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126-562: 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 known arthropods to have ever lived with some members of the family, such as Jaekelopterus and Acutiramus , exceeding 2 metres (6.6 ft) in length. Their fossilized remains have been recovered in deposits ranging in age from 428 to 372 million years old ( Late Silurian to Late Devonian ). One of

252-460: 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

378-421: A dry bite , a dose appropriate to the nature of the prey or enemy, or a maximal dose. The control is also necessary for actions such as the spitting of venomous silk by members of the family Scytodidae ; they depend on that mechanism both in hunting and defence. When a spider bites, the two parts of the chelicerae come together like a folding knife, and when making a threat display or actually preparing to bite,

504-419: A fang portion that articulates with the base segment. Almost all spiders have venom glands and can inject the venom through openings near the tips of their fangs when biting prey. The glands that produce this venom are located in the two segments of the chelicerae, and, in most spiders, extend beyond the chelicerae and into the cephalothorax. The fang, the organic functional equivalent to a hypodermic needle

630-558: 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

756-468: 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

882-534: A family of its own, the "Jaekelopteridae". The error with the genital appendage was later discovered and rectified, making Jaekelopterus a member of the Pterygotidae once more. In 1974, Størmer raised the Pterygotus subgenera Acutiramus and Truncatiramus to the level of separate genera. Truncatiramus has later been recognized as representing a synonym of Erettopterus . In 1986, Paul Selden examined

1008-476: 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

1134-431: 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

1260-604: 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

1386-451: 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

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1512-561: 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),

1638-407: 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

1764-532: A total temporal range of approximately 56 million years), reaching their greatest diversity during the Late Silurian, a period in time when other eurypterid groups became increasingly diverse as well. The enlargement and specialisation of the chelicerae within the Pterygotidae has been recognised as one of the two most striking evolutionary innovations within the Eurypterida, besides the transformation of

1890-405: 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

2016-414: Is among the best supported within the Eurypterida. Relationships within it has historically been difficult to resolve due to wrong interpretations of genital appendage of Jaekelopterus , and the consequential disturbance of character states historically interpreted as primitive and derived within the group when the error was solved. Subsequent descriptions and redescriptions have ensured that the phylogeny of

2142-502: 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

2268-851: 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) Chelicerae Chelicerae can be divided into three kinds: jackknife chelicerae, scissor chelicerae, and three-segmented chelate chelicerae. The jackknife chelicera

2394-544: 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

2520-419: 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

2646-406: Is considered an unspecified pterygotid. In 2009, Pterygotus ventricosus was recognized as being distinct from, and far more basal than, other species in its genus and was thus named as the type species of a new genus, Ciurcopterus . Studies of specimens referred to this genus resolved long-standing contentiousness about the precise phylogenetic position of the Pterygotidae, providing evidence in

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2772-406: 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

2898-562: 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

3024-481: Is known of eurypterid anatomy contradicts the undulation hypothesis simply because eurypterid bodies were likely very stiff. The body segments were nearly equal in width and thickness with little difference in size between segments directly adjoining to each other, while there is no evidence for any sort of tapering or other mechanism that would have increased flexibility. Any flexing of the body would require muscular contractions, but no major apodemes (internal ridges of

3150-433: Is mostly considered as far too simplistic of an explanation by modern researchers. Detailed analyses have failed to find any correlation between the extinction of the pterygotids and the diversification of the vertebrates. Pterygotid eurypterids , which occur in strata ranging from Late Silurian to Late Devonian in age, ranged in size from quite small animals, such as Acutiramus floweri at 20 cm (7.9 in), to

3276-623: Is only shared by the closely related Slimonia and by the derived hibbertopterid Hibbertopterus and mycteroptid Hastimima , where a flattened telson had convergently evolved . The telson is in general flat but with a raised thin median keel. The posterior margin (tip) of the telson form a short spine in some genera, such as Pterygotus and Acutiramus , and is indented (giving a bilobed appearance) in Erettopterus . The function of these specialised telsons has historically been controversial and disputed. Erik N. Kjellesvig-Waering compared

3402-495: 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

3528-411: 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

3654-447: 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

3780-467: Is subchelate (with fixed finger much reduced or absent) and is composed of two segments. This type of chelicera occurs exclusively in the Tetrapulmonata . Jackknife chelicera are described in two different forms: orthognathous and labidognathous. Orthognathous chelicerae are articulated in a manner that enables movements of the appendages parallel to the body axis. This kind of chelicera occurs in

3906-468: 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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4032-424: 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

4158-411: Is what penetrates the skin, fur, or exoskeleton of the spider's target—spider mouthparts are primarily intended for envenoming a spider's prey in most species, typically insects and other small arthropods . The basal portion includes all or part of the spider's venom glands, which can be squeezed to control the amount of venom forced out of the glands. Such control permits a spider to administer either

4284-592: 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

4410-537: The Liphistiomorphae and Mygalomorphae spiders and in the related orders Amblypygi , Schizomida and Uropygi . Labidognathous chelicerae move at right angles to the body axis. This kind of chelicera is rotated and occurs exclusively in the Araneomorphae spiders. The chelicerae consist of a base segment, sometimes called the "paturon", that articulates with the cephalothorax (or prosoma ) and

4536-439: 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

4662-409: 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

4788-600: The prosoma , or "head"), would have been capable of turning the entire appendage in a twisting way, which has led researchers to conclude that the function of the chelicerae would not have been only, or even primarily, for defense but rather to capture and convey food to the mouth. When captured, prey would need to be broken into smaller pieces to be able to fit into the mouth; eurypterid mouths were even less adapted to devour large pieces than mouths of modern crabs are. The eurypterid walking appendages could not cut, transport or grasp anything, and as such this would also be done with

4914-406: 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

5040-479: 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 ,

5166-571: 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

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5292-588: 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

5418-937: 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

5544-637: The Eurypterida, the Pterygotidae has attracted a lot of attention ever since their discovery. The first fossils found, discovered by quarrymen in Scotland , were referred to as " Seraphims " by the quarrymen. When describing Pterygotus itself in 1839, Louis Agassiz first thought the fossils represented remains of fish, with the name meaning "winged one", and only recognized their nature as arthropod remains five years later in 1844. By 1859, 10 species (many of which would later be reassigned) had been assigned to Pterygotus . John William Salter recognized that it

5670-568: 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

5796-496: 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

5922-406: The Pterygotidae. In 1961, Kjellesvig-Waering raised Erettopterus to the level of its own genus, recognizing two subgenera of Pterygotus ; P. ( Pterygotus ) and P. ( Acutiramus ), as well as two subgenera of Erettopterus ; E. ( Erettopterus ) and E. ( Truncatiramus ). Kjellesvig-Waering placed the primary taxonomical value on the morphology of the telson, considering potential differences in

6048-415: The actual count appears to be four joints. Additionally, a three-joint anatomy would have placed the claws at the end of appendages that would essentially have been rigid stalks, rendering their function useless. To have the necessary mobility, the pterygotid chelicerae would have had to have been composed of four joints. The first joint of the chelicerae, where it connects to the epistoma (a plate located on

6174-460: The armor was as "a protection against living enemies". With most of the early vertebrates of the Silurian being just a few decimetres in length and often occurring together with pterygotid eurypterids in freshwater environments, they would seem to represent appropriate prey for the pterygotids, which were large predators with grasping claws. There are few other animals that would present appropriate prey and there are virtually no other predators than

6300-547: 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

6426-460: The body) was expanded and flattened with a small median keel. The posterior margin (tip) of the telson forms a short spine in some genera ( Pterygotus and Acutiramus ) and is indented (giving a bilobed appearance) in others ( Erettopterus ). Like other chelicerates, pterygotids possessed chelicerae . These appendages are the only ones that appear before the mouth and take the form of small pincers used to feed in all other eurypterid groups. In

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6552-642: The carapace clearly belonged to a pterygotid, further suggesting a close relationship between the Pterygotidae and the Slimonidae within the Pterygotioidea superfamily. Alfred S. Romer suggested in 1933 that early vertebrate evolution might have been heavily influenced by pterygotid predation. Early vertebrates of the Late Silurian and Devonian are often heavily armored, and it is likely that this represents an ancestral vertebrate trait that

6678-576: 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

6804-413: The chelicerae and metastoma (a large plate that is part of the abdomen) to be secondary in importance. Jaekelopterus , previously designated as a species of Pterygotus , was separated into a distinct genus in 1964 based on the supposed different segmentation of the genital appendage. These supposed differences would later turn out to be false, but briefly prompted Jaekelopterus to be classified within

6930-506: The chelicerae of other eurypterids as well as those of other arthropods, such as crustaceans and xiphosurans ; the capture and cutting of food into smaller pieces and transport of food into the mouth as well as defense. Though most other eurypterid families had simple pincers, the Pterygotidae is the only eurypterid family to possess enlarged and robust chelicerae with claws and teeth, showing unique adaptations to defense and/or prey capture. The chelicerae were composed of several joints, though

7056-404: The chelicerae. In crabs, the claws tear food apart and then transport the smaller pieces to the mouth. Based on the feeding process seen in modern arthropods with chelicerae, one of the claws would hold the prey while the other would cut off pieces and transport it to the mouth with continuous and simple movements. The large and flattened pterygotid telson is a distinctive feature of the group that

7182-482: The cheliceral claws, which are robust and heavily sclerotized, a majority of fossilized large pterygotid body segments are unmineralized and thin. Even the plates that form the surface of the abdominal segments, the stergites and sternites , are preserved as paper-thin compressions which suggests that pterygotids were very light-weight in construction. Similar adaptations have been observed in other prehistoric giant arthropods, such as Arthropleura , and may be vital to

7308-471: The clade is rather robust at the genus level. Yet, a comprehensive species-level phylogenetic analysis has proven impossible due to the large amount of species based on scant and fragmentary fossilised material. The genus Slimonia is thought to represent the sister group to the pterygotids. The cladogram below is based on the nine best-known pterygotid species and two outgroup taxa ( Slimonia acuminata and Hughmilleria socialis ). The cladogram also contains

7434-625: 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

7560-469: 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

7686-584: 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

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7812-439: The curvature of the denticles (teeth) of the chelicerae. The same year (1935), Leif Størmer named a new pterygotid genus, Grossopterus , and split Pterygotus into two other subgenera, Pterygotus ( Pterygotus ) and Pterygotus ( Erettopterus ), designating Pterygotus ( Curviramus ) as a junior synonym of Pterygotus ( Pterygotus ) and not recognizing Pterygotus ( Acutiramus ). A division into three subgenera of Pterygotus

7938-607: 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

8064-412: 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

8190-518: The evolution of arthropod gigantism as a light-weight build decreases the influence of size-restricting factors. Though they were the largest arthropods known to have ever existed, the light-weight build of the pterygotids means that they are unlikely to have been the heaviest. Giant eurypterids of other lineages, notably the deep-bodied walking forms of the Hibbertopteridae, such as the almost 2 metre long Hibbertopterus , might have rivalled

8316-452: The evolution of significantly faster-moving fish and the evolution of proper jaws . These adaptations, potentially a result of pterygotid predation, would have significantly affected the likelihood of fish representing pterygotid prey and larger predatory fish may even have begun preying on pterygotids and other eurypterids, contributing to their decline and extinction. The arguments of Romer were based on evolutionary trends in both groups and

8442-537: The exact number is somewhat controversial with some researchers stating three, others four and some claiming that the number of joints varies between three and five depending on the species and genus in question ( Pterygotus would have three joints and Erettopterus five). The most common interpretation historically was that the number of joints were three, with a long basal joint followed by two smaller distal joints with teeth. More modern research on very complete specimens of Acutiramus and Erettopterus has revealed that

8568-410: The exoskeleton that supports muscular attachments) or any muscle scars indicative of large opisthosomal muscles have been found. Instead, pterygotids were most likely propelled by the enlarged and flattened paddlelike sixth pair of prosomal appendages, like other swimming eurypterids. An alternate hypothesis first proposed by C. D. Waterston in 1979 postulates that the median keel and the telson at large

8694-671: 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

8820-433: 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

8946-569: 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

9072-449: The form of shared characteristics that Slimonia , not Herefordopterus or Hughmilleria as previously thought, was the closest sister taxon of the group. The pterygotids were one of the most successful eurypterid groups, with fossilised remains having been discovered on all continents except Antarctica. They are the only eurypterid group with a cosmopolitan distribution . Their remains range in age from 428 to 372 million years old (for

9198-452: The fossil co-occurrences of both groups but he did not present a detailed analysis. The groups do frequently occur together, with pterygotids present at more than two-thirds of fossil localities where eurypterids and fish are recorded together. There is also a recorded increase in fish diversity at the same time as the eurypterids began to decline in the early Devonian, but available data does not support any direct competitive replacement. Though

9324-494: The fossil material of the enigmatic arthropod Necrogammarus and concluded that the specimen represents the infracapitulum and attached palp of a large pterygotid. The fossil likely belongs to either Erettopterus marstoni or Pterygotus arcuatus , both found in the same locality, but the lack of key diagnostic features in the Necrogammarus remains makes assignment to either impossible, and therefore, Necrogammarus

9450-476: 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

9576-501: 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

9702-498: 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

9828-517: The group formidable predators. The strange proportions and large size of the pterygotid eurypterids led to the quarrymen who discovered the first fossil remains of the group to give them the common name " Seraphims ". Studies on the cheliceral morphology and compound eyes of the pterygotids have revealed that the members of the group, despite overall morphological similarities, were highly divergent in their ecological roles. Pterygotid ecology ranged from generalized predatory behaviour in basal members of

9954-534: The group, such as Erettopterus , to active apex predators, such as Jaekelopterus and Pterygotus , and ambush predators and scavengers, such as Acutiramus . Some researchers have suggested that the pterygotid eurypterids evolved in something akin to an " arms race " with early vertebrates, that the evolution of heavy armor in the ostracoderms could be attributed to pressure from pterygotid predation and that later pterygotid decline could be attributed to subsequent evolutionary trends in fish. This hypothesis

10080-404: 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

10206-467: 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

10332-406: The largest known arthropods to have ever lived, with several species surpassing two metres in length (such as Jaekelopterus rhenaniae at 2.5 metres and Acutiramus bohemicus at 2.1 metres). There are several known factors that restrict the size arthropods are able to grow to. These factors include respiration, the energy it costs to moult, locomotion and the properties of the exoskeleton. Except

10458-452: The largest known arthropods to have ever lived. Several species reached and exceeded 2 metres in length, the largest known species including Jaekelopterus rhenaniae at 2.5 metres and Acutiramus bohemicus at 2.1 metres. Like all other chelicerates , and other arthropods in general, pterygotid eurypterids possessed segmented bodies and jointed appendages (limbs) covered in a cuticle composed of proteins and chitin . In pterygotids,

10584-471: 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

10710-472: 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

10836-424: 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

10962-483: 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

11088-475: The most posterior prosomal appendage into a swimming paddle (a trait seen in all eurypterids in the Eurypterina suborder). The most primitive and basal pterygotid, Ciurcopterus , preserves a mixture of characteristics that are reminiscent of Slimonia , which is often interpreted as a sister-taxon of the Pterygotidae, as well as more derived pterygotids. The appendages were similar to those of Slimonia but

11214-489: The most successful groups of eurypterids, the pterygotids were the only eurypterid family to achieve a truly worldwide distribution . Several evolutionary innovations made the pterygotids unique among the eurypterids, with large and flattened telsons (the posteriormost division of the body) likely used as rudders to provide additional agility and enlarged chelicerae (frontal appendages) with claws. These claws were robust and possessed teeth which would have made many members of

11340-440: 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

11466-417: The outer surface of the exoskeletons, ranging in size from small to gigantic, was composed of semilunar scales. The chelicerate body is divided into two tagmata (sections); the frontal prosoma (head) and posterior opisthosoma (abdomen). The appendages were attached to the prosoma, and were characterized in pterygotids by being small and slender and lacking spines. The telson (the posteriormost division of

11592-829: The primary unifying characteristics for the various clades, as well as 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, 8 in) Slimonia acuminata (100 cm, 3 ft 3 in) Ciurcopterus ventricosus (70 cm, 2 ft 4 in) Erettopterus waylandsmithi (60 cm, 2 ft) Erettopterus osiliensis (90 cm, 2 ft 11 in) Erettopterus serricaudatus (60 cm, 2 ft) Erettopterus bilobus (70 cm, 2 ft 4 in) Pterygotus anglicus (160 cm, 5 ft 3 in) Jaekelopterus rhenaniae (250 cm, 8 ft 2 in) Pterygotus Pterygotus

11718-465: 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

11844-499: 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

11970-408: The pterygotid telson to the large tail fluke of whales in 1964. The pterygotids were hypothesized to have moved by undulating the entire opisthosoma (the large posterior section of the body) by moving the abdominal plates, as such undulations of the opisthosoma and telson would have acted as the propulsive method of the animal, rendering the swimming legs used by other eurypterid groups useless. What

12096-502: The pterygotids as a suborder, but classifies them within the superfamily Pterygotioidea as the most derived members of the suborder Eurypterina. The cladogram below is simplified from a study by Tetlie (2007), showcasing the derived position of the pterygotids within Eurypterina. Stylonurina Megalograptoidea Eurypteroidea Carcinosomatoidea Waeringopteroidea Adelophthalmoidea Hughmilleria Herefordopterus Slimonia Pterygotidae The clade Pterygotidae

12222-430: The pterygotids in weight, if not surpassed them. Since its creation by John Mason Clarke & Rudolf Ruedemann in 1912, the phylogenetic status of the Pterygotidae has changed several times. Leif Størmer considered the group to represent a family within the eurypterid superfamily Eurypteracea. In 1962, Nestor Ivanovich Novojilov raised the groups in question to subordinal and superfamily status, Eurypteracea becoming

12348-455: The pterygotids that would warrant the evolution of armored protection in their prey. The pterygotids reached their maximum size and number in the Late Silurian and Early Devonian, after which they saw rapid decline during the Devonian. This decline occurred at around the same time as there was an increase in unarmored vertebrates as well as a growth in fish size and the increased migration of fish into marine environments. The Devonian would also see

12474-454: The pterygotids would be extinct at that point, both fish and eurypterids would decline in the Middle Devonian only to peak again in the late Devonian and to begin another decline in the Permian . Detailed analyses have failed to find any correlation between the extinction of the pterygotids and the diversification of the vertebrates. The function of pterygotid chelicerae was likely the same as

12600-462: The pterygotids, the chelicerae were large and long, with strong well developed teeth on specialised chelae (claws). These specialised chelicerae, likely used for prey capture but differing in the exact role from genus to genus, are also the primary feature that distinguishes members of the group from eurypterids of the other pterygotioid families, Slimonidae and Hughmilleriidae , and other eurypterids in general. Due to their unique features within

12726-410: 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

12852-573: The rather large spider shown above are quite sharp, and the spider's body is well adapted to driving the fangs into flesh. Some spider bites, such as those of the Sydney funnel-web spider , are reported to have penetrated toenails and soft leather shoes. The uncate chelicera is chelate and composed of two segments and occurs in the orders Pseudoscorpiones , Solifugae , Ricinulei , and Araneae (e.g., brown recluse , cellar spider , and crevice weaving spider ). Having three-segmented chelate chelicerae

12978-606: 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

13104-409: 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

13230-426: 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

13356-538: 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

13482-400: 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

13608-550: 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

13734-415: 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

13860-508: 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,

13986-401: The spider will open the angle of the fangs with the basal portion of the chelicerae and also open the angle of the basal portion with the cephalothorax. In the tarantulas and other Mygalomorphae , the horizontal separation of the tips of the fangs does not change much, but in the other spiders the tips of the fangs move apart from each other as well as elevating. Even the tips of the fangs of

14112-414: The suborder Eurypterina and creating the superfamily Pterygotioidea . Both Størmer (in 1974) and Erik N. Kjellesvig-Waering (in 1964) would come to consider the pterygotids as distinctive enough, due to their uniquely enlarged chelicerae, to warrant the status of a separate suborder, which was dubbed the "Pterygotina". More modern cladistics and phylogenetic analyses does not support the classification of

14238-538: 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,

14364-463: 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

14490-417: 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

14616-480: 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

14742-412: 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

14868-562: 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

14994-667: 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 ,

15120-404: Was later lost or reduced, rather than something that evolved separately in several groups at the same time. Some researchers have suggested that the armor was to protect against hitting rocky surfaces in fast flowing streams, but Romer pointed out that there is no such armor protection in modern fish that live in that type of environment. Instead, Romer stated that the only reasonable explanation for

15246-431: 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 ,

15372-587: Was possible to divide Pterygotus based on the morphology of the telsons of the species that had been assigned to it. He divided Pterygotus into subgenera, erecting Pterygotus ( Erettopterus ) for species with a bilobed telson. The family Pterygotidae was erected in 1912 by John Mason Clarke & Rudolf Ruedemann to constitute a group for the genera Pterygotus , Slimonia , Hastimima and Hughmilleria . Pterygotus would also designated as containing two " subgenera ", Pterygotus ( Curviramus ) and Pterygotus ( Acutiramus ) in 1935, differentiated by

15498-409: Was proposed by Ferdinand Prantl and Alois Přibyl in 1948, retaining P. ( Erettopterus ) and P. ( Pterygotus ) but also restoring P. ( Acutiramus ) to subgenus level. Erik N. Kjellesvig-Waering emended the family in 1951, when the genera Hastimima, Hughmilleria , Grossopterus and Slimonia were referred to their own family, the Hughmilleriidae , which left Pterygotus as the only genus within

15624-507: 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

15750-611: 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

15876-409: Was used to steer the body, working more like a vertical and horizontal rudder than a tail fluke. Calculations and the creation of models of plaster allowed Plotnick et al. (1988) to determine that the design of the pterygotid telson could functionally work as a rudder, which would have enabled the pterygotids to be agile animals capable of quick turns when chasing after prey. The Pterygotidae includes

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