Trigonotarbida
Encyclopedia
The Order
Trigonotarbida is an extinct group of arachnid
s whose fossil
record extends from the late Silurian
to the early Permian
. These animals are known from several localities in Europe
and North America
, as well as a single record from Argentina
. Trigonotarbids can be envisaged as spider
-like arachnids, but without silk-producing spinnerets. They ranged in size from a few millimetres to a few centimetres in body length and had a segmented abdomen, with the tergites across the back of the animal's abdomen characteristically divided into three or five separate plates. Probably living as predators on other arthropods, some later trigonotarbid species were quite heavily armoured and protected themselves with spines and tubercles. About seventy species are currently known, with most fossils originating from the Carboniferous
Coal Measures
.
in England
by the famous English geologist Dean William Buckland
. He believed it to be a fossil beetle and named it Curculoides prestvicii. A much better preserved example was later discovered from Coseley
near Dudley
; also in the English West Midlands conurbation
. Described in 1871 by Henry Woodward
, he correctly identified it as an arachnid and renamed it Eophrynus prestvicii
– whereby the genus name comes from (, meaning 'dawn'), and Phrynus, a genus of living whip spider (Amblypygi). Woodward subsequently described another trigonotarbid, Brachypyge carbonis, from the Coal Measues of Mons
in Belgium
; although this fossil is only known from the abdomen and was initially mistaken for the back end of a crab
.
(now Poland
), including one he named Anthracomartus voelkelianus in honour of Herr Völkel, the foreman of the mine where it was discovered. This species was raised to a new, extinct, arachnid order which Karsch called Anthracomarti. The name is derived from (), the Greek word for coal
. A number of other fossils which would eventually be placed in Trigonotarbida were discovered around this time. Hans Bruno Geinitz
described Kreischeria wiedei from the Coal Measures of Zwickau
in Germany
, although he interpreted it as a fossil pseudoscorpion
. Johann Kušta described Anthracomartus krejcii from Rakovník
in the Czech Republic
, and published further descriptions in a number of subsequent papers. In 1884, Samuel Hubbard Scudder
described Anthracomartus trilobitus from Fayetteville, Arkansas
– the first trigonotarbid from North America
.
). Petrunkevitch's division of the trigonotarbids into two, unrelated, orders was noted above. In detail, he divided the arachnids into suborders based on the width of the division between the two parts of the body (the prosoma and opisthosoma
). Anthracomartida and another extinct order, Haptopoda
, were grouped into a subclass Stethostomata defined by a broad division of the body and downward-hanging mouthparts. Trigonotarbida was placed in its own subclass Soluta and defined as having a division of the body which was variable in width. Petrunkevitch's scheme was largely followed in subsequent studies of fossil arachnids.
. They questioned whether it was appropriate to define a group of animals on a variable character state and carried out the first cladistic analysis of fossil and living arachnids. They showed that trigonotarbids are closely related to a group of arachnids which have gone under various names (Caulogastra, Arachnidea, etc.), but for which the name Tetrapulmonata
has become most widespread. Members of the Tetrapulmonata include spider
s, whip spiders, whip scorpions and Schizomida and, together with trigonotarbids, share characters like two pairs of book lung
s and similar mouthparts with fangs operating rather like a pocket knife. In the most recent study of arachnid relationships, the Shear et al. hypothesis was largely supported and a group Pantetrapulmonata was proposed which comprises Trigonotarbida + Tetrapulmonata.
) were the last living descendants of the trigonotarbids. A similar hypothesis was reintroduced by Dunlop, who pointed out distinct similarities between these arachnid groups. Both have opisthosomal tergites divided into median and lateral plates and both have a complicated coupling mechanism between the prosoma and the opisthosoma which 'locks' the two halves of the body together. Although cladistic anylsis has tended to recover ricinuleids in their traditional position closely related to mites and ticks, further discoveries have revealed that the tip of the pedipalp ends in a small claw in both trigonotarbids and ricinuleids.
s, but can be easily recognised by having tergites on the dorsal side of the abdomen divided into median and lateral plates. This character is shared with ricinuleids (Ricinulei
) (see also Relationships). As in other arachnids, the body is divided into a prosoma (or cephalothorax) and opisthosoma
(or abdomen). Body length ranges from a couple of millimetres up to about 5 cm (2 in).
– and perhaps also Anthracosironidae – there is an additional pair of lateral eye tubercles which, at least in palaeocharinids, appear to have borne a series of individual lenses. In this sense palaeocharinids seem to be in the process of reducing a compound eye.
The chelicerae resemble those of a mygalomorph spider and are of the 'pocket-knife' type consisting of a basal segment and a sharp, curving fang. There is no evidence in well-preserved fossils for the opening of a venom gland, thus trigonotarbids were probably not venomous. The chelicerae seem to have hung underneath the body and may have been slightly retractable into the prosoma. Well preserved palaeocharinids show evidence for a small, slit-like mouth with an upper lip (a labrum or rostrum) and a lower lip (or labium). Inside the mouth there is some sort of filtering system formed from hairs or platelets which strongly suggests that trigonotarbids (like spiders and many other arachnids) could only eat preorally digested, liquified prey.
The pedipalps have the typical arachnid structure with a coxa, trochanter, femur, patella, tibia and tarsus. They are pediform, i.e. they look like small legs and were not modified into pincers. There is no evidence for a special sperm transfer device as in the modified palpal organ of male spiders. Interestingly, in at least the palaeocharinids and anthracomartids the tip of the pedipalp is modified into a small claw formed from the tarsal claw (or apotele) and a projection from the tarsus. As mentioned above, a very similar arrangement is seen at the end of the pedipalp in Ricinulei
.
The walking legs again follow the typical arachnid plan with a coxa, trochanter, femur, patella, tibia, metatarsus and tarsus. The coxae surround a single sternum. In well preserved palaeocharinids there is a ring, or annulus, around the trochanter–femur joint which may be the remains of an earlier leg segment. The legs are largely unmodified, although in Anthracosironidae the forelegs are quite large and spiny, presumably to help catch prey. The legs end in three claws, two large ones and a smaller median claw.
(or abdomen) consists of twelve segments. The first forms a so called 'locking ridge' and the last two a small pygidium.
A quite unusual feature, again shared with Ricinulei
, is that the first tergite of the opisthosoma
has a half-moon shape and fits into a pocket created by a fold at the back of the carapace. In this way the two halves of the body seem to have been 'locked' together. The function of this system is unknown and some of the more derived trigonotarbids seem to have lost it.
The first tergite usually forms the locking ridge (see above). In many trigonotarbids the second and third tergites have fused together to form a single larger plate, sometimes called a 'diplotergite'. Further tergites from segments 4 to 9 follow. Tergites 2–8 (2–9 in some families) are divided into median and lateral plates and this is one of the most instantly recognisable trigonotarbid features. In most families each tergite is divided into three plates, but in Anthracomartidae
there are five.
Ventrally, the first sternite seems to be missing. The next two sclerites (segments 2–3) bear the lungs and are probably highly modified and flattened appendages. The third and sometimes the fourth segments also bear raised structures which may be equivalent to the ventral sacs seen in some living arachnids like whip spiders (Amblypygi). The last three segments of the abdomen comprise a flat element surrouding two small ring-like segments forming a postabdomen or pygidium. No trigonotarbid has yet been found with a telson.
Remarkable and well preserved trigonotarbid fossils from the Rhynie chert
of Scotland
show that these animals had two pairs of book lung
s. Dating from around , these are the oldest known examples of lungs in any animal group and clearly indicate that trigonotarbids lived on land. The detailed structure of these fossil book lungs is almost identical to the book lungs of modern arachnids.
Some trigonotarbids, especially Carboniferous
species in the families Aphantomartidae, Kreischeriidae and Eophrynidae
have a heavily armoured body covered with tubercles and occasionally sharp spines. In some ways they resemble harvestmen of the Laniatores
suborder, although the two groups are not closely related.
Palaeocharinidae Hirst, 1923
Anthracomartidae
Haase, 1890
Anthracosironidae Pocock, 1903
Trigonotarbidae Petrunkevitch, 1949
Lissomartidae Dunlop, 1995
Aphantomartidae Petrunkevitch, 1945
Kreischeriidae Haase, 1890
Eophrynidae
Karsch, 1882
incertae sedis
nomina dubia
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Trigonotarbida is an extinct group of arachnid
Arachnid
Arachnids are a class of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although in some species the front pair may convert to a sensory function. The term is derived from the Greek words , meaning "spider".Almost all extant arachnids are terrestrial...
s whose fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
record extends from the late Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
to the early Permian
Permian
The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...
. These animals are known from several localities in 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...
and 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...
, as well as a single record from Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
. Trigonotarbids can be envisaged as spider
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
-like arachnids, but without silk-producing spinnerets. They ranged in size from a few millimetres to a few centimetres in body length and had a segmented abdomen, with the tergites across the back of the animal's abdomen characteristically divided into three or five separate plates. Probably living as predators on other arthropods, some later trigonotarbid species were quite heavily armoured and protected themselves with spines and tubercles. About seventy species are currently known, with most fossils originating from the Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
Coal Measures
Coal Measures
The Coal Measures is a lithostratigraphical term for the coal-bearing part of the Upper Carboniferous System. It represents the remains of fluvio-deltaic sediment, and consists mainly of clastic rocks interstratified with the beds of coal...
.
Historical background
The first trigonotarbid was described in 1837 from the Coal Measures of CoalbrookdaleCoalbrookdale
Coalbrookdale is a village in the Ironbridge Gorge in Shropshire, England, containing a settlement of great significance in the history of iron ore smelting. This is where iron ore was first smelted by Abraham Darby using easily mined "coking coal". The coal was drawn from drift mines in the sides...
in 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...
by the famous English geologist Dean William Buckland
William Buckland
The Very Rev. Dr William Buckland DD FRS was an English geologist, palaeontologist and Dean of Westminster, who wrote the first full account of a fossil dinosaur, which he named Megalosaurus...
. He believed it to be a fossil beetle and named it Curculoides prestvicii. A much better preserved example was later discovered from Coseley
Coseley
Coseley is a town located mostly within the Metropolitan Borough of Dudley in the English West Midlands. Part of the Black Country, it lies south east of Wolverhampton and north of Dudley....
near Dudley
Dudley
Dudley is a large town in the West Midlands county of England. At the 2001 census , the Dudley Urban Sub Area had a population of 194,919, making it the 26th largest settlement in England, the second largest town in the United Kingdom behind Reading, and the largest settlement in the UK without...
; also in the English West Midlands conurbation
West Midlands conurbation
The West Midlands conurbation is the name given to the large conurbation that includes the cities of Birmingham and Wolverhampton and the large towns of Dudley, Walsall, West Bromwich, Solihull, Stourbridge, Halesowen in the English West Midlands....
. Described in 1871 by Henry Woodward
Henry Woodward (geologist)
Henry Bolingbroke Woodward was an English geologist.He became assistant in the geological department of the British Museum in 1858, and in 1880 keeper of that department. He became FRS in 1873, LL.D in 1878, president of the Geological Society of London...
, he correctly identified it as an arachnid and renamed it Eophrynus prestvicii
Eophrynus prestvicii
Eophrynus prestvicii was a species of trigonotarbid. Scientists at Imperial College London created a detailed 3D computer model of the arachnid from fossils....
– whereby the genus name comes from (, meaning 'dawn'), and Phrynus, a genus of living whip spider (Amblypygi). Woodward subsequently described another trigonotarbid, Brachypyge carbonis, from the Coal Measues of Mons
Mons
Mons is a Walloon city and municipality located in the Belgian province of Hainaut, of which it is the capital. The Mons municipality includes the old communes of Cuesmes, Flénu, Ghlin, Hyon, Nimy, Obourg, Baudour , Jemappes, Ciply, Harmignies, Harveng, Havré, Maisières, Mesvin, Nouvelles,...
in Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
; although this fossil is only known from the abdomen and was initially mistaken for the back end of a crab
Crab
True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax...
.
A new arachnid order
In 1882 The German zoologist Ferdinand Karsch described a number of fossil arachnids from the Coal Measures of Neurode in SilesiaSilesia
Silesia is a historical region of Central Europe located mostly in Poland, with smaller parts also in the Czech Republic, and Germany.Silesia is rich in mineral and natural resources, and includes several important industrial areas. Silesia's largest city and historical capital is Wrocław...
(now Poland
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
), including one he named Anthracomartus voelkelianus in honour of Herr Völkel, the foreman of the mine where it was discovered. This species was raised to a new, extinct, arachnid order which Karsch called Anthracomarti. The name is derived from (), the Greek word for coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
. A number of other fossils which would eventually be placed in Trigonotarbida were discovered around this time. Hans Bruno Geinitz
Hans Bruno Geinitz
Hanns Bruno Geinitz was a German geologist, born at Altenburg, the capital of Saxe-Altenburg.He was educated at the universities of Berlin and Jena, and gained the foundations of his geological knowledge under Friedrich August von Quenstedt. In 1837 he took the degree of Ph.D. with a thesis on the...
described Kreischeria wiedei from the Coal Measures of Zwickau
Zwickau
Zwickau in Germany, former seat of the government of the south-western region of the Free State of Saxony, belongs to an industrial and economical core region. Nowadays it is the capital city of the district of Zwickau...
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...
, although he interpreted it as a fossil pseudoscorpion
Pseudoscorpion
A pseudoscorpion, , is an arachnid belonging to the order Pseudoscorpionida, also known as Pseudoscorpiones or Chelonethida....
. Johann Kušta described Anthracomartus krejcii from Rakovník
Rakovník
Rakovník is a town in the western part of the Central Bohemian Region of the Czech Republic located between the cities of Prague and Plzeň. It has a population of approximately 16,000.- Trade and business :...
in the Czech Republic
Czech Republic
The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....
, and published further descriptions in a number of subsequent papers. In 1884, Samuel Hubbard Scudder
Samuel Hubbard Scudder
Samuel Hubbard Scudder was an American entomologist and palaeontologist.Born in Boston, Massachusetts, Scudder may be most widely known for his essay on the importance of first-hand, careful observation in the natural sciences...
described Anthracomartus trilobitus from Fayetteville, Arkansas
Fayetteville, Arkansas
Fayetteville is the county seat of Washington County, and the third largest city in Arkansas. The city is centrally located within the county and is home to the University of Arkansas. Fayetteville is also deep in the Boston Mountains, a subset of The Ozarks...
– the first trigonotarbid 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...
.
Relationships
Early studies tended to confuse trigonotarbids with other living or extinct groups of arachnids; particularly harvestmen (OpilionesOpiliones
Opiliones are an order of arachnids commonly known as harvestmen. , over 6,400 species of harvestmen have been discovered worldwide, although the real number of extant species may exceed 10,000. The order Opiliones can be divided into four suborders: Cyphophthalmi, Eupnoi, Dyspnoi and Laniatores...
). Petrunkevitch's division of the trigonotarbids into two, unrelated, orders was noted above. In detail, he divided the arachnids into suborders based on the width of the division between the two parts of the body (the prosoma and opisthosoma
Opisthosoma
The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma . It is a distinctive feature of the subphylum Chelicerata...
). Anthracomartida and another extinct order, Haptopoda
Haptopoda
Haptopoda is an extinct arachnid order known exclusively from only eight specimens from the Upper Carboniferous of Coseley, Staffordshire, United Kingdom. It is monotypic, i.e. has only one species, Plesiosiro madeleyi described by Reginald Innes Pocock in his important 1911 monograph on British...
, were grouped into a subclass Stethostomata defined by a broad division of the body and downward-hanging mouthparts. Trigonotarbida was placed in its own subclass Soluta and defined as having a division of the body which was variable in width. Petrunkevitch's scheme was largely followed in subsequent studies of fossil arachnids.
Pantetrapulmonata
In the 1980s, Bill Shear and colleagues carried out an important study on well preserved Mid Devonian trigonotarbids from Gilboa, New YorkGilboa, New York
Gilboa is a town in Schoharie County, New York, United States. The population was 1,215 at the 2000 census.The Town of Gilboa is in the south part of the county and is southwest of Albany.- History :The town was first settled around 1760....
. They questioned whether it was appropriate to define a group of animals on a variable character state and carried out the first cladistic analysis of fossil and living arachnids. They showed that trigonotarbids are closely related to a group of arachnids which have gone under various names (Caulogastra, Arachnidea, etc.), but for which the name Tetrapulmonata
Tetrapulmonata
Tetrapulmonata is a non-ranked supra-ordinal group of arachnids. It is composed of Thelyphonida, Schizomida, Amblypygi and Araneae.-Etymology:...
has become most widespread. Members of the Tetrapulmonata include spider
Spider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
s, whip spiders, whip scorpions and Schizomida and, together with trigonotarbids, share characters like two pairs of book lung
Book lung
A book lung is a type of respiration organ used for atmospheric gas exchange and is found in arachnids, such as scorpions and spiders. Each of these organs is found inside a ventral abdominal cavity and connects with the surroundings through a small opening. Book lungs are not related to the lungs...
s and similar mouthparts with fangs operating rather like a pocket knife. In the most recent study of arachnid relationships, the Shear et al. hypothesis was largely supported and a group Pantetrapulmonata was proposed which comprises Trigonotarbida + Tetrapulmonata.
Trigonotarbids and ricinuleids
In 1892, Ferdinand Karsch suggested that the rare and rather bizarre looking ricinuleids (RicinuleiRicinulei
The Order Ricinulei is a group of arachnids known as hooded tickspiders. In older works they are sometimes referred to as Podogona., 60 extant species of ricinuleids have been described worldwide, all in the single family Ricinoididae. They occur today in west-central Africa and the Neotropical...
) were the last living descendants of the trigonotarbids. A similar hypothesis was reintroduced by Dunlop, who pointed out distinct similarities between these arachnid groups. Both have opisthosomal tergites divided into median and lateral plates and both have a complicated coupling mechanism between the prosoma and the opisthosoma which 'locks' the two halves of the body together. Although cladistic anylsis has tended to recover ricinuleids in their traditional position closely related to mites and ticks, further discoveries have revealed that the tip of the pedipalp ends in a small claw in both trigonotarbids and ricinuleids.
Anatomy
Trigonotarbids superficially resemble spiderSpider
Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...
s, but can be easily recognised by having tergites on the dorsal side of the abdomen divided into median and lateral plates. This character is shared with ricinuleids (Ricinulei
Ricinulei
The Order Ricinulei is a group of arachnids known as hooded tickspiders. In older works they are sometimes referred to as Podogona., 60 extant species of ricinuleids have been described worldwide, all in the single family Ricinoididae. They occur today in west-central Africa and the Neotropical...
) (see also Relationships). As in other arachnids, the body is divided into a prosoma (or cephalothorax) and opisthosoma
Opisthosoma
The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma . It is a distinctive feature of the subphylum Chelicerata...
(or abdomen). Body length ranges from a couple of millimetres up to about 5 cm (2 in).
Prosoma
The prosoma is covered by the carapace and always bears a pair of median eyes. In the probably basal families Palaeocharinidae, AnthracomartidaeAnthracomartidae
Anthracomartidae Haase, 1890 is a family of the extinct arachnid order Trigonotarbida.-Genera:*Anthracomartus Karsch, 1882*Brachylycosa Frič, 1904*Brachypyge Woodward, 1878*Cleptomartus Petrunkevitch, 1949*Coryphomartus Petrunkevitch, 1945...
– and perhaps also Anthracosironidae – there is an additional pair of lateral eye tubercles which, at least in palaeocharinids, appear to have borne a series of individual lenses. In this sense palaeocharinids seem to be in the process of reducing a compound eye.
The chelicerae resemble those of a mygalomorph spider and are of the 'pocket-knife' type consisting of a basal segment and a sharp, curving fang. There is no evidence in well-preserved fossils for the opening of a venom gland, thus trigonotarbids were probably not venomous. The chelicerae seem to have hung underneath the body and may have been slightly retractable into the prosoma. Well preserved palaeocharinids show evidence for a small, slit-like mouth with an upper lip (a labrum or rostrum) and a lower lip (or labium). Inside the mouth there is some sort of filtering system formed from hairs or platelets which strongly suggests that trigonotarbids (like spiders and many other arachnids) could only eat preorally digested, liquified prey.
The pedipalps have the typical arachnid structure with a coxa, trochanter, femur, patella, tibia and tarsus. They are pediform, i.e. they look like small legs and were not modified into pincers. There is no evidence for a special sperm transfer device as in the modified palpal organ of male spiders. Interestingly, in at least the palaeocharinids and anthracomartids the tip of the pedipalp is modified into a small claw formed from the tarsal claw (or apotele) and a projection from the tarsus. As mentioned above, a very similar arrangement is seen at the end of the pedipalp in Ricinulei
Ricinulei
The Order Ricinulei is a group of arachnids known as hooded tickspiders. In older works they are sometimes referred to as Podogona., 60 extant species of ricinuleids have been described worldwide, all in the single family Ricinoididae. They occur today in west-central Africa and the Neotropical...
.
The walking legs again follow the typical arachnid plan with a coxa, trochanter, femur, patella, tibia, metatarsus and tarsus. The coxae surround a single sternum. In well preserved palaeocharinids there is a ring, or annulus, around the trochanter–femur joint which may be the remains of an earlier leg segment. The legs are largely unmodified, although in Anthracosironidae the forelegs are quite large and spiny, presumably to help catch prey. The legs end in three claws, two large ones and a smaller median claw.
Opisthosoma
The trigonotarbid opisthosomaOpisthosoma
The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma . It is a distinctive feature of the subphylum Chelicerata...
(or abdomen) consists of twelve segments. The first forms a so called 'locking ridge' and the last two a small pygidium.
A quite unusual feature, again shared with Ricinulei
Ricinulei
The Order Ricinulei is a group of arachnids known as hooded tickspiders. In older works they are sometimes referred to as Podogona., 60 extant species of ricinuleids have been described worldwide, all in the single family Ricinoididae. They occur today in west-central Africa and the Neotropical...
, is that the first tergite of the opisthosoma
Opisthosoma
The opisthosoma is the posterior part of the body in some arthropods, behind the prosoma . It is a distinctive feature of the subphylum Chelicerata...
has a half-moon shape and fits into a pocket created by a fold at the back of the carapace. In this way the two halves of the body seem to have been 'locked' together. The function of this system is unknown and some of the more derived trigonotarbids seem to have lost it.
The first tergite usually forms the locking ridge (see above). In many trigonotarbids the second and third tergites have fused together to form a single larger plate, sometimes called a 'diplotergite'. Further tergites from segments 4 to 9 follow. Tergites 2–8 (2–9 in some families) are divided into median and lateral plates and this is one of the most instantly recognisable trigonotarbid features. In most families each tergite is divided into three plates, but in Anthracomartidae
Anthracomartidae
Anthracomartidae Haase, 1890 is a family of the extinct arachnid order Trigonotarbida.-Genera:*Anthracomartus Karsch, 1882*Brachylycosa Frič, 1904*Brachypyge Woodward, 1878*Cleptomartus Petrunkevitch, 1949*Coryphomartus Petrunkevitch, 1945...
there are five.
Ventrally, the first sternite seems to be missing. The next two sclerites (segments 2–3) bear the lungs and are probably highly modified and flattened appendages. The third and sometimes the fourth segments also bear raised structures which may be equivalent to the ventral sacs seen in some living arachnids like whip spiders (Amblypygi). The last three segments of the abdomen comprise a flat element surrouding two small ring-like segments forming a postabdomen or pygidium. No trigonotarbid has yet been found with a telson.
Remarkable and well preserved trigonotarbid fossils from the Rhynie chert
Rhynie chert
The Rhynie chert is an Early Devonian sedimentary deposit exhibiting extraordinary fossil detail or completeness . It is exposed near the village of Rhynie, Aberdeenshire, Scotland; a second unit, the Windyfield chert, is located some 700 m away...
of Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...
show that these animals had two pairs of book lung
Book lung
A book lung is a type of respiration organ used for atmospheric gas exchange and is found in arachnids, such as scorpions and spiders. Each of these organs is found inside a ventral abdominal cavity and connects with the surroundings through a small opening. Book lungs are not related to the lungs...
s. Dating from around , these are the oldest known examples of lungs in any animal group and clearly indicate that trigonotarbids lived on land. The detailed structure of these fossil book lungs is almost identical to the book lungs of modern arachnids.
Some trigonotarbids, especially Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
species in the families Aphantomartidae, Kreischeriidae and Eophrynidae
Eophrynidae
Eophrynidae is a family of the extinct arachnid order Trigonotarbida. Eophrynids lived during the Carboniferous period in what is now modern Europe and North America.-Genera:*Areomartus Petrunkevitch, 1913*Eophrynus Woodward, 1871...
have a heavily armoured body covered with tubercles and occasionally sharp spines. In some ways they resemble harvestmen of the Laniatores
Laniatores
Laniatores is the largest suborder of the arachnid order Opiliones with over 4,000 described species worldwide. The majority of the species are highly dependent on humid environments and usually correlated with tropical and temperate forest habitats....
suborder, although the two groups are not closely related.
Taxonomy
plesion taxa- Palaeotarbus Dunlop, 1999
- Palaeotarbus jerami (Dunlop, 1996) – Late Silurian, England
- Alkenia Størmer, 1970
- Alkenia mirabilis Størmer, 1970 – Early Devonian, Germany
Palaeocharinidae Hirst, 1923
- Aculeatarbus Shear, Selden & Rolfe, 1987
- Aculeatarbus depressus Shear, Selden & Rolfe, 1987 – Mid Devonian, United States
- Gelasinotarbus Shear, Selden & Rolfe, 1987
- Gelasinotarbus bifidus Shear, Selden & Rolfe, 1987 – Mid Devonian, United States
- Gelasinotarbus bonamoae Shear, Selden & Rolfe, 1987 – Mid Devonian, United States
- Gelasinotarbus heptops Shear, Selden & Rolfe, 1987 – Mid Devonian, United States
- Gelasinotarbus reticulatus Shear, Selden & Rolfe, 1987 – Mid Devonian, United States
- Gigantocharinus Shear, 2000
- Gigantocharinus szatmaryi Shear, 2000 – Late Devonian, United States
- Gilboarachne Shear, Selden & Rolfe, 1987
- Gilboarachne griersoni Shear, Selden & Rolfe, 1987 – Mid Devonian, United States
- Palaeocharinus Hirst, 1923
- Palaeocharinus calmani Hirst, 1923 – Early Devonian, Scotland
- Palaeocharinus hornei (Hirst, 1923) – Early Devonian, Scotland
- Palaeocharinus kidstoni Hirst, 1923 – Early Devonan, Scotland
- Palaeocharinus rhyniensis Hirst, 1923 – Early Devonian, Scotland
- Palaeocharinus scourfieldi Hirst, 1923 – Early Devonian, Scotland
- Palaeocharinus tuberculatus Fayers, Dunlop & Trewin, 2005 – Early Devonian, Scotland
Anthracomartidae
Anthracomartidae
Anthracomartidae Haase, 1890 is a family of the extinct arachnid order Trigonotarbida.-Genera:*Anthracomartus Karsch, 1882*Brachylycosa Frič, 1904*Brachypyge Woodward, 1878*Cleptomartus Petrunkevitch, 1949*Coryphomartus Petrunkevitch, 1945...
Haase, 1890
- Anthracomartus Karsch, 1882
- synonyms
- = Brachylycosa Frič, 1904
- = Cleptomartus Petrunkevitch, 1949
- = Coryphomartus Petrunkevitch, 1945
- = Cryptomartus Petrunkevitch, 1945
- = Oomartus Petrunkevitch, 1953
- = Perneria Frič, 1904
- = Pleomartus Petrunkevitch, 1945
- = Promygale Frič, 1901
- Anthracomartus bohemica (Frič, 1901) – Late Carboniferous, Czech Republic
- Anthracomartus carcinoides (Frič, 1901) – Late Carboniferous, Czech Republic
- synonyms
- = Promygale rotunda Frič, 1901
- = Perneria salticoides Frič, 1904
- synonyms
- Anthracomartus elegans Frič, 1901 – Late Carboniferous, Czech Republic
- Anthracomartus hindi Pocock, 1911 – Late Carboniferous, England
- synonyms
- = Cleptomartus hangardi Guthörl, 1965
- = Cryptomartus meyeri Guthörl, 1964
- = Cleptomartus planus Petrunkevitch, 1949
- = Cryptomartus rebskei Brauckmann, 1984
- synonyms
- Anthracomartus granulatus Frič, 1904 – Late Carboniferous, Poland
- Anthracomartus janae (Opluštil, 1986) – Late Carboniferous, Czech Republic
- Anthracomartus kustae Petrunkevitch, 1953 – Late Carboniferous, Czech Republic
- Anthracomartus minor Kušta, 1884 – Late Carboniferous, Czech Republic
- synonym
- = Anthracomartus socius Kušta, 1888
- synonym
- Anthracomartus nyranensis (Petrunkevitch, 1953) – Late Carboniferous, Czech Republic
- Anthracomartus palatinus Ammon, 1901 – Late Carboniferous, Germany
- Anthracomartus priesti Pocock, 1911 – Late Carboniferous, England
- synonyms
- = Anthracomartus denuiti Pruvost, 1922
- = Cleptomartus plautus Petrunkevitch, 1949
- synonyms
- Anthracomartus radvanicensis (Opluštil, 1985) – Late Carboniferous, Czech Republic
- Anthracomartus triangularis Petrunkevitch, 1913 – Late Carboniferous, Canada
- Anthracomartus trilobitus Scudder, 1884 – Late Carboniferous, United States
- Anthracomartus voelkelianus Karsch, 1882 – Late Carboniferous, Poland
- synonyms
- Brachypyge Woodward, 1878
- Brachypyge carbonis Woodward, 1878 – Late Carboniferous, Belgium
- Maiocercus Pocock, 1911
- Maiocercus celticus (Pocock, 1902) – Late Carboniferous, Europe
Anthracosironidae Pocock, 1903
- Anthracosiro Pocock, 1903
- Anthracosiro fritschii Pocock, 1903 – Late Carboniferous, Europe
- Anthracosiro woodwardi Pocock, 1903 – Late Carboniferous, Europe
- Arianrhoda Dunlop & Selden, 2004
- Arianrhoda bennetti Dunlop & Selden, 2004 – Early Devonian, Wales
Trigonotarbidae Petrunkevitch, 1949
- Archaeomartus Størmer, 1970 – Early Devonian, Germany
- Archaeomartus levis Størmer, 1970 – Early Devonian, Germany
- Archaeomartus roessleri Dunlop & Brauckmann, 2006 – Late Carboniferous, Germany
- Archaeomartus tuberculatus Størmer, 1970 – Early Devonian, Germany
- Trigonotarbus Pocock, 1911
- Trigonotarbus arnoldi Petrunkevitch, 1955 – Late Carboniferous, France
- Trigonotarbus johnsoni Pocock, 1911 – Late Carboniferous, England
- Trigonotarbus stoermeri Schultka, 1991 – Early Devonian, Germany
Lissomartidae Dunlop, 1995
- Lissomartus Petrunkevitch, 1949
- Lissomartus carbonarius (Petrunkevitch, 1913) – Late Carboniferous, United States
- Lissomartus schucherti (Petrunkevitch, 1913) – Late Carboniferous, United States
Aphantomartidae Petrunkevitch, 1945
- Aphantomartus Pocock, 1911
- Aphantomartus areolatus Pocock, 1911 – Early/Late Carboniferous, Europe
- Aphantomartus ilfeldicus (Scharf, 1924) – Permian, Germany
- Aphantomartus pustulatus (Scudder, 1884) – Late Carboniferous, Europe, North America
Kreischeriidae Haase, 1890
- Anzinia Petrunkevitch, 1953
- Anzinia thevenini (Pruvost, 1919) – Late Carboniferous, France
- Gondwanarache Pinto & Hünicken, 1980
- Gondwanarache argentinensis Pinto & Hünicken, 1980 – Late Carboniferous, Argentina
- Hemikreischeria Frič, 1904
- Hemikreischeria geinitzi (Thevenin, 1902) – Late Carboniferous, France
- Kreischeria Geinitz, 1882
- Kreischeria wiedei Geinitz, 1882 – Late Carboniferous, Germany
- Pseudokreischeria Petrunkevitch, 1953
- Pseudokreischeria pococki (Gill, 1924) – Late Carboniferous, England
Eophrynidae
Eophrynidae
Eophrynidae is a family of the extinct arachnid order Trigonotarbida. Eophrynids lived during the Carboniferous period in what is now modern Europe and North America.-Genera:*Areomartus Petrunkevitch, 1913*Eophrynus Woodward, 1871...
Karsch, 1882
- Areomartus Petrunkevitch, 1913
- Areomartus ovatus Petrunkevitch, 1913 – Late Carboniferous, United States
- EophrynusEophrynusEophrynus is an extinct genus of arachnids from the trigonotarbid group, which lived during the Late Carboniferous period in Europe. The genus was first described in 1871 by Henry Woodward . The name comes from Eo, meaning 'dawn', and Phrynus, a genus of living whip spider .Two species have been...
Woodward, 1871- Eophrynus prestviciiEophrynus prestviciiEophrynus prestvicii was a species of trigonotarbid. Scientists at Imperial College London created a detailed 3D computer model of the arachnid from fossils....
(Buckland, 1837) – Late Carboniferous, England - Eophrynus udus Brauckmann, Koch & Kemper, 1985 – Late Carboniferous, Germany
- Eophrynus prestvicii
- Nyranytarbus Harvey & Selden, 1995
- Nyranytarbus hofmanni (Frič, 1901) – Late Carboniferous, Czech Republic
- Nyranytarbus longipes (Frič, 1901) – Late Carboniferous, Czech Republic
- Petrovicia Frič, 1904
- Petrovicia proditoria Frič, 1904 – Late Carboniferous, Czech Republic
- Planomartus Petrunkevitch, 1953
- Planomartus krejcii (Kušta, 1883) – Late Carboniferous, Czech Republic
- Pleophrynus Petrunkevitch, 1945a
- Pleophrynus verrucosus (Pocock, 1911) – Late Carboniferous, UK, United States
- Pocononia Petrunkevitch, 1953
- Pocononia whitei (Ewing, 1930) – Early Carboniferous, United States
- Somaspidion Jux, 1982
- Somaspidion hammapheron Jux, 1982
- Stenotrogulus Frič, 1904
- Stenotrogulus salmii (Stur, 1877) – Late Carboniferous, Czech Republic
- Vratislavia Frič, 1904
- Vratislavia silesica (Roemer, 1878 – Late Carboniferous, Poland
incertae sedis
Incertae sedis
, is a term used to define a taxonomic group where its broader relationships are unknown or undefined. Uncertainty at specific taxonomic levels is attributed by , , and similar terms.-Examples:*The fossil plant Paradinandra suecica could not be assigned to any...
- Anthracophrynus Andrée, 1913
- Anthracophrynus tuberculatus Andrée, 1913 – Late Carboniferous, Germany
- ‘Eophrynus’ scharfi Scharf, 1924 – Early Permian, Germany
nomina dubia
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...
- Anthracomartus buchi (Goldenberg, 1873) – Late Carboniferous, Germany
- Anthracomartus hageni (Goldenberg, 1873) – Late Carboniferous, Germany
- Elaverimartus pococki Petrunkevitch, 1953 – Late Carboniferous, Scotland
- Eurymartus latus Matthew, 1895 – Late Carboniferous, Canada
- ?Eurymartus spinulosus Matthew, 1895 – Late Carboniferous, Canada
- Trigonomartus woodruffi (Scudder, 1893) – Late Carboniferous, United States