Name:
Bonitasaura
(La Bonita lizard).
Phonetic: Bon-it-a-sore-rah.
Named By: Sebasti�n Apestegu�a - 2004.
Classification: Chordata, Reptilia, Dinosauria,
Saurischia, Sauropodomorpha, Sauropoda, Titanosauroidea,
Nemegtosauridae.
Species: B. salgadoi (type).
Diet: Herbivore.
Size: About 9 meters long, possibly larger
when fully grown.
Known locations: Argentina, Rio Negro Province
- Bajo de la Carpa Formation.
Time period: Santonian of the Cretaceous.
Fossil representation: Lower jaw and partial post
cranial remains.
Bonitasaura
is a genus of what seems to have been fairly small titanosaurs
that
lived in Argentina during the Late Cretaceous. The holotype
individual seems to have been a subadult, which means that while it
was sexually mature, it still would not have been fully grown.
During this phase of its life though, actual body growth would have
been expected to be slowing down, so adults of the type species might
have been longer than nine meters though not by much. This is a stark
contrast to another South American titanosaur named Argentinosaurus,
which might be one of the largest titanosaurian sauropods of all time.
Bonitasaura
seems to have had a fairly stocky build with a relatively short neck
when compared to some other titanosaurs. The dorsal (back)
vertebrae also had high and robust neural spines indicating a points
for strong muscle attachments. This could indicate that while the
neck was short, Bonitasaura were still high
browsers that cropped
mouthfuls of food from the tree canopy.
A
surprising feature of Bonitasaura is that the lower
jaw is actually
more like that of a diplodocid, a type of sauropod that was quite
different from titanosaurian sauropods. This lower jaw had teeth
reduced in size towards the back while the front had a ridge that in
life would have been covered by a growth of keratin. The upper jaw,
missing at the time of description) would be expected to mirror this
so that the front of the mouth had a kind of small beak that formed a
shearing edge. Bonitasaura would feed by gripping
parts of plants and
trees by biting and holding with the teeth, and then using the beak
to slice and remove them so that the mouthful could be swallowed.
Sauropods are not noted for having very strong bite forces, but a
more muscular neck as that seen in Bonitasaura may
have provided the
necessary strength to cut plants against the shearing beak.
The
shape of the lower jaw also reveals that while the diplodocids seem to
have largely disappeared by the late Cretaceous, the titanosaurs
independently developed similar morphological features. This can also
help explain the noted occurrence of other diplodocid like jaws found
in association with titanosaurian skulls, as has been seen in another
genus named Antarctosaurus.
Bonitasaura
is named after the La Bonita Quarry where the holotype remains were
found. Because Bonita is a feminine Spanish word, the genus name
has been named as ‘saura’ which is also feminine as opposed to
‘saurus’ which would be masculine (both are Ancient Greek for
lizard). The species named B. salgadoi is in
honour of the
Argentine palaeontologist Leonardo Salgado.
Further reading
- Bonitasaura salgadoi gen. et sp. nov.: a
beaked sauropod from
the Late Cretaceous of Patagonia - Sebasti�n Apestegu�a - 2004.
- Postcranial anatomy of Bonitasaura salgadoi (Sauropoda, Titanosauria)
from the Late Cretaceous of Patagonia. - Journal of Vertebrate
Paleontology 35. 1–22. - P. A. Gallina & S. Apestegu�a. - 2015.