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Elasmosaurus
Name:
Elasmosaurus
(Ribbon lizard).
Phonetic: El-lazz-mo-sore-us.
Named By: Edward Drinker Cope - 1868.
Classification: Chordata, Reptilia,
Sauropterygia, Plesiosauria, Elasmosauridae.
Species: E. platyurus
(type).
Diet: Piscivore.
Size: Upper size of up to 13-14 meters long.
Known locations: USA, particularly associated with
Kansas - Pierre Shale.
Time period: Campanian of the Cretaceous.
Fossil representation: Many specimens.
Today
Elasmosaurus is one of the best known plesiosaurs
in
the world, and
is the type genus for the Elasmosauridae. This group is noted for
having particularly long necks, proportionately even longer than the
more standard plesiosaurs. These long necks are composed of a large
number of cervical vertebrae that in Elasmosaurus
number seventy-one,
more than other plesiosaurs including fellow elasmosaurids. The
sheer number of vertebrae not only extend the length of the neck but
also provide greater flexibility for fine control of the head,
although very early reconstructions of Elasmosaurus
being able to coil
its neck like a snake are today considered to be very inaccurate and
impossible for a living Elasmosaurus to do.
Instead the neck would
have been held quite straight when resting with sideward movements
only occurring when necessary.
It
was the long neck of Elasmosaurus that was key to
its feeding method.
All Elasmosaurus would have to do was swim up to a
shoal of fish,
possibly from below so that it could hide its body in the slightly
darker depths, and use its neck to dart its head in and pluck out a
mouthful of fish. Approaching prey like a shoal of fish from below
would also silhouette themselves against the brighter surface water,
making them easier to define as well as removing the defence method of
flashing light off their shiny scales to confuse predators as they
turned and swam through the water. Such a method would have been a
reasonably efficient form of feeding as Elasmosaurus
would just have to
move its head and neck and not waste energy swimming after fast moving
individuals.
Key
to prey capture were the long and thin teeth that protruded from the
mouth of Elasmosaurus. These intermeshed together
so that when a fish
was caught between the jaws it was impaled upon the teeth so that it
could not wriggle free and escape. This kind of dentition is common
among other elasmosaurids as well as other piscivorous (fish eating)
animals such as skim feeding pterosaurs.
A defining characteristic
of Elasmosaurus is the fact that it has six teeth
in each premaxilla.
Because the teeth of Elasmosaurus were adapted for
prey capture rather
than biting clean through flesh, prey would need to have been
swallowed whole. Gastroliths have been found in association to
Elasmosaurus remains and its thought that the
grinding action of these
stones in its gut tenderised food for easier digestion.
Elasmosaurus
probably was not a fast swimmer, although if it used stalking tactics
to approach its prey from below it would not need to be. The
flipper-like limbs were rigid and well suited for providing efficient
locomotion through the water. Skeletal elements of the main body such
as the pectoral girdles were also well adapted to provide efficient
musculature support for the flippers so that that Elasmosaurus
could
paddle itself through the water with ease.
While
Elasmosaurus was beautifully adapted for an aquatic
life, the price
of these adaptations is that Elasmosaurus would
have almost certainly
been restricted to the marine environment. Because the paddle-shaped
limbs were so stiff they would at best been only just better than
useless for pushing its body along. Even when if Elasmosaurus
was
ever active in the shallows, it would still need to have kept its
body totally immersed so that the water could support its body weight.
More
‘classic’ depictions of Elasmosaurus shooting
its neck out of the
water are also unlikely as the longer the neck got, the more body
tissue such as bone and muscle was used to make up the neck meaning
more weight was added to it. More weight means that stronger muscles
would have been needed to support the neck when out of the water, and
study of the cervical vertebrae where the muscles attach indicates that
Elasmosaurus just did not have the muscles to move
its neck when it did
not have water to support the weight. Instead the muscles were only
strong enough to provide basic neck movements, which would be all
that was required of them when the neck was immersed in water.
While
no hard evidence currently exists for Elasmosaurus
either laying eggs
on land or giving birth to live young, most palaeontologists believe
that Elasmosaurus, and similar marine reptiles
would have given birth
to live young. The precedent is known to exist for other marine
reptiles like the ichthyosaurs
and nothosaurs
as far abck as the
Triassic and given the problems that
Elasmosaurus would have had just moving its body if
it ever found
itself out of the water make it extremely unlikely it could have laid
eggs on land. Today marine reptiles such as sea snakes can also be
observed giving birth to live young which indicates that as a group the
reptiles are capable of adapting to new methods to thrive in different
environments.
Elasmosaurus
discovery,
reconstruction and classification
The
palaeontological history of Elasmosaurus is a
turbulent one. First
discovered in 1868 by Dr. Theophilus Turner, the fossils were
sent to Edward Drinker Cope for study and identification. Cope had
never assembled a plesiosaur before but he had the idea the large
number of vertebrae mostly belonged in the tail which resulted in a
long tail and short neck. To Cope this made sense as the proportions
were similar to those of many modern lizards that also have short necks
and incredibly long tails.
The
next part of this story is a little hazy for exact details, but the
popular retelling of it has Othniel Charles Marsh realising that the
head was on the wrong end and ridiculed Cope for placing it in the
wrong place. However it seems that it was actually Joseph Leidy who
pointed this error out in a meeting in 1870, although given the
animosity already between Marsh and Cope at the time, its quite
possible that Marsh continued to use this case as an example to
discredit Cope’s work, hence the confusion. It is this criticism
that poured fuel onto the already burning fire that would become the
‘bone wars’, a fierce rivalry between Cope and Marsh that saw them
trying to out compete one another in terms of discovering new species.
Since
its naming back in 1868 many new specimens of Elasmosaurus
have
been recovered, and many of these were assigned their own species
within the genus. Many of these species continue to be mentioned
despite the fact that in 1999 the palaeontologist Ken Carpenter
conducted a study of the known Elasmosaurus fossils
at this point and
found that some of these did not belong as individual species, and
some of them even represented different genera. Today most
palaeontologists only recognise the original type species, E.
platyurus, as being valid.
Further reading
- On a new large enaliosaur. - The American Journal of Science, series
2 46(137):263-264. - E. D. Cope - 1868.
- Remarks on a new enaliosaurian, Elasmosaurus platyurus.
- Proceedings
of the Academy of Natural Sciences of Philadelphia. 20: 92–93. - E. D.
Cope - 1868.
- Remarks on Elasmosaurus platyurus. - Proceedings
of the Academy of
Natural Sciences of Philadelphia. 22: 9–10. - J. Liedy - 1870.
- North American plesiosaurs Elasmosaurus, Cimoliasaurus,
and
Polycotylus. - American Journal of Science. 4. 21
(123): 221–236. - S.
W. Williston - 1906.
- Elasmosaurus platyurus and a page from the
Cope-Marsh war. -
Discovery. 17 (2): 25–27.- G. W. Storrs - 1984.
- Revision of North American elasmosaurs from the Cretaceous of the
western interior. - Paludicola. 2 (2): 148–173. - K. Carpenter - 1999.
- Bonehead mistakes: The background in scientific literature and
illustrations for Edward Drinker Cope's first restoration of
Elasmosaurus platyurus. - Proceedings of the Academy
of Natural
Sciences of Philadelphia. 152 (1): 215–240. - J. P. Davidson - 2002.
- Elasmosaurid remains from the Pierre Shale (Upper Cretaceous) of
western Kansas. Possible missing elements of the type specimen of
Elasmosaurus platyurus Cope 1868?. - PalArch's Journal of Vertebrate
Palaeontology. 4 (3). - M. J. Everhart - 2005.
- Postscript to Everhart, M.J. 2005. "Elasmosaurid remains from the
Pierre Shale (Upper Cretaceous) of western Kansas. Possible missing
elements of the type specimen of Elasmosaurus platyurus
Cope 1868?" –
PalArch's Journal of Vertebrate Palaeontology 4, 3: 19–32. - PalArch's
Journal of Vertebrate Palaeontology. 2 (1). - L. F. No� & M.
G�mez–P�rez - 2007.
- Revised Vertebral Count in the "Longest-Necked Vertebrate"
Elasmosaurus platyurus Cope 1868, and Clarification
of the
Cervical-Dorsal Transition in Plesiosauria. - PLOS ONE. 8 (8). - S.
Sachs, B. P. Kear & M. Everhart - 2013.
- Captain Theophilus H. Turner and the Unlikely Discovery of
Elasmosaurus platyurus. - Transactions of the Kansas
Academy of
Science. 120 (3–4): 233–246. - M. J. Everhart - 2017.
- Scattered and Shattered: A Brief History of the Early Methods of
Digging, Preserving and Transporting Kansas Fossils. - Transactions of
the Kansas Academy of Science. 120 (3–4): 247–258. - J. P. Davidson
& M. J. Everhart - 2017.
- The Mystery of Elasmosaurus platyurus Cope 1868 – Where is the rest
of the type specimen?. - Transactions of the Kansas Academy of Science.
121 (3–4): 335–345. - J. P. Davidson & M. J. Everhart - 2018.
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