| Wessiea Temporal range: Middle Miocene 15.6 Ma |
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|---|---|
| Scientific classification | |
| Kingdom: | Plantae |
| Division: | Pteridophyta |
| Class: | Pteridopsida |
| Order: | Polypodiales |
| Family: | Dryopteridaceae |
| Genus: | †Wessiea |
| Species: | †W. yakimaensis |
| Binomial name | |
| Wessiea yakimaensis Pigg & Stockey 2001 |
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Wessiea is an extinct monotypic genus of fern in the Dryopteridaceae family with the sole species Wessiea yakimaensis. Wessia is known from Langhian age Miocene fossils found in Central Washington.[1]
The genus was described from specimens of slicified rhizomes and frond bases in blocks of chert. The cherts were recovered from the "Ho ho" site, one of the "county line hole" fossil localities north of Interstate 82 in Yakima County, Washington.[1] The "Ho ho" site works strata which is part of the Museum Flow Package within the interbeds of the Sentinel Bluffs Unit of the central Columbia Plateau N2 Grande Ronde Basalt, Columbia River Basalt Group. The Museum Flow Package interbeds, designated the type locality, are dated to the middle Miocene and are approximately 15.6 million years old.[1]
The holotype specimen, rhizomes and fronds #1–3 and 3 E2 #1–3, are preserved in chert block 3A1 and housed in the Burke Museum of Natural History and Culture as specimen number "UWBM 56441". The paratype, number 3F1 #2 top on specimen "UWBM 56441", is a rhizome which shows root gaps, roots and frond bases.[1] The specimens of chert were studied by paleobotanists Kathleen B. Pgg of Arizona State University and Gar W. Rothwell of Ohio University. Drs Pigg and Rothwell published their 2001 type description for Wessiea yakimaensis in the American Journal of Botany volume 88, Anatomically preserved Woodwardia virginica (Blechnaceae) and a new Filicalean fern from the Middle Miocene Yakima Canyon Flora of central Washington, USA.[1] In their type description they note the etymology for the generic name is in honor of Wesley C. Wehr for his numerous contributions to Tertiary paleobotany of western North America. The specific epithet yakimaensis, is a reference to the type locality in the Yakima Canyon.[1] Drs Pigg and Rothwell noted the similarity between Wessiea and both the modern genus Diplazium and the fossil genus Makotopteris.[1]
Wessiea possesses rhizomes which are 1.5–3 millimetres (0.059–0.12 in) in diameter. The frond bases where preserved in the chert are in a distinct helical arrangement. It is found in the chert blocks intertwined with the extinct Osmunda wehrii and anatomically preserved Woodwardia virginica, which still lives in the forests of eastern coastal North America.[1]