Tethyshadros
Name:
Tethyshadros
(Tethys hadrosaur).
Phonetic: Tef-iss-had-ross.
Named By: Fabio M. Dalla Vecchia - 2009.
Classification: Chordata, Reptilia, Dinosauria,
Ornithischia, Ornithopoda, Hadrosauroidea.
Species: T. insularis
(type).
Diet: Herbivore.
Size: About 4 meters long.
Known locations: Italy - Liburnia Formation.
Time period: Late Campanian of the Cretaceous.
Fossil representation: Holotype almost complete
skull and post cranial skeleton preserved on a slab. Remains of
several individuals are known.
Tethyshadros
is without doubt one of the more interesting genera of hadrosauroid
dinosaurs. For a start hadrosauroids are not particularly well known
from Europe, though large ornithopod dinosaurs which were ancestral
to them are. Tethyshadros also seems to have
been a dwarf
hadrosaur, growing to an average length of four meters. This
reduction in size seems to have come about from a reduction in the post
cranial skeleton, as the skull is notably large in proportion to the
rest of the skeleton. The limbs are also relatively long and more
gracile than relative genera. This length and a reduction in digits
seem to have been adaptations for a greater reliance upon cursorial
(ground) movement.
The
small size of Tethyshadros seems to have been
caused by an effect
termed ‘insular dwarfism. This is where a population of animals
that find themselves living on a restricted landmass with limited food
resources will progressively grow smaller over successive generations.
This is because evolution would favour those individuals which did not
have to eat so much, so that they would survive to breed for longer,
and by extension a balance would be attained where a population level
could stabilise without outstripping the available food resources for a
given area.
How
a population of Tethyshadros came to be restricted
to an island has
already become a matter of debate. We know that ancestral forms of
the hadrosauroid dinosaurs, typicially iguanodonts, were present in
Europe all the way back to the Jurassic, and that various forms such
as Zalmoxes
and Rhabdodon
were still present at the end of the
Cretaceous. However in the original 2009 description of
Tethyshadros, Dalla Vecchia favoured the idea of
island hopping.
This is a very plausable notion as during the Mesozoic Europe was not
one major landmass as it is today; instead it resembled a collection
of random islands and archipelagos. It is quite possible that as time
progressed, sea levels altered, and lands shifted, some creatures
were able to exploit these changes to progress into new areas.
Tethyshadros
was named after the Tehthys Ocean, an ancient body of water that
once separated
the northern continents from the southern continents.
Further reading
- Tethyshadros insularis, a new hadrosauroid
dinosaur
(Ornithischia) from the Upper Cretaceous of Italy. - Journal of
Vertebrate Paleontology 29(4):1100-1116. - Fabio M. Dalla
Vecchia - 2009.
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