Plants

Devonian Period (517-354 MYA)

Plant Proliferation

Plants began spreading beyond the wetlands during the Devonian, with new types developing that could survive on dry land. Toward the end of the Devonian the first forests arose as stemmed plants evolved strong, woody structures capable of supporting raised branches and leaves. Some Devonian trees are known to have grown 100 feet (30 meters) tall. By the end of the period the first ferns, horsetails, and seed plants had also appeared.

Plants during the Devonian Period

The genus Prototaxites describes terrestrial organisms known only from fossils dating from the Silurian and Devonian, approximately 420 to 370 million years ago. Prototaxites formed large trunk-like structures up to 1 metre (3 ft) wide, reaching 8 metres (26 ft) in height, made up of interwoven tubes just 50 micrometres (0.0020 in) in diameter. Whilst traditionally very difficult to assign to an extant group of organisms, current opinion is converging to a fungal placement for the genus. It might have had an algal symbiont, which would make it a lichen rather than a fungus in the strict sense.An opposing view has been presented that Prototaxites was not a fungus but consisted of enrolled liverwort mats with associated cyanobacteria and fungal tubular elements.

Plants during the Devonian Period

Archaeopteris is an extinct genus of tree-like plants with fern-like leaves

Carboniferous Period (354-290 MYA)

Description

Plants during the Carboniferous Period

The Equisetales is an order of pteridophytes with only one living genus Equisetum (horsetails), of the family Equisetaceae

Fossil leaves and branches of the species Sphenophyllum miravallis

Plants during the Carboniferous Period

The order Polypodiales encompasses the major lineages of polypod ferns, which comprise more than 80% of today's fern species. They are found in many parts of the world including tropical, semitropical and temperate areas.

The Medullosales is an order of pteridospermous seed plants characterised by large radiospermic ovules with a vascularised nucellus, complex pollen-organs, stems and rachises with a dissected stele, and frond-like leaves. Their nearest still-living relatives are probably the cycads.

Plants during the Carboniferous Period

The Lycopodiopsida are a class of plants often loosely grouped as the fern allies. Traditionally, the group included not only the clubmosses and firmosses, but also the spikemosses (Selaginella and relatives) and the quillworts (Isoetes and relatives).

Lepidodendrales (from Gr. "scale tree") were primitive, vascular, arborescent (tree-like) plants related to the lycopsids (club mosses).

Plants during the Carboniferous Period

Cordaitales are an extinct order of woody plants that may have been early conifers, or which may have given rise to the conifers (Pinophyta), ginkgos (Ginkgophyta) and cycads (Cycadophyta). They had cone-like reproductive structures reminiscent of those of modern conifers.

Cycads are seed plants typically characterized by a stout and woody (ligneous) trunk with a crown of large, hard and stiff, evergreen leaves.

Plants during the Carboniferous Period

Lepidodendron — known as scale trees — were a now extinct genus of primitive, vascular, arborescent (tree-like) plant related to the lycopsids (club mosses). They were part of the coal forest flora. They sometimes reached heights of over 30 metres (100 ft), and the trunks were often over 1 m (3.3 ft) in diameter, and thrived during the Carboniferous Period

Permian Period (290-248 MYA)

Description

The Permian period, which ended in the largest mass extinction the Earth has ever known, began about 299 million years ago. The emerging supercontinent of Pangaea presented severe extremes of climate and environment due to its vast size. The south was cold and arid, with much of the region frozen under ice caps. Northern areas suffered increasingly from intense heat and great seasonal fluctuations between wet and dry conditions. The lush swamp forests of the Carboniferous were gradually replaced by conifers, seed ferns, and other drought-resistant plants.

Description

The Permian, however, represented the last gasp for much early prehistoric life. The period, and the Paleozoic era, came to a calamitous close 251 million years ago, marking a biological dividing line that few animals crossed. The Permian extinction—the worst extinction event in the planet's history—is estimated to have wiped out more than 90 percent of all marine species and 70 percent of land animals.

Description

Various theories seek to explain this mass extinction. Some scientists think a series of volcanic eruptions pumped so much debris into the atmosphere that the sun was blocked out, causing a significant drop in temperature and preventing plant photosynthesis, which in turn caused food chains to collapse.

Description

Other scientists point to global climate change, citing evidence for a period of sudden warming and cooling. These rapid extremes of conditions may have meant species were unable to adjust. Other theories include a catastrophic release of methane gas stored under the seabed, triggered by earthquakes or global warming, or a massive asteroid impact.

Plants during the Permian Period

Sigillaria is a genus of extinct, spore-bearing, arborescent (tree-like) plants

Plants during the Permian Period

Glossopteris, (meaning "tongue", because the leaves were tongue-shaped) is the largest and best-known genus of the extinct order of seed ferns known as Glossopteridales

Ginkgo

Mass Extinction