''Aphaenogaster oligocenica'' 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 pair of

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'', "da ...

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s found in Europe. ''A. oligocenica'' is one of three species in the ant genus ''

Aphaenogaster ''Aphaenogaster'' is a genus of myrmicine ants. About 200 species have been described, including 18 fossil species. They occur worldwide except in South America south of Colombia, sub-Saharan Africa, and Antarctica. They are often confused w ...

'' to have been noted from fossils found in

Baltic amber The Baltic region is home to the largest known deposit of amber, called Baltic amber or succinite. It was produced sometime during the Eocene epoch, but exactly when is controversial. It has been estimated that these forests created more than ...

William Morton Wheeler William Morton Wheeler (March 19, 1865 – April 19, 1937) was an American entomologist, myrmecologist and Harvard professor. Biography Early life and education William Morton Wheeler was born on March 19, 1865, to parents Julius Morton Wheel ...

History and classification

When first examined, ''Aphaenogaster oligocenica'' was described from a single

type specimen In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes th ...

worker, with a second specimen being noted as probably belonging to the species, but too obscured by white mold growth in the fossil to be confirmed. Both of the specimen ants are fossilized as inclusions in transparent chunks of

. Baltic amber is approximately 46 million years old, having been deposited during the

Lutetian The Lutetian is, in the geologic timescale, a stage or age in the Eocene. It spans the time between . The Lutetian is preceded by the Ypresian and is followed by the Bartonian. Together with the Bartonian it is sometimes referred to as the ...

stage of the

. There is debate over the plant family which produced the amber, with evidence supporting relatives of either an '' Agathis'' or a ''

Pseudolarix ''Pseudolarix'' is a genus of coniferous trees in the pine family Pinaceae containing three species, the extant '' Pseudolarix amabilis'' and the extinct species '' Pseudolarix japonica'' and '' Pseudolarix wehrii''. ''Pseudolarix'' species are ...

''. When first described, the type worker was part of the

University of Königsberg The University of Königsberg (german: Albertus-Universität Königsberg) was the university of Königsberg in East Prussia. It was founded in 1544 as the world's second Protestant academy (after the University of Marburg) by Duke Albert of Pruss ...

amber collection as specimen number B5461, and the possible second fossil was specimen number B18570. The fossils were first studied by Wheeler, then a paleoentomologist with

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 placed the species in the genus ''Aphaenogaster''. Wheeler's 1915

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 journal ''Schriften der Physikalisch-Okonomischen Gesellschaft zu Konigsberg''. In his 1915 paper Wheeler noted that alongside ''A. oligocenica'', two other ''Aphaenogaster'' species are known from European amber fossils '' A. mersa'', and '' A. sommerfeldti''. A third northern European amber species, '' A. antiqua'', was described in 2009, and the authors of the 2009 paper noted a second confirmed ''A. oligocenica'' specimen which had been identified during their study. While both ''A. oligocenica'' and ''A. sommerfeldti'' are known from Baltic and

Bitterfeld amber The Baltic region is home to the largest known deposit of amber, called Baltic amber or succinite. It was produced sometime during the Eocene epoch, but exactly when is controversial. It has been estimated that these forests created more than ...

, ''A. mersa'' has only been found in Baltic amber and ''A. antiqua'' in

Rovno amber Rivne amber, occasionally called Ukrainian amber, is amber found in the Rivne Oblast and surrounding regions of Ukraine and Belarus. The amber is dated between Late Eocene and Early Miocene, and suggested to be contemporaneous to Baltic amber. ...

Description

The type worker of ''A. oligocenica'' has an approximate body length of , with a large gaster and long legs. Overall ''A. oligocenica'' can be distinguished from the related Baltic amber species ''A. sommerfeldti'' in several ways. ''A. sommerfeldti'' individuals have a more sloped and curved

mesonotum The mesothorax is the middle of the three segments of the thorax of hexapods, and bears the second pair of legs. Its principal sclerites (exoskeletal plates) are the mesonotum (dorsal), the mesosternum (ventral), and the mesopleuron (lateral) on ...

with the epinotum showing more tooth-like projections on the surface than seen in of ''A. oligocenica''. The head capsule of ''A. oligocenica'' has

rugose Rugose means "wrinkled". It may refer to: * Rugosa, an extinct order of coral, whose rugose shape earned it the name * Rugose, adjectival form of rugae Species with "rugose" in their names * ''Idiosoma nigrum'', more commonly, a black rugose trap ...

structuring which displays a reticulation on the rear of the capsule, transitioning to lengthwise striations from the region of the eyes forward. On the thorax and epinotum the striations are well pronounced and placed further apart than those on the head.

References

{{Taxonbar, from=Q14445646 Lutetian insects Fossil ant taxa Fossil taxa described in 1915 Prehistoric insects of Europe †Aphaenogaster oligocenica Baltic amber