My question is actually a bit more broad than what's in the title, but I don't know how to put it succinctly. When I was trying to find the answer to that question, I found that all known terrestrial vertebrates are ultimately descended from a species of lobe-finned fish that had 2 sets of bilaterally symmetric fins (which excludes the dorsal and ventral fins), which were the basis for the limbs of its tetrapodal descendants.
The best way I can think of to phrase the question is: Does paleontology has any evidence of a vertebrate that had 3 (or more) sets of bilaterally symmetric limbs or lobe-based fins? I'd like the focus to stay away from ray-finned fish, even though they're vertebrates and related.
This is not the common question, which is whether there is or can be a mammal/reptile species with more than four limbs. The essence of that question's answer is that mammals and reptiles both evolved from a common ancestor species that were tetrapods, and that it's extremely difficult to change the genetic floor plan in the necessary way without causing fatal problems (along with other evolutionary issues). By and large, this common question is so common that it chokes out the type of question that I have, making my amateur attempts at further research difficult to impossible.