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DINOSAURS AND PLANTS
Without plants, there would have been no dinosaurs (or any other land animals).
Plants are at the base of the food web (also called the food chain). Plants convert solar energy (sunlight) into chemical energy, which animals can eat. Plants are called "producers" or autotrophs because of this; they produce the fundamental food energy that all animals use.
Meat-eating animals (carnivores like Tyrannosaurus rex) get their energy by eating other animals, mostly plant-eating animals (herbivores like Triceratops). The herbivores get their energy by eating plants (like cycads). The plants (producers or autotrophs) get their energy from sunlight, converting the light into chemical energy using photosynthesis.
Another amazing thing that plants do is change the composition of the air. Plants actually changed the chemical makeup of the Earth's atmosphere by giving off oxygen and absorbing carbon dioxide. They also contribute to erosion and the creation of soil. Also, since plants are stationary, they determine where plant-eating animals live.
The development of plants was closely tied to the fate of the dinosaurs. Since most dinosaurs were plant-eaters, the nature and amount of available plants dictated whether a plant-eating dinosaur would thrive or die (and indirectly, would even influence the fate of meat-eating dinosaurs). As plants evolved through the Mesozoic Era, their distribution changed drastically, leading to the demise of some dinosaurs and the rise of new types of dinosaurs.
Mesozoic Era Plants
The Mesozoic landscape was very different that the modern-day landscapes. First of all, most of the plants around us today are flowering plants, and these did not evolve until relatively late in the Mesozoic (about 140 million years ago). Second, the Mesozoic Era was much sparser than today in both plant and animal life. There was much less diversity in life forms and fewer individual organisms, although the diversity increased throughout the Mesozoic Era. This Era ended in a huge mass extinction about 65 million years ago.
During the Mesozoic Era, when the dinosaurs lived, conifers dominated the landscape. These slow-growing evergreen trees and shrubs probably constituted the majority of the herbivorous dinosaurs' diets. Conifers were probably important food for dinosaurs, including the large sauropods.
Mesozoic Era conifers included redwoods, yews, pines, the monkey puzzle tree (Araucaria), cypress, Pseudofrenelopsis (a Cheirolepidiacean). Towards the end of the Jurassic period, flowering plants evolved and began to overtake conifers as the dominant flora.
Leptocycas was a cycad, a primitive seed plant from the late Triassic period. It was a palm-like tree with a long, woody trunk and tough leaves. It lived in warm climates. This tree was about 4.8 ft (1.5 m) tall.
Cycadophytes included the Cycads and Cycadeoids (Bennettitales), plants with woody stems (some erect, some spherical) and very tough leaves. These two groups differ mainly in the way they reproduce: Cycads have separate male and female plants; Cycadeoids do not always. Cycadeoids are now extinct but there are still a few cycads. Some Mesozoic Era Cycads included: Leptocycas, Cycas, Zamia, Dioon, Bowenia, Stangeria, and Microcyas. Some Mesozoic Cycadeoids included: Cycadeoidea, Vardekloeftia, Williamsonia, Williamsoniella, Westersheimia, and Leguminanthus.
Williamsonia sewardiana was a cycadeoid (a bennettitalean). It had a woody stem and simple leaves.
Cycadophytes dominated southern areas during the Triassic period and thrived during the Jurassic, but began to decline in the mid-Cretaceous period. Cycadeoids went extinct.
Gingkos (the maidenhair tree, family Gingkoaceae) are deciduous (losing their soft leaves in cold weather) gymnosperms that were common at higher altitudes. Gingkos peaked during the Jurassic and Cretaceous periods. Gingkos are still around today.
Pteridophytes are a group of primitive vascular plants that include Lycopods (club mosses), Sphenopsids (horsetails, shown left), and ferns (shown, right). These plants reproduce with spores that germinate only in moist areas; they also reproduce using rhizomes (underground stems). Pteridophytes evolved during the Devonian and were mostly low-growing during the Mesozoic Era. These fast-growing, resilient plants were a source of food for plant-eating dinosaurs that lived in moist areas.
Horsetails were an important source of nutrition for plant-eating dinosaurs. These primitive vascular plants were fast-growing and resilient (they could propagate using underground runners which a grazing dinosaur wouldn't eat). This meant that a hungry dinosaur could eat the plant without killing it, since the plant would regrow from the rhizome (the underground stem).
Glossopteris, a tree-like seed fern (Pteriosperm) from the Permian through the Triassic Period. It had tongue-shaped leaves and was about 12 ft (3.7 m) tall. Glossopteris was a dominant plant in Gondwana (the southern supercontinent) early in the Triassic period.
Seed ferns (Pteridosperms) had fern-like leaves but bore seeds and not spores. This group included Glossopteris, Dicroidium, Caytonia, Denkania, and Lidgettonia.
Seed ferns dominated southern Pangaea during the Triassic period. Seed ferns went extinct during early in the Cretaceous period. Glossopterids went extinct at the end of the Triassic period.
Flowering plants (angiosperms) evolved about 140 million years ago, during the late Jurassic period and dramatically changed the Earth's landscape, quickly taking over most of the ecological niches. These fast-growing, adaptable plants also gave rise to a HUGE boom in the dinosaur world. Most of the dinosaurs that have been found date from the late Cretaceous period, when flowering plants were suppling plant-eating dinosaurs (like hadrosaurs) with plentiful and nutritious food. Some Mesozoic Era angiosperms included magnolias, laurel, barberry, early sycamores, and palms. Grasses may have evolved later.
THE EVOLUTION OF LAND PLANTS
PANGAEA AND WEATHER DURING THE MESOZOIC ERA
The dinosaurs evolved early in the Mesozoic Era, during the Triassic period (about 228 million years ago). At the start of the Mesozoic Era, the continents of the Earth were jammed together into the supercontinent of Pangaea; this land mass had a hot, dry interior with many deserts. The polar regions were moist and temperate. During the Mesozoic, Pangaea began breaking apart and the weather changed.
Seed plants from the UCMP, Berkeley, CA.
from Prof. Tom Herbert at the University of Miami, FL
Plant Fossil Record from the International Organisation of Paleobotany
Links for Paleobotanists from the Mineralogisches Institut, Universität Würzburg.
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