In c# how can one define a static method that is to implemented by all derived/implementing types? I know you cannot define a static method within an interface.

Basic premise is like this:

Say for example I have a base class of Organism.
Derived types would be Human and Dog.

I want a method which can return to me say the number of legs that a given organism has. So Human would be 2, dog would be 4, etc.

I can make such a method an instance method, but it doesn't make much sense because its going to be the same method for all Dog types, and the same for all Human types, etc.