of
H. scouleri with a
telson and
appendages based on those of
Eurypterus (with swimming paddles and unspecialised walking appendages). 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 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 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 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 the two original species. Inexplicably,
Pterygotus hibernicus (a species described 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, but apparently flawed 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-Waering's acceptance of 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 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. 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 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 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, 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 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 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 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 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 the "cyrtoctenids" were definitely
Hibbertopterus-type eurypterids, not representatives of a new order of arthropods. == Classification ==