''Ypresiosirex'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of sawfly in the

horntail Horntail or wood wasp are any of the 150 non-social species of the hymenopteran family Siricidae, a type of wood-eating sawfly. The common name "horntail" derives from the stout, spine-like structure at the end of the adult's abdomen, which is u ...

family Siricidae. The genus is solely known from a single

Eocene The Eocene ( ) Epoch is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene' ...

fossil found in

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. 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 A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, specimen number RBCM.EH2015.004.0001.001A&B, which is housed in the collections of the Royal British Columbia Museum in

Victoria, British Columbia Victoria is the capital city of the Canadian province of British Columbia, on the southern tip of Vancouver Island off Canada's Pacific coast. The city has a population of 91,867, and the Greater Victoria area has a population of 397,237. Th ...

. ''Ypresiosirex'' was described from a specimen which was recovered from outcrops of the early Eocene,

Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

McAbee Fossil Beds The McAbee Fossil Beds is a Heritage Site that protects an Eocene Epoch fossil locality east of Cache Creek, British Columbia, Canada, just north of and visible from Provincial Highway 97 / the Trans-Canada Highway ( Highway 1). The McAbee Fos ...

near

Cache Creek, British Columbia Cache Creek is a historic transportation junction and incorporated village northeast of Vancouver in British Columbia, Canada. It is on the Trans-Canada Highway in the province of British Columbia at a junction with Highway 97. The same int ...

. 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 Elms are deciduous and semi-deciduous trees comprising the flowering plant genus ''Ulmus'' in the plant family Ulmaceae. They are distributed over most of the Northern Hemisphere, inhabiting the temperate and tropical-montane regions of North ...

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 Alexandr Pavlovich Rasnitsyn (Russian: Александр Павлович Расницын) is a Russian entomologist, expert in palaeoentomology, and Honored Scientist of the Russian Federation (2001). His scientific interests are centered on ...

of the A. A. Borissiak Paleontological Institute. Their 2015

type description A species description is a formal description of a newly discovered species, usually in the form of a scientific paper. Its purpose is to give a clear description of a new species of organism and explain how it differs from species that have be ...

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 ''Sirex'' is a genus of wasps in the family Siricidae, the horntails or wood wasps. They inject eggs with fungal endosymbionts into wood. The fungus is contained in a mycangium which nourishes it with secretions, and in turn it digests wood for ...

'' a horntail genus name. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''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 ''Cuspilongus'' is an extinct genus of parasitic wasp in the sawfly family Cephidae. At the time of its description the new genus comprised a single species named ''Cuspilongus cachecreekensis'', known from an Eocene fossil found in North Americ ...

'', from the

Klondike Mountain Formation The Klondike Mountain Formation is an Early Eocene (Ypresian) geological formation located in the northeast central area of Washington state. The formation, named for the type location designated in 1962, Klondike Mountain north of Republic, Wash ...

and the McAbee fossil beds respectively.

Description

The single described female of ''Ypresiosirex'' is mostly complete, missing the very apical section of the

ovipositor The ovipositor is a tube-like organ used by some animals, especially insects, for the laying of eggs. In insects, an ovipositor consists of a maximum of three pairs of appendages. The details and morphology of the ovipositor vary, but typical ...

. The female has a body length of approximately and an overall preserved length of with the partially preserved ovipositor included. The body is dark in coloration overall, with an area of the mid-abdomen possibly lighter, though the change in color may be the result of preservation showing the ventral color and not the dorsal color. The fore-wings show darkening near the base which grades to hyaline for the rest of the membrane. In some areas of the head and thorax preservation is detailed enough to show the surfaces had a patterning of shallow densely spaced pits. Placement of the genus into Siricidae was based on the modified abdomen tip which forms a cornus. The basal area of the wings shows distinct corrugation running from the leading edge to the rear edge, which is not seen in any other hymenopterans.

References

{{Taxonbar, from=Q27271393 Ypresian insects Fossils of British Columbia Fossil taxa described in 2015 Prehistoric insects of North America † Tranquille Formation