Archaeopteris

Radial section of the wood of Archaeopteris ( bar = 1 mm)

Archaeopteris is a fossil species of vascular plants and was for a time the oldest known tree in the true sense. The wood was formerly managed as a separate genus Callixylon, but the genus Archaeopteris is now assigned. The name Archaeopteris in Greek means " ancient fern ".

Features

The wood is very similar to the present-day gymnosperms. The formation of the wood was similar. The strains had a diameter of up to one meter at a height of up to 30 meters. This growth was not only at the growing tip, as usual until then. Archaeopteris also formed lateral buds, and from side shoots that could replace the main drive. Another new feature was the bifacial cambium, which gave inward wood, outward Bast. Here for the first time occurs secondary growth. With this growth form of the tree reached the age of 40 to 50 years.

Also, the root system was more pronounced than in the previously occurring plant. Achieved this a maximum depth of 20 centimeters, handed the root system of Archaeopteris to one meter deep.

In the sheets of the telomerase are found in a fan shape, the fronds were already so extensively. Within the pinnules the telomerase was branched dichotomously, the Telomenden were not fully grown, but partly free or slashed at the edge.

Archaeopteris was throwing leaves: at unfavorable seasons branch systems were dropped: branches with side branches on which sat the leaves. These branches are the most common fossils.

The increase took place via spores. Archaeopteris was heterosporous, so made ​​little male microspores and large female megaspores.

Dissemination

Archaeopteris was spread worldwide. There are localities in North America, Europe, Siberia, China, and the Gondwana continents of Africa, Australia, South America and Antarctica. The Paläobreiten ranging from equatorial to subpolar.

Until their extinction at the transition from the Devonian to Carboniferous in front of around 355 million years Archaeopteris plants formed the main component of the earliest forests.

The temporal distribution of Archaeopteris ranges from the Upper Devonian to Lower Mississippian into.

System

Archaeopteris is the largest genus within the order of Archaeopteridales. This is usually placed today to Progymnospermen, a group that mediates between the ferns and seed plants. This intermediate position corresponding to the features: the conifer -like wood and fern-like leaves and spores.

The genus occurred in the Middle Devonian the first time, was in the Upper Devonian widespread, but died at the end of the Devonian from. It is an index fossil for the Upper Devonian.

Other genera are much less frequent. The diminutive genus Eddya is also interpreted as a seedling of Archaeopteris.

Sources and further information

The article is based on the following sources:

• Archaeopteris in the Devonian Times
• Berkeley