I don't believe that Mr. Clubtail was part of the group of grownups that traveled to the Great Valley in the first movie. I believe that he arrived on his own sometime between movies 2 and 3.
Reasons for believing such:
1) He does not appear in movies one or two. His first appearance is in Movie 3, and he's played relatively notable parts in every movie he's appeared in from then on.
2) In the flashback from LBT 7, he is not shown traveling with the other grownups (the ankylosaurus you see with them chooses to follow Pterano, and meets his end from ambushing velociraptors.)
3) When Ruby discusses star days in the similarly named TV episode, none of the Great Valley inhabitants seem to know what a star day is (they probably use the term "hatch day," spoken by Cera in LBT 5.) However, when star days are mentioned to Mr. Clubtail, he is familiar with the term.
Opinions? Rebuttals? Guffaws?