Santiago, Apr 7 (efe-epa).- A group of South American paleontologists on Wednesday reported the discovery in Chile’s Patagonia region of fossil remains representing a new mammal species from the dinosaur era.
The remains discovered in rocks in southernmost Chile’s Dorotea Formation, part of the Magallanes Region, consist of a partial mandible (lower jaw bone) containing five teeth in sequence and an isolated upper premolar.
They date back to the Late Cretaceous (100.5 million to 66 million years ago), the final epoch of the Mesozoic Era, which lasted from about 252 million to 66 million years ago and is commonly referred to as the age of the dinosaurs.
The discovery of that species, called Orrretherium tzen, was unveiled Wednesday in Scientific Reports, a journal published by Nature Research. Researchers from Universidad de Chile, part of a team of Chilean, Argentine and Brazilian universities involved in the project, said the remains were obtained after several surveys were conducted in the Magallanes Region’s Rio de las Chinas Valley.
The find follows the discovery in that same region of Magallanodon baikashkenke, which constituted the “southernmost record of a Mesozoic gondwanatherian mammal, as well as the first Mesozoic mammal from Chile,” according to a scientific article published last year in Chile’s Bulletin of the National Museum of Natural History.
The Orretherium tzen’s partially preserved partial mandible, which measures less than three centimeters (1.2 inches) in length, has all five teeth in position, an “extremely important” detail that reveals the variation in dental morphology of this species and may help classify other isolated fossilized teeth.
Classified as a meridiolestidan mammal of the Mesungulatidae family, it has a simpler dentition relative to marsupial and placental mammals.
It was closely related to Mesungulatum and Coloniatherium, genuses whose fossils have been found in Late Cretaceous rocks (about 70 million years old) from the Argentine provinces of Rio Negro and Chubut, respectively, and the early Paleocene Peligrotherium (about 60 million years old), found in rocks in Chubut.
But until now the teeth of representatives of mammalian Cretaceous species had either been isolated or lost during the fossilization process.
“The new Chilean species Orretherium tzen is of special importance in discussing the evolutionary origin of an important family of mammals, the mesungulatids,” said Alexander Vargas, who together with Sergio Soto-Acuña coordinated the project on behalf of Universidad de Chile.
“The fossils found in Chile are extremely important to understand the puzzle of the evolutionary history of mammals during the age of the dinosaurs,” said Agustin G. Martinelli, a member of the National Scientific and Technical Research Council of Argentina (Conicet)-Argentine Museum of Natural Sciences who also took part in the project.
Dinosaur remains have been found in South America since the 19th century. However, the first bone remains of mammals from the Mesozoic Era – discovered in Argentina’s Patagonia region – were not located until the early 1980s.
Mesozoic mammals were generally smaller in size than an opossum, and their remains therefore have largely gone unnoticed in large rocky outcrops where dinosaur or crocodile fossils are much more commonly found.