Paleontologists discover ancient groundhog-like mammal in Madagascar

© Lucille Betti-Nash.

This is an artist’s rendering of Vintana sertichi.

The new fossil mammal, named , belongs to Gondwanatheria (or gondwanatherians), a group of early mammals that lived during the Cretaceous through the Miocene in the Southern Hemisphere, including Antarctica.

The animal's skull was huge, measuring 13 cm long - twice the size of the previously largest known mammalian skull from the entire Age of Dinosaurs of the southern supercontinent Gondwana.

Prof Krause and his colleagues conducted a comprehensive analysis of the fossil, much of it using micro-computed tomography and scanning electron microscopy to reveal minute aspects of its anatomy, including areas like the braincase, nasal cavity, and inner ear that are poorly known in almost all early mammals. They also compared the skull to those of hundreds of other fossil and extant mammals.

"We know next to nothing about early mammalian evolution on the southern continents. This discovery, from a time and an area of the world that are very poorly sampled, underscores how very little we know. No paleontologist could have come close to predicting the odd mix of anatomical features that this skull exhibits," said Prof Krause, who is the first author of a paper published in the journal .

At a time when the vast majority of mammals were mouse-sized, was a super heavyweight.

The animal had a body mass of about 9 kg, almost three times the size of an adult groundhog.

Various features of its teeth, eye sockets, nasal cavity, braincase, and inner ears revealed that it was a large-eyed herbivore that was agile, with keen senses of hearing and smell.

© Joseph Groenke, Stony Brook University / Gary Staab, Staab studios

The cast of the skull of Vintana sertichi with life reconstruction.

These and other features were also used to analyze its relationships to other early mammals.

The results show that and other gondwanatherians were close relatives of multituberculates, the most successful mammalian contemporaries of dinosaurs on the northern continents.

Multituberculates and gondwanatherians also grouped with another enigmatic taxon, the Haramiyida.

The current study is the first to find strong evidence for clustering these three groups together, primarily because the cranial anatomy of gondwanatherians was previously completely unknown.

Dr Zhe-Xi Luo of University of Chicago, who was not involved in the study, said that is "the discovery of the decade for understanding the deep history of mammals; it offers the best case of how plate tectonics and biogeography have impacted animal evolution - a lineage of mammals isolated on a part of the ancient Gondwana had evolved some extraordinary features beyond our previous imagination."

" is also a galvanizing discovery for the future decades," he said. "With features so remarkably different from those of other mammals previously known to science, this fossil tells us how little we knew about the early evolution of mammals - it will stimulate paleontologists to conduct more field exploration in order to advance the frontier of deep time history and evolution."