To complete the picture of the Sauropods, we must add that the
whole class is characterised by the extraordinary smallness of
the brain. The twenty-ton Brontosaur had a brain no larger than
that of a new-born human infant. Quite commonly the brain of one
of these enormous animals is no larger than a man's fist. It is
true that, as far as the muscular and sexual labour was
concerned, the brain was supplemented by a great enlargement of
the spinal cord in the sacral region (at the top of the thighs).
This inferior "brain" was from ten to twenty times as large as
the brain in the skull. It would, however, be fully occupied with
the movement of the monstrous limbs and tail, and the sex-life,
and does not add in the least to the "mental" power of the
Sauropods. They were stupid, sluggish, unwieldy creatures,
swollen parasites upon a luxuriant vegetation, and we shall
easily understand their disappearance at the end of the Mesozoic
Era, when the age of brawn will yield to an age of brain.
The next order of the Deinosaurs is that of the biped
vegetarians, the Ornithopods, which gradually became heavily
armoured and quadrupedal. The familiar Iguanodon is the chief
representative of this order in Europe.
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