This
Cambrian sandstone contains two Cambrian
Scyphozoan jellyfish ichnofossils from the Krukowski
quarry in Central Wisconsin that has been under currently
intense scientific study since 2000.
The
Krukowski quarry yields ichnofossils that are the earliest evidence
of terrestrialization of animals in the fossil record.
The
sandstone matrix contains six jellyfish fossils, which
are rare in the quarry. The fossils are actually body cavity
infillings
that formed as the animal's ingested sand while pumping their
bodies in a futile attempt to escape their stranding on the
intertidal zone of a Cambrian shoreline. Because
these jellyfish body fossils are incredibly subtle in vertical
relief, the
specimen has been subtly stained. Some Blackberry Hill jellyfish
fossils approach two feet in diameter.
Being
comprised entirely of soft tissue (living jellyfish are about
95
%
water), unlike animals with exoskeletons (e.g., trilobites)
or skeletons
(vertebrates), jellyfish fossils are body fossils that are impressions
of the jellyfish. Such fossil impressions are rare throughout
the
fossil record. Appearing during the Ediacaran, jellyfish were some
of the most ferocious predators of the Cambrian marine environment.
The Blackberry Hill scyphozoan
fossils are
almost
surely
the result of a mass stranding on an ancient Cambrian beach, possibly
caused by a storm surge.
Phylum
Cnidaria (anemones, corals, jellyfish and sea pens) are among
the
most ancient animals and has one of the longest fossil histories
of metazoans. Though simple in body form, they remain ubiquitous
and widespread in modern marine environments. The earliest forms
in the fossil record appear in Ediacarian fauna of Southern Australia,
which dates to the Precambrian some 600 million years ago. Their
persistence is clear testament that old and simple animals can
be
enormously successful, and that the Cliché "climbing the evolutionary
ladder" is a misnomer; rather, life either adapts to the current
and changing environment, or perishes.
Reference: Hagadorn, JW., Dott, RH., Damrow, D, Stranded on a
Late Cambrian shoreline: Medusae from central Wisconsin, Geology
(39)
No. 2. |