Leptictidium
Name:
Leptictidium
(Graceful weasel).
Phonetic: Lep-tik-tid-e-um.
Named By: Heinz Tobien - 1962.
Classification: Chordata, Mammalia, Theria,
Leptictida, Pseudorhyncocyonidae.
Species: L. auderiense (type), L.
ginsburgi, L. nasutum, L. sigei, L. tobieni.
Diet: Omnivore.
Size: Up to 90 centimetres long, 20
centimetres high (depending upon species).
Known locations: Germany.
Time period: Throughout the Eocene.
Fossil representation: Many specimens, while often
incomplete, some complete skeletons are known. Stomach contents
have also been preserved.
One
of the most striking characteristics of Leptictidium
are the
well-developed hind legs that are considered to have made this creature
one of the rare few bipedal mammals (the others being humans and the
macropods such as kangaroos and wallabies). The biggest problem
with Leptictidium however is that we can’t be
certain as to how it
moved about. Many people may remember how Leptictidium
was depicted
in the 2001 BBC series Walking with Beasts (alternatively known
as Walking with Prehistoric Beasts) where in the episode ‘New
Dawn’ Leptictidium was shown to hop about in a
similar fashion to
kangaroos. This form of locomotion is supported by the shape and
proportion of the legs which would allow for powerful tendons to run
across the length of the bones and act as springs for jumping.
However analysis of the bones has concluded that skeletally
Leptictidium was too weak to withstand the forces
involved with
repeated jumping, which leads to the idea that Leptictidium
may have
been more of a runner that could occasionally jump when necessary.
The only possible compensation for the weak skeletal structure is that
the ankles and pelvis were loosely connected, so it might be that
soft tissue of living Leptictidium was arranged to
withstand some of
the shocks of jumping. Regardless of whether it was a runner,
hopper or indeed both, Leptictidium was am agile
creature that would
have had a fairly easy time moving around the forest floors of
Eocene era Europe.
Some
of the best preserved remains of Leptictidium
reveal both animals and
plants in the stomach area, although animals such as insects and
lizards seem to be far more common. This suggests that while
Leptictidium could and would eat plants, it had a
greater tendency to
hunt for small animals. One feature that probably helped Leptictidium
to forage for food was the elongated snout, the presence of which
is indicated by the shape of the snout bones of the skull. This snout
could have been worked into small areas to detect things like hidden
fruits and insects, possibly to the point of being able to manipulate
them out into the open. The fore limbs of Leptictidium
which are much
smaller than the rear limbs seem to be well suited for grasping and
holding onto things which means that Leptictidium
may have held food
and prey in between its forelimbs as it ate just like how a squirrel
will eat nuts today.
In
terms of size there is a lot of variation between species of
Leptictidium. So far the type species of L.
tobieni is the largest
at up to ninety centimetres long (half of which is tail). By
contrast the smallest species of Leptictidium is L.
auderiense is
only six centimetres long. Further differences in species are
established upon the basis of varying dentition and skeletal
proportions. Leptictidium disappears from fossil
deposits at the end
of the Eocene period and this disappearance is usually credited as
being part of a shift in the habitat from warm subtropical forests to
more open plains and woodland. This change meant that Leptictidium
no
longer had the cover of the forest for protection and with new
predators coming onto the scene, Leptictidium
waned in numbers until
an inevitable extinction.
Further reading
- Leptictidium nasutum n sp., ein
Pseudorhyncocyonide aus dem Eoz�n der
"Grube Messel" bei Darmstadt (Mammalia, Proteutheria). -
Senckenbergiana Lethaea 66. - Adrian Lister & Gerhard Storch -
1985.
- Leptictidium tobieni n sp., ein dritter
Pseudorhyncocyonide
(Proteutheria, Mammalia) aus dem Eoz�n von Messel. - Cour.
Forsch.-Inst. Senckenberg 91: 107–116, 9 Abb. - Wighart von Koenigswald
& Gerhard Storch - 1987.
- The postcranial skeleton of early Oligocene Leptictis
(Mammalia:
Leptictida), with preliminary comparison to Leptictidium
from the
middle Eocene of Messel. - Palaeontographica Abteilung a -Stuttgart-
278(1):37-56. - Kenneth D. Rose - 2006.
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