|Evolution of plants
ferns The oldest
Four very old plants Parka Myriapods Crock Hey (Seed) ferns Scorpion Lepidodendron Sigillaria Calamites
Wood of Calamites Cordaites The leaf of Neuropteris Little animals Graissessac Psaronius Permian of Lodève
Bayreuth Yorkshire Gymnosperm wood Tree fern Tempskya Palm wood Hardwood Manosque Links Eight fossils
Cooksonia, a very old land plant
The evolution of the first land plants was a major event in the history
of Earth. It cleared the way for the irresistible development of animal life
on the land. And it was the land plants which changed the biosphere thoroughly,
e.g. the oxygen rate, the carbonic acid rate, the soil structure and the
character of the erosion.
Finding Cooksonia-fossils is difficult because only a few occurrences are known (marine, delta of river deposits from the Late Silurian and the earliest Devonian). The small size of the plant is also a disadvantage for finding. A rather complete plant is very rare.
W.H. Lang published the first species of Cooksonia in 1937:
C. pertoni en C. hemisphaerica. He used Lower Devonian specimens
from Wales for his description. They were a few centimeters high, one or
more times dichotomously branched and they were bearing more or less globose
sporangia at the end of the branches. Leaves and other appendices were
The best-known species are C. pertoni, C. hemisphaerica,
C. cambrensis, C. caledonica, all described on the basis of
British fossils. Furthermore recently the new species C. paranensis
from Brazil has been described by P. Gerrienne et al (2001).
Cooksonia-sporangia did not have an special adaptation for dehiscence
at maturity. Probably the sporangium simply tore open at the upper side.
(Photo: with permission of Nature Publishing Group).
Cooksonia must be seen as an artificial genus. It probably consists of several genera, which cannot be distinguished at the moment.