Why are protacanthopterygians important to the evolution of bony fishes?

Protacanthopterygians are significant to the evolution of bony fishes because they serve as a basal stock within the mainstream of modern teleost evolution. During the Late Mesozoic Era, approximately 100 million years ago, the ancestors of these fishes developed several evolutionary trends that provided the essential "raw material" for the emergence of multiple successful lineages.1

These lineages ultimately gave rise to the majority of modern bony fishes. Furthermore, scientific analysis suggests that several more advanced groups of fishes—including the Scopelomorpha, Paracanthopterygii, and Acanthopterygii—likely share a common ancestry, having evolved from early, protacanthopterygian-like ancestors. While these fishes are considered more advanced than "lower" teleosts like osteoglossomorphs and ostariophysans, they represent a critical transitional stage in the broader history of actinopterygian development.12