There isn't a standard classification of quolls into 4 distinct types. However, there are 6 extant species of quolls, and they can be grouped by size and geographic distribution:
- Large Quolls: Eastern Quoll and Tiger Quoll.
- Medium-Sized Quolls: Spotted-tailed Quoll and New Guinea Quoll.
- Small Quolls: Brown Quoll.
- Endangered Quolls: Queensland Quoll, a critically endangered subspecies of the Tiger Quoll.
This is just one way to group quolls, and other categorizations are possible depending on the criteria used.