Hibbertopterus - Knowledge

1617: 1640: 2284: 1428: 134: 155: 1290: 1875: 180: 4396: 687: 2628: 765: 4699: 2416:, 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 a different feeding method altogether. As such, it is more than possible that later 2716:. 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 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 1907:, 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 1331:(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 the second eurypterid to be scientifically studied, just six years after the 1825 description of 1537:

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 the presence of a fringe to the segments formed by their

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has been discovered, also preserves a diverse Carboniferous fauna and some species of plants. Interpreted as having been 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

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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

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The status of 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.

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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 was used as a strategy by many genera within the Stylonurina, it was most developed within the hibbertopterids,

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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

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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

1850:, is remarkably complete, preserving not only 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 863:

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 is yet to be published.

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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 the different adaptations of juveniles and adults

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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,

2480:, 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 735:

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

2712:. The trackway found 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 677:

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 the mouth) in adults.

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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

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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 a dual

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wasn't preying on large animals 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

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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.

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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

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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.

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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 the two original species.

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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

2863:. Plant fossils in the Waaiport Formation are notably less diverse than those of preceding ages in the same location, possibly because of climate reasons. Among the genera present are the common 1416:

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

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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

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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 is quite similar to

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Tetlie, O. E. (2008). "Hallipterus excelsior, a Stylonurid (Chelicerata: Eurypterida) from the Late Devonian Catskill Delta Complex, and Its Phylogenetic Position in the Hardieopteridae".

1529:. Scottish paleontologists Lyall I. Anderson and Nigel H. Trewin and German paleontologist Jason A. Dunlop noted in 2000 that Kjellesvig-Waerings acception of the original designation for 3556:"Redescription of Drepanopterus pentlandicus Laurie, 1892, the earliest known mycteropoid (Chelicerata: Eurypterida) from the early Silurian (Llandovery) of the Pentland Hills, Scotland" 1521:

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

2599:. The same conclusions and suggestions were also published in a later 2020 conference abstract, co-authored by Hughes and James Lamsdell. However, a 2023 study describing a new species 994:

is too limited to confidently establish any distinguishing features, though it can be confidently be assigned to the genus based on its "striking similarities" to the other species.

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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

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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

2851:. 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 2458:. The three fragmentary genera were suggested to by synonyms of each other by American paleontologist James Lamsdell in 2010, which would have meant the oldest name, 2392:

It 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

1854:, 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 791:(leg segments) of these three pairs of limbs were covered with long spines, and the end of each limb was covered with sensory organs. These adaptations suggest that 2693:"), individuals of different ages would possibly have preferred different types of prey, which would have reduced competition between members of the same genus. 1835: 638:

in Scotland. The trackway showed that an animal measuring around 160 centimetres (5.2 ft) had slowly lumbered across a stretch of land, dragging its

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are the large number filaments on its first pair of appendages and the longer filaments on the second pair of appendages, which also have large fulcra.

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is not surprising as movements of the eyes through ontogeny has been described in other eurypterid genera. Lamsdell considered it almost certain that

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Although not enough fossil material is known of the other hibbertopterid eurypterids to discuss the differences between them with full confidence,

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Evans, Francis John (1999). "Palaeobiology of Early Carboniferous lacustrine biota of the Waaipoort Formation (Witteberg Group), South Africa".

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from South Africa indicates an animal around 250 centimetres (8.2 ft) in length (the same size attributed to the largest known eurypterid,

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Laurie, 1892, the earliest known mycteropoid (Chelicerata: Eurypterida) from the early Silurian (Llandovery) of the Pentland Hills, Scotland"

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is the precise arrangement of lunules (crescent-shaped markings) on said leg segments, forming rows. This is different from, for an example,

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could reach lengths around 180–200 centimetres (5.9–6.6 ft). Though this is significantly smaller than the largest eurypterid overall,

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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

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Waterston, Charles D.; Størmer, Leif (1968). "IV. Cyrtoctenus gen. nov., a large late Palaeozoic Arthropod with pectinate Appendages*".

1720:(named in honour of Ben Peach), as its type. Both of these species were based on fragmentary fossil remains. Furthermore, the species 2583:. In particular, she noted that though the feeding appendages were different, the ornamentation and form of the raking tools seen in 1438:

Though only represented by two small, jointed and vaguely cylindrical fossil fragments (both discovered in the Portage sandstones of

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has had a complicated taxonomic history. Originally described in 1881 as a species of plant, the fragmentary fossil referred to as "

4749: 761:), though the largest known fossil specimens of the species only appear to have reached lengths of 135 centimetres (4.43 ft). 3914:. Geological Society of America Special Papers. Vol. 244. Geological Society of America Special Publication. pp. 13–24. 3906:

Rolfe, W. D. I.; Durant, G. P.; Fallick, A. E.; Hall, A. J.; Large, D. J.; Scott, A. C.; Smithson, T. R.; Walkden, G. M. (1990).

1903:. The hibbertopterids are united as a group by being large mycteropoids with broad prosomas, a hastate telson similar to that of 17: 2647:

which possessed blades on the second, third and fourth pair of appendages. Inhabiting freshwater swamps and rivers, the diet of

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can be distinguished from other species by the oval shape of its ocellar node (the raised portion of the carapace on which the

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Size estimate is based on a complete carapace. As the type species, no particular distinguishing features are established for

4475: 4465: 3987: 3341:"Cyrtoctenus wittebergensis sp. nov. (Chelicerata: Eurypterida), a large sweep-feeder from the Carboniferous of South Africa" 795:, like other hibbertopterids, would have fed by a method referred to as sweep-feeding, using its limbs to sweep through the 3288: 3050: 829:

sword) and had a keel running down the middle, with in turn had a small indentation in its own centre. The walking legs of

2842:. Among the acanthodians, at least three genera have been identified from fossil scales and spines, including the derived 2283: 1888:

is classified as part of the family Hibbertopteridae, which it also lends its name to, a family of eurypterids within the

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representing more derived genera of hibbertopterids, but rather due to both genera perhaps representing adult forms of

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other than the unique fragmentary type specimen, which at this point had been plastically preserved in sandstone. Like

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Kjellesvig-Waering, Erik N. (1964). "A Synopsis of the Family Pterygotidae Clarke and Ruedemann, 1912 (Eurypterida)".

1639: 4442: 3927: 926:) of its second pair of appendages and the presence of small cone-shaped fulcra (supportive tissue) along the limbs. 2838:. Though shark material is too fragmentary to be identifiable, at least some fossils might represent the remains of 1533:

was "burdensome" as it is based on highly fragmentary material. They noted that like many other pterygotid species,

2369:(various hardened body parts) which have little diagnostic potential and are poorly known in fossils attributed to 1911:

and the other hibbertopterids has been seen as so unusual that they have been thought to be an order separate from

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Fragmentary fossils known from Scotland. Known primarily from leg segments, the primary distinguishing feature of

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itself, though the highly incomplete nature of their remains again makes that hypothesis impossible to confirm.

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fossils represented remains of a new order of aquatic arthropods which they dubbed "Cyrtoctenida". The species

1786:, respectively. Despite noting the presence of eurypterid-type tergites, Størmer and Waterston thought that the 1482:

was probably based on the slightly spinose surface of the fossils, but in 1888 Hall and American paleontologist

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The lower size estimate follows known fossil evidence. The higher size estimate derives from trackway evidence.

4833: 4828: 4460: 4450: 4404: 2956:"Cope's rule and Romer's theory: patterns of diversity and gigantism in eurypterids and Palaeozoic vertebrates" 4422: 4417: 3517:

Tollerton, V P (1989). "Morphology, Taxonomy, and Classification of the Order Eurypterida Burmeister, 1843".

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actually had spines similar to what Woodward and Jones suggested and as such, reassigned the species back to

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by later researchers although it had not originally been designated as such) in 1882. The genus was based on

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Isolated podomeres of a prosomal appendage have been discovered in the United States. The fossil material of

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The cladogram below is adapted from Lamsdell (2012), collapsed to only show the superfamily Mycteropoidea.

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were congeneric (e.g. synonymous) was first suggested by British geologist Charles D. Waterston in 1985.

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known from reasonably complete remains other than the type species itself. The fossil, discovered in the

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Discerning the Diets of Sweep-Feeding Eurypterids Through Analyses of Mesh-Modified Appendage Armature

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was its comb-like first appendages. Waterston remarked in another 1968 paper that the "controversial"

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in 1912, though no distinguishing features of the fossils were given due to their fragmentary nature.

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is too limited to confidently establish any distinguishing features, but it is noted to be similar to

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Though sometimes, and often historically, treated as distinct genera, the hibbertopterid eurypterids

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Waterston, Charles D. (1968). "I.—Further Observations on the Scottish Carboniferous Eurypterids*".

2764:. Several terrestrial invertebrates are also known from the location, including several species of 1930:

relationships within the Hibbertopteridae difficult. Both genera could even represent synonyms of

673:. The features of fossils associated with these genera suggest that the sweep-feeding strategy of 3519: 1794:

had originally been described as the fragmentary remains of a eurypterid in 1889 was assigned to

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as composing three separate, but closely related, hibbertopterid genera. In these arrangements,

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The only known specimen, discovered in Ireland, is probably lost and was originally assigned to

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was a large, broad-bodied and heavy animal. It was the largest known eurypterid of the suborder

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Braddy, Simon J.; Lerner, Allan J.; Lucas, Spencer G. (2023). "A new species of the eurypterid

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Kjellesvig-Waering, Erik N. (1959). "A Taxonomic Review of Some Late Paleozoic Eurypterida".

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are located) and by the many crenulations present on the distal margins of its leg segments.

4808: 4702: 3973: 3806: 3128: 1253: 1213: 1175: 1141: 1103: 1069: 1007: 973: 939: 901: 1162:. Its latest published diagnosis is simply the same as the diagnosis of the genus itself. 8: 3082:"The systematics and phylogeny of the Stylonurina (Arthropoda: Chelicerata: Eurypterida)" 2839: 2737: 1851: 1377: 1338: 796: 630: 567: 3810: 3424:

Kjellesvig-Waering, Erik N. (1961). "The Silurian Eurypterida of the Welsh Borderland".

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Tetlie, O E (2007). "Distribution and dispersal history of Eurypterida (Chelicerata)".

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on the basis of the perceived filaments present on its appendages, similar to those of

1453:" was noted to represent the fossil remains of a eurypterid by American paleontologist 647: 467: 174: 3204:"A Middle Devonian chasmataspid arthropod from Achanarras Quarry, Caithness, Scotland" 1380:

in 1863. This designation was reinforced with more fossil fragments discovered in the

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would probably have been incapable of preying on larger animals. The conclusion that

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were weak and they would not have been able to grasp any potential prey which means

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is likely to have been the heaviest due to its broad and compact body. Furthermore,

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fed through a method called sweep-feeding. It used its specialised forward-facing

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were probably the precursors of the more moveable finger-like organs present in

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is the presence of ~110 filaments in every row of its comb-like feeding organs.

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