Cryptospores are microscopic fossil produced by Embryophyte (land plants). They first appear in the fossil record during the middle of the Ordovician period, as the oldest fossil evidence for the colonization of land by plants. A similar (though broader) category is miospores, a term generally used for spores smaller than 200 Micrometre. Both cryptospores and miospores are types of Palynology.
Cryptospores, which occur as permanent tetrads, dyads, or hilate monads, sometimes with additional wall envelopes, dominated fossil assemblages for approximately 60 million years, first appearing around 470 million years ago during the Ordovician Period. They underwent rapid diversification during what Jane Gray (1993) called the Eoembryophytic epoch,[Wellman CH, Steemans P, Vecoli M. 2013. Chapter 29 Palaeophytogeography of Ordovician–Silurian land plants. Geological Society, London, Memoirs 38: 461–476.]
Evidence that cryptospores derive from land plants
Occurrence
Cryptospores are generally found in non-marine rocks and decrease in abundance with distance offshore. This suggests that any cryptospores found in the marine environment were transported there by the wind from the land, rather than originating from the marine environment.
Wall ultrastructure
The walls of cryptospores consist of many lamellae (thin sheets).
Marchantiophyta, thought to be the most primitive
land plants, also have this spore wall morphology.
Chemical composition
(Some) cryptospores are composed of sporopollenin and have the same chemical makeup as co-occurring trilete spores.
Other information
Recently, fossils of plant
Sporangium have been found in
Oman with cryptospores showing concentric lamellae in their walls, similar to
liverworts. The earliest known cryptospores are from Middle
Ordovician (
Dapingian) strata of
Argentina.
Spores from the Lindegård
Mudstone (late
Katian–early
Hirnantian) represent the earliest record of early
land plant spores from
Sweden and possibly also from
Baltica and implies that
land plants had migrated to the
palaeocontinent Baltica by at least the Late
Ordovician.
This discovery reinforces the earlier suggestion that the migration of land plants from northern
Gondwana to
Baltica in the Late
Ordovician was facilitated by the northward migration of
Avalonia,
which is evidenced by the co-occurrence of reworked, Early–Middle
Ordovician acritarchs, possibly suggesting an Avalonian provenance in a
foreland basin system.
See also
Further reading
