What research has been done on attachment types in other primates? The most canonical experimental paradigm for studying human attachment styles is the Strange Situation leading to classifications such as Secure, Insecure-avoidant, and so on.

What are the equivalent methodologies, classifications, findings and longtitudinal variability in studies of other primates?

I should add that I'm vaguely aware of, say, Harlow's work, but as far as I understand it, it seems to be about the existence of, rather than the variability of, attachment behaviour in animals.
Jaak Panksepp, in Affective Neuroscience: The Foundations of Human and Animal Emotions, describes seven brain systems, "raw feels", that are shared among human and non-human primates. One of these systems is PANIC (he capitalizes the systems' name to differentiate them from the similar terms used in speaking about emotions). He says, "a separation distress PANIC system is important in the elaboration of social-emotional processes related to attachment".