{"id":292100,"date":"2019-07-15T17:00:52","date_gmt":"2019-07-15T20:00:52","guid":{"rendered":"https:\/\/revistapesquisa.fapesp.br\/?p=292100"},"modified":"2019-07-16T13:19:06","modified_gmt":"2019-07-16T16:19:06","slug":"the-horned-crocodile-of-acre","status":"publish","type":"post","link":"https:\/\/revistapesquisa.fapesp.br\/en\/the-horned-crocodile-of-acre\/","title":{"rendered":"The horned crocodile of Acre"},"content":{"rendered":"

A crocodile with a unique appearance lived between 11 million and 8.5 million years ago in part of what today is the southwest of the Brazilian Amazon. At three to four meters (m) from muzzle to tail, with a skull almost 60 centimeters (cm) long, it was about the size of a black caiman (Melanosuchus niger<\/em>), the largest remaining species from this group of South American reptiles. It probably fed on fish, mollusks, snakes, and medium-sized mammals, as well as turtles. Its most striking feature, however, was the two protrusions on top of its head, similar to the horns of a giraffe. The Brazilian researchers who described the new species in an article published in the Journal of Vertebrate Paleontology<\/em> in January named the species Acresuchus pachytemporalis<\/em>, which roughly translates to “thick-templed crocodile from Acre.”<\/p>\n

Protrusions on top of the skull are not exclusive to this species of crocodilian, a group of reptiles that emerged just over 200 million years ago\u2014a number of extinct species, such as those of the genus Mourasuchus<\/em>, as well as other living species, such as the Cuban crocodile (Crocodylus rhombifer<\/em>), also share this characteristic. “The protuberances of the Acresuchus<\/em>, however, are the largest ever observed in living or extinct crocodilians,” says paleontologist Annie Schmaltz Hsiou, from the Ribeir\u00e3o Preto campus of the University of S\u00e3o Paulo (USP-RP), one of the authors of the article describing the new species.<\/p>\n

“We suspect that the horns of the Acresuchus<\/em> were a feature that distinguished males from females and were used during mating rituals,” says paleontologist Giovanne Cidade, a PhD student being supervised by Hsiou and coauthor of the article.<\/p>\n

The new species was described based on an almost complete skull. Paleontologist Jonas Pereira de Souza Filho, from the Federal University of Acre (UFAC), found the fossil in 1989 during an excavation on the eastern bank of the Acre River in the municipality of Senador Guiomard, 30 kilometers south of the state capital, Rio Branco. Ten other fossilized Acresuchus<\/em> skulls have also been found\u2014nine in Acre and one in the Amazon\u2014but all are less complete. Paleontologist Marcos Bissaro Junior, from the Ribeir\u00e3o group, dated microscopic grains of zircon from two locations of the geological layer where the fossils were found. The results suggest that the Amazon specimen is older and lived about 11 million years ago, while those found in Acre are 8.5 million years old.<\/p>\n

The first Acresuchus<\/em> fossil remained in the UFAC collection awaiting detailed analysis for 30 years, during which time two other names were suggested for the species. At a congress in 1991, Souza Filho and French paleontologist Jean Bocquentin-Villanueva called it Caiman niteroiensis<\/em> in reference to Niter\u00f3i, the location in Senador Guiomard where the skull was found. When he defended his PhD thesis in 1998, Souza Filho changed its name to Caiman pachytemporalis<\/em> due to the protrusions on its head. None of the names are official yet because they have not been published in a scientific journal, as required by the International Code of Zoological Nomenclature.<\/p>\n

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Gerry Zambonini \/ Wikimedia Commons<\/span><\/a> The cuban crocodile, which moves its head so as to show the protrusions of its skull during mating ritualsGerry Zambonini \/ Wikimedia Commons<\/span><\/p><\/div>\n

An analysis of 187 anatomical features of 93 live and extinct crocodilian species indicates that Acresuchus<\/em>, a medium-sized predator, is the closest relative of the extinct Purussaurus<\/em>, the largest known crocodile, which reached as much as 12.5 m in length. Researchers believe that Acresuchus<\/em>, which emerged before Purussaurus<\/em>, was a transitionary species between the smaller and larger crocodilians.<\/p>\n

Diverse species and forms<\/strong>
\nThe official description of Acresuchus<\/em> brings to 31 the number of species of these predators that lived in South America in the Miocene period between 23 million and 5.3 million years ago. Only one\u2014the broad-snouted caiman (Caiman latirostris<\/em>)\u2014has survived to this day. Five other more recent species of these reptiles also live in Brazil today. “Fossil records show that crocodilians were at the height of their diversity during the Miocene geological period,” says Cidade. In a review article published in the Journal of South American Earth Sciences<\/em> in December 2018, before the Acresuchus<\/em> was officially described, Cidade identified 30 crocodilian species that lived in South America in the Miocene.<\/p>\n

“The diversity of life really exploded at the end of that period,” says Argentinean paleontologist Mario Cozzuol, from the Federal University of Minas Gerais (UFMG). The environment at the time was highly favorable to the emergence of new species. The continents already occupied their current position, but the landscape of South America was unique. The central region of the Andes was rising, depositing large volumes of sediment in the vast plains and wide rivers that stretched from Venezuela to northern Argentina and Uruguay (see<\/em> Pesquisa FAPESP issue no. 125<\/em><\/a>). It was a super-wetland roughly the size of Europe, composed of lakes, marshes, grassy fields, and sparse forests.<\/p>\n

In a review article published in the journal Earth-Science Reviews<\/em> in 2010, Cozzuol and Argentine geologist Edgardo Latrubesse, from the University of Texas, USA, listed 224 genera of land and water animals\u2014not including fish\u2014that lived in South America at the end of the Miocene. Two of the most diverse groups were the armadillos and sloths, with 62 genera, and rodents, with 48. Hsiou and her team have described three new species of Miocene rodents since 2012, all related to the current species, the pacarana<\/em>.<\/p>\n

According to Hsiou, such a large variety of crocodilians would only be possible with a combination of the right environmental conditions and high diversity among other animals. “To put it simply,” says Cozzuol, “there was plenty of food available at the time, of every possible size.”<\/p>\n

Project<\/strong>
\nThe Squamata (Reptilia, Lepidosauria) of the Cretaceous and Tertiary (Paleogene\/Neogene) periods in the Bauru, Aiuruoca, and Acre basins: Systems, evolution, and paleoenvironments (n\u00ba 11\/14080-0<\/a>); Junior Researcher Program; Principal Investigator<\/strong> Annie Schmaltz Hsiou (USP-RP); Investment<\/strong> R$733,129.66 (for the entire project).<\/p>\n

Scientific article<\/strong>
\nSOUZA-FILHO, J. P. et al<\/em>. A new caimanine (Crodcodylia, Alligatoroidea) species from the Solim\u00f5es Formation of Brazil and the phylogeny of Caimaninae<\/a>. Journal of Vertebrate Paleontology<\/strong>. 29 jan. 2019.
\nBISSARO-J\u00daNIOR, M. C.\u00a0et al.<\/em> Detrital zircon U-Pb geochronology constrains the age of Brazilian Neogene deposits from Western Amazonia<\/a>.\u00a0Palaeogeography, Palaeoclimatology, Palaeoecology<\/strong>. v. 516, p. 64-70. 15 Fev. 2019.
\nCIDADE, G. M.\u00a0et al.<\/em>\u00a0The crocodylomorph fauna of Cenozoic of South America and its evolutionary history: a review<\/a>.\u00a0Journal of South American Earth Sciences<\/strong>. v. 90, p. 392-411. On-line. 27 Dez. 2018.
\nLATRUBESSE, E. M. et al<\/em>. The late Miocene paleogeography of the Amazon basin and the evolution of the Amazon river system<\/a>.\u00a0Earth-Science Review<\/strong>. v. 99, p. 99-124. Mai. 2010.<\/p>\n","protected":false},"excerpt":{"rendered":"New fossil belonged to the 31st<\/sup> known species of a group of reptiles that lived in South America between 23 million and 5 million years ago ","protected":false},"author":16,"featured_media":292105,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[159],"tags":[255],"coauthors":[105],"class_list":["post-292100","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-science","tag-paleontology"],"acf":[],"_links":{"self":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/292100","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/users\/16"}],"replies":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/comments?post=292100"}],"version-history":[{"count":2,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/292100\/revisions"}],"predecessor-version":[{"id":296521,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/posts\/292100\/revisions\/296521"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media\/292105"}],"wp:attachment":[{"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/media?parent=292100"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/categories?post=292100"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/tags?post=292100"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/revistapesquisa.fapesp.br\/en\/wp-json\/wp\/v2\/coauthors?post=292100"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}