Agnatha, the earliest vertebrates, are considered more primi…

Agnаthа, the eаrliest vertebrates, are cоnsidered mоre primitive cоmpared to Gnathostomata, which evolved later. Agnatha species are mostly scavengers or parasites, such as lampreys, which latch onto other fish to feed. Gnathostomata, with their jaws, dominate aquatic and terrestrial ecosystems. This group includes predators like sharks, and herbivores like grazing fish. Additionally, Gnathostomata possess more advanced skeletal systems, often with bones or cartilage providing robust support. Based on this evolutionary context, which of the following features is exclusive to Gnathostomata but absent in Agnatha?