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certainly no burden, and is usually a pleasure, to make such studies. The fos-
sils of Sucia are an example.
Ammonites are the greatest fossil treasures to come from Sucia. Yet
here and there one can discover fossils easily mistaken fot ammonites, until
one looks a bit closer and sees that these particular shells are simpler, less el-
egant. Their chamber edges form simple wavy lines, rather than the flowery
contacts so characteristic of the ammonite design. They are fossils of nau-
tiloid cephalopods—a group represented today by the chambeted nautilus—
cousins of the ammonites.
Although the nautilus has been studied for centuries, many questions
about it remain unanswered. Is the nautilus a very ancient creature or a very
new one? Is it a living fossil (a designation first proposed by Charles Darwin
for organisms with long fossil records bereft of evolutionary change) ? Is it the
last of its kind or one of the first? Does it have many relatives or very few?
And perhaps most important, why should anyone care about these odd ani-
mals? For me, at least, the hook is that this endangered body plan, so rare
among swimming animals in today's seas, was once clearly the rule, not the
exception.
The nautilus has two great claims to fame. First, because its shell so
closely resembles that of the ammonites, it can be used to understand bettet
the complex workings of the intricate ammonite shell, which must have
evolved as a compromise between protection and a form of buoyancy con-
trol. Studying still-living creatures as a means of understanding the past is
one of the most powerful of all time machines, and in this case, the nautilus
seems to give us an accurate glimpse far back into time.
Second, as I hope to show in this chapter, the nautilus does appear to
be a living fossil, a form that has existed for millions or even tens of millions
of years without change. We have discoveted that some fossil nautiloids
closely resemble the living species. This realization has come about only be-
cause detailed studies of the nautiloids show the evolutionary relationships
of the distinct species. The classification and systematic zoology of the nau-
tiloids have enabled us to identify them as living fossils. The way in which
we study the evolution of animals and plants—including the nautiloid
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