A genus of Australian mammal renowned for 14-hour suicidal sex marathons has added two more species to its ranks.

But the Queensland scientist who named the cute marsupials is worried one of the species is already under threat, not least because of its mating habits.

The Tasman Peninsula dusky antechinus (Antechinus vandycki) is under threat. Credit:Gary Cranitch, Queensland Museum

The antechinus is famous for breeding so ferociously the male's immune system collapses and he dies.

"Every year the males actually have a mass die off after one to three weeks of mating," Queensland University of Technology mammalogist Dr Andrew Baker said.