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161-418: Pterygotus is a genus of giant predatory eurypterid , a group of extinct aquatic arthropods . Fossils of Pterygotus have been discovered in deposits ranging in age from Middle Silurian to Late Devonian , and have been referred to several different species. Fossils have been recovered from four continents; Australia , Europe, North America and South America, which indicates that Pterygotus might have had

322-460: A nomen vanum ("baseless name") as the species is impossible to define. The fossil material with which it was described is undiagnostic and insufficient to establish any meaningful characteristics and as such many fragmentary pterygotid fossils have been referred to it throughout its long history, rendering it effectively synonymous with the family Pterygotidae. More often than not, these fragments consist of patches of pterygotid integument preserving

483-564: A cosmopolitan distribution . Though the eurypterids continued to be abundant and diversify during the Early Devonian (for instance leading to the evolution of the pterygotid Jaekelopterus , the largest of all arthropods), the group was one of many heavily affected by the Late Devonian extinction . The extinction event, only known to affect marine life (particularly trilobites, brachiopods and reef -building organisms) effectively crippled

644-408: A lung , plastron or a pseudotrachea . Plastrons are organs that some arthropods evolved secondarily to breathe air underwater. This is considered an unlikely explanation since eurypterids had evolved in water from the start and they would not have organs evolved from air-breathing organs present. In addition, plastrons are generally exposed on outer parts of the body while the eurypterid gill tract

805-546: A North American species, P. cobbi , from the Pridoli of the United States and Canada. P. arcuatus was originally described from a syntypic series (a series of specimens out of which a particular holotype is not designated) of fossil remains by John William Salter, containing five separate fossil specimens. In 1961, 102 years after its description, Erik N. Kjellesvig-Waering noted that only one of these specimens (Number 89587 of

966-457: A eurypterid, as confirmed by further findings. Dawson reclassified it as a eurypterid in 1871. Kjellesvig-Waering in 1964 assigned it as a questionable species of Pterygotus . In 1921, Ruedemann described an eurypterid fauna from the Vernon Formation of Pittsford , New York. Among them, the species P. vernonensis was erected based on two small short carapaces. The outline and position of

1127-459: A few genera, such as Adelophthalmus and Pterygotus , achieved a cosmopolitan distribution with fossils being found worldwide. Like all other arthropods , eurypterids possessed segmented bodies and jointed appendages (limbs) covered in a cuticle composed of proteins and chitin . As in other chelicerates , the body was divided into two tagmata (sections); the frontal prosoma (head) and posterior opisthosoma (abdomen). The prosoma

1288-726: A gait like that of most modern insects. The weight of its long abdomen would have been balanced by two heavy and specialized frontal appendages, and the center of gravity might have been adjustable by raising and positioning the tail. Preserved fossilized eurypterid trackways tend to be large and heteropodous and often have an associated telson drag mark along the mid-line (as with the Scottish Hibbertopterus track). Such trackways have been discovered on every continent except for South America. In some places where eurypterid fossil remains are otherwise rare, such as in South Africa and

1449-644: 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 likely to have appeared first either during the Early Ordovician or Late Cambrian period. With approximately 250 species, the Eurypterida is the most diverse Paleozoic chelicerate order. Following their appearance during

1610-469: A highly taxonomically diverse genus. P. barrandei was named in 1898 and has fossil representation in Pridoli age deposits of the Czech Republic . P. barrandei is noted to be very similar to P. cobbi , and a close relation between the two species is assumed. Despite many similarities, the two species do have some differences, most prominently in the cheliceral teeth of the free rami. The largest tooth of

1771-486: A kind of "double tooth combination" that is also present in some other species, such as P. lightbodyi , P. impacatus and Erettopterus brodiei . The total length of the fossilized ramus is 2.35 cm (1 in), but it likely only represents around half of the full ramus. As in other species (and the Pterygotidae in general), the teeth are finely ribbed. It can be distinguished from all other species of Pterygotus by

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1932-597: A large chelicera (specimen number 53890 in the British Museum of Natural History ) originally doubtfully referred to Erettopterus bilobus , P. lanarkensis more closely resembles P. anglicus than it does species of Erettopterus . The terminal tooth (broken in this specimen) is 0.9 cm in length and the central tooth is unusually short. The combination of an unusually long terminal tooth and an underdeveloped central tooth differentiates P. lanarkensis from other species of Pterygotus . Several features distinguish it from

2093-416: A manner similar to modern horseshoe crabs, by grabbing and shredding food with their appendages before pushing it into their mouth using their chelicerae. Fossils preserving digestive tracts have been reported from fossils of various eurypterids, among them Carcinosoma , Acutiramus and Eurypterus . Though a potential anal opening has been reported from the telson of a specimen of Buffalopterus , it

2254-425: A meter (1.64 ft) even if the extended chelicerae are not included. Two other eurypterids have also been estimated to have reached lengths of 2.5 metres; Erettopterus grandis (closely related to Jaekelopterus ) and Hibbertopterus wittebergensis , but E. grandis is very fragmentary and the H. wittenbergensis size estimate is based on trackway evidence, not fossil remains. The family of Jaekelopterus ,

2415-451: A nearly cosmopolitan (worldwide) distribution. The type species, P. anglicus , was described by Swiss naturalist Louis Agassiz in 1839, who gave it the name Pterygotus , meaning "winged one". Agassiz mistakenly believed the remains were of a giant fish; he would only realize the mistake five years later in 1844. Pterygotus was among the largest eurypterids. Isolated fossil remains of a large chelicera (frontal appendage) suggests that

2576-471: A rowing type of propulsion similar to that of crabs and water beetles . Larger individuals may have been capable of underwater flying (or subaqueous flight ) in which the motion and shape of the paddles are enough to generate lift , similar to the swimming of sea turtles and sea lions . This type of movement has a relatively slower acceleration rate than the rowing type, especially since adults have proportionally smaller paddles than juveniles. However, since

2737-548: A telson (which is far more similar to Erettopterus than to Pterygotus ). Most of these specimens have been lost since the 1870s, the last record being that they were all in the cabinet of a Dr. McCullough of Abergavenny. The 20th century would see the description of additional species of Pterygotus in North America as well, including the Silurian P. marylandicus (1964, Maryland , USA) and P. monroensis (1902, New York, USA),

2898-404: A telson, has unusual and pronounced ridges that are not seen in any known species of Pterygotus , nor in any other genus of pterygotid eurypterids, which makes its assignment to Pterygotus questionable. In 1964, two species described by Kjellesvig-Waering increased the known range of Pterygotus to Scotland ( P. lanarkensis ) and Estonia ( P. impacatus ), both Ludlow in age. P. lanarkensis

3059-515: Is a junior synonym of Cancer grammarius Linnaeus, 1758 . Although the International Code of Nomenclature for algae, fungi, and plants does not contain the same explicit statement, examples make it clear that the original name is used, so that the "type species" of a genus name need not have a name within that genus. Thus in Article 10, Ex. 3, the type of the genus name Elodes is quoted as

3220-547: Is a genital appendage. This appendage, an elongated rod with an internal duct, is found in two distinct morphs, generally referred to as "type A" and "type B". These genital appendages are often preserved prominently in fossils and have been the subject of various interpretations of eurypterid reproduction and sexual dimorphism. Type A appendages are generally longer than those of type B. In some genera they are divided into different numbers of sections, such as in Eurypterus where

3381-495: Is a lightweight build. Factors such as locomotion, energy costs in molting and respiration, as well as the actual physical properties of the exoskeleton , limit the size that arthropods can reach. A lightweight construction significantly decreases the influence of these factors. Pterygotids were particularly lightweight, with most fossilized large body segments preserving as thin and unmineralized. Lightweight adaptations are present in other giant paleozoic arthropods as well, such as

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3542-523: Is also possible and the structure may represent the unfused tips of the appendages. Located between the dorsal and ventral surfaces of the Blattfüsse associated with the type A appendages is a set of organs traditionally described as either "tubular organs" or "horn organs". These organs are most often interpreted as spermathecae (organs for storing sperm ), though this function is yet to be proven conclusively. In arthropods, spermathecae are used to store

3703-490: Is an incomplete chelicerae, PE5105, that remains housed at the Chicago Natural History Museum alongside the paratype specimens. The species can be differentiated from other species of Pterygotus primarily by features of its cheliceral teeth, differing from P. barrandei and P. cobbi in these teeth being less-developed and thicker in P. carmani as well as the teeth having a markedly different arrangement on

3864-755: Is based on the nine best-known pterygotid species and two outgroup taxa ( Slimonia acuminata and Hughmilleria socialis ). The cladogram also contains the maximum sizes reached by the species in question, which have been suggested to possibly have been an evolutionary trait of the group per Cope's rule ("phyletic gigantism"). Hughmilleria socialis (20 cm) Slimonia acuminata (100 cm) Ciurcopterus ventricosus (70 cm) Erettopterus waylandsmithi (60 cm) Erettopterus osiliensis (90 cm) Erettopterus serricaudatus (60 cm) Erettopterus bilobus (70 cm) Pterygotus anglicus (160 cm) Jaekelopterus rhenaniae (250 cm) Eurypterid Eurypterids , often informally called sea scorpions , are

4025-539: Is classified as part of the pterygotid family of eurypterids, to which it lends its name, a group of highly derived eurypterids of the Silurian to Devonian periods that differ from other groups by a number of features, perhaps most prominently in the chelicerae (the first pair of limbs) and the telson (the posteriormost division of the body). The chelicerae of the Pterygotidae were enlarged and robust , clearly adapted to be used for active prey capture and more similar to

4186-418: Is classified within the family Pterygotidae in the superfamily Pterygotioidea , lending its name to both its family and its superfamily. The three most derived pterygotid eurypterids, Acutiramus , Jaekelopterus and Pterygotus , are very similar to each other. Pterygotus is particularly similar to Jaekelopterus , from which it is virtually only distinct in features of the genital appendage and potentially

4347-406: Is effectively a composite composed of fossils of three different eurypterids. These fossils consist of a type specimen of chelicerae (which is now lost, complicating any potential comparisons), a large carapace and chelicerae (likely actually referrable to Pterygotus due to being similar to P. anglicus ), a leg (undoubtedly representing a carcinosomatid eurypterid, potentially Carcinosoma ) and

4508-549: Is known from a single specimen (No. 48393 of the British Museum of Natural History) includes about half of the anterior end of what is presumed to be a fixed ramus of a chelicera. The claw is stout, with unusually short teeth that are faintly ribbed. This partial ramus measures 1.4 cm (0.5 in) in length and was discovered at Whitcliffe in Shropshire, England associated with fossils of brachiopods and cephalopods. Though it

4669-483: Is located behind the Blattfüssen . Instead, among arthropod respiratory organs, the eurypterid gill tracts most closely resemble the pseudotracheae found in modern isopods . These organs, called pseudotracheae, because of some resemblance to the tracheae (windpipes) of air-breathing organisms, are lung-like and present within the pleopods (back legs) of isopods. The structure of the pseudotracheae has been compared to

4830-487: Is made up of the first six exoskeleton segments fused together into a larger structure. The seventh segment (thus the first opisthosomal segment) is referred to as the metastoma and the eighth segment (distinctly plate-like) is called the operculum and contains the genital aperature. The underside of this segment is occupied by the genital operculum, a structure originally evolved from ancestral seventh and eighth pair of appendages. In its center, as in modern horseshoe crabs,

4991-517: Is more likely that the anus was opened through the thin cuticle between the last segment before the telson and the telson itself, as in modern horseshoe crabs. Eurypterid coprolites discovered in deposits of Ordovician age in Ohio containing fragments of a trilobite and eurypterid Megalograptus ohioensis in association with full specimens of the same eurypterid species have been suggested to represent evidence of cannibalism . Similar coprolites referred to

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5152-537: Is much more of a marine influence in many of the sections yielding Adelophthalmus than has previously been acknowledged." Similarly, a study of the eurypterid Hibbertopterus from the Carboniferous of New Mexico concluded that the habitat of some eurypterids "may need to be re-evaluated". The sole surviving eurypterine family, Adelophthalmidae, was represented by only a single genus, Adelophthalmus . The hibbertopterids, mycteroptids and Adelophthalmus survived into

5313-625: Is possible that many eurypterid species thought to be distinct actually represent juvenile specimens of other species, with paleontologists rarely considering the influence of ontogeny when describing new species. Studies on a well-preserved fossil assemblage of eurypterids from the Pragian -aged Beartooth Butte Formation in Cottonwood Canyon , Wyoming , composed of multiple specimens of various developmental stages of eurypterids Jaekelopterus and Strobilopterus , revealed that eurypterid ontogeny

5474-470: Is referred to as the metastoma, originally derived from a complete exoskeleton segment. The opisthosoma itself can be divided either into a " mesosoma " (comprising segments 1 to 6) and " metasoma " (comprising segments 7 to 12) or into a "preabdomen" (generally comprising segments 1 to 7) and "postabdomen" (generally comprising segments 8 to 12). The underside of the opisthosoma was covered in structures evolved from modified opisthosomal appendages. Throughout

5635-494: Is seen in the type species of Pterygotus , P. anglicus , and was noted to in fact be more similar to what is seen in P. buffaloensis and P. bohemicus . Today P. buffaloensis is considered a junior synonym of P. bohemicus , which has been reclassified as part of the closely related genus Acutiramus . The fragmentary remains of P. nobilis makes further studies of its precise identity difficult, Semper suggested that it may be synonymous with Acutiramus bohemicus , but noted that

5796-410: Is sometimes considered synonymous with P. lightbodyi , P. denticulatus can be distinguished by the small, thick and curved teeth of its claws, differing not only from P. lightbodyi in this respect, but virtually all other species of Pterygotus as well. P. lightbodyi is named in honor of Robert Lightbody , a British amateur geologist who made valuable contributions to paleontological research on

5957-445: Is sometimes used as a distinguishing feature, though the telsons of the three derived pterygotid genera are all paddle-shaped (the telson of Jaekelopterus is triangular, but might fall into the morphological range of the other genera). An inclusive phylogenetic analysis with multiple species of Acutiramus , Pterygotus and Jaekelopterus is required to resolve whether or not the genera are synonyms of each other. The cladogram below

6118-439: Is the first record of land locomotion by a eurypterid. The trackway provides evidence that some eurypterids could survive in terrestrial environments, at least for short periods of time, and reveals information about the stylonurine gait. In Hibbertopterus , as in most eurypterids, the pairs of appendages are different in size (referred to as a heteropodous limb condition). These differently sized pairs would have moved in phase, and

6279-795: Is the metastoma becoming proportionally less wide. This ontogenetic change has been observed in members of several superfamilies, such as the Eurypteroidea, the Pterygotioidea and the Moselopteroidea . No fossil gut contents from eurypterids are known, so direct evidence of their diet is lacking. The eurypterid biology is particularly suggestive of a carnivorous lifestyle. Not only were many large (in general, most predators tend to be larger than their prey), but they had stereoscopic vision (the ability to perceive depth). The legs of many eurypterids were covered in thin spines, used both for locomotion and

6440-410: Is the name-bearing type of a nominal genus or subgenus. The type species permanently attaches a formal name (the generic name) to a genus by providing just one species within that genus to which the genus name is permanently linked (i.e. the genus must include that species if it is to bear the name). The species name in turn is fixed, in theory, to a type specimen. For example, the type species for

6601-465: Is to other pterygotid species discovered in the P. cobbi locality (such as Acutiramus macrophthalmus ). By 1859, 10 species had been assigned to the genus, and John William Salter recognized that it was possible to divide these species into subgenera based on the morphology of the telsons. Salter erected the subgenus Pterygotus ( Erettopterus ) for species with a bilobed telson. Further subgenera would be named as more differences were noted between

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6762-418: Is unlikely the "gill tract" contained functional gills when comparing the organ to gills in other invertebrates and even fish. Previous interpretations often identified the eurypterid "gills" as homologous with those of other groups (hence the terminology), with gas exchange occurring within the spongy tract and a pattern of branchio-cardiac and dendritic veins (as in related groups) carrying oxygenated blood into

6923-423: Is unusually large in this species. The terminal tooth measures 2.3 cm (1 in) in length. The rami of P. impacatus are ornamented with large and pointed pustules (elevations in the skin), and this feature helps distinguish specimens of P. impacatus from other pterygotids in the fossil sites where its remains are found. In 2007, O. Erik Tetlie cast doubt on the assignment of P. impacatus to Pterygotus as

7084-526: The Ancient Greek words εὐρύς ( eurús ), meaning 'broad' or 'wide', and πτερόν ( pterón ), meaning 'wing', referring to the pair of wide swimming appendages present in many members of the group. The eurypterid order includes the largest known arthropods ever to have lived. The largest, Jaekelopterus , reached 2.5 meters (8.2 ft) in length. Eurypterids were not uniformly large and most species were less than 20 centimeters (8 in) long;

7245-636: The Erettopterus that it was found associated with, including the more robust chelicerae of P. lanarkensis . P. impacatus, recovered from deposits of Ludlow age at Kielkond in Saaremaa , Estonia, is represented by a holotype specimen consisting of a fragmentary free ramus of a chelicera that preserves some diagnostic and well-preserved details (specimen number 7059/7 housed in the Museum of Comparative Zoology ). Alongside this specimen, important specimens referred to

7406-439: The P. carmani remains were found, P. carmani is primarily known from incomplete chelicerae and gnathobases of coxae. Alongside the two coxae and three chelicerae part of its original description, known fossil remains also include a metastoma and a pretelson. All of these original fossil specimens were designated by Kjellesvig-Waering as paratype specimens upon the original description of the species. The designated type specimen

7567-520: The Permian–Triassic extinction event (or sometime shortly before) 251.9   million years ago. Although popularly called "sea scorpions", only the earliest eurypterids were marine ; many later forms lived in brackish or fresh water , and they were not true scorpions . Some studies suggest that a dual respiratory system was present, which would have allowed for short periods of time in terrestrial environments. The name Eurypterida comes from

7728-575: The Pterygotioidea , the Hibbertopteridae and the Mycteroptidae , the telson was flattened and may have been used as a rudder while swimming. Some genera within the superfamily Carcinosomatoidea , notably Eusarcana , had a telson similar to that of modern scorpions and may have been capable of using it to inject venom . The coxae of the sixth pair of appendages were overlaid by a plate that

7889-521: The Stylonuroidea , Kokomopteroidea and Mycteropoidea as well as eurypterine groups such as the Pterygotioidea, Eurypteroidea and Waeringopteroidea . The most successful eurypterid by far was the Middle to Late Silurian Eurypterus , a generalist , equally likely to have engaged in predation or scavenging . Thought to have hunted mainly small and soft-bodied invertebrates, such as worms , species of

8050-407: The claws of some modern crustaceans , with well developed teeth on the claws, than to the chelicerae of other eurypterid groups. Unlike most of the rest of the body, which was covered in a scale-like ornamentation like other pterygotid eurypterids, the claws lacked any type of ornamentation. Additionally, the end points of the claws were round and curved unlike the sharp points present at the ends of

8211-457: The land snail genus Monacha is Helix cartusiana , the name under which the species was first described, known as Monacha cartusiana when placed in the genus Monacha . That genus is currently placed within the family Hygromiidae . The type genus for that family is the genus Hygromia . The concept of the type species in zoology was introduced by Pierre André Latreille . The International Code of Zoological Nomenclature states that

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8372-442: The rhizodonts , were the new apex predators in marine environments. However, various recent findings raise doubts about this, and suggest that these eurypterids were euryhaline forms that lived in marginal marine environments, such as estuaries, deltas, lagoons, and coastal ponds. One argument is paleobiogeographical; pterygotoid distribution seems to require oceanic dispersal. A recent review of Adelophthalmoidea admitted that "There

8533-405: The spermatophore received from males. This would imply that the type A appendage is the female morph and the type B appendage is the male. Further evidence for the type A appendages representing the female morph of genital appendages comes in their more complex construction (a general trend for female arthropod genitalia). It is possible that the greater length of the type A appendage means that it

8694-406: The type species , grew to 1.6 metres (5.2 ft) in length, based on a large tergite discovered by Henry Woodward at some point between 1866 and 1878. Measuring just over 40 centimetres (16 in) in length and 10.5 centimetres (4.1 in) in width, the tergite suggests a eurypterid with a full length of 1.6 metres (5.2 ft) from the beginning of the carapace to the end of the telson, if

8855-478: The "peculiar hook-like termination of the ramus", a feature now known to be present due to a remnant of the free ramus being present in the fossil. The tooth pattern and shape of the claw suggests that an assignment to Pterygotus is more likely. P. siemiradzkii , described by Embrik Strand in 1926 based on fossil material from western Ukraine , is based on highly fragmentary material with little diagnostic value. The single specimen designated as P. siemiradzkii ,

9016-558: The "questions [about its identity] can not be answered from the material available to me". Another species, P. kopaninensis , also named in 1872, is known from a single and incomplete fixed cheliceral ramus (specimen number L1396) recovered from the Kopanina Formation around the village of Zadní Kopanina , located in Prague . The specimen measures 4.3 cm (1.7 in) in length and was at one point assigned to Erettopterus due to

9177-570: The 20th century would help establish that Pterygotus as a genus achieved a nearly cosmopolitan distribution . The first eurypterid to be discovered in Australia was Pterygotus australis , whose fossils were found in the Ludlow age Melbourne Group of the Dargile Formation . The fossils referred to P. australis , consisting of four fragments making up about half of a segment that were discovered during

9338-527: The Devonian, large two meter (6.5+ ft) pterygotids such as Acutiramus were already present during the Late Silurian. Their ecology ranged from generalized predatory behavior to ambush predation and some, such as Pterygotus itself, were active apex predators in Late Silurian marine ecosystems. The pterygotids were also evidently capable of crossing oceans, becoming one of only two eurypterid groups to achieve

9499-856: The Early Devonian P. carmani (1961, USA) and P. floridanus (1950, Florida, USA) and the Middle Devonian P. gaspesiensis (1953, Quebec , Canada). Fossil remains of pterygotid eurypterids, bearing the distinct scale-like ornamentation known from the group, had been reported from eastern Canada as early as 1846, when researcher William Edmond Logan reported the occurrence of an animal "bearing strong resemblance to Murchison's Pterygotus problematicus " in Silurian-Devonian deposits of Gaspé, Quebec . The fossils, eventually identified as being exclusively of Devonian age, were first tentatively referred to P. atlanticus (now synonymized with P. anglicus ), which had been discovered in relatively close proximity to

9660-563: The Gaspé fossils, on the account of the P. atlanticus material being so fragmentary that it was impossible to tell whether or not they represented the same species. They were described by Loris S. Russell as belonging to the new species P. gaspesiensis in 1953. John William Dawson in 1861 named a new species of lycopod plant, Selaginites formosus , based on alleged remains of stems and branches found at Gaspé. Salter convinced Dawson that fossils of S. formosus actually were fragmentary remains of

9821-487: The Geological Survey and Museum of London, a free ramus of a chelicera) might truly be referrable to this distinct species as the other fossils (tergites, coxae and indeterminable fragments) might actually represent fossils of other species due to not being diagnostic enough. P. ludensis , described by Salter in 1859, can be distinguished from other species by the more developed and prolonged keel (or ridge) running along

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9982-804: The Middle Ordovician suggests that eurypterids either originated during the Early Ordovician and experienced a rapid and explosive radiation and diversification soon after the first forms evolved, or that the group originated much earlier, perhaps during the Cambrian period. As such, the exact eurypterid time of origin remains unknown. Though fossils referred to as "primitive eurypterids" have occasionally been described from deposits of Cambrian or even Precambrian age, they are not recognized as eurypterids, and sometimes not even as related forms, today. Some animals previously seen as primitive eurypterids, such as

10143-590: The Middle Ordovician, 467.3 million years ago . There are also reports of even earlier fossil eurypterids in the Fezouata Biota of Late Tremadocian (Early Ordovician) age in Morocco , but these have yet to be thoroughly studied, and are likely to be peytoiid appendages. Pentecopterus was a relatively derived eurypterid, part of the megalograptid family within the carcinosomatoid superfamily. Its derived position suggests that most eurypterid clades, at least within

10304-590: The Middle Silurian and the Early Devonian, with an absolute peak in diversity during the Pridoli epoch , 423 to 419.2 million years ago, of the very latest Silurian. This peak in diversity has been recognized since the early twentieth century; of the approximately 150 species of eurypterids known in 1916, more than half were from the Silurian and a third were from the Late Silurian alone. Though stylonurine eurypterids generally remained rare and low in number, as had been

10465-536: The Ordovician, eurypterids became major components of marine faunas during the Silurian , from which the majority of eurypterid species have been described. The Silurian genus Eurypterus accounts for more than 90% of all known eurypterid specimens. Though the group continued to diversify during the subsequent Devonian period, the eurypterids were heavily affected by the Late Devonian extinction event . They declined in numbers and diversity until becoming extinct during

10626-485: The Permian. Type species In botanical nomenclature , these terms have no formal standing under the code of nomenclature , but are sometimes borrowed from zoological nomenclature. In botany, the type of a genus name is a specimen (or, rarely, an illustration) which is also the type of a species name. The species name with that type can also be referred to as the type of the genus name. Names of genus and family ranks,

10787-494: The Pterygotidae, is noted for several unusually large species. Both Acutiramus , whose largest member A. bohemicus measured 2.1 meters (6.9 ft), and Pterygotus , whose largest species P. grandidentatus measured 1.75 meters (5.7 ft), were gigantic. Several different contributing factors to the large size of the pterygotids have been suggested, including courtship behaviour, predation and competition over environmental resources. Giant eurypterids were not limited to

10948-586: The Stylonurina, this appendage takes the form of a long and slender walking leg, while in the Eurypterina, the leg is modified and broadened into a swimming paddle. Other than the swimming paddle, the legs of many eurypterines were far too small to do much more than allow them to crawl across the sea floor . In contrast, a number of stylonurines had elongated and powerful legs that might have allowed them to walk on land (similar to modern crabs ). A fossil trackway

11109-538: The abundance and diversity previously seen within the eurypterids. A major decline in diversity had already begun during the Early Devonian and eurypterids were rare in marine environments by the Late Devonian. During the Frasnian stage four families went extinct, and the later Famennian saw an additional five families going extinct. As marine groups were the most affected, the eurypterids were primarily impacted within

11270-530: The ancient continent of Laurentia , and demersal (living on the seafloor ) and basal animals from the continents Avalonia and Gondwana. The Laurentian predators, classified in the family Megalograptidae (comprising the genera Echinognathus , Megalograptus and Pentecopterus ), are likely to represent the first truly successful eurypterid group, experiencing a small radiation during the Late Ordovician. Eurypterids were most diverse and abundant between

11431-442: The animal in question could possibly have measured just short of 2 meters (6.6 ft) in length. More robust than the pterygotids, this giant Hibbertopterus would possibly have rivalled the largest pterygotids in weight, if not surpassed them, and as such be among the heaviest arthropods. The two eurypterid suborders, Eurypterina and Stylonurina , are distinguished primarily by the morphology of their final pair of appendages. In

11592-454: The appendage via tracts, but these supposed tracts remain unpreserved in available fossil material. Type B appendages, assumed male, would have produced, stored and perhaps shaped spermatophore in a heart-shaped structure on the dorsal surface of the appendage. A broad genital opening would have allowed large amounts of spermatophore to be released at once. The long furca associated with type B appendages, perhaps capable of being lowered like

11753-530: The arrangement of the smaller teeth of the claws and from P. barrandei in that P. floridanus has a more slender ramus. P. carmani is the most commonly found eurypterid in the Lower Devonian deposits of Lucas County, Ohio . Described by Erik N. Kjellesvig-Waering in 1961 and named in honor of Dr. J. Ernest Carman of the Ohio State University, the first to discover eurypterids at the locality where

11914-414: The body. The primary analogy used in previous studies has been horseshoe crabs, though their gill structure and that of eurypterids are remarkably different. In horseshoe crabs, the gills are more complex and composed of many lamellae (plates) which give a larger surface area used for gas exchange. In addition, the gill tract of eurypterids is proportionally much too small to support them if it is analogous to

12075-458: The case during the preceding Ordovician, eurypterine eurypterids experienced a rapid rise in diversity and number. In most Silurian fossil beds, eurypterine eurypterids account for 90% of all eurypterids present. Though some were likely already present by the Late Ordovician (simply missing from the fossil record so far), a vast majority of eurypterid groups are first recorded in strata of Silurian age. These include both stylonurine groups such as

12236-570: The center of the telson from its beginning to the tail spike. The rare species P. cobbi , described by James Hall in 1859 based on fossils recovered in New York, USA, was the first species of Pterygotus to be described from outside of Scotland and expanded the known range of the genus considerably. Hall described this new species alongside two other North American species; P. macrophthalmus (now referred to Acutiramus ) and P. osborni (later synonymized with P. macrophthalmus ). The distal tooth of

12397-605: The claw. P. marylandicus , from deposits of Ludfordian (Late Silurian) age, is known from a fragmentary and small telson from the McKenzie Formation , Maryland first described by Kjellesvig-Waering in 1964, who recognized it as a telson of a Pterygotus . The specimen (No. 140901 at the United States National Museum ) is very wide, 0.75 cm, and has a nearly straight base with the margins converging anteriorly. Unlike some species, there are no serrations on

12558-465: The claws of the related Erettopterus . The pterygotid telsons were flattened and expanded, likely used as rudders when swimming. Their walking legs were small and slender, without spines, and they were likely not capable of walking on land. Pterygotus is distinguishable from other pterygotids by the curved distal margin of the chelae (claws). The prosoma (head) is subtrapezoidal (a trapezoid with rounded corners), with compound eyes located near

12719-420: The coastlines and shallow inland seas of Euramerica. During the Late Silurian the pterygotid eurypterids, large and specialized forms with several new adaptations, such as large and flattened telsons capable of being used as rudders, and large and specialized chelicerae with enlarged pincers for handling (and potentially in some cases killing) prey appeared. Though the largest members of the family appeared in

12880-577: The continent, with New York State representing the most fossil-rich state. The remains of P. floridanus were first uncovered by G. Arthur Cooper in Suwannee County, Florida , and the fossils consist of a fixed ramus of the chelicera as well as fragments of the abdominal plates and tergites and were concluded to represent a new species of Pterygotus by Erik N. Kjellesvig-Waering in 1950. It most closely resembles P. cobbi and P. barrandei , differing from P. cobbi in its more developed central tooth and

13041-695: The cuticle) after which they underwent rapid and immediate growth. Some arthropods, such as insects and many crustaceans, undergo extreme changes over the course of maturing. Chelicerates, including eurypterids, are in general considered to be direct developers, undergoing no extreme changes after hatching (though extra body segments and extra limbs may be gained over the course of ontogeny in some lineages, such as xiphosurans and sea spiders ). Whether eurypterids were true direct developers (with hatchlings more or less being identical to adults) or hemianamorphic direct developers (with extra segments and limbs potentially being added during ontogeny) has been controversial in

13202-594: The early Paleozoic of the Welsh Borderland , including the discovery of important Silurian fossils (such as eurypterids), in the 1800s. This species was one of the most common eurypterid in England during the Ludlow epoch and was quite large and clearly distinct (though it resembles P. barrandei , P. floridanus and P. cobbi in its cheliceral morphology) from other species of the genus, being known from multiple specimens. The most important fossils of P. lightbodyi include

13363-410: The edge of the front corners. The telson has a pronounced dorsal carina (or keel) running down its center, terminating in a short spine. The Pterygotidae includes the largest known arthropods to have ever lived, with several species surpassing two metres in length (such as Jaekelopterus rhenaniae at 2.5 metres (8.2 ft) and Acutiramus bohemicus at 2.1 metres (6.9 ft)). Though Pterygotus

13524-409: The eurypterine suborder, had already been established at this point during the Middle Ordovician. The earliest known stylonurine eurypterid, Brachyopterus , is also Middle Ordovician in age. The presence of members of both suborders indicates that primitive stem-eurypterids would have preceded them, though these are so far unknown in the fossil record. The presence of several eurypterid clades during

13685-411: The eurypterine suborder. Only one group of stylonurines (the family Parastylonuridae ) went extinct in the Early Devonian. Only two families of eurypterines survived into the Late Devonian at all ( Adelophthalmidae and Waeringopteridae). The eurypterines experienced their most major declines in the Early Devonian, during which over 50% of their diversity was lost in just 10 million years. Stylonurines, on

13846-508: The eurypterine swimming paddles varied from group to group. In the Eurypteroidea , the paddles were similar in shape to oars. The condition of the joints in their appendages ensured their paddles could only be moved in near-horizontal planes, not upwards or downwards. Some other groups, such as the Pterygotioidea, would not have possessed this condition and were probably able to swim faster. Most eurypterines are generally agreed to have utilized

14007-613: The extended chelicerae are counted (normally they are not) the total length would exceed 2 metres (6.6 ft). P. carmani , from the Devonian of Ohio , likely reached lengths in excess of 1.5 metres (4.9 ft). The species P. cobbi (1.4 metres (4.6 ft)), P. barrandei (1.26 metres (4.1 ft)) and P. denticulatus (1.2 metres (3.9 ft)) also exceeded 1 metre in length. Smaller species include P. floridanus at 90 centimetres (35 in), P. lightbodyi at 75 centimetres (30 in), P. arcuatus at 60 centimetres (24 in), P. bolivianus at 55 centimetres (22 in) and

14168-432: The eyes suggest an assignation to the genus Pterygotus , differing from P. monroensis in being nearly rectangular in shape and with a straight transverse frontal margin. He suggested a relationship with Slimonia , but he did not assigned it due to the lack of more material indicative of the latter. Although it was later placed on the genus Waeringopterus , Samuel J. Ciurca, Jr. and O. Erik Tetlie concluded in 2007 that

14329-561: The family Pterygotidae was erected by John Mason Clarke & Rudolf Ruedemann in 1912 to include the eurypterid genera Pterygotus , Slimonia , Hughmilleria and Hastimima . The three latter genera would be reclassified as members of the Hughmilleriidae by Erik N. Kjellesvig-Waering in 1951, leaving Pterygotus and its former subgenera as the sole pterygotid eurypterids. Though early discoveries of Pterygotus were confined to England and North America, fossil finds throughout

14490-454: The family Pterygotidae. An isolated 12.7 centimeters (5.0 in) long fossil metastoma of the carcinosomatoid eurypterid Carcinosoma punctatum indicates the animal would have reached a length of 2.2 meters (7.2 ft) in life, rivalling the pterygotids in size. Another giant was Pentecopterus decorahensis , a primitive carcinosomatoid, which is estimated to have reached lengths of 1.7 meters (5.6 ft). Typical of large eurypterids

14651-465: The fossil remains of a large fish. The specimens described by Agassiz from England were referred to a species he dubbed Pterygotus problematicus . Agassiz first recognized the true nature of the fossils as arthropod remains five years later in 1844 after having examined more complete fossils recovered in the Old Red Sandstone of Scotland. Although recognizing the fossils of Pterygotus as arthropod

14812-476: The found tracks each being about 7.6 centimeters (3.0 in) in diameter. Other eurypterid ichnogenera include Merostomichnites (though it is likely that many specimens actually represent trackways of crustaceans) and Arcuites (which preserves grooves made by the swimming appendages). In eurypterids, the respiratory organs were located on the ventral body wall (the underside of the opisthosoma). Blattfüsse , evolved from opisthosomal appendages, covered

14973-494: The free ramus (the part of the claw that moves) was less prominent than in other species, which has been noted as similar to the distal tooth in the free ramus of Acutiramus cummingsi . Although P. cobbi is based on poor fossil material, only known from a free ramus, it remains recognized as a distinct species on the account of being more similar to certain species discovered in the Czech Republic (such as P. barrandei ) than it

15134-493: The free ramus of P. barrandei is significantly longer than the corresponding tooth in P. cobbi and the teeth of the free ramus of P. barrandei are directed forwards more prominently in general. Fossils of P. barrandei are rare, with fossil finds being confined to a handful of formations of Pridoli age in Bohemia . Known fossils include some incomplete chelicerae and a metastoma. Some additional fossil remains have been assigned to

15295-568: The gathering of food. In some groups, these spiny appendages became heavily specialized. In some eurypterids in the Carcinosomatoidea, forward-facing appendages were large and possessed enormously elongated spines (as in Mixopterus and Megalograptus ). In derived members of the Pterygotioidea, the appendages were completely without spines, but had specialized claws instead. Other eurypterids, lacking these specialized appendages, likely fed in

15456-651: The genus Strabops from the Cambrian of Missouri , are now classified as aglaspidids or strabopids . The aglaspidids, once seen as primitive chelicerates, are now seen as a group more closely related to trilobites. The fossil record of Ordovician eurypterids is quite poor. The majority of eurypterids once reportedly known from the Ordovician have since proven to be misidentifications or pseudofossils . Today only 11 species can be confidently identified as representing Ordovician eurypterids. These taxa fall into two distinct ecological categories; large and active predators from

15617-463: The genus (of which the most common is the type species, E. remipes ) account for more than 90% (perhaps as many as 95%) of all known fossil eurypterid specimens. Despite their vast number, Eurypterus are only known from a relatively short temporal range, first appearing during the Late Llandovery epoch (around 432 million years ago) and being extinct by the end of the Pridoli epoch. Eurypterus

15778-429: The giant millipede Arthropleura , and are possibly vital for the evolution of giant size in arthropods. In addition to the lightweight giant eurypterids, some deep-bodied forms in the family Hibbertopteridae were also very large. A carapace from the Carboniferous of Scotland referred to the species Hibbertoperus scouleri measures 65 cm (26 in) wide. As Hibbertopterus was very wide compared to its length,

15939-412: The gills of other groups. To be functional gills, they would have to have been highly efficient and would have required a highly efficient circulatory system. It is considered unlikely, however, that these factors would be enough to explain the large discrepancy between gill tract size and body size. It has been suggested instead that the "gill tract" was an organ for breathing air, perhaps actually being

16100-404: The holotype (consisting of most of a chelicera) and two paratypes (including most of the free ramus). The claws of P. lightbodyi are all equipped with vertically placed and very long teeth, most of which curve slightly backwards. The terminal tooth is unusually slender and long in P. lightbodyi , and as with the other teeth slightly curved backwards. Among the more important diagnostic features of

16261-461: The holotype does not really have eyes and is nothing more than an incomplete body segment. Therefore, they regarded the species as a nomen dubium . P. floridanus , recovered from deposits of Lochkovian age in Florida, extended the known range of eurypterids on the continent over 800 km (500 miles) south. Prior to its discovery, eurypterids in North America were only known from the northern parts of

16422-580: The invaginations leading to asphyxiation . Furthermore, most eurypterids would have been aquatic their entire lives. No matter how much time was spent on land, organs for respiration in underwater environments must have been present. True gills, expected to have been located within the branchial chamber within the Blattfüssen , remain unknown in eurypterids. Like all arthropods, eurypterids matured and grew through static developmental stages referred to as instars . These instars were punctuated by periods during which eurypterids went through ecdysis (molting of

16583-491: The larger sizes of adults mean a higher drag coefficient , using this type of propulsion is more energy-efficient. Some eurypterines, such as Mixopterus (as inferred from attributed fossil trackways), were not necessarily good swimmers. It likely kept mostly to the bottom, using its swimming paddles for occasional bursts of movements vertically, with the fourth and fifth pairs of appendages positioned backwards to produce minor movement forwards. While walking, it probably used

16744-495: The largest known arthropod ever to have lived, is Jaekelopterus rhenaniae . A chelicera from the Emsian Klerf Formation of Willwerath, Germany measured 36.4 centimeters (14.3 in) in length, but is missing a quarter of its length, suggesting that the full chelicera would have been 45.5 centimeters (17.9 in) long. If the proportions between body length and chelicerae match those of its closest relatives, where

16905-471: The largest known species, P. grandidentatus , reached a body length of 1.75 metres (5.7 ft). Several other species, notably P. impacatus at 1.65 metres (5.4 ft) and P. anglicus at 1.6 metres (5.2 ft) were similarly gigantic. Pterygotus was surpassed in size by other giant eurypterids. Acutiramus was able to surpass 2 metres (6.6 ft), and Jaekelopterus could reach 2.6 metres (8.5 ft). Many species were considerably smaller than

17066-470: The largest species, P. grandidentatus , reaching a body length of 1.75 metres (5.7 ft), Pterygotus was among the largest known eurypterids to have existed, though some of its close relatives (such as Acutiramus and Jaekelopterus ) surpassed it in length. Though there were a few gigantic species, many species were considerably smaller in size. The smallest species, P. kopaninensis , measured just 50 centimetres (20 in) in length. Pterygotus

17227-423: The largest species, such as P. kopaninensis at 50 centimetres (20 in). Pterygotus may have weighed around 30 kilogramms. Like its close relative Jaekelopterus , Pterygotus was a large and active predator noted for its robust and enlarged cheliceral claws that would have allowed it to puncture and grasp prey and a visual acuity (clarity of vision) comparable to that of modern predatory arthropods. With

17388-497: The last ever radiation within the eurypterids, which gave rise to several new forms capable of "sweep-feeding" (raking through the substrate in search of prey). Only three eurypterid families—Adelophthalmidae, Hibbertopteridae and Mycteroptidae—survived the extinction event in its entirety. It was assumed that these were all freshwater animals, which would have rendered the eurypterids extinct in marine environments, and with marine eurypterid predators gone, sarcopterygians , such as

17549-486: The limbs tended to get larger the farther back they were. In the Eurypterina suborder , the larger of the two eurypterid suborders, the sixth pair of appendages was also modified into a swimming paddle to aid in traversing aquatic environments. The opisthosoma comprised 12 segments and the telson , the posteriormost division of the body, which in most species took the form of a blade-like shape. In some lineages, notably

17710-474: The most extensively known species of Pterygotus , distinguished from subsequently discovered species by possessing curved terminal teeth and the primary and intermediate teeth being inclined slightly backwards. P. problematicus was also used as the designation for an incomplete chelicera discovered in the Welsh Borderland of western England by John William Salter in 1852 but is in modern times considered

17871-488: The mouth. In one lineage, the Pterygotidae , the chelicerae were large and long, with strong, well-developed teeth on specialised chelae (claws). The subsequent pairs of appendages, numbers II to VI, possessed gnathobases (or "tooth-plates") on the coxae (limb segments) used for feeding. These appendages were generally walking legs that were cylindrical in shape and were covered in spines in some species. In most lineages,

18032-439: The name is no longer in use. Instead P. anglicus , based on a number of diagnostic features and properly illustrated in its description by Agassiz in 1844, is considered the type species of Pterygotus . Two further species that remain assigned to the genus to this day would be described from England during the 19th century; P. ludensis of Pridoli (Late Silurian) age and P. arcuatus of Ludlow (Late Silurian) age, along with

18193-708: The opisthosoma, these structures formed plate-like structures termed Blattfüsse ( lit.   ' leaf-feet ' in German). These created a branchial chamber (gill tract) between preceding Blattfüsse and the ventral surface of the opisthosoma itself, which contained the respiratory organs. The second to sixth opisthosomal segments also contained oval or triangular organs that have been interpreted as organs that aid in respiration. These organs, termed Kiemenplatten or "gill tracts", would potentially have aided eurypterids to breathe air above water, while Blattfüssen , similar to organs in modern horseshoe crabs , would cover

18354-420: The original name (binomen) of the type species should always be cited. It gives an example in Article 67.1. Astacus marinus Fabricius, 1775 was later designated as the type species of the genus Homarus , thus giving it the name Homarus marinus (Fabricius, 1775) . However, the type species of Homarus should always be cited using its original name, i.e. Astacus marinus Fabricius, 1775 , even though that

18515-473: The original taxon to one of the resulting new taxa, the one that includes the type species. The term "type species" is regulated in zoological nomenclature by article 42.3 of the International Code of Zoological Nomenclature , which defines a type species as the name-bearing type of the name of a genus or subgenus (a " genus-group name "). In the Glossary, type species is defined as The nominal species that

18676-424: The other hand, persisted through the period with more or less consistent diversity and abundance but were affected during the Late Devonian, when many of the older groups were replaced by new forms in the families Mycteroptidae and Hibbertopteridae. It is possible that the catastrophic extinction patterns seen in the eurypterine suborder were related to the emergence of more derived fish. Eurypterine decline began at

18837-548: The parts that serve for underwater respiration . The appendages of opisthosomal segments 1 and 2 (the seventh and eighth segments overall) were fused into a structure termed the genital operculum, occupying most of the underside of the opisthosomal segment 2. Near the anterior margin of this structure, the genital appendage (also called the Zipfel or the median abdominal appendage) protruded. This appendage, often preserved very prominently, has consistently been interpreted as part of

18998-433: The past. Hemianamorphic direct development has been observed in many arthropod groups, such as trilobites , megacheirans , basal crustaceans and basal myriapods . True direct development has on occasion been referred to as a trait unique to arachnids . There have been few studies on eurypterid ontogeny as there is a general lack of specimens in the fossil record that can confidently be stated to represent juveniles. It

19159-434: The point when jawless fish first became more developed and coincides with the emergence of placoderms (armored fish) in both North America and Europe. Stylonurines of the surviving hibbertopterid and mycteroptid families completely avoided competition with fish by evolving towards a new and distinct ecological niche. These families experienced a radiation and diversification through the Late Devonian and Early Carboniferous,

19320-464: The process of excavations beneath Melbourne during the construction of new drainage works for the city in 1899. The fragmentary fossils closely resemble fossils of Erettopterus bilobus (classified as a species of Pterygotus at the time), which might make their assignment to Pterygotus questionable. In 2020, the species was marked as a nomen dubium (a dubious species) due to the lack of sufficient diagnostic material to separate P. australis from

19481-487: The pterygotid family. The specimen (PE6173, housed at the Chicago Natural History Museum ) includes the well-preserved anterior half of a chelicera and ramus. The tooth of the ramus are short, wide and conical, all being slightly curved backwards. The terminal tooth is larger, but only slightly, than the tooth succeeding it and the inwards bend of the claw suggests that another tooth might be present, creating

19642-407: The ramus is poorly known from other species of Pterygotus and P. waylandsmithi was reclassified as a species of Erettopterus in 2007 the assignment of P. grandidentatus to Pterygotus is questionable. England would also yield a dubious species, P. taurinus , from deposits of Pridoli or Devonian age. Named by Salter in 1868, P. taurinus is treated as a dubious species for the reason that it

19803-452: The ratio between claw size and body length is relatively consistent, the specimen of Jaekelopterus that possessed the chelicera in question would have measured between 233 and 259 centimeters (7.64 and 8.50 ft), an average 2.5 meters (8.2 ft), in length. With the chelicerae extended, another meter (3.28 ft) would be added to this length. This estimate exceeds the maximum body size of all other known giant arthropods by almost half

19964-445: The reproduction and sexual dimorphism of eurypterids is difficult, as they are only known from fossilized shells and carapaces. In some cases, there might not be enough apparent differences to separate the sexes based on morphology alone. Sometimes two sexes of the same species have been interpreted as two different species, as was the case with two species of Drepanopterus ( D. bembycoides and D. lobatus ). The eurypterid prosoma

20125-458: The reproductive system and occurs in two recognized types, assumed to correspond to male and female. Eurypterids were highly variable in size, depending on factors such as lifestyle, living environment and taxonomic affinity . Sizes around 100 centimeters (3.3 ft) are common in most eurypterid groups. The smallest eurypterid, Alkenopterus burglahrensis , measured just 2.03 centimeters (0.80 in) in length. The largest eurypterid, and

20286-435: The rest of the former supercontinent Gondwana , the discoveries of trackways both predate and outnumber eurypterid body fossils. Eurypterid trackways have been referred to several ichnogenera, most notably Palmichnium (defined as a series of four tracks often with an associated drag mark in the mid-line), wherein the holotype of the ichnospecies P. kosinkiorum preserves the largest eurypterid footprints known to date with

20447-584: The rest of the pterygotids. Kjellesvig-Waering named the species P. bolivianus in 1964 based on fossils recovered from deposits of Emsian - Eifelian (Early to Middle Devonian) age in Bolivia. This species was the first pterygotid to be discovered in South America, the first Devonian pterygotid to be recovered in deposits in the Southern Hemisphere and also represents one of the last known living member of

20608-405: The same genera. The primary function of the long, assumed female, type A appendages was likely to take up spermatophore from the substrate into the reproductive tract rather than to serve as an ovipositor, as arthropod ovipositors are generally longer than eurypterid type A appendages. By rotating the sides of the operculum, it would have been possible to lower the appendage from the body. Due to

20769-409: The scale-like ornamentation characteristic of the group which researchers have wrongfully believed was characteristic of only Pterygotus or P. problematicus . As such ornamentation is known from every pterygotid genus it can not be used as a diagnostic feature of a single species. Though P. problematicus is the earliest name used for a species of Pterygotus , it is not considered the type species as

20930-424: The shape of the eyes and carapace was similar to how these body parts are shaped in Erettopterus . England, the site of the initial discovery of P. problematicus , has provided fossils for several additional species. Kjellesvig-Waering named three new species from England in 1961; P. denticulatus , P. lightbodyi (both Late Ludlow in age) and P. grandidentatus ( Wenlock , Late Silurian, in age). P. denticulatus

21091-413: The short stride length indicates that Hibbertopterus crawled with an exceptionally slow speed, at least on land. The large telson was dragged along the ground and left a large central groove behind the animal. Slopes in the tracks at random intervals suggest that the motion was jerky. The gait of smaller stylonurines, such as Parastylonurus , was probably faster and more precise. The functionality of

21252-472: The smallest eurypterid, Alkenopterus , was only 2.03 centimeters (0.80 in) long. Eurypterid fossils have been recovered from every continent. A majority of fossils are from fossil sites in North America and Europe because the group lived primarily in the waters around and within the ancient supercontinent of Euramerica . Only a handful of eurypterid groups spread beyond the confines of Euramerica and

21413-532: The smallest known species, P. kopaninensis , at 50 centimetres (20 in) in length. The first fossils of Pterygotus were found in deposits of Lochkovian - Pragian (Early Devonian) age by quarrymen in Scotland and western England, who referred to the large fossil remains as " Seraphims ". Louis Agassiz , a Swiss-American biologist and geologist, described the fossils in 1839 and named it Pterygotus , which translates to "winged one". Agassiz believed that they were

21574-441: The species Lanarkopterus dolichoschelus from the Ordovician of Ohio contain fragments of jawless fish and fragments of smaller specimens of Lanarkopterus itself. Though apex predatory roles would have been limited to the very largest eurypterids, smaller eurypterids were likely formidable predators in their own right just like their larger relatives. As in many other entirely extinct groups, understanding and researching

21735-400: The species include the paratype (No. 7059/3, a fragmentary chelicera). This specimen includes several of the features that are diagnostic of P. impacatus , such as upright teeth following the thick and long teeth of the terminal part of the claw. Particularly of diagnostic value is that there are teeth present at the point where the terminal teeth first begin. The central tooth of the free ramus

21896-537: The species is the combination of a large terminal tooth and a large upright tooth near it. P. grandidentatus is known from a single specimen, the anterior half of a free ramus of a chelicera discovered in the Wenlock -aged beds at Dudley in Worcestershire, England (specimen number I. 3163 in the British Museum of Natural History ). It is notable for the stout stem and the unusually long length (1.75 cm, 0.7 in) of

22057-414: The species, consisting of coxae and a genital appendage, but their assignment to the species is doubtful. The species P. nobilis , described in 1872, is based on a small and fragmentary chelicera found in what today is the Czech Republic . The arrangement of teeth seen in this claw, though most teeth are not preserved, was noted by researcher Max Semper in 1897 as sharing little to no resemblance with what

22218-504: The species, such subgenera include Pterygotus ( Curviramus ) and Pterygotus ( Acutiramus ), named in 1935 based upon features of the denticles (teeth) of the chelicerae. Pterygotus ( Curviramus ) was later recognized as synonymous with Pterygotus ( Pterygotus ) by Leif Størmer the same year, and Erettopterus and Acutiramus would be recognized as separate, but closely related, genera ( Erettopterus by Erik N. Kjellesvig-Waering in 1961, and Acutiramus by Størmer in 1974). In 1912,

22379-427: The spongy structure of the eurypterid gill tracts. It is possible the two organs functioned in the same way. Some researchers have suggested that eurypterids may have been adapted to an amphibious lifestyle, using the full gill tract structure as gills and the invaginations within it as pseudotrachea. This mode of life may not have been physiologically possible, however, since water pressure would have forced water into

22540-492: The structure. Though the Kiemenplatte is referred to as a "gill tract", it may not necessarily have functioned as actual gills. In other animals, gills are used for oxygen uptake from water and are outgrowths of the body wall. Despite eurypterids clearly being primarily aquatic animals that almost certainly evolved underwater (some eurypterids, such as the pterygotids, would even have been physically unable to walk on land), it

22701-530: The telson and the spine is blunt. The species is very distinct, being distinguishable from all other Silurian species of Pterygotus by the shape of its telson. A species of Jaekelopterus , J. howelli from the Early Devonian, is similar in the wide and truncated telson shape, but is easily distinguished by possessing serrations and a much larger terminal spine. The species P. monroensis , known from deposits of late Wenlock to Ludlow age in New York State, USA,

22862-462: The telson. Similarities in the genital appendage could mean that the three genera are all synonyms of each other, as they had been classified in the past (as species of Pterygotus ). Some differences between them have also been noted in the chelicerae, though chelicerae have been questioned as the basis of eurypterid generic distinction since their morphology depends on the lifestyles and has been observed to vary throughout ontogeny . Telson morphology

23023-416: The terminal tooth and the unusual thickness of its base. P. grandidentatus can easily be distinguished from other species not only be its unusual terminal tooth, but also by the disoriented teeth along the claw, being bent in a variety of different directions. The terminal part of the ramus ends in an arrangement of multiple teeth otherwise only noted in the species P. waylandsmithi . As this specific part of

23184-464: The type A appendage is divided into three but the type B appendage into only two. Such division of the genital appendage is common in eurypterids, but the number is not universal; for instance, the appendages of both types in the family Pterygotidae are undivided. The type A appendage is also armed with two curved spines called furca (lit. 'fork' in Latin). The presence of furca in the type B appendage

23345-414: The type A appendage, could have been used to detect whether a substrate was suitable for spermatophore deposition. Until 1882 no eurypterids were known from before the Silurian. Contemporary discoveries since the 1880s have expanded the knowledge of early eurypterids from the Ordovician period. The earliest eurypterids known today, the megalograptid Pentecopterus , date from the Darriwilian stage of

23506-400: The underside and created a gill chamber where the "gill tracts" were located. Depending on the species, the eurypterid gill tract was either triangular or oval in shape and was possibly raised into a cushion-like state. The surface of this gill tract bore several spinules (small spines), which resulted in an enlarged surface area. It was composed of spongy tissue due to many invaginations in

23667-409: The various subdivisions of those ranks, and some higher-rank names based on genus names, have such types. In bacteriology , a type species is assigned for each genus. Whether or not currently recognized as valid , every named genus or subgenus in zoology is theoretically associated with a type species. In practice, however, there is a backlog of untypified names defined in older publications when it

23828-429: The way different plates overlay at its location, the appendage would have been impossible to move without muscular contractions moving around the operculum. It would have been kept in place when not it use. The furca on the type A appendages may have aided in breaking open the spermatophore to release the free sperm inside for uptake. The "horn organs," possibly spermathecae, are thought to have been connected directly to

23989-472: The wide but short and evenly sized teeth as well as the terminal tooth not having any particular development. In 2019, a new fragmentary ramus of a chelicera was found in the Cuche Formation of Colombia . The specimen (SGC-MGJRG.2018.I.5), assigned with uncertainty to P. bolivianus due to similarities with its holotype, represents the first eurypterid of Colombia and the fourth of South America. The fossil

24150-400: Was also restricted to the continent Euramerica (composed of the equatorial continents Avalonia, Baltica and Laurentia), which had been completely colonized by the genus during its merging and was unable to cross the vast expanses of ocean separating this continent from other parts of the world, such as the southern supercontinent Gondwana. As such, Eurypterus was limited geographically to

24311-411: Was classified as the separate genus Ciurcopterus in 2007 by O. Erik Tetlie and Derek E. G. Briggs, distinguished primarily by sharing several features with more basal pterygotioid eurypterids, such as its appendages being similar to those of Slimonia . New fossil finds also revealed the presence of Pterygotus in several European countries where it had previously been unknown and established it as

24472-550: Was closer to its modern phylogenetical position, Agassiz would consider Pterygotus to represent a crustacean of the Entomostraca subclass. Although Frederick M'Coy did note that Pterygotus resembled the Limulidae and the previously discovered eurypterid Eurypterus in 1849, he classified both Eurypterus and Pterygotus as crustaceans. The new Scottish fossils were named as the species P. anglicus in 1849, which remains

24633-496: Was covered by a carapace (sometimes called the "prosomal shield") on which both compound eyes and the ocelli (simple eye-like sensory organs) were located. The prosoma also bore six pairs of appendages which are usually referred to as appendage pairs I to VI. The first pair of appendages, the only pair placed before the mouth, is called the chelicerae ( homologous to the fangs of spiders). They were equipped with small pincers used to manipulate food fragments and push them into

24794-665: Was dated as Frasnian (Late Devonian), showing that Pterygotus did not become extinct during the Middle Devonian as previously thought. Following close examination and the discovery of new fossil evidence, further genera would be split off from Pterygotus . P. rhenaniae was classified as part of its own genus, Jaekelopterus , by Charles D. Waterston in 1964. He considered the species sufficiently distinct from other Pterygotus species due to its supposedly segmented genital appendage (a feature later realized to be wrong), its narrow and long chelicerae, and its primary teeth being angled slightly anteriorly. Another species, P. ventricosus ,

24955-497: Was discovered in Carboniferous-aged fossil deposits of Scotland in 2005. It was attributed to the stylonurine eurypterid Hibbertopterus due to a matching size (the trackmaker was estimated to have been about 1.6 meters (5.2 ft) long) and inferred leg anatomy. It is the largest terrestrial trackway—measuring 6 meters (20 ft) long and averaging 95 centimeters (3.12 ft) in width—made by an arthropod found thus far. It

25116-452: Was more or less parallel and similar to that of extinct and extant xiphosurans, with the largest exception being that eurypterids hatched with a full set of appendages and opisthosomal segments. Eurypterids were thus not hemianamorphic direct developers, but true direct developers like modern arachnids. The most frequently observed change occurring through ontogeny (except for some genera, such as Eurypterus , which appear to have been static)

25277-409: Was not required to specify a type. A type species is both a concept and a practical system that is used in the classification and nomenclature (naming) of animals. The "type species" represents the reference species and thus "definition" for a particular genus name. Whenever a taxon containing multiple species must be divided into more than one genus, the type species automatically assigns the name of

25438-429: Was not the largest of the pterygotids, several species were large, surpassing 1 metre (3.3 ft) in length. The largest known species was P. grandidentatus , with the largest known isolated chelicerae fragments suggesting a length of 1.75 metres (5.7 ft). The Estonian P. impacatus is the second largest known species, the largest fragmentary remains suggesting a length of 1.65 metres (5.4 ft). P. anglicus ,

25599-505: Was suggested to represent a synonym of Erettopterus osiliensis by Samuel J. Ciurca, Jr. and O. Erik Tetlie in 2007, based upon the similar shape of the eyes and the carapace. Such a reassignment would have implications for other species of Pterygotus as well, with P. impacatus potentially also representing a synonym of E. osiliensis . Subsequent studies and lists of eurypterid species have continued to treat P. monroensis and P. impacatus as distinct species of Pterygotus . Pterygotus

25760-599: Was the second pterygotid to be discovered from the well known eurypterid fauna of Lesmahagow in Lanarkshire, Scotland. As pterygotids commonly occur in association with multiple related genera, it was considered unusual that there was only one species, Erettopterus bilobus , present in Lesmahagow. Fossil remains of P. lanarkensis had been known since 1868 (first collected by Robert Slimon in 1855–1860), but were first recognized as such by Kjellesvig-Waering in 1964. Represented by

25921-518: Was used as an ovipositor (used to deposit eggs). The different types of genital appendages are not necessarily the only feature that distinguishes between the sexes of eurypterids. Depending on the genus and species in question, other features such as size, the amount of ornamentation and the proportional width of the body can be the result of sexual dimorphism. In general, eurypterids with type B appendages (males) appear to have been proportionally wider than eurypterids with type A appendages (females) of

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