Geoscience Reference
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deteriorating during the latest Cretaceous. These findings are consis-
tent with an abrupt extinction scenario."
5
1
Not surprisingly, Clemens and Archibald, among others, dis-
agreed. Clemens, for example, citing studies by Peter Dodson,
5
2
which he said showed a decline in diversity, held firm: Any viable
hypothesis of the causal factors of dinosaurian extinction must
account for the evidence of decrease in generic diversity."
5
3
Sheehan
and Fastovsky countered by also quoting Dodson: "There is nothing
to suggest that dinosaurs in the . . . Maastrichtian were a group that
had passed its prime and were in a state of decline."
5
4
The work of the good folks from the Milwaukee Public Museum
drives a nail in the coffin of arguments for the gradual decline of the
dinosaurs. In an interview published in 1994, looking back, Clemens
appeared to doubt the earlier evidence: "The 'Ghastly blank,' the un-
fossiliferous meter or so separating the stratigraphically highest dino-
saurian bones and the iridium-enriched layer, might well be the prod-
uct of leaching of fossils from the uppermost Hell Creek by acidic
ground waters derived from the widespread Tullock Swamps."
5
5
Reviewing this debate, a territorial chauvinism becomes obvi-
ous. Dinosaurs lived on every continent, yet the entire argument
about their extinction is based on evidence from one small area in
eastern Montana where, as Dale Russell pointed out in his review of
Archibald's topic
(Dinosaur Extinction and the End of an Era
56
),
"tab-
ulations of dinosaur species are based on about 100 incomplete
skeletons."
5
7
On the basis of this limited sample, from a geologically
complicated and minute fraction of dinosaur-land, some paleontolo-
gists have made the most categorical statements about dinosaur ex-
tinction. Yet surely, as we saw at Zumaya, local conditions can cause
a blank. Perhaps for unknown reasons, the dinosaurs simply left that
part of the Hell Creek area. In the Raton formation in Colorado, the
tracks of duck-billed hadrosaurs are found only 37 cm below the
iridium layer.
5
8
Since tracks are not reworked and required a living,
breathing dinosaur, this proves that the dinosaurs lived to within a
few thousand years of the K-T boundary. In Mongolia, more dino-
saur species are found in the latest Cretaceous than below it.
5
9
In
China, dinosaur fossils are found so close to the K-T boundary that
some say they actually transcend it.
6
0
In the Deccan, dinosaur egg-
shells are found in an intertrappean bed just at the boundary.
6
1
All
this evidence shows that the dinosaurs did not go extinct well
before the K-T boundary, but lived right up to it. If a blank does
exist, it is not so ghastly after all, but merely, once again, an artifact
of the Signor-Lipps effect.
