Nannochoristidae is a family of

scorpionflies Mecoptera (from the Greek language, Greek: ''mecos'' = "long", ''ptera'' = "wings") is an Order (biology), order of insects in the superorder Endopterygota with about six hundred species in nine Family (biology), families worldwide. Mecopterans ...

with many unusual traits. It is a tiny,

relict A relict is a surviving remnant of a natural phenomenon. Biology A relict (or relic) is an organism that at an earlier time was abundant in a large area but now occurs at only one or a few small areas. Geology and geomorphology In geology, a r ...

family with a single extant genus, '' Nannochorista'', with eight species occurring in

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

, southeastern

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

Tasmania ) , nickname = , image_map = Tasmania in Australia.svg , map_caption = Location of Tasmania in AustraliaCoordinates: , subdivision_type = Country , subdi ...

, Argentina and Chile. Due to the groups distinctiveness from other scorpionflies, it is sometimes placed in its own order, the Nannomecoptera. Some studies have placed them as the closest living relatives of

fleas Flea, the common name for the order Siphonaptera, includes 2,500 species of small flightless insects that live as external parasites of mammals and birds. Fleas live by ingesting the blood of their hosts. Adult fleas grow to about long, ar ...

. Most mecopteran

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. The ...

e are

eruciform Eruciform (literally: "caterpillar-shaped") is the entomological term describing a certain class of shapes of insect larvae. Origin and application The word ''eruciform'' literally means "caterpillar-shaped" (from Latin "eruca", a caterpilla ...

, or shaped like caterpillars. Nannochoristid larvae, however, are elateriform, and have elongated and slender bodies. The larvae are aquatic, which is unique among mecopterans. The larvae are

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

y, hunting on the beds of shallow streams, primarily on the larvae of aquatic

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 ...

chironomids The Chironomidae (informally known as chironomids, nonbiting midges, or lake flies) comprise a family of nematoceran flies with a global distribution. They are closely related to the Ceratopogonidae, Simuliidae, and Thaumaleidae. Many species ...

. Fossils indicate that Nannochoristidae formerly had a wider distribution, being present in the Northern Hemisphere during the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

and Early

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

. Some research suggests the nannochoristids are the only

holometabolous Holometabolism, also called complete metamorphosis, is a form of insect development which includes four life stages: egg, larva, pupa, and imago (or adult). Holometabolism is a synapomorphic trait of all insects in the superorder Endopterygot ...

insects with true larval compound eyes . All other eyed larvae have

stemmata A simple eye (sometimes called a pigment pit) refers to a form of eye or an optical arrangement composed of a single lens and without an elaborate retina such as occurs in most vertebrates. In this sense "simple eye" is distinct from a multi-l ...

, which are structurally different from adult compound eyes with ommatidia. This is unusual, since most adult features are present as

imaginal disc An imaginal disc is one of the parts of a holometabolous insect larva that will become a portion of the outside of the adult insect during the pupal transformation. Contained within the body of the larva, there are pairs of discs that will form, ...

s in larvae and not formed until

pupation A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in thei ...

. The presence of compound eyes in nannochoristid larvae suggests the timing of the development of adult features can be initiated earlier in development, which has important implications for insect evolutionary development.

Phylogeny

The

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

of external relationships, based on a 2008 DNA and

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

analysis, shows the family as a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

sister A sister is a woman or a girl who shares one or more parents with another individual; a female sibling. The male counterpart is a brother. Although the term typically refers to a familial relationship, it is sometimes used endearingly to refer to ...

to the Siphonaptera (fleas) and rest of

Mecoptera Mecoptera (from the Greek: ''mecos'' = "long", ''ptera'' = "wings") is an order of insects in the superorder Endopterygota with about six hundred species in nine families worldwide. Mecopterans are sometimes called scorpionflies after their lar ...

, and more distantly related to the

(true flies) and

(scorpionflies). A more recent study in 2021 found Nannochoristidae to be the sister group to fleas, with strong support.

Genera

After Cao et al. 2022. * '' Nannochorista'' Tillyard, 1917 (8 species: Argentina, Chile, Tasmania, Australia, New Zealand) Koonwarra fossil bed, Australia, Early Cretaceous (

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ago), a ...

) * †'' Dahurochorista'' Sukatsheva 1985 (one species: Ichetuy Formation, Russia, Late Jurassic ( Oxfordian) * †'' Dahurolarva'' Sukatsheva 1985 (one species: Ichetuy Formation, Oxfordian, Russia) (based on larvae only) * †'' Itaphlebia'' Sukatsheva 1985 (14 species)

Itat Formation The Itat Formation ( Russian: итатская свита) is a geologic formation in western Siberia. It was deposited in the Bajocian to Bathonian ages of the Middle Jurassic. Dinosaur remains are among the fossils that have been recovered from ...

, Russia, Middle Jurassic (

Bathonian In the geologic timescale the Bathonian is an age and stage of the Middle Jurassic. It lasted from approximately 168.3 Ma to around 166.1 Ma (million years ago). The Bathonian Age succeeds the Bajocian Age and precedes the Callovian Age. Strat ...

Daohugou The Haifanggou Formation (), also known as the Jiulongshan Formation (), is a fossil-bearing rock deposit located near Daohugou () village of Ningcheng County, in Inner Mongolia, northeastern China. The formation consists of coarse conglomerates ...

, China, Middle Jurassic (

Callovian In the geologic timescale, the Callovian is an age and stage in the Middle Jurassic, lasting between 166.1 ± 4.0 Ma (million years ago) and 163.5 ± 4.0 Ma. It is the last stage of the Middle Jurassic, following the Bathonian and preceding the ...

Karabastau Formation The Karabastau Formation ( kk, Qarabastaý svıtasy) is a geological formation and lagerstätte in the Karatau Mountains of southern Kazakhstan whose strata date to the Middle to Late Jurassic. It is an important locality for insect fossils that ...

, Kazakhstan, Late Jurassic (Oxfordian) Doronino Formation, Russia, Early Cretaceous (

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma (million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is preceded ...

) * †'' Namdyrus'' Sukacheva 1993 Khaya Formation, Russia, Late Jurassic (

Tithonian In the geological timescale, the Tithonian is the latest age of the Late Jurassic Epoch and the uppermost stage of the Upper Jurassic Series. It spans the time between 152.1 ± 4 Ma and 145.0 ± 4 Ma (million years ago). It is preceded by the K ...

) * †'' Tarantogus'' Sukatsheva, 1985 Itat Formation, Russia, Bathonian (based on larvae only) * †'' Undisca'' Sukatsheva, 1990 Glushkovo Formation, Russia, Tithonian

References

{{Taxonbar, from=Q1942055 Mecoptera Insect families