''Apterostigma electropilosum'' is an extinct

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 ...

ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of ...

in the subfamily Myrmicinae known from a single possibly

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 ...

fossil found on Hispaniola. ''A. electropilosum'' is one of only two species of the ant genus ''

Apterostigma ''Apterostigma'' is a genus of New World ants of the subfamily Myrmicinae. Two species have been described from fossils preserved in Dominican amber, while the others are extant. They are fungus-growing ants, though, unlike the majority of oth ...

'' and one of five attini species to have been described from fossils found in

Dominican amber Dominican amber is amber from the Dominican Republic derived from resin of the extinct tree '' Hymenaea protera''. Dominican amber differentiates itself from Baltic amber by being nearly always transparent, and it has a higher number of fossil inc ...

History and classification

''Apterostigma electropilosum'' is known from a solitary fossil insect which is an

inclusion Inclusion or Include may refer to: Sociology * Social inclusion, aims to create an environment that supports equal opportunity for individuals and groups that form a society. ** Inclusion (disability rights), promotion of people with disabiliti ...

in a transparent chunk of

. The amber was produced by the extinct '' Hymenaea protera'', which formerly grew on Hispaniola, across northern South America and up to southern Mexico. The specimens were collected from an undetermined amber mine in fossil bearing rocks of the

Cordillera Septentrional The Cordillera Septentrional is a mountain range that runs parallel to the north coast of the Dominican Republic, with extensions to the northwest as Tortuga (Haiti), Tortuga island in Haiti, and to the southeast through lowlands to where it rises ...

mountains, northern

Dominican Republic The Dominican Republic ( ; es, República Dominicana, ) is a country located on the island of Hispaniola in the Greater Antilles archipelago of the Caribbean region. It occupies the eastern five-eighths of the island, which it shares with ...

. The amber dates from at least the

Burdigalian The Burdigalian is, in the geologic timescale, an age or stage in the early Miocene. It spans the time between 20.43 ± 0.05 Ma and 15.97 ± 0.05 Ma (million years ago). Preceded by the Aquitanian, the Burdigalian was the first and longest w ...

stage of the Miocene, based on studying the associated fossil

foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...

and may be as old as the Middle Eocene, based on the associated fossil

coccoliths Coccoliths are individual plates or scales of calcium carbonate formed by coccolithophores (single-celled phytoplankton such as '' Emiliania huxleyi'') and cover the cell surface arranged in the form of a spherical shell, called a ''coccosphere'' ...

. This age range is due to the host rock being secondary deposits for the amber, and the Miocene the age range is only the youngest that it might be. 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 ...

amber specimen, number DR-14-984, is currently preserved in the amber collections of the

US National Museum The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. In 2021, with 7 ...

, and is labeled as part of the

Smithsonian Institution The Smithsonian Institution ( ), or simply the Smithsonian, is a group of museums and education and research centers, the largest such complex in the world, created by the U.S. government "for the increase and diffusion of knowledge". Founded ...

ant database as number 00443127. The fossil was first studied by entomologist Ted R. Schultz of the National Museum of Natural History with his 2007 type description of the new species being published in the journal ''Memoirs of the American Entomological Institute''. The specific epithet ''electropilosum'' is a combination of the

Latin Latin (, or , ) is a classical language belonging to the 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 the power of the ...

''electrum'' meaning "amber" and pilosum, the ''Apterostigma''

species group In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

which ''A. electropilosum'' it part of. Prior to the species formal description in 2007, no ''Apterostigma'' species were known from the fossil record, however three other Attini species were already known from Dominican Amber, '' Trachymyrmex primaevus'', '' Cyphomyrmex maya'', and '' Cyphomyrmex taino''. Schultz's paper described a second Dominican amber ''Apterostigma'' species, '' A. eowilsoni''. Bringing the total Attini fossil record to five species. Apterostigma pilosum casent0603533 profile 1

Apterostigma pilosum casent0603533 profile 1

Description

The ''Apterostigma electropilosum'' specimen is well preserved with an estimated Weber's length of and a head length of . The overall coloration of the species is hard to determine due to a sporadic microscopic coating of fine bubbles, possibly of oil or other liquid from punctures in the

integument In biology, an integument is the tissue surrounding an organism's body or an organ within, such as skin, a husk, shell, germ or rind. Etymology The term is derived from ''integumentum'', which is Latin for "a covering". In a transferred, or ...

after entombment by the resin. The body has a fine covering of simple upright

setae 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. ...

which reach a total length of . The head capsule shows a clypeus which is smooth and shiny, a feature seen in the living ''pilosum'' group of ''Apterostigma'' species. The

occiput The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the cereb ...

, rear area of the head capsule, is elongated to a slight neck with a smooth integument surface. The antennae are composed of eleven segments, in which the tip segment is 2.5 times the length of the next segment. The eyes are rounded and bulbous in structure with a circumference of ten

ommatidia The compound eyes of arthropods like insects, crustaceans and millipedes are composed of units called ommatidia (singular: ommatidium). An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. The ...

. While the clypeus structure places ''A. electropilosum'' in the ''pilosum'' group, the combination of rounded frontal head capsule lobes, mandibles with eleven teeth, and the angle of clypeus border is not seen in any extant species.

References

{{Taxonbar, from=Q18209484 Myrmicinae Fossil ant taxa Burdigalian life Neogene Dominican Republic Miocene insects of North America Prehistoric insects of the Caribbean Fauna of Hispaniola Insects of the Dominican Republic Fossils of the Dominican Republic Dominican amber Fossil taxa described in 2007