Re: Extinction scenarios

[John Bois <jbois@umd5.umd.edu>]

On Tue, 18 Aug 1998, Thomas R. Holtz, Jr. wrote:

> Checking the earlier Table 5.1 (pp. 84-85) from which the graph on p. 126 is
> derived, one can find that the eutherians concerned comprise only six
> species in two families: the gypsonictopid _Gypsonictops illuminatus_ and
> the palaeoryctids _Batodon tenuis_, _Cimolestes cerebroides_, _C. incisus_,
> _C. magnus_, and _C. propalaeoryctes_.  Of these, all but _G. illuminatus_
> are marked as "rare".

Thank you.  I had not xeroxed that table.

> It should be noted that while it is fair to say that there is 100%
> survivorship of known eutherian species in the Hell Creek into the Tullock
> Formation, it is not fair to extrapolate from this 100% survivorship is
> necessarily descriptive of all eutherian clades everywhere in the world.

But I think it _is_ fair to say that the world-wide adaptive radiation of
placentals began in the late Cretaceous and continued (amplified on into
the Tertiary.  This point, while not necessarily condemning the
bolide-as-sufficient idea, is not a friend to it.
By the way, how would a paleontologist justify Archibald's data with the
following favorite of mine (in Benton's Vert. Pal. text 1997 but from
Sloan and Van Valen 1986):
The relative abundance of non-avian dino and (all) mammalian genera over
the K/T transition

MYA           Dinosaurs           Mammals
63              0                   46
64              0                   34
65              0                   30
66             10                   36
67             18                   10
68             16                    6
69             22                   -
70-73          22                   -
74             28                   -
75             23                   -
76             14                   -

I'm just reading these of a non-gridded graph.  But the trend is accurate.
I'm assuming since Benton put it into his latest edition that the data is
still valid.