bu hayvanın vücudusu?
vücut -> vücudum ; vücudun ; vücudu
What's wrong with "Hayvanın vücudu bu"?
What happened to vowel harmony?!
Vucüdu is accusative. The root of the word is vucüt.
Vucüdu = vucüd (t transformed to d) + u (accusative suffix) which was added according to the four way vowel harmony because the last vowel of the word is ü
Forgot to mention that t transforms into d because it is followed by a vowel. Check https://www.duolingo.com/skill/tr/Accusative/tips-and-notes