Uhlia

''Uhlia'' is an extinct genus of coryphoid palm containing a single species ''Uhlia allenbyensis''. The species is known from permineralized remains recovered from the Princeton Chert in British Columbia, Canada. Leaves of ''Uhlia'' have "tar spot"-like fungal infections of the extinct ascomycete ''Paleoserenomyces'', which in turn are hyperparasitized by the ascomycete ''Cryptodidymosphaerites''.

Distribution

''Uhlia allenbyensis'' is known exclusively from the Princeton Chert, a fossil locality in British Columbia, Canada, which comprises an anatomically preserved flora of Eocene Epoch age, with rich species abundance and diversity. The chert is located in exposures of the Allenby Formation on the east bank of the Similkameen River, south of the town of Princeton, British Columbia.

Notable in conjunction with the coal seams of the Allenby Formation are sections of chert which formed during silica-rich periods. The rapid cyclical changes from coal to chert and back are not noted in any other fossil locality in the world. An estimated 49 coal/chert cycles are known, though the exact conditions for this process are not well understood. Silica-rich volcanic episodes in the region during deposition would have been needed for formation of the cherts, while slowly moving waters and gently subsiding terrains would be needed for the peats and fens to accumulate. Rates of organic deposition in swamps have been estimated at approximately in modern temperate climates, this suggests the time needed for each chert layer would be at least 100 years or more, with the full sequence of cycles taking place over no more than 15,000 years.

The Allenby Formation is one of the southernmost of the Eocene Okanagan Highlands lakes in British Columbia and second most southern site after the Klondike Mountain Formation of Republic, Washington, in northern Ferry County. In British Columbia, the formation is coeval to the Tranquille Formation, known from the McAbee Fossil Beds and Falkland site, the Coldwater Beds, known from the Quilchena site, and Driftwood Canyon Provincial Park. The highlands, including the Allenby Formation, have been described as one of the "Great Canadian '' Lagerstätten''" based on the diversity, quality and unique nature of the biotas that are preserved. The highlands temperate biome preserved across a large transect of lakes recorded many of the earliest appearances of modern genera, while also documenting the last stands of ancient lines.

History and classification

The chert palm fossils were first briefly described in 1976 by James Basinger as part of his PhD thesis; however, due to the isolated nature of the leaf and petiole specimens known at that time, the fossils were not given specific taxonomic treatment. Additional collecting and examination of recovered chert blocks over the next decade and a half included additional palm fossils and allowed for in-depth study by paleobotanists Diane Erwin and Ruth Stockey in the early 1990s. Erwin and Stockey used cellulose acetate peels with hydrofluoric acid to create serial thin sections of the fossils for anatomical and cellular study. The microscope slides were accessioned into the University of Alberta palaeobotanical collections. The formal description of the new genus and species was published by Erwin and Stockey (1994) in the journal '' Palaeontographica Abteilung B'', with the genus name ''Uhlia'' being chosen as a matronym honoring palm systematist Natalie Uhl in recognition of her work on palm taxonomy and the specific name ''allenbyensis'' coined from Allenby, British Columbia, the ghost town that the Allenby Formation takes its name from.

In the type description, ''U. allenbyensis'' was assigned to the palm subfamily Coryphoideae and tribe Corypheae based on the similarity in leaf and stem anatomy to the living genera '' Brahea'', ''Rhapidophyllum'', and ''Serenoa''. Subsequently phylogenetic evaluation of Coryphoideae has led to tribe Corypheae being restricted to only the type genus, with all other former members being placed on other tribes, Cryosophileae or Trachycarpeae.

Description

''Uhlia allenbyensis'' was a rhizomatous palm, with roots growing from the lower side of stems and leaves from the upper side. The roots range between wide with a central stele. The root cortex displays a narrow innermost layer of cells, and a middle cortex with a aerenchymous structure. The stems show a periderm-like layer of cells having irregular to rectangular shape and organized into vertical rows. Underlying the periderm-like layer the stem tissues are grouped into three major zones. The innermost zone, the central region, extends from the stem center to the boundary point with the "B zone". The peripheral area of the central region displays both leaf traces and vascular groupings which were interpreted as inflorescence traces.

Paleoecology

Leaves of ''Uhlia allenbyensis'' show parasitism by the parasitic fungus '' Paleoserenomyces allenbyensis'' which invaded the leaf surface cells. These parasitized areas have been described as similar to modern "tar spot