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Jaekelopterus rhenaniae
Temporal range: Middle Devonian, 390Ma
Jaekelopterus rhenaniae.jpg
Fossil of Jaekelopterus
Scientific classification e
Kingdom: Animalia
Phylum: Arthropoda
Class: Merostomata
Order: Eurypterida
Superfamily: Pterygotioidea
Family: Pterygotidae
Genus: Jaekelopterus
Waterston, 1964
Species: † J. rhenaniae
Binomial name
Jaekelopterus rhenaniae
(Jaekel, 1914)

Jaekelopterus rhenaniae ("Otto Jaekel's wing from the Rhineland") was a species of the extinct arthropod group Eurypterida. Jaekelopterus lived approximately 390 million years ago. At an estimated length of 2.5 metres (8 ft 2 in), it is one of the two largest arthropods ever discovered (the other is a giant millipede-like animal, Arthropleura, although which animal was larger is unclear).



Jaekelopterus is currently the largest known eurypterid, even bigger than the more famous Pterygotus. Again this demonstrates how the arthropods grew to giant proportions which continue to remain unknown in today’s living arthropods.[1]

The J. rhenaniae claw was found near Prüm in Germany. To work out the size of the arthropod it belonged to, Braddy and colleagues collected information on other sea scorpions and the ratio between their claw size and body length. This turned out to be relatively constant, leading the researchers to conclude that a creature with a 46-centimetre claw probaby had a body length of between 233 and 259 centimetres.[2] When extended, the chelicerae would have added 1 metre (3 ft 3 in) to its length.[3]


Although the fossil has been called a "sea scorpion", the strata in which it was found suggest that the living animal dwelled in fresh-water rivers and lakes, rather than in saltwater seas. The animal was described in November 2007 by Simon Braddy and Markus Poschmann of the University of Bristol in the journal Biology Letters: they found a 46-centimetre (18 in) chelicera (claw-like mouth part), and estimated the total size of the animal based on the proportions of this claw.[2][3][Note 1]

The animal's fossilised remains were discovered in the Lower Devonian (Emsian) Klerf Formation Lagerstätte of Willwerath near Prüm, Germany.[4][5]

See also[edit]


  1. ^ The maxim Ex pede Herculem expresses this principle of proportionality.


  1. ^ "Jaekelopterus". Prehistoric Wildlife. Retrieved 10 December 2014. 
  2. ^ a b Cressey, Daniel (November 21, 2007). "Giant sea scorpion discovered". Nature. doi:10.1038/news.2007.272. Retrieved June 10, 2013. 
  3. ^ a b Braddy, Simon J.; Poschmann, Markus; Tetlie, O. Erik (2007). "Giant claw reveals the largest ever arthropod". Biology Letters 4 (1): 106–109. doi:10.1098/rsbl.2007.0491. PMC 2412931. PMID 18029297. 
  4. ^ "Giant sea scorpion claw unearthed". BBC News. November 21, 2007. Retrieved June 9, 2013. 
  5. ^ Khamsi, Roxanne (November 21, 2007). "Giant claw points to monster sea scorpion". New Scientist.