j.ympev.2006.03.003
id =
accessdate = ] Tortoises are aided in oceanic dispersal by their ability to float with their heads up, and to survive up to six months without food or water. S. American tortoises then went on to colonize the West Indies and Galápagos Islands. Skinks of genus "Mabuya" apparently floated across the Atlantic from Africa during the last 9 Ma. [cite journal
last = Carranza
first = S.
authorlink =
coauthors = Arnold, N. E.
title = Investigating the origin of transoceanic distributions: mtDNA shows Mabuya lizards (Reptilia, Scincidae) crossed the Atlantic twice
journal = Systematics and Biodiversity
volume = 1
issue = 2
pages = 275–282
publisher = Cambridge University Press
location =
date = 2003-08-05
url = http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=168963
id =
doi= 10.1017/S1477200003001099
accessdate = 2008-04-04]

The earliest mammalian arrivals from North America were carnivorous procyonids that island-hopped from Central America prior to the formation of a land bridge, around 7 Ma ago. Some South American procyonids then diversified into forms now extinct (e.g. the "dog-coati" "Cyonasua", which evolved into the bear-like "Chapalmalania"). However, all extant procyonid genera appear to have originated in North America. [cite journal
title=Phylogeny of the Procyonidae (Mammalia: Carvnivora): Molecules, morphology and the Great American Interchange
author= K.-P. Koepfli, M. E. Gompper, E. Eizirik, C.-C. Ho, L. Linden, J. E. Maldonado, R. K. Wayne
journal=Molecular Phylogenetics and Evolution
volume=43
issue=3
pages=1076–1095
year=2007
doi= 10.1016/j.ympev.2006.10.003 ] It has been suggested that the first S. American procyonids may have contributed to the extinction of sebecid crocodilians by eating their eggs, but this view has not been universally viewed as plausible.Ref_label|B|b|none The procyonids were followed to S. America by island-hopping sigmodontine rodentscite journal
last = Marshall
first = L. G.
authorlink =
coauthors = Butler, R. F.; Drake, R. E.; Curtis, G. H.; Tedford, R. H.
title = Calibration of the Great American Interchange
journal = Science
volume = 204
issue = 4390
pages = 272–279
publisher = AAAS
location =
date = 1979-04-20
url = http://www.sciencemag.org/cgi/content/abstract/204/4390/272
doi = 10.1126/science.204.4390.272
id =
accessdate = 2008-04-15
format = abstract
pmid = 17800342] , peccaries and hog-nosed skunks.cite journal
last = Webb
first = S. D.
authorlink =
coauthors =
title = Mammalian Faunal Dynamics of the Great American Interchange
journal = Paleobiology
volume = 2
issue = 3
pages = 220–234
publisher = Paleontological Society
location =
year = 1976
url = http://www.jstor.org/stable/2400220
doi =
id =
accessdate = 2008-04-15]

Similarly, megalonychid and mylodontid ground sloths island-hopped to North America by 9 Ma ago. Megalonychids had colonized the Antilles previously, by the early Miocene [Citation
last = Morgan
first = Gary S.
editor-last = Emry
editor-first = Robert J.
contribution = Late Rancholabrean Mammals from Southernmost Florida, and the Neotropical Influence in Florida Pleistocene Faunas
title = Cenozoic Mammals of Land and Sea: Tributes to the Career of Clayton E. Ray
year = 2002
journal = Smithsonian Contributions to Paleobiology
publisher = Smithsonian Institution Press
location = Washington, D.C.
volume = 93
pages = 15–38
url = http://www.sil.si.edu/smithsoniancontributions/Paleobiology/sc_RecordSingle.cfm?filename=SCtP-0093] , and may have reached N. America by that route, since the oldest N. American fossils are from Florida.

The Great American Biotic Interchange

The formation of the Isthmus of Panama led to the last and most conspicuous wave, the great interchange, around 3 Ma ago. This included the immigration of North American ungulates (including llamas, tapirs, deer and horses), proboscids (gomphotheres), carnivorans (including felids like cougars and saber-toothed cats, canids, mustelids, procyonids and bears) and a number of types of rodentsRef_label|C|c|none into South America.

In general, the initial net migration was symmetrical. Later on, however, the Neotropic species proved far less successful than the Nearctic. This misfortune happened both ways. Northwardly migrating animals often were not able to compete for resources as well as the North American species already occupying the same ecological niches; even when they became established, they usually did not diversify much. Southwardly migrating Nearctic species diversified more, and are thought to have caused the extinction of a large proportion of the South American fauna. (There were no extinctions in N. America obviously attributable to S. American immigrants.) Although terror birds were initially able to invade N. America, this success was temporary; all of the large Neotropic avian and marsupial predators ultimately disappeared. South America's native ungulates also fared very poorly, with only several of the largest forms, "Macrauchenia" and a few toxodontids, withstanding the northern onslaught. (Among the notoungulates, the mesotheriids and hegetotheriids did manage to survive into the Pleistocene.) Its small marsupials fared better, while the primitive-looking xenarthrans proved to be surprisingly competitive. The African immigrants, the cavimorph rodents and platyrrhine monkeys, generally held their own during the interchange, although the largest rodents (e.g. the dinomyids) seem to have disappeared. With the exception of the North American porcupine and several extinct porcupines and capybaras, however, they did not migrate past Central America.Ref_label|D|d|none

The presence of armadillos, opossums, and porcupines in the United States today is explained by the Great American Interchange. Opossums and porcupines were among most successful northward migrants, reaching as far as Canada. While only one example each of xenarthrans, marsupials and cavimorph rodents currently lives in North America, 32 species from these taxa are present in tropical Central America. Prior to the end-Pleistocene extinctions, most major groups of xenarthrans were established in Central or North America (as a result of at least seven successful invasions of the latter, and at least six more of only the former). Among the megafauna, ground sloths were notably successful invaders of North America; "Megalonyx" spread as far north as the Yukon. [cite journal
last = McDonald
first = H. G.
authorlink =
coauthors = Harington, C. R.; De Iuliis, G.
title = The Ground Sloth "Megalonyx" from Pleistocene Deposits of the Old Crow Basin, Yukon, Canada
journal = Arctic
volume = 53
issue = 3
pages = 213–220
publisher = [http://www.arctic.ucalgary.ca/ The Arctic Institute of North America]
location = Calgary, Alberta
date = Sept. 2000
url = http://pubs.aina.ucalgary.ca/arctic/Arctic53-3-213.pdf
doi =
id =
accessdate = 2008-08-16|format=PDF]

Generally speaking, however, the dispersal and subsequent explosive adaptive radiation of sigmodontine rodents throughout South America was much more successful (both spatially and by number of species) than any northward migration of S. American mammals. Other examples of N. American mammal groups that diversified conspicuously in S. America include canids and cervids, both of which currently have . Although "Canis" currently ranges only as far south as Panama, S. America still has more extant canid genera than any other continent.

Reasons for success or failure

The eventual triumph of the Nearctic migrants was ultimately based on geography, which played into the hands of the northern invaders in two crucial respects. The first was a matter of climate. Obviously, any species that reached Panama from either direction had to be able to tolerate . Those migrating southward would then be able to occupy much of South America without encountering climates that were markedly different. However, northward migrants would begin to encounter drier and/or cooler conditions as soon as they reached the doorstep of North America. The challenge this climatic asymmetry (see map) presented was particularly acute for Neotropic species specialized for tropical rainforest environments, who had little prospect of penetrating beyond Central America.

The second and more important advantage geography gave to the northerners is related to the land area available for their ancestors to evolve in. During the Cenozoic, North America was periodically connected to Eurasia via Beringia, allowing multiple migrations back and forth to unite the faunas of the two continents. Eurasia was connected in turn to Africa, which contributed further to the species that made their way to North America. South America, on the other hand, was connected to Antarctica and Australia, two much smaller continents, only in the earliest part of the Cenozoic, and this land connection does not seem to have carried much traffic (apparently no mammals other than marsupials and perhaps a few monotremes ever migrated by this route). Effectively, this means that northern hemisphere species arose over a land area roughly six times larger than was available to S. American species. This calculation may not be entirely fair, in that migrations between continents would have been more difficult and less frequent than migrations within S. America. Nevertheless, it is clear that N. American species were products of a larger and more competitive arena, where evolution would have proceeded more rapidly. They tended to be more efficient and brainier, generally able to outrun and outwit their S. American counterparts. These advantages can be clearly seen in the cases of ungulates and their predators, where S. American forms were replaced wholesale by the invaders.

Against this backdrop, the ability of S. America's xenarthrans to compete effectively against the northerners represents a special case. The explanation for the xenarthrans' success lies in their idiosyncratic approach to defending against predation, based on possession of body armor and/or formidable claws. The xenarthrans did not need to be fleet-footed or quick-witted to survive. Such a strategy may have been forced on them by their low metabolic rate (the lowest among the therians). [cite journal
last = Elgar
first = M. A.
authorlink =
coauthors = Harvey, P. H.
title = Basal Metabolic Rates in Mammals: Allometry, Phylogeny and Ecology
journal = Functional Ecology
volume = 1
issue = 1
pages = 25–36
publisher = British Ecological Society
location =
year = 1987
url = http://www.jstor.org/stable/2389354
doi = 10.2307/2389354
id =
accessdate = 2008-04-18] [cite journal
last = Lovegrove
first = B. G.
authorlink =
coauthors =
title = The Zoogeography of Mammalian Basal Metabolic Rate
journal = The American Naturalist
volume = 156
issue = 2
pages = 201–219
publisher = The University of Chicago Press
location =
date = 2000-08
url = http://www.jstor.org/stable/3079219
doi = 10.1086/303383
id =
accessdate = 2008-04-19] Their low metabolic rate may in turn have been advantageous in allowing them to specialize on less abundant and/or less nutritious food sources.

End-Pleistocene extinctions

At the end of the Pleistocene epoch, about 12,000 years ago, three dramatic developments occurred in the Americas at roughly the same time (geologically speaking). Paleoindians invaded and occupied the New World, the last glacial period came to an end, and a large fraction of the megafauna of both North and South America went extinct. This wave of extinctions swept off the face of the Earth many of the successful participants of the Great American Interchange, as well as other species that had not migrated. All the pampatheres, glyptodonts, ground sloths, equids, proboscids, dire wolves, lions and "Smilodon" species of both continents disappeared. The last of the South and Central American notoungulates and litopterns died out, as well as North America's giant beavers, dholes, native cheetahs, scimitar cats, and many of its antilocaprid, tayassuid, cervid and bovid ungulates. Some groups survived in their adopted homes but disappeared over most or all of their original range, e.g. South American tapirs, camelids and tremarctine bears (cougars and jaguars may have been temporarily reduced to S. American ranges also). Others, such as capybaras, survived in their original range but died out in areas they had migrated to.

The near-simultaneity of the megafaunal extinctions with the glacial retreat and the peopling of the Americas has led to proposals that both climate change and human hunting played a role. However, a number of considerations suggest that human activities were pivotal. The extinctions did not occur selectively in the climatic zones that would have been most affected by the warming trend, and there is no plausible general climate-based megafauna-killing mechanism that could explain the continent-wide extinctions. The climate change took place worldwide, but had little effect on the megafauna in areas like Africa and South Asia, where megafaunal species had coevolved with humans. Numerous [http://en.wikipedia.org/wiki/
] [http://en.wikipedia.org/wiki/
] had occurred previously within the ice age of the last several Ma without ever producing comparable waves of extinction in the Americas or anywhere else. Similar megafaunal extinctions have occurred on other recently populated land masses (e.g. Australia, Madagascar, New Zealand, and many smaller islands around the world, such as Cyprus) at different times that correspond closely to the first arrival of humans at each location. Additionally, on sizable islands far enough offshore from newly occupied territory to escape immediate human colonization, megafaunal species sometimes survived for thousands of years after they became extinct on the mainland; examples include meiolaniid turtles on Lord Howe Island and New Caledonia, ground sloths on the Antilles, Steller's sea cows off the Commander Islands and wooly mammoths on Wrangel Island and Saint Paul Island. The glacial retreat may have played a primarily indirect role in the extinctions by simply facilitating the movement of humans southeastward from Beringia down to N. America. The reason that a number of groups went extinct in N. America but lived on in S. America (while there are no notable examples of the opposite pattern) appears to be that the dense rain forests of the Amazon basin and the high peaks of the Andes provided environments that afforded a degree of protection from human predation.Ref_label|E|e|none

outh American invasions of North America

Extant or extinct (†) North American taxa whose ancestors migrated out of South America during the last 10 MaRef_label|F|f|none:

*Cichlids (Cichlidae: e.g. "Herichthys cyanoguttatus") &ndash; freshwater fish that often tolerate brackish conditions
*Virginia Opossum ("Didelphis virginiana")
*Armadillos ("Dasypus novemcinctus", †"Dasypus bellus", †"Pachyarmatherium leiseyi")
*Pampatheres (†"Holmesina") &ndash; large armadillo-like animals
*Glyptodonts (†"Glyptotherium")
*Megalonychid Ground SlothsRef_label|G|g|none (†"Pliometanastes", †"Megalonyx")
*Mylodontid Ground Sloths (†"Paramylodon")
*Megatheriid Ground Sloths (†"Eremotherium", †"Nothrotheriops")
*New World porcupines ("Erethizon dorsatum", †"Erethizon poyeri", †"E. kleini")
*Capybaras (†"Neochoerus pinckneyi", †"Hydrochaeris holmesi")
*Vampire Bats (†"Desmodus stocki", †"D. archaeodaptes")
*Dire Wolf (†"Canis dirus") &ndash; which evolved from earlier N. American migrants
*Cougar ("Puma concolor") &ndash; returning from a S. American refugium after N. American cougars were extirpated in the Pleistocene extinctions [cite journal
title=Genomic Ancestry of the American Puma (Puma concolor)
author= M. Culver, W. E. Johnson, J. Pecon-Slattery, S. J. O'Brien
journal=Journal of Heredity
volume=91
issue=3
pages=186–197
year=2000
doi=10.1093/jhered/91.3.186
url=http://www.coryi.org/Florida_panther/Miscellaneous_Panther_Material/Genomic%20ancestry%20of%20the%20American%20puma.pdf
format = PDF
pmid=10833043]
*Terror Birds (†Phorusrhacidae: †"Titanis walleri")
*Kern Vulture ("Sarcoramphus": †"S. kernensis")
*Hummingbirds (Trochilidae)
*Tanagers (Thraupidae) &ndash; descended from earlier (perhaps Miocene) N. American migrants [cite journal
title=Splendid isolation: historical ecology of the South American passerine fauna
author= R. E. Ricklefs
journal=Journal of Avian Biology
volume=33
issue=3
pages=207–211
year=2002
doi=10.1034/j.1600-048X.2002.330301.x
url=http://www3.interscience.wiley.com/journal/120770689/abstract?CRETRY=1&SRETRY=0 ]
*Tyrant Flycatchers (Tyrannidae)
*Parrots (Arini: "Rhynchopsitta pachyrhyncha", †"Conuropsis carolinensis")

outh American invasions of Central America that failed to penetrate North America

Extant or extinct (†) Central American taxa whose ancestors migrated out of South America during the last 10 MaRef_label|F|f|none:

*Gonyleptid Harvestmen (Opiliones: Gonyleptidae)
*Electric Knifefishes (Gymnotiformes)
*Caeciliid Caecilians ("Caecilia", "Dermophis", "Gymnopis", "Oscaecilia") &ndash; snake-like amphibianscite journal
title = Molecular Evidence for the Early History of Living Amphibians
author = Feller, A. E. and [http://evo.bio.psu.edu/hedgeslab/People/sbh.htm Hedges, S. B.]
journal = Molecular Phylogenetics and Evolution
volume = 9
issue = 3
pages = 509–516
month = June | year = 1998
doi = 10.1006/mpev.1998.0500]
*Poison Dart Frogs (Dendrobatidae)
*Boine Boas (Boidae: Boinae)
*Spectacled Caiman ("Caiman crocodilus") [cite journal
last = Taplin
first = L. E.
authorlink =
coauthors = Grigg, G. C.
title = Historical Zoogeography of the Eusuchian Crocodilians: A Physiological Perspective
journal = American Zoologist
volume = 29
issue = 3
pages = 885-901
publisher = Oxford University Press
location =
date = 1989
url = http://icb.oxfordjournals.org/cgi/content/abstract/29/3/885
doi = 10.1093/icb/29.3.885
id =
accessdate = 2008-09-29]
*other Opossums (Didelphidae) &ndash; 12 additional extant species, listed on
*Northern Naked-tailed Armadillo ("Cabassous centralis")
*Hoffmann's Two-toed Sloth (Megalonychidae: "Choloepus hoffmanni")
*Three-toed Sloths (Bradypodidae: "Bradypus variegatus", "B. pygmaeus")
*Silky Anteater (Cyclopedidae: "Cyclopes didactylus")
*other Anteaters (Myrmecophagidae: "Myrmecophaga tridactyla", "Tamandua mexicana")
*Toxodontids (†"Mixotoxodon") &ndash; a rhino-sized notoungulate
*Rothschild's and Mexican Hairy Dwarf Porcupines ("Coendou rothschildi", "Sphiggurus mexicanus")
*other Caviomorph Rodents (Caviomorpha) &ndash; 9 additional extant species, listed on
*Platyrrhine Monkeys (Platyrrhini) &ndash; up to 10 extant species, listed on
*other Vampire Bats (Desmodontinae) &ndash; all 3 extant species
*Toucans (Ramphastidae)
*Tinamous (Tinamidae)
*Great Curassow ("Crax rubra")

North American invasions of South America

Extant or extinct (†) South American taxa whose ancestors migrated out of North or Central America during the last 10 MaRef_label|F|f|none:

*Lungless SalamandersRef_label|H|h|none ("Bolitoglossa" [cite journal
title= Molecular diversification of salamanders of the tropical American genus "Bolitoglossa" (Caudata: Plethodontidae) and its evolutionary and biogeographical implications
author = Parra-Olea, G., Garcia-Paris, M. and Wake, D. B.
journal = Biological Journal of the Linnean Society
volume = 81
issue = 3
pages= 325–346
year= 2004
url= http://repositories.cdlib.org/postprints/159/
accessdate = 2008-01-11
doi= 10.1111/j.1095-8312.2003.00303.x] , "Oedipina")
*Coral Snakes ("Leptomicrurus", "Micrurus") [cite journal
title= Phylogenetic Relationships of Elapid Snakes Based on Cytochrome b mtDNA Sequences
author = Slowinski, J. B. and [http://www.anu.edu.au/BoZo/keogh.html Keogh J. S.]
journal = Molecular Phylogenetics and Evolution
volume = 15
issue= 1
pages= 157–164
month= April | year= 2000
url= http://www.ingentaconnect.com/content/ap/fy/2000/00000015/00000001/art00725
doi = 10.1006/mpev.1999.0725
accessdate = 2007-12-29] [cite journal
title= The Phylogenetic Relationships of Asian Coral Snakes (Elapidae: Calliophis and Maticora) Based on Morphological and Molecular Characters
author = Slowinski, J. B., Boundy, J. and Lawson, R.
journal = Herpetologica
volume = 57
issue= 2
pages= 233–245
month= June | year= 2001
url= http://www.jstor.org/stable/3893186
accessdate = 2007-12-29
doi=
format= abstract]
*South American Rattlesnake ("Crotalus durissus") [cite journal
title= A Quantitative Analysis of the Ancestral Area of Rattlesnakes
author = Place, A. J., Abramson, C. I.
journal = Journal of Herpetology
volume = 38
issue= 1
pages= 152–156
year= 2004
doi = 10.1670/103-03N]
*Lanceheads ("Bothrops")
*Bushmasters ("Lachesis")
*other Pit Vipers ("Bothriechis schlegelii", "Bothriopsis", "Porthidium") [cite journal
title= Molecular Systematics and Biogeographical History of Pit Vipers as Determined by Mitochondrial Ribosomal DNA Sequences
author = Parkinson, C. L.
journal = Copeia
volume = 3
pages= 576–586
year= 1999
url = http://www.jstor.org/sici?sici=0045-8511%2819990802%293%3A1999%3A3%3C576%3AMSABHO%3E2.0.CO%3B2-Z&origin=crossref
doi= 10.2307/1447591
format= ]
*Small-eared Shrews ("Cryptotis") &ndash; only present in NW S. America: Colombia, Venezuela, Ecuador, Peru
*Geomyid Pocket Gophers ("Orthogeomys thaeleri") &ndash; one species, in Colombia
*Heteromyid Mice ("Heteromys") &ndash; only present in NW S. America: Colombia, Venezuela, Ecuador
*Cricetid &ndash; primarily Sigmodontine &ndash; Rats and Mice (Cricetidae: Sigmodontinae)
*Tree Squirrels ("Sciurus", "Microsciurus", "Sciurillus")
*Cottontail Rabbits ("Sylvilagus brasiliensis", "S. floridanus", "S. varynaensis)
*Tapirs ("Tapirus bairdii", "T. pinchaque", "T. terrestris")
*Equids (†"Plesippus", †"Hippidion")
*Peccaries ("Tayassu pecari", "Catagonus wagneri", "Pecari tajacu", "P. maximus")
*Deer ("Odocoileus", "Blastocerus", "Ozotoceros", "Mazama", "Pudu", "Hippocamelus")
*Camelids ("Lama glama", "L. guanicoe", "Vicugna pacos", "V. vicugna")
*Gomphotheres (†"Cuvieronius hyodon", †"Stegomastodon"Ref_label|I|i|none "waringi", †"S. platensis" [Citation
first = J. L.
last = Prado
author-link =
first2 = M. T.
last2 = Alberdi
first3 = B.
last3 = Azanza
first4 = B.
last4 = Sánchez
first5 = D.
last5 = Frassinetti
editor-last = Cavarretta
editor-first = G.
editor2-last = Gioia
editor2-first = P.
editor3-last = Mussi
editor3-first = M.
editor4-last = Palombo
editor4-first = M. R.
contribution = The Pleistocene Gomphotheres (Proboscidea) from South America: diversity, habitats and feeding ecology
contribution-url = http://www.cq.rm.cnr.it/elephants2001/pdf/337_340.pdf
title = The World of Elephants - Proceedings of the 1st International Congress, Rome October 16-20 2001
year = 2001
pages = 337-340
place = Rome
publisher = Consiglio Nazionale delle Ricerche
url = http://www.cq.rm.cnr.it/elephants2001/atti_en.htm
doi =
id = ISBN 88-8080-025-6
accessdate = 2008-07-25] ) &ndash; elephant relatives
*Otters ("Lontra", "Pteronura")
*other Mustelids (Mustelinae: "Eira", "Galictis", "Lyncodon", "Mustela")
*Hog-Nosed Skunks ("Conepatus chinga", "C. humboldtii", "C. semistriatus")
*Procyonids ("Procyon", "Nasua", "Nasuella", "Potos", "Bassaricyon")
*Short-Faced Bears (Tremarctinae: "Tremarctos ornatus", †"Arctotherium brasilense", †"A. latidens")
*Wolves (†"Canis ambrusteri", †"C. dirus")
*Gray FoxRef_label|J|j|none ("Urocyon cinereoargenteus") &ndash; only present in NW S. America: Colombia, Venezuela
*other Canids ("Atelocynus", "Cerdocyon", "Lycalopex", "Chrysocyon", "Speothos")
*small Felids ("Leopardus") &ndash; all 9 extant species (e.g. "L. pardalis", "L. wiedii")
*Cougar ("Puma concolor") and Jaguarundi ("P. yaguarondi)"
*Jaguar ("Panthera onca")
*American Lion (†"Panthera leo atrox")
*Scimitar Cats (†"Homotherium") &ndash; known so far only from Venezuela [cite web
last = Sanchez
first = Fabiola
authorlink =
coauthors =
title = Saber-toothed Cat Fossils Discovered in Venezuela
work =
publisher = Associated Press
date = 2008-08-22
url = http://www.livescience.com/animals/080822-ap-cat-fossils.html
format =
doi =
accessdate = 2008-08-30] [cite web
last = Orozco
first = José
authorlink =
coauthors =
title = Sabertooth Cousin Found in Venezuela Tar Pit -- A First
work = [http://news.nationalgeographic.com/news/index.html National Geographic News]
publisher = National Geographic Society
date = 2008-08-22
url = http://news.nationalgeographic.com/news/2008/08/080822-scimitar-cat.html
format =
doi =
accessdate = 2008-08-30]
*Saber-Toothed Cats (†"Smilodon gracilis", †"S. fatalis", †"S. populator")
*Trogons ("Trogon") [cite journal
last = Dacosta
first = J. M.
authorlink =
coauthors = Klicka, J.
title = The Great American Interchange in birds: a phylogenetic perspective with the genus "Trogon"
journal = Molecular Ecology
volume = 17
issue =
pages = 1328–1343
publisher = Wiley InterScience
location =
date = 2008-02-21
url = http://www3.interscience.wiley.com/journal/119411407/abstract?CRETRY=1&SRETRY=0
doi = 10.1111/j.1365-294X.2007.03647.x
id =
accessdate = 2008-07-21]

Notes

1. Note_label|A|a|none North American gopher tortoises are most closely related to the Asian genus "Manouria".
2. Note_label|B|b|none An alternative explanation blames climatic and physiographic changes associated with the uplift of the Andes.
3. Note_label|C|c|none Of the 6 families of North American rodents that did not originate in South America, only beavers and mountain beavers failed to migrate to S. America. (However, introduced beavers have become serious pests in Tierra del Fuego.)
4. Note_label|D|d|none Of the 11 extant families of South American cavimorph rodents, 5 are present in Central America; only 2 of these, Erethizontidae and Caviidae, ever reached North America. (The nutria/coypu has been introduced to a number of N. American locales.)
5. Note_label|E|e|none A number of recently extinct North American (and in some cases also South American) taxa such as tapirs, equids, camelids, saiga antelope, proboscids, dholes and lions survived in the Old World, probably mostly for different reasons (the tapir being a likely exception). Old World herbivores may in many cases have been able to learn to be vigilant about the presence of humans during a more gradual appearance (by development or migration) of advanced human hunters in their ranges. In the cases of predators, the Old World representatives in at least some locations would thus have suffered less from extinctions of their prey species. In contrast, the musk ox represents a rare example of a megafaunal taxon that recently went extinct in Asia but survived in remote areas of arctic N. America (its more southerly-distributed relatives such as Harlan's musk ox and the shrub ox were less fortunate).
6. Note_label|F|f|none This listing currently has fairly complete coverage of nonflying mammals. but only spotty coverage of other groups. Crossings may have been made before 10 Ma ago by some fish, arthropods, waif-dispersing amphibians and reptiles, and flying bats and birds. Taxa listed as invasive did not necessarily cross the isthmus themselves; they may have evolved in the adopted land mass from ancestral taxa that made the crossing.
7. Note_label|G|g|none While all megalonychid ground sloths are extinct, extant two-toed tree sloths are from the same family. Three-toed tree sloths, in contrast, are not closely related to any of the groups of extinct ground sloths.
8. Note_label|H|h|none Salamanders may have dispersed to South America more than 10 Ma ago. Nevertheless, the salamander fauna of S. America, which is restricted to the tropical region, consists of only 2 clades, and has fewer species and is far less diverse than that of much smaller Central America. Salamanders are believed to have originated in northern Pangea, perhaps not long before it separated to become Laurasia, and are not present anywhere else in the southern hemisphere (see the [http://en.wikipedia.org/wiki/
   ] ). In contrast, caecilians have a mostly Gondwanan [http://en.wikipedia.org/wiki/
   ] .
9. Note_label|I|i|none Not to be confused with the American mastodon (†"Mammut americanum"), a proboscid from a different family whose remains have been found no further south than Honduras. [Citation
   first = O. J.
   last = Polaco
   author-link =
   first2 = J.
   last2 = Arroyo-Cabrales
   first3 = E.
   last3 = Corona-M.
   first4 = J. G.
   last4 = López-Oliva
   editor-last = Cavarretta
   editor-first = G.
   editor2-last = Gioia
   editor2-first = P.
   editor3-last = Mussi
   editor3-first = M.
   editor4-last = Palombo
   editor4-first = M. R.
   contribution = The American Mastodon "Mammut americanum" in Mexico
   contribution-url = http://www.cq.rm.cnr.it/elephants2001/pdf/237_242.pdf
   title = The World of Elephants - Proceedings of the 1st International Congress, Rome October 16-20 2001
   year = 2001
   pages = 237-242
   place = Rome
   publisher = Consiglio Nazionale delle Ricerche
   url = http://www.cq.rm.cnr.it/elephants2001/atti_en.htm
   doi =
   id = ISBN 88-8080-025-6
   accessdate = 2008-07-25]
10. Note_label|J|j|none Not to be confused with the South American gray fox.

References

External links

* [http://www.wku.edu/~smithch/biogeog/SIMP1950.htm History of the Fauna of Latin America by George Gaylord Simpson (1950)]