The thick-billed longspur, also known as McCown's longspur, is a small ground-feeding bird in the family Calcariidae, which also contains the other longspurs and snow buntings. It is found in North America and is the only species in the genus Rhynchophanes.

Calcariidae is a small family of passerine birds. It includes longspurs and snow buntings. There are six species in three genera worldwide, found mainly in North America and Eurasia. They are migratory and can live in a variety of habitats including grasslands, prairies, tundra, mountains, and beaches.