Eurypterina is one of two

suborders Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...

eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 million years ago. The group is ...

s, an extinct group of

chelicerate The subphylum Chelicerata (from New Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, ...

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

s commonly known as "sea scorpions". Eurypterine eurypterids are sometimes informally known as "swimming eurypterids". They are known from fossil deposits worldwide, though primarily in North America and

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located enti ...

. Seventy-five percent of

species are eurypterines; this represents 99% of specimens. The superfamily

Pterygotioidea Pterygotioidea (the name deriving from the type genus ''Pterygotus'', meaning "winged one") is a superfamily of eurypterids, an extinct group of aquatic arthropods. Pterygotioids were the most derived members of the infraorder Diploperculata and ...

is the most species-rich clade, with 56 species, followed by the

Adelophthalmoidea Adelophthalmidae (the name deriving from the type genus ''Adelophthalmus'', meaning "no obvious eyes") is a family of eurypterids, an extinct group of aquatic arthropods. Adelophthalmidae is the only family classified as part of the superfamily ...

with 43 species; as

sister taxa In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and t ...

, they comprise the most derived eurypterines.

includes the

pterygotid Pterygotidae (the name deriving from the type genus ''Pterygotus'', meaning "winged one") is a family of eurypterids, an extinct group of aquatic arthropods. They were members of the superfamily Pterygotioidea. Pterygotids were the largest know ...

s, which are the only eurypterids known to have a cosmopolitan distribution. Though more numerous both in specimens and taxa, the eurypterines have the shorter temporal range of the two eurypterid suborders. They first appeared around the same time as the

Stylonurina Stylonurina is one of two suborders of eurypterids, a group of extinct arthropods commonly known as "sea scorpions". Members of the suborder are collectively and informally known as "stylonurine eurypterids" or "stylonurines". They are known fro ...

in the

Middle Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ...

. The suborder faced a slow extinction during the

Middle Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek (d ...

and

Late Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

, possibly tied to the emergence of jawed vertebrates. Every Eurypterine genus and lineage went extinct before the Carboniferous save for ''

Adelophthalmus ''Adelophthalmus'' is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Adelophthalmus'' have been discovered in deposits ranging in age from the Early Devonian to the Early Permian, which makes it the longest lived of ...

'' which would go extinct in the

Early Permian 01 or '01 may refer to: * The year 2001, or any year ending with 01 * The month of January * 1 (number) Music * 01'' (Richard Müller album), 2001 * ''01'' (Son of Dave album), 2000 * ''01'' (Urban Zakapa album), 2011 * ''O1'' (Hiroyuki Sawano ...

, millions of years before the Permian-Triassic extinction event that ended the stylonurines.

Description

The

and Eurypterina are most easily distinguished by the morphology of the posteriormost prosomal appendage. In the Stylonurina, this appendage takes the form of a long and slender walking leg, lacking a modified spine (termed podomere 7a). In the Eurypterina, the leg is most usually modified and broadened into a swimming paddle and always includes a podomere 7a. Swimming eurypterines represent the absolute majority of both known

species and known specimens, though the morphology of the walking stylonurines is almost as diverse in appearance, and the fossil record of the eurypterines may therefore simply be more complete than that of the stylonurines, possibly due to varying habitat preferences.

Paleobiogeography

The most basal eurypterines with swimming legs, the genus ''

Onychopterella ''Onychopterella'' ( , from Ancient Greek: ὄνῠξ (''ónyx''), "claw", and πτερόν (''pteron''), "wing") is a genus of predatory eurypterid ("sea scorpion"), an extinct group of aquatic arthropods. Fossils of ''Onychopterella'' have ...

'', are known from the east coast of

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final st ...

close to the equator (a region that today is South Africa) from the Late Ordovician. It is not known whether or not the swimming forms originated here or not, but it is speculated that they migrated from

Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, althoug ...

, since most stylonurines and basal swimming forms are predominantly known from Laurentia and Gondwana otherwise completely lacks basal swimming forms. The megalograptoids were likely the first major successful group of eurypterids, evidenced by a

Late Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ...

radiation. All known members of the Megalograptoidea are from the Middle to Late

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. ...

of Laurentia, though potential records from the

Middle Silurian Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek ( ...

Baltica Baltica is a paleocontinent that formed in the Paleoproterozoic and now constitutes northwestern Eurasia, or Europe north of the Trans-European Suture Zone and west of the Ural Mountains. The thick core of Baltica, the East European Craton, is ...

are known in the form of the genus '' Holmipterus suecicus'' (though its classification as a megalograptoid is questionable). Eurypteroids are known from Laurentia and Baltica, with one known species from

Avalonia Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, southern Ireland, and the eastern coast of North America. It is the source of many of the older rocks of We ...

. ''

Eurypterus ''Eurypterus'' ( ) is an extinct genus of eurypterid, a group of organisms commonly called "sea scorpions". The genus lived during the Silurian period, from around 432 to 418 million years ago. ''Eurypterus'' is by far the most well-studied and ...

'' and other eurypteroids appear to have been unable to spread beyond

Laurussia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around (Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pang ...

n waters. The genus ''Eurypterus'' in particular dominated many

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago (Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoi ...

eurypterid faunas of Laurentia. Despite its abundance, it appears to not have originated in Laurentia, the earliest records of the genus are from Baltica and ''Eurypterus'' was thus likely an invasive genus in Laurentia, albeit one that managed to adapt well to the new habitats. The majority of carcinosomatoid taxa are also known from Laurentia, Baltica and Avalonia. Isolated and fragmentary fossils from the

Late Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago (Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoi ...

Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making it ...

and the

Czech Republic The Czech Republic, or simply Czechia, is a landlocked country in Central Europe. Historically known as Bohemia, it is bordered by Austria to the south, Germany to the west, Poland to the northeast, and Slovakia to the southeast. Th ...

show that the

terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its ow ...

s of Annamia and Perunica were within the geographical range of the carcinosomatoids. Only a few basal carcinosomatoids (e.g. ''

Carcinosoma ''Carcinosoma'' (meaning "crab body") is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Carcinosoma'' are restricted to deposits of late Silurian (Late Llandovery to Early Pridoli) age. Classified as part of the fami ...

'' and ''

Paracarcinosoma ''Eusarcana'' (meaning "true flesh") is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Eusarcana'' have been discovered in deposits ranging in age from the Early Silurian to the Early Devonian. Classified as part ...

'') have been found in deeper waters whilst the more derived forms, such as ''

Mixopterus ''Mixopterus'' is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of ''Mixopterus'' have been discovered in deposits from Late Silurian age, and have been referred to several different species. Fossils have been recovered f ...

'' and ''

Lanarkopterus ''Lanarkopterus'' is a genus of prehistoric eurypterid with one recognised species, ''Lanarkopterus dolichoschelus''. ''Lanarkopterus'' was long seen as a species of the closely related ''Mixopterus'', though more complete specimens discovered in t ...

'' have not. Basal carcinosomatoids (

Carcinosomatidae Carcinosomatidae (the name deriving from the type genus ''Carcinosoma'', meaning "crab body")Meaning osomaat ''www.dictionary.com''. Retrieved 7 September 2018. is a family of Eurypterid, eurypterids, an extinct group of aquatic Arthropod, arthro ...

) are likely responsible for the fossil remains in Vietnam and the Czech Republic and may have had a distribution similar to the cosmopolitan distribution of the pterygotoids, though were not as common nor as successful. Adelophthalmoids were the longest lasting clade of eurypterines, becoming extinct in the

Middle Permian The Guadalupian is the second and middle series/ epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico and Texas, and dates between 272.95 ...

, this is in part due to the survival of ''Adelophthalmus'' beyond the

Middle Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, wher ...

. The earliest records of the genus are from the

Early Devonian The Early Devonian is the first of three epochs comprising the Devonian period, corresponding to the Lower Devonian series. It lasted from and began with the Lochkovian Stage , which was followed by the Pragian from and then by the Emsian, whi ...

of western

Germany Germany, officially the Federal Republic of Germany (FRG),, is a country in Central Europe. It is the most populous member state of the European Union. Germany lies between the Baltic and North Sea to the north and the Alps to the sou ...

, but following the amalgamation of

Pangaea Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 millio ...

during the Carboniferous and

Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Pale ...

, the genus gained an almost cosmopolitan distribution. The basalmost species in the entire clade are from

and most of the evolution within the basal members took place in

. By the Devonian, representatives were found in both

Siberia Siberia ( ; rus, Сибирь, r=Sibir', p=sʲɪˈbʲirʲ, a=Ru-Сибирь.ogg) is an extensive geographical region, constituting all of North Asia, from the Ural Mountains in the west to the Pacific Ocean in the east. It has been a part o ...

and Australia long before the formation of Pangaea. Although the

Pterygotoidea Pterygotioidea (the name deriving from the type genus ''Pterygotus'', meaning "winged one") is a superfamily of eurypterids, an extinct group of aquatic arthropods. Pterygotioids were the most derived members of the infraorder Diploperculata and ...

only existed for a period of about 40 million years during a time when most continents were widely separated, the clade is the eurypterid clade with the most cosmopolitan distribution. Like other eurypterines, they are most common in Laurentia, Baltica and Avalonia, but are also found commonly in other

paleocontinent A paleocontinent or palaeocontinent is a distinct area of continental crust that existed as a major landmass in the geological past. There have been many different landmasses throughout Earth's time. They range in sizes, some are just a collection ...

s. Fossil remains have been recovered from Australia,

Libya Libya (; ar, ليبيا, Lībiyā), officially the State of Libya ( ar, دولة ليبيا, Dawlat Lībiyā), is a country in the Maghreb region in North Africa. It is bordered by the Mediterranean Sea to the north, Egypt to the east, Su ...

Algeria ) , image_map = Algeria (centered orthographic projection).svg , map_caption = , image_map2 = , capital = Algiers , coordinates = , largest_city = capital , religi ...

Morocco Morocco (),, ) officially the Kingdom of Morocco, is the westernmost country in the Maghreb region of North Africa. It overlooks the Mediterranean Sea to the north and the Atlantic Ocean to the west, and has land borders with Algeria ...

Florida Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, a ...

Saudi Arabia Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in Western Asia. It covers the bulk of the Arabian Peninsula, and has a land area of about , making it the List of Asian countries by area, fifth-largest country in Asia ...

Iberia The Iberian Peninsula (), ** * Aragonese and Occitan: ''Peninsula Iberica'' ** ** * french: Péninsule Ibérique * mwl, Península Eibérica * eu, Iberiar penintsula also known as Iberia, is a peninsula A peninsula (; ) is a la ...

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the souther ...

, vast swaths of

, Bohemia and

. The earliest pterygotoids are from the latest

Llandovery Llandovery (; cy, Llanymddyfri ) is a market town and community in Carmarthenshire, Wales. It lies on the River Tywi and at the junction of the A40 and A483 roads, about north-east of Carmarthen, north of Swansea and west of Brecon. Hi ...

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to th ...

, Laurentia and South China and this mobility makes it difficult to pinpoint the geographical origin of the clade, though it is speculated to have been close to or in Laurentia like the Adelophthalmoidea.

Systematics and relationships

Eurypterina contains eight superfamilies -

Onychopterelloidea Onychopterellidae are an extinct family of eurypterids. The family is the only family classified as part of the superfamily Onychopterelloidea. Genera included are ''Alkenopterus'', ''Onychopterella'' and ''Tylopterella''.Dunlop, J. A., Penney, D ...

Moselopteroidea Moselopteridae are an extinct family of eurypterids. It is the only family classified as part of the superfamily Moselopteroidea, and contains three genera: '' Moselopterus'', ''Stoermeropterus'' and ''Vinetopterus''.Dunlop, J. A., Penney, D. & ...

Megalograptoidea Carcinosomatoidea is an extinct superfamily of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". It is one of the superfamilies classified as part of the suborder Eurypterina. Some carcinosomatoid genera ...

Eurypteroidea Eurypteroidea are an extinct superfamily of eurypterids. It contains three families (Dolichopteridae, Eurypteridae, Strobilopteridae) and two genera of uncertain classification, ''Paraeurypterus'' and ''Pentlandopterus''. Description Euryptero ...

Carcinosomatoidea Carcinosomatoidea is an extinct superfamily of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". It is one of the superfamilies classified as part of the suborder Eurypterina. Some carcinosomatoid genera ...

Waeringopteroidea Waeringopteridae is a family of eurypterids, an extinct group of aquatic arthropods. The Waeringopteridae is the only family classified as part of the superfamily Waeringopteroidea, which in turn is classified within the infraorder Diploperculata ...

and

. The relationships between them remain somewhat unclear, the

is thought to be relatively primitive (between ''

'' and the

) because they lack a

synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to hav ...

of all more derived swimming forms; the modified distal margin of the sixth podomere of the swimming leg. This position is not necessarily true, since the sixth podomere in the swimming leg resembles the reduced podomere found in the

Mixopteridae The Mixopteridae are a family of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". The family is one of two families contained in the superfamily Carcinosomatoidea (along with Carcinosomatidae), which in ...

, and they might instead belong between the Eurypteroidea and Carcinosomatoidea. In contrast to the Megalograptoidea, the

is a rather well-known clade that contains around 90% of all known eurypterid specimens. They were closely related, supported by numerous similarities, to the Carcinosomatoidea. The Carcinosomatoidea have a poorly resolved internal phylogeny, though can be easily recognised by

scorpion Scorpions are predatory arachnids of the order Scorpiones. They have eight legs, and are easily recognized by a pair of grasping pincers and a narrow, segmented tail, often carried in a characteristic forward curve over the back and always endi ...

-like appearance and heavily spinose appendages.

and

are the two most derived clades as well as the most taxonomically diverse ones. Adelophthalmoidea contains 43 species, whereas Pterygotioidea contains 56. The superfamilies classified as part of Eurypterina contain the following families: Jaekelopterus rhenaniae

Suborder Eurypterina Burmeister, 1843 * Superfamily

Lamsdell, 2011 ** Family

Onychopterellidae Onychopterellidae are an extinct family of eurypterids. The family is the only family classified as part of the superfamily Onychopterelloidea. Genera included are '' Alkenopterus'', ''Onychopterella'' and '' Tylopterella''.Dunlop, J. A., Penney, ...

Lamsdell, 2011 * Superfamily

Lamsdell, Braddy, & Tetlie, 2010 ** Family

Moselopteridae Moselopteridae are an extinct family of eurypterids. It is the only family classified as part of the superfamily Moselopteroidea, and contains three genera: '' Moselopterus'', ''Stoermeropterus'' and ''Vinetopterus''.Dunlop, J. A., Penney, D. & J ...

Lamsdell, Braddy, & Tetlie, 2010 * Superfamily

Burmeister, 1843 ** Family

Dolichopteridae Dolichopteridae is an extinct family of eurypterids that lived in the Silurian and Devonian periods. Description Dolichopterid eurypterids had outer surfaces that were either smooth or with pustules and semilunar scales. The compound eyes were ...

Kjellesvig-Waering & Størmer, 1952 ** Family

Eurypteridae Eurypteridae is an extinct family of eurypterids that lived in the Silurian and Devonian periods. The family is one of three families contained in the superfamily Eurypteroidea (along with Dolichopteridae and Strobilopteridae), which in turn is ...

Burmeister, 1843 ** Family

Strobilopteridae Strobilopteridae is an extinct family of eurypterids that lived in the Silurian and Devonian periods. The family is one of three families contained in the superfamily Eurypteroidea (along with Dolichopteridae and Eurypteridae), which in turn is ...

Lamsdell & Selden, 2013 * Superfamily

Størmer, 1934 ** Family

Megalograptidae Megalograptidae are a family of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". The megalograptids were likely the first major successful group of eurypterids, evidenced by a Late Ordovician radiation. ...

Caster & Kjellesvig-Waering, 1955 ** Family

Caster & Kjellesvig-Waering, 1955 * Superfamily

''(not formally published)'' ** Family

Waeringopteridae Waeringopteridae is a family of eurypterids, an extinct group of aquatic arthropods. The Waeringopteridae is the only family classified as part of the superfamily Waeringopteroidea, which in turn is classified within the infraorder Diploperculata ...

''(not formally published)'' * Superfamily

Tollerton, 1989 ** Family

Adelophthalmidae Adelophthalmidae (the name deriving from the type genus ''Adelophthalmus'', meaning "no obvious eyes") is a family of eurypterids, an extinct group of aquatic arthropods. Adelophthalmidae is the only family classified as part of the superfamily ...

Tollerton, 1989 * Superfamily

Clarke & Ruedemann, 1912 ** Family

Hughmilleriidae Hughmilleriidae (the name deriving from the type genus ''Hughmilleria'', which is named in honor of Scottish geologist Hugh Miller) is a family of eurypterids, an extinct group of aquatic arthropods. The hughmilleriids were the most basal member ...

Kjellesvig-Waering, 1951 ** Family

Slimonidae Slimonidae (the name deriving from the type genus ''Slimonia'', which is named in honor of Welsh fossil collector and surgeon Robert Slimon) is a family of eurypterids, an extinct group of aquatic arthropods. Slimonids were members of the superf ...

Novojilov, 1962 ** Family Ptergotidae Clarke & Ruedemann, 1912

Phylogeny

Eurypterines are characterised by the transformation of the posteriormost prosomal appendage into a swimming paddle, one of the main features used to distinguish them from the stylonurines. The cladogram presented below, simplified from a study by Tetlie, showcases the phylogenetic relationships of the Eurypterina based on this adaptation, and the enlargement of the

chelicerae The chelicerae () are the mouthparts of the subphylum Chelicerata, an arthropod group that includes arachnids, horseshoe crabs, and sea spiders. Commonly referred to as " jaws", chelicerae may be shaped as either articulated fangs, or simila ...

, which characterises the family

Pterygotidae Pterygotidae (the name deriving from the type genus '' Pterygotus'', meaning "winged one") is a family of eurypterids, an extinct group of aquatic arthropods. They were members of the superfamily Pterygotioidea. Pterygotids were the largest kn ...

, to be used for active prey capture.

References

{{Taxonbar, from=Q17136524 Ordovician first appearances Permian extinctions Arthropod suborders

Description

Paleobiogeography

Systematics and relationships

Phylogeny

See also

References