From Lindsay Field
Devon
The explanation of why trilobites died out surely is the opposite to the one
given by Danita Brandt of Michigan State University
(This Week, 26 July, p18).
If the trilobite arthropod had 20 segments and it shed its cuticle one
segment at a time, then a bite from a predator would have to be pretty accurate
to hit and penetrate the exposed, unprotected soft tissue of one-twentieth of
its total segments. Unless the predator had very narrow jaws, surely the other
19 segments would cushion the bite and prevent penetration.
This would also, by implication, limit the number of predator species to the
very small, or those with jaws powerful enough to penetrate the armoured
cuticle.
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If the arthropod developed fewer body segments, then the ability of the
cuticle to withstand a bite and protect the exposed soft tissue would be
severely compromised, and would also have the effect of increasing the range of
predator species, which may have evolved subsequently to include those of
intermediate size.
Thus, overwhelmed by predators, the fate of the trilobite would have been
sealed.
