both pondered and worried about the paucity of fossils found
that dated before the Cambrian. More than a century later
now know that arthropods lacking external exoskeletons walked
in the shallows, on the beaches, and ultimately made their
on land. Darwin would today be gratified that science has determined
that these transitional creatures had left there traces,
only footprints in the sand, substantiating there overarching
of the Precambrian/Cambrian boundary of time. This fossil
such evidence, coming from the history-making Blackberry
Hill (Krukowski quarry) in central Wisconsin that
recently came under intense study by Paleontologists, and descriptions
of a diverse fauna that apparently walked or floated upon an
is an ichnogenus normally attributed to arthropod locomotion.
The fossil trackway exhibits two parallel lines of
feet impressions. The animal was ostensibly striding on the
surface and leaving
no other impressions such as from the drag of a tail or other
body parts, like Protichnites.
The spacing of the foot prints along the track would
be wider at higher speeds.
Diplichnites shown to the right is unique owing to the obvious
large size of the animal, since the sides of the tracks are
some two inches apart. Note that this large specimen is the
half of the fossil (called hyporelief) (e.g., see Stranded
on a Late Cambrian shoreline: Medusae from central Wisconsin,
et. al., describing Ichnology). This
particular plate measures 775 by 140 (30 1/2 by 5 1/2 inches),
and a yardstick is shown to give perspective.
conjecture was that Diplichnites is the trace of a wandering
Myriapod, which brings to mind an ancient centipede (Chilopoda).
Given the spacing of these footprints, the centipede that
the tracks of the fossil to the right would have been an awesome
predator - perhaps the terror of the Cambrian beach some
billion years ago. Diplichites from other locations have been
attributed to trilobites. Many ichnofossils, Protichnites,
from the Mount Elk Group show drag traces putatively made
arthropod tails or other body parts, suggesting taxonomic identity
among crustaceans, aglaspids, chelicerates or euryipterid
group. The more accepted interpretation is now that the Diplichnites
from Blackberry Hill are deep footprints made in a preserved
by a thick microbial mat on which the animal walked.