''Priabona'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of big-headed flies in the dipteran subfamily

Nephrocerinae Nephrocerinae is a subfamily of big-headed flies (insects in the family Pipunculidae). Genera * Tribe Nephrocerini ** Genus ''Nephrocerus'' Zetterstedt, 1838 * Tribe ''incertae sedis'' ** Genus '' Priabona'' Archibald, Kehlmaier & Mathewes, 201 ...

, within which it is one of only two genera. The genus contains a single described

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

, ''Priabona florissantius''. ''Priabona'' is known from a single

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

fossil from western North America.

History and classification

''Priabona'' is known from a compression-impression fossil preserved in fine shale of the

Florissant Formation The Florissant Formation is a sedimentary geologic formation outcropping around Florissant, Teller County, Colorado. The formation is noted for the abundant and exceptionally preserved insect and plant fossils that are found in the mudstones an ...

in Colorado. The formation is composed of successive lake deposits which have preserved a diverse assemblage of insects. The insects and plants suggest a climate similar to modern Southeastern North America, with a number of taxa represented that are now found in the subtropics to tropics and confined to the Old World. When ''Priabona'' was described, the Florissant formation was considered to be

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

in age, based on the flora and fauna preserved. Subsequent research and fossil descriptions permitted a re-examined dating, and by 1985 the formation had been reassigned to an Oligocene age. Further refinement of the formation's age using radiometric dating of sanidine crystals has resulted in an age of 34 million years, which places the formation in the Late Eocene Priabonian stage. At the time of description the

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 sever ...

specimen, number 3976 was deposited in the

Museum of Comparative Zoology A museum ( ; plural museums or, rarely, musea) is a building or institution that cares for and displays a collection of artifacts and other objects of artistic, cultural, historical, or scientific importance. Many public museums make thes ...

paleontology collections at

Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of high ...

. Placement of the group has changed several times, with '' Nepherocerus'' '' Metanephrocerus'' ''Priabona'' and '' Protonephrocerus'' being placed in the pipunculid subfamily

from 1948 until 2014. The placement of the tribe Protonephrocerini, containing ''Metanephrocerus'' and ''Protonephrocerus'', was challenged in 2014 by Kehlmaier, Dierick and Skevington who suggested inclusion of the genera made Nephrocerinae paraphyletic. As such they elevated the tribe Protonephrocerini to the subfamily rank as Protonephrocerinae, leaving only ''Nephrocerus'' and ''Priabona'' in Nephrocerinae. The species was originally placed into the genus ''Protonephrocerus'' by Frank M. Carpenter and F.M. Hull with their type description in 1939. The species was moved in 2014, based on a redescription of the type specimen, to the new genus ''Priabona''. The generic epithet "Priabona" is taken from ''Priabonian'', the age of the Florissant Formation.

Description

''P. florissantius'' has a body length of , with the details of the head mostly indistinct. There appears to be a notch between the eyes which runs halfway up the rear-side of the head capsule. The wings of the holotype are and hyaline overall, with a darkening of the pterostigma. The femurs of ''P. florissantius'' are unique in that they have several darkened spines on the undersides and which have setae on the front and upper sides, a feature absent in ''Nephrocerus''.

References

{{Taxonbar, from=Q20818061 Eocene insects Fossils of the United States Fossil taxa described in 2014 Prehistoric insects of North America Florissant Formation