# Killer Whales are a type of Dolphin

**URL:** <https://boards.straightdope.com/t/killer-whales-are-a-type-of-dolphin/715564>\
**Category:** Great Debates\
**Created:** [March 21, 2015, 2:26am UTC](https://boards.straightdope.com/t/killer-whales-are-a-type-of-dolphin/715564 "2015-03-21T02:26:43Z")\
**Posts on this page:** 2\
**Page:** 4

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**Author:** ![Darwins\_Finch](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/darwins_finch/32/20304_2.png) [@Darwins\_Finch](https://boards.straightdope.com/u/Darwins_Finch)\
**Post date:** [April 1, 2015, 1:31pm UTC](https://boards.straightdope.com/t/killer-whales-are-a-type-of-dolphin/715564/61 "2015-04-01T13:31:44Z")

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> [@Irishman](#):
>
> Okay, this is partially a matter of unclear presentation on wikipedia and partially my fault for relying so heavily on wikipedia.
> 
> […]
> 
> Can you see how that says that the link between fish and mammals goes through amphibians, and how Synapsida is a branch of reptiles? Of course, terms keep getting redefined, which makes it hard to follow.

Well, our earliest tetrapod ancestors (pre-Amniota) would have been “amphibians”, in the paraphyletic sense. But, precisely because “amphibian” is a paraphyletic group, we, as the descendents of those pre-amniote tetrapods, are not ourselves amphibians (indeed, a monophyletic “Amphibia” would be synonymous with Tetrapoda). In the same way, we are not “fish”, since “fish” is paraphyletic, and generally excludes everything in Tetrapoda (a monophyletic Fish clade would probably be synonymous with Vertebrata).

So, in essence, we are what our ancestors were if we are talking about monophyletic groups; we (or whatever other group we might talk about) are not what our ancestors were if we are talking about paraphyletic groups. We (and killer whales, while we’re at it) are tetrapod vertebrates, but we are not amphibian fish. Or amphibians, or fish.

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**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\
**Post date:** [April 1, 2015, 5:15pm UTC](https://boards.straightdope.com/t/killer-whales-are-a-type-of-dolphin/715564/62 "2015-04-01T17:15:02Z")

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> [@Darwins\_Finch](#):
>
> So, in essence, we are what our ancestors were if we are talking about monophyletic groups; we (or whatever other group we might talk about) are not what our ancestors were if we are talking about paraphyletic groups. We (and killer whales, while we’re at it) are tetrapod vertebrates, but we are not amphibian fish. Or amphibians, or fish.

I think that’s probably the root of the problem. The paraphyletic groups are the result of early attempts at classification based upon appearance before descent was really understood. That’s why modern classification is trying to get rid of paraphyletic groups from the official classification, though it requires redefining some terms along the way, which fosters confusion.

I am trying to be flexible and adaptable to the new info. I think I have a much more nuanced understanding of “species” and evolution from that standpoint than most people. It’s the cladistics I’m trying to catch up on.

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