Florist Rebecca Dale, 26, told John Booth ''are you taking the p**s?'' as he kissed his son goodbye - then grabbed the victim's hair and sank her teeth into the side of his head.
Booth managed to break free following a violent struggle which left him with blood pouring from the wound.
The 31-year-old discovered that part of his outer ear was missing when he returned to his car.
After driving to the hospital, he was told by a doctor that the pinna of his left ear had been chewed off.
Booth also suffered a burst lip when he was punched in the face and his T-shirt was was torn up in the assault.He had to have stitches for his wounds and is now disfigured for life.
At Manchester Crown Court, Dale admitted causing grievous bodily harm but escaped with 12 months jail suspended for two years.
The court heard Dale and Booth had been in a relationship for seven years and had a son together in 2010 but he dumped her in Autumn 2015.
The incident occurred on Christmas Day 2015 when Dale and her new boyfriend were entertaining relatives at her house in Burnage, Manchester.
Prosecutor Wayne Jackson said: ''Mr Booth picked up the boy from Rebecca’s house at about midday and took his son home.
The agreement was that he was to return the boy to mum at 3pm but it didn‘t quite work out like that and they got to mum's at about 3.25pm.
“John Booth rang the defendant’s mother to let her know that he was outside as he didn't want direct contact with her. But the defendant came to the door and as Mr Booth kissed his son goodbye, the defendant said, “Are you taking the p**s?” She was angry.
“Mr Booth asked her what she was on about and pointed out that he was only 25 minutes late. But no sooner had he said that the defendant attacked him, punching him to the head, grabbing his face and ripping his top.
“She burst his lip as he was saying to her that he had done nothing wrong, to get off him and asked her what she was doing.
"She then took hold of his hair and pulled his head down and then bit his left ear. He kept telling her to get off and eventually she did.