Acutiramus fossil map
Where fossils of Acutiramus have been found, shown on the Earth as it looked about 420 million years ago and on today’s map.
Dots are fossil collections recorded in the Paleobiology Database. The “then” view moves today’s fossil sites back to their positions 420 million years ago (the time slice nearest the median age of the fossils) using the Merdith et al. (2021) plate model; positions are approximate. Open on the timeline map →
| Group | Trilobites & sea scorpions |
|---|---|
| Lived | 425–410.62 million years ago (Ludfordian to Pragian) |
| Periods | Silurian, Devonian |
| Family | Pterygotidae |
| Named by | (Ruedemann 1935) |
| Fossil records | 32 occurrences at 18 locations (PBDB) |
| Found in | Czech Republic, United States, Canada, Spain, Algeria, Australia |
| Rock formations | Pozary, Lochkov, Fiddlers Green, Bertie, Cunningham Creek, Olorda |
About Acutiramus
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) and likely an apex predator.
Text in “About” is quoted from the Wikipedia article Acutiramus (revision 1374508465), licensed under CC BY-SA 4.0; introduction excerpted verbatim, formatting removed. Ages, family, authority and fossil records: Paleobiology Database, accessed 23 October 2026. Ages are those of the rock layers the fossils were found in. Wikidata: Q3651722.
