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Corystospermaceae is a natural family of seed ferns (
The leaves ('' Dicroidium'') are tied to the fertile organs by similarities of cuticular structure, because their cuticles were robust like those of gymnosperms and unlike the thin leaves of ferns.
Pteridospermatophyta
The term Pteridospermatophyta (or "seed ferns" or "Pteridospermatopsida") is a polyphyletic group of extinct seed-bearing plants (spermatophytes). The earliest fossil evidence for plants of this type is the genus ''Elkinsia'' of the late Devonian ...
) also called Umkomasiaceae, and first based on fossils collected by Hamshaw Thomas from the Burnera Waterfall locality near the Umkomaas River of South Africa. Corystosperms are typified by a group of plants that bore '' Dicroidium'' leaves, ''Umkomasia
''Umkomasia'' is a genus of seed bearing organs produced by corystosperm seed ferns, first based on fossils collected by Hamshaw Thomas from the Burnera Waterfall locality near the Umkomaas River of South Africa.
He recognized on the basis of ...
'' ovulate structures and '' Pteruchus'' pollen organs, that were widespread over Gondwana
Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...
during the Triassic
The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
period. Other fossil Mesozoic seed plants with similar reproductive structures have also sometimes been included within the concept, such as the "doyleoids" from the Early Cretaceous of North America and Asia. A potential corystosperm, the leaf fossil ''Komlopteris cenozoicus'', is known from the Eocene
The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', "daw ...
of Tasmania, at least 13 million years after the Cretaceous–Paleogene extinction event.
Description
Umkomasiaceae have helmet-like cupules aroundovules
In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the ''integument'', forming its outer layer, the ''nucellus'' (or remnant of the megasporangium), and the fem ...
born in complex large branching structures (''Umkomasia
''Umkomasia'' is a genus of seed bearing organs produced by corystosperm seed ferns, first based on fossils collected by Hamshaw Thomas from the Burnera Waterfall locality near the Umkomaas River of South Africa.
He recognized on the basis of ...
'').
The pollen organ ('' Pteruchus'') has numerous cigar-shaped pollen sacs hanging from epaulette-like blades, again in complex branching structures.
The leaves ('' Dicroidium'') are tied to the fertile organs by similarities of cuticular structure, because their cuticles were robust like those of gymnosperms and unlike the thin leaves of ferns.
See also
*Evolution of plants
The evolution of plants has resulted in a wide range of complexity, from the earliest algal mats, through multicellular marine and freshwater green algae, terrestrial bryophytes, lycopods and ferns, to the complex gymnosperms and angiosperms (fl ...
References
External links
* {{Taxonbar, from=Q21588008 Pteridospermatophyta Permian plants Triassic plants Prehistoric plant families Permian first appearances Triassic extinctions