Unformatted text preview: ungulates Extinct Ground Sloths
Toxodon N.A. to S.A. Procyonids
Murids Crossing Over Crossing Over 3 Million Years Ago Middle Pliocene Just before final emergence of the isthmus Last corridors for dispersal of marine organisms between Caribbean Sea & Pacific Ocean Late Pliocene Land Bridge Complete
Mammalian Exchange Reaches Climax Effects of Interchange
Effects of Interchange Exchange uniform at first, becoming unbalanced later
S.A. fauna made little impact in N.A.
N.A. fauna radiated explosively in S.A.
Reasons for imbalance: N.A. fauna longer subjected to repeated immigrations
Better competitors & predators
Webb & Rancy threephase model Threephase Model
Webb & Rancy (1996) First Phase Late Pliocene Just after land bridge formed
Glacial conditions shrunk forests
Allowed Savanna habitats to dominate tropical latitudes
Establishing a corridor for savanna adapted animals Threephase Model
Webb & Rancy (199...
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- Spring '09
- North American Fauna, American Fauna, South American Fauna