Lourinhanosaurus
Name:
Lourinhanosaurus
(Lourinh� lizard).
Phonetic: Lore-in-han-o-soer-us.
Named By: Mateus - 1998.
Classification: Chordata, Reptilia,
Dinosauria, Theropoda, Allosauroidea, Sinraptoridae.
Species: L. antunesi (type).
Diet: Carnivore.
Size: Around 4.5 meters long for the type
specimen, later research has speculated that Lourinhanosaurus
may
have reached 8 meters long when fully grown.
Known locations: Portugal - Lourinha Formation
Time period: Kimmeridgian to Tithonian of the
Jurassic.
Fossil representation: Partial post cranial remains
including vertebrae, limb and foot bones, ilia, pubis, and
ischia. Gastroliths were also found with the type specimen.
Additional remains including around 100 fossil eggs have been
referred to the genus.
Lourinhanosaurus
is a tantalising enigma for palaeontologists as although vastly
incomplete the remains seem to reveal a sinraptorid theropod (the
theropod group typified by Sinraptor).
If true then this would make
Lourinhanosaurus the first sinraptorid to be
discovered outside of
China, but other palaeontologists have suggested that
Lourinhanosaurus might also be a megalosauroid
(more closely related
to Megalosaurus).
Classification
issues aside, the discovery that really made palaeontologists scratch
their heads were the presence of gastroliths in association with the
Lourinhanosaurus remains. In an herbivorous
dinosaur this would not
be that unexpected, but the fragmentary remains of Lourinhanosaurus
are enough to reveal a theropod of the kind that has been dug up the
world over as a meat eater. Additionally palaeontologists are quite
satisfied that the stones could not have been swallowed accidentally
when the individual fed upon a herbivorous dinosaur.
However
while it is unusual for a predator to use gastroliths, it is not
altogether unknown. The grinding effects of the stones would have
been able to tenderise meat that had been swallowed, useful since
predatory dinosaurs were not good at chewing and they could at best
only swallow chunks of meat. It is also perhaps not impossible
that Lourinhanosaurus was a specialised predator
that might have eaten
crustaceans and shellfish which needed gastroliths for the shells to
crack. Unfortunately this is pure speculation in the absence of the
parts that could answer the question. Without a skull, it would be
impossible to identify any specialised feeding adaptations, and other
remains with the gastroliths might reveal parts of what was inside the
stomach at the time of death, but these first need to be found.
One
final thing to remember upon this subject is that during the Jurassic
Europe was not a single large land mass like it is today, and an
animal that could adapt to different food sources, particularly the
creatures like one might expect upon a beach ecosystem, would have an
advantage in the survival stakes. It could also be that
Lourinhanosaurus like other theropod dinosaurs may
have changed its
ecological niche during different phases of its life. Tyrannosaurs
by
example seem to have been very fast and agile predators when only a few
years old, making them well suited for chasing the smaller and faster
ornithopod dinosaurs. In later life they grew much bigger and no
longer had the agility to hunt these swifter dinosaurs which also no
longer offered a sufficient return in calories, so the adults
switched to hunting larger and heavier dinosaurs. This niche
specialisation also allowed juveniles and adults of the same species to
coexist in the same ecosystem without competing with each other for the
same food.
When
younger and smaller, Lourinhanosaurus may have
frequented coastal
environments which were far more extensive in Jurassic Europe. Here
they would be able to feed by either hunting smaller dinosaurs or
raiding tidal pools for fish and crustaceans, the latter two choices
requiring the use of gastroliths. Lourinhanosaurus
that survived to
adulthood may have grown too large to support themselves by this and
switched to a greater reliance upon hunting other dinosaurs, again
the two generations avoiding competition with one another for the same
resources.
Lourinhanosaurus
is usually credited at being around four and a half meters long and
this is certainly true for the type specimen. The type specimen
however is thought to represent an immature individual and later
analysis and study has led to an upper estimate of eight meters long
for an adult individual. This would make Lourinhanosaurus
a large
theropod dinosaur for the Jurassic, but within the realms of upper
size for the European theropods.
The
discovery of around a hundred eggs, some of which contain fossilised
embryos has been very exciting. These eggs are around thirteen
centimetres long and were attributed to Lourinhanosaurus
on the grounds
that they were found not far away from the Lourinhanosaurus
type
specimen.
Further reading
- Lourinhanosaurus antunesi, a new Upper Jurassic
allosauroid
(Dinosauria: Theropoda) from Lourinh� (Portugal) - Mem�rias da Academia
de Ci�ncias de Lisboa 37: 111–124. - O. Mateus - 1998.
- Upper Jurassic theropod dinosaur embryos from Lourinh� (Portugal) -
Mem�rias da Academia das Ci�ncias de Lisboa 37, 101-110. - I. Mateus,
H. Mateus, M. T. Antunes, O. Mateus, P. Taquet, V. Ribeiro & G.
Manuppella - 1998.
- Upper Jurassic dinosaur and crocodile eggs from Paimogo nesting site
(Lourinh�- Portugal). - Mem�rias da Academia de Ci�ncias de Lisboa 37:
83–100. - M. T. Antunes, P. Taquet & V.Ribeiro - 1998.
- The Large Theropod Fauna of the Lourinha Formation (Portugal) and its
Similarity to the Morrison Formation, With a Description of a New
Species of Allosaurus - J. R. Foster & S.
G. R.M. Lucas, eds.,
Paleontology and Geology of the Upper Jurassic Morrison Formation. New
Mexico Museum of Natural History and Science Bulletin 36. - O. Mateus,
A. Walen & M. T. Antunes - 2006.
Random favourites
 |
 |
 |
 |