Acarechimys hunikuini resided in what is now Brazilian Amazonia around 10 million years ago(Late Miocene date).

The ancient types comes from Octodontoidea, a household of Neotropical hystricognathous rodents within the parvorder Caviomorpha.

“Hystricognathous rodents of the Neotropics, i.e., Caviomorpha, are an interesting mammal group due to the fact that of their amazing taxonomic and environmental variety, which shows an intricate evolutionary history,” stated Dr. Emmanuelle Fontoura, a paleontologist with the Universidade Federal de Santa Maria and CAPPA-Centro de Apoio à Pesquisa Paleontológica da Quarta Colônia, and associates.

“These rodents appear unexpectedly in the South American fossil record at the end of the Eocene date, a minimum of from what we understand from the readily available record, particularly that of Peruvian Amazonia.”

“By the Early Oligocene, they had actually currently diversified, with the very first agents of the crown groups.”

“Present‐day caviomorphs consist of 266 types, structured into 2 significant clades and 4 superfamilies: i) Erethicavioi organizing Cavioidea (e.g., guinea pig and associated types) and Erethizontoidea (New World porcupines), and ii) Octochinchilloi with Chinchilloidea (chinchilla and pacaranas) and Octodontoidea (e.g., spiny rats and associated types).”

“The superfamily Octodontoidea consists of the extant households Abrocomidae, Echimyidae, Octodontidae and Ctenomyidae, plus extinct family trees.”

“This is the wealthiest and most varied clade amongst Caviomorpha, both taxonomically and phenotypically through time.”

The oral remains of Acarechimys hunikuini were gathered throughout excursion in 2019 and 2022 at the PRE06 outcrop of the Solimões Formation near the city of Feijó in the Brazilian state of Acre.

“The Solimões Formation has actually yielded a terrific variety of vertebrate fossils given that the mid‐19th century,” the paleontologists stated.

“Fossil‐bearing areas from this development were just recently dated, exposing optimum ages of deposition within the Tortonian, i.e., Upper Miocene.”

“Mammals are amongst the most varied fossils discovered there, consisting of bats, cetaceans, litopterns, marsupials, notoungulates, primates, rodents, sirenians, and xenarthrans.”

“In addition, fossil remains of birds, crocodilians, chelonians, fishes, amphibians, invertebrates, ichnofossils, and plants have actually likewise been recorded.”

The discovery of Acarechimys hunikuini programs that numerous superfamilies of caviomorphous rodents co-existed in this area, in addition to numerous other animal groups, highlighting the presence of an abundant animals in the Brazilian Amazonia.

Acarechimys potentially emerged throughout the Late Oligocene and varied in the Patagonian area throughout the Early Miocene,” the scientists stated.

“During the Middle Miocene, it infected extra‐Patagonian areas, towards the north of South America.”

“During the Late Miocene, the family tree stayed just in extra‐Patagonian areas.”

“This brand-new record, which is the last look of the genus, supports the hypothesis of the late survival of rodent family trees in the tropics, a pattern that has actually been recorded in octodontoids, hydrochoerines and neoepiblemids.”

“The quick diversity and radiation of Acarechimysin addition to the deficiency of information, divergence of viewpoints in between research studies committed to this group, and the numerous separated teeth reported for the Amazonian area, make the research study of this genus difficult.”

“Further research study is needed to improve our understanding of the diversity and temporal variation of this broad family tree of Octodontoidea.”

The group’s paper was released in the Journal of Vertebrate Paleontology

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Emmanuelle Fontoura et al2024. A brand-new Late Miocene stem Octodontoid (Rodentia: Caviomorpha: Octochinchilloi) from the Solimões Formation (Brazil): paleobiogeographic ramifications. Journal of Vertebrate Paleontology 44 (1 ): e2382822; doi: 10.1080/ 02724634.2024.2382822