Wessiea
| Wessiea Temporal range:
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Scientific classification
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| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Division: | Polypodiophyta |
| Class: | Polypodiopsida |
| Order: | Polypodiales |
| Family: | incertae sedis |
| Genus: | †Wessiea Pigg & Rothwell, 2001 |
| Species | |
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Wessieais anextinctmorphogenus offernnot placed in a specific family.Wessieais known fromLate CretaceousandMiddle Mioceneagefossilsfound in CentralWashingtonUSA and SouthernAlbertaCanada. Two species are described in the morphogenus,W. orosziiand the type speciesW. yakimaensis.
History and classification
[edit]The genus was first described from specimens ofsilicifiedrhizomesand frond bases in blocks ofchert.The chert was recovered from the "Ho ho" site, one of the "county line hole" fossil localities north ofInterstate 82inYakima 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 N2Grande Ronde Basalt,Columbia River Basalt Group.The Museum Flow Package interbeds, designated thetype locality,are dated to themiddle Mioceneand are approximately 15.6 million years old.[1]
Theholotypespecimen, rhizomes and fronds #1–3 and 3 E2 #1–3, are preserved in chert block 3A1 and housed in theBurke Museum of Natural History and Cultureas 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 bypaleobotanistsKathleen B. Pigg ofArizona State Universityand Gar W. Rothwell ofOhio University.Pigg and Rothwell published their 2001type descriptionforWessiea yakimaensisin theAmerican Journal of Botany.[1]In their type description they note theetymologyfor thegeneric nameis in honor ofWesley C. Wehrfor his numerous contributions to Tertiary paleobotany of western North America. Thespecific epithetyakimaensis,is a reference to the type locality in theYakima Canyon.[1]Pigg and Rothwell noted the similarity betweenWessieaand both the modern genusDiplaziumand the fossil genusMakotopteris.[1]
The second species is known from ironstones of theCampanianageHorseshoe Canyon Formation,Alberta, recovered at the "Fred's site" locality. The fossils, housed in theRoyal Tyrrell Museum of Palaeontology,were dissolved from the ironstone and embedded into abioplasticfor study. After embedding, the fossils wereacid peeledby paleobotanists Rudolph Serbet and Gar W. Rothwell for study in thin section slides. Serbert and Rothell published the description ofW. orosziiin a 2006 article. The specific epithet "oroszii" is a patronym honoring s Alfred Orosz, paleontologist for the Royal Tyrrell Museum, and discoverer of the species type locality.[2]
Description
[edit]The morphogenus is defined by the rhizomes and attached frond bases preserved by permineralization. Thestipeshows the presence of two hippocampiform vascular bundles and thedictyosteleis composed of forkingmeristeles.[2]
W. oroszii
[edit]The rhizomes ofW. orosziiare erect in positioning and grow up to 7 mm (0.28 in) in diameter, larger thanW. yakimaensis.The dictyostele is made of five to seven oval meristeles and has a maximum diameter of 2.8 mm (0.11 in). The frond bases are flattened on the upper sides and generally produced by the rhizomes in groups of two to four in a helical arrangement.[2]
W. yakimaensis
[edit]W. yakimaensispossesses rhizomes which are 1.5–3 mm (0.059–0.118 in) in diameter.[1]The frond bases where preserved in the chert are in a distinct helical arrangement and diverge from the center of the arrangement in a recumbent positioning.[2]The dictyostele is composed of four to five individual meristeles each being oval in outline. It is found in the chert blocks intertwined with the extinctOsmunda wehriiand anatomically preservedAnchistea virginica,which still lives in the forests of eastern coastalNorth America.[1]
References
[edit]- ^abcdefghPigg, K.B. (2001). "Anatomically preservedWoodwardia virginica(Blechnaceae) and a new Filicalean fern from the Middle Miocene Yakima Canyon Flora of central Washington, USA ".American Journal of Botany.88(5): 777–787.doi:10.2307/2657030.JSTOR2657030.PMID11353703.
- ^abcdSerbet, R.; Rothwell, G (2006). "Anatomically Preserved Ferns from the Late Cretaceous of Western North America. II. Blechnaceae/Dryopteridaceae".International Journal of Plant Sciences.167(3). The University of Chicago Press: 703–709.doi:10.1086/500996.JSTOR10.1086/500996.S2CID84953835.