Branisella
Name:
Branisella
(after Leonardo Branisca, the palaeontologist who discovered the
first remains).
Phonetic: Bran-e-sel-la.
Named By: R. Hoffstetter - 1969.
Classification: Chordata, Mammalia, Primates,
Platyrrhini.
Species: B. boliviana
(type).
Diet: Herbivore/Frugivore?
Size: Uncertain due to lack of remains.
Known locations: Bolivia - Salla Formation.
Time period: Chattian of the Oligocene.
Fossil representation: Teeth and fragmentary remains
of the skull and jaws.
At
first glance the lack of fossils might make Branisella
not seem an
important primate, but here you need to appreciate two things;
where the fossils have been found and how old they are. Dating to
the Chattian stage of the Oligocene period about twenty-six million
years ago, Branisella was and at the time of
writing still is the
oldest known primate discovered in South America. More popularly this
makes Branisella the oldest known New World Monkey.
Fossil
evidence from other primate genera points to an Old World
(Africa/Eurasia) origin for primates, and this is the stem for a
large element of confusion as to how Branisella
ended up in South
America, since during the Oligocene, South America was detached and
isolated from the other continents. Popular theory is that
Branisella, or the immediate ancestors of,
floated across the sea
upon rafts of vegetation that may have been thrown clear from the
mainland home by extremely powerful storms. This is not a huge
stretch in itself, but palaeontologists are divided as to exactly
where such life rafts could have originated from. Unfortunately very
little of the skull and mandible of Branisella is
known, and nothing
of the post cranial skeleton has so far been located. What elements
that have been discovered have not only been interpreted as being
similar to Old World primates of the Oligocene, but also to the now
extinct omomyids, a group of tarsier-like primates. If the old
world connection is correct, then Branisella
might have come to South
America upon rafts that floated across the Atlantic Ocean from Africa.
If the omomyid connection is the correct one, then the point of
origin would be across the Central American Seaway from North America.
Unfortunately at the time of writing it is impossible to interpret
anything more than this, though future discoveries may help to piece
things together more completely.
Because
a post cranial skeleton is still unknown, it is impossible to
establish either a definitive size estimate or lifestyle for
Branisella. However the teeth of Branisella
do have high crowns,
and usually these kinds of teeth are found in animals that do a lot of
grinding since the higher crowns extend the useful life expectancy of
the teeth from the increased wear. Indeed, the first set of molar
teeth in the jaw have been seen to be considerably more heavily worn
than the molars at the back of the mouth. This could be a sign of the
processing of tough food plants, though the lack of sharp cutting
edges and cusps could be a sign of a diet of soft fruit which could be
mashed by unspecialised teeth. It is also worth remembering for
consideration that Branisella like other monkeys we
see today would
have foraged for whatever food was available, geographically and/or
seasonally, and may have adapted its diet and feeding behaviour
accordingly.
The
presence of heavily worn grinding teeth may also mean that Branisella
spent time on the ground since the plants that would cause this kind of
wear would be most common on or near the ground. Also other monkey
genera that have reduced tooth crowns and grinding wear (the opposite
of the teeth of Branisella) are usually seen to
be either folivores
(leaf eaters) or frugivores (fruit eaters) that spend most of
their lives in the upper tree canopy where vegetation is generally
softer because it does not need to grow as strong.
Another
thing to note about Branisella is the discovery of
a partial orbit that
when compared to others to reconstruct the missing remainder was seen
to be particularly small. This means that Branisella
likely had small
eyes that would have not let much light through because of the reduced
area, and this in turn means that Branisella was
probably diurnal,
or rather active during the daytime only. The bright light of the
daytime meant that the eyes of Branisella worked
perfectly fine at
defining their surroundings, but the small size of the eyes also
meant that the upper limit for light passing through the eye would be
quite low, and during dusk and especially at night time Branisella
might not have been unable to see much more than just very dark shapes
against a black background.
Bringing
all of the above together, it might be possible to reconstruct
Branisella as a monkey that would descend down to
the forest floor
during the daytime where it foraged for tougher low growing vegetation
while also possibly browsing for ripe fruit that had fallen to the
ground. By foraging during daylight hours, Branisella
could also
have kept a lookout for potential predators that would have been easier
to see during the day. As night approached, Branisella
may have
then ascended into the tree canopy for the night where they would have
been relatively safe from ground predators that may have been more
active as they hunted under the cover of darkness.
Further reading
- New fossil materials of the earliest new world monkey, Branisella
boliviana, and the problem of platyrrhine origins, M.
Takai,
F. Anaya, N. Shigehara & T. Setoguchi - 2000
- The adaptations of Branisella boliviana, the
earliest South
American
monkey, R. F. Kay, F. Anaya & B. A. Williams. -
2001.
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