Ostafrikasaurus
Name:
Ostafrikasaurus
(Ostafrika lizard - derived from Deutsch-Ostafrika which is the
former name for what was once known as ‘German East Africa’).
Phonetic: Ost-af-ree-ka-sore-us.
Named By: Eric Buffetaut - 2012.
Synonyms: Ceratosaurus stechowi?
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Theropoda, Megalosauridae, Spinosauridae,
Baryonychinae.
Species: O. crassiserratus
(type).
Diet: Carnivore/Piscivore.
Size: Unknown due to lack of fossil remains.
Holotype tooth is 49 millimetres long.
Known locations: Tanzania - Tendaguru
Formation, Upper Dinosaur Member.
Time period: Mid Tithonian of the Jurassic.
Fossil representation: Isolated teeth.
The
holotype tooth of this genus was originally described by the German
palaeontologist Werner Janensch in 1920 as belonging to the genus
Labrosaurus. The first reassignment came about
when Labrosaurus was
declared to be a synonym of Allosaurus,
but the teeth in question
were not seen to be similar to those known for Allosaurus,
so they
were moved over to another Jurassic theropod called Ceratosaurus.
Again the teeth were not a perfect match for this genus which led to
them being considered to be of a different and hitherto unknown
theropod, all the way until 2012 when the palaeontologist Eric
Buffetaut established a new genus of spinosaurid dinosaur with them.
Because
Ostafrikasaurus is based upon the description of a
tooth there is a lot
we don’t know about this dinosaur. For instance no one can say how
big it was, what exactly it ate, and even though it has been
classed as belonging to a spinosaurid, it might not have looked
exactly as spinosaurids are so far known to. However it is the mere
classification of Ostafrikasaurus that is important
here, and for two
reasons. First, the holotype tooth has been identified as coming
from a late Jurassic era deposit, something that at the time of
description and writing makes Ostafrikasaurus the
oldest known
spinosaurid. Before its description other spinosaurid genera
including Spinosaurus,
Baryonyx,
Suchomimus,
Irritator,
Oxalaia,
and Ichthyovenator
amongst others were all identified as
coming from early Cretaceous deposits that are many millions of years
younger that the deposit for Ostafrikasaurus.
The
second important area for Ostafrikasaurus is the
actual form of the
teeth. The holotype tooth is not like the long and thin teeth that
are adapted for spearing which are seen in later spinosaurid genera.
Instead the holotype gets quite a bit broader at the base given it a
form that is similar to the more general theropod tooth form. The
tooth is serrated and has up to ten denticles every five millimetres on
the distal side, thirteen denticles every five millimetres on the
medial side. This is more than later spinosaurid which has led to the
notion proposed by Buffetaut that the number of denticles on
spinosaurid teeth reduced as the spinosaurids became more advanced.
This essentially means that if and when other early spinosaurid genera
are found, the older they are, the higher the number of teeth
denticles they would be expected to have. The form of the holotype
tooth is also the inspiration of the type species name, O.
crassiserratus which translates to English as ‘thick
serrated’.
As
already mentioned without the discovery of a skull or a skeleton
(ideally both) no one can say for certian what Ostafrikasaurus
looked like or how it lived, though it is possible to make
surmisations about what needs to be looked for. Spinosaurids are
often described as having crocodile-like snouts, a very loose
description given the way crocodiles can vary in form, but one that
does illustrate how the snouts of spinosaurids are proportionately much
longer than those of other more generic theropod dinosaurs.
Ostafrikasaurus might have already developed the
long snout
characteristic of spinosaurids, it might have been short like an
early theropod, or anywhere in-between. It is still uncertain if
Ostafrikasaurus had the sensory snout features that
have been proposed
for other spinosaurid genera.
Spinosaurids,
where the fore limbs have been preserved, have also been noted for
having enlarged claws on their hands, and again Ostafrikasaurus
might
have already had this development, or had a form that was similar to
but not yet as well developed. Ostafrikasaurus
might have also been
more of a generalist hunter rather than a specialist fish hunter,
though even later more specialised genera such as Baryonyx
are known
to have eaten dinosaurs, though the circumstances for this are
unknown (the dinosaur may have been scavenged rather than killed and
then eaten).
The
future of the genus Ostafrikasaurus may be a
dubious one since the
history of palaeontology has consistently proven that it is very
difficult to attribute skeletal remains to a genus that is based only
upon teeth. Though with that said, the genus Troodon
was
established on teeth long before skeletal remains were definitively
proven to belong to it. Regardless of what the future may hold for
the Ostafrikasaurus genus, the holotype tooth
came from a dinosaur
that would have lived in an ecosystem that saw the presence of other
dinosaurs such as the stegosaur Kentrosaurus,
the sauropods
Dicraeosaurus
and Giraffatitan
and the theropod Elaphrosaurus.
Further reading
- Spinosaurid teeth from the Late Jurassic of Tendaguru, Tanzania,
with remarks on the evolutionary and biogeographical history of the
Spinosauridae. - Eric Buffetaut - 2008.
- An early spinosaurid dinosaur from the Late Jurassic of Tendaguru
(Tanzania) and the evolution of the spinosaurid dentition. - Eric
Buffetaut - 2012.
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