Sprecher
Beschreibung
The Battery Point Formation, exposed in eastern Quebec (Canada), hosts mid- to late Emsian fossil assemblages preserved as adpressions and permineralizations. At least 17 euphyllophyte taxa are known to date from permineralizations in this unit. We add to these five new euphyllophyte morphotypes described from permineralizations. Three of the five have Psilophyton-type tracheids typical of early euphyllophytes: one morphotype with a trilobed mesarch actinostele; a second morphotype with elliptical xylem (in cross section) and 2-3 mesarch protoxylem strands; a third morphotype with elongate xylem with lobed ends and probably mesarch protoxylem. The other two morphotypes have tracheids with circular-oval bordered pits indicative of cladoxylopsid affinities. One of them has an actinostele with three major ribs, two of which are bisected, and probably exarch xylem maturation, reminiscent of cladoxylopsid roots. The other is a larger cladoxylopsid with a typical deeply lobed and dissected actinostele-plectostele with multiple protoxylem strands per xylem lobe. These new morphotypes increase the taxonomic diversity and morphological disparity of euphyllophytes known from the Battery Point Formation. The group appeared in the late Silurian >425 Ma ago but euphyllophyte diversity remained modest during the first 15 million-years and increased significantly in the second half of the Early Devonian. Euphyllophyte diversity in the Battery Point Formation, unparalleled in coeval and older Devonian localities, provides the oldest snapshot of the effects of the first major radiation of the clade, suggesting that this early burst of diversification was fast and had probably started by the beginning of the Emsian.