The rules for the Skink Starpriest's serpent staff read as follows (emphasis mine): The Ripperdactyls are described as having a Vicious Beak, with which they perform their dreaded attack where each hit generates an extra attack. However, this attack does not include the word "bite" (unlike the Cold Ones' Vicious Bite), nor does it include the word "jaws" (unlike a Saurus's Powerful Jaws and Stardrake Shield). Given the reliance of Age of Sigmar rules on keywords, should I infer that the bonus from the Starpriest's serpent staff does not apply to Ripperdactyls? Thanks.
No bite and no jaws unfortunately, so no if you take rules as written. Same goes for a Terradon's attack. From a fluff perspective you can also explain it: it "transforms" the teeth into fangs like those from a venomous serpent. Those flying Dinosaurs are more like birds with beaks, so no teeth. Roughly speaking.
If you look at a ripperdactyl's mouth, you will notice it is some sort of combination of a beak and teeth. Also, if anything has a mouth, it has jaws, so a ripper's beak attack would count.