Promastacidae

''Promastax'' is a genus of "monkey grasshoppers" belonging to the extinct monotypic family Promastacidae and containing the single species ''Promastax archaicus''. The species is dated to the Early Eocenes Ypresian stage and has only been found at the type locality in east central British Columbia.

History and classification

The holotype fossil of ''Promastax archaicus'' was collected by Lawrence Lambe from outcrops of the Horsefly Shales at the horsefly Mine on 20 July 1906, and then subsequently described by Anton Handlirsch in 1910. The type description was published in his ''Canadian fossil Insects. 5. Insects from the Tertiary lake deposits of the southern interior of British Columbia'', along with a number of other Okanagan Highlands insect species. Handlirsch did not include the etymological derivation of genus or species names in the volume.

Handlirsch initially grouped ''Promastax'' into the orthopteran superfamily Acridioidea without making a more precise placement. He noted a gross similarity with the Acridinae subfamily as then defined, but that it differed in the venation of the wing apex. The short cubital region he likened to " Mastacinae" genera, but again noted the significant differences within the venation of ''Promastax archaicus'' as reason not to place the genus there. The genus was not discussed in any depth again until Kevan and Wighton (1981) described a series of orthopteroid fossils from the Paleocene Paskapoo Formation in central Alberta. Along with the monotypic '' Promastacoides'', ''Promastax'' was referred by Kevan and Wighton (1981) to a new family Promastacidae which they placed in the superfamily Eumastacoidea. Kevan and Wighton identified ''Promastacoides'' as a very primitive member of Eumastacoidea and together with ''Promastax'' shared a close relationship to the family " Eruciidae". However ''Promastacoides'' was subsequently identified as a Susumaniinae stick insect leaving the family Promastacidae with only ''Promastax''. The quality of the characters defined for the erection of Promastacidae were noted as few and of poor quality by Schubnel ''et al''. (2020), and they stated that the family should be revised.

Distribution and paleoenvironment

''Promastax archaicus'' lived in the forests surrounding the Horsefly Shales lake system during the Early Eocene Climatic Optimum. The horsefly shales have not been radiometrically dated, but based on shared floral and faunal taxa found in other Early Eocene, Ypresian, age Okanagan Highlands sites, Horsefly is assumed to be contemporaneous. The lake was subject to season summer algal bloom of the diatom ''Eoseira wilsonii'' , with the polysaccharide slime grown by ''E. wilsonii'' suggested to have enhanced the preservation quality of organisms that were coated with slime films before entombment in the lake bottom.

The greater Eocene Okanagan 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. 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 then the coeval