Tiffney, Bruce H. , Manchester, Steven R. .
The Middle Eocene Wagon Bed Florule of Central Wyoming, U.S.A.
An assemblage of silicified fruits and seeds from the early Middle Eocene Wagon Bed Formation exposed on the south side of Oil Mountain, Fremont County, Wyoming was investigated for comparison with floras of similar age from other regions. Forty-two specimens were available, along with co-occurring silicified wood, from a collection made in the 1960s; subsequent exploration (1995) did not reveal more material. The specimens range from casts to occasional full anatomical preservation, and were apparently deposited in a mineral-rich lacustrine environment. Twenty-one distinct morphological types are recognizable, 11 of which have recognizable modern familial and/or generic affinities. Among these, Juglandaceae (Juglans or Carya - 10), Anacardiaceae (Spondiaedeae - 5), and Mastixiaceae (Mastixia - 4) are represented by multiple specimens. Additional taxa known from single specimens include Burseraceae (Canarium), Canabinaceae (Celtis and Aphananthe), Menispermaceae (Chandlera; extinct), Lauraceae (genus indet) and possible Pandanaceae (Pandanus?) and Salicaceae. Several taxa are held in common with the Early Eocene Clarno Formation of Oregon and Late Eocene La Porte Flora of California. The Aphananthe endocarp resembles that of A. maii from the Clarno Flora of Oregon, and Chandlera lacunosa Scott is the only known occurrence of this extinct genus other than the type locality at Clarno. The record of Canarium is the first fossil fruit from western North America; the specimen (27 mm long) is much larger than C. parksii from the Eocene of Virginia (6-9 mm long). The taxonomic composition and relatively large disseminule size bespeak a mesic forest, although with a notable paucity of lianes for an Eocene community. This could reflect environmental, successional, or taphonomic features. The presence of mammalian fossils in the Wagon Bed Formation may permit further refinement of this environmental interpretation.
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1 - University of California Santa Barbara, Dept. of Earth Sciences and College of Creative Studies, Santa Barbara, California, 93106, USA
2 - Florida Museum of Natural History, Dickinson Hall, P.O. Box 117800, Gainesville, Florida, 32611, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, July 29th, 2008
Time: 2:45 PM