Complex sentence: Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders; with over 5,000 identified species, it has roughly twice as many species as the largest of the mammal orders, the Rodentia.
Split into simpler sentences: Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders, with over 5,000 identified species. It has roughly twice as many species as the largest of the mammal orders, the Rodentia.