The origin and early evolution of land plants in the mid-Palaeozoic era, between about 480 and 360 million years ago, was an important event in the history of life, with far-reaching consequences for the evolution of terrestrial organisms and global environments. A recent surge of interest, catalysed by palaeobotanical discoveries and advances in the systematics of living plants, provides a revised perspective on the evolution of early land plants and suggests new directions for future research.

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The origin and early evolution of plants on land

Fossil in situ spores and pollen grains: an annotated catalogue

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.

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Cryptospores and cryptophytes reveal hidden diversity in early land floras

Charting diversity in early land plants morphological diversity and evolution of vegetative organs in pteridophytes RNA editing in land plants phylogenetic reconstruction of some conifer families evolutionary biology of flowers fossil history of magnoliid angiosperms molecular phylogenic relationships among angiosperms - based on rbcL and 18S rDNA sequences evolution of MADS gene family in plants palynological approaches to the origin and early diversification of angiosperms chromosomal evolution of angiosperms mating systems and evolution in flowering plants plant speciation on Oceanic islands speciation and morphological evolution in rheophytes.

Evolution and diversification of land plants

New insights into early land ecosystems: a glimpse of a lilliputian world

Lower Devonian coalified sporangia from Shropshire: Salopella Edwards & Richardson and Tortilicaulis Edwards

A diverse assemblage of early land plants from the Lower Devonian of the Welsh Borderland

Exceptional preservation in Lower Devonian coalified fossils from the Welsh Borderland: a new genus based on reniform sporangia lacking thickened borders

Small coalified plant fragments from basal Pridoli (Silurian) strata at Perton near Hereford, England comprise isotomously branching smooth axes terminating in vertically elongate sporangia. The latter, which occasionally bifurcate, are characterized by prominent, distally concentrated, spinous emergences and contain trilete, retusoid, smooth-walled isospores. The plants are placed in a new genus and species, Caia langii. Comparisons are made with a number of Silurian and Lower Devonian plants with elongate sporangia and particularly with Horneophyton. A hypothesis is developed that spines on sporangia had a nutritive function. The spores are discussed in terms of other records of late Silurian-Early Devonian in situ spores.

U. Fanning

Papers

Lower Devonian coalified sporangia from Shropshire: Salopella Edwards & Richardson and Tortilicaulis Edwards

A diverse assemblage of early land plants from the Lower Devonian of the Welsh Borderland

Exceptional preservation in Lower Devonian coalified fossils from the Welsh Borderland: a new genus based on reniform sporangia lacking thickened borders

Further evidence for diversity in late Silurian land vegetation

Regular ArticleLower Devonian coalified sporangia from Shropshire: Salopella Edwards & Richardson and Tortilicaulis Edwards