Travel Reference
In-Depth Information
Underneath the sea's turbid surface layer visibility improved, and our
time traveler was relieved to see the dim outlines of the bottom, far below.
He had never liked vertical descents, especially in very deep or murky water
where you lost sight of both the surface and the bottom. He swam down
quickly, chased by beams of shimmering sunlight, through a cerulean-blue
water column rich in tiny invertebrates and minnows, and he thought of the
hundred new species he was surely passing by. Now the bottom was visible,
coming up fast, and he gently dropped down onto its sandy surface, landing
on his knees, to be surrounded like a dream by a Mesozoic sea bottom fes-
tooned with multicolored algas: bright, current-wafted pennants in browns,
yellows, reds, and greens. But his eyes ignored the submarine flora; he
searched instead for old friends he had known only in death. He quickly saw
them in legions, quite alive, and he greeted them with the hoots of joy that
are the only underwater exclamation of a scuba diver.
The sandy bottom was slightly rippled, barely disturbed by the stronger
waves at the surface. The tubular, tentacled necks of clams whose shells were
deeply buried in the fine sand were scattered across the bottom in great num-
ber, and he wryly wondered what a chowder of these Cretaceous clams would
taste like. Snails large and small crawled by, leaving irregular tracks across
the sediment surface, while circular sea urchins rattled their pike-like spines
among the immobile inhabitants: the sponges, bryozoans, and hydrozoans
and a myriad of other colonial and solitary filter-feeding animals living in
their skeletal mansions and tenements. But of all the creatures visible, one
stood out. The bottom was littered with large clams both dead and alive.
These Cretaceous clams were distant relatives of the oyster and perhaps the
most ubiquitous residents of the Late Cretaceous seaways. By the end of the
Cretaceous Period, 65 million years before the time of humans, they would
be entirely extinct. But on this older sea bottom they were everywhere. They
sat atop the sediment, not buried in it like the other species of clams hete,
and their large, ribbed shells were crowded with colonies of encrusting in-
vertebrates. Bright mantle flesh extended partly over the inoceramid's shells,
making them look like the giant clam
Tridacna
of modern coral reefs, and
probably for the same reason, he thought:
Tridacna
clams harbor gardens of
