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Nigersaurus ate plants – learn
what could have been on
an herbivore’s Mesozoic menu.
Illustrations by Caroline Stromberg
Photographs © Botanics
Only by bringing together plants from around the globe and a variety of modern environments can a dinosaur-age scene be recreated. Some of the plants, like ginkgos, look virtually the same as their extinct ancestors; some, like the conifer Araucaria, were the dominant trees of the forests 110 million years ago. Plant groups alive at the time of the dinosaurs include mosses, horsetails, ferns, tree ferns, cycads, ginkgos, conifers, palms, blooming water lilies and magnolias.
EARLY PLANTS LIVED IN WET ENVIRONMENTS
AND REPRODUCED USING SPORES:
Early land plants inhabited a hot, humid environment. 300 million years ago, many land areas were covered in wet forests of giant clubmoss, horsetails and ferns. These seedless plants reproduce with spores, which require humid environments to survive.
Clubmoss and Horsetails
Horsetails (Equisetum) have a central, hollow stem with whorls of leaves or thin branches. They hold their spores in a cigar-shaped “cone” at the top of the plant. Horsetails date back to ~370 million years ago. During the beginning of the dinosaur era they grew to be nearly 30 feet tall (10m.)
DURING DRIER CLIMATES OF THE MESOZOIC ERA, PLANTS THAT REPRODUCED USING SEEDS DIVERSIFIED
Seasonally dry conditions at the beginning of the Mesozoic (245 million years ago) favored the diversification of plants that reproduced with seeds. Plants such as cycads, ginkgoes and conifers, which had seeds, relied on either wind or animals (insects, reptiles) for pollination and seed dispersal.
Cycads
Modern cycads have short, stout trunks with a bush of long, green, hardy, leaves at the top. As the leaves fall off, their bases create a honeycomb pattern. Mesozoic cycads were more slender and branched and could grow to 45 feet (15 m) tall! Cycads are “dioecious,” (“two houses”), which means plants are either male or female. Unlike modern conifers and ginkgoes, which are pollinated by the wind, many cycads are pollinated by insects.
Cycads today are confined to tropical and warm temperate regions of South America, South Africa, Australia, Mexico, Central America, and parts of eastern Asia. However, they display a wide range of ecological roles: understory in tropical forests, epiphytes, mangroves, fire-tolerant shrubs
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Cycad
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Cycas revoluta, "King Sago" |
Cycas tiatungensis, "Prince Sago" |
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Ginkgoes
Ginkgoes evolved 280 million years ago. Today only a single species survives: Ginkgo biloba. This tree is extinct in the wild except in a few places in China and was “rescued” from extinction by Chinese priests before it came to Europe and North America as an ornamental plant. Ginkgos have distinctive triangular leaves. Ginkgo trees are either male or female. Ginkgo seeds, produced by female plants, are yellow and fleshy and smell like rotting meat! (Which explains the popularity of male trees.)
Ginkgo
© University of California Berkeley
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Conifers
Conifers date back 310 million years, and were the dominant tree of the Mesozoic Era. Today most conifers have needle-like leaves that grow in a spiral or in pairs around the branches. Trees produce both female cones (that produce seeds) and male cones (that produce pollen.) Most conifers are wind pollinated. |
Araucariaceae is an ancient family that dates back to the late Triassic, ~220 million years ago. Araucarians diversified during the Jurassic, when they were present in both the northern and southern hemisphere. They have declined in diversity since the Cretaceous and today there are only two genera, Araucaria and Agathis, which are confined to the southern hemisphere (except Africa). Araucarians can grow very tall, up to 180 feet (60 m) tall. The Petrified Forest in Arizona consists of trunks thought to be Araucarians.
Monkey Puzzle tree (Araucaria araucana): Its name derives from the belief that monkeys would have difficulty climbing it's spiky trunk. Today, it lives primarily on the flanks of the Andes mountaints in Chile and Argentina.
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Conifer |
Araucaria heterophylla, "Norfolk Island Pine" |
Araucaria araucana,
"Monkey Puzzle |
AT THE VERY END OF THE DINOSAUR ERA, FLOWERING PLANTS SUCH AS GRASSES AND BROAD-LEAFED TREES EVOLVED
Flowering plants’ showy petals are thought to be modified stamens which attract insects, birds and other pollinators. Today, flowering plants are extremely diverse; they even inhabit the water (duckweed) and the air (Spanish moss). Some flowering plants are parasitic and even carnivorous! Grasses, which today cover 30% of the Earth’s land surface and provide humans with more than 50% of the carbohydrates we eat (think of corn, rice, bread, cereal…), did not evolve until the latest Cretaceous.
Water lilies
The earliest flowering plants are thought to have been weedy shrubs that lived alongside streams. One of these early groups to evolve was the water lily family.
Magnolias
Magnolias (Magnoliales) were among the first groups of flowering plants to evolve. Fossils of Magnolia-like plants are known from early-mid Cretaceous sediments (Aptian-Albian, ~112 Ma) in North America. Because Magnolia, and many other early flowers have large bisexual flowers with very many floral parts (carpels, stamens) compared to later (more “derived”) groups of flowering plants, it was long thought that this represented the “primitive”(ancestral) condition from which other flower types evolved. Now we know that both very large flowers with numerous parts (such as Magnolia,) and simple flowers with few floral parts, existed among the earliest flowers.
Magnolia
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Paleontologists have suggested a few explanations for why flowering plants evolved at the end of the dinosaur era (~140 Ma):
- The environment during the Cretaceous – which was warm and dry – favored the evolution of flowering plants
- Flowering evolved in conjunction with plant-eating dinosaurs
- Flowering plants evolved in conjunction with insects
It is also possible that flowering plants DID evolve earlier than the late Mesozoic, but the plants were so small and fragile they didn’t fossilize.
Unfortunately, none of these hypotheses are well supported. |
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Species List
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