Giant claw reveals the largest ever arthropod

Area of Science:

• Paleontology
• Evolutionary Biology
• Marine Biology

Background:

• The fossil record shows extinct arthropods were significantly larger than modern species.
• Eurypterids, or 'sea scorpions,' are known to have reached considerable sizes in prehistoric oceans.
• Previous size estimates for Jaekelopterus rhenaniae were considerably smaller than recent findings suggest.

Purpose of the Study:

• To determine the actual size of the eurypterid Jaekelopterus rhenaniae based on new fossil evidence.
• To investigate the evolutionary relationships within the pterygotid clade.
• To explore potential factors contributing to gigantism in ancient marine arthropods.

Main Methods:

• Analysis of a 46 cm long fossil chelicera (claw) from Jaekelopterus rhenaniae.
• Estimation of total body length based on the size of the recovered fossil appendage.
• Phylogenetic analysis of the pterygotid clade, including Jaekelopterus and Acutiramus.

Main Results:

• The recovered chelicera indicates Jaekelopterus rhenaniae reached an estimated body length of approximately 2.5 meters.
• This makes Jaekelopterus rhenaniae the largest arthropod known to have ever evolved.
• Phylogenetic analysis places Jaekelopterus as a derived member of the pterygotids, closely related to Acutiramus.

Conclusions:

• The discovery of Jaekelopterus rhenaniae significantly revises our understanding of arthropod size limits.
• Gigantism in ancient marine arthropods may be influenced by factors beyond atmospheric oxygen, such as resources and predation.
• Jaekelopterus represents a key species for understanding pterygotid evolution and extreme size attainment in arthropods.