Uhlia

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Uhlia
Temporal range: Ypresian
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Clade: Commelinids
Order: Arecales
Family: Arecaceae
Subfamily: Coryphoideae
Tribe: Trachycarpeae
Genus: †Uhlia
Erwin & Stockey
Species:
†U. allenbyensis
Binomial name
†Uhlia allenbyensis
Erwin & Stockey

Uhlia is an

ascomycete Paleoserenomyces, which in turn are hyperparasitized by the ascomycete Cryptodidymosphaerites
.

Distribution

Close up of Princeton Chert outcrop showing volcanic ash (white layer at base), peaty coal (dark layer), and Chert layers (grey). Layer 36 is labelled.

Uhlia allenbyensis is known exclusively from the

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, 8.5 km (5.3 mi) south of the town of Princeton, British Columbia.[2]

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 0.5–1 mm (0.020–0.039 in) in modern temperate climates, this suggests the time needed for each 10–20 cm (3.9–7.9 in) 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.[3]

The Allenby Formation is one of the southernmost of the

Lagerstätten"[4] 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.[4]

History and classification

The chert palm fossils were first briefly described in 1976 by

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.[1]

In the type description, U. allenbyensis was assigned to the palm subfamily

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[5] or Trachycarpeae.[6]

Description

Uhlia allenbyensis was a rhizomatous palm, with roots growing from the lower side of stems and leaves from the upper side.[1] The roots range between 4–10 mm (0.16–0.39 in) 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.[1]

Paleoecology

Georgia, USA

Leaves of Uhlia allenbyensis show parasitism by the

Cryptodidymosphaerites princetonensis was preserved, providing a firm fossil record for fungal hyperparasitism.[7]

The low stature of U. allenbyensis has been likened to that of the modern saw palmetto

Phoeniceae.[8]

Paleoenvironment

The Princeton chert preserves an aquatic system with silica rich slow moving waters which was likely a

biotas, the lakes were higher and cooler than the coeval coastal forests preserved in the Puget Group and Chuckanut Formation of Western Washington, which are described as lowland tropical forest ecosystems. Estimates of the paleoelevation range between 0.7–1.2 km (0.43–0.75 mi) higher than the coastal forests. This is consistent with the paleoelevation estimates for the lake systems, which range between 1.1–2.9 km (1,100–2,900 m), which is similar to the modern elevation of 0.8 km (0.50 mi) but higher.[9]

Estimates of the mean annual temperature have been derived from climate leaf analysis multivariate program (CLAMP) analysis and leaf margin analysis (LMA) of the Princeton paleoflora. The CLAMP results after multiple linear regressions for Princeton's gave a 5.1 °C (41.2 °F), and the LMA returned a mean annual temperature of 5.1 ± 2.2 °C (41.2 ± 4.0 °F). This is lower than the mean annual temperature estimates given for the coastal Puget Group, which is estimated to have been between 15–18.6 °C (59.0–65.5 °F). The bioclimatic analysis for Princeton suggest mean annual precipitation amount of 114 ± 42 cm (45 ± 17 in).[9]

The warm temperate uplands floras of the Allenby Formation and greater highlands in association with downfaulted

lacustrine basins and active volcanism are noted to have no exact modern equivalents. This is due to the more seasonally equitable conditions of the Early Eocene, resulting in much lower seasonal temperature shifts. However, the highlands have been compared to the upland ecological islands in the Virunga Mountains within the Albertine Rift of the African rift valley.[10]

References

  1. ^ a b c d e Erwin, D.M.; Stockey, R.A. (1994). "Permineralized monocotyledons from the middle Eocene Princeton chert (Allenby Formation) of British Columbia: Arecaceae". Palaeontographica Abteilung B. 234: 19–40.
  2. ^ Miller, C. (1975). "Silicified cones and vegetative remains of Pinus from the Eocene of British Columbia". Contributions from the Museum of Paleontology, University of Michigan. 24 (10): 101–118.
  3. ^
    doi:10.1139/e10-085
    .
  4. ^ a b c Archibald, S.; Greenwood, D.; Smith, R.; Mathewes, R.; Basinger, J. (2011). "Great Canadian Lagerstätten 1. Early Eocene Lagerstätten of the Okanagan Highlands (British Columbia and Washington State)". Geoscience Canada. 38 (4): 155–164.
  5. ^ Stevens, P.F. (2015) [1st. Pub. 2001], Arecale-Angiosperm Phylogeny Website, retrieved 22 December 2021
  6. S2CID 208587364
    .
  7. JSTOR 3761225
    .
  8. PMID 24821798
    .
  9. ^
    doi:10.1139/e04-100
    .
  10. S2CID 225050834
    .
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