Purussaurus is a genus of extinct giant caimans that lived in the Americas 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, Argentina, Colombian Villavieja Formation, Panamanian Culebra Formation, Urumaco, and Socorro Formations of northern Venezuela.
Description
One of the largest known skull specimen (UFAC 1403) of the type species, P. brasiliensis, is measured up to 1.4 m (4.6 ft) in maximal skull length from the tip of the snout to the quadrates. In 2015, Aureliano and colleagues assumed that this maximal skull length is equivalent to the dorsal cranial length (DCL), the skull measurement from the tip of the snout to the back of the skull (occipital/parietal area) along the midline, and estimated a body length of 12.5 m (41 ft), ranging from 9.9 to 15.8 m (32 to 52 ft), and a body mass of 8.4 t (9.3 short tons), ranging from 5.6 to 12.6 t (6.2 to 13.9 short tons), with a mean daily food intake of 40.6 kg (90 lb), ranging from 21.6 to 59.5 kg (48 to 131 lb). However, a comment to the paper by Betancourt criticized the authors' assumption, suggesting that the DCL is probably shorter at 1.22 m (4.0 ft), which would produce a smaller estimate of 10.9 m (36 ft) and 5.6 t (6.2 short tons). According to a 2007 study, the dorsal skull length (DSL) of UFAC 1403 is 1.34 m (4.4 ft), and it has been estimated to have been about 9.5 m (31 ft) in length and 4 t (4.4 short tons) in weight. There is also a larger skull (DGM 527-R) not given an estimate in the 2015 study with a length of 1,453 mm (57.2 in) and a mandible length of 1.75 m (5.7 ft) that has been used to produce an estimate of 10.3 m (34 ft) and 5.16 t (5.69 short tons) in the same 2007 study.P. neivensis size has been estimated at 6.5-9 m (21-30 ft) in length and 2 tonnes in weight. A 2022 study also suggested a smaller size estimate, with an estimated length of 7.6–9.3 m (25–31 ft) and mass of 2–6.3 t (2.2–6.9 short tons) using a phylogenetic approach, and an estimated length of 9.3–10 m (31–33 ft) and mass of 3.95–5 t (4.35–5.51 short tons) using a non-phylogenetic approach. A 2025 study estimated based on head width that P. brasiliensis reached an average total length of approximately 7.8 metres (26 ft), while P. mirandai and P. neivensis had average body lengths of 6.55 metres (21.5 ft) and 4.58 metres (15.0 ft) respectively, placing P. brasiliensis as the largest crocodilian in the study, even larger than Deinosuchus.Supplementary Data 2 Table S1 This would possibly make P. brasiliensis the largest crocodyliform to ever exist. Bite force has been estimated to be around 69,000 N (around 7 metric tons-force) in 2015, however the comment to the paper by Betancourt criticizing the authors' assumptions also affects the bite force estimate, bringing it down to around 52,500 N (around 5.3 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, notoungulates, and giant turtles 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 could not survive when its habitat changed, unlike smaller related species of caimans. 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 had three. 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 onto 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, which 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, the Franco-Peruvian 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
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