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Atlantochelys mortoni
Topic Started: Mar 25 2014, 04:48 PM (3,248 Views)
Taipan
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Atlantochelys mortoni

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Scientific Classification
Kingdom: Animalia
Class: Sauropsida
Order: Testudines
Suborder: Cryptodira
Family: Protostegidae
Genus: Atlantochelys
Species: Atlantochelys mortoni

Atlantochelys mortoni is a fossil species, the only representative of the genus Atlantochelys . It was a sea turtle giant of the family Protostegidae , who lived in the Late Cretaceous . Known from very fragmentary remains, we know little about it.

Discovery and description
The first mention made ​​of the kind was published in the Proceedings of the Academy of Natural Sciences of Philadelphia , March 13, 1849, which are reported two interventions Louis Agassiz :
"Professor Agassiz Some observations made ​​upon the Crocodilus clavirostris of Morton, and charaterized it as a distinct genus under the Proposed name Sphenosaurus . aussi He refferd to the remains of an enormous fossil Chelonian, in the collection of the Academy, and found in the green sand of New Jersey. Being allied to the Colossochelys of India, Professor Agassiz proposed for it the name of Atlantochelys mortoni "
(Professor Agassiz made ​​some observations on the clavirostris Crocodilus Morton, and characterized it as a distinct genus, under the proposed name of Sphenosaurus . He also refers to the remains of a huge fossil chelonian in collection Academy, and found in the greensand of New Jersey. Hitherto up of Colossochelys India, Professor Agassiz proposed for the name of Atlantochelys Mortoni ).
The only known fossil to date is a fragment of humerus , which remains the proximal half. The humerus resembles that of Desmatochelys by its appearance, but it is much thinner. The entire humerus should be about the size that of the Archelon, which however it differs in appearance. It suggests, anyway, an animal of a very large size.
The exact location is unknown, but we know that the fossil was extracted in green sandstone Cretaceous County Burlington, New Jersey
Ren Hirayama has classified its kind within the family Protostegidae in 1997.

Closely related species
Lehman and Tomlinson note in 2004 1 the similarities between the species they describe Terlinguachelys fishbecki, and known fossil Atlantochelys unique, environments deposits of both species also correspond. Given the differences in proportions of 2 , it is unlikely that both belong to the same species, but the authors consider that the two species may be related.

Dimensions
Given the fragmentary nature of the fossil remains, it is very difficult to have a precise idea of the size of Atlantochelys . OP Hay 3 believes that the humerus must have dimensions similar to that of Archelon , although its shape is quite different. According to Lehman & Tomlinson, Atlantochelys would be roughly twice as large as Terlinguachelys , for which the length of the shell is estimated at 1.5 m. These estimates give the image of a turtle very large, exceeding three meters long, comparable to those of other giant turtles dimensions as Archelon, Protostega or Cratochelone .

Synonyms
Probably due to lack of fossils, types Atlantochelys and Protostega were often confused and considered synonyms . In this case, the grandfather rule to apply, it is the term of Atlantochelys which is preserved ( Protostega was described in 1872), and " Atlantochelys gigas "is a synonym current Protostega gigas .
Othniel Charles Marsh itself, perhaps because the kind Protostega was described by his great rival, paleontologist American Edward Drinker Cope , do not recognize the validity and never mentions the term " Protostega "him preferring that of Atlantochelys 4 .
As Marsh, many paleontologists Atlantochelys use the term to describe several species of Protostegidae, attached to the genus Protostega or other. This results in a confusion of description of the type, including with regard to its abundance and distribution, as a large number of sources dealing 's Atlantochelys actually do mention other species.
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Taipan
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Monster turtle fossils re-united

By Jonathan Amos
Science correspondent, BBC News
25 March 2014 Last updated at 02:35

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The two halves were discovered at least 163 years apart

Two halves of a fossil bone found more 160 years apart have finally allowed scientists to scale one of the biggest sea turtles that ever lived.

Atlantochelys mortoni was originally described from a broken arm bone, or humerus, found in the 1840s in the US state of New Jersey.

Remarkably, the missing portion has also now been unearthed.

The fossil fragments are a perfect match, and indicate A. mortoni must have been 3m from tip to tail.



"When we put the two halves together, we were flabbergasted," recalls Dr Ted Daeschler, from the Academy of Natural Sciences of Drexel University, Philadelphia.

"We said, 'no - that can't be!' We even turned them around trying to show they didn't match, but they're obviously supposed to be together," he told BBC News.

The re-united fossils will be described anew in a forthcoming issue of the Proceedings of the Academy of Natural Sciences of Philadelphia.

Both parts come from Cretaceous sediments, 70-75 million years old, in Monmouth County, New Jersey.

Very little is known about the discovery of the distal end - the end nearest to the elbow.

It received its first description from the famed naturalist Louis Agassiz in 1846. For years, it was assumed the bone was picked up in Burlington County.

But then amateur fossil palaeontologist Gregory Harpel picked up the proximal end - the end nearest the shoulder - from a brook in the neighbouring Monmouth district.

"I picked it up and thought it was a rock at first - it was heavy," Mr Harpel said.

Rocks tend not to have markings from shark bites, and so he quickly realised the find was something far more significant.

Together, the bone fragments give a much clearer view of A. mortoni, a species that would have looked very similar to the modern loggerhead - apart from its size.

"This turtle was a monster, probably the maximum size you can have for a turtle," said Dr Daeschler.

"Scientifically, we now know a lot more about this creature.

"Most importantly, we now know precisely which rock formation the original came out of, and so we can more precisely know its age, and we can be much more confident about finding additional material in that same formation and therefore telling more about A. mortoni."

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A 3D scan of the broken turtle limb: There is evidence of shark damage

http://www.bbc.com/news/science-environment-26717415
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