Though this is significantly smaller than the largest eurypterid overall, Jaekelopterus, which could reach lengths of around 250 centimetres (8.2 ft), Hibbertopterus is likely to have been the heaviest due to its broad and compact body.

It used its specialised forward-facing appendages (limbs), equipped with several spines, to rake through 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 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, the hibbertopterid eurypterids Cyrtoctenus and Dunsopterus have been suggested to represent adult ontogenetic stages of Hibbertopterus.

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.

[3] Although not enough fossil material is known of the other hibbertopterid eurypterids to discuss the differences between them with full confidence,[4] 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 the middle, with in turn had a small indentation in its own centre.

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.

[6] 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.

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 the fossils were given due to their fragmentary nature.

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 ornamentation was absent in all other species of Pterygotus, but "strikingly similar" to what was present in Cyrtoctenus.

Despite noting 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.

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 the very limited fossil material.

The fossil, discovered in the Waaipoort Formation near Klaarstroom, Cape Province, South Africa, is remarkably complete, preserving not only the prosoma, the telson and several tergites, but also coxae and even part of the digestive system.

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 hibbertopterids are united as a group by being large mycteropoids with broad prosomas, 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.

The cladogram below is adapted from Lamsdell (2012),[16] 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 the ten species assigned to Hibbertopterus as composing three separate, but closely related, hibbertopterid genera.

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.

In particular, she noted that though 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.

[4] 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.

[23] 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.

[23] Additionally, some studies suggest that eurypterids possessed a dual respiratory system, which would allow short periods of time in terrestrial environments.

[24] 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.

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 of fish.