Complex sentence: Urocordylidae is divided into two subfamilies, Urocordylinae and Sauropleurinae, that are distinguished by the shapes of their skulls; urocordylines have short, blunt skulls while sauropleurines have longer, pointed skulls.
Split into simpler sentences: Urocordylidae is divided into two subfamilies, Urocordylinae and Sauropleurinae. The two groups are distinguished by the shapes of their skulls; urocordylines have short, blunt skulls while sauropleurines have longer, pointed skulls.