[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Turtles and Crocodylians are not Reptiles - no? What are they?

On Sun, Jul 27, 2008 at 6:27 PM, Tim Williams
<twilliams_alpha@hotmail.com> wrote:
> Nick Pharris wrote:
>> Yes they are. The existence of a "Cetacea+Artiodactyla clade" that
>> excludes Mesonychia means that cetaceans are closer to hippos (as
>> artiodactyls) than they are to mesonychians. It's just that, under
>> Thewissen et al.'s phylogeny, cetaceans are not any closer to hippos
>> than they are to llamas, babirusas, chevrotains, mule deer, okapis,
>> etc., etc.
> Ummm... no, they're not, Nick.  While it is true that Thewissen &c's 
> phylogeny found Cetacea to form a clade with Artiodactyla to the exclusion of 
> Mesonychia, this does not automatically make cetaceans closer to hippos than 
> to mesonychians.  Cetaceans (plus raoellids) are at the base of the 
> Artiodactyla, and the Cetacea+Artiodactyla clade forms a trichotomy with 
> Mesonychia and _Andrewsarchus_.  The Raoellidae+Cetacea clade is recovered as 
> the sister taxon to the crown Artiodactyla clade (pigs, babirusas, hippos, 
> llamas, chevrotains, mule deer, cows, gnus, okapis, etc etc).  So, as Mike 
> Keesey pointed out, under Thewissen &c's phylogeny cetaceans are outside the 
> crown Artiodactyla.

I'm very confused, because what you just said sounds consistent with
what Nick just said. And your second sentence seems to contradict

According to you, the topology is (Andrewsarchus, Mesonychia, (crown
Artiodactyla*, (Raoellidae, Cetacea))). Therefore, cetaceans share a
clade with hippopotami (and other [crown] artiodactyls) which excludes

* which I think should just be called "Artiodactyla"

Put it all on a tree:

   |--Artiodactyla (incl. Hippopotamidae)

T. Michael Keesey
Director of Technology
Exopolis, Inc.
2894 Rowena Avenue Ste. B
Los Angeles, California 90039