A reappraisal of the Dinantian floras at Oxroad Bay, East Lothian, Scotland. 1. Floristics and the development of whole-plant concepts

Abstract

Re-investigation of species-rich late Tournaisian floras at Oxroad Bay reveals eight plant-bearing exposures that represent four distinct stratigraphic levels. The allochthonous megafossil assemblages vary in degrees of disarticulation, modes of preservation and taxonomic composition. Within-site stratigraphic distributions are presented for 43 anatomically-preserved organ-species; of these, 12 are new to science, 18 have not previously been recorded at the locality, 21 are illustrated from the locality for the first time and 19 are currently considered endemic. Another six have been recorded in error from unprovenanced water-worn blocks. Nineteen adpressed organ-species are also described. Methods and concepts of whole-plant reconstruction are reviewed. At least 11 whole-plant species occur at Oxroad Bay. The lycopsids comprise an enigmatic plant with anAsteroxylon-like stele and two morphologically- and ecologically-distinct species ofOxroadia. A new species ofProtocalamitesdemonstrates the earliest evidence of heterospory and tuberoid stem-bases in the sphenopsid clade.CladoxylonandStauropterisrepresent the pteropsids. At least five lyginopterid pteridosperm species are present. They include both trees (Eristophyton, Bilignea) and shrubs/pseudoherbs (e.g.Tetrastichiaand theTriradioxylon–Calathopteris–Oxroadopteris–‘Tristichia’ plexus), suggesting a range of life strategies. Their diversity has complicated attempts to reconstruct whole-plants, though attachment is demonstrated between several ovules and cupules, and several ovules and pollen-organs are correlated using shared microspores. Elements of particular evolutionary significance include the ‘megacupule’Calathospermumand a structurally similar pollen-organ aggregate, a bisexualPullarithecacupule, and a complete ontogenetic sequence ofHydraspermaovules. Comparable Dinantian floras are reviewed.

The Early Carboniferous (Courceyan–Arundian) monsoonal climate of the British Isles: evidence from growth rings in fossil woods

“…Anatomically preserved fossil woods are very common in the Lower Carboniferous rocks of the British Isles (Scott & Galtier, 1996). However, until recently their value as palaeoclimatic indicators has been neglected (Bateman & Rothwell, 1990).…”

Cordaitalean Seed Plants from the Early Permian of North China. III. Reconstruction of the Shanxioxylon taiyuanense Plant

“…In short, we have sufficient organs to constitute a third whole plant, leaving no surplus organ species. Admittedly, the conceptual reconstruction of S. taiyuanensis lacks roots, but these are the most generalized kind of organ within Paleozoic seed plants and so add relatively little to the phylogenetic or functional interpretation of any reconstruction (Bateman and Rothwell 1990). Importantly, this third conceptual whole plant, S. taiyuanensis, is congruent with the available (albeit limited) evidence gained from association-dissociation and morphological/histological comparison ( fig.…”

Whole-Plant Concept and Environment Reconstruction of aTelemachusConifer (Voltziales) from the Triassic of Antarctica

“…Whole-plant reconstructions play an important role for placing and interpreting extinct plants in a variety of scientific contexts, including physiological and ecological as well as systematic and evolutionary studies (Dilcher 1991;Stewart and Rothwell 1993;DiMichele and Gastaldo 2008;Bateman and Hilton 2009;Taylor et al 2009;Dunn et al 2012). The methods that can be used to reconstruct fossil plants from individual isolated body parts or organs can be classified into three main approaches: (1) identifying organic connections, (2) determining morphological similarities/structural correspondences, and (3) analyzing association/disassociation data (Bateman and Rothwell 1990;Bateman and Hilton 2009). Particular lines of evidence in these categories are diverse; they can be based, for instance, on cuticle micromorphology and epidermal anatomy (Harris 1956;Kerp 1990), on in situ and ex situ palynology (Kva cek 2008), or on the identification of one plant organ in different preservational states (Chaloner 1986;Galtier 1986).…”