View source for Eoseira

{{Short description|Genus of extinct diatom}}
{{Species box
|fossil_range = {{fossilrange|53|48|[[Ypresian]]}}
|image =
|image_caption =
|genus = Eoseira
|parent_authority = A.P.Wolfe & M.B.Edlund, 2005
|species = wilsonii
|authority = A.P.Wolfe & M.B.Edlund, 2005
}}
'''''Eoseira''''' is an extinct genus of [[diatom]]s belonging to the family [[Aulacoseiraceae]] and containing the single species '''''Eoseira wilsonii'''''. The species is dated to the [[Early Eocene]] [[Ypresian]] stage and has only been found at the type locality in east central British Columbia.
==Distribution==
''Eoseira wilsonii'' was an [[algal bloom]] forming [[diatom]] during the [[Early Eocene Climatic Optimum]]<ref name="Lowe2018">{{cite journal |last1=Lowe |first1=A. J. |last2=Greenwood |first2=D. R. |last3=West |first3=C. K. |last4=Galloway |first4=J. M. |last5=Sudermann |first5=M. |last6=Reichgelt |first6=T. |year=2018 |title=Plant community ecology and climate on an upland volcanic landscape during the Early Eocene Climatic Optimum: McAbee Fossil Beds, British Columbia, Canada |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=511 |pages=433–448|doi=10.1016/j.palaeo.2018.09.010 |bibcode=2018PPP...511..433L |s2cid=134962126 }}</ref> and one of the major lake components the [[Horsefly Shales]] lake system. The Horsefly shales have not been radiometrically dated, but based on shared [[Paleoflora of the Eocene Okanagan Highlands|floral]] and [[Paleofauna of the Eocene Okanagan Highlands|faunal]] taxa found in the other [[Early Eocene]], [[Ypresian]] age, [[Eocene Okanagan Highlands|Okanagan Highlands sites]], Horsefly is assumed to be contemporaneous.<ref name="Archibald2015">{{Cite journal|last1=Archibald |first1=S.B. |last2=Rasnitsyn |first2=A.P. |year=2015 |title=New early Eocene Siricomorpha (Hymenoptera: Symphyta: Pamphiliidae, Siricidae, Cephidae) from the Okanagan Highlands, western North America |journal=The Canadian Entomologist |volume=148 |issue=2 |pages=209–228 |doi=10.4039/tce.2015.55 |s2cid=85743832 }}</ref>
==History and classification==
Diatom fossils at Horsefly had been noted by Mark Wilson and Adrian Bogan (1994) who identified significant diatom volumes in the "summer [[varve]]s" during study of a 6,375 year long [[stratigraphic section]].<ref name="Varves1994">{{cite journal |last1=Wilson |first1=M. V. |last2=Bogen |first2=A. |title=Tests of the annual hypothesis and temporal calibration of a 6375‐varve fish‐bearing interval, Eocene horsefly beds, British Columbia, Canada |journal=Historical Biology |date=1994 |volume=7 |issue=4 |pages=325–339 |doi=10.1080/10292389409380463}}</ref> Fossil material was studied subsequently by Alexander Wolfe and Mark Edlund (2005) with the type description of the species being published in the ''[[Canadian Journal of Earth Sciences]]''.<ref name="A.Wolfe2005"/><ref name="GBIFgenus">{{cite web |title=''Eoseira'' A.P.Wolfe & M.B.Edlund, 2005 |url=https://www.gbif.org/species/7515240 |website=www.gbif.org |access-date=10 April 2022}}</ref><ref name="GBIFspecies">{{cite web |title=''Eoseira wilsonii'' A.P.Wolfe & M.B.Edlund, 2005 |url=https://www.gbif.org/species/8345121 |website=www.gbif.org |access-date=10 April 2022}}</ref> They designated three type specimens at the time of publication, the [[holotype]] "CANA 76143" and [[paratype]] "BCr; CANA 76144" which were both accessioned into the [[Canadian Museum of Nature]] at Ottawa, while the [[Isotype (biology)|isotype]] was placed in the [[California Academy of Sciences|California Academy of Sciences Diatom Herbarium]].  Both the holotype and isotype were collected from the lower (H2) varve sequence exposed at the Horsefly mine locality. The paratype was collected at the nearby outcrops along the Black Creek Road. Wolfe and Edlund coined the [[Botanical name#Components of plant names|specific epithet]] ''wilsonii'' as a [[patronym]] honoring [[Mark V. H. Wilson|Mark Wilson]] as recognition for his enormous work on western North American Eocene lake [[paleolimnology]] and [[paleoichthyology]].  They did not give an etymology for the genus name ''Eoseira''.<ref name="A.Wolfe2005"/>
''E. wilsonii'' was placed into the family Aulacoseiraceae based on the numerous similarities to other members of the family, but placed into the monotypic new genus ''Eoseira'' due to a suite of distinctive features.<ref name="A.Wolfe2005"/>  Aulacoseiraceae is considered one of the first diatom families to transition from marine to freshwater habitats, sometime during the [[Cretaceous]]. The oldest genus of the family is ''Aulacoseira'', from which ''Eoseira'' and other undescribed genera branched from in the Eocene, while a second diversification even took place in the Miocene resulting in the extinct genera ''[[Alveolophora]]'', ''[[Miosira]]'', and ''[[Pseudoaulacosira]]''. ''E. wilsonii'' is suggested to be a sister branch to the aulacoseiroid lineages.<ref name="A.Wolfe2005"/>
==Description==
''Eoseira wilsonii'' grew valve [[frustule]]s with a cylindrical cross-section when viewed from the end, and a rectangular outline when viewed from the side. The individual valves formed linked filaments, with many individual frustules connected end to end by an interlinking collar of spines that arise from the face-side junction.  The spines on a valve are spoon-shaped with a narrow base widening to an ovoid tip and [[Dovetail joint|dovetailing]] with the spines of the next valve.  Each spine is smooth on the external surface and along the inner margins.<ref name="A.Wolfe2005"/>  The sides of the valves are stippled with straight rows of [[Areolae (diatom)|areolae]] oriented parallel to each other and perpendicular to the valve end faces. Unlike in ''Aulacoseira'' enlarged single or paired areolae groups do not form the linking or separation spines, rather the spines arise entirety separate from the areolae.  Each of the areolae has a thin, porous silica layer, a vela, on the internal side of the opening. In contrast, as is seen in ''Aulacoseira'', the valves of ''E. wilsonii'' develop a distinct [[ringleiste]] on the internal surface of the valves. Between the ringleist and valve junction are a number of sessile pore openings through the valve surface, called rimoportulae. The two halves of the valves are linked via girdle bands with connecting ligulate strands which developed parallel poroid rows oriented perpendicular to the valve ends.<ref name="A.Wolfe2005"/>
[[File:Aulacoseira granulata 2.jpeg|thumb|right|''[[Aulacoseira granulata]]'' living filament]]
==Paleoecology==
The polysaccharide slime grown by ''E. wilsonii'' is suggested to have enhanced the preservation quality of organisms which were coated by the slime films before entombment in the lake sediments.<ref name="A.Wolfe2005">{{cite journal |last1=Wolfe |first1=A. |last2=Edlund |first2=M. |year=2005 |title=Taxonomy, phylogeny, and paleoecology of ''Eoseira wilsonii'' gen. et sp. nov., a Middle Eocene diatom (Bacillariophyceae: Aulacoseiraceae) from lake sediments at Horsefly, British Columbia, Canada |journal=Canadian Journal of Earth Sciences |volume=42 |issue=2 |pages=243–257|doi=10.1139/e04-051 |bibcode=2005CaJES..42..243W }}</ref> The horsefly lake system has been interpreted as [[monomictic]] to possibly [[meromictic]].  If the lake was monomictic, the lake waters would have one period of surface layer and deep water mixing a year, but if it was meromictic, the water layers did not have any annual periods of mixing.<ref name="Mallomonas2019">{{cite journal |last1=Siver |first1=P. A. |last2=Skogstad |first2=A. |last3=Nemcova |first3=Y. |title=Endemism, palaeoendemism and migration: the case for the 'European endemic', ''Mallomonas intermedia'' |journal=European Journal of Phycology |date=2019 |volume=54 |issue=2 |pages=222–234 |doi=10.1080/09670262.2018.1544377|s2cid=85555530 }}</ref>
''E. wilsonii'' is one of two diatoms known from Horsefly, with an undescribed species of ''[[Aulacoseira]]'' also being present. Unlike ''[[Aulacoseira giraffensis]]'' from the similarly aged [[Giraffe maar]] [[kimberlite pipe]] deposit in the [[North West Territories]] however, the  undescribed Horsefly ''Aulacoseira'' species was a minor component of the lake flora, with ''E. wilsonii'' being the dominatant bloom florming species.<ref name="Siver2019">{{cite journal |last1=Siver |first1=P. A. |last2=Wolfe |first2=A. P. |last3=Edlund |first3=M. B. |last4=Sibley |first4=J. |last5=Hausman |first5=J. |last6=Torres |first6=P. |last7=Lott |first7=A. M. |title=''Aulacoseira giraffensis'' (Bacillariophyceae), a new diatom species forming massive populations in an Eocene lake. |journal=Plant Ecology and Evolution |date=2019 |volume=152 |issue=2 |pages=358–367 |doi=10.5091/plecevo.2019.1586|s2cid=199531867 |doi-access=free }}</ref> Additionally the extant [[synurid]] "[[algae]]" species ''[[Mallomonas intermedia]]'' has also been recovered from Horsefly,<ref name="Mallomonas2019"/> while study of diatomitic sediments by George Mustoe (2005) from the [[McAbee Fossil Beds]] show undescribed Aulacoseiraceae diatoms and [[chrysophyte]] stomatocysts.  Mustoe also examined sediment from the [[Allenby Formation]] near Princeton and found diatomitic layers, but noted that alteration and remineralization of the [[Opal#Noncrystalline opal|opal-A]] to [[Opal#Microcrystalline opal|opal-CT]] destroyed the original organic structures in the diatomite.<ref name="Mustoe2005diatom">{{cite journal |last1=Mustoe |first1=G. E. |year=2005 |title=Diatomaceous origin of siliceous shale in Eocene lake beds of central British Columbia |journal=Canadian Journal of Earth Sciences |volume=42 |issue=2 |pages=231–241 |doi=10.1139/e04-099|bibcode=2005CaJES..42..231M }}</ref>
==Paleoenvironment==
The greater Eocene Okanagan Highlands likely had a [[Mesic habitat|mesic]] [[Microthermal|upper microthermal]] to [[mesothermal|lower mesothermal]] climate, in which winter temperatures rarely dropped low enough for snow, and which were seasonably equitable.<ref name="Greenwood2005"/>  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 [[Biota (plant)|biota]]s the lakes were higher and cooler then the [[coeval]] coastal forests preserved in the [[Puget Group]] and [[Chuckanut Formation]] of Western Washington, which are described as [[Tropical forest|lowland tropical forest]] ecosystems. Estimates of the [[elevation|paleoelevation]] range between {{convert|0.7-1.2|km|mi|abbr=on}} higher than the coastal forests.  This is consistent with the paleoelevation estimates for the lake systems, which range between {{convert|1.1-2.9|km|m|abbr=on}}, which is similar to the modern elevation {{convert|0.8|km|mi|abbr=on}}, but higher.<ref name="Greenwood2005"/> Estimates of the [[Climate|mean annual temperature]] have been derived from [[Paleothermometer#Leaf margin analysis|leaf margin analysis (LMA)]] of the Horsefly shales with the LMA returning a mean annual temperature of approximately {{convert|10.4|±|2.2|C|F|abbr=on}}. The estimated cold month mean temperature during the winter is placed at approximately {{convert|5.3|±|2.8|C|F|abbr=on}}. These estimates are lower than the mean annual temperature estimates given for the coastal Puget Group, which is estimated to have been between {{convert|15–18.6|C|F|abbr=on}}.  The bioclimatic analysis for Horsefly suggests a mean annual precipitation amount of {{convert|105|±|47|cm|in|abbr=on}}.<ref name="Greenwood2005">{{cite journal |last1=Greenwood |first1=D.R. |last2=Archibald |first2=S.B. |last3=Mathewes |first3=R.W |last4=Moss |first4=P.T. |year=2005 |title=Fossil biotas from the Okanagan Highlands, southern British Columbia and northeastern Washington State: climates and ecosystems across an Eocene landscape |journal=Canadian Journal of Earth Sciences |volume=42 |issue=2 |pages=167–185|bibcode=2005CaJES..42..167G |doi=10.1139/e04-100}}</ref>
The Okanagan Highlands fossil sites, which includes the Eocene formations between the [[Driftwood Shales]] near [[Smithers, British Columbia]] in the north and the [[Klondike Mountain Formation]] surrounding [[Republic, Washington]] to the south have been described collectively as one of the "Great Canadian ''[[Lagerstätten]]''"<ref name="GCL2011"/> based on the diversity, quality and unique nature of the biotas that are preserved.  The highlands temperate biome preserved across such a large transect of lakes recorded many of the earliest appearances of modern genera, while also documenting the last stands of ancient lines.<ref name="GCL2011">{{cite journal |last1=Archibald |first1=S. |last2=Greenwood |first2=D. |last3=Smith |first3=R. |last4=Mathewes |first4=R. |last5=Basinger |first5=J. |year=2011 |title=Great Canadian ''Lagerstätten'' 1. Early Eocene Lagerstätten of the Okanagan Highlands (British Columbia and Washington State) |journal=Geoscience Canada |volume=38 |issue=4 |pages=155–164}}</ref> The warm temperate highland floras in association with downfaulted [[lacustrine basin]]s 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 [[East African Rift|African rift valley]].<ref name="DeVore2020">{{Cite journal|last1=DeVore |first1=M. L. |last2=Nyandwi |first2=A. |last3=Eckardt |first3=W. |last4=Bizuru |first4=E. |last5=Mujawamariya |first5=M. |last6=Pigg |first6=K. B. |year=2020 |title=Urticaceae leaves with stinging trichomes were already present in latest early Eocene Okanogan Highlands, British Columbia, Canada |journal=American Journal of Botany |volume=107 |issue=10 |pages=1449–1456 |doi=10.1002/ajb2.1548 |pmid=33091153 |s2cid=225050834 |doi-access=free }}</ref>
==References==
{{Reflist}}
{{Taxonbar|from=Q21397804}}
[[Category:Diatoms|†Eoseira]]
[[Category:Ypresian plants of North America]]
[[Category:Extinct flora of North America]]
[[Category:Flora of the West Coast of the United States|†]]
[[Category:Plants described in 2005|†]]
[[Category:Fossil taxa described in 2005]]
[[Category:Horsefly Shales]]
[[Category:Diatom genera|†]]