How are the goldeye and mooneye related to osteoglossomorphs?

The goldeye (Hiodon alosoides) and the mooneye (H. tergisus) are members of the order Hiodontiformes, which is one of the two primary orders within the superorder Osteoglossomorpha.

These two species, which are the only extant members of the family Hiodontidae, are considered by many authorities to be the most primitive living representatives of the entire osteoglossomorph group. Unlike the more diverse Osteoglossiformes—which are found across various tropical regions—hiodontiforms are geographically restricted to North America. While some taxonomic classifications choose to demote the hiodontiforms to a family within the order Osteoglossiformes, they remain a fundamental part of the osteoglossomorph lineage, defined by specific skeletal characteristics such as their caudal fin structure and the anatomy of their gill arches.1234