Ypresiosirex
Ypresiosirex is an extinct genus of sawfly in the horntail family Siricidae. The genus is solely known from a single Eocene fossil found in North America. At the time of its description the new genus was composed of a single species named Ypresiosirex orthosemos.
History and classification
Y. orthosemos is known only from one fossil, a part and counterpart holotype, specimen number RBCM.EH2015.004.0001.001A&B, which is housed in the collections of the Royal [British Columbia Museum] in Victoria, British Columbia. Ypresiosirex was described from a specimen which was recovered from outcrops of the early Eocene, Ypresian McAbee Fossil Beds near Cache Creek, British Columbia. The unnamed formation outcropping at the McAbee Fossil Beds preserve an upland temperate flora that was first interpreted as being Microthermal, although further study has shown them to be more mesothermal in nature. The plant community preserved in the McAbee Fossil Beds site is mostly broadleaf pollen with alder and elm dominating, and may represent a successional forest involving multiple volcanic ash eruptions.Ypresiosirex was first studied by the paleoentomologists S. Bruce Archibald from Simon Fraser University in Burnaby, British Columbia and Alexandr Rasnitsyn of the A. A. Borissiak Paleontological Institute. Their 2015 type description of the new genus and species was published in the journal Canadian Entomologist. The genus name Ypresiosirex was coined by the researchers as a combination of Ypresian, the age of the fossil, and Sirex a horntail genus name. The specific epithet orthosemos is derived from Greek meaning "with vertical stipes", alluding to the corrugated texture of the wing membrane at its base.
Ypresiosirex orthosemos was one of three sawfly species described in Archibald & Rasnitsyn's 2015 paper, the other two being Ulteramus republicensis and Cuspilongus cachecreekensis, from the Klondike Mountain Formation and the McAbee fossil beds respectively.