Acutiramus

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Smaller than a Microraptor!

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Acutiramus Temporal range: Late Silurian–Pragian PreЄ Є O S D C P T J K Pg N
Life-size restoration of A. macrophthalmus.
Scientific classification
Domain:	Eukarya
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Clade:	Dekatriata
Order:	Eurypterida
Superfamily:	Pterygotioidea
Family:	Pterygotidae
Genus:	†Acutiramus Ruedemann, 1935
Type species
†A. cummingsi Grote & Pitt, 1875
Reffered 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
A. bohemicus Pterygotus comes Barrande, 1872 Pterygotus mediocris Barrande, 1872 Pterygotus blahai Semper, 1898 Pterygotus fissus Seemann, 1906 A. cummingsi Pterygotus acuticaudatus Pohlman, 1882 Pterygotus buffaloensis Pohlman, 1881 Pterygotus quadraticaudatus Pohlman, 1882 A. macrophthalmus Pterygotus osborni Hall, 1859 Pterygotus cobbi var. juvenis Clarke & Ruedemann, 1912

Acutiramus is a genus of giant pterygotid eurypterid from the Late Silurian and Early Devonian eras of North America, Europe, and possibly Australia. Seven species are currently known, with 2 from Czech Republic and 5 from North America. They ranged in size from 20 centimeters.

Discovery & Naming

Misidentification as Pterygotus

Three different species of Acutiramus were originally classified as Pterygotus before 1935. In 1859, the carapace of a young Acutiramus macrophthalmus was discovered in Litchfield, New York. It was identified as a species of Pterygotus and named "Pterygotus macrophthalmus". A. bohemicus from Czech was, in 1872, also classified as a species of Pterygotus.

Paleobiology

Size

The 7 species of Acutiramus vary massively in size.
A. bohemicus was the largest, at around 7 feet (2.1 meters) in length. It was quite a slim animal, perhaps to allow graceful swimming. The only arthropod larger than A. bohemicus is another eurypterid, Jaekelopterus rhenaniae.
The smallest species (A. floweri and A. perryensis) were about 7.9 inches (20 centimeters) in length. Other giant eurypterid genera, like Jaekelopterus, also had relatively small species.

Hunting

An FEA (finite element analysis) model testing stress patterns in various species of eurypterid, it was shown that Acutiramus bohemicus featured stress concentrated in the lower part of the pincer and the serrated denticles. Based on such models, Acutiramus probably targeted softer and smaller prey than other giant eurypterids (e.g., Jaekelopterus).

Gallery

All's artistic restoration

Acutiramus cummingsi claw from Yale Peabody Museum