''Agastomyrma'' 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 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 formicid in the ant subfamily

Myrmicinae Myrmicinae is a subfamily of ants, with about 140 extant genera; their distribution is cosmopolitan. The pupae lack cocoons. Some species retain a functional sting. The petioles of Myrmicinae consist of two nodes. The nests are permanent and ...

known from the fossil species ''Agastomyrma laticeps'' found in eastern Asia.

History and classification

''A. laticeps'' is known from a single

queen ant A queen ant (formally known as a gyne) is an adult, reproducing female ant in an ant colony; generally she will be the mother of all the other ants in that colony. Some female ants, such as the ''Cataglyphis'', do not need to mate to produce offs ...

found in Russia. The specimen was described from a

compression fossil A compression fossil is a fossil preserved in sedimentary rock that has undergone physical compression. While it is uncommon to find animals preserved as good compression fossils, it is very common to find plants preserved this way. The reason f ...

preserved in

diatomite Diatomaceous earth (), diatomite (), or kieselgur/kieselguhr is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging from more than 3 μm to le ...

deposits of the Bol’shaya Svetlovodnaya site. The site is exposed on the bank of Barachek Creek upstream from the creeks confluence with the Bol’shaya Svetlovodnaya River in the

Pozharsky District Pozharsky District (russian: Пожа́рский райо́н) is an administrativeLaw #161-KZ and municipalLaw #191-KZ district (raion), one of the twenty-two in Primorsky Krai, Russia. It is located in the northern and northwestern parts of t ...

, on the Pacific Coast of Russia. The fossil-bearing rocks preserve possibly

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 ...

plants and animals which lived in and around a small lake near a volcano. The site has been attributed to either the Maksimovka or Salibez Formations and compared to the Bembridge Marls and

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 ...

, both of which are Priabonian in age. At the time of description, the 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 seve ...

queen specimen, numbers PIN 3429/1178 and PIN 3429/1173, was preserved in the A. A. Borissiak Paleontological Institute collections, part of the

Russian Academy of Sciences The Russian Academy of Sciences (RAS; russian: Росси́йская акаде́мия нау́к (РАН) ''Rossíyskaya akadémiya naúk'') consists of the national academy of Russia; a network of scientific research institutes from across t ...

. The fossil was first described by the trio of paleomyrmecologists Gennady Dlussky,

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 ...

and Ksenia Perfilieva. In the type description, Dlussky, Rasnitsyn and Perfilieva coined the genus name ''Agastomyrma'' from a combination of the

Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

''agastus'' which means "pleasing" and

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

''Myrmica'' meaning "ant". 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, bo ...

is derived the Latin ''laticeps'' that translates to "with a wide head". ''Agastomyrma'' is one of two extinct ant genera described by Dlussky ''et al'' from Bol’shaya Svetlovodnaya fossils in the 2015 paper. The other genus '' Biamomyrma'' is also a

myrmicine Myrmicinae is a subfamily of ants, with about 140 extant genera; their distribution is cosmopolitan. The pupae lack cocoons. Some species retain a functional sting. The petioles of Myrmicinae consist of two nodes. The nests are permanent and i ...

, and differs from ''Agastomyrma'' in the structuring of the petiole and in the relative sizing of the queens head.

Description

The ''A. laticeps'' queen is preserved as a dorsal compression showing the upper surface of the head, thorax and abdomen, without fore-wings or antennae. The body length as preserved is estimated at , though portions of the head and the gaster are missing. ''A. laticeps'' is distinguished by the large size of the head relative to the body, the head being long while the

mesosoma The mesosoma is the middle part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the metasoma. It bears the legs, and, in the case of winged insects, the wings. In hymenopterans of t ...

is . The head has rounded back corners and a straight back edge.

References

{{Taxonbar, from=Q28432136 Fossil taxa described in 2015 Agastomyrma Fossil ant genera Eocene insects Prehistoric insects of Asia