 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
| Division (Phylum) Pteridophyta or Filicophyta | |
Ferns (division Pteridophyta or Filicophyta) range from the Devonian to recent times. Ferns, like clubmosses and horsetails are vascular plants with true roots, stems, and leaves. While many ferns are smaller herbaceous plants, larger tree-like ferns still exist. The leaves of ferns are formed as fronds. Fronds may be simple or compound and are attached to a vertical stem or underground rhizome by a stipe (which corresponds to the petiole in angiosperms). Compound fronds are sub-divided numerous times into pinnae (singular: pinna), which are attached to a long central axis called the rachis. Pinnae may be subdivided into ultimate units called pinnules, which may be further sub-divided. Ferns like to grow in moist shady places. Like clubmosses and horsetails, ferns require a thin film of water covering their small gametophytes to reproduce sexually. Like clubmosses and horsetails, ferns also reproduce asexually with spores. The spores in clubmosses and horsetails are produced in cones on the sporophyte. In ferns, spores are produced in round structures called sori (sorus: singular) on the underside of pinnules.Tree Ferns Ferns occupied many habitats in the Carboniferous. Fern species grew as epiphytes, ground cover, understory and canopy in these ancient forests. Psaronius was the largest arborescent fern found in the coal measure swamps (Willis & McElvain, 2002, p. 108). Psaronius was up to 10 m tall and occupied the drier areas of the swamps. The trunk had no secondary wood for strength. The center of the trunk was composed of a narrow cylinder of vascular tissue. Enclosing this cylinder was a mantle of leaf petioles and aerial roots, which created a fibrous, tough, lightweight structure (Kenrick & Davis, 2004, p. 71). Today, epiphytes like orchids and bromeliads grown in tree fern root mantles. During the Carboniferous certain species of small ferns and horsetails grew in association with the roots of Psaronius (Rothwell, 2002, p 42).The trunk of Psaronius was unbranched and clothed in a thick mass of descending roots near the bottom. Along the trunk leaf scars marked former positions of fronds. These circular scars are diagnostic of species. At the top, Psaronius bore fronds forming an apical crown. The fronds of Psaronius are known as Pecopteris. Towards the end of the Carboniferous arborescent ferns started to dominate the canopy as the climate became dryer. Science Olympiad Fossil Event The 2010 Science Olympiad Fossil List includes fern-like foliage under the category Ferns. |
|
 Tree Fern Psaronius brasiliensis Bieland, Maranhao Province, Brazil Pedra de Fogo Formation Permian 15 cm x 14.5 cm |
 Tree Fern Titea singularis Bieland, Maranhao Province, Brazil Pedra de Fogo Formation Permian 17 cm x 15 cm |
 Tree Fern Grammatopteris freitasii Bieland, Maranhao Province, Brazil Pedra de Fogo Formation Permian 20 cm x 19.5 cm |
 Tree Fern Dernbachia brasiliensis Bieland, Maranhao Province, Brazil Pedra de Fogo Formation Permian 7.5 cm x 7 cm |
 Tree Fern Guairea carnieri Paraguay, South America Permian 20 cm x 12.5 cm |
 Osmunda Queensland, Australia Jurassic 8.6 cm x 12 cm |
 Fern Stipe Section Acrostichum Green River Formation Eocene Wyoming, USA 1.5 cm diameter x 9 cm long |
 Fern Stipe Section Acrostichum Green River Formation Eocene Wyoming, USA 2 cm diameter x 3 cm long |
 Tree Fern Tempskya Cretaceous Chippy Creek, Idaho 7.5 cm x 6 cm |
 Fern Bud Cyathodendron texanum Eocene South Texas 6 cm x 4.5 cm |
|
 Fern Pinna (Pecopterid Group) Asterotheca sp. Mazon Creek, Illinois Carbondale Formation, Francis Creek Shale Member Paleozoic; Pennsylvanian 10 cm long x 6 cm wide |
Bibliography |
|
| Kenrick,
P. and Davis, P. (2004). Fossil Plants. Smithsonian
Books: Washington. Rothwell, G.W. (2002). Coal Balls: Remarkable Evidence of Palaeoxoic Plants and the Communities in Which They Grew. . In Dernbach, U. & Tidwell, W.D. Secrets of Petrified Plants: Fascination from Millions of Years (pp. 39-47). Germany: D’ORO Publishers. Willis, K.J. & McElwain, J.C. (2002). The Evolution of Plants. New York: Oxford Univeristy Press. |
|
