Complex sentence: Compared to later aircraft carriers, "Ranger" was a relatively smaller ship, closer to "Langley" in tonnage, and initially it did not even possess an island; although a small one was added after construction.
Split into simpler sentences: Compared to later aircraft carriers, "Ranger" was a relatively small ship, closer to the preceding carrier, "USS Langley" in terms of tonnage. Initially it did not even possess an island; although a small one was added after construction.