Their main bones are hollow and lightweight and are fully ossified and the vertebrae interlock with each other and have articular processes.
ðɛɹ mˈeɪn bˈoʊnz ɑːɹ hˈɑːloʊ ænd lˈaɪtweɪt ænd ɑːɹ fˈʊli ˈɑːsᵻfˌaɪd ænd ðə vˈɜːɾɪbɹˌiː ˌɪntɚlˈɑːk wɪð ˈiːtʃ ˈʌðɚ ænd hæv ɑːɹtˈɪkjʊlɚ pɹˈɑːsɛsᵻz.