YOU SAID:
my mother never ate diplodocus
INTO JAPANESE
私の母はディプロドカスを食べたことがない
BACK INTO ENGLISH
My mother has never eaten diplodocus.
INTO JAPANESE
私の母はディプロドカスを食べたことがありません。
BACK INTO ENGLISH
My mother has never eaten diplodocus.
That didn't even make that much sense in English.