Seed Fern

Associated Smithsonian Expert: Jonathan G. Wingerath, M.F.S.

Jonathan Wingerath working with fossil plant specimens at the National Museum of Natural History

Photo by Smithsonian Institution

Jonathan Wingerath is a Museum Specialist who manages the Paleobotanical collections at the Smithsonian National Museum of Natural History. He grew up in northern New York State and became interested in paleontology as a Geology major at St. Lawrence University. During vacations he explored the fossil bearing outcrops of local Ordovician limestones, finding an occasional trilobite, brachiopod, or crinoid fragment. At Yale, he received his master’s degree in Forest Soils and Hydrology. Between the summers of 1988 and 1989 he was employed by the State of New York to map large sections of the surficial geology in the St. Lawrence Lowlands. He also worked as a Peace Corps volunteer in the Department of Concepcion, Paraguay, teaching agroforestry practices to farmers, public school teachers and their students. Wingerath began his career at the Smithsonian in the Division of Sedimentology, applying his knowledge of geology, soils, and hydrology to projects involving the Nile River, Nile delta, and offshore sedimentation in the Levant region. His current work involves organizing and housing approximately 6.5 million fossil plant specimens, facilitating the work of paleobotanists at the Smithsonian and scientists from all over the world. He also prepares thin-sections of paleontological, biological, and geological materials.

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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Depiction of a late Carboniferous seed fern forest
Photo by Mary Parrish, Smithsonian, National Museum of Natural History

About Seed Ferns (Pteridospermatophyta): Paleobiology

Seed ferns sounds like a contradiction, since modern ferns reproduce with spores, not seeds. It took scientists awhile to understand seed ferns, which flourished in the Carboniferous (about 325 million years ago). Common in wetlands, including coal swamps, they were first classified as ferns because of their large, divided leaves (fronds). The fronds of some seed ferns were huge (7 m, nearly 25 feet) in length, though most were 1-5 meters. In the late 1800s, to the surprise of many, paleobotanists pieced together evidence that they made seeds (sexual reproductive structures). It turns out that seed ferns are more closely related to flowering plants than to ferns. Like flowering plants, seed ferns made pollen, adapted to be spread by wind and maybe insects. Seed ferns diversified during the early Mesozoic, giving rise to new groups. Some had reproductive structures like those of flowering plants and suggesting insect pollinated. By the later Cretaceous (65 million years ago), however, seed ferns began to decline and gradually disappeared from Earth.

What might this fossil leaf tell you about climate?
Photo by Smithsonian Institution, Department of Paleobiology

About Plants (Kingdom Plantae): Prehistoric Climate Change

The great biogeographer Wladimir Peter Koppen once said that plants are crystalized visible climate. He had studied the distribution of modern plants, but there is no reason to believe that ancient plants were not equally sensitive to climate. Indicators of paleoclimate, such as rainfall and surface temperature, can be found in the chemistry of fossil plants and the rocks that surround them. The form of the fossils themselves can also reveal a great deal about climate. For example, plants have tiny openings on their leaves (stomata) through which they absorb CO2 and release oxygen. More stomata occur in low CO2 atmospheres, and fewer in high CO2 environments. Some woody plants have growth rings, showing the alternation of favorable and unfavorable conditions. Leaf shapes can also act as thermometers. Leaves with serrated edges (toothed margins) are more common in cooler climates, whereas smooth-edged leaves dominate in warmer climates. By studying modern forests, and applying the findings to extinct plant communities, past climate conditions can be inferred. Changes in fossil plant assemblages mirror changes in global climate over time.