How are atheriniform fishes related to spiny-finned fishes?

Atheriniform fishes are classified as members of the superorder Acanthopterygii, commonly known as spiny-finned fishes. They represent a radiation from near the base of the acanthopterygian stock, though their precise evolutionary relationships within this group remain uncertain.123

While atheriniforms share several structural resemblances with more advanced spiny-finned fishes, these features are distributed in a mosaic pattern, indicating that they were likely acquired independently rather than inherited from a common ancestor. For example, although many atheriniforms possess protrusile jaws and spines in front of their dorsal and anal fins, the structural mechanisms behind these traits differ significantly from those found in typical acanthopterygians. Unlike higher spiny-finned fishes, atheriniforms lack the complex system of joints and ligaments for jaw protrusion and do not possess a direct bony contact between their pelvic and shoulder girdles. Consequently, while they are grouped with spiny-finned fishes, many of their "spiny" characteristics appear to have evolved independently.4