79-408: Hibbertopteridae (the name deriving from the type genus Hibbertopterus , meaning " Hibbert 's wing") is a family of eurypterids , an extinct group of aquatic arthropods . They were members of the superfamily Mycteropoidea . Hibbertopterids were large, broad and heavy animals unlike virtually every other group of eurypterids, which are commonly streamlined and lightweight. Their bizarre morphology
158-406: A hexapodal (six-legged) gait. Although not enough fossil material is known of the other hibbertopterid eurypterids to discuss the differences between them with full confidence, Hibbertopterus is defined based on a collection of definite characteristics. The telson (the posteriormost division of the body) was hastate (e.g. shaped like a gladius , a Roman sword) and had a keel running down
237-414: A 2023 study describing a new species H. lamsdelli argued that Dunsopterus and Vernonopterus should be synonymized with Hibbertopterus , while Cyrtoctenus is distinct from it. Hibbertopterids such as Hibbertopterus were sweep-feeders, having modified spines on their forward-facing prosomal appendages that allowed them to rake through the substrate of their living environments. Though sweep-feeding
316-427: A carapace. These include Cladocera , ostracods , and isopods , but isopods only have a developed "cephalic shield" carapace covering the head. In arachnids , the carapace is formed by the fusion of prosomal tergites into a single plate which carries the eyes, ocularium, ozopores (a pair of openings of the scent gland of Opiliones ) and diverse phaneres. In a few orders, such as Solifugae and Schizomida ,
395-402: A central groove. The slow progression and dragging of the tail indicate that the animal responsible was moving out of water. The presence of terrestrial tracks indicate that Hibbertopterus was able to survive on land at least briefly, possible due to the probability that their gills could function in air as long as they remained wet. Additionally, some studies suggest that eurypterids possessed
474-523: A century later, combines his name and the Greek word πτερόν ( pteron ) meaning "wing". Hibbertopterus was the largest eurypterid within the stylonurine suborder, with the largest fossil specimens suggesting that H. scouleri could reach lengths around 180–200 centimetres (5.9–6.6 ft). Though this is significantly smaller than the largest eurypterid overall, Jaekelopterus , which could reach lengths of around 250 centimetres (8.2 ft), Hibbertopterus
553-567: A different feeding method altogether. As such, it is more than possible that later ontogenetic stages of Hibbertopterus developed the structures seen in Cyrtoctenus to be able to continue to feed at larger body sizes. Fossil specimens of Hibbertopterus frequently occur together with fragments referred to Cyrtoctenus , Dunsopterus and Vernonopterus . The three fragmentary genera were suggested to by synonyms of each other by American paleontologist James Lamsdell in 2010, which would have meant
632-536: A distinct eurypterid genus, Vernonopterus . Størmer and Waterston concluded that the Glyptoscorpius species G. caledonicus was to be part of a new genus, which they named Cyrtoctenus (the name deriving from the Greek Cyrtoctenos , a curved comb) and they named a new species, C. peachi (named in honour of Ben Peach), as its type. Both of these species were based on fragmentary fossil remains. Furthermore,
711-581: A dual respiratory system , which would allow short periods of time in terrestrial environments. In the Midland Valley of Scotland, 27 kilometres (16.8 miles) to the west of Edinburgh , East Kirkton Quarry contains deposits that were once a freshwater lake near a volcano. The locality has preserved a diverse fauna of the Viséan age of the Carboniferous (about 335 million years ago). Other than H. scouleri ,
790-481: A feature they shared with their entire suborder, the Stylonurina . Hibbertopterids fed using a method referred to as sweep-feeding, in which the animal would rake through the soft sediment of their substrate with specialised blades on their forward-facing appendages to capture small invertebrates. Though this method of feeding was present in other mycteropoids and in stylonuroids , it was at its most advanced stage within
869-425: A hastate telson similar to that of Hibbertopterus , ornamentation consisting of scales or other similar structures on the exoskeleton, the fourth pair of appendages possessing spines, the more posterior tergites of the abdomen possessing tongue-shaped scales near their edges and there being lobes positioned posterolaterally (posteriorly on both sides) on the prosoma. Historically, the morphology of Hibbertopterus and
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#1733092664951948-499: A large and open fresh to brackish water lake, with possibly occasional influences by storms and glacial processes, fossil remains recovered is most commonly that of various types of fish. Among these types are palaeoniscoids , sharks and acanthodians . Though shark material is too fragmentary to be identifiable, at least some fossils might represent the remains of protacrodontoids . Among the acanthodians, at least three genera have been identified from fossil scales and spines, including
1027-553: A ring-like shape of hardened integument (absent in Campylocephalus ). The eyes of Hibbertopterus are also located near the center of the head whereas those of Campylocephalus are located further back. The generic name Hibbertopterus was selected to honor the original descriptor of H. scouleri , Samuel Hibbert. The fact that Glyptoscorpius was questionable at best and that its type species, G. perornatus , (and other species, such as G. kidstoni ) had recently been referred to
1106-460: A size of 140 centimetres (4.6 feet) and at 180–200 centimetres (5.9–6.6 ft), Hibbertopterus scouleri was the largest eurypterid in the entire stylonurine suborder. That hibbertopterids were so broad and compact probably means they were the overall heaviest eurypterids, surpassing longer forms, such as the light-weight pterygotids , in weight. Compared to other eurypterids, hibbertopterids were highly unusual. Their broad and heavy bodies go against
1185-483: A stretch of land, dragging its telson (the posteriormost division of its body) across the ground after it. How Hibbertopterus could survive on land, however briefly, is unknown but it might have been possible through either its gills being able to function in air as long as they were wet or by the animal possessing a dual respiratory system , theorised to have been present in at least some eurypterids. Though sometimes, and often historically, treated as distinct genera,
1264-813: Is a genus of eurypterid , a group of extinct aquatic arthropods . Fossils of Hibbertopterus have been discovered in deposits ranging from the Devonian period in Belgium , Scotland and the United States to the Carboniferous period in Scotland, Ireland , the Czech Republic and South Africa . The type species, H. scouleri , was first named as a species of the significantly different Eurypterus by Samuel Hibbert in 1836. The generic name Hibbertopterus , coined more than
1343-473: Is also supported by the complete lack of adaptations towards any organs used for trapping prey in younger specimens (though they are present on adult specimens once referred to Cyrtoctenus ) and a lack of swimming adaptations. Through sweep-feeding, Hibbertopterus could sweep up small animals from the soft sediments of shallow bodies of water, presumably small crustaceans and other arthropods, and could then sweep them into its mouth when it detected them. Through
1422-400: Is highly problematic; some of the diagnostic characteristics used when describing it are either questionable or outright meaningless. For instance, the original description had been based on G. caledonicus and G. perornatus but since the parts of the body preserved in the fossils described don't completely overlap it is impossible to say if Peach's diagnostic characteristics actually apply to
1501-485: Is likely to have been the heaviest due to its broad and compact body. Furthermore, trackway evidence indicates that the South African species H. wittebergensis might have reached lengths similar to Jaekelopterus . Like many other stylonurine eurypterids, Hibbertopterus fed through a method called sweep-feeding. It used its specialised forward-facing appendages (limbs), equipped with several spines, to rake through
1580-620: Is quite similar to filter feeding . This has led some researchers to suggest that Hibbertopterus would have been a pelagic animal, as modern filter feeding crustaceans, but the robust and massive nature of the genus (in contrast to modern filter feeding crustaceans which are typically very small) makes such a conclusion unlikely. The chelicerae (pincers) of Hibbertopterus were weak and they would not have been able to grasp any potential prey which means Hibbertopterus would probably have been incapable of preying on larger animals. The conclusion that Hibbertopterus wasn't preying on large animals
1659-667: Is so unusual that they in the past have been thought to represent an entirely distinct order of chelicerates . Fossils of the family first appear in deposits of Middle Devonian age and the last known fossils representing hibbertopterids are known from deposits of Late Permian age. The hibbertopterids represent the last known living eurypterids, going extinct during the Permian–Triassic extinction event or shortly before. Although eurypterids are commonly known as "sea scorpions", hibbertopterids inhabited freshwater swamps and rivers and were unable to swim since they lacked swimming paddles,
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#17330926649511738-413: Is the presence of grooves on its podomeres, which studies on Drepanopterus suggest might have been a feature which appeared late in an animal's life cycle. Differences in the positions of the eyes in specimens of Hibbertopterus and Cyrtoctenus is not surprising as movements of the eyes through ontogeny has been described in other eurypterid genera. Lamsdell considered it almost certain that Dunsopterus
1817-399: Is yet to be published. In 1831, Scottish naturalist John Scouler described the remains, consisting of a massive and unusual prosoma (head) and several tergites (segments from the back of the animal), of a large and strange arthropod discovered in deposits in Scotland of Lower Carboniferous age, but did not assign a name to the fossils. Through Scouler's examination, the fossils represent
1896-524: The Opiliones . The site also preserves abundant plant life, including the genera Lepidodendron , Lepidophloios , Stigmaria and Sphenopteris . Locally, the strange fossil carapaces of H. scouleri have been given the common name "Scouler's heids" ("heid" being Scots for "head"). The Waaipoort Formation, where H. wittebergensis has been discovered, also preserves a diverse Carboniferous fauna and some species of plants. Interpreted as having been
1975-442: The substrate of the environments in which it lived in search for small invertebrates to eat, which it could then push towards its mouth. Though long hypothesised, the fact that eurypterids were capable of terrestrial locomotion was definitely proven through the discovery of a fossil trackway made by Hibbertopterus in Scotland. The trackway showed that an animal measuring around 160 centimetres (5.2 ft) had slowly lumbered across
2054-443: The "cyrtoctenids" were definitely Hibbertopterus -type eurypterids, not representatives of a new order of arthropods. Hibbertopterus is classified as part of the family Hibbertopteridae, which it also lends its name to, a family of eurypterids within the superfamily Mycteropoidea , alongside the genera Campylocephalus and Vernonopterus . The hibbertopterids are united as a group by being large mycteropoids with broad prosomas,
2133-630: The 10 species 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. The distinguishing features of H. caledonicus , H. dewalquei , H. ostraviensis and H. peachi follow the 1968 description of these species. The descriptors, Norwegian paleontologist Leif Størmer and British paleontologist Charles D. Waterston, did not consider these species to represent eurypterids, though any emended diagnosis of them
2212-412: The actual mortalities, susceptible to scavengers . In a 2019 graduate thesis , American geologist Emily Hughes suggested the synonymization of Hibbertopterus and Dunsopterus due to the "strong morphological similarities" between them, and as Dunsopterus was found to be paraphyletic in regards to Cyrtoctenus , all three were subsumed into just Hibbertopterus . In particular, she noted that though
2291-425: The carapace may be subdivided. In Opiliones, some authors prefer to use the term carapace interchangeably with the term cephalothorax, which is incorrect usage, because carapace refers only to the dorsal part of the exoskeleton of the cephalothorax. Alternative terms for the carapace of arachnids and their relatives, which avoids confusion with crustaceans, are prosomal dorsal shield and peltidium . The carapace
2370-493: The derived climatiiform Gyracanthides . Among the palaeoniscoids, eight distinct genera have been identified. Several of these palaeoniscoid genera also occur in deposits of similar age in Scotland. Other than H. wittebergensis , the only known invertebrates are two rare species of bivalves , possibly representing unionids . Plant fossils in the Waaiport Formation are notably less diverse than those of preceding ages in
2449-487: The derived Hibbertopteridae. The hibbertopterids were the largest of all stylonurine eurypterids, with both Hibbertopterus at 180–200 centimetres (5.9–6.6 ft) and Campylocephalus at 140 centimetres (4.6 feet) representing giant eurypterids in their own right. Though longer eurypterids are known from the eurypterine suborder, notably the largest known arthropod of all time, Jaekelopterus , at 230–260 centimetres (7.5–8.5 ft), hibbertopterids were far bulkier than any of
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2528-449: The different adaptations of juveniles and adults (" Cyrtoctenus "), individuals of different ages would possibly have preferred different types of prey, which would have reduced competition between members of the same genus. A fossil trackway discovered near St Andrews in Fife , Scotland, reveals that Hibbertopterus was capable of at least limited terrestrial locomotion . The trackway found
2607-518: The end of each limb was covered with sensory organs. These adaptations suggest that Hibbertopterus , like other hibbertopterids, would have fed by a method referred to as sweep-feeding, using its limbs to sweep through the substrate of its environment in search for food. The fourth pair of appendages, though used in feeding like the second and third pairs, was also used for locomotion and the two final pairs of legs (pairs five and six overall) were solely locomotory. As such, Hibbertopterus would have used
2686-708: The family monotypic (containing only one immediately subordinate taxon), though the highly incomplete nature of their remains again makes that hypothesis impossible to confirm. The cladogram below is adapted from Lamsdell (2012), collapsed to only show the superfamily Mycteropoidea. Drepanopterus pentlandicus Drepanopterus abonensis Drepanopterus odontospathus Woodwardopterus scabrosus Mycterops mathieui Hastimima whitei Megarachne servinei Campylocephalus oculatus Hibbertopterus scouleri Hibbertopterus wittebergensis The hibbertopterids were derived sweep-feeders, inhabiting freshwater swamps and rivers and feeding by raking through
2765-406: The fauna includes several terrestrial animals, such as anthracosaurs , aistopods , baphetids and temnospondyls , representing some of the oldest known terrestrial tetrapods . Several terrestrial invertebrates are also known from the location, including several species of millipedes , Gigantoscorpio (one of the earliest scorpions proven to have been terrestrial) and early representatives of
2844-534: The feeding appendages were different, the ornamentation and form of the raking tools seen in Hibbertopterus were probably the precursors of the more moveable finger-like organs present in Cyrtoctenus . Hughes suggested that Vernonopterus , due to its distinct ornamentation, represented a genus distinct from Hibbertopterus . The same conclusions and suggestions were also published in a later 2020 conference abstract, co-authored by Hughes and James Lamsdell. However,
2923-481: The food masticatory process being assumed by the laden (plates overlaying the coxae). Some of its species have even further adaptations towards sweep-feeding than other mycteropoids, with its blades modified into comb-like rachis that could entrap smaller prey or other organic food particles. With its coxae being large, it is likely that some species of Hibbertopterus would also feed on relatively large invertebrates when able to. Hibbertopterus Hibbertopterus
3002-400: The fossil remains of a eurypterid by American paleontologist James Hall in 1884, three years later. Though Hall assigned the species to Stylonurus , that same year British paleontologists Henry Woodward and Thomas Rupert Jones assigned the fossil to the genus Echinocaris , believing the fossils represented a phyllocarid crustacean . The assignment to Echinocaris was probably based on
3081-635: The fossils were given due to their fragmentary nature. Though no specification was given as to why, Pterygotus hibernicus (a species described from Ireland by British paleontologist William Hellier Baily in 1872) was reassigned to Hibbertopterus by American paleontologist Erik N. Kjellesvig-Waering in 1964 as part of a greater re-examination of the various species assigned to the family Pterygotidae. Kjellesvig-Waering retained P. dicki as part of Pterygotus . Scottish paleontologists Lyall I. Anderson and Nigel H. Trewin and German paleontologist Jason A. Dunlop noted in 2000 that Kjellesvig-Waerings acception of
3160-431: The general eurypterid trend of being streamlined and lightweight and like all other stylonurine eurypterids, they lack swimming paddles. Out of their six pairs of limbs, the second, third and fourth pairs were forward-facing and specialised for gathering food. The leg segments of these limbs were covered with long spines and their ends were covered with sensory organs. The fourth pair of limbs, although also used in feeding,
3239-407: The genus Adelophthalmus prompted Norwegian paleontologist Leif Størmer and British paleontologist Charles D. Waterston to in 1968 re-examine the various species that had been referred to it. Because G. perornatus was the type species of Glyptoscorpius , the genus itself became synonymous with Adelophthalmus . That same year, the species G. minutisculptus had been designated the type species of
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3318-841: The genus Cyrtoctenus (where H. peachi is the type species). The idea that Dunsopterus and Cyrtoctenus were congeneric (e.g. synonymous) was first suggested by British geologist Charles D. Waterston in 1985. Dunsopterus is known from very fragmentary material, mainly sclerites (various hardened body parts) which have little diagnostic potential and are poorly known in fossils attributed to Cyrtoctenus . The morphology of fossils attributed to Dunsopterus and Cyrtoctenus does suggest that they were more specialised than H. scouleri , particularly in their adaptations to sweep-feeding. If valid, Cyrtoctenus would have had further adaptations towards sweep-feeding than any other hibbertopterid, with its blades modified into comb-like rachis that could entrap smaller prey or other organic food particles. It
3397-432: The head) of Campylocephalus is slightly narrower and is broadest at its midsection, rather than at the part which connects to the rest of the body (as it is in Hibbertopterus ). The fragmentary Vernonopterus can be distinguished from the others by its distinctive and unique ornamentation. Preserved cuticle of hibbertopterids is thinner than what is expected of arthropods of their size, though this might be explained by
3476-463: The hibbertopterid eurypterids Cyrtoctenus and Dunsopterus have been suggested to represent adult ontogenetic stages of Hibbertopterus . The features of fossils associated with these genera suggest that the sweep-feeding strategy of Hibbertopterus changed significantly over the course of its life, from simpler raking organs present in younger specimens to specialised comb-like organs capable of trapping prey (rather than simply pushing it towards
3555-540: The highly incomplete nature of their remains again makes that hypothesis impossible to confirm. The cladogram below is adapted from Lamsdell (2012), collapsed to only show the superfamily Mycteropoidea. Drepanopterus pentlandicus Drepanopterus abonensis Drepanopterus odontospathus Woodwardopterus scabrosus Mycterops mathieui Hastimima whitei Megarachne servinei Campylocephalus oculatus Hibbertopterus scouleri Cyrtoctenus wittebergensis Many analyses and overviews treat
3634-461: The larger size of the specimens referred to Cyrtoctenus . The method of Hibbertopterus , which involves raking, would have become significantly less effective the larger the animal grew since a larger and larger portion of its prey would be small enough to pass between its sweep-feeding spines. Any specimen over the size of a metre (3.2 ft) which continued to feed on small invertebrates would need modified sweep-feeding appendages or would need to employ
3713-460: The largest eurypterine eurypterids and as such likely represent the overall heaviest animals in the order. Hibbertopterids were large mycteropoid eurypterids characterised by their broad prosomas (heads), hastate (e.g. shaped like a gladius , a Roman sword) telsons (which were the posteriormost division of the body) with paired keels and a covering of ornamentation in the shape of scales across their exoskeletons . More shared features are
3792-426: The middle, with in turn had a small indentation in its own centre. The walking legs of Hibbertopterus had extensions at their base and lacked longitudinal posterior grooves in all of its podomeres (leg segments). Some of these characteristics, in particular the shape of the telson, are thought to have been shared by other hibbertopterids, which are much less well preserved than Hibbertopterus itself. The status of
3871-644: The modern consensus is that they represent ontogenetic stages (different developmental stages of the animal throughout its life) of Hibbertopterus . The genus Hastimima , sometimes classified as part of the Hibbertopteridae, has been recovered as part of the Mycteroptidae (the closest relatives of the hibbertopterids) in recent analyses. The morphology of the hibbertopterids was so unusual that they have been thought to be an order separate to Eurypterida. Recent work however confirms them to be derived members of
3950-465: The mouth) in adults. Like other known hibbertopterid eurypterids , Hibbertopterus was a large, broad-bodied and heavy animal. It was the largest known eurypterid of the suborder Stylonurina , composed of those eurypterids that lacked swimming paddles. A carapace (the part of the exoskeleton which covered the head) referred to the species H. scouleri , from Carboniferous Scotland , measures 65 centimetres (26 in) wide. Since Hibbertopterus
4029-452: The oldest name, Dunsopterus , taking priority and subsuming both Cyrtoctenus and Vernonopterus as junior synonyms . Following studies on the ontogeny of Drepanopterus , a more primitid mycteropoid eurypterid, large-scale changes in the developments of the appendages over the course of the life of a single animal have been proven to have happened in some eurypterids. One of the key features distinguishing Cyrtoctenus from Hibbertopterus
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#17330926649514108-419: The original designation for Pterygotus dicki was "burdensome" as it is based on highly fragmentary material. They noted that like many other pterygotid species, P. dicki represented yet another name applied to some scattered segments, a practice they deemed "taxonomically unsound". Though they suggested that further research was required to determine whether or not the taxon was valid at all, they did note that
4187-502: The other hibbertopterids has been seen as so unusual that they have been thought to be an order separate from Eurypterida . The features of Campylocephalus and Vernonopterus makes it clear that both genera represent hibbertopterid eurypterids, but the incomplete nature of all fossil specimens referred to them make any further study of the precise phylogenetic relationships within the Hibbertopteridae difficult. Both genera could even represent synonyms of Hibbertopterus itself, though
4266-442: The possibility that only an outer exocuticular region has been preserved in their fossils. The hibbertopterids are classified as part of the superfamily Mycteropoidea within the eurypterid suborder Stylonurina. The family includes the three genera Campylocephalus , Hibbertopterus and Vernonopterus . Up until recently the two genera Cyrtoctenus and Dunsopterus were also recognised as valid and distinct hibbertopterid genera, but
4345-404: The presence of a fringe to the segments formed by their ornamentation was absent in all other species of Pterygotus , but "strikingly similar" to what was present in Cyrtoctenus . Subsequent research treated P. dicki as a species of Cyrtoctenus . When Kjellesvig-Waering designated the genus Hibbertopterus in 1959, Eurypterus scouleri had already been referred to (considered a species of)
4424-516: The presence of eurypterid-type tergites, Størmer and Waterston thought that the Cyrtoctenus fossils represented remains of a new order of aquatic arthropods which they dubbed "Cyrtoctenida". The species C. dewalquei had originally been described as the fragmentary remains of a eurypterid in 1889 was assigned to Cyrtoctenus on the basis of the perceived filaments present on its appendages, similar to those of C. peachi . Størmer and Waterston disregarded specimens referred to C. caledonicus other than
4503-532: The presence of tongue-shaped scales on the margins of the tergites of the opisthosoma (the abdomen) and that the fourth pair of appendages were covered in spines. The prosoma of the hibbertopterids possessed lobes that were positioned posterolaterally ( posteriorly on both sides). Although Vernonopterus has been estimated to have reached lengths of "just" 50 centimetres (19.7 inches), both Campylocephalus and Hibbertopterus represent true giant eurypterids. The largest specimens of Campylocephalus suggests
4582-572: The prosoma, the telson and several tergites, but also coxae and even part of the digestive system. The discovery was also important for eurypterid research in general, since it represents one of the few eurypterids known from the southern hemisphere , where eurypterid finds are rare and usually fragmentary. The presence of the gut in the fossil proves that the specimen represents a dead individual, and not only exuviae , and scientists examining it could conclude that it had been preserved as lying on its back. The description of H. wittebergensis affirmed that
4661-467: The related Campylocephalus for some time. Kjellesvig-Waering recognised Campylocephalus scouleri as distinct from the type species of that genus, C. oculatus , in that the prosoma of Campylocephalus was more narrow, had a subelliptical (almost elliptical) shape and had its widest point in the middle rather than at the base. Further differences were noted in the position and shape of the animal's compound eyes, which in Hibbertopterus are surrounded by
4740-483: The same location, possibly because of climate reasons. Among the genera present are the common Praeramunculus (possibly representing a progymnosperm ) and Archaeosigillaria (a small type of lycopod ). Carapace A carapace is a dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods , such as crustaceans and arachnids , as well as vertebrates, such as turtles and tortoises . In turtles and tortoises,
4819-404: The second eurypterid to be scientifically studied, just six years after the 1825 description of Eurypterus itself. Five years later, in 1836, British geologist Samuel Hibbert redescribed the same fossil specimens, giving them the name Eurypterus scouleri . The eurypterid genus Glyptoscorpius was named by British geologist Ben Peach , who also named the species G. perornatus (treated as
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#17330926649514898-466: The sediments and thus entangling anything in their way. Mycteropoidea show even more extreme adaptations towards a sweep-feeding lifestyle. These adaptations are taken to an even further extreme within the Hibbertopteridae, with appendage IV possessing a blade alongside the appendages II-III (which also have blades in other hibbertopteroids). The coxae in Hibbertopterus are reduced, leading to part of
4977-537: The slightly spinose surface of the fossils, but in 1888 Hall and American paleontologist John Mason Clarke pointed out that no described Echinocaris actually had spines similar to what Woodward and Jones suggested and as such, reassigned the species back to Stylonurus , interpreting the fossils as fragments of the long walking legs. An assignment to Stylonurus was affirmed by Clarke and American paleontologist Rudolf Ruedemann in their influential The Eurypterida of New York in 1912, though no distinguishing features of
5056-632: The soft sediment with blades on their anterior appendages to capture small invertebrates. Sweep-feeding strategies evolved independently in two of the four stylonurine superfamilies, the Stylonuroidea and the Mycteropoidea . In both superfamilies, the adaptations to this lifestyle involves modifications to the spines on their anterior prosomal appendages for raking through the substrate of their habitats. Stylonuroids have fixed spines on appendages II-IV which could have been used as dragnets to rake through
5135-726: The species G. stevensoni , named in 1936, was referred to the new genus Dunsopterus . The key diagnostic feature of Cyrtoctenus was its comb-like first appendages. Waterston remarked in another 1968 paper that the "controversial" Stylonurus wrightianus was similar to the unusual and massive prosomal appendage of Dunsopterus and as such reassigned S. wrightianus to Dunsopterus , creating Dunsopterus wrightianus . Other than C. peachi and C. caledonicus , further species were added to Cyrtoctenus by Størmer and Waterston; Eurypterus dewalquei , described in 1889, and Ctenopterus ostraviensis , described in 1951, became Cyrtoctenus dewalquei and C. ostraviensis , respectively. Despite noting
5214-545: The species H. wittebergensis from South Africa indicates an animal around 250 centimetres (8.2 ft) in length (the same size attributed to the largest known eurypterid, Jaekelopterus ), though the largest known fossil specimens of the species only appear to have reached lengths of 135 centimetres (4.43 ft). The forward-facing appendages (limbs) of Hibbertopterus (pairs 2, 3 and 4) were specialised for gathering food. The distal podomeres (leg segments) of these three pairs of limbs were covered with long spines, and
5293-542: The suborder Stylonurina, closely related to Drepanopterus and the Mycteroptidae. The features of genera Campylocephalus and Vernonopterus makes it clear that both genera represent hibbertopterid eurypterids, but the incomplete nature of all fossil specimens referred to them make any further study of the precise phylogenetic relationships within the Hibbertopteridae difficult. Both genera could even represent further synonyms of Hibbertopterus itself, which would make
5372-458: The ten species assigned to Hibbertopterus as composing three separate, but closely related, hibbertopterid genera. In these arrangements, Hibbertopterus is typically restricted to the species H. scouleri and H. hibernicus , with the species H. stevensoni being the type and only species of the genus Dunsopterus and the species H. caledonicus , H. dewalquei , H. dicki , H. ostraviensis , H. peachi and H. wittebergensis being referred to
5451-463: The two original species. Though only represented by two small, jointed and vaguely cylindrical fossil fragments (both discovered in the Portage sandstones of Italy, New York ), the species today recognised as H. wrightianus has had a complicated taxonomic history. Originally described in 1881 as a species of plant, the fragmentary fossil referred to as " Equisetides wrightiana " was noted to represent
5530-724: The type species of Glyptoscorpius by later researchers although it had not originally been designated as such) in 1882. The genus was based on G. perornatus and the fragmentary species G. caledonicus , previously described as the plant Cycadites caledonicus by English paleontologist John William Salter in 1863. This designation was reinforced with more fossil fragments discovered in the Coomsdon Burn , which Peach referred to Glyptoscorpius caledonicus . In 1887 Peach described G. minutisculptus from Mount Vernon , Glasgow , and G. kidstoni from Radstock in Somerset . Peach's Glyptoscorpius
5609-415: The underside is called the plastron . In crustaceans , the carapace functions as a protective cover over the cephalothorax (i.e., the fused head and thorax , as distinct from the abdomen behind). Where it projects forward beyond the eyes, this projection is called a rostrum . The carapace is calcified to varying degrees in different crustaceans. Zooplankton within the phylum Crustacea also have
5688-409: The unique fragmentary type specimen, which at this point had been plastically preserved in sandstone. Like C. caledonicus , C. ostraviensis was also known only from a single specimen, a fragment of an appendage described in 1951. No distinguishing features were given for the species, and the authors noted that it was possibly synonymous with C. peachi , but they chose to maintain it as distinct due to
5767-473: The very limited fossil material. Known from a single specimen described in 1985, H. wittebergensis (described as Cyrtoctenus wittebergensis ) is the only species of Hibbertopterus known from reasonably complete remains other than the type species itself. The fossil, discovered in the Waaipoort Formation near Klaarstroom , Cape Province , South Africa , is remarkably complete, preserving not only
5846-514: Was a junior synonym of Hibbertopterus and that Cyrtoctenus and Vernonopterus in turn represented junior synonyms of Dunsopterus , which would subsume all three into Hibbertopterus . Synonymizing Hibbertopterus with Cyrtoctenus and Dunsopterus would also explain why smaller Hibbertopterus specimens are more complete than the known fossil remains of Cyrtoctenus , often fragmentary. The majority of Hibbertopterus specimens would then represent exuviae whilst Cyrtoctenus specimens represent
5925-416: Was also used for locomotion, as were pairs five and six. As such, hibbertopterids would have been hexapods (walking on six legs). Due to the fragmentary nature of both Campylocephalus and Vernonopterus , confidently establishing distinguishing features between the three genera is difficult. Distinguishing Campylocephalus from Hibbertopterus is primarily the fact that the carapace (exoskeleton covering
6004-409: Was roughly 6 metres (20 ft) long and 1 metre (3.3 ft) wide, and suggests that the eurypterid responsible was 160 centimetres (5.2 ft) long, consistent with other giant sizes attributed to Hibbertopterus . The tracks indicate a lumbering, jerky and dragging movement. Scarps with crescent-shapes were left by the outer limbs, inner markings were made by the keeled belly and the telson carved
6083-452: Was suggested as early as 1993 by American paleontologist Paul Selden and British paleontologist Andrew J. Jeram that these adaptations might not have been due to Dunsopterus and Cyrtoctenus representing more derived genera of hibbertopterids, but rather due to both genera perhaps representing adult forms of Hibbertopterus . In this case, the development of the more specialized sweep-feeding method of Cyrtoctenus can directly be explained by
6162-587: Was unusually wide relative to its length for a eurypterid, the animal in question would probably have measured around 180–200 centimetres (5.9–6.6 ft) in length. Even though there were eurypterids of greater length (such as Jaekelopterus and Carcinosoma ), Hibbertopterus was very deep-bodied and compact in comparison to other eurypterids and the mass of the specimen in question would likely have rivalled that of other giant eurypterids (and other giant arthropods), if not surpassed them. In addition to fossil finds of large specimens, fossil trackways attributed to
6241-482: Was used as a strategy by many genera within the Stylonurina, it was most developed within the hibbertopterids, which possessed blades on the second, third and fourth pair of appendages. Inhabiting freshwater swamps and rivers, the diet of Hibbertopterus and other sweep-feeders was probably composed of what they could find raking through its living environment, likely primarily small invertebrates. This method of feeding
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