When the type hierarchy paradigm fails

Is there any solution to a problem like this?:

Type TAnimal

Type TUnderwaterAnimal Extends TAnimal

Type TFish Extends TUnderwaterAnimal

Type TMammal Extends TAnimal

Type TDolphin Extends TUnderwaterAnimal,TMammal?????

Not using pure extension but decoration.


This means:

Type TDolphin extends TAnimal
field mammal:TMammal
field underwater:TUnderwaterAnimal

...