This timeline of eurypterid research is a chronologically ordered list of important fossil discoveries, controversies of interpretation, and taxonomic revisions of eurypterids, a group of extinct aquatic arthropods closely related to modern arachnids and horseshoe crabs that lived during the PaleozoicEra.
The scientific study of eurypterids began in the early 19th century when James E. DeKay recognized a fossil that had previously been described as that of a fish as arthropod in nature. Though DeKay erroneously believed the fossil to represent a crustacean and a missing link between trilobites and branchiopods, the fossil became the type species of first ever eurypterid to be scientifically described, Eurypterus remipes, in 1825.[1]
Over 250 species of eurypterids in 74 recognized valid genera have been described since the discovery of Eurypterus remipes.[2] The most recent genus to be described is Terropterus (2021) and the most recent species is its type species Terropterus xiushanensis (2021).[3]
19th century
Reconstruction of Eurypterus. Eurypterus was the first eurypterid to be described.
The first eurypterid fossil to be discovered is unearthed in rocks in New York of Silurian age. It is described by Dr. S. L. Mitchill as an example of the fish Silurus, possibly due to the catfish-like appearance of its carapace.[1]
Agassiz recognized Pterygotus as an arthropod after the discovery of more complete remains, he classified it as a crustacean of the Entomostraca subclass.[9]
Salter described the new genus Himantopterus (the genus name was replaced in 1859 by Erettopterus) and the new species H. acuminatus, H. banksii, H. bilobus, H. lanceolatus, H. maximus and H. perornatus.[14]
Salter described the species Pterygotus acuminata.[15]
Page transferred Pterygotus acuminata to its own genus, Slimonia.[15]
Page named and figured, but did not thoroughly describe, the genus Stylonurus.[16]
Edouard D'Eichwald recognized Kutorga's Limulus oculatus to be highly distinct from Limulus and created the generic name Campylocephalus to contain the species.[23]
Henry Woodward described the genus Stylonurus (named and figured, but not thoroughly described, by David Page in 1856) and raised the rank of the Eurypteridae to that of order, effectively creating the Eurypterida as the taxonomic unit it is seen as today.[16]
Woodward created the subclass Merostomata to contain eurypterids and xiphosurans.[17]
Ernst Haeckel classified the Merostomata (containing virtually only the Eurypterida) and Xiphosura within a group he named Gigantostraca within the crustaceans. "Gigantostraca" is later treated as a synonym of Mersostomata.[17]
Samuel Almond Miller described the new genus and species Megalograptus welchi, mistakenly believing the fragmentary fossils to represent a graptolite.[30]
Ben Peach named the genus Glyptoscorpius to include some fossils from the Carboniferous of Scotland, including the species G. perornatus, G. caledonicus and G. kidstoni. He mistakenly believed the fossils to represent the remains of scorpions.[38]
Dewalque described the species Eurypterus lohesti.[44]
1890s
Fossil of Carcinosoma newlini. Carcinosoma was coined as a replacement name for the preoccupied name Eurysoma in 1890, the same year its type species was described.
Edward Waller Claypole described the genus and species Eurysoma newlini. Later that same year he discovered Eurysoma to be pre-occupied, and coined the replacement name Carcinosoma.[45]
Pereira de Lima described the species Eurypterus douvillei, later referred to Adelophthalmus.[2]
In the work Anatomy and Relations of the Eurypterida (1893), Malcolm Laurie added considerably to the knowledge and discussion of eurypterid anatomy and relations. He focused on how the eurypterids related to each other and to trilobites, crustaceans, scorpions, other arachnids and horseshoe crabs.[17]
Gerhard Holm described the species Eurypterus fischeri. His description was so elaborate that the species became one of the most completely known of all extinct animals, so much so that the knowledge of E. fischeri was comparable with the knowledge of its modern relatives (such as the Atlantic horseshoe crab). The description also helped solidify the close relationship between the eurypterids and other chelicerates by showcasing numerous homologies between the two groups.[17]
Samuel Almond Miller and William Frank Eugene Gurley described the species Eurypterus kokomoensis, later considered the type species of the genus Onychopterella.[32]
Clifton J. Sarle described the new species Pterygotus monroensis and Eurypterus pittsfordensis. The new genus and species Hughmilleria socialis with the variety H. socialis var. robusta is also described.[52]
Ruedemann recognizes that Megalograptus is an eurypterid, rather than a graptolite.[30]
1910s
Reconstruction of Jaekelopterus rhenaniae. Initially described as a species of Pterygotus in 1914, Jaekelopterus rhenaniae is the largest known eurypterid.
Ruedemann and Clarke publish The Eurypterida of New York, wherein several new speciesand taxonomic groupings are created. New species described are Eurypterus megalops, Eurypterus pristinus, Eurypterus ranilarva, Eurypterus stellatus, Eusarcus longiceps, Eusarcus triangulatus, Eusarcus vaningeni, Dolichopterus frankfortensis, Dolichopterus latifrons, Dolichopterus siluriceps, Dolichopterus testudineus, Dolichopterus stylonuroides, Stylonurus limbatus, Ctenopterus multispinosus, Drepanopterus longicaudatus, Hughmilleria magna, Pterygotus atlanticus, Erettopterus globiceps, Pterygotus nasatus and Pterygotus prolificus. They also name the genus Tylopterus (later Tylopterella) and the family Pterygotidae. There are also numerous taxonomic revisions. Eurypterus obesus and E. acrocephalus are referred to the genus Eusarcus.[17] The genus Carcinosoma, to which the species Eurypterus scorpioides and Eurypterus scoticus are transferred, is designated as a junior synonym of Eusarcus.[32] The species Eurypterus kokomoensis is raised to the subgeneric level under the subgenus name Onychopterus.[17]
Otto Jaekel described the new species Pterygotus rhenaniae, later designated as the type species of Jaekelopterus.[55]
Erwin H. Barbour described the new species Anthraconectes nebraskensis. The discovery helped reinforce the idea as Adelophthalmus (or Anthraconectes) as a freshwater animal.[56]
Gilbert Oscar Raasch referred Strabops to the order Aglaspida.[67]
Roy Woodhouse Pocock and A. J. Butler discover a relatively complete telson of Eurypterus abbreviatus, showing that the species was highly distinct from other species referred to the genus.[68]
Pruvost described the species Anthraconectes corneti.[2]
1940s
Carapace of Unionopterus anastasiae. Unionopterus was first described in 1948 and its precise taxonomical position remains unclear.
Reconstruction of Campylocephalus. Throughout the 1950s, several studies centered on whether or not Campylocephalus was synonymous with Hibbertopterus.
Kjellesvig-Waering described the new family Hughmilleriidae, composed of Hughmilleria, Slimonia, Grossopterus, Lepidoderma, Hastimima and the new genus Salteropterus abbreviatus (formerly a species of Eurypterus), leaving the Pterygotidae monotypic.[68]
Størmer concluded that Campylocephalus and Hibbertopterus were congeneric. The fossils that had been referred to Ediothea were recognized as representatives of Campylocephalus.[72]
Størmer noted that the name Onychopterus was pre-occupied and coined the replacement name Onychopterella.[72]
Kjellesvig-Waering coined the replacement name Tylopterella for the genus Tylopterus, as the name Tylopterus was found to be preoccupied.[73]
Augusta and Pribyl described the species Ctenopterus ostraviensis.[49]
Kjellesvig-Waering reaffirmed the status of Tylopterella as a separate genus from Eurypterus.[78]
Kjellesvig-Waering publishes a study which determines the coloration of Carcinosoma newlini; showing that it was light brown with darker scales and appendages and a black telson and spines.[45]
Kjellesvig-Waering recognized Campylocephalus as being distinct from Eurypterus scouleri and erected the genus Hibbertopterus to contain E. scouleri.[2]
Adelophthalmus oklahomensis is designated a junior synonym of Adelophthalmus sellardsi.[44]
1960s
Reconstruction of Nanahughmilleria norvegica. Nanahughmilleria was one of the many products of major taxonomic revisals by eurypterid researchers in the 1960s.
Kjellesvig-Waering described the new species Salteropterus longilabium, Pterygotus (Pterygotus) denticulatus, P. (P.) grandidentatus, P. (P.) lightbodyi, Carcinosoma harleyi and Dolichopterus bulbosus. The new genus Parahughmilleria is described with P. salteri as the type species. Hughmilleria bellistriata, H. phelpsae and Eurypterus maria are moved to this genus. The subgenus Erettopterus is regarded as a new genus and is separated into two new subgenera, E. (Erettopterus), including the new species E. (E.) brodiei, E. (E.) marstoni and E. (E.) spatulatus, and E. (Truncatiramus), including the new subspecies E. (T.) gigas megalodon. The genus Hughmilleria is split into two new subgenera, H. (Hughmilleria) and H. (Nanahughmilleria).[12]
Kjellesvig-Waering transfers the species Pterygotus punctatus to Carcinosoma as Pterygotus punctatum.[21]
Nestor Ivanovich Novozhilov names the genus Rhinocarcinosoma to contain the species R. vaningeni and R. cicerops, previously referred to Eusarcus (Paracacinosoma).[79]
Charles D. Waterston names the genus Jaekelopterus to contain the species Pterygotus rhenaniae.[80]
Kjellesvig-Waering described the species Pterygotus impacatus and Pterygotus lanarkensis.[81]
Kjellesvig-Waering described the species Pterygotus marylandicus.[51]
Kjellesvig-Waering questionably assigned Selaginites formosus to Pterygotus as Pterygotus formosus.[82]
Caster and Khellesvig-Waering recognize Eusarcus and Carcinosoma to represent distinct genera and since Eusarcus is pre-occupied, they coin the replacement name Paracarcinosoma for its species.[32]
Caster and Kjellesvig-Waering described the species Eocarcinosoma batrachophthalmus.[30]
Caster and Kjellesvig-Waering describe two new species of Megalograptus, M. williamsae and M. shideleri. They also assign the species M. alveolatus, named as a species of Ctenpterus, to Megalograptus.[30]
Kjellesvig-Waering and Willard P. Leutze described the new species Bassipterus virginicus (a new genus), Drepanopterus nodosus and Erettopterus (Truncatiramus) exophthalmus. The species H. (N.) phelpsae is classified as a new genus, Pittsfordipterus. Rhenopterus matarakensis is assigned to Parahughmilleria, R. schiraensis is assigned to Hughmilleria (Nanahughmilleria).[71]
Nestor Ivanovich Novojilov classifies Slimonia into a new family of its own, the Slimonidae.[83]
Waterston re-examines Eurypterus minutisculptus and concludes that it represents a genus of its own, which he names Vernonopterus.[40]
Størmer and Waterston re-examine the fossil species referred to Glyptoscorpius and name the new genus Cyrtoctenus, containing the species C. caledonicus, C. dewalquei (previously Eurypterus), C. ostraviensis (previously Ctenopterus) and C. peachi. They also name the genus Dunsopterus to contain the species G. stevensoni.[49]
Størmer creates the family Jaekelopteridae to contain Jaekelopterus. This family has subsequently been treated as synonymous with the Pterygotidae.[77]
Størmer raises the Pterygotus subgenus Acutiramus and the Erettopterus subgenus Truncatiramus to the level of separate genera.[59]
Paul Selden recognizes the fossil remains of Necrogammarus, previously believed to possibly represent a crustacean or a millipede, to be fragmentary fossils of a pterygotid eurypterid.[22]
Salteropterus is placed in the family Slimonidae by Tollerton.[95]
Tollerton publishes a major taxonomic revision of the Eurypterida, dividing it into suborders Eurypterina and Ptergotina and recognizing some eurypterids, such as the hibbertopterids, as outside the order and part of a distinct order he calls Cyrtoctenida.[96] Modern research favors suborders Eurypterina and Stylonurina instead.[97]
The fossil that will later be designated as the holotype of Rhinocarcinosoma dosonensis is discovered in northern Vietnam and initially misidentified as a chasmataspidid.[79]
Ciurca reported specimens of Rhinocarcinosoma and Paracarcinosoma from elsewhere in the United States, the genera previously mainly being known from fossils found in New York State.[98]
Braddy, Richard John Aldridge and Johannes N. Theron described the species Onychopterella augusti.[99]
21st century
2000s
Reconstruction of Herefordopterus banksii. Regarded as a species of Hughmilleria since 1859, H. banksii was concluded to represent a genus of its own in 2006.
Tetlie interpreted Hughmilleria banksii as a new genus, Herefordopterus. In addition, the species Hughmilleria acuminata was synonymized with Herefordopterus banksii.
Evgenyi S. Shpinev described the species Adelophthalmus irinae.[102]
Tetlie, Selden & Ren described the new species Hughmilleria wangi.[103]
Miller and Tetlie determine that Bunodella represents an indeterminate species of Acutiramus. However, it is not formally synonymized and is regarded as a nomen dubium.[104]
Poschmann and Tetlie determine that Jaekelopterus was a highly derived pterygotid, not a basal form as previously assumed. It is declared to represent the largest known eurypterid.[105]
Tetlie described the new species Pterygotus sarlei.[106]
Ciurca and Tetlie transfer the species Pterygotus waylandsmithi to Erettopterus. Additionally, they concluded that P. monroensis was synonymous with E. osiliensis.[59]
Tetlie suggests that Dorfopterus might represent a telson of Strobilopterus princetonii and tentatively synonymizes Dorfopterus into the species.[107]
Shpinev described the new species Parahughmilleria longa and Nanahughmilleria notosibirica.[109]
Shpinev described the new species Adelophthalmus kamyshtensis and Adelophthalmus dubius.[110]
Lamsdell publishes a phylogenetic analysis which finds Merostomata to be invalid, as Xiphosura is paraphyletic, and finds eurypterids to be more closely related to arachnids than to horseshoe crabs.[97]
Jason A. Dunlop and Lamsdell pointed out that Eusarcana holds priority over Paracarcinosoma as a replacement name for Eusarcus, designating Paracarcinosoma as a junior synonym of Eusarcana.[32]
Lamsdell reassigned Hibbertopterus permianus to Campylocephalus as Campylocephalus permianus.[92]
McCoy, Lamsdell, Poschmann, Anderson and Briggs conduct a study on the eyes of pterygotid eurypterids and determine that the genera included in the family, such as Jaekelopterus, Acutiramus and Ptergyotus, had divergent adaptations, suggesting they had different ecological roles despite their close outward resemblance.[115]
Emily Hughes concludes that the genera Cyrtoctenus and Dunsopterus represent junior synonyms of Hibbertopterus.[119]
Schoenemann, Poschmann and Clarkson publish a study comparing the eyes of Jaekelopterus with those of horseshoe crabs, arachnids and other arthropods.[120]
Naugolnykh and Areshin describe the new species Soligorskopterus shpinevi.[121]
Brandt publishes a study on the possible relationships between eurypterid morphology, the ease with which members of this group experienced ecdysis and the longevity of eurypterid species.[125]
Wang et al. describe Terropterus xiushanensis, to date the most recently described eurypterid genus and species.[3]
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