is just something intrinsic about ammonites (and nautiloids) that
is aesthetically pleasing to humans, and perhaps as well to our
less sentient cousins in Kingdom Animalia. Could it be Phi, the
Golden Number (= 1.61803….), ubiquitous in nature? Could
the pleasure be the ammonite's Fibonacci spiral, observed in galaxies,
the arrangement of leaves around a stem, and the shape of ammonite
and nautiloid shells?
+ 1**2 + . . . + F(n)**2 = F(n) x F(n+1)
is it the ammonite's shells, originally composed of aragonite,
a carbonite mineral, which is unstable at standard temperature
and pressure, and reverts to calcite over tens of millions of
years. Actually, the shells inner surfaces had layers of nacre,
or mother of pearl, an iridescent organic-inorganic composite
(aragonite plates separated by proteins) secreted by the epithelial
cells of some mollusk. During fossilization, the nacreous layer
of some ammonites was chemically transformed into an iridescent
material called ammolite, which is aragonite with varying mineral
impurities that is considered to be an opal-like gemstone.
it is the shape or the shell, or both, ammonite fossils possess
an inherent beauty seemingly pleasing to everyone’s eyes.
Just as Fibonacci numbers are apparently ubiquitous in nature,
so too are the ammonites, having left an extensive fossil record.
From the time of their appearance, descending from nautiloids
in the Upper Silurian to
Lower Devonian, to their extinction with the dinosaurs, ammonites
left their shell remains across the globe. Ammonites cyclically
declined and radiated through the many extinction events that
punctuated the Paleozoic
Eras and were extremely prolific in the Mesozoic. Ammonites are
also a favorite subject of the artistically inclined individual
that may cut, polish and mount them in various ways. The specimens
below were chosen more for beauty and diversity than to tell a
tale of ammonite evolution.