Convergent evolution of giant size in eurypterids.

Area of Science:

• Paleontology
• Evolutionary Biology
• Arthropod Paleobiology

Background:

• Eurypterids, or sea scorpions, were Palaeozoic arthropods that achieved remarkable sizes.
• These marine and freshwater creatures repeatedly evolved gigantism and colonized diverse aquatic habitats.

Purpose of the Study:

• To investigate the evolutionary drivers behind the giant size of eurypterids.
• To test hypotheses linking eurypterid gigantism to habitat, temperature, oxygen, latitude, and diversity.

Main Methods:

• Compiled data on a majority of eurypterid species.
• Employed a phylogenetic comparative approach utilizing a new tip-dated phylogenetic tree.
• Analyzed correlations between body size evolution and environmental/ecological factors.

Main Results:

• No compelling evidence supports temperature or oxygen levels driving eurypterid gigantism.
• Giant size evolution was not coupled with continental aquatic invasions, latitude, or local faunal diversity.
• Eurypterid body size evolution is characterized by rapid, independent bursts of change.

Conclusions:

• Intrinsic factors played a significant role in the convergent evolution of eurypterid gigantism.
• Habitat and environmental conditions were not primary drivers of sea scorpion size evolution.