Paleobiota of the Latah Formation
The paleobiota of the Latah Formation encompasses both floral and faunal elements preserved in temporary lacustrine environments formed between eruptive phases of the Columbia River Basalts in central to east Eastern Washington and central to north Idaho. The Latah Formation is centered around the greater Spokane area, with a western extent outcropping at Grand Coulee and the eastern margins as far southeast as the area of White Bird, Idaho. Dating of the core Spokane sites is based on the host Grande Ronde Basalts which give an age range of. The Clarkia fossil beds lagerstätte site are slightly younger, being interbedded in the Wanapum Basalts Priest Rapids Member with an age constraint of, or Early Barstovian in age.
The intermittent lakes were surrounded by a temperate ecosystem that was mesophytic in nature, and hosting a diverse flora with plants that are still native to the region and others now restricted to other areas of the globe. There is a small element of the flora that consists of fully extinct genera that are unique to the time and region. Based on work from sampling around Mica, Washington a diverse assembly of diatoms and algae lived in the Spokane area lakes though water conditions for growth were not ideal. The known fauna of the formation is smaller than the flora, with most taxa being insect species though one unnamed Sciuridae fossil was described in 2018, and fish belonging to the salmonid, cyprinid, and centrarchid groups are known. Preservation varies from carbonized compressions at most sites to exceptional organic preservations in some parts of the Clarkia area localities where original organic material is preserved down to living coloration and possible ancient DNA fragments. Upper layers of the Clarkia deposits have been recorded with modern fungi actively feeding on the ancient organic material of the fossils as a food source.
Plants
The initial taxonomic work on the flora was undertaken by Frank Knowlton with assistance from diatom specialist Albert Mann and bryologist Elizabeth Britton. Their combined work was published as a supplemental chapter to the initial 1926 descriptive work by Joseph Pardee and Kirk Bryan. After Knowlton's death in November 1926, his revision of the Latah flora was taken over by Edward W. Berry who also erroneously included strata of the much older Klondike Mountain Formation around Republic, Washington. This error was noted and corrected in later works by Roland W. Brown. Ralph W. Cheney and Daniel I. Axelrod broke the Latah into four major florules, Grand Coulee and Spokane in Washington plus Coeur d'Alene and White Bird in Idaho, while noting several "miscellaneous" sites as well. Modern works have concentrated more on single taxa and certain florules.Magnoliids
Fungi
The Clarkia outcrops is noted for exceptionally good palynological preservation, with a number of fungal palynomorphs preserved at the sites.| Order | Family | Genus | Species | Florule | Notes | Images |
Amphisphaeriales | Cf. Apiosporaceae | indeterminate | indeterminate | Clarkia | ||
Chaetosphaeriales | Chaetosphaeriaceae | Cf. ''Catenularia | indeterminate | Clarkia | ||
Coronophorales | incertae sedis | Sphaerodes | indeterminate | Clarkia | ||
| Dothideomycetes | incertae sedis | Bactrodesmium | Aff. B. abruptum | Clarkia | ||
| Dothideomycetes | incertae sedis | Bactrodesmium | indeterminate | Clarkia | ||
Helotiales | Helotiaceae | Bispora | indeterminate | Clarkia | ||
Hysteriales | Hysteriaceae | Cf. Acrogenospora | indeterminate | Clarkia | ||
Minutisphaerales | Minutisphaeraceae | Minutisphaera | indeterminate | Clarkia | ||
| Pleosporales | Dictyosporiaceae | Dictyocheirospora | indeterminate | Clarkia | ||
| Pleosporales | Didymosphaeriaceae | Cf. Didymosphaeria | indeterminate | Clarkia | ||
| Pleosporales | Roussoellaceae | Neoroussoella | indeterminate | Clarkia | ||
Savoryellales | Savoryellaceae | Cf. Helicoon | indeterminate | Clarkia | ||
| Sordariales | Chaetomiaceae | Chaetomium | indeterminate | Clarkia | ||
| Sordariales | Chaetomiaceae | Trichocladium | indeterminate | Clarkia | ||
| Sordariales | Lasiosphaeriaceae | Cf. Bombardioidea | indeterminate | Clarkia | ||
| Sordariales | Naviculisporaceae | Naviculispora | indeterminate | Clarkia | ||
| Sordariales | Neoschizotheciaceae | Cf. Cercophora | indeterminate | Clarkia | ||
| Sordariales | Podosporaceae | Podospora | indeterminate | Clarkia | ||
| Sordariales | incertae sedis | Brachysporiella | indeterminate | Clarkia | ||
Cf. Sordariales | indeterminate | indeterminate | indeterminate | Clarkia | ||
Tubeufiales | Tubeufiaceae | Pendulispora | indeterminate | Clarkia | ||
| Xenospadicoidales | Xenospadicoidaceae | Spadicoides | S. sp. 1. | Clarkia | ||
| Xenospadicoidales | Xenospadicoidaceae | Spadicoides | S. sp. 2. | Clarkia | ||
| Xylariales | Xylariaceae | Cf. Rosellinia | indeterminate | Clarkia | ||
| Xylariales | Xylariaceae | indeterminate | indeterminate | Clarkia | ||
| incertae sedis | Diporothecaceae | Diporotheca | Aff. D. rhizophila | Clarkia | ||
| incertae sedis | incertae sedis | Acarocybiopsis | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Cf. Brachydesmiella | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Desertella | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Endophragmia | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Endophragmiopsis | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Endophragmiella | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Helensiella | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Cf. Hermatomyces | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Hughesinia | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Cf. Lemkea | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Melanocephala | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Cf. Melanographium | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Phragmocephala | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Cf. Polytretophora | indeterminate | Clarkia | ||
| incertae sedis | incertae sedis | Seychellomyces'' | indeterminate | Clarkia |
Algae
An initial survey of Latah Formation diatoms was conduced by Albert Mann at the behest of Frank Hall Knowlton. Based on sample material recovered from a well west of Mica, Washington, itself southeast of Spokane, Mann identified a large number of diatomaceous species, including 10 new species. Mann noted the diatoms appear to have lived under stressed conditions caused by caustic water, with many of the specimens showing malformed shapes or blurred ornamentations. The typical cause of this in diatoms is a high concentration of dissolved mineral salts in the water body.| Family | Genus | Species | Author/year | Florule | Notes | Synonyms | Images |
| Amphipleuraceae | Amphipleura | Amphipleura oregonica | Grunow |
| An amphipleuraceous diatom |
| |
| Amphipleuraceae | Frustulia | Frustulia rhomboides | De Toni |
| An amphipleuraceous diatom | ||
| Aulacoseiraceae | Aulacoseira | †Aulacoseira distans | Simonsen |
| A aulacoseiraceous diatom |
| |
| Aulacoseiraceae | Aulacoseira | Aulacoseira granulata | Simonsen |
| A aulacoseiraceous diatom |
| |
| Cavinulaceae | Cavinula | Cavinula scutiformis | D.G.Mann & A.J.Stickle |
| A cavinulaceous diatom |
| |
| Coscinodiscaceae | Coscinodiscus | Coscinodiscus subaulacodiscoidalis | Rattray |
| A coscinodiscaceous diatom | ||
| Cymbellaceae | Cymbella | Cymbella americana | A.W.F.Schmidt |
| A cymbellaceous diatom | ||
| Cymbellaceae | Cymbella | Cymbella amphicephala | Näegeli |
| A cymbellaceous diatom | ||
| Cymbellaceae | Cymbella | Cymbella flexella | Kützing |
| A cymbellaceous diatom |
| |
| Cymbellaceae | Cymbella | Cymbella lunula | Rabenhorst |
| A cymbellaceous diatom | ||
| Cymbellaceae | Cymbella | Cymbella partita | Mann |
| A cymbellaceous diatom | ||
| Cymbellaceae | Cymbella | Cymbella sagittarius | Mann |
| A cymbellaceous diatom | ||
| Eunotiaceae | Actinella | Actinella brasiliensis | Grunow |
| A eunotiaceous diatom | ||
| Eunotiaceae | Desmogonium | Desmogonium rabenhorstianum | Grunow |
| A eunotiaceous diatom | ||
| Eunotiaceae | Eunotia | Eunotia incisa | Grunow |
| A eunotiaceous diatom | ||
| Eunotiaceae | Eunotia | Eunotia parallela | Ehrenberg |
| A eunotiaceous diatom | ||
| Eunotiaceae | Eunotia | Eunotia pectinalis | Rabenhorst |
| A eunotiaceous diatom | ||
| Eunotiaceae | Eunotia | Eunotia robusta | Ralfs |
| A eunotiaceous diatom Varieties E. r. var. diadema & E. r. var. papilio | ||
| Fragilariaceae | Fragilaria | Fragilaria constricta | Hustedt |
| A fragilariaceous diatom Form Fragilaria constricta f. stricta |
| |
| Fragilariaceae | Fragilaria | Fragilaria binalis | Ehrenberg |
| A fragilariaceous diatom |
| |
| Gomphonemataceae | Gomphonema | Gomphonema acuminatum | Ehrenberg |
| A gomphonemataceous diatom | ||
| Gomphonemataceae | Gomphonema | Gomphonema gracile | Ehrenberg |
| A gomphonemataceous diatom | ||
| Gomphonemataceae | Gomphonema | Gomphonema parvulum | Kützing |
| A gomphonemataceous diatom | ||
| Melosiraceae | Melosira | Melosira biseriata | Schmidt |
| A melosiraceous diatom | ||
| Melosiraceae | Melosira | Melosira lyrata | Ehrenberg |
| A melosiraceous diatom | ||
| Melosiraceae | Melosira | Melosira teres | Brun |
| A melosiraceous diatom | ||
| Melosiraceae | Melosira | Melosira undulata | Kützing |
| A melosiraceous diatom | ||
| Naviculaceae | Caloneis | Caloneis westii | Hendey |
| A naviculaceous diatom |
| |
| Naviculaceae | Navicula | Navicula americana | F.W. Mills |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula angusta | Grunow |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula bacillum | Ehrenberg |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula commutata | Grunow ex A.Schmidt |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | †Navicula contendens | Mann |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula elegans | Grunow |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula instabilis | A.Schmidt |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | †Navicula pauper | Mann |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula placentula | Pantocsek |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | †Navicula pontifica | Mann |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | †Navicula protrudens | Mann |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | †Navicula pseudoaffinis | Mann |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula pseudobacillum | Grunow |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula pusilla | Donkin |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula radiosa | Kützing |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | †Navicula reversa | Mann |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula stauroptera | Schumann |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula subacuta | Ralfs |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | †Navicula substauroneis | Mann |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula tabellaria | Kützing |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula transversa | A.Schmidt |
| A naviculaceous diatom | ||
| Naviculaceae | Navicula | Navicula viridis | Kutzing |
| A naviculaceous diatom | ||
| Neidiaceae | Neidium | Neidium dubium | Cleve |
| A neidiaceous diatom | ||
| Neidiaceae | Neidium | Neidium iridescens | VanLandingham |
| A naviculaceous diatom | Navicula iridescens | |
| Neidiaceae | Neidium | Neidium iridis | Cleve |
| A neidiaceous diatom |
| |
| Pinnulariaceae | Pinnularia | Pinnularia gibba | Ehrenberg |
| A pinnulariaceous diatom |
| |
| Pinnulariaceae | Pinnularia | Pinnularia gracillima | W.Gregory |
| A pinnulariaceous diatom |
| file:Pinnularia gracillima as Navicula gracillima figured Plate30 fig 4.jpg|thumb|center|upright|Pinnularia gracillima |
| Pinnulariaceae | Pinnularia | Pinnularia major | Rabenhorst |
| A pinnulariaceous diatom |
| |
| Pinnulariaceae | Pinnularia | Pinnularia mesotyla | Ehrenberg |
| A pinnulariaceous diatom |
| |
| Pinnulariaceae | Pinnularia | Pinnularia nodosa | W.Smith |
| A pinnulariaceous diatom |
| |
| Pinnulariaceae | Pinnularia | Pinnularia rupestris | Hantzsch |
| A pinnulariaceous diatom |
| |
| Pinnulariaceae | Pinnularia | Pinnularia subcapitata | W.Gregory |
| A pinnulariaceous diatom |
| |
| Stauroneidaceae | Stauroneis | †Stauroneis acutissima | Mann |
| A stauroneidaceous diatom | file:Stauroneis acutissima syntype Plate30 fig 8.jpg|thumb|center|upright|Stauroneis acutissima | |
| Stauroneidaceae | Stauroneis | Stauroneis anceps | Ehrenberg |
| A stauroneidaceous diatom | file:Stauroneis anceps figured twin Plate31 fig 11.jpg|thumb|center|upright|Stauroneis anceps | |
| Stauroneidaceae | Stauroneis | Stauroneis phoenicenteron | Ehrenberg |
| A stauroneidaceous diatom | file:Stauroneis phoenicenteron twin figured Plate31 fig 12.jpg|thumb|center|upright|Stauroneis phoenicenteron | |
| Surirellaceae | Surirella | Surirella bifrons | Ehrenberg |
| A surirellaceous diatom | ||
| Surirellaceae | Surirella | Surirella inducta | A.W.F.Schmidt |
| A surirellaceous diatom | ||
| Surirellaceae | Surirella | Surirella striatula | Turpin |
| A surirellaceous diatom | ||
| Tabellariaceae | Tabellaria | Tabellaria fenestrata | Kützing |
| A tabellariaceous diatom | ||
| Tabellariaceae | Tabellaria | Tabellaria flocculosa | Kützing |
| A tabellariaceous diatom | ||
| Tabellariaceae | Tetracyclus | Tetracyclus ellipticus | Grunow |
| A tabellariaceous diatom | ||
Tetracyclus lacustris | Tetracyclus | Ralfs |
| A tabellariaceous diatom | - | ||
| incertae sedis | Diatoma | Diatoma grande | W. Smith |
| A diatom of uncertain familial affiliation | ||
| incertae sedis | Diatoma | Diatoma tenue var. hybrida | Grunow |
| A diatom of uncertain familial affiliation | ||
| incertae sedis | Diatoma | Diatoma vulgaris | Bory de Saint-Vincent |
| A diatom of uncertain familial affiliation |
| |
| incertae sedis | Gomphogramma | Gomphogramma rupestre | Braun in Rabenhorst |
| A bacillariophyceopus diatom of uncertain affiliation |
| |
| incertae sedis | Himantidium | Himantidium faba | Ehrenberg |
| A diatom of uncertain familial affiliation |
| |
| incertae sedis | Himantidium | Himantidium gracile | Ehrenberg |
| A diatom of uncertain familial affiliation |
| |
| incertae sedis | Himantidium | Himantidium minus | Kützing |
| A diatom of uncertain familial affiliation |
|