Late Silurian and Early Devonian fossil plants of Bathurst Island, arctic Canada

Abstract

Early land plant fossils were retrieved from Bathurst Island, Arctic Canada. These plants are preserved as compressions, impressions or rarely pyrite permineralizations in rocks of Late Silurian and Early Devonian age. Specimens of some taxa are numerous and, sometimes, almost complete, allowing analysis of intraspecific variability, developmental patterns and reconstruction of the whole plant. The majority of plant fossils are derived from the Pragian Stuart Baybeds. This flora is currently the largest and most diverse pre-Emsian flora from North America. The flora is composed primarily of zosterophylls; however, rhyniophytoids, lycophytes, and a trimerophyte were also collected. Sixteen Pragian plant taxa are described herein: Cooksonia hemisphaerica, Cooksonia sp., four species of Zosterophyllum, three of which are described as new species, Distichophytum ovatum, two new genera bearing bilaterally arranged, dense spikes, Bathurstia denticulata, Psitopnytites sp., Drepanophycus spinaeformis, D. gaspianus, one trimerophyte, and two plants of unknown affinity. Zosterophyllum new species c, found primarily in certain beds of the Cheyne River region is the only taxon that is isolated to specific sites or beds on the island. This Pragian flora, correlates best to the contemporaneous floras of northern Laurussia and Siberia. Four species belonging to Lochkovian beds are described: Newgenus F newspecies, Hicklingiasp., cf. Distichophytumsp. and cf. Bathurstia sp. Of great significance is a small number of Late Silurian plant fossils collected from the lower Bathurst Island beds in the Polar Bear Pass region. Plants from the Late Silurian are poorly known, but most reports indicate that they were very simple. The plants from the Silurian rocks of Bathurst Island possess advanced characteristics more typical of Early Devonian floras. Seven taxa are described, including two new zosterophyllgenera, a rhyniophytoid of unknown genus and species,a Bathurstia-like zosterophyll bearing robust two-rowed spikes, Zosterophyllumsp., Zosterophyllum cf. Z. newspecies b, and Distichophytum sp.