Fossil Representative of Rhode Island
Horsetail (common name) Sphenopsida (scientific name) STATUS Unofficial DESCRIPTION Sphenopsida is a class of seedless vascular plants that typically grow in wet climates. They belong to the taxonomic division of ferns. The members of the class, which is also known as Equisetopsida, reached their peak in number and diversity in the Carboniferous period (300 to 355 million years ago) of the Paleozoic era, but most species became extinct by the end of that era (251 million years ago). A single genus, Equisetum, commonly called horsetails, survives today as a modern representative of these primitive plants. REPRESENTATIVE OF THE STATE Sphenopsida were most abundant and diverse in the Carboniferous period, which is also when the majority of the coal deposits on earth formed. This coal formation gave the period, which occurred approximately 300 to 359 million years ago, its name. Rhode Island’s Narragansett Basin formed at this time, and Sphenopsid fossils are preserved there. In addition, these fossils can be found in lakebeds and riverbeds bordering coal swamps. The old coalmines of Portsmouth, Rhode Island, as well as the Rhode Island geological formation that reaches into Massachusetts, contain excellent Pennsylvanian-age fossil specimens of these primitive ferns. Although Rhode Island has not selected an official state fossil, Sphenopsida are among the most common fossil plants in the state, and as such, represent the state’s geology and paleontology well. NAME ORIGIN Carl Adolph Agardh, a Swedish botanist, professor, and bishop, named the class Equisetopsida. This name was derived from the Latin words equus, which means "horse," and seta, which means "bristle." The modern members of this class are commonly called horsetails. The word Sphenopsida is derived from the Greek word σφήνα (sfina), which means "wedge;" -psida is the suffix for certain classes of plants. Early fossil forms such as the genus Sphenophyllum had broad, wedge-shaped leaves. BIOLOGY/ANATOMY Paleozoic Sphenopsida stems were straight, hollow, ribbed, and segmented. The plants’ small leaves or needles were arranged in whorls. These tall ferns grew up to 32 feet (10 m) in height, and some reached as high as 100 feet (30 m). Sphenopsida lived on sandy seafloors, where it sprouted spores from underground rootstalks rather than reproducing from seeds. EVOLUTION/EXTINCTION Sphenopsida are known mainly from fossil species, which date back as far as 360 to 385 million years ago in the late Devonian period of the Paleozoic era. The Devonian period was extremely important in the evolution of plants. During this geologic period, plants, which had been on Earth for almost a hundred million years, gained leaves, roots, and seeds for the first time. They also diversified greatly, growing tall and strong enough to create the first forests. Sphenopsida featured prominently in the understory of the new forests of the Paleozoic era. This class of seedless plants diversified throughout the Carboniferous period to the mid-Permian period, after which most species of Sphenopsida became extinct. INTERESTING FACTS Although large quantities of horsetail can be poisonous to grazing animals, field horsetail is cooked and eaten by humans in Japan and elsewhere. The dish, called tsukushi in Japanese, is described as being similar to asparagus. Tsukushi is rich in several vitamins and essential elements. It has also been said to help prevent various degenerative diseases.
	Click to enlarge an image Clump of Horsetail Horsetail Illustration CLASSIFICATION Kingdom: Plantae Division: Pteridophyta Class: Sphenopsida
	Author: World Trade Press