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over an inch in diameter, with seven fully formed septa. Soon we found other
nautiloid specimens squirreled away in various museum collections. Cut in
half, they also showed internal shell characters that, when added to other
shell and suture character states, gave telltale evidence of being—or in some
cases not being—members of the genus
Nautilus.
We had shown that
Nau-
tilus
lived in Cretaceous seas, and more recently we have found Jurassic spec-
imens that indicate that this wondrous creature may have lived as along as
200 million years ago.
A final outcome of all of this is the need to suppress hundreds of species
defined for various nautiloid genera. To date we can confirm only three (and
perhaps four) discrete species of
Nautilus:
the modern-day
N. pompilius,
per-
haps the modern day
N. macromphalus
(which may turn out to be a sub-
species of
N. pompilius),
and a ribbed species from the Cretaceous of Van-
couver Island. The others, including the hundred-million-year-old specimen
that Steve Gould resurrected from my mantle (now sitting safely, if less elo-
quently, in a dark museum drawer) may all simply be
Nautilus pompilius.
On
the basis of shell characters, that is certainly what they seem to be.
This raises a profound evolutionary question. Can any "species" exist
for such a long period of time? Although thete are many known cases of
gen-
era
lasting for a hundred million years, the persistence of a
species
for so long
is far more problematical, especially that of a species of a creature as complex
as a cephalopod. Wouldn't genetic drift—the rather random evolutionary
change that can affect any population—eventually result in a new species
over such immense periods of time? Or would our hundred-million-year-old
nautilus, if somehow brought back to life, happily and successfully mate with
a
Nautilus pompilius
from today's oceans? Is a hundred-million-year-old
species not a rare exception, but perhaps more common that we think? Are
there even billion-year-old species on earth, perhaps among the bacteria,
blue-green algas, or even flatworms, annelids, and mollusks as well?
