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Abstract Detail


Allen, Sarah [1], Alford, Mac [2], Manchester, Steven R [3], Judd, Walter [4].

Flowers of extinct Salicaceae from the Eocene of western Wyoming.

A new flower type has been recognized based on impression and compression specimens from both the Eocene Blue Rim escarpment in the Bridger Formation of southwestern Wyoming and the Kisinger Lakes sites in the Aycross Formation of northwestern Wyoming. The flowers, represented by at least 50 specimens at Blue Rim and four specimens from Kisinger Lakes, are preserved both transversely (most specimens) and laterally (occasionally). Transversely compressed specimens have 8 tepals (likely sepals) in a single whorl, each with an elliptical nectary gland at the base. The tepals, which do not show any distinct venation, average 6.0 mm by 1.2 mm for a length to width ratio of 5.4:1. Stamens are numerous (>50) with distinct filaments and globose to subglobose anthers. Rare specimens preserve a superior ovary. Laterally preserved specimens usually only show 3 or 4 tepals (with the others presumably concealed in the underlying sediment inferred from symmetry), but regularly preserve the pedicel. In situ pollen is prolate, tricolpate with a reticulate exine. The exine is smooth along the colpi margins with the lumina gradually increasing in size away from the colpi. Grains range from ~16-19 µm in polar diameter and ~11-15 µm in equatorial diameter. Families in the basal eudicots and rosids were explored to look for genera with morphological similarities to the fossil flowers. Similar flowers and pollen are present in the tribe Homalieae of Salicaceae sensu lato (former Flacourtiaceae). Homalieae, as currently circumscribed, are not monophyletic, but contain approximately 170 species of tropical trees and shrubs in nine genera. The fossils share the most morphological similarities with Bivinia, Byrsanthus, Calantica, Dissomeria, and Homalium, but most likely represent an extinct genus. The flowers have been tentatively associated with unidentified leaves preserved in the same quarries as the flowers at Blue Rim. The leaves are notophyllous, elliptic, and pinnate with semicraspedodromous secondaries. Tertiaries are opposite percurrent with a straight course. The leaf margin preserves 4-5 convex teeth per centimeter with angular sinuses. To our knowledge, these flowers would be the first confirmed fossils assignable to Homalieae. Wood from the Deccan Intertrappean Beds of India was assigned to Homalioxylon, but this taxonomic assignment has since been refuted as the specimen lacks diagnostic characters found in extant Homalieae. These flowers, together with fruits and foliage previously assigned to Populus and Pseudosalix, indicate that Salicaceae were a conspicuous component of Eocene vegetation near depositional areas in the central Rocky Mountain region.

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1 - University of Florida & Florida Museum of Natural History, Department of Biology, PO Box 118525, Gainesville, FL, 32611, USA
2 - University Of Southern Mississippi, Department Of Biological Sciences, 118 COLLEGE DRIVE #5018, HATTIESBURG, MS, 39406-0001, USA
3 - University Of Florida, Florida Museum Of Natural History, PO BOX 117800, Gainesville, FL, 32611, USA
4 - University of Florida, Florida Museum of Natural History, PO Box 117800, Gainesville, FL, 32611, USA

Fossil flowers.

Presentation Type: Oral Paper
Session: 1, Cookson/Moseley award presentations
Location: Sundance 4/Omni Hotel
Date: Monday, June 26th, 2017
Time: 9:30 AM
Number: 1007
Abstract ID:195
Candidate for Awards:Isabel Cookson Award,Maynard F. Moseley Award

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