Rare fossil from early mammal found in Madagascar

Illustration from Stonybrook University of the giant groundhog type creature that lived alongside the dinosaurs, some 70 million years ago.

Scientists have reconstructed the skull of a groundhog-type creature that lived alongside the dinosaurs on Madagascar, 66-70 million years ago.

The skull of the animal, Vintana sertichi, was 125mm long, double the size of other mammals from the southern supercontinent Gondwana. The authors estimate the body was about 9 kilos, making it the largest known mammal of its time. The results have been published in Nature.

The skull was reconstructed by biologist Elizabeth Dumont from the University of Massachusetts and her assistant Dan Pulaski. They believe Vintana ate a diet of roots, seeds or nut-like fruits and belonged to a group of early mammals known as gondwanatherians. Before this reconstruction, these creatures were only known from some teeth and jaw fragments.

Lead author, palaeontologist David Krause of Stony Brook University says Vintana "reshapes some major branches" of the mammalian family tree, by grouping gondwanatherians with other mammals that had been "very difficult to place".

"We know next to nothing about early mammalian evolution on the southern continents," he says. "No palaeontologist could have come close to predicting the odd mix of anatomical features that this cranium exhibits." Vintana had a powerful bite and moved its jaw upwards and backwards. The skull was discovered by chance in 2010 and is only the third mammalian skull to be recovered from the Cretaceous period in the Southern Hemishpere,

Krause and his colleagues compared the skull to hundreds of other fossils and living mammals and concluded it likely had large eyes, the ability to hear high frequency sounds and a good sense of smell.

The analysis provides evidence that Vintana was probably related to multituberculates, the most successful mammalian contemporaries of dinosaurs on the northern continents, and early herbivores known as Haramiyida.

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