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Humeral variation associated with digging ability in the subterranean rodent Ctenomys was analyzed through 6 functionally significant indexes. The humerus of some extinct and living species was slightly more specialized than that of fossorial octodontoids [dagger] Actenomys and Octodon, whereas it was highly specialized in some living species. The constant occurrence of greater epicondyles suggests a hierarchical pattern in the acquisition of scratch-digging specializations. A possible relationship between humeral morphological diversity and environments is preliminarily discussed. Key words: Ctenomyidae, morphofunctional humeral diversity, rodents, scratch-digging adaptations

We respond to Steppan and Sullivan's (2000) critique of the systematic arguments and recommendations presented by Mares and Braun (1996). We argue that a 'nonstatistical' approach still has a place in systematics as it is currently practiced. Although useful for hypothesis testing, Steppan and Sullivan's (2000) statistical approach should be used with caution when proposing changes in classification.