As it’s known, Aladar was raised by the lemurs, that’s why his way of thinking is completely different from the other dinosaurs. But their influence is not limited to his way of thinking. He shows some lemur-like behavioral traits as well during the movie. Originally the filmmakers wanted him to behave and move more like a lemur, but they rejected the idea with the exception of some brief movements.
That sassy tail swish which Aladar shows to Kron was actually intended to be one of them, it’s the same gesture, which was made by both Plio and Yar in the beginning of the movie.
Source: “Audio Commentary #1 With Directors And Special Effects Team” from the DVD