Dickwhitea

Dickwhitea; Temporal range: 50–49 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Scientific classification
Kingdom:	Plantae
Phylum:	Tracheophytes
Division:	Polypodiophyta
Class:	Polypodiopsida
Order:	Polypodiales
Suborder:	Aspleniineae
Family:	Athyriaceae
Genus:	† Dickwhitea ; Karafit et al.
Species:	†D. allenbyensis
Binomial name
	†Dickwhitea allenbyensis; Karafit et al.

Last updated March 23, 2024

Dickwhitea is an extinct morphogenus of lady fern containing a single morphospecies Dickwhitea allenbyensis. The species is known from permineralized remains recovered from the Princeton Chert in British Columbia, Canada. Rhizomes of Dickwhitea are noted for having a sympodial vascular architecture notably similar to Ginkgo biloba and Sequoia sempervirens .

Distribution

Dickwhitea is known exclusively from the Princeton Chert, a fossil locality in British Columbia, Canada,^[1]^[2] 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, 8.5 km (5.3 mi) south of the town of Princeton, British Columbia.^[3]

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 (0.02–0.04 in) in modern temperate climates, this suggests the time needed for each 10–20 cm (4–8 in) chert layer would be at least 100 years or more, with the full sequence of cycles taking place over no more then 15,000 years.^[4]

The Allenby Formation is one of the southern-most of the Eocene Okanagan Highlands Lagerstätten in British Columbia, with the Canadian Penticton Group at the international border and the Klondike Mountain Formation of Republic, Washington in northern Ferry County to the south. The highlands, including the Allenby Formation, have been described as one of the "Great Canadian Lagerstätten"^[5] based on the diversity, quality and unique nature of the biotas that are preserved. The Eocene Okanagan Highlands temperate-subtropical 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.^[5]

History and classification

The fossil material was all derived from a single block of chert, number P1080, which was collected from outcrops of the Princeton chert approximately 630 m (2,070 ft) above the Princeton black coal seam. Within the block two rhizomes with associated and isolated adventitious roots and stipes. A paleobotanical team led by Steven Karafit used cellulose acetate peels with hydrofluoric acid to create serial thin sections of the fossils for anatomical and cellular study. The blocks, slabs and microscope slides were accessioned into the University of Alberta palaeobotanical collections.^[1] The formal description of the new genus and species was published by Karafit et al. (2006) in the International Journal of Plant Sciences , with the genus name Dickwhitea being chosen as a patronym honoring fern systematist Richard "Dick" White in recognition of his work on fern vascular anatomy and the specific name allenbyensis coined from Allenby, British Columbia, the ghost town that the Allenby Formation takes its name from.^[1]

Karafit et al. considered the morphogenus in the same family as Makotopteris princetonensis , another Princeton Chert fern, based on the overall structure of the rhizome and the paired Onoclea -type stipes of the leaves. The stele features seen in D. allenbyensis are found in both Athyriaceae and Dryopteridaceae, and the placement into Athyriaceae was not discussed by the authors.^[1]

Description

Vascular diagram with Eustele arrangement (right) Siphonostele.jpg — Vascular diagram with Eustele arrangement (right)

Dickwhitea allenbyensis is known only from 6–7 mm (0.24–0.28 in) wide radial rhizomes, the longest preserved section being just over 9.0 cm (3.5 in) long. The rhizomes have a relatively long internodal structure which was suggested to be around 1 cm (0.39 in) long due to the fragmentary fossils usually only showing one stipe in the preserved length. The longest specimen recorded was to distorted and incomplete to measure the internodal length with certainty. Both attached and isolated roots, along with the frond stipes are known. The rhizomes have a radial symmetry with roots and stipes growing in helical arrangement all the way around the rhizome circumference. The frond bases are arranged along the rhizome in an 2/5 phyllotactic helix succession. In cross section the 2–3 mm (0.079–0.118 in) wide stipes show a distorted square outline with rounded corners and lacking a grove along the upper surface. Due to the nature of the preservation within the chert, none of the upper portions of D. allenbyensis, specifically fronds or spores, is known.^[1] The roots grade from the epidermal layer into sclerenchyma cells and then to parenchyma cells in the cortex and pith. The pith is between 2.9–4.6 mm (0.11–0.18 in) wide comprised of tightly packed parenchyma. In areas where the preservation is good, the parenchyma cells appear to lack internal contents.^[1] The cauline vascular bundles are vessel groups that extend outwards from the central xylem.^[1] The roots are adventitious along the rhizome and have a diarch xylem vessel structure, with the oldest xylem cells forming two lines along the outer sides of the vessel.^[6] The stipes have two hippocampiform vascular bundles which originate from cauline vessel bundles next to each other. Each diverging frond base is spaced two cauline vessel bundles away from the next in the radial spiral pattern. This divergent pattern arising from the five radially placed cauline bundles is noted as equivalent to the eustele of ginkgo and conifers like Sequoia sempervirens .^[1] This was the fossil evidence for eustele-type vascular arrangement arising in ferns, and confirming the eustele like structure of the modern fern genera Botrychium and Ophioglossum .^[1]^[7]

Paleoenvironment

The Princeton chert preserves an aquatic system with silica rich slow moving waters which was likely a peat fen ecosystem. While other fossil producing areas of the Allenby Formation are likely the product of deep water deposition and diatomite sedimentation, the chert layers originate from shallow waters, as evidenced by plant and animal fossils.^[4] The Okanagan Highland sites, such as the Princeton chert represent upland lake systems that were surrounded by a warm temperate ecosystem with nearby volcanism.^[5] The highlands likely had a mesic upper microthermal to lower mesothermal climate, in which winter temperatures rarely dropped low enough for snow and which were seasonably equitable.^[8] The Okanagan Highlands paleoforest surrounding the lakes have been described as precursors to the modern temperate broadleaf and mixed forests of Eastern North America and Eastern Asia. Based on the fossil 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.^[8]

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).^[8]

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.^[9]

Related Research Articles

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Azolla primaeva is an extinct species of "water fern" in the family Salviniaceae known from Eocene fossils from the Ypresian stage, found in southern British Columbia.

Wessiea is an extinct morphogenus of fern not placed in a specific family. Wessiea is known from Late Cretaceous and Middle Miocene age fossils found in Central Washington USA and Southern Alberta Canada. Two species are described in the morphogenus, W. oroszii and the type species W. yakimaensis.

The Princeton Chert is a fossil locality in British Columbia, Canada, which comprises an anatomically preserved flora of Eocene Epoch age, with rich species abundance and diversity. It 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.

The McAbee Fossil Beds is a Heritage Site that protects an Eocene Epoch fossil locality east of Cache Creek, British Columbia, Canada, just north of and visible from Provincial Highway 97 / the Trans-Canada Highway. The McAbee Fossil Beds, comprising 548.23 hectares, were officially designated a Provincial Heritage Site under British Columbia's Heritage Conservation Act on July 19, 2012. The site is part of an old lake bed which was deposited about 52 million years ago and is internationally recognised for the diversity of plant, insect, and fish fossils found there. Similar fossil beds in Eocene lake sediments, also known for their well preserved plant, insect and fish fossils, are found at Driftwood Canyon Provincial Park near Smithers in northern British Columbia, on the Horsefly River near Quesnel in central British Columbia, and at Republic in Washington, United States. The Princeton Chert fossil beds in southern British Columbia are also Eocene, but primarily preserve an aquatic plant community. A 2016 review of the early Eocene fossil sites from the interior of British Columbia discusses the history of paleobotanical research at McAbee, the Princeton Chert, Driftwood Canyon, and related Eocene fossil sites such as at Republic.

The Allenby formation is a sedimentary rock formation in British Columbia which was deposited during the Ypresian stage of the Early Eocene. It consists of conglomerates, sandstones with interbedded shales and coal. The shales contain an abundance of insect, fish and plant fossils known from 1877 and onward, while the Princeton Chert was first indented in the 1950's and is known from anatomically preserved plants.

Nuphar carlquistii is an extinct species of flowering plant in the family Nymphaeaceae related to the modern spatterdock, Nuphar advena. The species is known from fossil seeds and fruits found in the early Eocene Okanagan Highlands deposits of northern Washington state and British Columbia, Canada.

Comptonia columbiana is an extinct species of sweet fern in the flowering plant family Myricaceae. The species is known from fossil leaves found in the early Eocene deposits of central to southern British Columbia, Canada, plus northern Washington state, United States, and, tentatively, the late Eocene of Southern Idaho and Earliest Oligocene of Oregon, United States.

Amia? hesperia is an extinct species of bony fish in the bowfin family, Amiidae. The species is known from fossils found in the early Eocene deposits of northern Washington state in the United States and southeastern British Columbia. The species is one of eight fish species identified in the Eocene Okanagan Highlands paleofauna.

Equisetum similkamense is an extinct horsetail species in the family Equisetaceae described from a group of whole plant fossils including rhizomes, stems, and leaves. The species is known from Ypresian sediments exposed in British Columbia, Canada. It is one of several extinct species placed in the living genus Equisetum.

The paleoflora of the Eocene Okanagan Highlands includes all plant and fungi fossils preserved in the Eocene Okanagan Highlands Lagerstätten. The highlands are a series of Early Eocene geological formations which span an 1,000 km (620 mi) transect of British Columbia, Canada and Washington state, United States and are known for the diverse and detailed plant fossils which represent an upland temperate ecosystem immediately after the Paleocene-Eocene thermal maximum, and before the increased cooling of the middle and late Eocene to Oligocene. The fossiliferous deposits of the region were noted as early as 1873, with small amounts of systematic work happening in the 1880-90s on British Columbian sites, and 1920-30s for Washington sites. A returned focus and more detailed descriptive work on the Okanagan Highlands sites revived in the 1970's. The noted richness of agricultural plant families in Republic and Princeton floras resulted in the term "Eocene orchards" being used for the paleofloras.

The Eocene Okanagan Highlands or Eocene Okanogan Highlands are a series of Early Eocene geological formations which span a 1,000 km (620 mi) transect of British Columbia, Canada, and Washington state, United States. Known for a highly diverse and detailed plant and animal paleobiota the paleolake beds as a whole are considered one of the great Canadian Lagerstätten. The paleobiota represented are of an upland subtropical to temperate ecosystem series immediately after the Paleocene–Eocene thermal maximum, and before the increased cooling of the middle and late Eocene to Oligocene. The fossiliferous deposits of the region were noted as early as 1873, with small amounts of systematic work happening in the 1870–1920s on British Columbian sites, and 1920–1930s for Washington sites. Focus and more detailed descriptive work on the Okanagan Highland sites started in the late 1960s.

The paleofauna of the Eocene Okanagan Highlands consists of Early Eocene arthropods, vertebrates, plus rare nematodes and molluscs found in geological formations of the northwestern North American Eocene Okanagan Highlands. The highlands lake bed series' as a whole are considered one of the great Canadian Lagerstätten. The paleofauna represents that of a late Ypresian upland temperate ecosystem immediately after the Paleocene-Eocene thermal maximum, and before the increased cooling of the middle and late Eocene to Oligocene. The fossiliferous deposits of the region were noted as early as 1873, with small amounts of systematic work happening in the 1880-90s on British Columbian sites, and 1920-30s for Washington sites. Focus and more detailed descriptive work on the Okanagan Highlands site started in the last 1970's. Most of the highlands sites are preserved as compression-impression fossils in "shales", but also includes a rare permineralized biota and an amber biota.

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.

Paleoserenomyces is an extinct monotypic genus of pleosporale fungus of uncertain family placement. When described it contained the single species Paleoserenomyces allenbyensis. The genus is solely known from the Early Eocene, Ypresian aged, Princeton Chert deposit of the Allenby Formation. Palaeoserenomyces is one of only three described fossil fungus species found in the Princeton Chert, being a tar spot like parasite of the fossil palm Uhlia allenbyensis, and is host for the hyperparasite Cryptodidymosphaerites princetonensis.

Cryptodidymosphaerites is an extinct monotypic genus of pleosporale fungus of uncertain family placement. When described it contained the single species Cryptodidymosphaerites princetonensis. The genus is solely known from the Early Eocene, Ypresian aged, Princeton Chert deposit of the Allenby Formation. Cryptodidymosphaerites is one of only three described fossil fungus species found in the Princeton Chert, and is a hyperparasite of Palaeoserenomyces allenbyensis, itself a tar spot-like parasite of the fossil palm Uhlia.

Plecia avus is an extinct species of Plecia in the March fly family Bibionidae and is solely known from Early Eocene sediments exposed in central southern British Columbia. The species is one of twenty bibionid species described from the Eocene Okanagan Highlands.

The Paleobiota of the Klondike Mountain Formation comprises a diverse suite of Early Eocene plants and animals recovered from North Central Washington State. The formation outcrops in locations across the north western area of Ferry County, with major sites in Republic, north west of Curlew Lake, and on the Toroda Creek area. The formation is the southern most of the Eocene Okanagan Highlands, sharing much of the paleoflora and paleofauna with site across Central and southern British Columbia.

Dennstaedtia christophelii is an extinct species of fern in the family Dennstaedtiaceae related to the modern hayscented ferns. The species is known from fossil fronds found in early Eocene sites of northern Washington state, United States and central British Columbia, Canada. The species is suggested to be closest to a Neotropical "Patania" clade and specifically the species Dennstaedtia producta and Dennstaedtia mathewsii.

Allenbya is an extinct genus of water lilies in the family Nymphaeaceae containing a single species Allenbya collinsonae. The species is known from permineralized remains recovered from the Early Eocene Princeton Chert in British Columbia, Canada.

References

1 2 3 4 5 6 7 8 9 Karafit, S. J.; Rothwell, G. W.; Stockey, R. A.; Nishida, H. (2006). "Evidence for sympodial vascular architecture in a filicalean fern rhizome: Dickwhitea allenbyensis gen. et sp. nov.(Athyriaceae)". International Journal of Plant Sciences. 167 (3): 721–727. doi:10.1086/501036. S2CID 85348245.
↑ Currah, R.S.; Stockey, R.A.; LePage, B.A. (1998). "An Eocene tar spot on a fossil palm and its fungal hyperparasite". Mycologia. 90 (4): 667–673. doi:10.1080/00275514.1998.12026955.
↑ 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.
1 2 Mustoe, G. (2010). "Cyclic sedimentation in the Eocene Allenby Formation of south-central British Columbia and the origin of the Princeton Chert fossil beds". Canadian Journal of Earth Sciences. 48 (1): 25–43. doi:10.1139/e10-085.
1 2 3 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.
↑ "Tracheophyte - Roots". Brittanica. Retrieved 8 August 2023.
↑ Rothwell, G.W.; Stockey, R.A. (2008). "Phylogeny and evolution of ferns: a paleontological perspective". Biology and evolution of ferns and lycophytes. Cambridge University Press. p. 332-366. doi:10.1017/CBO9780511541827.014.
1 2 3 Greenwood, D.R.; Archibald, S.B.; Mathewes, R.W; Moss, P.T. (2005). "Fossil biotas from the Okanagan Highlands, southern British Columbia and northeastern Washington State: climates and ecosystems across an Eocene landscape" (PDF). Canadian Journal of Earth Sciences. 42 (2): 167–185. Bibcode:2005CaJES..42..167G. doi:10.1139/e04-100.
↑ DeVore, M. L.; Nyandwi, A.; Eckardt, W.; Bizuru, E.; Mujawamariya, M.; Pigg, K. B. (2020). "Urticaceae leaves with stinging trichomes were already present in latest early Eocene Okanogan Highlands, British Columbia, Canada". American Journal of Botany. 107 (10): 1449–1456. doi:10.1002/ajb2.1548. PMID 33091153. S2CID 225050834.

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[Dickwhitea2006-1] 1 2 3 4 5 6 7 8 9 Karafit, S. J.; Rothwell, G. W.; Stockey, R. A.; Nishida, H. (2006). "Evidence for sympodial vascular architecture in a filicalean fern rhizome: Dickwhitea allenbyensis gen. et sp. nov.(Athyriaceae)". International Journal of Plant Sciences. 167 (3): 721–727. doi:10.1086/501036. S2CID 85348245.

[tarspot1998-2] Currah, R.S.; Stockey, R.A.; LePage, B.A. (1998). "An Eocene tar spot on a fossil palm and its fungal hyperparasite". Mycologia. 90 (4): 667–673. doi:10.1080/00275514.1998.12026955.

[Miller1975pine-3] 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.

[Mustoe2010-4] 1 2 Mustoe, G. (2010). "Cyclic sedimentation in the Eocene Allenby Formation of south-central British Columbia and the origin of the Princeton Chert fossil beds". Canadian Journal of Earth Sciences. 48 (1): 25–43. doi:10.1139/e10-085.

[GCL2011-5] 1 2 3 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.

[Brittanica-6] "Tracheophyte - Roots". Brittanica. Retrieved 8 August 2023.

[7] Rothwell, G.W.; Stockey, R.A. (2008). "Phylogeny and evolution of ferns: a paleontological perspective". Biology and evolution of ferns and lycophytes. Cambridge University Press. p. 332-366. doi:10.1017/CBO9780511541827.014.

[Greenwood2005-8] 1 2 3 Greenwood, D.R.; Archibald, S.B.; Mathewes, R.W; Moss, P.T. (2005). "Fossil biotas from the Okanagan Highlands, southern British Columbia and northeastern Washington State: climates and ecosystems across an Eocene landscape" (PDF). Canadian Journal of Earth Sciences. 42 (2): 167–185. Bibcode:2005CaJES..42..167G. doi:10.1139/e04-100.

[DeVore2020-9] DeVore, M. L.; Nyandwi, A.; Eckardt, W.; Bizuru, E.; Mujawamariya, M.; Pigg, K. B. (2020). "Urticaceae leaves with stinging trichomes were already present in latest early Eocene Okanogan Highlands, British Columbia, Canada". American Journal of Botany. 107 (10): 1449–1456. doi:10.1002/ajb2.1548. PMID 33091153. S2CID 225050834.

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