Re: No Cretaceous placental mammals?

[Jeff Hecht <jeff@jeffhecht.com>]

Yes, I meant placentals (mea culpa, mea culpa). 

The Slack et al paper is well worth looking up.  (Mol. Biol Evol 23 (6) 
1144-1155, 2006). It's available at 
<http://mbe.oxfordjournals.org/cgi/reprint/msj124?ijkey=zaRIuJ8ctNRqLkV&k> and 
well worth looking at their rooted tree, which takes the divergence of 
neognathae and paleognathae back to 98 million years ago. The two key fossils 
that calibrate it are Vegavis at 66 million and Waimanu (a primitive penguin) 
at 62 million.



At 10:52 AM -0700 6/22/07, T. Michael Keesey wrote:
>On 6/22/07, Dino Guy Ralph <dinoguy@sbcglobal.net> wrote:
>> Jeff Hecht writes:
>> "It is curious that living birds seem to have originated well before the
>> K/T, in contrast to mammals."
>>
>> If you'll forgive the Linnaean vernacular, I think that Jeff Hecht meant to
>> say something along these lines:
>> "It is curious that extant orders of birds seem to have originated well
>> before the K/T, in contrast to extant orders of mammals."
>
>That's even less curious than my interpretation (that he meant
>"placentals" instead of "mammals"), since it's essentially
>meaningless. "Order" doesn't have a good definition, but, when it
>comes to birds and mammals, you almost could define it as "any of
>certain clades originating in the early Cenozoic or Late Cretaceous".
>

-- 
Jeff Hecht, science & technology writer
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