The history, importance and anatomy of the specimen that validated the giant Purussaurus brasiliensis Barbosa-Rodrigues 1892 (Crocodylia: Caimaninae).

The Solimões Formation is a southwest geological unit of the Brazilian Amazon, being well-known for the Cenozoic giant eusuchian fossils. Among the eight species of Crocodylia described for this formation, the alligatoroid Purussaurus brasiliensis is the best known worldwide due to its enormous size. The holotype was described in 1892 by Barbosa-Rodrigues, composed by a right hemimandible. Later, two other species were assigned to the genus, but the loss of the type specimen brought a series of doubts and discussions about genus and species validity. Here, we provide a historical reconstruction of the genus Purussaurus, especially with a new description of the specimen DGM 527-R, which was first described by L. I. Price. We also provide a review of Purussaurus brasiliensis as a valid species, highlighting the importance of the paleontologist Diogenes de Almeida Campos to the preservation, study availability and divulgation of the specimen. From the six mandibular features discussed, at least two are putative synapomorphies for the genus: the false ziphodont teeth and the thinning of the medial surface of the mandible posterior to the fourteen alveoli, while the lateral surface become laterally expanded from ninth alveoli to behind. The review of the other species of the genus was aggravated due to little sampling of photos and low quality of those contributions. Finally, the curatorial efforts initiated by Price and kept for decades by Campos turned possible the revision of DGM 527-R, an important specimen for understanding the paleobiology and evolution of the genus, and, consequently P. brasiliensis. Such importance was recognized here scientifically and by Campos when considered this specimen as the center-piece of the exhibition in honor of the centenary anniversary of Price.

Revisiting Gryposuchus jessei Gürich, 1912 (Crocodylia: Gavialoidea): specimen description and comments on the genus.

Gryposuchus Gürich, 1912 is the most diverse genus within the Gavialoidea. However, the type species G. jessei Gürich, 1912 has been subject of controversy and was regarded conspecific with G. neogaeus (Burmeinster, 1885) or G. colombianus (Langston, 1965). Here we provide a revision of G. jessei to verify the conspecific hypothesis and the implications for the genus Gryposuchus. Our study shows that G. jessei is a valid species, and a new specimen was referred to this taxon. The comparisons with other Gavialoidea species enabled the proposition of three exclusive characters for the genus. We further advocate a sister affinity between G. jessei and G. pachakamue.

Morphometry, bite-force, and paleobiology of the late miocene caiman Purussaurus brasiliensis.

Purussaurus brasiliensis thrived in the northwestern portion of South America during the Late Miocene. Although substantial material has been recovered since its early discovery, this fossil crocodilian can still be considered as very poorly understood. In the present work, we used regression equations based on modern crocodilians to present novel details about the morphometry, bite-force and paleobiology of this species. According to our results, an adult Purussaurus brasiliensis was estimated to reach around 12.5 m in length, weighing around 8.4 metric tons, with a mean daily food intake of 40.6 kg. It was capable of generating sustained bite forces of 69,000 N (around 7 metric tons-force). The extreme size and strength reached by this animal seems to have allowed it to include a wide range of prey in its diet, making it a top predator in its ecosystem. As an adult, it would have preyed upon large to very large vertebrates, and, being unmatched by any other carnivore, it avoided competition. The evolution of a large body size granted P. brasiliensis many advantages, but it 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.