''Aphaenogaster praerelicta'' 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 solitary

Late Oligocene The Chattian is, in the geologic timescale, the younger of two ages or upper of two stages of the Oligocene Epoch/ Series. It spans the time between . The Chattian is preceded by the Rupelian and is followed by the Aquitanian (the lowest stage ...

Early Miocene The Early Miocene (also known as Lower Miocene) is a sub-epoch of the Miocene epoch (geology), Epoch made up of two faunal stage, stages: the Aquitanian age, Aquitanian and Burdigalian stages. The sub-epoch lasted from 23.03 ± 0.05 annum, Ma to ...

fossil found in

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

. At the time of description ''A. praerelicta'' was one of three ''Aphaenogaster'' species known from Mexico.

History and classification

''Aphaenogaster praerelicta'' 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

Mexican amber Mexican amber, also known as Chiapas Amber is amber found in Mexico, created during the Early Miocene and middle Miocene epochs of the Cenozoic Era in southwestern North America. As with other ambers, a wide variety of taxa have been found as inc ...

along with three

flies 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 m ...

, two

springtail Springtails (Collembola) form the largest of the three lineages of modern hexapods that are no longer considered insects (the other two are the Protura and Diplura). Although the three orders are sometimes grouped together in a class called Ento ...

s, a

wasp A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. ...

, and some pollen grains. Mexican amber is recovered from fossil bearing rocks in the

Simojovel Simojovel is one of the 119 municipalities of Chiapas, in southern Mexico. As of 2010, the municipality had a total population of 40,297, up from 31,615 as of 2005. It covers an area of 446.99 km2. The municipality had 145 localities, the ...

region of Chiapas, Mexico. The amber dates from between 22.5 million years old, representing the youngest sediments of the Balumtun Sandstone, and the 26 million year old

La Quinta Formation The La Quinta Formation is a Jurassic geologic formation which crops out in the Cordillera de Mérida and Serranía del Perijá of western Venezuela and northeastern Colombia. The formation is also present in the subsurface of the Cesar-Rancher ...

. This age range straddles the boundary between the

and

and is complicated by both formations being secondary deposits for the amber: the age range represents only the youngest that it might be. The amber was produced by either of two extinct ''

Hymenaea ''Hymenaea'' is a genus of plants in the legume family Fabaceae. Of the fourteen living species in the genus, all but one are native to the tropics of the Americas, with one additional species (''Hymenaea verrucosa'') on the east coast of Afr ...

'' species, '' Hymenaea mexicana'' or '' Hymenaea allendis'', both of which were initially described from fossil flowers included in Mexican amber. The fossil is part of the amber collection of George Poinar Jr., which at the time of description, was housed at the

University of California, Berkeley The University of California, Berkeley (UC Berkeley, Berkeley, Cal, or California) is a public land-grant research university in Berkeley, California. Established in 1868 as the University of California, it is the state's first land-grant u ...

. The fossil ant was first studied by paleoentomologist Maria De Andrade of the

University of Basel The University of Basel (Latin: ''Universitas Basiliensis'', German: ''Universität Basel'') is a university in Basel, Switzerland. Founded on 4 April 1460, it is Switzerland's oldest university and among the world's oldest surviving universit ...

. De Andrade's 1995

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 German journal ''Stuttgarter Beiträge zur Naturkunde. Serie B (Geologie und Paläontologie)''. The specific epithet ''praerelicta'' 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 ...

"prae" meaning ''before'' and "relicta", the species name for the modern '' Aphaenogaster relicta'' of Haiti, to which ''A. praerelicta'' is most similar. ''A. praerelicta'' is one of two species described by De Andrade in the 1995 paper: the other species ''

Aphaenogaster amphioceanica ''Aphaenogaster amphioceanica'' is an extinct species of ant in the subfamily Myrmicinae known from a single possibly Miocene fossil found in amber on Hispaniola. At the time of description ''A. amphioceanica'' was one of two ''Aphaenogaster'' sp ...

'' was 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 ...

. Three l species of ''Aphaenogaster'' are currently known from Mexico, the fossil ''A. praerelicta'', '' A. ensifera'' and '' A. mexicana''.

Description

The ''Aphaenogaster praerelicta'' specimen is a well-preserved worker caste adult with an estimated body length of approximately . The overall coloration of ''A. praerelicta'' is a brown tone, with the legs and posterior borders of the

tergites A ''tergum'' (Latin for "the back"; plural ''terga'', associated adjective tergal) is the dorsal ('upper') portion of an arthropod segment other than the head. The anterior edge is called the 'base' and posterior edge is called the 'apex' or 'mar ...

shading slightly lighter. The body has numerous long thick hairs which range from fully erect to lying down against the exoskeleton. The head widens towards the posterior edge and lacks the "neck" which is seen in ''A. amphioceanica''. While the hollows where the antennae were attached to the head capsule are small, the antennae of ''A. praerelicta'' are unknown, as they were lost before the specimen was entombed. The head capsule has numerous deep anatomizing ridges over which a strong reticulation is superimposed. The propodeum is notable in having two spines long that point upwards and backwards and another set of spines at the humeral angle closer to the head. The combination of no "neck", short humeral spines and long posterior spines on the propodeum are unique. The character combination is similar to that of several modern North American species and ''A. relicta'' of Hati.

References

{{Taxonbar, from=Q15733597 praerelicta Miocene insects Fossil ant taxa Fossils of Mexico Fossil taxa described in 1995 Mexican amber Prehistoric insects of North America