The development of early terrestrial ecosystems

In this review of terrestrialization by plants and animals in the early Phanerozoic, the classical idea of a major mid-Palaeozoic event is discarded in favour of gradual colonization over a long time period. Four phases of colonization of the land by plants are recognized but their limits are often difficult to define. The first, of microbial mats comprising prokaryotes and later photosynthesizing protists (algae) but with no direct fossil evidence, extends from the Precambrian and may persist in environments unsuitable for colonization by higher plants and animals today. The second, based on microfossils (spores and cuticles) possibly from plants of bryophyte aspect (if not affinity) started in the Ordovician (c. 460 Ma ago) and ended in the Lower Devonian, but was overlapped by the third phase beginning early in the Silurian (c. 430 Ma). This consisted of small plants of axial organization with terminal sporangia probably allied to the tracheophytes. The advent of taller vascular plants of varied organization around the Silurian — Devonian boundary (c. 420–400 Ma) signalled the final pioneering phase — that of major adaptative radiations on land, culminating in the appearance of extant groups, in changes in reproductive strategy and in the development of complex vegetation structure. The animal record is sparser than that of the plants, but suggests an early land fauna in the mid-Palaeozoic which differed from later terrestrial assemblages in lacking herbivores, with the first direct fossil evidence for land animals in the late Silurian

A palaeobotanical pot-pourri

This study, the third in the series of virtual issues of Palaeontology, examines the contributions the journal has made to the field of palaeobotany from 1961 onwards. I offer a personal selection of six papers repres enting four decades of research, with a range of specific geographical (Canada, Australia, China), temporal (Mesozoic, Devonian, Silurian) or more general (cycads, palynology, stratigraphy) focus

The Silurian greening of planet Earth

Comparative studies on spores and megafossils of early land plants in Silurian times will be reviewed in an attempt to reconstruct the pioneering phases of terrestrial vegetation on both regional and global scales. Traditionally the advent and diversification of vascular plants have dominated such studies. The recent discoveries of in situ nontrilete spores (viz. cryptospores in the form of dyads and tetrads) and subsequent ultrastructural studies permit more informed speculation on the nature and significance of the earliest embryophytes which are generally accepted as related to bryophytes.Simposio I: 2º Simposio de bioestratigrafía y eventos del Paleozoico inferiorFacultad de Ciencias Naturales y Muse

Embryophytic sporophytes in the Rhynie and Windyfield cherts

Brief descriptions and comments on relationships are given for the seven embryophytic sporophytes in the cherts at Rhynie, Aberdeenshire, Scotland. They are Rhynia gwynnevaughanii Kidston & Lang, Aglaophyton major D. S. Edwards, Horneophyton lignieri Barghoorn & Darrah, Asteroxylon mackiei Kidston & Lang, Nothia aphylla Lyon ex Høeg, Trichopherophyton teuchansii Lyon & Edwards and Ventarura lyonii Powell, Edwards & Trewin. The superb preservation of the silica permineralisations produced in the hot spring environment provides remarkable insights into the anatomy of early land plants which are not available from compression fossils and other modes of permineralisation. They include soft tissues, such as those surrounding stomata, rhizoids, apical and lateral meristems, and diversity in conducting cells, with inferences for palaeoecophysiology, including water use efficiency, transport and absorption, and for growth processes and patterns

Far away and long ago: a South American odyssey

This lecture gives me a splendid opportunity to celebrate the importance of South America plants in palaeobotanical studies as they relate to a personal journey in the sub continent. This began in Venezuela many years ago when I began studies on a very diverse Middle to Upper Devonian flora, research now undertaken by Chris Berry. Its palaeogeographical significance remains intriguing, because, in similarities in assemblage composition, it relates to North America. In contrast subsequent studies in Argentina and Bolivia, earlier in the Devonian and Silurian, reveal a flora far more typical of Gondwana. Even more importantly it gives us some insight into high latitude vegetation, although sadly preservation is very poor in fragmentary fossils. Thus we have no comprehensive insights into early land plant ecosystems as, for example, is provided by the Rhynie Chert Lower Devonian hot spring deposit in Scotland. However a similar hot spring deposit recently discovered in the Jurassic of Santa Cruz Province, Argentina, provides a phenomenal window into an ecosystem preserved in situ and in great cellular detail, encompassing plants, animals and microbes. And so the odyssey ends in Patagonia on a high that would surely have been of major interest to naturalist W.H. Hudson (Far away and long ago: a history of my early life). It would not have been possible without the assistance and generosity of colleagues in La Plata, whose contributions will be further acknowledged in the lecture.Conferencias plenarias.Facultad de Ciencias Naturales y Muse

New plants from the Lower Devonian Pingyipu Group, Jiangyou County, Sichuan Province, China

Descriptions of Lower Devonian plants from Yunnan, South China, have revolutionized concepts of diversity and disparity in tracheophytes soon after they became established on land. Sichuan assemblages have received little attention since their discovery almost 25 years ago and require revision. With this objective, fieldwork involving detailed logging and collection of fossils was undertaken in the Longmenshan Mountain Region, Jiangyou County and yielded the two new taxa described here. They are preserved as coalified compressions and impressions that allowed morphological but not anatomical analyses. Yanmenia (Zosterophyllum) longa comb nov is based on numerous rarely branching shoots with enations resembling lycophyte microphylls, without evidence for vasculature. The presence of sporangia is equivocal making assignation to the Lycopsida conjectural. The plant was recently described as a zosterophyll, but lacks strobili. These are present in the second plant and comprise bivalved sporangia. The strobili terminate aerial stems which arise from a basal axial complex displaying diversity in branching including H- and K- forms. These features characterise the Zosterophyllopsida, although the plant differs from Zosterophyllum in valve shape. Comparisons indicate greatest similarities to the Lower Devonian Guangnania cuneata, from Yunnan, but differences, particularly in the nature of the sporangium border, require the erection of a new species, G. minor. Superficial examination of specimens already published indicate a high degree of endemism at both species and generic level, while this study shows that Yanmenia is confined to Sichuan and Guangnania is one of the very few genera shared with Yunnan, where assemblages also show a high proportion of further endemic genera. Such provincialism noted in the Chinese Lower Devonian is explained by the palaeogeographic isolation of the South China plate, but this cannot account for differences/endemism between the Sichuan and Yunnan floras. Such an enigma demands further integrated geological, palaeobotanical and palynological studies

Glimpses of the botanical history of Wales

The Ordovician through Carboniferous rocks of Wales and the Welsh borderland (c. 250 million years) have been central to elucidating the initial phases of the colonization of land by plants as they diversified from simple herbaceous organisms lacking leaves and roots to substantial forest trees. Spores extracted from Ordovician and younger rocks indicate that pioneering plants allied to mosses and liverworts were part of a vegetation composed of lichens and algae. Vascular plants today include ferns, horsetails, conifers, and flowering plants but their earliest fossils in Silurian and Devonian rocks, although possessing all the anatomical characteristics of today’s flora, had very simple architecture – essentially collections of green smooth stems and sacs of spores (e.g. Cooksonia). In time branching diversified and height and reproductive capacity increased. Only one group, the clubmosses, with small simple leaves, still exists, evolving into the gigantic trees that dominated Carboniferous swamps. Other members of the tropical forests included tall ferns and horsetails plus the earliest seed plants. The peat they produced was transformed into coal whose exploitation led to Wales’s global influence during the Industrial Revolution

The early evolution of land plants, from fossils to genomics: a commentary on Lang (1937) ‘On the plant-remains from the Downtonian of England and Wales'

© 2015 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, provided the original author and source are credited. The file attached is the published version of the article