Temporal range: Late Silurian-Pragian, 422–407.6 Ma
PreꞒ
Ꞓ
O
S
D
C
P
T
J
K
Pg
N
Fossil of A. cummingsi
Scientific classification
Domain:
Eukaryota
Kingdom:
Animalia
Phylum:
Arthropoda
Subphylum:
Chelicerata
Order:
†Eurypterida
Superfamily:
†Pterygotioidea
Family:
†Pterygotidae
Genus:
†Acutiramus Ruedemann, 1935
Type species
†Acutiramus cummingsi
Grote & Pitt, 1875
Species
†A. bohemicus Barrande, 1872
†A. cummingsi Grote & Pitt, 1875
†A. floweri Kjellesvig-Waering & Caster, 1955
†A. macrophthalmus Hall, 1859
†A. perneri Chlupáč, 1994
†A. perryensis Leutze, 1958
†A. suwanneensis Kjellesvig-Waering, 1955
Synonyms
Synonyms of A. bohemicus
Pterygotus comes Barrande, 1872
Pterygotus mediocris Barrande, 1872
Pterygotus blahai Semper, 1898
Pterygotus fissus Seemann, 1906
Synonyms of A. cummingsi
Pterygotus acuticaudatus Pohlman, 1882
Pterygotus buffaloensis Pohlman, 1881
Pterygotus quadraticaudatus Pohlman, 1882
Synonyms of A. macrophthalmus
Pterygotus osborni Hall, 1859
Pterygotus cobbi var. juvenis Clarke & Ruedemann, 1912
Acutiramus is a genus of giant predatory eurypterid, an extinct group of aquatic arthropods. Fossils of Acutiramus have been discovered in deposits of Late Silurian to Early Devonian age. Eight species have been described, five from North America (including A. cummingsi, the type species) and two from the Czech Republic (with one of them potentially found in Australia as well). The generic name derives from Latin acuto ("acute" or "sharp") and Latin ramus ("branch"), referring to the acute angle of the final tooth of the claws relative to the rest of the claw.
Acutiramus is classified as part of the eurypterid family Pterygotidae, a family differentiated from other eurypterids by their flattened telsons (the most posterior segment of the body) and their modified chelicerae (frontal appendages), ending in well-developed chelae (claws). Many pterygotid eurypterids, such as Jaekelopterus and Pterygotus, grew to gigantic proportions. Acutiramus was no exception, with the largest species, A. bohemicus, surpassing 2 metres (6.6 feet) in length. All species were not this large though, with some (such as A. floweri) only reaching lengths of 20 centimetres (7.9 in).
Other giant pterygotid eurypterids, such as Jaekelopterus and Pterygotus, were very visually acute (possessed good and sharp eyesight) in a similar way to modern predatory arthropods and possessed robust and crushing chelae. Studies on the compound eyes and chelicerae of Acutiramus has revealed that it would have had a comparably low visual acuity and claws adapted for slicing and shearing, rather than crushing. This suggests that the ecological role of Acutiramus was distinct from that of other pterygotids, it potentially lived a lifestyle of ambush predation or scavenging on soft-bodied animals, feeding during the night or in otherwise low-light conditions.
Acutiramus is a genus of giant predatory eurypterid, an extinct group of aquatic arthropods. Fossils of Acutiramus have been discovered in deposits of...
present in Pterygotus and Acutiramus. Genital appendages can vary even within genera; for instance, the genital appendage of Acutiramus changes from species...
and Acutiramus would be recognized as separate, but closely related, genera (Erettopterus by Erik N. Kjellesvig-Waering in 1961, and Acutiramus by Størmer...
(Phosphatocopina) Other examples of now extinct arthropod groups include Acutiramus (Eurypterida) Apankura (Euthycarcinoidea) Trimerus (Artiopoda) Concavicaris...
ever lived with some members of the family, such as Jaekelopterus and Acutiramus, exceeding 2 metres (6.6 ft) in length. Their fossilized remains have...
3-segmented chelicerae Isolated fossil chelicera of a pterygotid eurypterid, Acutiramus cummingsi This is the primitive condition and occurs in arachnids such...
the Pterygotidae, is noted for several unusually large species. Both Acutiramus, whose largest member A. bohemicus measured 2.1 meters (6.9 ft), and Pterygotus...
(claws). Although some pterygotid eurypterids, such as Jaekelopterus or Acutiramus grew to gigantic proportions, it is estimated that the largest species...
Jaekelopterus rhenaniae at 2.5 metres (8 ft, the largest known arthropod) and Acutiramus bohemicus at 2.1 metres (7 ft). Ciurcopterus possessed walking legs that...
acrocephalus occur together with other eurypterids Slimonia, Pterygotus and Acutiramus as well as with various trilobites (including Crotalocephalina, Otarion...
but this is based on an incomplete telson only. A close contender was Acutiramus bohemicus at 2.1 m (6 ft 11 in) in length. The largest megalograptid as...
Kjellesvig-Waering and Caster describe the species Acutiramus floweri. Kjellesvig-Waering describes the species Acutiramus suwanneensis. Kjellesvig-Waering and Caster...
and Skrytyaspis andersoni, as well as indeterminate eurypterids like Acutiramus. The lithology (physical characteristics of the rocks) of the place has...
Member Image Notes Fish Nerepisacanthus denisoni Williamsville Eurypterids Acutiramus macrophthalmus Fiddlers Green Williamsville A. cummingsi Fiddlers Green...
Borchgrevinkium taimyrensis and indeterminate species of eurypterids like Acutiramus. The lithology (physical characteristics of the rocks) of the place near...
known occurrences of Precambrian fossils in Florida. †Actinopteria †Acutiramus †Acutiramus suwaneensis †Arisaigia †Arisaigia postornata – or unidentified comparable...
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