Cooksonia

Cooksonia is an extinct genus of small early vascular plants known from Silurian and Devonian rocks. Its slender, leafless branching stems ended in spore-bearing capsules.

Vascular plant: A plant with specialized tissues that transport water, minerals, and sugars through its body. Cooksonia’s conducting tissues distinguish it from earlier nonvascular land plants.
Silurian: A geologic period lasting from about 443 to 419 million years ago. Some of the oldest Cooksonia fossils come from Silurian deposits.
Cooksonia pertoni: A species of Cooksonia described from Silurian fossils in Britain. Its fossils helped establish Cooksonia as a distinctive early plant genus.
Polysporangiophyte: A land plant with a branched sporophyte bearing multiple sporangia. Cooksonia’s branching, spore-bearing axes fit this broad early-plant group.
Sporophyte: The diploid, spore-producing stage in a plant’s life cycle. Cooksonia fossils represent the spore-producing generation of the plant.
Devonian: A geologic period lasting from about 419 to 359 million years ago. Cooksonia fossils also occur in Devonian strata.
Cooksonia caledonica: A species assigned to Cooksonia from Silurian deposits in Scotland. Its branching stems and terminal capsules illustrate the genus’s characteristic form.
Rhyniophyte: An extinct grade of simple early vascular plants, often defined by branching axes and terminal sporangia. Cooksonia has often been grouped with rhyniophytes, though the group’s boundaries are unsettled.
Sporangium: A structure in which spores are produced and released. The terminal capsules on Cooksonia stems are sporangia.
Přídolí: The final series of the Silurian Period, spanning about 423 to 419 million years ago. Cooksonia-bearing rocks from this interval record early vascular plant diversity.

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