Optional disagreement and the case for feature hierarchies

Jingulu (western Barkly Tablelands, Northern Territory, Australia (non-Pama-Nyungan)), the traditional language of the Jingili people, shows evidence for a hierarchical relationship between all four of its gender categories. Modifiers have separate forms for each of the four genders and usually appear in the same gender form as the head they modify. When disagreement occurs, masculine modifiers can found with heads of all four genders, while vegetable gender heads can be modified by neuter modifiers as well. While agreement is the norm, disagreement is always an available option, and appears never to be either mandated or ruled out in specific grammatical or semantic contexts.