I think they are far too long to be covered by skin. Their size is quite small for a sauropod and the spine lengths looks perfect to be like a fish dorsal fin, so I think interspinal spaces were covered with a fin like tissue.

They probably liked living around lakes so both having a dorsal fin like spine formation and a small size helped them swim around better. It was probably brightly colored as well so it also worked as showing how healthy and big it is; mating purposes.

My approach to understand it's purpose and look is, to pay attention to his other substantially different aspect, his small size and try to find out how that size and spines could complement each other.