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Sarcosuchus imperator
Topic Started: Jan 8 2012, 01:51 PM (11,067 Views)
Taipan
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Sarcosuchus imperator

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Fossil range: Early Cretaceous, 112 Ma

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Subclass: Diapsida
Infraclass: Archosauromorpha
(unranked): Mesoeucrocodylia
Family: Pholidosauridae
Genus: Sarcosuchus
Species: Sarcosuchus imperator

Sarcosuchus (pronounced /ˌsɑrkɵˈsuːkəs/, meaning 'flesh crocodile' and commonly called "SuperCroc") is an extinct genus of crocodyliform and distant relative of the crocodile that lived 112 Million years ago. It dates from the early Cretaceous Period of what is now Africa and is one of the largest giant crocodile-like reptiles that ever lived. It was almost twice as long as the modern saltwater crocodile and weighed approximately 8 to 10 tonnes.

Until recently, all that was known of the genus was a few fossilised teeth and armour scutes, which were discovered in the Sahara Desert by the French paleontologist Albert-Félix de Lapparent, in the 1940s or 1950s. He called it the "Aoulef crocodile". However, in 1997 and 2000, Paul Sereno discovered half a dozen new specimens, including one with about half the skeleton intact and most of the spine. All of the other giant crocodiles are known only from a few partial skulls, so which is actually the biggest is an open question.

Description
When fully mature, Sarcosuchus is believed to have been as long as a city bus (11.2–12.2 meters or 37–40 ft) and weighed up to 8 tonnes (8.75 tons). The largest living crocodilian, the saltwater crocodile, is less than two-thirds of that length (6.3 meters or 20.6 ft is the longest confirmed individual) and a small fraction of the weight (1,200 kg, or 1.3 tons).

The very largest Sarcosuchus is believed to have been the oldest. Osteoderm growth rings taken from an 80% grown individual (based on comparison to largest individual found) suggest that Sarcosuchus kept growing throughout its entire 50–60 year average life span (Sereno et al., 2001). Modern crocodiles grow at a rapid rate, reaching their adult size in about a decade, then growing more slowly afterwards.

Its skull alone was as big as a human adult (1.78 m, or 5 ft 10 inches). The upper jaw overlapped the lower jaw, creating an overbite. The jaws were relatively narrow (especially in juveniles). The snout comprises about 75% of the skull's length (Sereno et al., 2001).

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The huge jaw contained 132 thick teeth (Larsson said they were like "railroad spikes"). The teeth were conical, adapted for grabbing and holding; instead of narrow, adapted for slashing (like the teeth of some land-dwelling carnivores), and more like that of true crocodilians. Sarcosuchus could probably exert a force of 80 kN (18,000 lbf) with its jaw, making it very unlikely that prey could escape.

It had a row of bony plates or osteoderms, running down its back, the largest of which were 1 m (3 ft) long. The scutes served as armour and may have helped support its great mass, but also restricted its flexibility.

Sarcosuchus also had a strange depression at the end of its snout. Called a bulla, it has been compared to the ghara seen in gharials. Unlike the ghara, though, the bulla is present in all Sarcosuchus skulls that have been found so far. This suggests it was not a sexually selected character (only the male gharial has a ghara). The purpose of this structure remains enigmatic. Sereno and others asked various reptile researchers what their thoughts on this bulla were. Opinions ranged from it being an olfactory enhancer to being connected to a vocalization device (Geology News, 2001).

Behaviour and diet
The eye sockets of Sarcosuchus rotated upwards and were somewhat telescoped (Sereno et al., 2001). This suggests that the animal probably spent most of its time with the majority of its body submerged, watching the shore for prey.

It seems likely that it ate the large fish and turtles of the Cretaceous. As the overhanging jaw and stout teeth are designed for grabbing and crushing, its primary prey may have been large animals and smaller dinosaurs, which it ambushed, dragged into the water, crushed, drowned and then tore apart.

It may have come into conflict with Suchomimus, an 11 m (36 ft) theropod dinosaur with a gharial-like snout, whose fossils were found in the same geological formation as Sarcosuchus. According to Sereno[citation needed], "because the ancient animal was so large, it could easily handle huge dinosaurs, including the massive long-necked, small-headed sauropods that were common in that African region".

Other crocodilian biologists are skeptical of the animal's "giant killing" capabilities. The long, thin snout of Sarcosuchus was very similar to the thin snouts of the modern gharial, the false gharial and the slender-snouted crocodile, all of which are nearly exclusive fish-eaters and incapable of tackling large prey. This can be contrasted to both the modern Nile crocodile and the extinct Deinosuchus, both of which exhibit very broad, heavy skulls, suitable for dealing with large prey. This, coupled with the abundance of large, lobe-finned fish in its environment, leads many to suggest that, far from being a dinosaur killer, Sarcosuchus was simply a large piscivore, a scaled-up version of the modern gharial.

However, while the snout of juvenile Sarcosuchus strongly resembled modern narrow-snouted crocodiles in width, it expands dramatically in mature individuals (Sereno et al., 2001). While still comparatively narrower than the snout of a Nile crocodile, the snout is still much wider than the snouts of crocodilians like the gharial. In addition, the teeth do not interlock, like those of mostly piscivorous crocodilians. This suggests that, like the Nile crocodile, it may have complemented a primarily fish diet with terrestrial animals, at least upon maturity.

It is pertinent to note, though, that the lobe-finned fish that shared the waters with Sarcosuchus were often in excess of 1.8 m (6 ft) long and 90 kg (200 lb) in weight. This raises the possibility of those adaptations, which seem to indicate large or moderate-sized terrestrial prey, may instead have been adaptations for dealing with exceptionally large fish (many species of which possessed a layer of osteoderms, for protection).

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Environment
110 million years ago, in the Early Cretaceous, the Sahara was still a great tropical plain, dotted with lakes and crossed by rivers and streams that were lined with vegetation. Based on the number of fossils discovered, the aquatic Sarcosuchus was probably plentiful in these warm, shallow, freshwater habitats.

Unlike modern true crocodiles, which are very similar in size and shape to one another and tend to live in different areas; Sarcosuchus was just one of many Crocodyliformes, of different sizes and shapes, all living in the same area. Four other species of extinct Crocodyliformes were also discovered in the same rock formation along with the Sarcosuchus, including a dwarf crocodile with a tiny, 8 cm (3 in) long skull. They filled a diverse variety of ecological niches, instead of competing with each other for resources.

Scientific study
The Sarcosuchus remains are from several individuals and include a spine (vertebrae), limb bones, hip bones (a pelvic girdle), the bony armored plates that ran down its back (scutes) and more than a half-dozen skulls. Many crocodyliform skulls are thick and heavy[citation needed]. They tend to be found more frequently than the rest of the body. This is quite a contrast with dinosaurs, whose relatively fragile skulls rarely become part of the fossil record.
The osteoderms of ancient reptiles have been used to determine age (Erickson & Brochu, 1999). Since they retain growth rings, like those found in trees (most other bones 'suffer' remodeling with age, which destroys former growth rings), it is theoretically possible to count the age of the individual that the bones belonged to. One 80% grown specimen was discovered with 40 rings, indicating that it had lived for 40 years. This form of growth rate calculation has been somewhat controversial. Others (Schwimmer, 2002) have criticised this form of growth measurement, as annular rings are harder to determine in a creature that lives in an environment that is without extreme seasonality (such as the Mesozoic).

No skeleton was complete enough to measure directly, so the maximum length estimate was calculated by measuring the largest skull and comparing it to modern crocodiles. In modern crocodiles, the skull and body are the same proportion regardless of age or sex (Sereno et al., 2001). The primary difference is that species with a long snout have larger heads in proportion to their bodies than species with relatively broad snouts. The length of Sarcosuchus was the average of the expected length of the narrow-snouted gharial and the intermediate-snouted saltwater crocodile, while the mass was the expected mass of the latter. Sereno also measured living crocodilians in India and Costa Rica and used that data in his analysis.

As part of a National Geographic Special, Greg Erickson of Florida State University, Kent Vliet of the University of Florida and Kristopher Lapping of Northern Arizona University provoked American alligators, at the St. Augustine Alligator Farm and Zoological Park in Florida, into biting a bar studded with piezoelectric sensors. The largest alligator they tested] was able to exert a force of 9.45 kN (2,125 lbf). By comparing the force exerted by more than 60 animals, they were able to determine that the force exerted was proportional to the size of the animal, which allowed an estimate of the biting power of the Sarcosuchus. This force was calculated to be 80 kN (18,000 lbf).

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The giant croc phenomenon
"With today's crocs, you basically have a period of fast growth, then a little bit of growth — this guy wasn't slowing down."
—Paul C. Sereno
Giant crocodiles seem to be a good example of convergence because, according to Schwimmer, "the idea of really big crocs is a repeat theme in evolution". This may in part be due to body design (the armoured plates of the back can provide structural support to a massive body) and in part due to environment (water can buoy up their massive bodies).

A study of another giant crocodilian, Deinosuchus, indicated that it grew at about the same rate as modern crocodiles, up to 0.5 m (1.5 ft) per year. It was larger because it kept growing, reaching full adulthood in 35 years, instead of 10. While there is a genetic component, growing that large also requires a rich diet. All the different giant crocodiles must have lived in near-perfect environments, with vast areas of warm, shallow water and abundant prey.

Deinosuchus, which was from the Late Cretaceous of what is now North America, is also a good example of a giant crocodile that is only distantly related to Sarcosuchus. Deinosuchus, which is only known from skulls, had a smaller skull than Sarcosuchus[citation needed], but a broad snout, like an alligator. This means that the skull of the Deinosuchus is probably a smaller portion of its total body length than the skull of the long-snouted Sarcosuchus, so its total size may be as large, or even larger. Other rivals in size of Sarcosuchus are Purussaurus from the Miocene of what is now Peru and Brazil, and Rhamphosuchus from the Miocene and Pliocene of what is now India. However, their fossils are less complete.

Sarcosuchus is not an ancestor of modern crocodiles. Also, it is not a crocodilian in the phylogenetic definition of the term. A crocodilian is any member of the clade Crocodilia. Crocodilia includes all modern forms (such as crocodiles proper, alligators etc) and their immediate prehistoric relatives. Sarcosuchus is a member of the family Pholidosauridae, more distantly related to today's crocodilians.

"Crocodile" is a term commonly used in a much broader sense. The first 'crocodile-like reptiles' (the Crocodylomorpha), which split from the bird-line of archosaurs (the group of reptiles that include dinosaurs, pterosaurs and birds) about 230 million years ago (in the Late Triassic), looked somewhat like modern crocodilians. They had long legs, long bodies covered with armour.

Until the 1980s, the pholidosaurids were classified as part of the presumed suborder "Mesosuchia", within the order Crocodylia. However, Benton and Clark determined in 1988 that Mesosuchia was a paraphyletic group, containing the ancestor of all modern crocodiles.

Teeth and osteoderms found in Brazil belong to a close relative of Sarcosuchus. This is possibly evidence that land bridges between Africa and South America existed much later than was previously believed.

On the other hand, based on the structure of the snout, the closest relative of Sarcosuchus is the pholidosauridTerminonaris, with Dyrosaurus and Pholidosaurus as slightly more distant relatives. As a group, they are narrow-snouted fish-eaters from saltwater environments, except for the broader snouted, river-dwelling Sarcosuchus.

Desert discoveries
The fossils were discovered in Gadoufaoua, Niger in the Ténéré Desert, which is part of the Sahara. The first Sarcosuchus teeth and scutes were recovered by the French paleontologist Albert-Félix de Lapparent, in the 1940s or 1950s. It was 1964, however, before a skull was discovered by geologists and brought to the attention of paleontologist Philippe Taquet. He shipped it to Paris, where it was examined by France de Broin. Together, they formally named and described the species, in 1966, before returning the specimen to Niger.

In 1966, de Lapparent's niece France de Broin and Taquet named the creature Sarcosuchus imperator, which is dervived from sarco (meaning 'flesh'), suchus (meaning 'crocodile') and imperator (Latin, meaning 'emperor'), i.e., the flesh crocodile emperor. The holotype specimen is MNN 604.

The next major expedition was Paul C. Sereno's trip, in 1997 and the follow-up trip in 2000. He recovered partial skeletons, numerous skulls and 20 tons of assorted other fossils from the deposits of the Elrhaz Formation, which has been dated as late Aptian or early Albian stages of the late Cretaceous. It took about a year to prepare the Sarcosuchus remains. The discovery was then published on October 25, 2001, in the scientific journal Science by Paul C. Sereno of the University of Chicago and National Geographic's Explorer-in-Residence, Hans C. E. Larsson from Yale University and the University of Toronto (formerly a student at the University of Chicago), Christian Sidor of the New York College of Osteopathic Medicine in Old Westbury, New York and Boubé Gado of the Institut de Recherches en Sciences Humaines in Niamey, Niger.

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Edited by Taipan, Jun 29 2013, 11:21 PM.
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Troubled life of the Nigersaurus

February 19, 2002 Posted: 10:45 AM EST (1545 GMT)


BOSTON, Massachusetts -- The uneasy life of a 1,000-toothed dinosaur "lawnmower" -- and how it fell prey to giant crocodiles -- has been unveiled to scientists.

Nigersaurus had so many teeth it has been dubbed "the mesozoic lawnmower," but while it may may have looked like "a hammerhead shark with legs," even it had a match.

Dinosaur hunter Paul Sereno revealed to the American Association for the Advancement of Sciences annual meeting in Boston that the 14 metre (45ft) giant was big -- but easy prey to others.

In particular, how Nigersaurus proved no match for a 12 metre (40ft) long crocodile called Sarcosuchus, or supercroc.

Nigersaurus -- so named because it was discovered in Niger -- had the long neck of a Diplodocus and up to 1,000 teeth in its intricate jaws, Sereno, of the University of Chicago, said on Monday.

The bones of the 1,000-toothed "lawnmower" which scythed across west Africa were found first by a French researcher.

More remains were found in the same strata as those of the giant crocodile.

"I would not doubt for a minute that those two encountered each other, not favourably for the Nigersaurus," Sereno said.

"The crocodile would have been something to watch out for along the banks of the river. It may have been a fish eater when it was young, but when it grew up to 40ft long anything along the banks would have been fair game.

"Nigersaurus, a lightly built, delicate, wondrous plant eater, would have been easy prey."

Sereno has made several major dinosaur discoveries
Sereno is credited with discovering the supercroc and his other discoveries in Africa alone have included a giant predator, Carcharodontosaurus, a rival to T rex; a swiftcarnivore, Deltadromeus; and an 18 metre (60ft) long plant eater, Jobaria.

He and colleagues had been piecing together the life of Nigersaurus.

Although it is known it roamed a meandering African river valley 100m years ago, its way of life is still a puzzle.

Nigersaurus may have grown to 14 metres and three metres (10ft) high at the hip.

"We are missing only a few bones of the skull, feet and the tip of the tail," he told the meeting.

"The teeth were narrow, needle shaped, not bigger than just a few millimetres in width and packed into an open groove in the jaw.

"There were stacks of eight or 10 teeth in line, erupting from a single point in the jaw: a huge number of small teeth, enamel covered, giving it more bite, because each small tooth has its own wrapping of enamel, and a lot more cutting surface.

"It looks like a hammerhead shark on legs. I have never seen anything like it.

"It is going to be a shocker when we eventually get this thing together. It has jaws that extend to each side of the skull. It is definitely designed to crop plants. When you look at it, you say: this is the mesozoic lawnmower."

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http://archives.cnn.com/2002/TECH/science/02/19/dinosaur.croc/index.html?related
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http://palaeontology.palass-pubs.org/pdf/Vol%2020/Pages%20203-208.pdf

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Spinning Slayers: Giant Crocs Used 'Death Rolls' to Kill Dinosaurs

By Charles Q. Choi, Live Science Contributor | May 04, 2014 10:48am ET

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New research suggests Deinosuchus, a crocodilian from North America that could reach a length of 39.3 feet (12 m) and weighed more than 18,740 lbs. (8,500 kg), could take down dinosaurs with so-called death rolls.

Ancient giant crocodilians killed dinosaur prey by spinning their bodies in "death rolls," tearing off the beasts' flesh and limbs, researchers say.

These new findings shed light on the way ancient reptiles interacted with their environments, scientists added.

Crocodilians include the largest of all reptiles alive today, the saltwater crocodile, a deadly carnivore that can grow at least 23 feet (7 meters) long and weigh more than 2,200 lbs. (1,000 kilograms). These predators will eat just about anything they can, including sharks. (Although these reptiles do kill people, far more people die of bee stings each year than crocodile attacks.)

As massive as saltwater crocodiles are, their ancient relatives could get even larger. Sarcosuchus from Africa and South America could reach about 37.7 feet (11.5 m) long and weigh a whopping 17,635 lbs. (8,000 kg); Deinosuchus from North America could reach a length of 39.3 feet (12 m) and weigh more than 18,740 lbs. (8,500 kg); and Purussaurus from the Amazon basin could reach more than 42.6 feet (13 m) long and at least 22,000 lbs. (10,000 kg).

Bite marks found on fossils suggest that Deinosuchus preyed on dinosaurs such as hadrosaurs, which were large duck-billed dinosaurs, and medium-size bipedal dinosaurs known as theropods, a group that includes Tyrannosaurus rex and the ancestors of birds. Scientists have suggested that Sarcosuchus might also have fed on large dinosaurs, while Purussaurus hunted large mammals such as giant rodents, as well as turtles and fish.

Researchers suggested that like modern crocodilians, these ancient reptiles might have used death rolls to finish off their prey. This lethal move involves reptiles holding their prey tight with their mighty jaws and spinning their entire bodies to rip off flesh or tear off limbs.

However, the death roll can generate substantial forces in the skull. To see if ancient crocs had skulls that were strong enough to withstand these stresses, investigators modeled the skulls of 16 living crocodilian species and three extinct crocodilian groups.

The researchers suggest that Deinosuchus and Purussaurus could execute death rolls on, respectively, dinosaurs and large mammals. However, narrow-snouted Sarcosuchus probably could not, as the forces to its skull may have been too great.

The scientists found that death rolls were easier for smaller predators, because they were lighter, making it easier for them to spin. This means it was probably easier for juveniles than adults, said lead study author Ernesto Blanco, a paleobiomechanicist at the Institute of Physics in Montevideo, Uruguay.

"It is possible that very large specimens use other approaches for taking chunks of meat from large vertebrates," Blanco said -- for example, with sideways movements of the head. They may have also simply swallowed small prey whole.

The researchers did note their model had several uncertainties, as "we are studying much larger crocs than any living species," Blanco told Live Science. This means "we cannot completely exclude 'death roll' in Sarcosuchus."

The scientists detailed their findings online April 16 in the journal Historical Biology.

http://www.livescience.com/45342-crocs-killed-dinosaurs-with-death-rolls.html




The ‘death roll’ of giant fossil crocodyliforms (Crocodylomorpha: Neosuchia): allometric and skull strength analysis

DOI:10.1080/08912963.2014.893300
Rudemar Ernesto Blancoac, Washington W. Jonesbc & Joaquín Villamilbc*
Received: 14 Oct 2013
Accepted: 7 Feb 2014
Published online: 16 Apr 2014

Abstract
In the evolution of crocodylomorphs, there were at least three giant-dimension genera: Deinosuchus from late Cretaceous of North America, Sarcosuchus from middle Cretaceous of Africa and South America, and Purussaurus from Miocene of South America. It has been suggested that these predators could have fed on very large prey as dinosaurs and megamammals. The ‘death roll’ is a spinning manoeuver executed to subdue and dismember large prey; therefore, it has been previously suggested that giant cocrodylomorphs may have used this manoeuver. However, this manoeuver can generate torsional stresses in the skull. We propose a biomechanical model to estimate the capability of a crocodylomorphs for withstanding this torsional stresses. Our results show a good correlation between a ‘death roll’ capability indicator and the feeding categories related with the actual use of ‘death roll’ in 16 living species. Here, for the first time, we propose a biomechanical approach of the implications of ‘death roll’ in fossil crocodylomorphs. We suggest that Deinosuchus and Purussaurus were able to execute death roll over dinosaurs and large mammals, respectively, but Sarcosuchus probably was not. We also found some allometry effects and, finally, we discuss palaeobiological implications based on our results.

http://www.tandfonline.com/doi/abs/10.1080/08912963.2014.893300#.U2dHzq2SzVs
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Other crocodilian biologists are skeptical of the animal's "giant killing" capabilities. The long, thin snout of Sarcosuchus was very similar to the thin snouts of the modern gharial, the false gharial and the slender-snouted crocodile, all of which are nearly exclusive fish-eaters and incapable of tackling large prey. This can be contrasted to both the modern Nile crocodile and the extinct Deinosuchus, both of which exhibit very broad, heavy skulls, suitable for dealing with large prey. This, coupled with the abundance of large, lobe-finned fish in its environment, leads many to suggest that, far from being a dinosaur killer, Sarcosuchus was simply a large piscivore, a scaled-up version of the modern gharial.

However, while the snout of juvenile Sarcosuchus strongly resembled modern narrow-snouted crocodiles in width, it expands dramatically in mature individuals (Sereno et al., 2001). While still comparatively narrower than the snout of a Nile crocodile, the snout is still much wider than the snouts of crocodilians like the gharial. In addition, the teeth do not interlock, like those of mostly piscivorous crocodilians. This suggests that, like the Nile crocodile, it may have complemented a primarily fish diet with terrestrial animals, at least upon maturity.


I would really like this misconception that Sarcosuchus had gharial snout to stop being brought back in any disqussion about Sarcosuchus. Sarcosuchus wasn't an ancestor of gharials like how usually said. And the wide base of the jaws indicates that it had large jaw muscles.

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