Dattola, Melissa A. , Caruso, Joseph A. , Nauman, Brandon N. , Tomescu, Alexandru MF .
Additional diversity in Early Devonian floras of the Beartooth Butte Formation (Wyoming).
The Beartooth Butte Formation has yielded Early Devonian (Pragian-Emsian, 400-410 Myr old) plant fossil assemblages from two localities in Wyoming. These are the only extensive Early Devonian plant fossil assemblages known from western North America. The Beartooth Butte Formation is a discontinuous unit that consists of dolomitic channel fill deposits interpreted as estuarine to fluvial sediments. Plants are preserved as coalified compressions (sometimes highly oxidized) or impressions. They form allochthonous assemblages characterized by a relatively high degree of fragmentation, mixed with fish remains. The few previous studies of the Beartooth Butte Formation flora have revealed considerable diversity (including Drephanophycus, Gosslingia, Renalia, Sawdonia, Psilophyton, Rebuchia, and Hostinella), but have not produced exhaustive taxonomic accounts. An ongoing re-examination of the Beartooth Butte Formation, aimed at filling this gap, expands the known diversity of the flora. Among the most interesting findings are specimens with slender axes (<1 mm), some of which bear lateral stalked sporangia at irregular intervals, while others bear terminal sporangia. Numerous minute specimens (<1 cm2) consist of slender, sometimes branching appendages radiating from a central area, reminiscent of land plant gametophytes. Also notable are a few axes (<4 cm long) bearing whorls of short branches spaced at ca. 5 mm intervals. Among the Drepanophycus axes, a significant proportion exhibit knotty lateral protrusions, often supplied by conspicuous vascular strands, that could represent plant response to pathogens or animal damage. Our findings emphasize the need for thorough re-examination of these poorly characterized fossil floras, which will add to knowledge of Early Devonian plant diversity and biogeography.
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1 - Humboldt State University, Department of Biological Sciences, Arcata, CA, 95521, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Superior A/Cliff Lodge - Level C
Date: Monday, July 27th, 2009
Time: 9:15 AM