Cryptospore

Cryptospores are microscopic fossilized spores produced by embryophytes (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 μm. Both cryptospores and miospores are types of palynomorphs.^[1]

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). Liverworts, 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.^[2]

Other information

Recently, fossils of plant sporangia 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.^[3] 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.^[4] 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,^[5] which is evidenced by the co-occurrence of reworked, Early–Middle Ordovician acritarchs, possibly suggesting an Avalonian provenance in a foreland basin system.

References

^ Steemans, P (2000). "Miospore evolution from the Ordovician to the Silurian". Review of Palaeobotany and Palynology. 113 (1–3): 189–196. Bibcode:2000RPaPa.113..189S. doi:10.1016/S0034-6667(00)00059-2. PMID 11164219.
^ Steemans, P.; Lepot, K.; Marshall, C.P.; Le Hérissé, A. and Javaux, E.J. (2010). "FTIR characterisation of the chemical composition of Silurian miospores (cryptospores and trilete spores) from Gotland, Sweden" (PDF). Review of Palaeobotany and Palynology. 162 (4): 577–590. Bibcode:2010RPaPa.162..577S. doi:10.1016/j.revpalbo.2010.07.006.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Rubinstein, C.V.; Gerrienne, P.; de la Puente, G.S.; Astini, R.A.; Steemans, P. (2010). "Early Middle Ordovician evidence for land plants in Argentina (eastern Gondwana)". New Phytologist. 188 (2): 365–369. doi:10.1111/j.1469-8137.2010.03433.x. hdl:11336/55341. PMID 20731783. S2CID 24070744.
^ Badawy, A.S.; Mehlqvist, K.; Vajda, V.; Ahlberg, P. and Calner, M. (2014). "Late Ordovician (Katian) spores in Sweden: oldest land plant remains from Baltica". GFF. 136 (1): 16–21. Bibcode:2014GFF...136...16B. doi:10.1080/11035897.2014.899266. S2CID 22198834.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^ Steemans, P.; Wellman, C.H. and Gerrienne, P. (2010). "Paleogeographic and paleoclimatic considerations based on Ordovician to Lochkovian vegetation". Geological Society, London, Special Publications. 339 (1): 49–58. Bibcode:2010GSLSP.339...49S. doi:10.1144/SP339.5. S2CID 140195843.{{cite journal}}: CS1 maint: multiple names: authors list (link)