Archimyrmex

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Archimyrmex
Temporal range: Middle Eocene
Archimyrmex wedmannae Smfmei2016 01.jpg
A. wedmannae holotype
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Myrmeciinae
Genus:† Archimyrmex
Cockerell, 1923
Species
  • A. rostratusCockerell, 1923
  • A. piatnitzkyi(Viana & Haedo Rossi, 1957)
  • A. smekali(Rossi de Garcia, 1981)
  • A. wedmannaeDlussky, 2012
Synonyms
  • AmeghinoiaViana & Haedo Rossi, 1957
  • PolanskiellaRossi de Garcia, 1983

Archimyrmex is an extinct genus of ant in the formicid subfamily Myrmeciinae, described by palaeoentomologist Theodore Cockerell in 1923. The genus contains four described species, Archimyrmex rostratus, Archimyrmex piatnitzkyi, Archimyrmex smekali and Archimyrmex wedmannae. Archimyrmex is known from a group of Middle Eocene fossils which were found in North America, South America, and Europe. The genus was initially placed in the subfamily Ponerinae, but it was later placed in Myrmeciinae; it is now believed to be the ancestor of the extant primitive genus Myrmecia from Australia. Despite this, Archimyrmex is not a member to any tribe and is regarded as incertae sedis within Myrmeciinae. However, some authors believe Archimyrmex should be assigned as incertae sedis within Formicidae. These ants can be characterised by their large mandibles and body length, ranging from 13.2 to 30 mm (0.52 to 1.18 in). They also have long, thin legs and an elongated mesosoma (thorax) and petiole.

Contents

History and classification

When described the genus Archimyrmex was known from a solitary fossil preserved as an impression in fine shale of the Green River formation in Colorado. The fossil was recovered in July 1922 from the "station 1" fossil site near the top of the Ute trail by entomologist Wilmatte Porter Cockerell. [1] One side of the A. rostratus holotype is currently deposited in the University of Colorado paleontology collections while the counterpart is in the US National Museum, and an additional eleven fossils were known as of 2002. [2] The holotype was first studied by palaeoentomologist Theodore Dru Alison Cockerell of the University of Colorado and his 1923 type description of the new genus and species was published in The Entomologist. [3] The specific epithet "rostratus" is a reference to the beak-like outline of the mandibles seen in the type specimen. [1]

Cockerell placed the genus into the subfamily Ponerinae. He noted similarities between Archimyrmex and Myrmecia and Prionomyrmex , suggesting Archimyrmex to be an intermediate between the two other genera. The genus was re-described in 1928 by palaeoentomologist William Wheeler who moved the genus from Ponerinae to Myrmicinae. This placement was not challenged until a 2003 paper by Russian palaeoentomologists G.M. Dlussky and K.S. Perfilieva, who moved the genus again, this time to the primitive Subfamily Myrmeciinae based on the close similarity between Archimyrmex and Prionomyrmex. [2] [4] [5] In 1957, an additional species of fossil ant was described from the Middle Eocene Ventana Formation in the Rio Pichileufu region of Argentina by M.J. Viana and J.A. Haedo Rossi. They placed the species into a new genus, Ameghinoia as Ameghinoia" piatnitzkyi. As with Archimyrmex, the genus was first placed in Ponerinae. It was subsequently moved to Myrmeciinae by R.R. Snelling in 1981. A second Ventana Formation ant species was described in 1981 by E. Rossi de Garcia and placed into another new genus Polanskiella as P. smekali. Recovered from an outcrop of the Ventana Formation in the Rio Limay area, Rossi de Garcia distinguished the new species from "A." piatnitzkyi based on characteristics of the wing venation and because of the difference in size of the two type specimens. A series of fossils from the three genera were examined by Dlussky and Perfilieva and based on the very notable similarities between the three species, they synonymized the three genera under Archimyrmex, treating both Ameghinoia and "Polanskiella" as junior synonyms. A fourth species, A. wedmannae was described by Dlussky in 2012 based on fossils found in the Middle Eocene Messel Pit site of Germany. The specific epithet was chosen by Dlussky to honour paleoentomologist Sonja Wedmann. [4]

Before Archimyrmex was placed into the subfamily Myrmeciinae, Wheeler classified the genus as incertae sedis (Latin for "of uncertain placement") within the ant subfamily Myrmicinae, as it could not be confidently placed into any ant tribe. [6] Even after its placement within Myrmeciinae it was still classified as incertae sedis. However, Cesare Baroni Urbani of the University of Basel, Switzerland classified the genus as incertae sedis within the family Formicidae. [7] Baroni Urbani justifies his decision by stating the characters of the ant are similar to those of Cariridris , an insect from the Lower Cretaceous that was once placed in Myrmeciinae, but is now incertae sedis within the subclade Aculeata. [8] [9] Archimyrmex also shares a similar structure to other ants and insects within the order Hymenoptera. The key diagnostic traits (synapomorphies) of Myrmeciinae ants cannot be observed although the described species have elongated scapes (the first segment of the antenna), a key diagnostic trait for Formicidae. [7] A 2012 report describing new myrmecine fossils accepted the classification of Archibald and colleagues while disregarding Baroni Urbani's comments. [4]

The following cladogram generated by Archibald and colleagues show the possible phylogenetic position of Archimyrmex among some ants of the subfamily Myrmeciinae; it is possible that Archimyrmex may be the ancestor of Myrmecia. [5] [10]

Myrmeciinae

Archimyrmex

Myrmecia

Prionomyrmex janzeni

Prionomyrmex longiceps

Macabeemyrma

Avitomyrmex

Ypresiomyrma

Nothomyrmecia

Description

In general Archimyrmex individuals have a head capsule that bears a set of enlarged mandibles with either a rectangular or triangular outline. The mandibles have a mixed arrangement of teeth and denticles (smaller teeth) on the inside margin. The gynes have long legs and long mesosomas, an elongated petiole (a narrow waist between the mesosoma and gaster) which is usually smooth in profile on the upper surface. The petiole structure in combination with little to no constriction between abdominal segments III and IV is unique to the genus and separates it from the other Myrmeciinae genera. [4] [5]

A. piatnitzkyi

A. piatnitzkyi holotype Archimyrmex piatnitzkyi NHMW1976-1783-6 profile.jpg
A. piatnitzkyi holotype

A. piatnitzkyi is reported from three specimens, giving a body length between 16–18 mm (0.63–0.71 in). [5] The holotype, recovered from the Ventana Formation of the Neuquén Basin in Argentina is currently preserved at the Bernardino Rivadavia Natural Sciences Museum palaeoentomological collection. The head capsule is slightly ovoid, being a little longer than it is wide and having elongated mandibles that are notably shorter than the head. As with A. smekali, the mesosoma is massive, being between 1.7-1.8 times as long as it is tall. The legs are like those of the other species, being long and thin. Unlike the other species, the petiole of A. piatnitzkyi does not have a constricted post-petiole. [5]

A. rostratus

A. rostratus holotype Archimyrmex rostratus UCM15174 profile.jpg
A. rostratus holotype

The type specimen numbers are UC no. 15174 and USNM no. 69617 for the part and counterpart; females of the type species A. rostratus have a body length estimated to be between 13.2–15.8 mm (0.52–0.62 in), with a small gaster that is shorter than the mesosoma and sporting a short thick sting. [5] The length of the head when excluding the mandibles is 4 mm (0.16 in), the mesosoma is 5.3 mm (0.21 in) and the middle femur is around 3.7 mm (0.15 in). The preserved specimens from the Green River Formation are brown and the upper area of the head and gaster is black, which is similar to Myrmecia nigriceps . [1] The head capsules have antennae borne on a scape which is long and passes the edge of the occipital margin of the head. The short, thickened mandibles have several larger teeth interspersed with small denticles, [5] and are about 50% of the length of the head capsule. [4] The scape is believed to be long and thin, and its mesosoma is narrow and long. The width of the scutum is greater than its length, the legs are noticeably elongated and thin, and the podeum (a narrow stalk that connects the mesosoma with the abdomen) is slightly convex. [5]

A. smekali

The A. smekali was recovered from the Ventana Formation in Argentina. The lectotype, numbered NMW. no. 1972/1574/9, is housed in the Museum of Natural History. [5] The lectotype female has an estimated body length of 3 cm (1.2 in) with an mesosoma that is described as "relatively massive" (being only 1.7 to 1.9 times as long as tall) and an oval shaped gaster. There is a notable constriction in the post-petiole abdominal segment not seen in the other species. The head capsule has mandibles which are about 70% as long as the head capsule, [4] and have four to five large teeth each. The antennal scape is longer than the occipital margin and the antenna is composed of an estimated twelve segments. [5] The legs are elongated and narrow, the propodeum is weakly convex and the petiole does not have a node (a segment between the mesosoma and gaster). A. smekali can be distinguished from other species by its massive size, the constriction in the post-petiole and the absence of the node. It was previously thought the ant had an eight-segmented antennae, but the lectotype has seven segments; Dlussky also mentions that the original description provided by Elsa Rossi de Garcia does not match the description he provided. [5] [11]

A. wedmannae

A. wedmannae from Germany is described from a single gyne that is approximately 23 mm (0.91 in), found in the Messel Formation. The fossil is believed to be 47 million years old. [4] The mesosoma measures 7.4 mm (0.29 in), the length of the head is 2.8 mm (0.11 in), the scape is 3.4 mm (0.13 in), the diameter of the eyes are 1.2 mm (0.047 in) and the forewings are 10.6 mm (0.42 in). The species has a head which is shorter than it is wide, but has mandibles about as long as the head which are triangular in outline. The eyes are oval shaped. As with the three other species the antennal scape is long, one-third of the scape length protrudes past the occipital margin of the head. [4] The pronotum in profile is either straight or weakly concave, and the petiole is weakly rounded with no node present. The propodeum has small denticles and is weakly convex, and the legs are long. The gaster has a well developed and long sting. This species can be distinguished from other Archimyrmex ants by its long mandibles; the shape of the petiole is almost the same as A. smekali, but their mandibles are much shorter and the mesosoma is more compact. The propodeum's dorsal surface is also more convex. [4]

Related Research Articles

<span class="mw-page-title-main">Myrmeciinae</span> Subfamily of ants

Myrmeciinae is a subfamily of the Formicidae, ants once found worldwide but now restricted to Australia and New Caledonia. This subfamily is one of several ant subfamilies which possess gamergates, female worker ants which are able to mate and reproduce, thus sustaining the colony after the loss of the queen. The Myrmeciinae subfamily was formerly composed of only one genus, Myrmecia, but the subfamily was redescribed by Ward & Brady in 2003 to include two tribes and four genera: An additional three genera, one form genus, and 9 species were described in 2006 from the Early Eocene of Denmark, Canada, and Washington. Subsequently an additional fossil genus was moved from the family Rhopalosomatidae in 2018, and a new genus was described in 2021.

<i>Sphecomyrma</i> Extinct genus of ants

Sphecomyrma is an extinct genus of ants which existed in the Cretaceous approximately 79 to 92 million years ago. The first specimens were collected in 1966, found embedded in amber which had been exposed in the cliffs of Cliffwood, New Jersey, by Edmund Frey and his wife. In 1967, zoologists E. O. Wilson, Frank Carpenter and William L. Brown, Jr. published a paper describing and naming Sphecomyrma freyi. They described an ant with a mosaic of features—a mix of characteristics from modern ants and aculeate wasps. It possessed a metapleural gland, a feature unique to ants. Furthermore, it was wingless and had a petiole which was ant-like in form. The mandibles were short and wasp-like with only two teeth, the gaster was constricted, and the middle and hind legs had double tibial spurs. The antennae were, in form, midway between the wasps and ants, having a short first segment but a long flexible funiculus. Two additional species, S. canadensis and S. mesaki, were described in 1985 and 2005, respectively.

<i>Prionomyrmex</i> Extinct genus of ants

Prionomyrmex is an extinct genus of bulldog ants in the subfamily Myrmeciinae of the family Formicidae. It was first described by Gustav Mayr in 1868, after he collected a holotype worker of P. longiceps in Baltic amber. Three species are currently described, characterised by their long mandibles, slender bodies and large size. These ants are known from the Eocene and Late Oligocene, with fossil specimens only found around Europe. It is suggested that these ants preferred to live in jungles, with one species assumed to be an arboreal nesting species. These ants had a powerful stinger that was used to subdue prey. In 2000, it was suggested by Cesare Baroni Urbani that the living species Nothomyrmecia macrops and a species he described both belonged to Prionomyrmex, but this proposal has not been widely accepted by the entomological community. Instead, scientists still classify the two genera distinctive from each other, making Nothomyrmecia a valid genus.

<i>Ypresiomyrma</i> Extinct genus of ants

Ypresiomyrma is an extinct genus of ants in the subfamily Myrmeciinae that was described in 2006. There are four species described; one species is from the Isle of Fur in Denmark, two are from the McAbee Fossil Beds in British Columbia, Canada, and the fourth from the Bol’shaya Svetlovodnaya fossil site in Russia. The queens of this genus are large, the mandibles are elongated and the eyes are well developed; a stinger is also present. The behaviour of these ants would have been similar to that of extant Myrmeciinae ants, such as solitary foraging for arthropod prey and never leaving pheromone trails. The alates were poor flyers due to their size, and birds and animals most likely preyed on these ants. Ypresiomyrma is not assigned to any tribe, and is instead generally regarded as incertae sedis within Myrmeciinae. However, some authors believe Ypresiomyrma should be assigned as incertae sedis within Formicidae.

Avitomyrmex is an extinct genus of bulldog ants in the subfamily Myrmeciinae which contains three described species. The genus was described in 2006 from Ypresian stage deposits of British Columbia, Canada. Almost all the specimens collected are queens, with an exception of a single fossilised worker. These ants are large, and the eyes are also large and well developed; a sting is present in one species. The behaviour of these ants may have been similar to extant Myrmeciinae ants, such as foraging solitarily for arthropod prey and never leaving pheromone trails to food sources. Avitomyrmex has not been assigned to any tribe, instead generally being regarded as incertae sedis within Myrmeciinae. However, its identity as an ant has been challenged, although it is undoubtedly a hymenopteran insect.

<i>Macabeemyrma</i> Extinct genus of ants

Macabeemyrma is an extinct genus of bulldog ants in the subfamily Myrmeciinae containing the single species Macabeemyrma ovata, described in 2006 from Ypresian stage deposits of British Columbia, Canada. Only a single specimen is known; a holotype queen found preserved as a compression fossil. The specimen had no wings and small portions of its legs and eyes were faintly preserved. It was a large ant, reaching 25 millimetres (0.98 in) in length. This ants' behaviour would have been similar to that of extant Myrmeciinae ants, such as foraging singly in search for arthropod prey and nesting in soil or in trees. Macabeemyrma shows similarities to extinct ants in the genus Ypresiomyrma, and to the living Nothomyrmecia macrops, but has not been conclusively assigned to any tribe, instead generally regarded as incertae sedis within Myrmeciinae. However, the sole specimen lacks definitive traits, and its classification in Myrmeciinae, and even its identity as an ant, has been challenged.

<i>Myrmeciites</i> Extinct genus of ants

Myrmeciites is an extinct form genus of bulldog ants in the subfamily Myrmeciinae of the family Formicidae, which contains three described species and two fossils not placed beyond the genus level. Described in 2006 from Ypresian stage deposits, all three of the described species and one unplaced fossil are from British Columbia, Canada, while the second unplaced fossil is from Washington State, USA. These ants were large, with the largest specimens collected reaching 3 centimetres (1.2 in). The behaviour of these ants would have been similar to extant Myrmeciinae ants, such as solitary foraging, nesting either in the soil or trees, and leaving no pheromone trail to food sources. Due to the poor preservation of these ants, their phylogenetic position among Myrmeciinae is unclear, and no type species has been designated. These ants are classified as incertae sedis in Myrmeciinae, but some writers have classified it as incertae sedis within the insect order Hymenoptera. This reclassification, however, has not been accepted; instead, Myrmeciites remains in Myrmeciinae.

<span class="mw-page-title-main">Prionomyrmecini</span> Tribe of ants

Prionomyrmecini is an ant tribe belonging to the subfamily Myrmeciinae established by William Morton Wheeler in 1915. Two members are a part of this tribe, the extant Nothomyrmecia and the extinct Prionomyrmex. The tribe was once considered a subfamily due to the similarities between Nothomyrmecia and Prionomyrmex, but such reclassification was not widely accepted by the scientific community. These ants can be identified by their long slender bodies, powerful stingers and elongated mandibles. Fossil Prionomyrmecini ants were once found throughout Europe, possibly nesting in trees and preferring jungle habitats. Today, Prionomyrmecini is only found in Australia, preferring old-growth mallee woodland surrounded by Eucalyptus trees. Nothomyrmecia workers feed on nectar and arthropods, using their compound eyes for prey and navigational purposes. Owing to their primitive nature, they do not recruit others to food sources or create pheromone trails. Nothomyrmecia colonies are small, consisting of 50 to 100 individuals.

<i>Emplastus</i> Genus of ants

Emplastus is an extinct morphogenus of ants in the subfamily Dolichoderinae, known from fossils found in Asia and Europe. The genus contains twelve species described from sites in England, Eastern Europe and Far Eastern Russia.

<i>Casaleia</i> Genus of ants

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<i>Pseudectatomma</i> Genus of ants

Pseudectatomma is an extinct genus of ants in the formicid subfamily Ectatomminae described by from fossils found in Europe. The genus contains two species dating from the Eocene, Pseudectatomma eocenica and Pseudectatomma striatula.

<i>Pachycondyla lutzi</i> Extinct species of ant

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<i>Myanmyrma</i> Extinct genus of ants

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<i>Protopone</i> Extinct genus of ants

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<i>Pachycondyla succinea</i> Extinct species of ant

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Klondikia is an extinct hymenopteran genus in the ant family Formicidae with a single described species Klondikia whiteae. The species is solely known from the Early Eocene sediments exposed in northeast Washington state, United States. The genus is currently not placed into any ant subfamily, being treated as incertae sedis.

References

  1. 1 2 3 Cockerell, T.D.A. (1923). "The earliest known ponerine ant". The Entomologist. 56: 51–52. doi:10.5281/zenodo.26638.
  2. 1 2 Dlussky, G.M.; Rasnitsyn, A.P. (2002). "Ants (Hymenoptera: Formicidae) of Formation Green River and some other Middle Eocene deposits of North America". Russian Entomological Journal. 11 (4): 411–436.
  3. ↑ Carpenter, F. M. (1930). "The fossil ants of North America" (PDF). Bulletin of the Museum of Comparative Zoology. 70: 1–66.
  4. 1 2 3 4 5 6 7 8 9 Dlussky, G.M. (2012). "New Fossil Ants of the Subfamily Myrmeciinae (Hymenoptera, Formicidae) from Germany". Paleontological Journal. 46 (3): 288–292. doi:10.1134/s0031030111050054. S2CID   83891156.
  5. 1 2 3 4 5 6 7 8 9 10 11 Dlussky, G.M.; Perfilieva, K.S. (2003). "Paleogene ants of the genus Archimyrmex Cockerell, 1923 (Hymenoptera, Formicidae, Myrmeciinae)" (PDF). Paleontological Journal. 37 (1): 39–47.
  6. ↑ Wheeler, W.M. (1928). The Social Insects: Their Origin and Evolution. New York: Harcourt, Brace and Co. p. 117. OCLC   1533756.
  7. 1 2 Baroni Urbani, Cesare (2008). "Orthotaxonomy and parataxonomy of true and presumed bulldog ants (Hymenoptera, Formicidae)" (PDF). Doriana (Suppl. To Annali del Museo Civico di Storia Naturale Giacomo Doria). 8 (358): 1–10. ISSN   0417-9927.
  8. ↑ Ward, Philip S.; Brady, Seán G. (2003). "Phylogeny and biogeography of the ant subfamily Myrmeciinae (Hymenoptera : Formicidae)" (PDF). Invertebrate Systematics. 17 (3): 361–386. doi:10.1071/IS02046.
  9. ↑ Grimaldi, D.; Agosti, D.; Carpenter, J. M. (1997). "New and rediscovered primitive ants (Hymenoptera, Formicidae) in Cretaceous amber from New Jersey, and their phylogenetic relationships". American Museum Novitates (3208): 1–43.
  10. ↑ Archibald, S.B.; Cover, S. P.; Moreau, C. S. (2006). "Bulldog Ants of the Eocene Okanagan Highlands and History of the Subfamily (Hymenoptera: Formicidae: Myrmeciinae)" (PDF). Annals of the Entomological Society of America. 99 (3): 487–523. doi:10.1603/0013-8746(2006)99[487:BAOTEO]2.0.CO;2. S2CID   4845957.
  11. ↑ Rossi de Garcia, E. (1983). "Insectos fósiles en la Formación Ventana (Eoceno). Provincia de Neuquén". Revista de la Asociación Geológica Argentina. 38 (1): 17–23. ISSN   0004-4822.
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