Growing up, when looking in textbooks and other references about plate tectonics, there was always the Indo-Australian (or Indian-Australian) plate, such as shown below:
But, recently it has been recognised that there are separate Indian and Australian plates, such as shown below:
Image source: An Introduction to Plate Tectonics
This would make sense given the differences in the collisional history of the two landmasses.
What tectonic structures delineate the split between the Australian and Indian tectonic plates?