Constraints on Siluran and Early Devonian phytogeographic analysis based on megafossils

Abstract

The detection of phytogeographic patterns in Silurian and Early Devonian land vegetation is hampered by the dearth of occurrences of megafossils, the absence of consistently precise correlation, unreliability of identification, and the lack of sufficient detailed sampling and information on sediments to permit evaluation of taphonomic influences on composition of assemblages. Interpretation is further complicated by the exceptional evolutionary position of the plants themselves and the lack of extant representatives. There is little information on whole plants, their life histories, their ecological and climatic tolerances. The composition of Ludlow, Pridoli and Lochkovian/Gedinnian assemblages is analysed. Those from Kazakhstan and Siberia are particularly enigmatic. The assemblages are plotted on the appropriate continental reconstructions. Most are clustered on the southeast margin of Laurussia and very few occur at high latitudes.

Silurian and Lower Devonian plant assemblages from the Anglo‐Welsh Basin: a palaeobotanical and palynological synthesis

“…Lower tripapillatusspicula Pȓídolí (?ultimus) Rushall Beds Lang (1937) Fanning (1987) Fanning et al (1988, 1990 Perton Lane, (PL) Hereford, England Edwards and Fanning (1985) Fanning (1987) Fanning et al (1988Fanning et al ( ,1992 …”

Plant Paleoecology in Deep Time1

“…A few examples include the enigmatic fungus Prototaxites Dawson (Hueber, 2001;Boyce et al, 2007), the lycopsid Sawdonia ornata (Dawson) F. M. Hueber (Hueber, 1971), the trimerophyte Pertica quadrifaria Kasper & Andrews (Kasper & Andrews, 1972;Gensel & Andrews, 1984), and numerous plants from the classic Rhynie Chert in Scotland, which usually have been reconstructed by finding parts attached in series rather than as single whole plants (Paleobotanical Research Group, University of Mü nster, 2007). One of the most puzzling nearly whole plants is Cooksonia W. H. Lang, often touted as the earliest vascular land plant but known only from aerial parts (Edwards et al, 1992). Where were the prostrate axes to which these organs presumably were attached?…”

“…Consequently, from the Silurian to the end of the Permian there really was a series of worlds in which plant distributional patterns were changing, sometimes dramatically, through time. There also are time intervals of considerable uncertainty due to poor sampling, intercalated among times of rich sample density during which subtle patterns can be detected (e.g., Edwards, 1990;Laveine et al, 2000). Through most of the later Paleozoic, continental landmasses were gradually coalescing into the Pangean supercontinent, resulting in many land-based connections permitting plant dispersal across wide areas.…”

“…Ziegler et al (2003) argue persuasively that atmospheric circulation patterns are the major controls on vegetational distribution, with due regard for the effects of elevation and paleogeographic locations of moisture sources (e.g., Ziegler et al, 1997). Summaries of Silurian and Devonian paleobiogeography, the most problematic of the Paleozoic, can be found in Raymond et al (1985Raymond et al ( , 2006, , Edwards (1990), and Raymond and Metz (1995); these analyses suggest some largely latitudinal floristic differentiation with limited taxonomic overlap between regions. The much greater abundance of fossil plant collecting sites from the Carboniferous yields a more detailed understanding of phytogeography at that time.…”

New observations on a Pridoli plant assemblage from north Xinjiang, northwest China, with comments on its evolutionary and palaeogeographical significance

“…On the palaeogeographic reconstructions in the locality was on the margin of the Siberian plate (see e.g. Edwards, 1990). However, it was even then abundantly evident from fauna, flora and lithofacies that there was a close relationship with Kazakhstan in Silurian times and thus the western part of the Junggar basin is better attached to the Kazakhstan palaeocontinent.…”