Biology Reference
In-Depth Information
0.5°C/1° latitude, and the steeper trend intensifi ed near the beginning of
the middle Eocene. Between these two sites is the Brandon Lignite of west-
central Vermont, which has been well-known since the 1840s as a source
of fuel for the Brandon Iron and Car Wheel Company. It is important be-
cause there are so few fl oras of Tertiary age in the northeastern United
States. The exact age is diffi cult to determine because it is underlain by
Precambrian quartzite, overlain by Pleistocene drift, and the sediments are
not suitable for radiometric dating. The current estimate is early Miocene
(Tiffney and Traverse 1994). It contains an exceptional assemblage of fruits
and seeds (e.g., Tiffney 1977; Tiffney and Traverse 1994) and pollen (Tra-
verse 1955). Among the fossils are
Carya
,
Castanea
(chestnut),
Ilex
(holly),
Nyssa
,
Quercus
,
Ulmus
, and
Vitis
(grape). In addition, there is a present-day
Asian component of
Glyptostrobus
,
Alangium
,
Engelhardia
,
Pterocarpus
, and
Sargentodoxa
(a deciduous vine of southeastern Asia). Other plants repre-
sented are
Cyrilla
,
Gordonia
,
Persea
, and
Symplocos
, currently of the south-
eastern United States and absent in areas with signifi cant frost. The MAT is
estimated at around 17°C (at present 7.6°C) or intermediate between those
to the far north and in the southeastern United States. It was a mixed de-
ciduous forest and had broad geographic affi nities with Europe and espe-
cially with eastern Asia.
The Eocene vegetation of the Jackson, Clairborne, and Wilcox Group in
southeastern United States is known from early studies by Berry (1916),
and is currently being revised by David Dilcher and colleagues (e.g.,
Dilcher 1973; Dilcher and Lott 2005). The previously reported
Taxodium
has been found to be
Podocarpus
;
Aralia
is
Dendropanax
; and the Proteaceae,
thought to be represented by four species, is not present. The vegetation
in the uplands was a warm-temperate forest trending toward temperate to
cool-temperate forest later in the Oligocene. The lowland vegetation was
deposited in oxbow lakes and other basins varying distances from the coast,
and it was a moist to seasonally dry community later becoming warm-
temperate, with pine forest developing on edaphically dry coastal sands.
The middle Eocene Claiborne Group (Laredo Formation) of south Texas
has shark, skates, rays,
Tarpon
, and Crocodylidae, along with the present-
day Old World mangrove
Nypa
(Westgate and Gee 1990). At this time
Nypa
(fi g. 6.1) also occurred along the Gulf Coast to Florida (Jarzen and Dilcher
2006), and southward to northern South America.
An important development in the modernization of New World ecosys-
tems in middle Eocene and slightly later times was the fi rst appearance
of
Rhizophora
in mangrove communities occupying coastal brackish-water
habitats (Ellison 2008; Graham 1995, 2006). Prior to that time,
Nypa
(
Spi-
