What is this deeply weird humanoid corpse washed up on an Australian beach?

Earlier this week, Alex Tan found this bizarre humanoid creature washed up on Maroochydore Beach in Queensland, Australia. From News.com.au:

Step forward University of Queensland Associate Professor Stephen Johnston, who told the Courier-Mail the animal was most likely a swollen, waterlogged brushtail possum.

"The skull and hindlimb give the clues," he said.

"The animal was probably washed down into the ocean during the floods."

Sure, that's what They want us to think. How far is Marochydore Beach from Lake Baikal!?