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Figure 7.
Biostratigraphy of the 10 taxa of land mammals found in the Gaillard Cut Local Fauna in
the Culebra and Cucaracha formations, Panama, based on the North American Land Mammal Age
of their conspecific taxa in North America.
from a very high volcanic mountain range (1,400-4,000 m), suggesting that this
peninsula had very high relief (Retallack and Kirby, 2007). Shallowing to outer neritic
depths in the northerly peripheral Limon and Bocas del Toro basins (Coates et al.,
2003, 2004) (Figure 1) is also consistent with the continuing emergence of a Central
American Peninsula to the south of these basins by the middle Miocene. In addition,
the stratigraphically higher Gatun Formation, which is exposed in the northern part of
the Panama Canal Basin, contains fossil benthic foraminifera that have a strong
Caribbean affi nity, indicating an effective biogeographic barrier between Caribbean
and Pacifi c surface water in the middle to late Miocene (Collins et al., 1996), which
further suggests that a peninsula existed during this time. Although we do not have
evidence for a direct land connection between Panama and North America after
