Evolutionary prerequisites for early Phanerozoic calcareous skeletons

Area of Science:

• Evolutionary Biology
• Biomineralization
• Cell Physiology

Background:

• The Lower Cambrian period witnessed a rapid diversification of metazoans, including the sudden appearance of organisms with calcareous skeletons.
• Understanding the precise triggers for this biomineralization event is crucial for comprehending early animal evolution.

Observation:

• A homologous family of calcium-modulated proteins, characterized by "EF hands", has been identified.
• These proteins play a key role in maintaining low intracellular calcium concentrations and regulating calcium ion flow.
• The fossil record indicates the timing of the first appearance of calcareous mineralization across different phyla.

Findings:

• The origin of sophisticated intracellular calcium modulation mechanisms is directly linked to the emergence of calcareous skeletons.
• Specialized calcium physiology, particularly in muscle systems, served as a preadaptation for calcification.
• Predation acted as a selective pressure, driving the diversification of calcified metazoans during the Tommotian period.

Implications:

• The evolution of cellular calcium regulation was a prerequisite for the development of macroscopic calcified hard parts.
• This study provides insights into the interplay between physiological innovation and ecological pressures in driving evolutionary radiations.
• The findings contribute to our understanding of the early evolution of skeletal structures and metazoan body plans.