Pteridosperm

A pteridosperm is an extinct seed plant with fernlike foliage. Known mainly from fossils, pteridosperms form an informal group commonly called seed ferns.

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Seed plant: A plant that reproduces through seeds rather than dispersing only spores. Pteridosperms belong to this broader group despite their fernlike foliage.
Ovule: The structure in seed plants that contains the female gametophyte and develops into a seed after fertilization. Pteridosperm ovules reveal seed reproduction in plants with fernlike leaves.
Devonian: A geologic period spanning about 419 to 359 million years ago, when early seed plants appeared. The earliest known seed-plant lineages emerged before the classic pteridosperm diversity.
Lyginopteris: A Carboniferous pteridosperm genus known from fernlike leaves and anatomically preserved stems. Its preserved organs provide a detailed example of early seed-fern structure.
Plant taxonomy: The classification and naming of plants according to their characteristics and evolutionary relationships. Pteridosperm is an informal grouping rather than a consistently defined taxonomic rank.
Seed: A plant reproductive structure containing an embryo, stored resources, and a protective covering. Seeds distinguish pteridosperms from true ferns, which reproduce with spores.
Pollination: The transfer of pollen to a plant structure where fertilization can occur. Pollen had to reach pteridosperm ovules before seeds could develop.
Carboniferous: A geologic period spanning about 359 to 299 million years ago, marked by extensive coal-forming forests. Many familiar seed-fern fossils come from Carboniferous deposits.
Medullosa: An extinct seed-fern genus, especially diverse in the Carboniferous and Permian. Medullosa shows that pteridosperms included large, complex plants, not just leaf fossils.
Cladistics: A method of classifying organisms by shared derived characteristics and inferred common ancestry. Cladistic analyses test whether traditional seed ferns form natural evolutionary groups.