Tamar Braxton's domestic dispute with her husband got so down and dirty, he bit into her hand ... according to a friend who called police.
TMZ obtained the 911 call made Sunday from the Ritz-Carlton in Atlanta -- the caller immediately tells the operator about the alleged bite, and Vincent Herbert fleeing the scene.
As you can imagine ... the operator's concerned an ambulance will be needed.
Neither Tamar nor Vincent is saying what really went down. We got them at LAX the next day, and they made it seem like all's right in their world.