Living neopterygians are subdivided into two main groups (
infraclasses):
teleosts and
holosteans. Holosteans comprise two
clades, the
Ginglymodi and the
Halecomorphi. All of these groups have a long and extensive
fossil record. The
evolutionary relationships between the different groups of Neopterygii is summarized in the
cladogram below (
divergence time for each
clade in
mya are based on). }} Neopterygians are a very speciose group. They make up over 50% of the total
vertebrate diversity today, and their diversity grew since the
Mesozoic era. However, the diversity of the various groups of neopterygians (or of
fishes in general) is unevenly distributed, with teleosts making up the vast majority (96%) of living species. Only a few changes occurred during the evolution of neopterygians from the earlier
actinopterygians. However, a very important step in the evolution of neopterygians is the acquisition of a better control of the movements of both
dorsal and
anal fins, resulting in an improvement in their swimming capabilities. They additionally acquired several modifications in the
skull, which allowed the evolution of different
feeding mechanisms and consequently the colonization of new ecological
niches. All of these characters represented major improvements, resulting in Neopterygii becoming the dominant group of fishes (and, thus,
taxonomically of
vertebrates in general) today. == Classification ==