Потребителски вход

Запомни ме | Регистрация
15.01.2016 22:55 - Largest prehistoric animals Vol.1 Vertebrates part9 Repstiles ch.3 Crocodylomorpha - Caimans and Alligators
Автор: valentint Категория: Забавление   
Прочетен: 584 Коментари: 0 Гласове:

Последна промяна: 05.12.2016 19:34

Purussaurus estimated at 11–13 metres (36–43 ft) in length.

Purussaurus is an extinct genus of giant caiman that lived in South America during the Miocene epoch, 8 million years ago. It is known from skull material found in the Brazilian, Colombian and Peruvian Amazonia, and northern Venezuela.
The estimated skull length for one large individual of the type species P. brasiliensis is 1,400 millimetres (55 in). Paleontologists estimate that P. brasiliensis reached around 12.5 metres (41 ft) in length, weighing around 8.4 metric tons, with a mean daily food intake of 40.6 kg. Bite force has been estimated to be around 69,000 N (around 7 metric tons-force).The large size and estimated strength of this animal appears to have allowed it to include a wide range of prey in its diet, making it an apex predator in its ecosystem. As an adult, it would have preyed upon large to very large vertebrates with no real competition from sympatric, smaller, carnivores. Researchers have proposed that the large size of Purussaurus, though offering many advantages, may also have led to its vulnerability. The constantly changing environment on a large geological scale may have reduced its long-term survival, favoring smaller species more resilient to ecological shifts.
Purussaurus is one of the largest known crocodyliformes ever to have existed. Three other extinct crocodyliformes, Sarcosuchus, Deinosuchus, and Rhamphosuchus had similar body sizes. Sarcosuchus and Deinosuchus had similar proportions, but both were geologically much older, dating from the Early and Late Cretaceous, respectively. Rhamphosuchus lived around the same time as Purussaurus, but was slightly smaller, had a more gharial-like snout and lived in India. During the summer of 2005, a Franco-Peruvian expedition (the Fitzcarrald expedition) found new fossils of Purussaurus in the Peruvian Amazon (600 km from Lima).
Analysis of a biomechanical model of the skull of Purussaurus indicated that it was capable of performing the "death roll" maneuver used by extant crocodilians to subdue and dismember their prey.
Brazilian P. brasiliensis is associated with sharks, rays, freshwater teleosts, lungfish, turtles including Stupendemys, crocodilians including Charactosuchus, Gryposuchus, and Mourasuchus, Anhinga birds, and mammals including sloths, bats, rodents, the primate Stirtonia, and river dolphins. River, floodplain, and lake environments were present.Marine and freshwater fish, turtles, crocodilians, and terrestrial and aquatic mammals are associated with Venezuelan P. mirandai. Its environment is described as tropical and coastal. The earlier Colombian P. neivensis lived alongside a massive variety of fauna, including astrapotheres like Granastrapotherium and Xenastrapotherium, the early species of Mourasuchus and Gryposuchus, and the terrestrial crocodyliform Langstonia. This fauna dates from 13 million years ago, in the Laventan stage of the Late Miocene.

Some close contenders in size are Deinosuchus estimated at around 12 metres (39 ft)

Deinosuchus  is an extinct genus related to the alligator that lived 80 to 73 million years ago (Ma), during the late Cretaceous period. The name translates as "terrible crocodile" and is derived from the Greek deinos  "terrible", and soukhos 
"crocodile". The first remains were discovered in North Carolina (United States) in the 1850s; the genus was named and described in 1909. Additional fragments were discovered in the 1940s and were later incorporated into an influential, though inaccurate, skull reconstruction at the American Museum of Natural History. Knowledge of Deinosuchus remains incomplete, but better cranial material found in recent years has expanded scientific understanding of this massive predator.
Although Deinosuchus was far larger than any modern crocodile or alligator, with the largest adults measuring 10.6 m (35 ft) in total length, its overall appearance was fairly similar to its smaller relatives. It had large, robust teeth built for crushing, and its back was covered with thick hemispherical osteoderms. One study indicated Deinosuchus may have lived for up to 50 years, growing at a rate similar to that of modern crocodilians, but maintaining this growth over a much longer time.
Deinosuchus fossils have been found in 10 US states, including Texas, Montana, and many along the East Coast. Fossils have also been found in northern Mexico. It lived on both sides of the Western Interior Seaway, and was an opportunistic apex predator in the coastal regions of eastern North America. Deinosuchus reached its largest size in its western habitat, but the eastern populations were far more abundant. Opinion remains divided as to whether these two populations represent separate species. Deinosuchus was probably capable of killing and eating large dinosaurs. It may have also fed upon sea turtles, fish, and other aquatic and terrestrial prey.
Despite its large size, the overall appearance of Deinosuchus
was not considerably different from that of modern crocodilians Deinosuchus had an alligator-like, broad snout, with a slightly bulbous tip.Each premaxilla contained four teeth, with the pair nearest to the tip of the snout being significantly smaller than the other two.Each maxilla (the main tooth-bearing bone in the upper jaw) contained 21 or 22 teeth.The tooth count for each dentary (tooth-bearing bone in the lower jaw) was at least 22.All the teeth were very thick and robust; those close to the rear of the jaws were short, rounded, and blunt.They appear to have been adapted for crushing, rather than piercing.When the mouth was closed, only the fourth tooth of the lower jaw would have been visible.

Modern saltwater crocodiles (Crocodylus porosus) have the strongest recorded bite of any living animal, with a maximum force of 16,414 N (3,690 lbf).The bite force of Deinosuchus has been estimated to be 18,000 N (4,000 lbf). to 102,803 N (23,111 lbf).It has been argued that even the largest and strongest theropod dinosaurs, such as Tyrannosaurus, probably had bite forces inferior to that of Deinosuchus.
Deinosuchus had a secondary bony palate, which would have permitted it to breathe through its nostrils while the rest of the head remained submerged underwater.The vertebrae were articulated in a procoelous manner, meaning they had a concave hollow on the front end and a convex bulge on the rear; these would have fit together to produce a ball and socket joint.The secondary palate and procoelous vertebrae are advanced features also found in modern eusuchian crocodilians.
The osteoderms (scutes) covering the back of Deinosuchus were unusually large, heavy, and deeply pitted; some were of a roughly hemispherical shape.Deep pits and grooves on these osteoderms served as attachment points for connective tissue.Together, the osteoderms and connective tissue would have served as load-bearing reinforcement to support the massive body of Deinosuchus out of water.These deeply pitted osteoderms have been used to suggest that, despite its bulk, Deinosuchus could probably have walked on land much like modern-day crocodiles.
The large size of Deinosuchus has generally been recognized despite the fragmentary nature of the fossils assigned to it. However, estimates of how large it really was have varied considerably over the years. The original estimates from the 1950s for the type specimen of the then-named "Phobosuchus riograndensis" were based on a skull 1.5 m (5 ft) long, reconstructed with similar proportions to the Cuban crocodile giving a total estimated length of 15 m (50 ft).However, this reconstruction is currently considered to be inaccurate.Using more complete remains, it was estimated in 1999 that the size attained by specimens of Deinosuchus varied from 8 to 10 m (26 to 33 ft) with weights from 2.5 to 5 t (3 to 6 short tons). This was later corroborated when it was noted that most known specimens of D. rugosus usually had skulls of about 1 m (3.3 ft) with estimated total lengths of 8 m (26 ft) and weights of 2.3 t (3 short tons). However, the largest fragmentary remains of D. riograndensis were 1.5 times the size of those of the average D. rugosus and it was determined that the largest individuals of this species may have been up to 12 m (39 ft) in length and perhaps weighed as much as 8.5 t (9.4 short tons).
A particularly large mandibular fragment from a D. riograndensis specimen was estimated to have come from an individual with a skull length of approximately 1.48 m (4.9 ft). This length was used in conjunction with a regression equation relating skull length to total length in the American alligator to estimate a total length of 10.6 metres (35 ft) for this particularly specimen.This is only slightly lower than previous estimates for the species. Deinosuchus has often been described as the largest crocodyliform of all time. However other crocodyliformes such as Purussaurus, Rhamphosuchus, and Sarcosuchus may have equaled or exceeded it in size.
Deinosuchus was present on both sides of the Western Interior Seaway.Specimens have been found in 10 of the modern-day United States.A Deinosuchus osteoderm from the San Carlos Formation was also reported in 2006, so the giant crocodilian's range may have included parts of northern Mexico.Deinosuchus fossils are most abundant in the Gulf Coastal Plain region of Georgia, near the Alabama border. All known specimens of Deinosuchus were found in rocks dated to the Campanian stage of the Late Cretaceous period. The oldest examples of this genus lived approximately 80 Ma, and the youngest lived around 73 Ma.
The distribution of Deinosuchus specimens indicates these giant crocodilians may have preferred estuarine environments. In the Aguja Formation of Texas, where some of the largest specimens of Deinosuchus have been found, these massive predators probably inhabited brackish-water bays. Although some specimens have also been found in marine deposits, it is not clear whether Deinosuchus ventured out into the ocean (like modern-day saltwater crocodiles); these remains might have been displaced after the animals died.Deinosuchus has been described as a "conspicuous" component of a purportedly distinct biome occupying the southern half of Late Cretaceous North America.
In 1954, Edwin H. Colbert and Roland T. Bird speculated that Deinosuchus "may very well have hunted and devoured some of the dinosaurs with which it was contemporaneous".Colbert restated this hypothesis more confidently in 1961: "Certainly this crocodile must have been a predator of dinosaurs; otherwise why would it have been so overwhelmingly gigantic? It hunted in the water where the giant theropods could not go."David R. Schwimmer proposed in 2002 that several hadrosaurid tail vertebrae found near Big Bend National Park show evidence of Deinosuchus tooth marks, strengthening the hypothesis that Deinosuchus fed on dinosaurs in at least some instances.In 2003, Christopher A. Brochu agreed that Deinosuchus "probably dined on ornithopods from time to time." Deinosuchus is generally thought to have employed hunting tactics similar to those of modern crocodilians, ambushing dinosaurs and other terrestrial animals at the water's edge and then submerging them until they drowned. A 2014 study suggested that it would have been able to perform a "death roll", like modern crocodiles.
Schwimmer and G. Dent Williams proposed in 1996 that Deinosuchus may have preyed on marine turtles Deinosuchus would probably have used the robust, flat teeth near the back of its jaws to crush the turtle shells.The "side-necked" sea turtle Bothremys was especially common in the eastern habitat of Deinosuchus, and several of its shells have been found with bite marks that were most likely inflicted by the giant crocodilian.
Schwimmer concluded in 2002 that the feeding patterns of Deinosuchus most likely varied by geographic location; the smaller Deinosuchus specimens of eastern North America would have been opportunistic feeders in an ecological niche similar to that of the modern American alligator. They would have consumed marine turtles, large fish, and smaller dinosaurs.The bigger, but less common, Deinosuchus that lived in Texas and Montana might have been more specialized hunters, capturing and eating large dinosaurs.Schwimmer noted no theropod dinosaurs in Deinosuchus's eastern range approached its size, indicating the massive crocodilian could have been the region's apex predator.
A 1999 study by Gregory M. Erickson and Christopher A. Brochu suggested the growth rate of Deinosuchus was comparable to that of modern crocodilians, but was maintained over a far longer time.Their estimates, based on growth rings in the dorsal osteoderms of various specimens, indicated each Deinosuchus might have taken over 35 years to reach full adult size, and the oldest individuals may have lived for more than 50 years.This was a completely different growth strategy than that of large dinosaurs, which reached adult size much more quickly and had shorter lifespans. According to Erickson, a full-grown Deinosuchus "must have seen several generations of dinosaurs come and go".
Schwimmer noted in 2002 that Erickson and Brochu's assumptions about growth rates are only valid if the osteodermal rings reflect annual periods, as they do in modern crocodilians.According to Schwimmer, the growth ring patterns observed could have been affected by a variety of factors, including "migrations of their prey, wet-dry seasonal climate variations, or oceanic circulation and nutrient cycles". If the ring cycle were biannual rather than annual, this might indicate Deinosuchus grew faster than modern crocodilians, and had a similar maximum lifespan.
Numerous additional specimens of Deinosuchus were discovered over the next several decades. Most were quite fragmentary, but they expanded knowledge of the giant predator's geographic range. As noted by Chris Brochu, the osteoderms are distinctive enough that even "bone granola" can adequately confirm the presence of Deinosuchus.Better cranial material was also found; by 2002, David R. Schwimmer was able to create a composite computer reconstruction of 90% of the skull.


Mourasuchus is an extinct genus of giant crocodilian from the Miocene of South America. The skull has been described as duck like, being broad, flat and very elongate, closely resembling what is seen in Stomatosuchus, an unrelated crocodilian that may also have had a large gular sac similar to those of pelicans or baleen whales. Mourasuchus had rows of small, conical teeth numbering around 40 on each side of the upper and lower jaws. Mourasuchus presumably obtained its food by filter feeding; the jaws were too gracile for the animal to have captured larger prey. It also probed the bottoms of lakes and rivers for food. Fossils have been found in the Fitzcarrald Arch of Peru, where it coexisted with many other crocodilians, including the giant gharial, Gryposuchus, and the alligatorid  Purussaurus, both of which were 12 m. The great diversity of crocodylomorphs in this Miocene-age (Tortonian stage, 8 million years ago) wetland suggests that niche partitioning was efficient, which would have limited interspecific competition


Even though it was ten meters long, it is not its size that makes Stomatosuchus stand out but its presumed feeding strategy. The upper jaw only had small conical teeth, while the lower jaw has been suggested at being toothless, with the inclusion of a pelican like pouch underneath. This is unprecedented amongst other known crocodiles and is why this ancient crocodile was given the full name of Stomatosuchus inermis which means 'weaponless mouth crocodile'.
What Stomatosuchus ate remains unknown for certain but one theory is that it ate fish. Stomatosuchus could either gulp water, or wait for a fish to pass by and then suck in water with its throat muscles drawing the fish inside. It could then close the upper jaw and constrict its pouch to squeeze the water out while the upper teeth prevented the fish from escaping. Re-studying the skull with modern techniques may have shed some more light upon how Stomatosuchus lived, but unfortunately the only known specimen of Stomatosuchus was destroyed along with the rest of the Munich Museum by an allied bombing raid in 1944.
Stomatosuchus is just one of many North African crocodiles that developed very special adaptations as also evidenced by the discoveries of Laganosuchus and Kaprosuchus, better known as the 'Boar croc'.




Тагове:   сова,   prehistoric animals,   giant animals,   reptiles,


Няма коментари

За този блог
Автор: valentint
Категория: Политика
Прочетен: 75337
Постинги: 146
Коментари: 24
Гласове: 11
«  Април, 2017