Complex sentence: Recent morphological and molecular-based classifications reveal the sirenians to be the closest living relatives of elephants, while hyraxes are closely related, but form an outgroup to the assemblage of elephants, sirenians, and extinct orders such as Embrithopoda and Desmostylia.
Split into simpler sentences: Recent morphological and molecular-based classifications reveal the sirenians to be the closest living relatives of elephants. While hyraxes are closely related, they form a taxonomic outgroup to the assemblage of elephants, sirenians, and extinct orders such as Embrithopoda and Desmostylia.