x1 is a rodent [can be a member of eutherian mammal Rodentia; semantic broadening might subjectively generalize the concept somewhat] of subtaxon/type/genus/species/breed/variety x2.
(Updated for 2022-11-18: This word is now in conflict with "ronti", although this word was created on or around 2014-06-27 and thus might have precedence; see "raunte"). This word is the gismu version of: "ratcnrodentia", "rontnrodentia". Meant for any rodent in general (more general than "ratcu", "smacu"). Semantic broadening may allow for any 'small, scurrying mammal' to be so named (such as lagomorphs; such description should be avoided in technical contexts and is not necessarily disparaging (unlike in English)). For the subjective generalization of concept to any 'small scurrying mammal' made explicit, unambiguous, and clear, use: "rontysmimabru".