From DEREK AGER
I think the supposed Permo-Triassic extinctions have been grossly exaggerated
(‘The day the world nearly died’, 25 January, and Letters, 8 February).
Part of the problem is the way people compartmentalise the data. If you
only have such information as ‘Devonian to Permian’ then inevitably the
number crunchers will ‘prove’ a ‘mass extinction’ at the end of the latter
period.
If we consider the three main groups of fossils used in the Palaeozoic,
the graptolites were extinct before the Permian, the trilobites were reduced
to a handful by Permian times and the brachiopods at least coped with the
transition. Permian type brachiopods are found in the Lower Triassic of
Greenland, trans-Caucasia and southern China. It is never enough to look
at the evidence from one’s own back yard or even one’s own continent.
When I dealt with a major group of brachiopods for the monumental R.
C. Moore Treatise on Invertebrate Palaeontology, our distinguished editor
inserted a paragraph about the big changes at the end of the Palaeozoic.
I had to ask him to withdraw this, because it just was not true. Admittedly,
the names changed and the classification changed; even the names of parts
of the anatomy changed, but I was able to trace all my lineages through
from the Palaeozoic to the Mesozoic.
Though environmental factors were important, notably the matter of worldwide
marine salinity (as suggested by Al Fischer), I think the organic changes
are largely a matter of psychology rather than palaeontology, simply because
Palaeozoic specialists rarely study the Mesozoic and Mesozoic specialists
rarely study the Palaeozoic.
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Derek Ager Swansea, Wales
