Their lungs improved and their skeletons became heavier and stronger, better able to support the weight of their bodies on land.
ðɛɹ lˈʌŋz ɪmpɹˈuːvd ænd ðɛɹ skˈɛlᵻtənz bɪkˌeɪm hˈɛviɚ ænd stɹˈɔŋɡɚ, bˈɛɾɚɹ ˈeɪbəl tə səpˈoːɹt ðə wˈeɪt ʌv ðɛɹ bˈɑːdiz ˌɔn lˈænd.