Table of Contents
The early Angiosperms: Paleophytogeography and Depositional Settings
Introduction
Fossil Record Searches
Fossil Record Searches cont.
Relationships between floodplain deposits
Aquatic Evidence
North American Evidence
Sassafras leaf of the U. Cretaceous of Eastern North America
Koonwarra
PPT Slide
Koonwarra cont.
Koonwarra Angiosperm-like Petal
Antarctica
Nothofagus sp. (White, 1986)
Plausible initial angiosperm radiation patterns
Macro-factors leading to early angiosperm evolution (Wolfe, 1997)
General Radiation Patterns (Wolfe, 1997)
Cretaceous paleoclimate
Late Cretaceous locations & problems
Evolved first in West Gondwana, in the rift valley between the hump of Africa and northern S. America (Retallack and Dilcher, 1981), contact with the Euramerican landmass enabled the first radiating waves of angiosperms to spread into the Northern Hemisphere.
Other theories point to east Gondwanaland, Fiji, and east Asia via Indonesia as origins (Taylor and Taylor, 1993).
PPT Slide
Why herbaceous?
North American
North American Early Angiosperm Morphology
PPT Slide
The Upland Diversification Theory (Axelrod, 1952)
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Oleanane as a biomarker (from Taylor and Hickey, 1996)
Oleanane cont.
Molecular evidence
Molecular evidence cont.
Physiological Factors for Radiation
At higher latitudes the advantages of angiosperm C gain may have been offset by the evergreen habit of conifers, allowing C fixation to continue throughout the year and reducing the large energy expenditure required to re-establish a deciduous canopy at the beginning of the growing season (Beerling, 1994).
Bocherens et al. (1993) dispute this.
Vegetative Morphology
Vegetative Growth & Habit
Cretaceous Terrestrial Community Changes
Ancestral Habitats
Early Cretaceous floras - approx. Berriasian-Barremian (from Hughes, 1976)
Modern Ancestral Habitat Hypothesis
Ancestral Habitats cont.
Proof of this scenario (from Taylor and Hickey, 1996)
As mentioned previously, with high-nutrient habitats, where efficient nutrient retention is unimportant…
Angiosperm exploitation of nutrient-rich environments form the equator to the poles (Taylor and Hickey,1996).
Early Ecological Radiation
Early Ecological radiation
More environmental description
Environments
Wealden Cretaceous Paleoenvironment
A transition from Mesozoic ecosystems dominated by ferns, conifers, cycads and Bennettitales to more modern L. Cretaceous and Tertiary ecosystems dominated by angiosperms (Crane and Lidgard, 1989).
Subsequent radiation
The Tropical Dilemma (Taylor and Hickey, 1996)
Conclusions
More Final Conclusions
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Author: Envrionmental Division
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