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NPS photo by Jacob Holgerson.
Introduction
Plants are one of the most abundant and diverse groups of organisms on Earth. Like fungi, protists, invertebrates, and vertebrates, plants are eukaryotes. What distinguishes them from these other groups are rigid cell walls around each cell and their ability to produce their own food by capturing light and converting it into sugar, starch, and other foods needed for survival. Some fossils that appear to be from plants date back to the Ordovician, but the first unquestioned occurrences of plant fossils are from the Late Silurian.
The study of fossil plants is known as paleobotany. Paleobotany is an important aspect of paleontology especially useful for understanding and interpreting ancient ecosystems. Fossil plants range from the most delicate of flowers to the largest of petrified trees and stumps, and include nearly every other part of a plant: leaves, roots, nuts, cones, berries, needles, stems, twigs, seeds, and pollen.
Types of Plants
To learn more, select a type of plant:
While walking through a bog or along a stream bank, you may have pulled apart the finely ribbed stems of horsetails or scouring rushes at their joints. These jointed plants and their relatives have whorls of leaves or branches at the stem joints. Much smaller today, they once grew like trees in coal-forming swamps during the Pennsylvanian Period, though they appeared during the Devonian Period. You can find fossil horsetails at Grand Canyon and Petrified Forest national parks in Arizona and New River Gorge National River in West Virginia.
Ferns are a long-lived group with Devonian representatives and modern relatives. Then as now they lived in humid environments. Ferns differ from lycophytes in having true leaves, and from seed plants such as angiosperms in lacking seeds. Ferns reproduce by means of minute spores, which form in clusters on the undersides of their large, many-divided leaves called fronds.
Although many ferns are low herbaceous plants, they have periodically attained the dimensions of trees; forests of such tree ferns exist today in humid regions such as New Zealand. Large ferns were present as early as the Late Devonian and different genera as large or larger were significant components of forests during the Pennsylvanian Period. The Pennsylvanian Hermit Shale in Grand Canyon National Park in Arizona preserves many fossil ferns as does the Jurassic Morrison Formation at Dinosaur National Monument in Colorado and Utah.
Although many ferns are low herbaceous plants, they have periodically attained the dimensions of trees; forests of such tree ferns exist today in humid regions such as New Zealand. Large ferns were present as early as the Late Devonian and different genera as large or larger were significant components of forests during the Pennsylvanian Period. The Pennsylvanian Hermit Shale in Grand Canyon National Park in Arizona preserves many fossil ferns as does the Jurassic Morrison Formation at Dinosaur National Monument in Colorado and Utah.
Many of the fern-like fronds in Pennsylvanian rocks belong to an extinct group of plants that share a common ancestor with ferns but are distinct enough to be regarded as an entirely separate group—seed ferns. This name is misleading because they are not ferns at all; rather they are true seed plants. Seed ferns were generally bushy shrubs; however, some may have been climbers or robust enough to form small trees (Fortey 1991). The oldest known seed plant is a seed fern from Late Devonian time. Seed ferns have been fossilized as part of the Pennsylvanian Hermit Shale at Grand Canyon National Park in Arizona and the Pennsylvanian Pocahontas Formation at New River Gorge National Park & Preserve in West Virginia. A seed fern (Neuropteris pocahontas) at New River Gorge serves as a boundary marker between earlier Mississippian and later Pennsylvanian rock layers.
Today conifers are as varied and successful a group of plants as they ever have been. Conifers are cone-bearing plants with blade-like leaves such as pines, firs, cypresses, redwood, and spruces. They are an ancient group with ancestors from Pennsylvanian Period forests (Fortey 1991). No other group of organisms of such antiquity has retained an unbroken hold over vast areas of Earth’s surface.
The best known conifer fossils in the National Park System are the large silicified logs in Petrified National Park in Arizona. Florissant Fossil Beds National Monument and Yellowstone National Park also have extraordinary examples of petrified trees and wood. More recent conifer specimens in the National Park System include an 800,000-year-old pinecone from Valley Forge National Historical Park in Pennsylvania.
The best known conifer fossils in the National Park System are the large silicified logs in Petrified National Park in Arizona. Florissant Fossil Beds National Monument and Yellowstone National Park also have extraordinary examples of petrified trees and wood. More recent conifer specimens in the National Park System include an 800,000-year-old pinecone from Valley Forge National Historical Park in Pennsylvania.
During the Triassic, Jurassic, and Cretaceous periods, forests contained large numbers of trees and shrubby plants that looked like palm trees, with large divided leaves and pineapple-like trunks. These were cycads. Cycads had their heyday during the Mesozoic Era, but a small number of cycads survive in tropical and subtropical regions today. Petrified Forest, Arches, and Canyonlands national parks contain cycad fossils, but they are much less conspicuous in the National Park System today than they were in the 1920s and 1930s at Fossil Cycad National Monument.
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Although prominent during the Triassic, Jurassic, and Cretaceous periods, only a single species (Ginkgo biloba) survives today. Unlike conifers, ginkgos slowly declined in variety since their origin. Ginkgo with its perfect fan-like leaves is an obligatory “living fossil” in botanical gardens today. Ancient ginkgos of Triassic age occur as part of the Chinle Formation in Petrified Forest National Park in Arizona, and the Brushy Basin Member of the Morrison Formation at Dinosaur National Monument in Colorado hosts a gingko leaf locality.
Angiosperms dominate the world of flora today. These so-called flowering plants may be broad-leaved trees, grasses, tiny creeping plants, or showy flowers. Their diversity is truly extraordinary: in tropical forests alone, thousands of species of trees exist.
A good deal of angiosperm diversification probably happened within the last 120 million years. The first known fossils are from the Cretaceous Period, and this group has living relatives. Flower fossils are extremely beautiful, for example from Florissant Fossil Beds National Monument. The Eocene lake deposits at Fossil Butte National Monument in Wyoming also contain fossil flowers, and fossilized cattails are on display at the visitor center there.
A good deal of angiosperm diversification probably happened within the last 120 million years. The first known fossils are from the Cretaceous Period, and this group has living relatives. Flower fossils are extremely beautiful, for example from Florissant Fossil Beds National Monument. The Eocene lake deposits at Fossil Butte National Monument in Wyoming also contain fossil flowers, and fossilized cattails are on display at the visitor center there.
Earliest Plants on Land
Rocks from the Ordovician Period contain evidence that plants began colonizing dry land at this time. Most experts agree that the ancestors of land plants first evolved in a marine environment, then moved into a freshwater environment and finally onto land.First flowering plants
Angiosperms (flowering plants) appeared in the fossil record more than 100 million years ago during the Cretaceous Period. Once they appeared, they quickly became the dominant type of plant life on land and remain so today. The earliest angiosperms evolved from a specialized group of seed ferns. Since their first appearance, angiosperms have adapted to nearly every terrestrial habitat from mountains to deserts, and some have adapted to shallow coastal waters. A few varieties are known as “carnivorous” plants.
Not all flowering plants produce the kinds of blossoms you find in florist shops, but along with enclosed seeds, flowers are a key reproductive feature of angiosperms. The evolution of flowers, which attract pollinators, especially insects, and the evolution of a seed, with a protective coating and a ready supply of nourishment, enabled flowering plants to populate the world. Angiosperm seeds are dispersed widely in many ways: blown by the wind, transported by rivers and streams, carried in burrs that become attached to animal fur (or your socks), or embedded in fleshy fruit that is eaten and later “pooped out.”
Angiosperms have developed an incredible array of colors, scents, and fruits through their intricate and reciprocal relationship with the animal world. Without the abundance and variety of flowering plants (more than 90% of all land-plant species) known today, the world would be a much duller place.
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Featured Parks
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Chaco Culture National Historical Park (CHCU), New Mexico—[CHCU Geodiversity Atlas] [CHCU Park Home] [CHCU npshistory.com]
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Florissant Fossil Beds National Monument (FLFO), Colorado—[FLFO Geodiversity Atlas] [FLFO Park Home] [FLFO npshistory.com]
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Fossil Butte National Monument (FOBU), Wyoming—[FOBU Geodiversity Atlas] [FOBU Park Home] [FOBU npshistory.com]
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Hawai’i Volcanoes National Park (HAVO), Hawai’i—[HAVO Geodiversity Atlas] [HAVO Park Home] [HAVO npshistory.com]
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Petrified Forest National Park (PEFO), Arizona—[PEFO Geodiversity Atlas] [PEFO Park Home] [PEFO npshistory.com]
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Prince William Forest Park (PRWI), Virginia—[PRWI Geodiversity Atlas] [PRWI Park Home] [PRWI npshistory.com]
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Yellowstone National Park (YELL), Idaho, Montana, and Wyoming—[YELL Geodiversity Atlas] [YELL Park Home] [YELL npshistory.com]
Last updated: December 11, 2024