Why can't we all just count along?

I was researching a music parody post that will probably appear later in the week, and ended up doing a Google search for the words "types of dolphins." And I was surprised at what I found:

What are the 32 types of dolphins?

There are two major types of dolphins: oceanic dolphins and river dolphins. Within each of these groups there are thought to be around 40 different dolphin species.

There are 33 different types of marine dolphins, 4 types of river dolphins and 6 types of porpoises.

But an interesting fact is that there are over 45 types of dolphins.

I'm not a biologist, so I'm not sure why there's such a great divergence in these counts.

But bear this in mind when you hear an assertion that a fact of business is an accepted truth. And if you don't believe me, answer this question - how long should a business lunch last?