Do Athapaskan languages provide a precedent for signed language 'classifier predicates'?

In the 1970s, linguists still thought of signed classifier predicates (CPs) as visual representation. One of the key events that changed this perspective was the apparent discovery of a good 'formal' parallel to CPs in the verb morphology of some spoken languages. However, as Engberg-Pedersen (1993) has argued, these parallels are in fact mistaken. The mistake appears to have arisen as follows.Athapaskan languages, such as Navaho or the Apachean group, have a very complex verbal morphology. It includes a group of verb morphemes which Allan (1977) called "predicate classifiers", because these morphemes appear to classify the action of the verb according to such now-familiar, CP-like criteria as the physical features of the object involved (round, flat, long, etc). The exciting thing for signlanguage linguists, though, was not the semantic parallels, but the formal parallels that seemed to exist with Athapaskan verbs.