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Libotonius is an extinct genus of Percopsiformes fish which lived during the early Eocene epoch and contains two species, the type species Libotonius blakeburnensis plus Libotonius pearsoni. Libotonius has been variously treated as part of the expanded Percopsidae family, or formerly as a member of the monotypic family Libotoniidae.
The second described species, Libotonius pearsoni known exclusively by fossils from the Klondike Mountain Formation exposed northwest of Republic in Ferry County, northeast Central Washington. The outcrop along Toroda Creek is considered to be the same general age as the Republic sites of "Boot Hill", UWBM B4131, and "Corner lot", site A0307. Tuffs of the Klondike Mountain Formation had been dated to , the youngest of the Okanagan Highlands sites, though a revised oldest age of was given based on isotopic data published in 2021.
Collection work was performed in the 1970's by Mark M. V. Wilson across the Okanagan Highlands fossil sites in both British Columbia and Washington, culminating in a series of publications on the Highlands fish fauna over the next two decades. The first major work published was Wilson's 1977 monograph Middle Eocene freshwater fishes from British Columbia covering almost all of the fish found in the highlands and initially naming several taxon, including Libotonius.
Description of the genus and type species was based on the holotype, "ROM 11157 A&B", plus a series of seven all collected by Wilson during 1970 and 1971 field work at the Blakeburm mine. He also identified a number of additional specimens which were collected by other people and not included in the type series. An isolated partial specimen collected in 1941 by Harington M. A. Rice and 5 additional complete fish donated by Réne Liboton were all collected from around Whipsaw Creek south of Princeton. Wilson coined the genus name Libotonius as a patronym honoring Mr Liboton, a fossil museum and rock shop owner from Vaseaux Lake who contributed L. blakeburnensis and Wilsonium specimens for study. Wilson did not elaborate on the origin of the species name "blakeburnensis". Wilson designated the Blakeburn Mine, ROM site L95, south of Coalmont the type locality of the genus and species in the Allenby Formation.
Two years later Wilson (1979) published the description of a second Libotonius species, Libotonius pearsoni based on fossils collected from Pearson's site along Toroda Creek. While the original specimens identified as Erismatopterus were lost by 1979, and thus not accessible to Wilson, he considered them to more likely belong to L. pearsoni than Erismatopterus. His description was based on the holotype, "UA 13466" with the paratypes "UA 14765" and "UA 13469", while an additional thirteen fish were listed as additional material specimens outside the type series. All of the specimens were collected during 1977 and 1978 fieldwork. Given the history of the Toroda creek Site, Wilson chose the species name pearsoni in recognition of R. C. Pearson and his initial work discovering the site.
Lance Grande, in his 1988 description of Mcconichthys, listed the Libotonius species as belonging to the family "Libotoniidae", but did not provide a formal description of the family. He cited the work of Colin Patterson and Donn Eric Rosen, then "in press" and released in 1989, where they state finding no convincing characters to place Libotonius within the family Percopsidae. The uncertain placement of the genus was maintained by Murrey and Wilson (1999) who agreed with Patterson and Rosens placement of Libotonius basally as a Percopsiformes stem group. In Murry and Wilsons phylogenic assessments, they recovered Libotonius in a polytomy with both Aphredoderidae and Percopsidae. By 2013, the placement of Libotonius was again shifting, this time back towards Percopsidae in various chapters of the book Mesozoic Fishes 5 – Global Diversity and Evolution. In the chapter by W. Calvin Borden, Terry Grande and W. Leo Smith which discusses Paracanthopterygii caudal fin osteology Borden et al justified the placement based on the skeletal similarities between Libotonius and the other core percopsids. In the phylogeny they produced, based on their interpretation of the evolution of 26 differing skeletal characters, Libotonius was basal in the Percopsidae, with Mcconichthys basal to the sister clade that included Aphredoderus. (2025). 9783899371598, Verlag Dr. Friedrich Pfeil. ISBN 9783899371598 However in their earlier chapter on the history of Paracanthopterygii and possibilities of molecular phylogenetics, they list the studied specimens of Libotonius under "Libotoniidae".
Three years later Richard Van der Laan's 2016 Family-group names of fossil fishes listed "Libotoniidae" as a junior synonym of Percopsidae, but did not give a rational or reference for the placement. The 2016 Fishes of the World 5th edition discusses Libotonius within the paragraph on Percopsidae as a percopsid that is sometimes treated in the separate family "Libotoniidae". (2025). 9781118342336, John Wiley & Sons. ISBN 9781118342336 The placement in Percopsidae was uncertain in Murray et al (2020) who presented to cladograms in relation to the placement of the Cretaceous genus Lindoeichthys from Alberta. In the unconstrained cladogram, the two Libotonius are successive sister clades to the core Percopsidae within the family, however in the 50% majority rule
cladogram, both species are placed just outside the family in polytomy with Percopsidae and Mcconichthys, Murray et al treating them as either sisters to the family or included in an expanded clade.
The Republic and Princeton upland lake systems were surrounded by a warm temperate ecosystem with nearby volcanism. The highlands likely had a Mesic habitat Microthermal to mesothermal climate, in which winter temperatures rarely dropped low enough for snow, and which were seasonably equitable. The paleoforests 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 Tropical forest ecosystems. Estimates of the elevation range between higher than the coastal forests. This is consistent with the paleoelevation estimates for the lake systems, which range between , which is similar to the modern elevation , but higher.
Estimates of the Climate have been derived from climate leaf analysis multivariate program (CLAMP) and leaf margin analysis (LMA) of the Republic and Princeton paleofloras. The CLAMP results after multiple linear regressions for Republic gave a mean annual temperature of approximately , with the LMA giving . CLAMP results from Princeton returned the lower , confirmed by the LMA with a mean annual temperature of . Both Formations are lower than the mean annual temperature estimates given for the coastal Puget Group, which is estimated to have been between . The bioclimatic analysis for Republic and Princeton suggests mean annual precipitation amounts of and respectively.
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