Here
we have an association plate of Cambrian
Scyphozoa jellyfish, from the famous Krukowski quarry in Central
Wisconsin that is currently under intense scientific study. The
Krukowski quarry yields ichnofossils that are the earliest evidence
of terrestrialization of animals in the fossil record. The animals
have yet to be described in the literature, though publication can
be soon anticipated.
Two
types of jellyfish fossils are found in the quarry, smaller tentacle
jelly fish, which are rare in the quarry, and the larger medusa
form of jellyfish. This particular specimen is from a new layer
with the first such tentacle jellyfish to be recovered in three
years. It is also the first layer to yield tentacle and madusoid
forms in association, as is the case in this specimen. This flagstone
plate contains two tentacle Scyphozoa, and a medusa measuring
about 4 inches in diameter.
It
comes from a particular horizon in the Mount Simon Sandstone formation
that also yields fascinating Diplichnites,
huge Jellyfish (Medusae)
and Climactichnites.
Jellyfish body
fossils are incredibly subtle, and therefore this specimen has been
subtly stained.
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. Jellyfish were some of the most ferocious
predators of the Cambrian marine environment. These fossils are
almost surely the result of a mass stranding on an ancient Cambrian
beach, possibly caused by a storm surge. Science believes jellyfish
fossils may only result from being stsanded on a beach, and subsequent
lack of predation and rapid burial by sediment or other material.
At least during the Cambrian there were no purely land-based predators.
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 clique' "climbing the evolutionary
ladder" is a misnomer; rather, life either adapts to the current
and changing environment, or perishes.
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