Complex sentence: The myriapods have traditionally been considered the closest relatives of the hexapods, based on morphological similarity, but new work has called this into question, and it appears their closest relatives may be the crustaceans instead.
Split into simpler sentences: The myriapods have traditionally been considered the closest relatives of the hexapods, based on morphological similarity. New work, however, has called this into question, and it appears their closest relatives may be the crustaceans instead.