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Re: Sauropodz r kewl WAS: silly conversation on 2012 US presidential race



On Wed, Apr 18, 2012 at 8:01 AM, Anthony Docimo <keenir@hotmail.com> wrote:
>
>  We've demolished groups such as Pachyderma, relocating its members (rhinos, 
> elephants, etc) to their true relatives...and yet the tuatara, aardvark and 
> pangolin are set aside in their own groups with no near extant relatives.
>
> so, if there is no way to quantify it, why do we keep them separate?

But they aren't "separate". Sphenodon* is in Lepidosauria, along with
its extant sister group, Squamata. Orycteropus afer is (possibly) in
Afroinsectiphilia along with its extant sister groups, Macroscelididae
and Afrosoricida. Manis** is in Ferae, along with its extant sister
group, Carnivora.

* two living species
** eight living species

The fact that they have large extant sister groups is simply an
artifact of which groups went extinct. The fossil record has
stem-tuataras, stem-aardvarks, and stem-pangolins.

> (I don't know if there are any dinosaur equivilents of the aardvarks and 
> pangolins, cladistically speaking)

Being a small extant taxon with a much larger sister group? There are
plenty of dinosaurian taxa like that. How about Struthio (sister to
the rest of Palaeognathae), Anhimidae (sister to Anseres), or Coliidae
(sister to the rest of Dendrornithes)? Or Palaeognathae (sister to
Neognathae)?

-- 
T. Michael Keesey
http://tmkeesey.net/