How did subholosteans differ from more primitive palaeonisciform fishes?

Subholosteans, which emerged from palaeonisciform-like ancestors during the Permian and Triassic periods, represented an evolutionary transition toward more advanced actinopterygian fishes. They differed from the more primitive Palaeonisciformes in several key ways:1

• Jaw Structure: A defining characteristic of subholosteans was the development of an upright jaw suspension, a feature that anticipated the more advanced anatomy found in holosteans. In contrast, primitive palaeonisciforms typically possessed jaws firmly bound to the cheekbones, which limited their biting power.12
• Skeletal Diversity: Subholosteans exhibited a greater diversity in skeletal structure than the more primitive palaeonisciforms. This variation is viewed by scientists as a series of evolutionary experiments that occurred during the rise of more advanced fish families.1
• Evolutionary Significance: While palaeonisciforms served as the basal stock for all other chondrosteans and holosteans, subholosteans acted as an intermediate group, bridging the gap between primitive forms and the later, more efficient holosteans and teleosts.12