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A termagant - like animal that snagged insect from fern draw the shores of freshwater lakes 160 million class ago , might be one of the first " true " mammals to take the air the Earth , back when the dinosaurs roll , a new fossil suggests .
The new fossil , discovered in what is now Liaoning Province inChina , is the previous grounds of the divergence of these " true " or placental mammals from their pouched mammal counterparts , and indicates the mammalian lineage was evolving faster than gestate during the Jurassic Period . [ Images of the fossil ]
The earliest-known eutherian mammal hunting on a tree fern.
" We can really conclude that the old age of placental mammals live on back to over 160 million twelvemonth ago , " study researcher Zhe - Xi Luo , of the Carnegie Museum of Natural account in Pittsburgh , told LiveScience . " It ’s an evolutionary milepost for mammal evolution . "
True mammals — those that have take over much of the earth and make up 90 percent of today ’s mammal — are different from pouched mammal in several ways . Most importantly , marsupials give nascence to very green baby , which then climb into apouch on the mother’sbelly where they feed and grow . Placental mammals stay in the uterus for this time , until amply developed .
The fresh fogy species , now calledJuramaia sinensis , admit an uncomplete skull , fond skeleton and impressions of soft tissue paper , such as fuzz .
Fossil photograph and restorations of Juramaia
Even though the soft tissue that would show pouched mammal or placental traits — mammary glands or a pouch — had not been retained the fossil ’s forepaw bones and teeth suggest it was secretive to placental mammal than marsupial on the mammal crime syndicate tree . The next - old true mammal fogy dates back about 125 million years .
" We are placing this fossil closer to the placental line thanthe marsupial pipeline , though it is in spades still between the two groups , " Luo said . " It ’s related to and part of our ancestry , but it may not be the direct grandmother to our descent . " [ Gallery : Evolution ’s Most Extreme Mammals ]
The date this fossil Set for the divergence of placentals and marsupials , 160 million years ago , fit well with dates garnered from former genomic analysis .
Skeletal reconstruction and life restoration of the earliest-known eutherian mammal
" This molecular time estimation places the time of split between marsupial and placentals around middle Jurassic , around 165 million years ago , " Luo said . " Previously , the oldest record[ed placental mammal fossil]was 125 million years ago , so there was a solid gap between the fossil record and the molecular estimate . "
By labor back the placental - marsupial division by 35 million years , this fossil evince that even during the age of feather dinosaurs mammal were blow up and evolve into newfangled group quicker than previously believe .
The study was published today ( Aug. 24 ) in the journal Nature .
