Promastax

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Promastax
Temporal range: Ypresian
Promastax archaicus 1910 illustration
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Orthoptera
Suborder: Caelifera
Family: †Promastacidae
Genus: †Promastax
Handlirsch, 1910
Species:
†P. archaicus
Binomial name
†Promastax archaicus
Handlirsch, 1910
Erucius sp. monkey hopper

Promastax is a

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.[1]

Handlirsch initially grouped Promastax into the orthopteran superfamily

stick insect[3] leaving the family Promastacidae with only Promastax.[4] 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.[5]

Distribution and paleoenvironment

Promastax archaicus lived in the forests surrounding the

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.[8]

The greater

biotas 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 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 0.8 km (0.50 mi), but higher.[9] Estimates of the mean annual temperature have been derived from leaf margin analysis (LMA) of the Horsefly shales with the LMA returning a mean annual temperature of approximately 10.4 ± 2.2 °C (50.7 ± 4.0 °F). The estimated cold month mean temperature during the winter is placed at approximately 5.3 ± 2.8 °C (41.5 ± 5.0 °F). These estimates are 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 Horsefly suggests a mean annual precipitation amount of 105 ± 47 cm (41 ± 19 in).[9]

The Okanagan Highlands fossil sites, which includes the Eocene formations between the

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.[11]

Description

modern grasshopper wings with the major veins labeled

The only described fossil of Promastax archaicus is the holotype forewing, which is incomplete, missing the basal region of the wing. The preserved length is given by Handlirsch (1910) as 18 mm (0.71 in) with an estimated complete length of 25 mm (0.98 in)[1] though Kevan and Wighton (1981) suggested the full length might be longer.[2] The wing has a rounded apical margin, and a width that does not exceed being a quarter that of the length. Along the posterior margin, the anal area, marked as A in the illustration, extends less than half the wing length, while along the costal margin the costal vein, marked as C, also extends about halfway along the wing. The precostal area, the region between the costal vein and the wing edge is described as large, as is the costal region, the area between the costal and subcostal vein. The subcostal, marked as Sc, and Radius, marked as R, run close to each other, with only a narrow space between before the subcostal turns upwards and terminates at the wing margin.[1] The sector radii, marked Rs, forks two times, with the main Rs vein angling upwards to the costal margin before curving slightly to the posterior and terminating at the wings apical margin. On the costal side the main Rs, a series of four small veins branch off near the end of the vein, while two larger branches fork off from the posterior side more basally and angle towards the posterior margin. The medial, marked M, and cubital, marked Cu, veins are each separated by larger open spaces, with only a single branch from the medial vein forking off the posterior side between it and the cubital vein.[1]

References

  1. ^
    doi:10.4095/100486
    .
  2. ^
    doi:10.1139/e81-170
    .
  3. doi:10.4202/app.2009.1108
    .
  4. ^ "†family Promastacidae Kevan and Wighton 1981 (grasshopper)". Paleobiology Database. Retrieved 9 May 2022.
  5. doi:10.4202/app.00676.2019
    .
  6. S2CID 134962126
    .
  7. S2CID 85743832
    .
  8. doi:10.1139/e04-051
    .
  9. ^
    doi:10.1139/e04-100
    .
  10. ^ a b 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.
  11. S2CID 225050834
    .
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