I have usually seen the paucal number presented as intermediate between singular and plural in the languages that have it:
However, is there any language that only distinguishes between paucal and plural? Or is it a linguistic universal that a language with only two number distinctions will always have singular and plural, and that the paucal number only occurs in languages with three or more number distinctions?
I don't know much on the issue personally, but in Person and number in pronouns: a feature-geometric analysis (Harley & Ritter, 2002), they make the following claims:
...a language never has a dual without also having a plural (captured by the fact that both Group and Minimal must be active to encode dual). Similarly, no language has a paucal without also having a dual.
This seems straightforward enough, and under this claim, languages with a paucal must have at least 4 numbers (singular, dual, paucal, plural). However, they make some concessions in the footnotes:
Corbett (2000:39) makes a distinction between determinate and indeterminate numbers. Singular, dual and trial denoting exactly one, two or three individuals, respectively, are determinate numbers; paucal and plural are indeterminate ones. We have not explicitly encoded this distinction in the geometry, with the advantage that it enables us to deal straightforwardly with languages that allegedly have a paucal without a dual, such as Bayso (Cushitic) or Walapai (Yuman), cf. Corbett (2000:22) and references cited therein. In these languages, the paucal denotes between two and six individuals, rather than the usual case of three to six. We propose that a dual is a simply a determinate minimal group, and that the paucal in Bayso or Walapai is an indeterminate one, represented by the same Minimal Group geometry as the dual.
So it seems that the previous paucal-dual claim has counterexamples. Still, there must be a singular-plural distinction before a paucal can appear, and it is quite likely there will be a dual as well.
They make another interesting restriction on number related to the paucal:
Note that we predict that no language has both a trial and a paucal number; they are in complementary distribution, representing determinate and indeterminate interpretations of the same geometric configuration.
And of course, no typological study is comprehensive. I'd be happy to hear more on the issue myself. ;)
An auxiliary issue is the point that number is a property of morphologial subsystems, rather than of languages themselves. Most languages only distinguish number on nouns and noun-indexing inflectional morphemes, and do so in a consistent way. Some languages, especially Oceanic languages, have different number-marking systems for different morphological subsystems.
In Wala, lexical nouns have only a two-way distinction between singular and non-singular (i.e. two or more), but possessive suffixes show a four-way distinction between singular, dual, paucal and plural. (data is from a sketch I am preparing)
In Hiw it gets even more interesting. Subject pronouns can be singular, dual, or plural. Object suffixes can be only singular or non-singular, and non-human NP's show no number contrast at all. Hiw also has verbal number, and the contrast is between plural and non-plural (i.e. one or two). So the verb meaning 'kill' has two suppletive stems, not, meaning to kill one or two people, and qetnog, to kill three or more people. This is a rare case of a subsystem where there is no singular number. (Hiw data is from Francois 2009)
