purussaurus

''Purussaurus'' is an extinct genus of giant caiman that lived in South America during the Miocene epoch, from the Friasian to the Huayquerian in the SALMA classification. It is known from skull material found in the Brazilian and Peruvian Amazon, Colombian Villavieja Formation, Panamanian Culebra Formation and the Urumaco and Socorro Formations of northern Venezuela.

Description

The skull length of the largest known individual of the type species, ''P. brasiliensis'' is .
It has been estimated that ''P. brasiliensis'' reached about in length, weighing about . Another estimate gave a larger size of in length, ranging from , and in weight, ranging from , with a mean daily food intake of . It is also likely that ''Purussaurus'' reached only long and . A 2022 study estimated a length of and a mass of using a phylogenetic approach; and a length of and mass of using a non-phylogenetic approach. As only skulls have been found, the actual length is not certain. Bite force has been estimated to be around 52,500 N (around 5.3 metric tons-force), with upper estimates indicating that Purussaurus was capable of generating 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 such as the xenarthrans and notoungulates present, 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. In other words, it was over-specialised and couldn't survive when its habitat changed, unlike smaller related species of caiman.

The skeletal anatomy of P. mirandai shows some adaptations for more upright limb orientation or weight support. Unlike all other members of the crown Crocodylia, which have two sacrals, P. mirandai have three.Giant extinct caiman breaks constraint on the axial skeleton of extant crocodylians
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The teeth vary between the three species of ''Purussaurus'', but are always around 50 mm (2 in) long and curve slightly backwards. They have small ridges along two of the edges which resemble those in ziphodonts. This indicates that ''Purussaurus'' hunted large vertebrates, as these ridges are used for puncturing and holding on to flesh. The teeth are slightly flattened at the top and are roughly conical, which means that they would have been unlikely to break on impact with a thick bone. Teeth at the anterior are taller and more pointed, whereas those at the posterior are lower and more rounded.

''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. One study also indicates that ''Purussaurus'' may have been heavier than either ''Sarcosuchus'' or ''Deinosuchus,'' as it had a much broader, shorter snout and this would require a thicker, stronger neck to support the larger head. '' 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.

All sense organs (eyes, ears, nostrils) were at the very top of the head, indicating that ''Purussaurus'' was an ambush predator like many modern caimans.

Paleoecology

'' Stupendemys'', crocodilians including '' Charactosuchus'', ''Gryposuchus'', and '' Mourasuchus'', '' Anhinga'' birds, and mammals including sloths, bats, rodents such as relatives of the modern capybara weighing up to 700 kilograms (1540 lb), the primate '' Stirtonia'', and river dolphins were all present, and would probably all have been eaten by ''Purussaurus''. Rivers, floodplains, 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.

Etymology

The genus was named for the Purus River where its fossils were first found.

Distribution

Fossils of ''Purussaurus'' have been found in:''Purussaurus''
at Fossilworks.org

;Miocene
* Solimões Formation, Brazil
* Honda Group and Castilletes Formation, Colombia
* Culebra Formation, Panama
* Fitzcarrald Arch and Pebas Formation, Peru
* Urumaco Formation, Urumaco and Socorro Formation, Venezuela

See also

* '' Mourasuchus''

References

Further reading

*
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External links

Tetrapod Zoology post on ''Purussaurus''
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Article about ''Purussaurus'' on ''DinosaurusBlog''

{{Taxonbar, from=Q133296, from2=Q1241636, from3=Q48789986

Alligatoridae
Prehistoric pseudosuchian genera
Miocene crocodylomorphs
Miocene reptiles of South America
Montehermosan
Huayquerian
Chasicoan
Mayoan
Laventan
Colloncuran
Friasian
Neogene Brazil
Neogene Colombia
Neogene Panama
Neogene Peru
Neogene Venezuela
Fossils of Brazil
Fossils of Colombia
Honda Group, Colombia
Fossils of Panama
Fossils of Peru
Fossils of Venezuela
Fossil taxa described in 1892
Taxa named by João Barbosa Rodrigues
Apex predators