Which tetraodontiform features became more elaborate during evolution?

While the evolution of tetraodontiforms is characterized by significant reductive trends—such as the loss of skeletal elements, fewer fin spines, and smaller gill openings—several features have become more elaborate over time.

The primary systems that have undergone elaborative trends during their diversification include:

• Scale and skin development: Scales have evolved into highly modified structures, ranging from overlapping or sutured plates to sharp, projecting spines, while the skin in some species has thickened and hardened through deep layers of connective tissue.1
• Inflation apparatus: The ability to inflate the body has become a specialized feature in certain groups.1
• Dentition: While the number of teeth has generally decreased, the size of the teeth and their fusion with the jawbones have become more pronounced.1
• Toxicity: The development of poisonous flesh has become a characteristic trait in many members of the order.1

These elaborations contrast with the order's overall evolutionary pattern of skeletal and anatomical simplification.1