Jaekelopterus fossil map
Where fossils of Jaekelopterus 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 | 432.9–387.95 million years ago (Sheinwoodian to Eifelian) |
| Periods | Silurian, Devonian |
| Family | Pterygotidae |
| Fossil records | 7 occurrences at 7 locations (PBDB) |
| Found in | United States, Germany, Australia |
| Rock formations | Beartooth Butte, Mifflintown, txn:303383, Klerf, Hunsruck Slate, Merrimerriwa |
About Jaekelopterus
Jaekelopterus is an extinct genus of eurypterid, a group of extinct aquatic arthropods. Fossils of Jaekelopterus have been discovered in deposits of Middle Silurian to Early Devonian age, from the Wenlock epoch to Emsian stage. There are three known species: the type species J. rhenaniae from Devonian brackish to fresh water strata in the Rhineland, J. howelli from Devonian estuarine strata in Wyoming, and J. marylandicus from Silurian deposits in Maryland. The generic name combines the name of German paleontologist Otto Jaekel, who described the type species, and the Greek word πτερόν (pteron) meaning 'wing'.
Based on the isolated fossil remains of a large chelicera (claw) from the Klerf Formation of Germany, J. rhenaniae has been estimated to have reached a size of around 2.3–2.6 metres (7.5–8.5 ft), making it the largest arthropod ever discovered, surpassing other large arthropods such as fellow eurypterids Acutiramus and Pterygotus and the millipede Arthropleura. The much smaller J. howelli only reached 80 centimetres (2.6 ft) in length.
Text in “About” is quoted from the Wikipedia article Jaekelopterus (revision 1379411690), licensed under CC BY-SA 4.0; introduction excerpted verbatim, formatting removed. Ages, family, authority and fossil records: Paleobiology Database, accessed 22 October 2026. Ages are those of the rock layers the fossils were found in.
