Biology Reference
In-Depth Information
tropical rain forest in the southeast. Locally there were continuing versions
of the freshwater herbaceous bog/marsh/swamp ecosystem ( Equisetum , Ly-
copodium , Selaginella ; possibly some marsh grasses by the Paleocene), and
versions of the aquatic ecosystem ( Isöetes , Azolla , Salvinia , Trapago from the
Cretaceous; Nelumbo , Porosia added in the early Eocene). As noted previ-
ously, there must have been some beach/strand/dune vegetation of fi brous-
rooted plants suitable for the shifting sandy substrate because grasses were
present in North America by the Eocene (Paleocene to possibly Cretaceous
elsewhere). Brackish-water coastal habitats also existed, but Rhizophora
would not appear until the middle Eocene; so mangrove-habitat plants in-
cluded some ferns (like the present-day mangrove fern Acrostichum ), pos-
sibly some grasses, and palms. The Old World mangrove palm Nypa was
present in the Late Cretaceous and Paleocene of the New World (Maracaibo
Basin/Caribbean region, Germeraad et al. 1968; Colombia, Gomez-Navarro
et al. 2009). It expanded to its maximum distribution in the warm interval
of the Eocene (e.g., to the southeastern United States as the pollen type
Spinozonocolpites , Frederiksen 1988; in south Texas as Nypa , Westgate and
Gee 1990), and disappeared from the New World in the late Eocene. Only
individual elements of a coniferous forest ( Pinus ), grassland, and drier veg-
etation like shrubland/chaparral-woodland-savanna—possibly represented
by other species of Pinus , grasses, and Quercus —were present in northern
North America at the end of the early Eocene. There is no paleobotanical
evidence for desert ( Ephedra was present as an element), tundra, or alpine
tundra as communities. The principal difference between the ecosystems
of North America north of Mexico in the early Eocene and those in the
Middle to Late Cretaceous was that in the early Eocene various modern-
ized forms of a tropical rain forest reached their maximum extent, while,
in contrast, early versions of the deciduous forest, as a community, had the
most limited distribution of its entire history.
MEXICO, THE ANTILLES, CENTRAL AMERICA
Cretaceous, Paleocene, and early Eocene fl oras are few in Mexico, the An-
tilles, and Central America because the land diminishes toward the south;
furthermore, the region was still being assembled from terranes or by uplift,
and much of it was inundated by the high seas. In Mexico the La Misión
and Rosario fl oras are Campanian (Late Cretaceous) in age and grew on the
north coast of Baja California when that land was still part of a volcanic is-
land arc off midcoastal Sonora. These small fl oras include Araucaria , related
to the Southern Hemisphere Norfolk Island pine or monkey-puzzle tree and
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