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Post by Infinity Blade on Oct 29, 2016 5:24:58 GMT 5
Impressive. How massive would that P. macromerus be?
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Post by Grey on Oct 29, 2016 13:56:35 GMT 5
~20 tonnes.
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Post by Grey on Oct 29, 2016 15:34:04 GMT 5
S. popularis may have been a macropredator.
BEYOND THE SHONISAURUS DEATH CULT: NEW INSIGHTS INTO THE
ECOLOGY AND LIFE HISTORY OF THE EARLIEST GIGANTIC MARINE
TETRAPOD
KELLEY, Neil P., Vanderbilt University, Nashville, TN, United States of America;
IRMIS, Randall, University of Utah, Salt Lake City, UT, United States of America;
RASMUSSEN, Cornelia, University of Utah, Salt Lake City, UT, United States of
America; DEPOLO, Paige E., University of Nevada, Reno, Reno, NV, United States of
America; PYENSON, Nicholas, Smithsonian Institution National Museum of Natural
History, Washington, DC, United States of America
Ranging up to 15 m in length, the Triassic ichthyosaur Shonisaurus popularis was
the first marine tetrapod to attain truly gigantic proportions. Shonisaurus is famous both
for its size and for exceptional fossil concentrations found in the Upper Triassic
(Carnian–Norian) Luning Formation in central Nevada. An assemblage of 6–9 skeletons
concentrated on a single 250 m2
bedding plane is preserved as an in-situ public display at
Berlin-Ichthyosaur State Park. Additional multi-individual accumulations of Shonisaurus
occur at other sites in the area, but other marine tetrapods are conspicuously absent.
Although the apparent mass mortality preserved in the display quarry has garnered
much attention, the paleobiology of S. popularis remains enigmatic despite a rich fossil
record. As part of a detailed reappraisal of the site, we produced high-resolution digital models of the fossils in the display quarry and conducted extensive field surveys.
Ichthyosaur fossils remain locally abundant and we discovered new material, notably the
well-preserved partial jaws and skull of an individual much smaller than those in the
display quarry. We also re-evaluated type material and additional specimens, including
fossils from other Nevada ranges pointing to a broad distribution of Shonisaurus within
the region.
The gigantic size of Shonisaurus suggests a novel ecology relative to
contemporaries. Previously, the apparent absence of teeth associated with adult
Shonisaurus skeletons inspired comparison to both baleen and deep-diving toothed
whales and suggestions of filter or suction feeding. We located multiple dentigerous S.
popularis jaws and isolated teeth, in the field and existing collections, including a jaw in
the display quarry. These fossils confirm the presence of teeth in all ontogenetic stages.
These robust, occasionally carinate teeth, set in individual sockets, likely played a role in
prey capture or processing and indicate a macropredatory niche rather than filter or
suction-feeding.
Our new data span a wide ontogenetic series, including the jaw of a small individual,
probably an embryo or neonate. These indicate Shonisaurus occupied the area at multiple
stages in its life history. Though the mechanisms behind the mass death assemblage
remain a topic of investigation, our improved understanding of the paleobiology of S.
popularis helps to constrain possible scenarios and is potentially consistent with previous
suggestions of reproductive aggregations in a partially restricted environment devoid of
other marine reptiles.
Grant Information
Smithsonian Small Grants Fund
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Post by Grey on Nov 8, 2016 9:03:08 GMT 5
This new data about S. popularis makes me wonder if it could have been the same in S. sikanniensis.
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Apex
Junior Member
Posts: 207
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Post by Apex on Nov 10, 2016 0:59:51 GMT 5
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Post by Grey on Nov 10, 2016 22:14:38 GMT 5
A large piece of bone from a P. macromerus mandible found in the Dorset coast. It is reported to have been close to the hinge. The measurements are 11 inches long.4 1/2 inches wide and the largest alveoli is 2 1/4 inches. This part of the jaw is the narrowest [ hence why i believe its the back of the jaw] and as it tapers out the alveolis get larger as does the width of the jaw.The tooth is a cast of an original tooth and firs perfectly in the 2 1/4 inch wide tooth socket. I'm going to try to extrapolate some mandible total size>body size from it. Anyone wants to test it too ? coherentsheaf theropod blaze  |
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Post by theropod on Nov 11, 2016 17:10:04 GMT 5
10m is a stretch. Using the estimated skull length of 1.2m, the largest it gets with Tylosaurine proportions is 9.2m, but that’s using an old figure from Russell (1967) that certainly doesn’t base on an accurately restored spine curvature and tailfin. Using Scott Hartman’s Tylosaurus pembinensis as a guide its 8.2m. That is actually reasonably large, there are Tylosaurus individuals that size (although I don’t know how mature they are), but it’s not a contender for the biggest mosasaur specimen and certainly not in the same league as some of the taxa discussed on this thread.  |
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Post by Grey on Dec 27, 2016 11:47:09 GMT 5
Big "Liopleurodon" tooth found in Russia a few months back.  Would be interesting to extrapolate a skull size. Seems pretty massive. |
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blaze
Paleo-artist 
Posts: 766
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Post by blaze on Jan 24, 2017 9:05:58 GMT 5
Remember the large Mosasaurus quadrate mentioned in Lingham-Soliar (1995)? the one that suggested an skull length of 2m using the scalebars? one abstract in the 5th Triennial Mosasaur Meeting mentions a giant quadrate from the Natuurhistorisch Museum Maastricht collection being of exceptional size, catalogue number is different but it's probably the same since its found in the same institution and it wouldn't be the first time Lingham-Soliar gets the number wrong. This quadrate is said to be 215mm tall, so only 29% larger than the one of NJSM 1105, which has a 123cm long lower jaw, suggesting an skull length of 1.6m, the same as the 90cm dentary.
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Post by Grey on Feb 21, 2017 11:47:14 GMT 5
saurian.maxmediacorp.com/?p=1479Nathan Van Vraken seems positive 17-18 m Mosasaurus exist. Nathan VV on January 30, 2017
I would not use Carnivoria as any source of reliable information. Consult peer reviewed literature and or scientists. 17-18m specimens have been discussed at various technical meetings based off of fragmentary material. Mosasaurs could in theory, have gotten to whale sizes at least if the K-Pg never occurred. Isotope data, fragmentary specimens, and modeling supports this.
Measurements can get skewed, no one is perfect like the editors. I’m assuming you are basing off the Lingham-Solier material.
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Post by Grey on May 30, 2017 21:18:52 GMT 5
Responses from Eberhard Frey about the MoA :
- is there a new paper in preparation about it ?
> Not yet, because the specimen is distributed in two institutions.
- how complete it is by now ?
> 75-80%. Excavation was finished end 2005.
- how large are the vertebra in it ? I've read in the papers 20 cm but some media articles report 30 cm.
> The anterior thoracic vertebrae are about 200 mm in Diameter. The height of the neural spine is 400 mm.
- what is the most likely size estimate of the specimen ? In medias I read 15-18 m but the latest scientific papers I've read (McHenry 2009, Frey & Stinnesbeck 2014) are more about 12-14 m .
> 12 to 14 is more correct, but the animal the attacked the monster was way bigger.
- is it really a young, immature specimen nowhere close to its adult size or is it possibly the result of paedomorphy (reportedly observed in large adult pliosaurs specimens).
> Difficult to say with 1 specimen at hand.
- if so, is there really a general scientific agreement that the adults may have been around 25 m as I've read in some medias ?
> When looking at the bite marks, 20 m come easily into reach.
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Post by spartan on Jun 1, 2017 20:54:39 GMT 5
Was it this attack that killed the monster?
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Post by Grey on Jun 2, 2017 6:42:06 GMT 5
There are two bite marks, one healed the other not. The reportedly biggest bite mark is healed.
I always find strange that such a huge, larger predator would have failed to kill with such a bite on the skull a smaller individual. Benson said that during the healing process a callus could have removed part of the bone. Also Buchy reported the marks as being oval. Pliosaurs teeth are not that shape so an enlargement seems possible.
The strong possibility that the MoA could be an adult specimen as in the case of the Svalbard material, casts more doubt about much larger specimens than it was.
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Post by spartan on Jun 3, 2017 3:34:05 GMT 5
Maybe the attacker was from a whole other, even bigger species.
But yes, it would be nice to have direct evidence for 15m+ pliosaurs for once.
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Post by Grey on Apr 9, 2018 23:11:31 GMT 5
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