Travel Reference
In-Depth Information
Evidence of ancient predation
A seashell pressed to the ear will evoke the sound of surf, aural waves on
some far tropical beach, the tone of the sea. But any seashell records far more
than an imaginary surf. Shells bear the equivalent of a tree's rings, giving us
age and clues to environment; all shells maintain a record of their life and
times, and sometimes the time and manner of their death. One of the prop-
erties of sea shells—including
ancient
sea shells—is that they are faithful
recorders of age-old predation.
Much information about the past comes from reading the record of shell
breaks that offer an account of some ancient predatory attack. Interpreting
breaks in fossil shells is an important and widely used means of bringing the
past back to life. The shells and their breakage patterns, then, are the data.
But our interpretation of what caused those breaks can be far more ambiguous.
Many fossil shells show breaks. Sometimes the attacks that caused these
breaks killed the animal within. Often, however, the predator did not succeed
in killing its shelled quarry, leaving the organism to repair the breaks and, in
the process, leaving a scar behind, yielding fascinating infotmation about
who ate whom in ancient time. Sometimes, however, the investigators zeal
for such investigations outstrips the evidence. And when such excitement is
coupled with an incomplete or faulty understanding of how shell material
fails under pressure or point load, misinterpretations can ensue. The follow-
ing is just such a cautionary tale. It not only pitted those who understand the
mechanical and material properties of molluscan shell against those who
don't but also cast into sharp relief a clearly sensational explanation for fossil
evidence against a far more prosaic—yet in this case accurate—portrayal.
Ammonite shells often have round marks in them. Were these holes left by
the dramatic attack of a marine lizard of great size and strength or by the slow
rasping of a tiny snail shell over many years? Are these holes the bite marks of
a creature whose closest living relative is the Komodo dragon?
The Komodo dragon is a large lizard (up to 10 feet long) that now lives
only on several small Indonesian islands, where it preys mainly on small deer
and pigs, killing them with a saliva rendered poisonous by highly toxic bac-
