Archaeopteris

Archaeopteris belongs to the fossil group of the Progymnospermes and is regarded by many scientists as the first modern tree. The kind Archaeopteris has more characteristics common with the Plantes to seeds than any other known fossil plant and the recent cladistic analyzes place it as a group-brother of the Plantes at seeds.

Old : Archaeopteris meets in the layers dating from the higher Dévonien until the lower Carbonifère. Distribution : fossils were found in South Africa, Germany, Australia, Belgium, Canada, China, Colombia, the United States, Ireland, Kazakhstan, Morocco, Russia, Ukraine, Venezuela.

! Not to confuse with Archeopteryx !

History of the kind

The first fossils of Archaeopteris , described at the 19th century, were prints and compressions which resembled slings of ferns. Archaeopteris initially was thus classified in the ferns.

In 1911, Mikhail Zalessky, a Russian paleontologist, described a new type of wood of Dévonien which it names Callixylon . Callixylon resembles the wood of conifers much. Several species are described in Russia, North America and Europe. Some of the specimens are stocks or trunks of big size.

It is into 1960 that the paleobotanist Charles Beck shows connection between Callixylon and Archaeopteris - to start from a specimen whose stem is of type Callixylon and the foliage Archaeopteris . The plant can then be rebuilt as a large tree whose foliage resembles the slings of the ferns and who reproduces by spores. This unknown combination of characters at the current plants involves the creation of the group of the Progymnospermes. As the name Archaeopteris was oldest, it is that which was preserved to indicate the whole plant.

In 1966, Carluccio and its collaborators show that the " frondes" of Archaeopteris are not made up sheets but branches ramified in a plan and which carry simple sheets.

Main features

Port: Archaeopteris is rebuilt as a tree which could reach 30 to 40 m in height. the largest found stocks reach 1.5 m in diameter. Archaeopteris was able to produce adventitious ramifications. The side ramification of Archaeopteris approaches the ramification axillaire which one observes at the Plantes with seeds.

Reproduction: the presence of two types of Spores (hétérosporée reproduction) was shown in several species.

Anatomy: axes of Archaeopteris (=" Callixylon ")have a large central marrow which can exceed 1 cm diameter. The Bois points out that of the Conifères with trachéides and rays. It is produced by a Cambium bifacial. The trachéides relate to their wall radial of the groups of punctuations separated by nonpunctuated zones. The most external fabrics (secondary Phloem e.g.) are seldom preserved and thus badly known.

Ecology

It is thought that Archaeopteris lived in well drained zones where it could form forests. Archaeopteris had a well developed system racinaire which could contribute to the formation of deep grounds in higher Dévonien. This transformation of the grounds could have had an impact on the cycle of carbon with large scales and the climate.

External bonds

file " Dévonien supérieur" with images D ''' Archaeopteris ''

Devonian times: '' Archaeopteris ''

Images

Random links: