It is only known from the type locality in the upper Kikori Basin in the Southern Highlands Province, Papua New Guinea.

[2] The specific name refers to its most distinctive feature, the moderately enlarged discs on fingers and toes, although their function remains unknown as the specimens were collected on or near the ground.

[1] The advertisement call of male Callulops mediodiscus is a series of four loud, barking notes, with a dominant frequency of 1529–1661 Hz.

[1] The type locality is extremely wet, mossy lower-montane rainforest at about 1,750 m (5,740 ft) asl on karst limestone.

Individuals were found on the ground on leaf litter, or calling on mossy rocks and logs after rain at night.