Yangtze is Bonnie's pet pug.
This is actually the only book where Yangtze is seen in, as he is killed on the night of the Dumb Supper. Everyone assumes it was Damon who did it until Katherine reveals it was her in The Fury. Apparently, he "tasted bad".
Yangtze was presumedly brought back to life by the Guardians in The Hunters: Phantom.
The Hunters: MoonsongEdit
While trying to point out why Damon isn't the best boyfriend material, Meredith asks if Elena remembers that one time he killed Yangtze. Elena comments that she doesn't want to talk about it right now, and that it was Katherine who killed him anyway.