Paleogene Land Mammal Faunas of South America; a response to global climatic changes and indigenous floral diversity

MIKEL WOODBURNE; FRANCISCO GOIN; MARIANO BOND; ALFREDO CARLINI ; JAVIER JELFO; GUILLERMO LÓPEZ; ARI IGLESIAS; ANA ZIMICS

JOURNAL OF MAMMALIAN EVOLUTION

SPRINGER

Lugar: Berlin; Año: 2013 vol. 21 p. 1 - 73

1064-7554

An appraisal of Paleogene floral and land mammal faunal dynamics in South Americasuggests that both biotic elements responded at rate and extent generally comparable to thatportrayed by the global climate pattern of the interval. A major difference in the SouthAmerican record is the initial as well as subsequent much greater diversity of both Neotropicaland Austral floras relative to North American counterparts. Conversely, the concurrent mammalfaunas in South America did not match, much less exceed, the diversity seen to the north. Itappears unlikely that this difference is solely due to the virtual absence of immigrants subsequentto the initial dispersal of mammals to South America, and cannot be explained solely by thedifferent collecting histories of the two regions. Possible roles plalyed by non-mammalianvertebrates in niche exploitation remain to be explored.The Paleogene floras of Patagonia and Chile show a climatic pattern that approximatesthat of North America, with an increase in both Mean Annual Temperature (MAT) and MeanAnnual Precipitation (MAP) from the Paleocene into the Early Eocene Climatic Optimum(EECO), although the Paleocene-Eocene Thermal Maximum (PETM) is not recognized in theavailable data set. Post-EECO temperatures declined in both regions, but more so in the norththan the south which also retained a higher rate of precipitation.The South American Paleogene mammal faunas developed gradual, but distinct, changesin composition and diversity as the EECO was approached, but actually declined somewhatduring its peak, contrary to the record in North America. At about 40 Ma a post-EECO declinewas recovered in both hemispheres, but the South American record achieved its greatest diversitythen, rather than at the peak of the EECO as in the north. This post-EECO faunal turnoverapparently was a response to the changing conditions when global climate was deteriorating toward the Oligocene. Under the progressively more temperate to seasonally arid conditions inSouth America, this turnover reflected a major change from the more archaic, and more tropicalto subtropical-adapted mammals, to the beginning of the ultimately modern South Americanfauna, achieved completely by the Eocene-Oligocene transition. Interestingly, hypsodonty wasachieved by South American cursorial mammals about 15 ? 20 m.y. earlier than in NorthAmerica. In addition to being composed of essentially different groups of mammals, those of theSouth American continent seem to have responded to the climatic changes associated with theECCO and subsequent conditions in a pattern that was initially comparable to, but subsequentlydifferent from, their North American counterparts.