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Cryptospores and cryptophytes reveal hidden diversity in early land floras

Edwards, Dianne, Morris, Jennifer, Richardson, John B. and Kenrick, Paul 2014. Cryptospores and cryptophytes reveal hidden diversity in early land floras. New Phytologist 202 (1) , pp. 50-78. 10.1111/nph.12645

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Abstract

Cryptospores, recovered from Ordovician through Devonian rocks, differ from trilete spores in possessing distinctive configurations (i.e. hilate monads, dyads, and permanent tetrads). Their affinities are contentious, but knowledge of their relationships is essential to understanding the nature of the earliest land flora. This review brings together evidence about the source plants, mostly obtained from spores extracted from minute, fragmented, yet exceptionally anatomically preserved fossils. We coin the term ‘cryptophytes’ for plants that produced the cryptospores and show them to have been simple terrestrial organisms of short stature (i.e. millimetres high). Two lineages are currently recognized. Partitatheca shows a combination of characters (e.g. spo-rophyte bifurcation, stomata, and dyads) unknown in plants today. Lenticulatheca encompasses discoidal sporangia containing monads formed from dyads with ultrastructure closer to that of higher plants, as exemplified by Cooksonia. Other emerging groupings are less well characterized, and their precise affinities to living clades remain unclear. Some may be stem group embryophytes or tracheophytes. Others are more closely related to the bryophytes, but they are not bryophytes as defined by extant representatives. Cryptophytes encompass a pool of diversity from which modern bryophytes and vascular plants emerged, but were competitively replaced by early tracheophytes. Sporogenesis always produced either dyads or tetrads, indicating strict genetic control. The long-held consensus that tetrads were the archetypal condition in land plants is challenged.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QK Botany
Uncontrolled Keywords: bryophytes; Devonian; dyads; meiosis; Ordovician-Silurian; spore-wall ultrastructure; tetrads; tracheophytes
Additional Information: Free open access PDF version available via Related URL link.
Publisher: Wiley-Blackwell
ISSN: 0028-646X
Date of First Compliant Deposit: 30 March 2016
Date of Acceptance: 4 November 2013
Last Modified: 26 Feb 2019 15:48
URI: http://orca.cf.ac.uk/id/eprint/57757

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