Nameless was probably sniffing you intently--the open-mouth thing is called the flehmen response, and it's what cats do when they find something that they want to sniff intently. It funnels the scent-laden air past this sensory organ they have (horses have it too) to get more info.

There was a fantasy/sf novel that touched on it and the atrophy of this organ in humans--a woman of one of the Pueblo tribes, in the process of delivering an airplane to a client on some planet finds a settlement of other Pueblo people that nobody knew about, the tribe having formed a symbiotic relationship with giant sentient dragonflies. Fairly typical that I'd remember that detail but not the useful ones like author or title. ;-)