A longer video, so here are the 2 important events:
00:00 Tyrannotitan begins its harassment
10:00 Tyrannotitan and Tyrannosaurus join forces against me, both die
I honestly thought I was a goner, but still wanted to try one last, desperate attempt at... at least killing one of them. And it worked. For both. This is my first Tyrannotitan kill as a TRex, I have been killed once by a group of 3 of them, although I must say it was my mistake (got stuck running away, then got pushed off a cliff).
Seems the new dinosaur was very hungry, practically starving to death, which is why I managed to kill it as well in the end.
Map: Gondwa