How are osteoglossomorph fishes classified within the bony fishes?

Osteoglossomorphs (superorder Osteoglossomorpha) are classified as a group of bony fishes widely considered to be the most primitive lineage within the group. Their classification is primarily based on skeletal characteristics, including the structure of the caudal fin, the bones surrounding the eye, and the anatomy of the gill arches and inner ear.12

Within this superorder, they are divided into two distinct orders:

• Osteoglossiformes: A diverse group characterized by well-developed teeth on the tongue and mouth cavity. This order includes suborders such as the Osteoglossoidei (e.g., bonytongues), Notopteroidei (e.g., knifefishes), and Mormyroidei (e.g., mormyrs).2
• Hiodontiformes: Represented by the family Hiodontidae (goldeyes and mooneyes), which are found in North America and are regarded as the most primitive living osteoglossomorphs.12

While generally viewed as basal, the exact evolutionary position of osteoglossomorphs among teleostean lineages remains a subject of scientific debate, with some researchers challenging their status as the most primitive group.3