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Eurypterus sp.
Eurypterus #1
Eurypterus is an extinct genus of the order Eurypterida which is a group known as "sea scorpions". Eurypterids(sea scorpions) flourished during the Silurian and the Devonian 3).
The eurypterids are known as large arthropods groups and actually almost groups have representatives approaching 1m. Some of Eurypterus also are about 1m in length, but many species of Eurypterus are several tens cm 2), 3).
Eurypterus #5
Eurypterus has six paired prosomal (head and thorax) appendages. The first pair of limbs is chelicerae, limbs II - IV are feeding and/or walking, limbs V is walking, and limbs VI is paddle-like form adapting for swimming 1), 3). The chelicera of Eurypterus is small.
Eurypterus #2
The euypterids were sexual dimorphism. There is a model of mating that the male deposits a spermatophore on the bottom and the female retrieves and storages it in the spemathecae, allowing the timing of egg production and fertilization to be controlled 1). In the ancient lagoon, a pair of eurypterids may have danced face to face with each other.
Eurypterus #6
The eurypterids may have mated and moulted en masse. They may have migrated seasonally into quiet and fluctuating salinity levels environments, such as nearshore, lagoons, brackish water estuaries, to protect themselves from other predators during ecdysis, or to prevent spermatophore from disruption by strong stream 1).
Eurypterus #3
Probably, the eurypterids had a dual respratory system, an aquatic respiratory organ and an accessory arerial respiratory organ 4). Accordingly, they may have been able to breathe some while on land.
Eurypterus #4
Most of the eurypterids group may have been present by the Middle Ordovician. They either radiated rapidly after their occurrence, or earlier groups of them may have an origin in the Cambrian 3).
I wonder whether Eurypterus had a venomous sting. This felting work has a conspicous red spine. How was it actually ?
Long genital appendage is belong to the female, short one is belong to the male 1). This felted Eurypterus may be female.
created in November 2017 - April 2018.
  1. Braddy SJ, Dunlop JA (1997) The functional morphology of mating in the Silurian eurypterid, Baltoeyrypterus tetragonophthalmus (Fischer, 1839). Zool. J. Linn. Soc. 120(4):435-461.(DOI:10.1111/j.1096-3642.1997.tb01282.x)
  2. Braddy SJ, Poschmann M, Tetlie OE (2007) Giant claw reveals the largest ever arthropod. Biol. Lett. 4:106-109. (DOI:10.1098/rsbl.2007.0491).
  3. Lamsdell JC, Briggs DEG, Liu HP, Witzke BJ, McKay RM (2015) The oldest described eurypterid: a giant Middle Ordovician (Darriwilian) megalograptid from the Winneshiek Lagerstätte of Iowa. BMC Evol Biol 15(169). (DOI:10.1186/s12862-015-0443-9).
  4. Manning PL, Dunlop JA (1995) The respiratory organs of eurypterids Palaeontology 38 : 287-297.