Lotosaurus
Name:
Lotosaurus
(lotus lizard).
Phonetic: Moe-toe-sore-us.
Named By: Fa-kui Zhang - 1975.
Classification: Chordata, Reptilia,
Archosauria, Suchia, Paracrocodylomorpha, Poposauroidea.
Species: L. adentus (type).
Diet: Often depicted as a herbivore, there has
been speculation that it might have been durophagous (a shellfish
eater).
Size: Up to 2.5 meters long.
Known locations: China, Hunan Province -
Batung (Xinlingzhen) Formation.
Time period: Anisian of the Triassic.
Fossil representation: Initially known from a well
preserved skeleton, further skull and post cranial remains from many
other individuals have been attributed to the genus.
Sail-backed
rauisuchian
archosaurs are not especially well known, but they do
seem to have existed in reasonably high numbers, although it is also
important not to confuse them with the earlier sail-backed pelycosaurs
of the Permian such as Dimetrodon
and Edaphosaurus.
Upon is initial
discovery and description, Lotosaurus was thought
to have been one of
the ctenosauriscids, sail-backed thecodont archosaurs such as
Ctenosauriscus
and Xilousuchus.
Further fossils and later study have
now placed Lotosaurus within the Poposauroidea, a
sister group that
is separate to the ctenosauriscids.
Like
with others of its kind, Lotosaurus was a
quadrupedal reptile,
although it had a more rotund body than its relatives which have been
confirmed as being carnivorous. This indicates that Lotosaurus
was
not an overly active creature and as such was not a main predator of
the ecosystem. However this does not answer what Lotosaurus
ate
as the toothless jaws may have served two possible dietary
preferences, either that of a plant eating herbivore or a shellfish
eating durophagovore. Aside from being toothless, the only other
things of note about the jaws of Lotosaurus is that
the upper curved
down and that they seem to have had a powerful bite, but again these
do not give much indication towards one diet over the other.
What
does give us an indication as to what Lotosaurus
ate is analysis of the
fossil sites that Lotosaurus fossils are known
from. So far the one
unifying factor of these sites is that they were all wetland areas and
this is where many researchers sway more towards a duropohagous diet.
You see if Lotosaurus had lived in a dryer more
arid habitat, it
would have been feeding upon tougher plants that would require a strong
bite. The vegetation growing in wetland habitats however is usually
much softer and easier to pull free because plants do not have to
adapt to survive in a harsher climate. A strong bite would be an
unnecessary adaptation for a herbivorous diet in a wetland ecosystem,
but it would be very useful for cracking open shellfish that would
have also been abundant in a wetland habitat. Also remember that even
though it is not out of the question that archosaurs can adapt to a
vegetarian diet, others that Lotosaurus would
have been related to
(even if albeit distantly) were carnivorous. This means that even
Lotosaurus would quite possibly have had to survive
upon animal protein
that it obtained from the soft internal bodies of shellfish and since
these could not run away, Lotosaurus did not have
to adapt to become
an ambush or pursuit predator. On a final note about diet, the
shape of the jaws could have been adapted for pulling vegetation, but
could have also been used for picking out shellfish from amongst
others, the curvature of the jaw hooking around the round shells of
shellfish.
The
sail on the back of Lotosaurus obviously had a
purpose but so far there
is no way of confirming exactly what this purpose was.
Thermoregulation is a steadfast proposal for such features and one
that is entirely plausible. The one main problem with this theory
however is that not all rauisuchians had sails, in fact those that do
are so far in the minority when it comes to fossils. Additionally
those that do such as Arizonasaurus
and Ctenosauriscus have sails
that are quite different to the sails of Lotosaurus
and its kin.
Logic would dictate that if thermoregulation was the defining factor,
the sails would be more standardised in form. However this does not
put the theory to rest completely as since Lotosaurus
lived in wetlands
it would likely have a greater exposure to the cooling effects of
airborne moisture and water. It is also plausible that Lotosaurus
may
have even entered the water to feed upon plants or even shellfish and a
sail rising up from the back to catch the sun’s rays while other parts
of the body were submerged would have helped to keep body temperature
high.
A
theory that at least goes some way to explain the variance between the
sail forms of different genera is display. Here the sail would allow
Lotosaurus to recognise others of its own species as
well as possibly
be coloured or patterned to attract a mate. It is also important to
remember however that a feature such as sail doesn’t have to have just
one purpose and may have in fact worked to all of the above theories.
Further reading
- A new thecodont Lotosaurus, from Middle Triassic
of Hunan. -
Vertebrata PalAsiatica 13:144-147. - F. -K. Zhang - 1975.
- Taphonomy, geological age, and paleobiogeography of Lotosaurus
adentus (archosauria: poposauroidea) from the middle-upper triassic
badong formation, hunan, china. - Palaios. 33 (3): 106–124. - Cedric J.
Hagen, Eric M. Roberts, Corwin Sullivan, Jun Liu, Yanyin Wang, Prince
C. Owusu Agyemang, Xu Xing - 2018.
- New age constraints for the Middle Triassic archosaur Lotosaurus:
Implications for basal archosaurian appearance and radiation in South
China. - Palaeogeography, Palaeoclimatology, Palaeoecology. 521: 30–41.
- Jun Wang, Rui Pei, Jianye Chen, Zhenzhu Zhou, Chongqin Feng &
Su-Chin Chang - 2019.
Random favourites
 |
 |
 |
 |