Titanomyrma
Encyclopedia
Titanomyrma was a genus of giant ant
. The latest species to be discovered, T. lubei, was described in 2011, when a fossilized winged queen ant
, comparable in size to hummingbird
s, was found in Wyoming
. This fossil is the first body of a giant ant found in the Western Hemisphere. The presence of Titanomyrma in North America is considered to indicate "the first reported cross-Arctic dispersal by a thermophilic insect group". Another fossil species of this genus, T. giganteum, is the largest known fossil
or extant species of giant ant in the world.
locality 784, Farson Fish Beds, Laney Member of the Green River Formation
; Sweetwater County, Wyoming
, USA by Louis Lube, the collector and donor of the holotype
specimen.
The fossil formed part of the collection of Denver Museum of Nature and Science
and was discovered by Bruce Archibald and co-author and museum chief curator Kirk R. Johnson while casually going through storage drawers. The fossil depicts the queen ant only and no fossils of workers have been found. With the discovery of Titanomyrma lubei and the description of the genus, two other species of giant ants, Formicium giganteum and Formicium simillimum, were reclassified into this genus.
Beautifully preserved fossils of Titanomyrma giganteum and Titanomyrma simillimum were discovered in the Messel shales
, near the village of Messel
, in the state of Hesse
, 30 km south of Frankfurt am Main (Darmstadt Administrative District), in Germany
. A related undescribed species has been found in the nearby Eckfeld Maar.
s of Greek mythology; and the Greek word () meaning 'ant', gender feminine. The specific epithet of the new species is formed from the surname of the collector of the holotype, Louis Lube.
for the genus.
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.
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. giganteum – 1.40, and T. simillimum – 1.50. 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 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.
Titanomyrma giganteum is the largest giant ant ever found, larger than the biggest extant giant ants, which are the 5 centimetres (2 in) long driver ants of the Dorylus
genus, found in Central
and East Africa
. The fossils indicate that the males grew up to 3 centimetres (1.2 in) and the queens
grew to 6 centimetres (2.4 in). It had a wingspan of about 15 centimetres (5.9 in).
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 leaf-cutters, or was carnivorous
. Its modern relatives include driver ant
s and Titanomyrma may have been a precursor species, possibly following a raiding lifestyle and butchering large animals.
Titanomyrma lubei is related to fossil giant ants previously found in Germany
and in the Isle of Wight
in southern England
dating from the same period. It is the first complete giant ant fossil from North America
; previous evidence that big ants lived in North America during the Eocene
included an ancient ant 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. Titanomyrma lubei supports the idea that during the Eocene , conditions such as land bridge
s 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.
Ant
Ants are social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. More than...
. The latest species to be discovered, T. lubei, was described in 2011, when a fossilized winged queen ant
Queen ant
A queen ant is an adult, reproducing female ant in an ant colony; generally she will be the mother of all the other ants in that colony. Some female ants do not need to mate to produce offspring, reproducing through asexual parthenogenesis or cloning and all of those offspring will be female.Ant...
, comparable in size to hummingbird
Hummingbird
Hummingbirds are birds that comprise the family Trochilidae. They are among the smallest of birds, most species measuring in the 7.5–13 cm range. Indeed, the smallest extant bird species is a hummingbird, the 5-cm Bee Hummingbird. They can hover in mid-air by rapidly flapping their wings...
s, was found in Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
. This fossil is the first body of a giant ant found in the Western Hemisphere. The presence of Titanomyrma in North America is considered to indicate "the first reported cross-Arctic dispersal by a thermophilic insect group". Another fossil species of this genus, T. giganteum, is the largest known fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
or extant species of giant ant in the world.
Discovery
The fossil ant Titanomyrma lubei was discovered in ancient lake sediments in the DMNSDenver Museum of Nature and Science
The Denver Museum of Nature & Science is a municipal natural history and science museum in Denver, Colorado. It is a resource for informal science education in the Rocky Mountain region. A variety of exhibitions, programs, and activities help museum visitors learn about the natural history of...
locality 784, Farson Fish Beds, Laney Member of the Green River Formation
Green River Formation
The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes. The sediments are deposited in very fine layers, a dark layer during the growing season and a light-hue inorganic layer in winter. Each pair of layers is called a varve and...
; Sweetwater County, Wyoming
Wyoming
Wyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
, USA by Louis Lube, the collector and donor of the holotype
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen.
The fossil formed part of the collection of Denver Museum of Nature and Science
Denver Museum of Nature and Science
The Denver Museum of Nature & Science is a municipal natural history and science museum in Denver, Colorado. It is a resource for informal science education in the Rocky Mountain region. A variety of exhibitions, programs, and activities help museum visitors learn about the natural history of...
and was discovered by Bruce Archibald and co-author and museum chief curator Kirk R. Johnson while casually going through storage drawers. The fossil depicts the queen ant only and no fossils of workers have been found. With the discovery of Titanomyrma lubei and the description of the genus, two other species of giant ants, Formicium giganteum and Formicium simillimum, were reclassified into this genus.
Beautifully preserved fossils of Titanomyrma giganteum and Titanomyrma simillimum were discovered in the Messel shales
Messel pit
The Messel Pit is a disused quarry near the village of Messel, about southeast of Frankfurt am Main, Germany. Bituminous shale was mined there. Because of its abundance of fossils, it has significant geological and scientific importance...
, near the village of Messel
Messel
Messel is a municipality in the district of Darmstadt-Dieburg in Hesse near Frankfurt am Main in Germany.The village is first mentioned, as Masilla, in the Lorsch codex.Messel was the property of the lords of Groschlag from ca. 1400 to 1799...
, in the state of Hesse
Hesse
Hesse or Hessia is both a cultural region of Germany and the name of an individual German state.* The cultural region of Hesse includes both the State of Hesse and the area known as Rhenish Hesse in the neighbouring Rhineland-Palatinate state...
, 30 km south of Frankfurt am Main (Darmstadt Administrative District), in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
. A related undescribed species has been found in the nearby Eckfeld Maar.
Etymology
The name of the genus is a derivative of the Greek (), meaning 'one of prodigious size, strength, or achievement', and alluding to the TitanTitan (mythology)
In Greek mythology, the Titans were a race of powerful deities, descendants of Gaia and Uranus, that ruled during the legendary Golden Age....
s of Greek mythology; and the Greek word () meaning 'ant', gender feminine. The specific epithet of the new species is formed from the surname of the collector of the holotype, Louis Lube.
Taxonomy
Archibald et al. in 2011 erected the genus Titanomyrma, described the species Titanomyrma lubei and proposed two new combinations, T. giganteum (formerly Formicium giganteum Lutz, 1986) and T. simillimum (formerly F. simillimum Lutz, 1986). T. giganteum has been designated the type speciesType species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
for the genus.
The genus Titanomyrma is differentiated from others in the family by the shape of the gaster
Gaster
The gaster is the bulbous posterior portion of the metasoma found in Apocrita Hymenoptera . This begins with abdominal segment III on most ants, but some make a postpetiole out of segment III, in which case the gaster begins with abdominal segment IV....
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.
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. giganteum – 1.40, and T. simillimum – 1.50. 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 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.
Titanomyrma giganteum is the largest giant ant ever found, larger than the biggest extant giant ants, which are the 5 centimetres (2 in) long driver ants of the Dorylus
Dorylus
The army ant genus Dorylus, also known as driver ants, safari ants, or siafu, is found primarily in central and east Africa, although the range also extends to tropical Asia. The term siafu is a loanword from Swahili, and is one of numerous similar words from regional Bantu languages used by...
genus, found in Central
Central Africa
Central Africa is a core region of the African continent which includes Burundi, the Central African Republic, Chad, the Democratic Republic of the Congo, and Rwanda....
and East Africa
East Africa
East Africa or Eastern Africa is the easterly region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:...
. The fossils indicate that the males grew up to 3 centimetres (1.2 in) and the queens
Queen ant
A queen ant is an adult, reproducing female ant in an ant colony; generally she will be the mother of all the other ants in that colony. Some female ants do not need to mate to produce offspring, reproducing through asexual parthenogenesis or cloning and all of those offspring will be female.Ant...
grew to 6 centimetres (2.4 in). It had a wingspan of about 15 centimetres (5.9 in).
Paleo-ecological implications
The fossils of Titanomyrma giganteum, the first of the genus to be discovered, are very well preserved. They show that T. giganteum did not possess a stingStinger
-Biology:* Stinger, an organ or body part found in various animals that usually delivers some kind of venom.* Stinger , a minor neurological injury suffered by athletes.-Sports and entertainment:...
and did not have a closing mechanism on the crop
Crop (anatomy)
A crop is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion that is found in many animals, including gastropods, earthworms, leeches, insects, birds, and even some dinosaurs.- Bees :Cropping is used by bees to temporarily store nectar of flowers...
. It is surmised that it must have sprayed formic acid
Formic acid
Formic acid is the simplest carboxylic acid. Its chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings. In fact, its name comes from the Latin word for ant, formica, referring to its early...
as a defence
Biological defense
In biology,*often biological defense mechanism, a form of adaptation that promotes the survivability of an organism by protecting it from its natural enemies. Also see chemical defense.In law,...
, and either ate fresh food, in the manner of leaf-cutters, or was carnivorous
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
. Its modern relatives include driver ant
Dorylus
The army ant genus Dorylus, also known as driver ants, safari ants, or siafu, is found primarily in central and east Africa, although the range also extends to tropical Asia. The term siafu is a loanword from Swahili, and is one of numerous similar words from regional Bantu languages used by...
s and Titanomyrma may have been a precursor species, possibly following a raiding lifestyle and butchering large animals.
Titanomyrma lubei is related to fossil giant ants previously found in Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
and in the Isle of Wight
Isle of Wight
The Isle of Wight is a county and the largest island of England, located in the English Channel, on average about 2–4 miles off the south coast of the county of Hampshire, separated from the mainland by a strait called the Solent...
in southern England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
dating from the same period. It is the first complete giant ant fossil from North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
; previous evidence that big ants lived in North America during the Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
included an ancient ant wing from Tennessee
Tennessee
Tennessee is a U.S. state located in the Southeastern United States. It has a population of 6,346,105, making it the nation's 17th-largest state by population, and covers , making it the 36th-largest by total land area...
. It is a further example, in the northern temperate regions, of tropical fauna and flora such as hippopotamus
Hippopotamus
The hippopotamus , or hippo, from the ancient Greek for "river horse" , is a large, mostly herbivorous mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae After the elephant and rhinoceros, the hippopotamus is the third largest land mammal and the heaviest...
precursors, tropical plankton
Plankton
Plankton are any drifting organisms that inhabit the pelagic zone of oceans, seas, or bodies of fresh water. That is, plankton are defined by their ecological niche rather than phylogenetic or taxonomic classification...
and pollen
Pollen
Pollen is a fine to coarse powder containing the microgametophytes of seed plants, which produce the male gametes . Pollen grains have a hard coat that protects the sperm cells during the process of their movement from the stamens to the pistil of flowering plants or from the male cone to the...
from tropical palms. Titanomyrma lubei supports the idea that during the Eocene , conditions such as land bridge
Land bridge
A land bridge, in biogeography, is an isthmus or wider land connection between otherwise separate areas, over which animals and plants are able to cross and colonise new lands...
s and hot spells existed which permitted the spread of ancient warmth-loving insects and other forms of life from Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
to North America or vice versa, which would not have occurred had the temperature been uniformly cool throughout.