''Priabona'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of big-headed flies in the

diptera Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advance ...

n subfamily

Nephrocerinae Nephrocerinae is a subfamily of big-headed flies (insects in the family Pipunculidae). Genera * Tribe Nephrocerini ** Genus ''Nephrocerus ''Nephrocerus'' is a genus of flies belonging to the family Pipunculidae. The species of this genus ar ...

, within which it is one of only two

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

. The genus contains a single described

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

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

Late Eocene The Priabonian is, in the International Commission on Stratigraphy, ICS's geologic timescale, the latest age (geology), age or the upper stage (stratigraphy), stage of the Eocene epoch (geology), Epoch or series (stratigraphy), Series. It spans ...

fossil from western North America.

History and classification

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

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

of the Florissant Formation 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 The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

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 The Priabonian is, in the ICS's geologic timescale, the latest age or the upper stage of the Eocene Epoch or Series. It spans the time between . The Priabonian is preceded by the Bartonian and is followed by the Rupelian, the lowest stage ...

stage. At the time of description the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

specimen, number 3976 was deposited in the

Museum of Comparative Zoology The Museum of Comparative Zoology (formally the Agassiz Museum of Comparative Zoology and often abbreviated to MCZ) is a zoology museum located on the grounds of Harvard University in Cambridge, Massachusetts. It is one of three natural-history r ...

paleontology collections at

Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...

. Placement of the group has changed several times, with '' Nepherocerus'' ''

Metanephrocerus ''Metanephrocerus'' is an extinct genus of big-headed flies in the dipteran subfamily Protonephrocerinae, for which it is one of only two genera. The genus contains four described species, ''Metanephrocerus belgardeae'', ''M. collini'', ''M. gro ...

'' ''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 Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic ''with respect to'' the excluded subgroups. In co ...

. 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