Myriam Boivin

Instituto de Ecorregiones Andinas · Paleontology

Caviomorph rodents present an astonishing variation in sizes both nowadays and in the past. The objective of this work was to estimate the body mass of 32 extinct caviomorphs. Moreover, we seek to analyse the influence on the estimations of the: i. selected predictors (i.e., measurements on cheek teeth); ii. used reference sample comparing three di...

With their past and current diversities, West Indian caviomorph rodents dominate the terrestrial mammalian fauna of the Caribbean archipelago. Many of these species have recently become extinct, including the emblematic giant forms known as Heptaxodontidae. The higher-level systematics and content of this family have been widely disputed over the l...

Cavies are one of the most-specialized grinding rodents, with folivorous and grass-based diets. Antecedents on head myology are focused mainly on domestic guinea pig. Here, we analyze three specimens of wild caviines (two of Cavia aperea and one of Galea leucoblephara), describing, illustrating, mapping, and weighing facial and masticatory muscles....

Analysis of the incisor enamel microstructure of extinct and extant West Indian caviomorph rodents emphasizes a clear microstructural distinction between the Echimyidae (Capromyinae and Heteropsomyinae) among Octodontoidea and the “Heptaxodontidae”, whose phylogenetic affinities are debated. All capromyines and heteropsomyines have a pattern of ena...

Currently, marsupials (modern members of the Metatheria clade) are widely distributed in tropical and subtropical areas of South America, but poorly represented in the fossil record of these regions. Except for the species-rich fossiliferous localities of La Venta in Colombia, additional Miocene metatherians from tropical, equatorial South America...

Caviid rodents have peculiar craniomandibular specializations toward masticatory propalinal movements and grinding, in relation to a grass-rich diet. The aim of this study is to: (1) analyse the variation of cheek tooth shape in the Caviinae and, (2) quantify the covariation relations between caviine cheek teeth. For this purpose, we perform the fi...

Miocene deposits of South America have yielded several species-rich assemblages of caviomorph rodents. They are mostly situated at high and mid- latitudes of the continent, except for the exceptional Honda Group of La Venta, Colombia, the faunal composition of which allowed to describe the late middle Miocene Laventan South American Land Mammal Age...

The Paleogene record of caviomorph rodents has substantially increased over the last decades, and their evolutionary history better understood by the discovery of their earliest representatives, so far recorded in several pre-Deseadan localities in Peruvian Amazonia. We report here the discovery of new caviomorph fossils from the Balsayacu area in...

Since 2012, we have investigated a stratigraphic section encompassing the late Eocene–earliest Oligocene interval at Shapaja (Tarapoto area, Peruvian Amazonia, ca. 7°S), through paleontological and geological fieldwork. The measured sedimentary series (120 m-thick [West] plus 90 m-thick [East]), assigned to the upper member of the Pozo Formation, r...

The Honda Group of La Venta, Colombia, has yielded a wide array of crown platyrrhine primates, documenting the late Middle Miocene epoch (ca. 12-13 Ma, Laventan SALMA). Although exceptional, this record represents only a snapshot of the evolutionary history of New World monkeys since none of the primate taxa recorded at La Venta had so far been fou...

Après les dinosaures géants du Mésozoïque, les Néotropiques ont hébergé des espèces de très grande taille : une impressionnante mégafaune* brassant poissons, serpents, tortues, crocodiles, oiseaux et mammifères, tout au long du Cénozoïque. Cette profusion de formes gigantesques est d’autant plus inattendue que les faunes néotropicales actuelles en...

The issue is mostly devoted to Neotropical mammals, with original drawings by Mazan and a bunch of nice articles (interchanges, evolution, megafauna, and Caribbean mammals), original illustrations, fantastic drawings by Mazan, and photographs (notably by Antoine Baglan, Quentin Martinez, and Nathan Upham)!

By their past and present diversity, rodents are among the richest components of Caribbean land mammals. Their phylogenetic affinities, the timing of their arrival in the West Indies, and their biogeographical history are all ongoing debated issues. Here we report the discovery of rodent teeth from lower Oligocene deposits (~29.5 Ma) of Puerto Rico...

Paleogene deposits of Peruvian Amazonia have yielded the oldest caviomorph rodent communities from South America, and the clues that their early diversification had occurred in this area. Here we report fossil dental remains of rodents from two new sections located in the vicinity of Juanjui and Balsayacu (San Martín Department, Peruvian Amazonia)....

Although phylogenies imply Asia as the ancestral homeland of the Hystricognathi clade (Rodentia, Ctenohystrica), curiously the oldest known fossil occurrences of hystricognathous rodents are not from Asia but from Africa and South America, where they appear suddenly in the fossil record of both landmasses by the late middle Eocene. Here we performe...

Seven hystricognaths and five anomaluroids have been recently described from the earliest Oligocene of the Dakhla (DAK C2) region of Morocco, based primarily on isolated cheek teeth. Here, we analyzed the enamel microstructure of thirty associated isolated fragments of incisors. Among these specimens, only three display an early stage of uniserial...

We investigate the enamel microstructure of 37 isolated rodent incisors from several late middle Eocene and late Oligocene localities of Contamana (Loreto Department, Peruvian Amazonia), and from the early Oligocene TAR-01 locality (Shapaja, San Martín Department, Peruvian Amazonia). All incisors show an enamel internal portion with multiserial Hun...

We report here a new record of the giant caviomorph Phoberomys corresponding to a fragmentary mandible from the Monte Salvado area, Peruvian Amazonia (Madre de Dios Department). We describe this specimen and compare it with the material previously attributed to Phoberomys. The mandibular fragment is referred to as Phoberomys sp. Found as float on a...

In rodents, and other vertebrates in general, the morphology of tarsal bones, especially the astragalus and calcaneus, has been shown to be tightly linked to locomotor movements. As a result, it has been used to infer locomotor behaviors in extinct species. Recent expeditions in Peruvian Amazonia have led to the discovery of the oldest caviomorph r...

Dental homologies and evolutionary transformations within caviomorph rodents have long been disputed. Here, we participate in these debates in providing new insights from the dental morphology of Paleogene caviomorphs from Peruvian Amazonia (Contamana and Shapaja). Their analyses and comparisons with many hystricognaths allow (1) to generalize some...

The rodent record during the late Eocene‒early Oligocene interval is poorly known in South America. Our team’s recent fieldwork in Peruvian Amazonia allowed for the discovery of five new fossil-bearing localities in a single stratigraphic section at Shapaja (Tarapoto area, San Martín Department), considered as early Oligocene by mammalian biostrati...

Modern African cane-, dassie- and mole-rats, Afro-Asian porcupines, and South American chinchillas, guinea pigs, spiny-rats, etc., make up the natural group of the hystricognathous rodents (Hystricognathi Tullberg, 1899). The hystricognathy is described on their lower jaw, which shows the origin of the angular process distinctly lateral to the plan...

Modern caviomorphs or South American hystricognathous rodents exhibit a great taxonomical and ecological diversity,with a broad spectrum of dietary habits, ranging from frugivorous to grass eaters. Their oldest record dates back to the late middle Eocene from Peruvian Amazonia. Continuous paleontological field efforts have substantially increased t...

Caviomorph rodents have been an important component of South American mammal faunas at least since the Oligocene. Those from the Deseadan South American Land Mammal Age (SALMA; late Oligocene) have been exhaustively studied because they are considered key to understanding the evolution of South American rodents. Deseadan faunas are widely distribut...

Diacodexeidae are the first representatives of Artiodactyla in the fossil record. Their first occurrence is at the very base of the Ypresian (earliest Eocene, 56.0 Ma) with Diacodexis, a genus well diversified during the early Eocene in Europe, especially during the MP7–MP8 + 9 interval. However, most of European species are documented by scarce ma...

Caviomorph rodents represent one of the most successful groups of placental mammals from South America. Despite their modern, Neogene and late Paleogene high diversity, their early evolutionary history has long remained obscure. Recent field expeditions in Peruvian Amazonia have yielded among the earliest representatives of that group, in deposits...

Poster session presented at: 4th Young Natural History Scientists’ Meeting, 2017 Feb. 08, Paris, France.

We provide a synopsis of ~60 million years of life history in Neotropical lowlands, based on a comprehensive survey of the Cenozoic deposits along the Quebra da Cachiyacu near Contamana in Peruvian Amazonia. The 34 fossil-bearing localities identified have yielded a diversity of fossil remains, including vertebrates, mollusks, arthropods, plant fos...