Pterygotus
Pterygotus | |
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Fossils of P. anglicus | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Subphylum: | Chelicerata |
Order: | †Eurypterida |
Superfamily: | †Pterygotioidea |
Family: | †Pterygotidae |
Genus: | †Pterygotus Agassiz, 1839 |
Type species | |
†Pterygotus anglicus Agassiz, 1849
| |
Species | |
17 valid species
6 dubious species
| |
Synonyms | |
Genus synonymy
Synonyms of P. anglicus
Synonyms of P. barrandei
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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 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 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 the largest species, such as P. kopaninensis at 50 centimetres (20 in).
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.
Description
With 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.[1] 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.[2]
Pterygotus is classified as part of the
Pterygotus is distinguishable from other pterygotids by the curved
Size
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)).[1] Though Pterygotus was not the largest of the pterygotids, several species were large, surpassing 1 metre (3.3 ft) in length.[2]
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).
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 the smallest known species, P. kopaninensis, at 50 centimetres (20 in) in length.[2]
History of research
Initial finds
The first fossils of Pterygotus were found in deposits of
The new Scottish fossils were named as the species P. anglicus in 1849, which remains 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.[13]
P. problematicus was also used as the designation for an incomplete chelicera discovered in the Welsh Borderland of western England by
Two further species that remain assigned to the genus to this day would be described from England during the 19th century; P. ludensis of
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 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 is to other pterygotid species discovered in the P. cobbi locality (such as Acutiramus macrophthalmus).[5]
Creation of subgenera and the Pterygotidae
By 1859, 10 species had been assigned to the genus,[15] 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.[16] Further subgenera would be named as more differences were noted between the species, such subgenera include Pterygotus (Curviramus) and Pterygotus (Acutiramus), named in 1935 based upon features of the denticles (teeth) of the chelicerae.[16] Pterygotus (Curviramus) was later recognized as synonymous with Pterygotus (Pterygotus) by Leif Størmer the same year,[10] and Erettopterus and Acutiramus would be recognized as separate, but closely related, genera (Erettopterus by Erik N. Kjellesvig-Waering in 1961,[10] and Acutiramus by Størmer in 1974).[16]
In 1912, 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.[8]
Further discoveries
Though early discoveries of Pterygotus were confined to England and North America, fossil finds throughout the 20th century would help establish that Pterygotus as a genus achieved a nearly cosmopolitan distribution.[17] 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 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.[18] 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 the rest of the pterygotids.[19]
Kjellesvig-Waering named the species P. bolivianus in 1964 based on fossils recovered from deposits of
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.[21] Another species, P. ventricosus, 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.[22]
Discoveries in Europe
New fossil finds also revealed the presence of Pterygotus in several European countries where it had previously been unknown and established it as 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 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 the species, consisting of coxae and a genital appendage, but their assignment to the species is doubtful.[23]
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 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.[16] 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 the "questions [about its identity] can not be answered from the material available to me".[24]
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 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.[23]
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, 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.[25]
In 1964, two species described by Kjellesvig-Waering increased the known range of Pterygotus to
P. impacatus, recovered from deposits of Ludlow age at
England
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 (
P. lightbodyi is named in honor of Robert Lightbody, a British amateur geologist who made valuable contributions to paleontological research on 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 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 the species is the combination of a large terminal tooth and a large upright tooth near it.[11]
P. grandidentatus is known from a single specimen, the anterior half of a free ramus of a chelicera discovered in the
England would also yield a dubious species, P. taurinus, from deposits of Pridoli[2] or Devonian[11] age. Named by Salter in 1868, P. taurinus is treated as a dubious species for the reason that it 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 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.[11]
Discoveries in North America
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), the Early Devonian P. carmani (1961, USA) and P. floridanus (1950, Florida, USA) and the Middle Devonian P. gaspesiensis (1953, Quebec, Canada).[2][26]
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 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.[27]
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 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.[30] Although it was later placed on the genus Waeringopterus, Samuel J. Ciurca, Jr. and O. Erik Tetlie concluded in 2007 that 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.[16]
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 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 the arrangement of the smaller teeth of the claws and from P. barrandei in that P. floridanus has a more slender ramus.[31]
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 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 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 the claw.
P. marylandicus, from deposits of
The species P. monroensis, known from deposits of late Wenlock to Ludlow age in New York State, USA, 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.[16] Subsequent studies and lists of eurypterid species have continued to treat P. monroensis and P. impacatus as distinct species of Pterygotus.[15]
Classification
Pterygotus is classified within the family Pterygotidae in the superfamily Pterygotioidea,[15] 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 the telson.[32]
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 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).[33] 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.[33]
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 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").[1][34]
Pterygotioidea |
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Paleobiology
The cheliceral morphology and
Both Pterygotus anglicus and
All known pterygotids (though they are so far unknown in Ciurcopterus
Paleoecology
Pterygotus lived in both fully marine environments as well as lacustrine and fluvial systems, and its fossils are today recovered and associated with common and diverse fossils indicative of such environments.
The deposits where the holotype specimen of P. kopaninensis was found preserves fossils of many other animals as well. Among them are
In the Devonian
Five species of Pterygotus have been discovered in deposits of Silurian age in the Welsh Borderland, P. ludensis, P. arcuatus, P. grandidentatus, P. lightbodyi and P. denticulatus. The Welsh Borderland preserves one of the more extensive eurypterid faunas known, with the exact genera and species depending on the precise time. The Wenlock-aged P. grandidentatus occurred together with Mixopterus, P. arcuatus of Middle Ludlow age occurred together with Salteropterus, Erettopterus and Carcinosoma whilst P. lightbodyi and P. denticulatus were contemporaries with each other and species of the genera Erettopterus and Carcinosoma. P. ludensis, Downtonian in age, occurred together with a diverse array of eurypterids composed of Carcinosoma, Dolichopterus, Erettopterus, Hughmilleria, Parahughmilleria, Eurypterus, Nanahughmilleria, Marsupipterus, Stylonurus, Tarsopterella, Slimonia and Salteropterus.[11]
Sometimes the only known other fossil eurypterids occurring with Pterygotus are also pterygotids. P. marylandicus occurs together only with Erettopterus.
In some cases, Pterygotus represents the only known eurypterid in its living environment. P. bolivianus was found only associated with trilobites of the genus
See also
References
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- doi:10.1016/j.palaeo.2007.05.011. Archived from the original(PDF) on 18 July 2011.
- ^ a b Kjellesvig-Waering, Erik N. (1961). "Eurypterids of the Devonian Holland Quarry shale of Ohio". Fieldiana Geology. 14: 79–98.
- ^ a b Clarke, John Mason (1912). "The Eurypterida of New York". Memoir (New York State Museum and Science Service). 14.
- .
- ^ a b Størmer, Leif (1955). "Merostomata". Part P Arthropoda 2, Chelicerata. Treatise on Invertebrate Paleontology. pp. 30–31.
- ^ JSTOR 1301554.
- ^ Murchison, Roderick Impey (1839). The Silurian System, Founded on Geological Researches in the Counties of Salop, Hereford, Radnor, Montgomery, Caermarthen, Brecon, Pembroke, Monmouth, Gloucester, Worcester, and Stafford: With Descriptions of the Coalfields and Overlying Formations. Albemarle Street. p. 606. Note that this work incorrectly translates Pterygotus as "winged fish", but there is no "fish" element in the name.
- ^ JSTOR 1301554.
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- ^ a b c "The Old Red Sandstone of Great Britain (Geological Conservation Review Series No. 31) | JNCC Resource Hub". hub.jncc.gov.uk. Retrieved 20 August 2023.
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- ^ "Fossilworks: Eurypterids of the Melbourne Group, ?Dargile Formation, at Melbourne (Silurian of Australia)". fossilworks.org. Retrieved 27 February 2018.
- ^ "Dargile Formation, Winneke Reservoir Site (Silurian of Australia)". fossilworks.org. Retrieved 27 July 2018.
- ^ a b R. E. Plotnick. 1999. Habitat of Llandoverian-Lochkovian eurypterids. In A. J. Boucot, J. D. Lawson (eds.), Paleocommunities – a case study from the Silurian and Lower Devonian
- ^ "Eurypterid-Associated Biota of the Rootsikula Horizon, Saaremaa, Estonia: Rootsikula, Estonia". paleobiodb.org. Retrieved 27 July 2018.
- ^ "Eurypterid-Associated Biota of the Pittsford Shale, Pittsford, New York: Ludlow, New York". paleobiodb.org. Retrieved 27 July 2018.
- ^ "Platy limestone-shale facies, Upper Pridolian, Barrandian S-D boundary section: Pridoli, Czech Republic". paleobiodb.org. Retrieved 27 July 2018.
- ^ "Eurypterus remipes tetragonopthalmus Community, Ustje subsuite, Podolia (Silurian of Ukraine)". paleobiodb.org. Retrieved 27 July 2018.
- ^ "Eurypterid-Associated Biota of the Chortkov Horizon in Podolia (Devonian of Ukraine)". paleobiodb.org. Retrieved 27 July 2018.
- ^ "Eurypterids of the Keefer Sst. Mbr, Mifflintown Fmn., Hancock, Maryland: Wenlock, Maryland". paleobiodb.org. Retrieved 27 July 2018.
- ^ "Eurypterid-Associated Biota of the Ledbury Formation, Ewyas Harold, England: Pridoli, United Kingdom". paleobiodb.org. Retrieved 27 July 2018.
- ^ "Sun Oil Co. well, Core 44 (3552–3568 feet): Lochkovian, Florida". paleobiodb.org. Retrieved 27 July 2018.
- ^ "Gaspe community, Gaspe Sandstone (Devonian of Canada)". paleobiodb.org. Retrieved 27 July 2018.
External links
- Media related to Pterygotus at Wikimedia Commons