Evening star., 1935-02-26

Some 250, ,000, 900 years ago strange
little animal-perhaps the first four
legged, breathing creature to leave
any trace of its presence on earth
lived within q few hundred miles Of
Washington.
The only records Of it are some foot
prints in the ancient Allegheny rocks,
but these are so curious that from
them can be reconstructed the picture
of an animal midway in the process
of transition from a fish to an am
phibian. Such a reconstruction Is at
tempted, at least. by one OF the discov-
erers of the tracks, Bradford Willard
of the Pennsylvania Geological Survey
Several double rows of tracks were
found in rocks dating from the De-
vonian geological period, the beginning
of which is estimated by the United
States Geological Survey as approx
imately 292 900 900 years ago. Life
which left fossil evidences already had
existed in the world for about 200,-
900 900 years, but, SO far as Is known,
1t had been confined to the seas and
the crab-like trilobites Of the begin
ming still were sharing the shallow
oceans with the fishes.
Each row consists OF small. regu-
larly spaced imprints and Is exactly
duplicated by its companion row. But
alternate prints in each row are
strikinely. almost inexplicably, differ
ent. One is that Of an unmistakable
animal foot with sole, heel and nve
toes. The other is a claw-like track,
difficult to interpret. It Is somewhat
like the track of q large insect-except
that no insects or spiders were known
from the Devonian.
Mr.. Willard, after exhausting va
rious possibilities, concludes that these
tracks must have been those Of a four
legged creature walking through mud.
Furthermore, he deduces that the un-
mistakably animal footprints were
those of the strange little creature s
hind feet, which already had under
gone the evolutionary process, and the
others prints of the front appendages,
which were fms in the process OF be-
coming feet. It is also obvious that
the animal did not drag itself along.
but walked with its body OF the
ground. Otherwise there would have
been a continuous impression of its
belly in the mud, whereas all that can
be found is the occasional imprint OF
its tail. .
The PAGES often are staggered"
and. reports Mr.. Willard, show evi-
dence Of passing from q "hitching"
gate to true quadrupedal walking. It
was learning-a process that doubt
less extended for thousands Of years
to walk and trying to throw of its
ancestral habit of using its four limbs
as oars instead of legs, just as fishes
use their fins in swimming. It al
ready had gone a long way toward
true walking, but whenever it got
into minor difficulties, the tracks in
dicate, it reverted to the rowing"
method. Indications Of this also are
more common in those tracks which
appear to have been those Of younger
animals.
To understand the significance Of
these tracks, Mr.. Willard points out
in his report, it Is necessary to the
fishes. from whom sprang the amphi-
bians, from whom sprang the reptiles,
from whom sprang the mammals.
from whom sprang man.
1t now Is generally recognized
among paleontologists that that am
phibia were derived, some time in the
late Devonian, from family Of fishes
known as the crossopterygii. Living
close to shore at q time when the
seas were declining, they must quite
frequently have been left stranded on