At a time when the immense majority of mammals were the size of it of shrews and mouse , Vintana sertichiwas a ace hulk . Researchers have unearth the skull of a primitive mammal with unco keen senses who live in Madagascar 66 to 72 million years ago . This giant woodchuck - like critter belong to a mysterious group of mammal call the gondwanatherians , who roamed the ancient supercontinent Gondwana at around the same sentence as dinosaurs . Theworkwas bring out inNaturethis workweek .
Gondwanatherians have only been roll in the hay from quarantined teeth and jaw fragment , so the details of their appearing and evolutionary relationships were hard to determine . Now , a squad led byStony Brook ’s David Krausedescribe a fossilized brainpan ( no humbled jaw ) uncovered in an Upper Cretaceous formation in Madagascar . This is only the third mammalian skull reclaim from the Cretaceous in the southern hemisphere .
Vintanais the Malagasy word for “ chance , ” and it refers to the fossil ’s luck breakthrough . In 2010,Joseph Sertich of the Denver Museum of Nature & Sciencecollected a sandstone block filled with Pisces fossils without know that the skull of a previously unsung mammalian was inside . They also named the species , sertichi , after him .
This 125 - millimeter - long skull is double the sizing of the previous largest - known mammal skull from southerly Gondwana during the eld of dinosaur . The team judge a dead body masses of nine kilograms ( that ’s nearly 20 British pound sterling ) , make it the biggest primitive mammal on that supercontinent during its time – and up to three times the size of it of adult groundhogs today .
Micro - CT scans and skim electron microscopy of the brainpan , nasal enclosed space , and interior pinna reveal thatVintanahad good in high spirits - frequency hearing and a keen sense of olfaction . In fact , 14 percent of its psyche was devoted to interpreting odors , skill reports . Deep , Brobdingnagian socket indicate expectant center , and all of these features suggest it was flying and quick .
The team also modeled the mechanics ofVintana ’s manduction by reconstructing the cranium from CT scans and studying the anatomy of live rodent . The image on the right shows how accent is distributed through the skull under an incisor bite at a extensive gape angle . ( quick colouration betoken low tension , cool colors indicate gamey stress . ) Those long , sabre - alike flanges were for the attachment of massive manduction muscles , intimate thatVintanaenjoyed a assorted dieting of radical , seeds , and ball - alike fruits .
The new findings help clarify where gondwanatherians fit in the mammalian kin tree , remold a few branches even . “ We know next to nothing about early mammalian evolution on the southerly continent , ” Krause says in anews departure . “ The find of Vintana will likely stir up the pot . ” Gondwanatherians , they launch , were closely relate to multituberculates , a long - lived , successful chemical group of rodent - similar mammalian contemporaries of dinosaurs on the northerly continents .
Madagascar had been sequester for over 20 million eld beforeVintana ’s meter . The research worker call back its archaic feature are hangover from when the island was trim down off from Africa , then Antarctica and Australia , and finally the Amerindic subcontinent . Isolation for that long was plenty of sentence for the evolution of these unique mosaic of characteristic .
image : Luci Betti - Nash ( top ) , Joseph Groenke viaNSF(middle),UMass Amherst(bottom )
