“Paleo-monster” was Human Size

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“Paleo-monster” was human size

Largest sea scorpion fossil discovered

American scientists discovered the fossils of the oldest known species of sea scorpions buried in shale in Iowa. Some of the well-preserved pieces of molted exoskeletons of 150-odd specimens found in  sediments dated to 467 million years  ago showed that adults could attain a body length of 170 cm. The samples also included 15-20 cm-long remains of what was believed to be the young animals.

Fossils were identified to belong to sea scorpions which lived during the Mid-Ordovician period 470-to-458 million years ago   in Laurentia, then a detached continent encompassing the bulk of modern North America.

Researchers, led by James Lamsdell from the Geology and Geophysics Department of Yale University, named the so-far-unknown species of sea scorpions  – eurypterids in  scientific jargon – Pentecopterus decorahensis after the antique Greek warship “penteconter”  which it resembled in shape and aggressiveness.   

Eurypterids, are members of the class arthropoda which also includes spiders, insects and crabs.

According to the findings published in the open-access journal  BMC Evolutionary Biology , the giant sea scorpion walked the sea floor on three pairs of  limbs,  while  two forward-facing pairs and pincers were employed in catching prey.The rearmost pair of legs were flattened to form a “paddle” used for propulsion and digging the sediments on the floor.


Raşit Gürdilek


  • 1. Giant “sea scorpion” fossil discovered, BioMed Central, 31 Ağustos 2015
  • 2. Scientists find oldest known species of Sea Scorpion, ScienceOnline 31 Ağustos 2015
  • 3. “The oldest described eurypterid: a giant Middle Ordovician (Darriwilian) megalograptid from the Winneshiek Lagerstätte of Iowa”, BMC Evolutionary Biology, 1 Eylül 2015