Titanomyrma

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Titanomyrma
Temporal range: 48.6–46.2  Ma
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Titanomyrma gigantea SMFMEI00998.jpg
Dorsal view of T. gigantea holotype, specimen SMFMEI00998
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily:† Formiciinae
Genus:† Titanomyrma
Archibald et al., 2011
Species
  • Titanomyrma lubeiArchibald et al., 2011
  • Titanomyrma gigantea(Lutz, 1986)
  • Titanomyrma simillima(Lutz, 1986)

Titanomyrma is a genus of extinct giant ants which lived during the Eocene. The type species Titanomyrma gigantea and the smaller Titanomyrma simillima are known from the Eocene of Germany, while the third species Titanomyrma lubei, is known from Wyoming, United States. The presence of Titanomyrma in North America was considered to indicate "the first reported cross-Arctic dispersal by a thermophilic insect group". [1] . However a queen reported from Upland temperate shales in British Columbia raised questions on the exact thermophilic nature of the genus. The type species of this genus, T. gigantea, is the largest-known fossil or extant species of ant in the world.

Contents

Taxonomy

Dorsal view of the Titanomyrma simillima holotype, specimen "SMFMEI01006" Titanomyrma simillima SMFMEI01006 01.jpg
Dorsal view of the Titanomyrma simillima holotype, specimen "SMFMEI01006"

Archibald et al. in 2011 erected the genus Titanomyrma, described the species Titanomyrma lubei and proposed two new combinations, T. gigantea (formerly Formicium giganteum Lutz, 1986) and T. simillima (formerly Formicium simillimum Lutz, 1986). T. gigantea has been designated the type species for the genus. [2] [3]

The name of the genus is a derivative of the Greek Τιτάν (Titan), meaning 'one of prodigious size, strength, or achievement', [4] and alluding to the Titans of Greek mythology; and the Greek word μύρμηξ (myrmex) meaning 'ant'. [5]

The genus Titanomyrma is differentiated from others in the family by the shape of the gaster which is variable. In the three included species the gaster ranges from ovate to more slender or cylindrical. The A5 abdominal segment width relative to other gaster segments is variable and the relative lengths of A3–A7 are also variable. [2]

The queens of the three Titanomyrma can be distinguished from those of other genera most easily by gaster characters. The gasters are more slender in Titanomyrma. Amongst the three species of Titanomyrma, the ratio between length to width of the queens of the three species is as follows, T. lubei – 2.14, T. gigantea – 1.40, and T. simillima – 1.50. [2] The middle half of T. lubei is roughly cylindrical while for other Titanomyrma species, it is ovate with the segment A5 being the widest. The segment A3 has a length about a quarter of the width while for other species it is about a third. The segment A4 is thrice as long as the length of segment A3 while that of A4 segments of other species is less than twice. The segment A5–6 of T. lubei is approximately half as long as it is wide while for other species it is about a third. A3 is not curved around the petiole at the junction. [2]

T. gigantea is the largest giant ant ever found, larger than the biggest extant giant ants, which are the five-centimetre-long (2.0 in) driver ants of the genus Dorylus , found in Central and East Africa. [1] [6] The fossils indicate that the males grew up to 3 centimetres (1.2 in) and the queens grew to 7 centimetres (2.8 in). It had a wingspan of about 16 centimetres (6.3 in). [7] [8]

With the description of the genus Titanomyrma and the description T. lubei, two other species, Formicium giganteum and Formicium simillima, were reclassified into this genus, additional undescribed or unplaced specimens are also known.

T. gigantea

Titanomyrma gigantea queens and males are described from the Messel Formation, [9] near the village of Messel, in the state of Hessen, 30 km (19 mi) south of Frankfurt am Main in Germany.

T. simillima

Titanomyrma simillima, as with T. gigantea, are also only known from the Messel Formation, [9] and is slightly smaller in size then the coeval species.

T. lubei

The Titanomyrma lubei holotype was discovered by Louis Lube at DMNS locality 784, the Farson Fish Beds, in Sweetwater County, Wyoming, USA. The site works Early Eocene lake sediments of the Green River Formations Laney Member. [2] [6]

After discovery, Lube donated the fossil to the collections of the Denver Museum of Nature and Science where it was noticed by paleoentomologist Bruce Archibald and (then) museum chief curator Kirk R. Johnson while they were going through storage drawers. [1] The holotype is of a queen ant comparable in size to rufus hummingbirds, but no workers have been found. The specific epithet of the new species is formed from the surname of the collector of the holotype, Louis Lube. [2] , and was the first member of the genus known from North America.

Titianomyrma sp. Eocene Okanagan Highlands Titianomyrma sp BBM-PAL-2022-00001 Allenby Formation Fig1a.png
Titianomyrma sp.
Eocene Okanagan Highlands

Unidentified species

An undescribed species has been reported from the Eckfeld Maar of Germany. [7] Archibald, Mathewes, & Aase (2023) reported a Titanomyrma queen from the Allenby Formation, and noted the range extension for Formiciinae into the Eocene Okanagan Highlands, as the subfamily was previously considered a strictly thermophilic ant group. Due to complications arising from preservational distortion during diagenesis, they were unable to determine the correct size of the queen in life. If the distortion was lateral, then compression to bilateral symmetry yielded an adult length of approximately 3.3 cm (1.3 in), placing it the same range as Formicium berryi and F. brodiei , known only from wings, and suggested as possible males. Conversely stretching the fossil to bilateral symmetry results in a larger 5 cm (2.0 in) length estimate, placing it as comparable to queens of T. lubei and T. simillima. [8]

Paleoecological implications

Holotype of T. lubei with rufous hummingbird for scale Titanomyrma lubei 02.jpg
Holotype of T. lubei with rufous hummingbird for scale

The fossils of Titanomyrma gigantea, the first of the genus to be discovered, are very well preserved. They show that T. gigantea did not possess a sting and did not have a closing mechanism on the crop. It is surmised that it must have sprayed formic acid as a defence, and either ate fresh food, in the manner of leafcutter ants (which eat only the fungi they personally cultivate in their nests), or was carnivorous. Modern relatives include driver ants. Titanomyrma may have been a precursor species, possibly following a raiding lifestyle and butchering large animals. [9]

T. lubei is related to Formiciinae specimens previously found in Germany and in the Isle of Wight in southern England dating from the same period. It is the first complete Formiciinae fossil from North America; previous evidence that the subfamily lived in North America during the Eocene included an isolated wing from Tennessee. It is a further example, in the northern temperate regions, of tropical fauna and flora such as hippopotamus precursors, tropical plankton and pollen from tropical palms. T. lubei was suggested to support the hypothesis that during the Eocene ( 56 to 34 million years ago), conditions such as land bridges and hot spells existed which permitted the spread of ancient warmth-loving insects and other forms of life from Europe to North America or vice versa, which would not have occurred had the temperature been uniformly cool throughout. [1] [2] [6] However in 2023, a Titanomyrma queen was reported from the Eocene Okanagan Highlands, a noted upland subtropical to temperate mountain area. The presence of the genus in much cooler temperatures than previously known brought up question regarding how thermophilic the subfamily was. [8]

Related Research Articles

<span class="mw-page-title-main">Formiciinae</span> Extinct subfamily of ants

Formiciinae is an extinct subfamily of ants known from Eocene deposits in Europe and North America.

<span class="mw-page-title-main">Messel pit</span> UNESCO World Heritage Site near Messel, Germany

The Messel pit is a disused quarry near the village of Messel about 35 km (22 mi) southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of well-preserved fossils dating from the middle of the Eocene, it has significant geological and scientific importance. Over 1000 species of plants and animals have been found at the site. After almost becoming a landfill, strong local resistance eventually stopped these plans and the Messel pit was declared a UNESCO World Heritage Site on 9 December 1995. Significant scientific discoveries about the early evolution of mammals and birds are still being made at the Messel pit, and the site has increasingly become a tourist site as well.

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

Formicium is an extinct collective genus of giant ants in the Formicidae subfamily Formiciinae. The genus currently contains three species, Formicium berryi, Formicium brodiei, and Formicium mirabile. All three species were described from Eocene aged sediments.

<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.

T. giganteum may refer to:

<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>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">Allenby Formation</span>

The Allenby formation is a sedimentary rock formation in British Columbia which was deposited during the Ypresian stage of the Early Eocene. It consists of conglomerates, sandstones with interbedded shales and coal. The shales contain an abundance of insect, fish and plant fossils known from 1877 and onward, while the Princeton Chert was first indented in the 1950's and is known from anatomically preserved plants.

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

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. They also have long, thin legs and an elongated mesosoma (thorax) and petiole.

<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

Pachycondyla lutzi is an extinct species of ant in the formicid subfamily Ponerinae described by from fossils found in Europe. P. lutzi is one of six Lutetian Pachycondyla species.

<i>Pachycondyla? messeliana</i> Extinct species of ant

Pachycondyla? messeliana is an extinct species of ants in the formicid subfamily Ponerinae described by from a fossil found in Europe. P.? messeliana is one of six Lutetian Pachycondyla species.

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

Pachycondyla petiolosa is an extinct species of ant in the formicid subfamily Ponerinae described by from a fossil found in Europe. P. parvula is one of six Lutetian Pachycondyla species.

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

Cephalopone is an extinct genus of ants in the formicid subfamily Ponerinae described from fossils found in Europe. There are two described species placed into the genus, Cephalopone grandis and Cephalopone potens. Cephalopone is one several Lutetian Ponerinae genera.

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

Cyrtopone is an extinct genus of ants in the formicid subfamily Ponerinae described from fossils found in Europe. There are four described species placed into the genus, Cyrtopone curiosa, Cyrtopone elongata, Cyrtopone microcephala, and Cyrtopone striata. Cyrtopone is one several Lutetian Ponerinae genera.

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

Messelepone is an extinct genus of ants in the formicid subfamily Ponerinae described from fossils found in Europe. M. leptogenoides is the only species assigned to the genus, which is one of several Lutetian Ponerinae genera.

<i>Paraneuretus</i> Genus of ants

Paraneuretus is an extinct genus of formicid in the ant subfamily Aneuretinae known from fossils found in Asia and Europe. The genus contains three middle to late Eocene age species, Paraneuretus dubovikoffi, Paraneuretus longicornis, and Paraneuretus tornquisti.

Aneuretellus is an extinct genus of ant in the formicid subfamily Aneuretinae, and is one of eight genera of the subfamily. The genus contains a single described species Aneuretellus deformis and is known from one Middle Eocene fossil which was found in Sakhalin in the Russian Far East.

The paleofauna of the Eocene Okanagan Highlands is comprised of Early Eocene arthropods, vertebrates, plus rare nematodes and molluscs found in geological formations of the northwestern North American Eocene Okanagan Highlands. The highlands lake bed series' as a whole are considered one of the great Canadian Lagerstätten. The paleofauna represents that of a late Ypresian upland temperate ecosystem immediately after the Paleocene-Eocene thermal maximum, and before the increased cooling of the middle and late Eocene to Oligocene. The fossiliferous deposits of the region were noted as early as 1873, with small amounts of systematic work happening in the 1880-90s on British Columbian sites, and 1920-30s for Washington sites. Focus and more detailed descriptive work on the Okanagan Highlands site started in the last 1970's. Most of the highlands sites are preserved as compression-impression fossils in "shales", but also includes a rare permineralized biota and an amber biota.

References

  1. 1 2 3 4 Susan Milius (May 4, 2011). "Giant ants once roamed Wyoming". Science News . Retrieved May 6, 2011.
  2. 1 2 3 4 5 6 7 S. Bruce Archibald; Kirk R. Johnson; Rolf W. Mathewes & David R. Greenwood (2011). "Intercontinental dispersal of giant thermophilic ants across the Arctic during early Eocene hyperthermals" (PDF). Proceedings of the Royal Society B . 278 (1725): 3679–3686. doi:10.1098/rspb.2011.0729. PMC   3203508 . PMID   21543354.
  3. ↑ "†Titanomyrma Archibald et al. 2011 (ant)". Paleobiology Database. Paleodb.org. Retrieved 10 May 2011.
  4. ↑ Titan. (n.d.) The American Heritage Dictionary of the English Language, Fourth Edition. (2003). Retrieved May 9, 2011 from The Free Dictionary.
  5. ↑ "Myrmex". Greek Myth Index. www.mythindex.com. 2007. Retrieved 10 May 2011.
  6. 1 2 3 Richard Black (3 May 2011). "Giant ants spread in warm climes". BBC News . Retrieved 10 May 2011.
  7. 1 2 Stephan Schaal (27 Jan 2006). "Messel". eLS. doi:10.1038/npg.els.0004143.
  8. 1 2 3 Archibald, S.; Mathewes, R.; Aase, A. (2023). "Eocene giant ants, Arctic intercontinental dispersal, and hyperthermals revisited: discovery of fossil Titanomyrma (Hymenoptera: Formicidae: Formiciinae) in the cool uplands of British Columbia, Canada". The Canadian Entomologist. 155 (e6).
  9. 1 2 3 "Giant ant Formicium giganteum". Wildfacts (Science and Nature:Animals) of BBC Home. bbc.co.uk. July 2008. Archived from the original on 1 February 2003. Retrieved 17 May 2011.
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