Katsura Tree

Associated Smithsonian Expert: William A. DiMichele, Ph.D.

Bill DiMichele in an underground coal mine in Indiana looking at 9-foot long stem of an extinct seed-fern (Medullosa sp.)

Courtesy of Scott Elrick, Illinois State Geological Survey

Dr. Bill DiMichele is a research paleontologist at the Smithsonian National Museum of Natural History. He specializes in the study of late Paleozoic and early Mesozoic plants, those living between about 230 and 350 million years ago. His work mainly examines the morphological evolution of these plants, their ecologies, and evolutionary relationships. Much of his work is about how tropical ecosystems of these ancient times responded to major climatic changes experienced by the Earth. DiMichele grew up in southern New Jersey, on the Atlantic coastal plain, and never saw (or remembers seeing) an actual fossil until graduate school. Inspired by professors at his undergrad institution, Drexel University, in Philadelphia, he pursued graduate studies in the paleobotany of coal-forming environments at the University of Illinois, Champaign-Urbana, finishing his Ph.D. in 1979. He joined the faculty of the Botany Department at the University of Washington and then came to the the Smithsonian in 1985. Working with scientists at many other institutions throughout the world, DiMichele’s studies have taken him to many parts of the United States and Europe for fieldwork and to examine collections in other museums.

Meet our associated expert

This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws.

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Fossil flower from Green River Formation dated to the early Eocene
Photo by Smithsonian Institution, Department of Paleobiology

About Flowering Plants (Magnoliophyta): Paleobiology

Flowering plants (or angiosperms) are the dominant group of plants today, but newcomers compared to others. The earliest, clear evidence of angiosperms is from the Cretaceous (about 100 million years ago). Classifying the earliest angiosperm fossils is difficult because they tend to be leaves and pollen, rather than flowers that would permit conclusive identification. Competing theories explain angiosperm origins: that they lived in disturbed areas along stream corridors from which they invaded lowland habitats; that they began as understory plants in dark forests; that they originated in coastal areas and moved inland; or that they started as aquatic plants. Questions about angiosperm origins led Charles Darwin to describe their origins as an abominable mystery. After they appeared on the scene, angiosperms gradually and then rapidly replaced conifers and seed ferns in ecosystems. Advantages may have been faster reproductive cycles, their intimate relationship with insects for pollination, large photosynthetic leaves, and improved systems to transport water and nutrients. Which combination of characteristics allowed angiosperms to become so successful is a question of continuing debate for paleobotanists.

Fossil palm frond
Photo by Department of Paleobiology, Smithsonian

About Plants (Kingdom Plantae): Paleobiology

Plants on Earth began life in the water. The earliest plants were aquatic algae, living in the warm seas more than 500 million years ago. By the Silurian and possibly the latest Ordovician (as much as 440 million years ago), plant life on land had begun. While terrestrial plants had more access to sunlight, challenges included supporting their weight and distributing water throughout their tissues. During the Devonian explosion (55 million years, which is brief in geologic time), plants evolved from small, simple forms to a huge variety of larger, complex forms adapted to life on land. Club mosses, horsetails, ferns, and probably sphenopsids originated. The incredible seed, which safely packages the developing plant embryo, also evolved. Plants extended their reach underground with root systems, providing the anchor and water supply to support large trees. Although plants were to undergo many changes over time, by the end of the Devonian (the golden age of plant evolution), the groundwork had been laid for the terrestrial ecosystems of today.