''Metanephrocerus'' 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
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 advanced ...
n subfamily
Protonephrocerinae, for which it is one of only two
genera
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 nomenclat ...
. The genus contains four 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 ...
, ''Metanephrocerus belgardeae'', ''M. collini'', ''M. groehni'', and ''M. hoffeinsorum''. ''Metanephrocerus'' is known from a group of
Middle Eocene fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s which were found in
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
and a single early Eocene fossil from North America.
History and classification
When first described, ''Metanephrocerus'' was known only from two separate fossils, 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 several ...
female, and the female
paratype were fossilized as
inclusions in transparent chunks of
Baltic amber
The Baltic region is home to the largest known deposit of amber, called Baltic amber or succinite. It was produced sometime during the Eocene epoch, but exactly when is controversial. It has been estimated that these forests created more than 1 ...
.
Baltic amber is approximately forty-six million years old, having been deposited during the
Lutetian
The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the Midd ...
stage of the
Middle Eocene. There is debate on what plant family produced the amber, with evidence supporting relatives of either an ''
Agathis
''Agathis'', commonly known as kauri or dammara, is a genus of 22 species of evergreen tree. The genus is part of the ancient conifer family Araucariaceae, a group once widespread during the Jurassic and Cretaceous periods, but now largely re ...
'' or a ''
Pseudolarix
''Pseudolarix'' is a genus of coniferous trees in the pine family Pinaceae containing three species, the extant ''Pseudolarix amabilis'' and the extinct species '' Pseudolarix japonica'' and '' Pseudolarix wehrii''. ''Pseudolarix'' species are c ...
'' relative.
Fossils of the type species, ''M. collini'', were first studied by American entomologist
Frank M. Carpenter
Frank Morton Carpenter (September 6, 1902 – January 18, 1994) was an American entomologist and paleontologist. He received his PhD from Harvard University, and was curator of fossil insects at the Harvard Museum of Comparative Zoology for 60 y ...
and F. M. Hull who placed the new species in the fossil genus ''
Protonephrocerus
''Protonephrocerus'' is a genus of flies belonging to the family Pipunculidae
Pipunculidae is a family of flies (Diptera) commonly termed big-headed flies, a reference to the large (holoptic) eyes, which cover nearly the entire head. The fami ...
''. Carpenter and Hull's 1939
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 species was published in the monograph series ''
Bernstein-Forschungens''.
The species was moved to the new genus ''Metanephrocerus'' in a 1948 paper by Martin L Aczél, and since that time both the type specimens have been lost and are considered possibly destroyed. After the ''M. collini'' description, 75 years passed before an additional three related species were described. Two of those, ''M. groehni'' and ''M. hoffeinsorum''. were described from solitary fossil inclusions in Baltic amber. The 2014 descriptions were made by Christian Kehlmaier, Manuel Dierick and Jeffrey H. Skevington, based on detailed CT scans of the specimens. They chose the
species name "groehni" is a patronym honoring Carsten Gröhn, who supported the research of the authors, and who was the owner of the specimen before description. The fossil was to be deposited into the collections of the
Geologisch-Paläontologisches Institut und Museum der Universität Hamburg Similarly, the epithet of the second species "hoffeinsorum" is a patronym for Christel and Hans-Werner Hoffeins for the donation of the type fossil to the
Senckenberg Deutsches Entomologisches Institut and for their support of the authors research.
The third related species, ''M. belgardeae'', bringing the total to four, was described from a compression fossil found in 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 ...
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 ...
lagerstätten, its discovery expanding both the temporal range and geographic range.
''M. belgardeae'' was described by S. Bruce Archibald, Christian Kehlmaier, and Rolf Mathewes from a single partial female. 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 ...
is a matronym of Azure Rain Belgarde, who collected the type specimen, SR 08-06-02, and donated it to the
Stonerose Interpretive Center.
Placement of the group has changed several times, with ''Metanephrocerus'' and ''Protonephrocerus'' being placed in the pipunculid 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 ...
as tribe Protonephrocerini from 1948 until 2014. The placement of the tribe was challenged in 2014 by Kehlmaier, Dierick and Skevington who suggested inclusion of the genera made Nephrocerinae
paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...
. As such they elevated the tribe Protonephrocerini to the subfamily rank as Protonephrocerinae, leaving only ''
Nephrocerus
''Nephrocerus'' is a genus of flies belonging to the family Pipunculidae.
The species of this genus are found in Europe, Asia and Northern America.
Species
*'' Nephrocerus acanthostylus'' Skevington, 2005
*'' Nephrocerus atrapilus'' Skevington, ...
'' and ''
Priabona'' in Nephrocerinae.
Description
''Metanephrocerus belgardeae'' is a large species, with a wing length of , and a
hyaline
A hyaline substance is one with a glassy appearance. The word is derived from el, ὑάλινος, translit=hyálinos, lit=transparent, and el, ὕαλος, translit=hýalos, lit=crystal, glass, label=none.
Histopathology
Hyaline cartilage is ...
wing coloration, broken by a smokey tone to the
pterostigma
The pterostigma (plural: pterostigmata) is a group of specialized cells in the outer insect wing, wings of insects, which are often thickened or coloured, and thus stand out from other cells. It is particularly noticeable in dragonfly, dragonfli ...
and basal area of the wing. The wing has a long third section of the costal vein and the median vein that is long and straight. The females abdomen is approximately long, with short
seta
In biology, setae (singular seta ; from the Latin word for "bristle") are any of a number of different bristle- or hair-like structures on living organisms.
Animal setae
Protostomes
Annelid setae are stiff bristles present on the body. Th ...
e on the
tergites, which grade to longer
tergites on the first and second tergites. The short abdominal setae are distinct for the genus and exclude the species from other pipnculid genera.
''M. collini'' was known from 2 female specimens, which had hyaline wings with colored pterostigma.
''M. groehni'' is a nearly complete male fly with a total body length of , and is only missing the tip of the left hind leg. The hind legs show a distinct
chaetotaxy to the setae, with front sides having setae that are longer than the femur is wide. The eyes connect for three times the length of the
frons
Insect morphology is the study and description of the physical form of insects. The terminology used to describe insects is similar to that used for other arthropods due to their shared evolutionary history. Three physical features separate insec ...
. The wings are , though the wings are folded slightly and difficult to fully assess. The halters are darkened at the base and on the knob.
''M. hoffeinsorum'' is a whole male, though large portions of it are enclosed in white mold and the specimen has a total length of . The wings show a length of and have a covering of
microtrichia
Insect morphology is the study and description of the physical form of insects. The terminology used to describe insects is similar to that used for other arthropods due to their shared evolutionary history. Three physical features separate insec ...
. As with ''M. groehni'' the halters have darkened knobs and bases and the
pteropleuron has 6 hairs on it. Tergite three of the abdomen is 1.3 times as long as tergite two.
References
{{Taxonbar, from=Q18926236
Ypresian insects
Fossils of the United States
Fossil taxa described in 2014
Fossil taxa described in 1939
Prehistoric insects of Europe
Prehistoric insects of North America
Pipunculidae
Baltic amber
Priabonian insects
†
Taxa named by Frank M. Carpenter
Klondike Mountain Formation
Prehistoric Diptera genera