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characters that could he recognized in fossils. The traditional shell charac-
ters, such as shape, ornament, and sutute type, were useful but too few in
number to allow meaningful cladistic analysis. Luckily, just at this time a
wealth of morphological characters, buried deep in the middle of every nau-
tiloid, was discovered through the detailed work of Neil Landman of the
American Museum of Natural History.
The nautilus has long been known to hatch at a very large size: It
emetges from its egg with seven fully formed chambers and a shell diameter
of over an inch, which makes it the largest invertebrate, at hatching, in the
world. Indeed, it may have been this trait that enabled it to survive the gteat
Cretaceous mass extinction, for the nautilus appears to lay these eggs in very
deep watet whete they take a year to hatch, and it may have been the deep-
living juveniles, or even the unhatched eggs, that survived in this refuge.
When a young nautilus emetges from its egg, a distinct mark is left on its
shell. Landman began dissecting many types of fossil nautiloids to see whether
similar marks were found in ancient species as well. He discovered not only
that these marks did occur but also that many other types of characters could
be found in the hatching stages of all nautiloid fossils.
By combining these traits—shell shape complexity of sutures, orna-
mentation, and hatching stage—Saundets and I finally had enough charac-
ters to perform a meaningful cladistic analysis of fossil nautiloids. To our sur-
prise, these analyses showed the genus Nautilus to be extremely primitive.
Rather than being a descendant of some Late Tertiary (perhaps 30-million-
year-old) nautiloid genus such as Eutrephoceras or Hercoglossa, Nautilus ap-
pears to be derived from a much older ancestor, probably the Jurassic-aged,
180-million-year-old Cenoceras that our new genus Allonautilus so resembles.
Furthermore, rather than being the last-evolved nautiloid genus, it seems to
have been among the first of its family and the ancestor of most of the Ceno-
zoic Era nautiluses. There was only one problem: If Nautilus was so old, why
were there no fossils of it?
It turns out that there are many fossils that we can now confidently
place in the genus Nautilus. The first to point this out was the paleontologist
Richard Squires of California. Squires, a specialist in Tertiary-aged mollusks,
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