''Azteca alpha'' is an extinct

species In biology, a species is the basic unit of Taxonomy (biology), 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 ...

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 22,0 ...

in the subfamily

Dolichoderinae Dolichoderinae is a subfamily of ants, which includes species such as the Argentine ant (''Linepithema humile''), the erratic ant, the odorous house ant, and the cone ant. The subfamily presents a great diversity of species throughout the w ...

known from possibly

Miocene The Miocene ( ) is the first 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 means "less recent" ...

fossils found on

Hispaniola Hispaniola (, also ; es, La Española; Latin and french: Hispaniola; ht, Ispayola; tnq, Ayiti or Quisqueya) is an island in the Caribbean that is part of the Greater Antilles. Hispaniola is the most populous island in the West Indies, and t ...

. ''A. alpha'' is one of only two species in the genus '' Azteca'' to have been described from fossils, both 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 incl ...

. It is the host for a fossil nematode, and has been preserved with

scale insects Scale insects are small insects of the order Hemiptera, suborder Sternorrhyncha. Of dramatically variable appearance and extreme sexual dimorphism, they comprise the infraorder Coccomorpha which is considered a more convenient grouping than th ...

History and classification

left, up''A. alpha'' dorsal view When described ''Azteca alpha'' was known from approximately 560 fossil insects which are solitary or group inclusions in transparent chunks of

. The amber was produced by the extinct ''

Hymenaea protera ''Hymenaea protera'' is an extinct prehistoric leguminous tree, the probable ancestor of present-day ''Hymenaea'' species. Most neotropical ambers come from its fossilized resin, including the famous Dominican amber. ''H. protera'' once grew in ...

'', which formerly grew on

, across northern South America and up to southern Mexico. The specimens were collected from a number of amber mines 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 war ...

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 The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', " ...

, 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. At the time of description, 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 seve ...

worker in addition to the

paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype nor a syntype). O ...

worker, male and queen specimens, were preserved in the

Museum of Comparative Zoology A museum ( ; plural museums or, rarely, musea) is a building or institution that cares for and displays a collection of artifacts and other objects of artistic, cultural, historical, or scientific importance. Many public museums make thes ...

amber collections. The fossils were first studied by entomologist

Edward O. Wilson Edward Osborne Wilson (June 10, 1929 – December 26, 2021) was an American biologist, naturalist, entomologist and writer. According to David Attenborough, Wilson was the world's leading expert in his specialty of myrmecology, the study of ...

of the

Harvard University Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of high ...

, who published his

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 ...

of the new species in the journal ''

Psyche Psyche (''Psyché'' in French) is the Greek term for "soul" (ψυχή). Psyche may also refer to: Psychology * Psyche (psychology), the totality of the human mind, conscious and unconscious * ''Psyche'', an 1846 book about the unconscious by Car ...

'' in 1985. 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 ...

''alpha'', derived from 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 ...

''alpha'', was chosen both as a reference to the early geological occurrence of the species for the genus ''Azteca'' and in allusion to the sheer volume of ''A. alpha'' fossil inclusions in the Dominican amber. George Poinar Jr. noted that ''Azteca alpha'' fossils comprise up to 50% of the formicids in Dominican amber, and Wilson estimated that ''A. alpha'' represented 50% or more of them. Portions of nests have also been fossilized and identified. They show an association of ''A. alpha'' colonies and the extinct nematode '' Formicodiplogaster myrmenema''. The nests show active ant colonies in which adult and juvenile ''F. myrmenema'' are present. Individual examples of

phoretic Phoresis or phoresy is a non-permanent, commensalistic interaction in which one organism (a phoront or phoretic) attaches itself to another (the host) solely for the purpose of travel. Phoresis has been observed directly in ticks and mites s ...

''F myrmenema'' are preserved in a

dauer stage Dauer (German "''die Dauer''", English "the enduring", "the duration" in the meaning of "a length of time",) describes an alternative developmental stage of nematode worms, particularly rhabditids including ''Caenorhabditis elegans'', whereby the ...

that was possibly carried in the ants' abdominal intersegment membranes. The transition and transport of the dauer stage ''F myrmenema'' may have been a result of deteriorating conditions in the host colony. No direct evidence has been found for ''F. myrmenema'' living in the postpharyngeal glands or head glands of ''A. alpha''. Another amber specimen with 23 pseudococcid

, twenty female and nymphs and three males, associated closely with nine ''A. alpha'' workers has been described. While the pseudococcids likely were not full

trophobiont Trophobiosis is a symbiotic association between organisms where food is obtained or provided. The provider of food in the association is referred to as a trophobiont. The name is derived from the Ancient Greek τροφή (''trophē''), meaning " ...

s, as indicated by wax extrusions from between the dorsal abdominal segments, the association indicates they were tended by the ants. The specimens in amber were possibly entombed while transporting the pseudococcids, an early representation in amber of ants tending scale insects.

Description

''Azteca alpha'' has a suite of traits that match modern species in the ''alfari'' group. ''A. alpha'' is separated from the other species in the group by the outline of the

propodeum The propodeum or propodium is the first abdominal segment in Apocrita Hymenoptera ( wasps, bees and ants). It is fused with the thorax to form the mesosoma. It is a single large sclerite, not subdivided, and bears a pair of spiracles. It is ...

, the length of the antennae scape and in the density of the hairs covering the body. The males of ''A. alpha'' are nearly identical to males of the modern species '' A. fiebrigi''. The queens are similar to ''A. fiebrigi'' but can be separated by the thinner outline of the petiole than is seen in ''A. fiebrigi''. The second Dominican amber species, '' Azteca eumeces'' is separated from ''A. alpha'' by the notably elongated head capsule of the workers.

References

{{Taxonbar, from=Q14438604 †alpha 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 1985 Taxa named by E. O. Wilson