Потребителски вход

Запомни ме | Регистрация
16.01.2016 16:42 - Encyclopedia Largest prehistoric animals Vol.1 Vertebrates part7 Pliosaurus-Mine’s bigger than yours
Автор: valentint Категория: Забавление   
Прочетен: 2547 Коментари: 0 Гласове:

Последна промяна: 30.04.2019 00:16

The Monster of Aramberri, Predator X, and other monster pliosaurs in the media and real.
During the past decade several dramatically named giant pliosaurs have hit the mainstream media, many claiming to be the biggest yet discovered. But only a trickle of peer-reviewed literature has been published to accompany these news stories. The lack of published data makes it really difficult to sift the facts from the fiction, and it’s easy to get the different stories muddled up, especially in the case of two identically sized congeneric pliosaur specimens from Svalbard: ‘The Monster’ and ‘Predator X’. So in an attempt to iron out the details and assess what we really know about all these specimens, here’s a short summary of the main players.
There is an unofficial "Premier League" in vertebrate palaeontology which consits of the animals which attract a lot of public attention. Its members include T.rex, Seismosaurus, Argentinosaurus, Giganotosaurus and so on - the biggest and fiercest extinct animals. When the BBC broadcast "Walking with Dinosaurs" they moved Liopleurodon ferox firmly into the Premier League. Here was an animal that made T.rex look like a kitten - 25 meters long and weighing 150 tons, an awesome predator that dwarfs anything before or since.
The problem is that Liopleurodon ferox was not 25 meters long, and did not weigh 150 tons. Something more…None of the known pliosaurs not even close to half of these dimensions.
It is hard to identify bones are being definitely those of Liopleurodon. Remains of top predators in general are rare - there aren"t as many of them as there are of animals further down the food chain. Our knowledge of the pliosaurs of the Oxford Clay in general has recently been greatly refined by Leslie Noи"s PhD thesis. His work has concentrated on skull morphology, so our knowledge of their postcranial anatomy is still rather limited. The largest skull definitely belonging to L.ferox are about 1.5 meters long, and if the head was about a seventh of the body length (as reconstructed by Tarlo) it would make the length a little over 10 meters. I have studied the bite marks left by Liopleurodon on the bones especially of Cryptocleidus, and by matching skull size to recognisable patterns of tooth marks would conclude that the normal size range was about 5 to 7 meters. Very rough calculations (based on measuring the volume of a plastic model of a pliosaur) suggest that the normal weight range was from about a quarter to three quarters of a ton, and up to around 2.5 tons for the biggest animals. This does not allow for changes in body proportion as animal increase in size, and it is not unlikely that larger animals were also proportionally bulkier, as is the case in modern crocodiles. Even taking this into account it seems unlikely that Liopleurodon reached weights of more than 5 tons.
There is evidence of a much larger pliosaur in the Oxford and Kimmeridge Clays. Very large isolated elements such as vertebrae and a large lower jaw have been found. These cannot be identified as Liopleurodon and it seems most likely that they belong to an unknown and very large taxon. A lower jaw, in the collection of the Oxford Museum is from the Kimmeridge Clay and reportedly measures 3 meters in length (though I haven"t measured it myself). Leslie Noй thinks it is from an undescribed taxon. Scaling up on the same basis as before, this would suggest an animal as much as 12-15 meters in length, and weighing therefore in the region of 10 tons. There have been unconfirmed reports of a lower jaw found on the Dorset coast measuring as much as 4 meters, which could therefore measure 16 - 20 meters in length, and weigh as much as 20 tons.
But in this article we are not interested in sensationalism and unsubstantiated allegations.So we move on to the real facts.What are the biggest plesiosaurs.

Pliosaurus macromerus
Pliosaurus macromerus was first described and named by John Phillips in 1871, as a species of Pleiosaurus, on the basis of a large femur, OUMNH J.12498, and a series of unassociated vertebrae. The specific name is derived from μακρός, makros, meaning "long" in Ancient Greek and mēros, meaning "thigh" in Latin, from Greek, in reference to the large size of OUMNH J.12498 (a thigh bone).These specimens were collected during the excavation of the Great Western Railway near Swindon, Wiltshire, probably from the Pectinatites hudlestoni and Pavlovia pallasioides ammonite zone, Upper Kimmeridge Clay, of the Swindon Clay and Cemetery Beds. Another very large pliosaur was Pliosaurus macromerus, known from a single 2.8 m long incomplete mandible. It may have reached 18 metres (59 ft), assuming the skull was about 17% of the total body length.

Pliosaurus kevani - Weymouth Bay Pliosaur
Dating back around 155 million years, the pliosaur skull was discovered on the nearby Jurassic Coast World Heritage Site, and is one of the largest and best preserved fossils of its kind ever found.
Belonging to a creature up to 18m in length, the skull is a staggering 2.4 m long and is believed to have possessed the biggest bite of all time – powerful enough to break a small car in half.
Pliosaurus kevani was named in honour of Kevan Sheehan, the Osmington Mills cafй owner who collected most of the skull, piece by piece, over a period of eight years during daily walks along the foreshore. Kevan collected chunks up to 60 kg in mass as they weathered out from the Jurassic aged Kimmeridge Clay Formation sea-cliff. The specimen was purchased with funding secured by Dorset County Council’s museum service from the Heritage Lottery Fund Collecting Cultures programme and Dorset and Devon county councils. It was prepared between 2010 and 2011 by Scott Moore-Fay and went on public display in Dorchester County Museum in July 2011.
Richard Forrest, who was involved with the project from the beginning, first had the idea of putting together a ‘dream team’ of British plesiosaur specialists to study and describe the skull. This is the first collaboration of its kind among plesiosaur researchers (as far as I know), and I feel lucky to have had the opportunity to contribute to it under the driving force of our lead author, Roger Benson.
The massive skull has a long snout, circular orbits, huge temporal openings for the jaw musculature, and a deep mandible. Large portions of the skull have been crushed flat during fossilisation, so one of my tasks was to reconstruct the skull to show how it might have appeared before it was flattened. After several versions and much input from Mark Evans, I’m pleased with how it turned out, and I think we have a pretty accurate reconstruction of Pliosaurus. On the basis of this reconstruction I’ve also had a go at restoring the life appearance of the head of P. kevani in profile. Despite its large size and massive teeth, the head is rather gracile.

Pliosaurus funkei - Predator X
Fossil remains of a pliosaur nicknamed as Predator X have been discovered and excavated from Norway in 2008. This pliosaur has been estimated at 15 metres (49 ft) in length and 45 metric tons (50 short tons) in weight.
Using Liopleurodon, another large pliosaurid, as a guide, the Svalbard specimen had been estimated to have been 15 metres (49 ft) long, 45,000 kilograms (99,000 lb) in weight and had teeth 30 centimetres (12 in) long.The jaws of the creature may have been able to exert more force than those of a Tyrannosaurus rex,with one news source stating the bite was over 10 times more powerful than any modern animal and four times more powerful than that of a Tyrannosaurus.It is estimated to have lived approximately 147 million years ago.[Analysis of bones from the four flippers suggest that the animal cruised using just two fore-flippers, using the back pair for extra speed when pursuing and capturing prey. P. funkei"s brain was of a similar type and size, proportionally, to that of today"s great white shark, the team says.Later on, thorough scrutiny of this Svalbard specimen revealed that it was not as massive as originally claimed; total length estimates have been revised to 10.0–12.8 metres (32.8–42.0 ft).

Predator X Officially Named Pliosaurus funkei
The holotype of P. funkei is represented by the anterior portions of the upper and lower jaws (including premaxillary and dentary teeth), one nearly complete cervical centrum and two partial cervical centra, three pectoral centra with neural arches, fifteen dorsal centra and eight neural arches, a complete right coracoid, numerous rib fragments and gastralia, and a complete right forelimb. The referred specimen is represented by five partial cervical centra, one partial dorsal centrum, and a partial skull including the occipital condyle, a complete left quadrate, a partial left squamosal and incomplete left surangular and articular. Several fragmentary and unidentified bones also pertain to PMO 214.136. Due to the Arctic climate found on Svalbard, the sediment in which the specimens were subjected to repeated freeze-thaw cycles prior to collection, resulting in extensive fracturing and degradation of the material.PMO 214.136 was discovered in 2007, following the collection of approximately 20,000 fragments that compose PMO 214.135 which were found moist in situ and degraded upon drying during the preparation process (individual fragments are catalogued at the University of Oslo Natural History Museum by specimen number followed by a slash and a number). Estimates of skull length are approximately 1.6–2.0 m (5.2–6.6 ft) for the holotype and 2.0–2.5 m (6.6–8.2 ft) for PMO 214.136, suggesting a total body length of 10–13 m (33–43 ft) for the species, making P. funkei one of the largest pliosaurs described so far.Due to its large size and relative completeness, the species, nicknamed "Predator X" prior to its formal description, gained extensive media coverage, which claimed that it was "most fearsome animal ever to swim in the oceans".Morphological and histological characters, such as the presence of a tuberosity on the humerus and a well developed anterior process on the coracoid, and abnormal hardening and increase in density of bone, indicate that both specimens were adult individuals. Even though none of the neural arches are fused to their centra in the vertebral column of both individuals (a possible juvenile trait), this feature is present in all large pliosaurids, and thus possibly paedomorphic within Pliosauridae.
Analysis of bones from the four flippers suggest that the animal cruised using only the fore-flippers, using the back flippers for extra speed when pursuing and capturing prey. Predator X"s brain was of a similar type and size, proportionally, to that of today"s.

The Monster of Aramberri
A preliminary report on an pliosaur from Mexico was made in June of 2002 and gained some media publicity in December 2002/January 2003. This specimen is estimated, possibly rather conservatively at 15 meters in length based on the diameter of a pectoral vertebra being rather larger than that of Kronosaurus. This specimen is substantially complete, and there is some expectation that it will be possible to prepare the post-cranial material as well as the skull.
The "monster of Aramberri" is the denomination that was given to the fossil remains of a huge marine reptile, a giant carnivore belonging to the Pliosauroidea clade that was found in Aramberri, Nuevo Leуn, Mexico by a student of the Facultad de Ciencias de la Tierra of the Universidad Autуnoma de Nuevo Leуn while conducting geological mapping in 1985.
It was originally estimated that the remains belonged to a young individual which was more or less 15 meters long. It was initially falsely identified as Liopleurodon ferox; this conclusion was used in BBC"s Walking with Dinosaurs, in which the individual was the base to depict a very big Liopleurodon. French and German paleontologists classified it as a giant pliosaur, which lived around 140 millions years ago in shallow waters of the area, in what is now Aramberri, Mexico.
The specimen is not properly named and described yet though the first assumptions of it being a juvenile individual have been outdated and that it is apparently not related to Liopleurodon ferox. It remains possibly one of the largest pliosaur known, and perhaps the largest.

Тагове:   Monster,   FORCE,   Predator,   Famous,   сова,   Prey,   Fossil,   blood,   Loss,   Gigantic,   skull,   prehistoric animals,   giant animals,   reptiles,   encyclopedia,   teeth,   extinct,   mainstream media,   pliosaurs,   carnivor,   jaws,   armor,   evolutia,   terrible,   habitat,   scavenger,


Няма коментари

За този блог
Автор: valentint
Категория: Политика
Прочетен: 922435
Постинги: 225
Коментари: 18
Гласове: 16
«  Юли, 2020