compare the evolution of bony fish and jawless fish.
During the Cambrian explosion approximately 530 million years ago, fish began to evolve. The early chordates developed the skull and vertebral column during this epoch, giving rise to the first craniates and vertebrates. The first fish lineages are the Agnatha (or jawless fish). Haikouichthys was among the first. Eel-like jawless fish (Conodonts), and small mostly armoured fish (ostracoderms) first appeared during the late Cambrian period. Most jawless fishes are no longer appear, but the extant lampreys may resemble ancient pre-jawed fish. Lampreys are members of the Cyclostomata, which includes extant hagfish, and this group may have separated from other agnathans earlier.
The earliest jawed vertebrates evolved during the late Ordovician period. The armoured fish are known as placoderms, which evolved from the ostracoderms, and the Acanthodii (or spiny sharks) are the first fish to be found in the Silurian fossil record. The jawed fish that exist today also appeared during the late Silurian: the Chondrichthyes (or cartilaginous fish) and the Osteichthyes (or bony fish). The bony fish evolved into two distinct groups: Sarcopterygii (which includes the lobe-finned fish) and Actinopterygii (or ray-finned fish).
Step by step
Solved in 3 steps
