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How has the tetraodontiform skeleton changed during evolution?

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Scrawled filefish (Aluterus scriptus) — tetraodontiform Scrawled filefish (*Aluterus scriptus*)

The evolution of the tetraodontiform skeleton is characterized primarily by a trend toward reduction. Compared to generalized perciforms, the tetraodontiform skeleton features a significantly lower number of bones. This reduction occurs through several processes, including the loss of separate bony elements, consolidation, fusion, or the failure of certain structures to develop entirely.1

This reductive trend extends to other anatomical features as well, such as the number of fin spines, the size of the mouth, and the total number of teeth. Additionally, the pelvic fin has undergone substantial reduction, often disappearing or being limited to a single spine and two small soft rays.1

While these skeletal elements have diminished, the order has simultaneously undergone elaborative changes in other systems, such as the development of specialized scales and skin, the evolution of an inflation apparatus, and the fusion of teeth with the jawbones.1