Cephalopod body size and macroecology through deep time

Area of Science:

• Paleontology
• Marine Biology
• Evolutionary Biology

Background:

• Cephalopods are ancient marine predators crucial to ecosystem regulation.
• Understanding their evolutionary body size trends provides insights into marine ecosystem dynamics.

Purpose of the Study:

• To reconstruct and analyze the long-term fluctuations of cephalopod body size from the Cambrian to the present.
• To compare the evolutionary trajectories and mass extinction responses across major cephalopod groups.

Main Methods:

• Determined maximum body volumes for various cephalopod species using diverse proxies for inter-group comparability.
• Separately analyzed Cephalopoda with orthoconic conchs, Nautilida, Ammonoida, and Neocoleoida.

Main Results:

• Long-term body size trajectories varied significantly among the examined cephalopod groups.
• All groups, except nautilids, evolved species exceeding one meter in size, becoming part of the marine megafauna.
• Nautilids and orthocones had a volume threshold around 100 liters, while ammonoids and neocoleoids reached up to 500 liters.

Conclusions:

• Cephalopod body size evolution is diverse, with distinct group-specific trends and responses to environmental changes like mass extinctions.
• The study highlights the significant ecological role of cephalopods, particularly the evolution of marine megafauna within this class.