166-613: Adelophthalmus is a genus of eurypterid , an extinct group of aquatic arthropods . Fossils of Adelophthalmus have been discovered in deposits ranging in age from the Early Devonian to the Early Permian , which makes it the longest lived of all known eurypterid genera, with a total temporal range of over 120 million years. Adelopththalmus was the final genus of the Eurypterina suborder of eurypterids and consisted
332-495: A carapace and seven opisthosomal segments on a large block of sandstone. The name of the species, piussii , honors the collector of the type specimen, Stefano Piussi. In 2018, Shpinev and Russian researcher A. N. Filimonov described a new species named A. khakassicus based in many well-preserved specimens. Found in the Ilemorovskaya Formation of Khakassia (hence the name) in 2014 by Filimonov, it represents
498-578: 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
664-509: 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 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,
830-408: 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
996-621: A subgenus of Eurypterus , based on fossils recovered in Carboniferous-age deposits at Mazon Creek in Illinois (the first species to be described from North America). After examining the Adelophthalmus type specimen in 1934, German paleontologist Paul Guthörl remarked that Anthraconectes and Adelophthalmus were so similar that they would have been synonyms had Adelophthalmus possessed eyes. The name Polyzosternites
1162-530: A Famennian species of Hibbertopterus , H. dewalquei , A. lohesti represents the oldest known eurypterid hitherto discovered in Belgium. A. lohesti is however represented by a single fragmentary specimen whose identification as Adelophthalmus or even eurypterine at large is questionable, with it possibly representing a stylonurid eurypterid instead. Devonian specimens of Adelophthalmus have allegedly also been recovered from Siberia , which would mean that
1328-422: A complete lack of eyes. Since the preserved carapace had no indication of there ever having been any eyes present, Jordan and von Meyer assumed that the animal would have been completely eyeless in life, with the original description of the fossil citing several cases in which eyeless forms occur in arthropod groups otherwise possessing eyes (such as in crustaceans and trilobites). This apparent eyelessness prompted
1494-683: A distinct genus, citing that scorpions with similar dorsal anatomies can be quite different ventrally and that the same could be true for the Carboniferous Adelophthalmus where the ventral morphology is not yet known. A genus Anthraconectes of this nature would be problematic due to its classification depending on the preservational state of any given specimen. A. asturica was described as Lepidoderma asturica by Spanish paleontologist Bermudo Meléndez in 1971 based on fossils from d'Ablana in Spain. The species A. luceroensis
1660-461: A dual respiratory system was present, which would have allowed for short periods of time in terrestrial environments. The name Eurypterida comes from 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
1826-742: 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
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#17327871503491992-416: 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
2158-524: A member of the Pterygotidae, until it was reclassified alongside Hughmilleria and other genera to the family Hughmilleriidae in 1951 by Erik N. Kjellesvig-Waering. Nestor Ivanovich Novojilov classified Slimonia as part of a family of its own in 1968. Slimonia is one of the most closely related genera to the pterygotid family and the Slimonidae is often interpreted as a sister-taxon to
2324-425: 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 ,
2490-722: A narrow postabdomen and a telson with a strongly expanded anterior half. The chelicerae (frontal appendages) were small in comparison to those of the pterygotids and the walking legs had denticles, but no spines. Genital appendages were long and narrow in both males and females. The type species of Slimonia , S. acuminata , was first described as a species of Pterygotus , " Pterygotus acuminata " ( acuminata being Latin for "sharp" or "tapering"), by John William Salter in 1856, based on fossils recovered from deposits of Llandovery - Wenlock (Early to Middle Silurian) age in Lesmahagow , Scotland . That same year David Page erected
2656-523: A new genus to contain the species, as several distinctive characteristics made the species considerably different from other known species of Pterygotus , among them the shape of the carapace and S. acuminata lacking the large cheliceral claws known from Pterygotus . The generic name is derived from and honors Robert Slimon, a fossil collector and surgeon from Lesmahagow. Slimon was the first to discover eurypterid fossils in Lesmahagow, bringing them to
2822-651: A new species of Adelophthalmus from the Tournaisian stage of (most likely) the Lydiennes Formation , in France. Its only known specimen, GLAHM A23113, is a nearly complete body only lacking the telson and preserved in phosphatic nodules . For this reason, it was called Adelophthalmus pyrrhae , named after Pyrrha of Thessaly , a figure from Greek mythology who, together with her husband Deucalion , threw stones that transformed into babies to repopulate
2988-437: A possible life position. They further argued that since the telson of Slimonia also possessed a keel, this would have created significant drag on it while Slimonia was trying to laterally sweep the telson to stab its prey. Lastly, they argued that the serrations on the telson would most likely be attachment points for setae that would have aided the animal in sensing the water flow to make steering much easier. Visual acuity ,
3154-560: A relatively complete fossil measuring just 3.3 centimetres (1.3 in) in length, was discovered through boring at a new coalfield in Campine , northern Belgium. Though the fossil had been slightly damaged, including the entire counterpart being fragmented, owing to careless usage of hammers and diamond bores during excavation, the fossil could nevertheless be studied in detail and compared to known eurypterid species. As Stainier considered every known Carboniferous eurypterid to be part of
3320-471: 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
3486-578: A similar stratigraphical horizon in Kansas, A. oklahomensis was designated a junior synonym of A. sellardsi by American geologist Carl Colton Branson, with the support of Decker, in 1959. The type specimen of A. zadrai , MB.A. 889, was collected in the Czech Republic in 1930 or 1931 and first mentioned in a manuscript by French Carboniferous worker Pierre Pruvost, who dubbed it " Eurypterus (Anthraconectes) Zadrai ", but he did not formally describe
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#17327871503493652-453: A single row of large marginal scales that form a linear serrated edge. A slight dorsal keel is present along the telson. There was a triangular area at the base of the telson which could have been a point of union with the muscles. S. boliviana differed from S. acuminata in having the keel much less developed, narrower and not reaching the terminal spike. The latter was wider, not as pointed and with less developed serrations. The telson itself
3818-408: A species of Eurypterus , E. lohesti (first described in 1889) to Adelophthalmus in 1983 (as A. lohesti ), but this classification is questionable as the morphology of the A. lohesti specimen is not consistent with that otherwise known of Adelophthalmus. The differences include A. lohesti having larger eyes, a wider carapace and what could possible by a median ridge on the carapace. In 2004,
3984-637: A varied and unstable habitat, which indicates that Adelophthalmus was eurytopic (capable of surviving in a wide range of environments). Three other species from the Middle Devonian , A. khakassicus , A. kamyshtensis and A. dubius , are the earliest known species of Adelophthalmus from outside Europe, fossils of the three having been recovered from Khakassia in Russia. By the Late Devonian, Adelophthalmus had already become widespread, with
4150-628: A whole does not appear to have fluctuated much in size over the course of its long evolutionary history, with "large" species occurring in the Devonian ( A. sievertsi at 18 cm, 7 in, and A. waterstoni at 15 cm, 6 in), the Carboniferous (the aforementioned A. mazonensis , A. wilsoni at 20 cm, 7.9 in, and both A. granosus and A. zadrai at 15 cm, 6 in) and during the Permian ( A. luceroensis at 18 cm, 7 in). Most of
4316-553: 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
4482-495: 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
4648-529: 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
4814-935: Is its elongated body and the spurs present on its abdominal segments. The status of the 35 names (out of which two are synonyms) listed below follow a 2018 survey by German paleontologists Jason A. Dunlop and Denise Jekel and British paleontologist David Penney and size- and temporal ranges follow a 2009 study by American paleontologists James Lamsdell and Simon J. Braddy unless otherwise noted. Possible synonym of A. imhofi Possible synonym of A. imhofi Possible synonym of A. imhofi Possible synonym of A. kamyshtensis Possible synonym of A. kamyshtensis Possible synonym of A. imhofi Possible stylonurid affinities Possible hibbertopterid affinities Possible synonym of A. imhofi Possible synonym of A. imhofi Possible synonym of A. imhofi Possible synonym of A. imhofi The first specimen of Adelophthalmus to be discovered
4980-523: Is large for a predatory arthropod, Slimonia would be exceeded in length by later and more derived (more "advanced") members of the closely related pterygotid family of eurypterids, which would become the largest known arthropods to ever live. Slimonia is in many ways similar to the more derived (more "advanced") eurypterids of its superfamily, the Pterygotioidea . In particular, the expanded and flattened telson (the most posterior segment of
5146-489: 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
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5312-487: 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,
5478-729: Is more closely related to the Pterygotidae than the Hughmilleriidae is. The cladogram below is simplified from a study by O. Erik Tetlie (2007), and showcases the position of Slimonia relative to the rest of the Eurypterina suborder of eurypterids, with the Stylonurina suborder as an outgroup . Stylonurina Megalograptoidea Eurypteroidea Carcinosomatoidea Waeringopteroidea Adelophthalmoidea Hughmilleria Herefordopterus Slimonia Pterygotidae In 2017, W. Scott Persons IV and John Acorn reported finding an S. acuminata specimen, MB.A 863, in
5644-521: 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
5810-481: 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
5976-638: 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
6142-439: 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
6308-458: Is the first species of Adelophthalmus to be described from Russia and the first ever Carboniferous eurypterid known from the country. It is also one of few Carboniferous eurypterids found within the territory of the former Soviet Union , the only others being A. carbonarius from Ukraine and Unionopterus from Kazakhstan . Shpinev described two new species of Adelophthalmus in 2012; A. kamyshtensis and A. dubius (the name deriving from
6474-816: 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
6640-494: Is the most taxonomically diverse of all eurypterid genera, containing 33 species considered valid. This large amount of species, many named long ago, have prompted some researchers to designate Adelophthalmus as a " wastebasket taxon " with poorly known internal relationships and phylogeny . The genus as it is currently seen may form a monophyletic group (a group sharing a common ancestor) but might most appropriately be split into different genera along distinct clades formed within
6806-418: 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
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6972-528: The Donets in Ukraine. A new expedition in 2012 carried out by Russian paleontologist Evgeniy S. Shpinev and others in the respectively Russian and Ukrainian localities of Kakichev and Lomuvatka brought a number of well-preserved, presumably juvenile, fossils of A. carbonarius . The exact identification of these fossils is not possible, but they are identified as A. carbonarius since there are no features showing
7138-686: The Early Ordovician or Late Cambrian period. With approximately 250 species, the Eurypterida is the most diverse Paleozoic chelicerate order. Following their appearance during 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
7304-613: The Kirusillas Formation , of Ludlow - Pridoli (Late Silurian) age, in Cochabamba , Bolivia . Named S. boliviana , the holotype (BLV15, deposited at the National Museum of Natural History of France ) comprises a well-preserved telson typical of the genus, being laterally inflated and with a dagger-like terminal point. It was anteriorly covered with small scales semilunar to mucronitic ("spined") grouped into
7470-564: The Patrick Burn Formation of Scotland, dated to the Telychian , around 430 million years ago. The specimen was a complete and articulated series of telsonal, postabdominal and preabdominal segments, and it showed a very strong lateral curvature in the postabdomen. Persons and Acorn admitted that it might have experienced some disarticulation postmortem or could represent a partial molt (exuviae), but concluded that since there
7636-520: The Pentland Hills of Scotland and one dubious species, S. stylops , from Herefordshire , England . The generic name is derived from and honors Robert Slimon, a fossil collector and surgeon from Lesmahagow. Out of the four described species of Slimonia , three measured below or up to 20 centimetres (7.9 in) in length. Only S. acuminata was larger, with the largest specimens measuring 100 centimetres (39 in) in length. Though this
7802-532: 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
7968-443: The carapace (the segment covering the prosoma, the "head") of Adelophthalmus was parabolic in shape, with a narrow marginal rim (edge). The carapace was held in place with the aid of a small and hinged triangular "locking" mechanism placed anteriorly . The eyes were reniform (bean-shaped) and the small ocelli were located between, or slightly behind (depending on the species), the larger eyes. The metastoma (a large plate part of
8134-477: 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, 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
8300-442: 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
8466-405: 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
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#17327871503498632-615: The telson , the posteriormost division of the body, which in most species took the form of a blade-like shape. In some lineages, notably 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
8798-416: The Carboniferous of Scotland, including the species G. perornatus (designated as type, the type specimen consisting of only five tergites ), G. caledonicus and G. kidstoni , by British geologist Ben Peach in 1882. Glyptoscorpius would for a long time erroneously be considered to represent the fossil remains of a scorpion and not an eurypterid. The second species to be described from North America
8964-582: The County of Victoria , Canada , referring it to the genus due to similarities with the Scottish A. kidstoni and the American A. mansfieldi . 1924 saw the description of the species Anthraconectes sellardsi by American paleontologist Carl Owen Dunbar based on two incomplete fossils and few other small fragments from Elmo in Kansas. The first specimen preserves the carapace and the first four tergites of
9130-567: The Devonian, but it first gained its almost cosmopolitan distribution following the amalgamation of the supercontinent Pangaea during the Carboniferous and Permian . The generic name Adelophthalmus means "no obvious eye", referencing that the holotype fossil seemingly represented an eyeless eurypterid, with a carapace (head plate) completely lacking any indication of eyes. Though this has caused much subsequent confusion, including
9296-483: 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
9462-588: The German paleontologist Markus Poschmann referred the species A. sievertsi, first described as part of the genus Rhenopterus by Norwegian paleontologist Leif Størmer in 1969 based on fossil remains from the Devonian Klerf Formation in Germany, to the genus. Poschmann also referred the species Rhenopterus waterstoni (described earlier in 2004 based on the singular specimen BMNH In 60174 from
9628-411: The Late Devonian of Australia) to Adelophthalmus. This species had previously not been assigned to the genus despite clear similarities to other species of Adelophthalmus partly due to there previously not being any solid evidence for the presence of Adelophthalmus as early as the Devonian. A. irinae was described in 2006 based on a fossil specimens (including the holotype, a prosoma, "head", with
9794-616: The Latin dubius = "doubtful"), both based on fossils originally collected by Russian geologist Yuriy Fedorovich Pogonya-Stefanovich in 1960 in deposits 3 km southeast of the village of Kamyshta (which lent its name to A. kamyshtensis ) of the Republic of Khakassia , Russia and now housed at the Borissiak Paleontological Institute . Despite how poorly preserved these fossils are, several features (notably
9960-825: 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
10126-602: 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
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#173278715034910292-658: 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
10458-1110: The Pentland Hills, where remains of S. dubia have been found, preserve fossils of a large amount of other eurypterids, including Drepanopterus pentlandicus , Laurieipterus elegans , Parastylonurus ornatus , Hardieopterus macrophthalmus , Carcinosoma scoticus , Stoermeropterus conicus and Pentlandopterus minor . Also preserved are fossils of orthocerids , such as Geisonoceras maclareni . Similar levels of eurypterid diversity are also observed in fossil deposits where other species of Slimonia have been found. S. acuminata has been found associated with Nanahughmilleria lanceolata , Hardieopterus lanarkensis , Eusarcana obesus , Parastylonurus sigmoidalis , Carcinosoma scorpionis and Erettopterus bilobus and S. stylops have been found associated with Nanahughmilleria pygmaea , Eusarcana salteri , Hardieopterus megalops , Erettopterus brodiei , E. gigas , Hughmilleria banksi , Eurypterus cephalaspis and Pterygotus ludensis . The living environment of
10624-521: The Permian. Slimonia Slimonia is a genus of eurypterid , an extinct group of aquatic arthropods . Fossils of Slimonia have been discovered in deposits of Silurian age in South America and Europe . Classified as part of the family Slimonidae alongside the related Salteropterus , the genus contains three valid species, S. acuminata from Lesmahagow , Scotland , S. boliviana from Cochabamba , Bolivia and S. dubia from
10790-473: The Persons and Acorn study claimed that the fossil didn't show any signs of disarticulation, Lamsdell, Marshall, and Briggs showed this is likely not true. They argued that both tergite 8 and 10 clearly overlapped the other tergites in an unnatural way. Furthermore, they noted that the specimen was definitely a molt rather than a carcass, and argued that this meant that the pose the fossil was in did not represent
10956-494: 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
11122-472: The Pterygotidae. The other Pterygotioid family, the Hughmilleriidae , has also been interpreted as the most closely related sister-taxon to the pterygotids. The discovery of Ciurcopterus , the most primitive known pterygotid, and studies revealing that Ciurcopterus combines features of Slimonia (the appendages are particularly similar) and of more derived pterygotids, revealed that the Slimonidae
11288-742: The Silurian. Baltica would later collide with the continents Avalonia and Laurentia and form the landmass Euramerica , where most of basal adelophthalmid evolution took place in the Early Devonian . The earliest known species of Adelophthalmus is A. sievertsi from Early Devonian ( Emsian ) deposits of the Klerf Formation in Wilwerath (in the Rhineland-Palatinate ), Germany, then part of Avalonia within Euramerica. A. sievertsi lived in near-shore environments, typically
11454-598: 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
11620-454: The abdomen) of Adelophthalmus was oval in shape, with the first opisthosomal (the opisthosoma refers to all segments after the carapace, essentially the abdomen ) having a reduced length and being tapered laterally . The body of Adelophthalmus ended with a long and sharp styliform telson (the posteriormost segment, here in the shape of a spike). The feature that primarily distinguishes Adelophthalmus from other adelophthalmid eurypterids
11786-487: 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
11952-537: 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
12118-442: 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
12284-454: 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
12450-418: The attention of Roderick Murchison in 1851. S. acuminata remains the largest known species, with the largest specimens measuring up to 100 cm (39 in) in length. In 1899, an additional species, S. dubia , would be referred to the genus. This species was recovered from slightly earlier deposits (Llandovery age) in the Pentland Hills of Scotland and could be distinguished from S. acuminata by
12616-436: The biggest species of the genus. The holotype, PM TGU 168/108, is composed of parts of the metasoma and a complete telson, with several other known paratypes. As A. khakassicus is known from similar stratigraphic levels to those of A. kamyshtensis and A. dubius , it has been suggested that these three species could represent synonyms. In 2020, Lamsdell, Victoria E. McCoy, Opal A. Perron-Felle and Melanie J. Hopkins described
12782-513: The body and appendages. In some arthropods, pustules serve as attachment points of setae (bristle- or hair-like structures with sensory functions). Similar pustule rows have been discovered in the other eurypterid Drepanopterus abonensis , a sweep-feeder that used the marginal rim to search the substrate of its living environment for prey. If the pustules of S. acuminata had setae, these pustules may have functioned as tactile and sensory organs used for locating and identifying prey, together with
12948-450: The body was very stiff, and that the flattened telson would likely have served as a rudder that would have allowed the animals to be agile and capable of quick turns when chasing after prey, contradicting previous hypotheses that the telson would have served a propulsive function. Whilst the postabdomen of Slimonia was likely similarly stiff and inflexible dorsally (up and down), Persons and Acorn claimed that their specimen suggested that it
13114-440: The body) of Slimonia is similar to that of the pterygotid eurypterids and is a feature that Slimonia and the pterygotids only share with some derived hibbertopterid eurypterids (where the feature convergently evolved). The pterygotid telson was in general slightly larger than that of Slimonia and was more slender. The telson spike of Slimonia was much longer than any seen in the Pterygotidae (constituting just over half of
13280-414: 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
13446-458: 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
13612-517: The choice of name , Adelophthalmus , meaning "no obvious eye". The species name, granosus , is derived from the latin grānōsus ("grainy" or "full of grains"), referring to the state of the fossil preservation having given some of the fossils a grainy texture. The type specimen, to this day the only specimen referred to A. granosus , is today held in the arthropod paleontology collections of the Natural History Museum of Berlin under
13778-402: The clarity of vision, can be determined in arthropods by determining number of lenses in their compound eyes and the interommatidial angle (shortened as IOA and referring to the angle between the optical axes of the adjacent lenses). The IOA is especially important as it can be used to distinguish different ecological roles in arthropods, being low in modern active arthropod predators. Slimonia
13944-460: The closely related pterygotid family of eurypterids, which would become the largest known arthropods to ever live. Slimonia can be distinguished from other members of its family, the Slimonidae , by a variety of characteristics. The prosoma (head) is quadrate (square-shaped) in shape and had small compound eyes on the frontal corners. The bodies were large and cordate (heart-shaped), with
14110-420: 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
14276-421: The current confines of the genus. Adelophthalmid eurypterids such as Adelophthalmus were small and streamlined nektonic (actively swimming) eurypterids with prominent cuticle sculptures (ornamentation consisting of small, minute, scales across their backs). These scales are perhaps the most distinguishing feature of the group, though similar scales have been reported in other eurypterid groups, most notably
14442-695: 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
14608-403: The enlarged cheliceral claws of the pterygotids and was smaller in size than the largest members of that group. Prey likely included jawless fish such as heterostracans and early osteostracans , which Slimonia would have seized with its frontal appendages. Slimonia traversed its living environment on spindly legs or through using its swimming appendages. The lungs of the genus were located on
14774-409: 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
14940-411: 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
15106-515: 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
15272-454: 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
15438-485: The fossil (Dr. Palisa) and without any designation of it representing a type specimen. Pruvost was also honored through the naming of A. pruvosti (described as Lepidoderma pruvosti by Norwegian paleontologist Erik N. Kjellesvig-Waering in 1948 based on fossils discovered in Lens , France). 1933 saw Ukrainian paleontologist Boris Isidorovich Chernyshev describe the species A. carbonarius based in one single specimen from
15604-476: 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
15770-582: 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
15936-656: 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
16102-434: The genus Eurypterus (among them several species today recognized as Adelophthalmus , such as the type species A. granosus , A. imhofi and A. pennsylvanicus ), he classified the new Belgian eurypterid in that genus as well. He did note that the new species was very similar to species such as E. pennsylvanicus and especially E. mansfieldi (both seen as species of Adelophthalmus today). The species name dumonti honors
16268-525: 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
16434-429: 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,
16600-412: 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
16766-587: 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 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
16932-432: 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 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
17098-429: The highly fragmentary nature of the known fossils make a precise identification difficult and problematic. Only one specimen, the anterior part of a carapace with the compound eyes placed on the margin, is known and though it does resemble Slimonia , it could also potentially be referred to Hughmilleria or even represent the carapace of Salteropterus abbreviatus (a closely related slimonid eurypterid known only from
17264-580: 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
17430-491: 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
17596-505: 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
17762-523: 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; 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
17928-497: 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
18094-443: The more elongated telson (also not as broad in the parts furthest back), thinner telson spike and a slightly different, tapering, body shape that tapers evenly the whole way instead of suddenly narrowing near the seventh segment as in S. acuminata . The type specimen of S. dubia is a badly preserved carapace, with fragments of various degrees of completion of the first eleven segments found associated. Despite its fragmentary nature,
18260-441: The naming of several junior synonyms , the apparent eyelessness of the type specimen is treated by modern researchers as a preservational artifact, and not a feature that any species of Adelophthalmus would have possessed in life. Adelophthalmus was a genus of comparatively small eurypterids, with species ranging in size from 4 cm (1.6 in, A. douvillei ) to 32 cm (12.6 in, A. khakassicus ). As of 2020, Adelophthalmus
18426-641: The only known genus of swimming eurypterids from the Middle Devonian until its extinction during the Permian, after which the few surviving eurypterids were all walking forms of the suborder Stylonurina . Fossils of Adelophthalmus have been described from four continents; North America , Europe , Asia and Australia , which indicates that Adelophthalmus might have had a nearly cosmopolitan (worldwide) distribution, one of few eurypterid genera to achieve one besides potentially Pterygotus . The territorial expansion of Adelophthalmus had begun early, with representatives found in both Siberia and Australia during
18592-507: 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 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
18758-812: The opisthosoma was covered in structures evolved from modified opisthosomal appendages. Throughout 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
18924-535: The opposite. Another Belgian species, A. corneti , was described by Pruvost in 1939 based on fossils from Quaregnon . All synonymous genera; Anthraconectes , Glyptoscorpius , Lepidoderma and Polyzosternites , were subsumed into Adelophthalmus in studies during the middle twentieth century, notably that of Belgian paleontologist Fredrik Herman van Oyen (1956). Though most authors assign all described species to Adelophthalmus , some, such as van Oyen in 1956, have considered Anthraconectes to potentially represent
19090-424: 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
19256-546: The parabolic carapace and the presence of spikes along the abdomen) place both species within Adelophthalmus . In 2013, A. piussii became the first eurypterid to be described from Italy . The specimen (specimen number MFSNgp 31681, housed at the Museo Friulano di Storia Naturale in Udine ) was collected in the gravel bank of a small creek near the greater Bombaso creek, north of the village of Pontebba and consists of
19422-552: 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
19588-433: 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
19754-434: 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,
19920-457: The preabdomen, while the second preserves five preabdominal and three postabdominal tergites; this specimen represents twice the size of the first one. The species A. oklahomensis was described by American paleontologist Carl E. Decker in 1938 based on Permian-age fossils in Oklahoma. Since the A. oklahomensis specimen was virtually identical to specimens of A. sellardsi of similar age and
20086-591: The prominent Belgian geologist André Dumont . The American geologist Amadeus William Grabau described the species Anthraconectes chinensis in 1920, based on fossils discovered in Zhaozezhuang, China. Canadian geologist Walter A. Bell described the species A. bradorensis in 1922 (as a species of Anthraconectes ) based on a single fossil recovered in New Campbelton in the Municipality of
20252-446: The pterygotids differed from genus to genus, with some (such as Pterygotus ) being found in estuaries, while other (such as Jaekelopterus ) were found in freshwater environments; Slimonia has been found in environments which appear to have been intertidal to marine, Patrick Burn Formation for example is estimated to be non-marine or marginal marine or just marine environment. Slimonia likely preyed on smaller fish, as it lacked
20418-531: The pterygotids, as well. Though the largest adelophthalmid, Adelophthalmus was, in comparison to larger apex predatory members of the group (such as Jaekelopterus ), a genus of relatively small eurypterids. The largest species of Adelophthalmus known, A. khakassicus , reached a maximum length of approximately 32 cm (12.6 in). Many species were smaller, the smallest being the Permian A. douvillei at just 4 cm (1.6 in) in length. The genus as
20584-487: The quadrangular (square) shape of the carapace and the eyes placed at its corners allowed zoologist and paleontologist Malcolm Laurie to place it within Slimonia when describing it in 1899. The size of the carapace suggests that the species would have grown to 12 cm (5 in) in length. Another species, S. stylops , was first considered a species of Pterygotus when described by John William Salter in 1859, and
20750-517: The range of the genus included water around all then existing continents. Eurypterid Eurypterids , often informally called sea scorpions , are a group of extinct arthropods that form the order Eurypterida . The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 million years ago . The group is likely to have appeared first either during
20916-452: 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
21082-445: 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
21248-458: 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
21414-435: 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
21580-405: 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
21746-413: 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
21912-429: The sixth pair of appendages were overlaid by a plate that 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
22078-451: The smaller species are known from the Carboniferous, when Adelophthalmus was the most abundant, including the "medium-sized" A. irinae (13 cm, 5.1 in) and A. moyseyi (12 cm, 4.7 in) and the smaller A. mansfieldi , A. pennsylvanicus (both at 8 cm, 3.1 in), A. approximatus (7 cm, 2.8 in) and A. dumonti (6 cm, 2.4 in). Like most eurypterids (with some exceptions, such as Slimonia and Rhinocarcinosoma ),
22244-441: 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
22410-634: The species A. waterstoni having been recovered from deposits of Frasnian (~382.2 to 372.2 million years old) age in the Gogo Formation of Western Australia , the only eurypterid with the exception of Acutiramus and Pterygotus known from the continent. The only other species of Adelophthalmus known from the Devonian is the Famennian (latest Devonian) A. lohesti , known from fossil deposits at Pont de Bonne in Liège , Belgium . Alongside
22576-529: The species Eurypterus douvillei (today seen as Adelophthalmus douvillei ) in 1890 based on fossils from Bussaco in Portugal. In 1907, Henry Woodward described Eurypterus moyseyi (today recognized as Adelophthalmus moyseyi ) based on fossils recovered from Radstock, Somerset in England. Woodward compared the singular specimen of E. moyseyi to fossil specimens of A. mansfieldi from America, finding
22742-596: The species Eurypterus wilsoni (= Adelophthalmus wilsoni ) in 1888 based on a fossil recovered by an Edward Wilson of the Bristol Museum , naming the species in his honor. The only known specimen is composed of six body segments and Woodward noted that naming the species may have been slightly premature. He noted that the specimen possessed markings and spikes running alongside the abdomen in a similar way to A. mansfieldi (then classified as Eurypterus mansfieldi ). Portuguese paleontologist Pereira de Lima described
22908-511: The specimen number MB.A. 890. Though modern researchers tend to treat the assumed eyelessness as a preservational artifact and not a feature that A. granosus would have had in life, this issue was not resolved immediately which made the naming of subsequently discovered species confusing and problematic. Lepidoderma imhofi , named in 1855 from Carboniferous-age deposits in Germany, shows definite eyes. The descriptor, Austrian paleontologist August Emanuel von Reuss , noted that Lepidoderma likely
23074-755: The specimen number PIN no. 5109/4) collected by the Krasnoyarsk Geological Expedition near Sakhapta, a village in the Nazarovsky District of the Krasnoyarsk Region of Russia . The fossils, from the Tournaisian Solomennyi Stan Formation, could confidently be assigned to Adelophthalmus based on their scalelike ornamentation, the position of their eyes and the shape of the carapace shortly after their excavation. The species
23240-476: The specimen or taxon. Pruvost had previous experience with the genus, having described the species Anthraconectes cambieri in 1930 based on fossils from Charleroi , Belgium. A. zadrai was first described formally in 1952 as Adelophthalmus zadrai , at a point in time when the type specimen was seemingly lost. The specimen was rediscovered in Berlin under a different species name based on the original collector of
23406-437: The spikes along the abdomen very similar, though noted that they were less prominent in E. moyseyi . Woodward described very large fossil specimens, the carapace alone measuring 21 cm (8.3 in) and the seven associated body segments measuring an additional 25 cm (9.8) together. Despite this, the latest available size estimates for A. moyseyi put the species at 12 cm (4.7 in) in length. A. nebraskensis
23572-427: 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
23738-498: 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
23904-534: The telson and metastoma , a large plate part of the abdomen). The fossils were recovered from deposits of Pridoli (Late Silurian) age in Herefordshire , England and suggest that the species grew to 12 cm (5 in) in length. Due to its problematic nature, S. stylops is seen as a nomen dubium by modern researchers. In 1973, another species of Slimonia was named by Kjellesvig-Waering based on one single fossil recovered by Eduardo Rodriguez from
24070-400: The total telson length) however, serrated and ending in a fine point. The largest species of Slimonia , S. acuminata , reached a maximum length of 100 cm (39 in) whilst the smallest, S. dubia , grew to 12 cm (5 in) in length. Though 100 cm is large for a predatory arthropod, Slimonia would be exceeded in length by later and more derived (more "advanced") members of
24236-468: 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
24402-414: 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
24568-400: 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
24734-465: The underside of the body in a series of folds. Like many eurypterid species, Slimonia acuminata requires a modern re-description to properly establish defining traits and characteristics. Some traits that appear to be unique to S. acuminata have been described based on specimens housed at the Doncaster Museum and Art Gallery , including rows of pustules (bulges) along the marginal rim of
24900-429: 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
25066-467: The world. The good preservation of A. pyrrhae allowed researchers to examine parts of its respiratory system , and after their study it was confirmed that even if they had a mostly aquatic lifestyle, the eurypterids could venture on to land for long periods. The adelophthalmids likely first appeared in the waters of the continent Baltica in the Late Silurian, being a part of a rapid diversification of swimming eurypterids (suborder Eurypterina) throughout
25232-657: Was A. pennsylvanicus (as Eurypterus pennsylvanicus ), by Meek and Worthen from the coal-measures of Venango County, Pennsylvania in 1877. That same year, American paleontologist James Hall described the species A. mansfieldi (under the name Eurypterus ( Dolichopterus ) mansfieldi ) based on fossils recovered in Cannelton, Pennsylvania . In 1888, Hall described the species A. approximatus (as Eurypterus approximatus ) together with American paleontologist John Mason Clarke based on fossils also recovered from Pennsylvania. The English geologist Henry Woodward described
25398-400: 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
25564-403: Was coined by German paleontologist Friedrich Goldenberg (who also named the species Polyzosternites raniceps , today recognized as A. raniceps ) in 1873 to replace the name Adelophthalmus in regards to specimens described after the type specimen in the belief that the type of Adelophthalmus represented the fossil remains of a cockroach. Glyptoscorpius was erected to include some fossils from
25730-550: Was described as Eurypterus ( Anthraconectes ) nebraskensis in 1914 by American geologist Erwin H. Barbour based on fossils recovered in Nebraska, USA. The species was described alongside other fossils from the associated sediments, which helped reinforce the idea as Adelophthalmus (or Anthraconectes ) as a freshwater animal. The species A. dumonti , Carboniferous in age, was described by Belgian paleontologist Xavier Stainier in 1915 as Eurypterus dumonti . The type specimen,
25896-509: Was described by American paleontologists Barry S. Kues and Kenneth K. Kietzke in 1981 based on 150 fossil specimens recovered from the Madera Formation of New Mexico. The large amount of specimens recovered, representing individuals at various stages of development and ontogeny, allowed detailed studies to be performed on the ontogeny and intraspecific variation within Adelophthalmus . American paleontologist Roy E. Plotnick referred
26062-505: 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
26228-432: Was excavated in 1851 by German paleontologist Hermann Jordan in a railway shaft at Jägersfreude, near Saarbrücken in Germany. This specimen was described three years later in 1854 in the work Ueber die Crustaceen der Steinkohlenformation von Saarbrücken ("Of the crustaceans of the coal formation of Saarbrücken"), written by Jordan and Hermann von Meyer and featuring descriptions of several other arthropod taxa. The fossil
26394-423: Was highly flexible laterally (side to side). As such, they theorised that the tail may have been used as a weapon. The telson spine, serrated along the sides and exceeding the flattened telson in length, ends in a sharp tip, and they proposed that it could have been capable of piercing prey. However, the Persons and Acorn theory was challenged in 2018 by James Lamsdell, David Marshall, and Derek Briggs. Even though
26560-566: Was immediately recognized by Jordan as that of a eurypterid, with both the overall shape and form and the individual parts (particularly the head and the appendages) being very similar to those of Eurypterus which had been described in the United States in 1825, 29 years earlier. Among the differences noted between the specimens were the smaller size and later age of the Saarbrücken fossil and what Jordan and von Meyer perceived to be
26726-452: 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)
26892-435: Was no apparent disarticulation in the metasoma, it was likely that the articulation seen in the postabdominal segments (which is also seen in some other eurypterid fossils, such as of Eurypterus and Alkenopterus ) would have been possible in life. Biomechanical studies on the telsons and postabdominal segments of eurypterids closely related to Slimonia , particularly those of the family Pterygotidae , had revealed that
27058-466: Was synonymous with Adelophthalmus , but ignored the rules of taxonomical priority and used his younger name due to it being based on material that he considered to be better preserved. The name Lepidoderma derives from the Latin lepidus ("elegant" or "fine") and Ancient Greek δέρμα (ðerma, "skin"). In 1868, American paleontologists Fielding Bradford Meek and Amos Henry Worthen described Anthraconectes mazonensis , Anthraconectes being designated
27224-518: 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
27390-546: Was very similar to the basal pterygotid Erettopterus in terms of visual acuity, with the number of lenses being comparable to those of Pterygotus and Jaekelopterus and possessing an IOA between 2 and 3 (which is higher than the IOA of Pterygotus and Jaekelopterus , suggesting that the visual acuity of Slimonia was good, but not as good as in the derived pterygotids). Fossils of Slimonia have been recovered in deposits home to diverse eurypterid faunas. Telychian deposits in
27556-484: Was wider and shorter than in the type species. This species was the third Silurian eurypterid in the Southern Hemisphere to be described, the other two coming from Australia . The fossil suggest a total body length of 20 centimetres (7.9 in). Slimonia is classified as part of the eurypterid family Slimonidae , within the superfamily Pterygotioidea . Historically Slimonia was first considered
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