Yes, I thought of that. There probably is a connection, but it is not based on scientific fact. All the Gang members are of the same intelligence, even though the encephalization quotient suggests there were large gaps in intelligence among their species in reality. According to the EQ, Littlefoot should be the dumbest by far, with Spike a distant second, then a smaller gap to Cera, then a small gap a Petrie, a small gap to Ducky, a small gap to Chomper and then a large gap to Ruby, which should be the smartest by far. But since the people who creted LBT are not paleontologists, maybe the popular image of "the dumb stegosaur" made the authors choose the "slower" member of the Gang to be a stegosaur. The authors catered to public opinion here.