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While searching for dinosaur fossils in Argentina , fossilist made an accidental discovery : the oldest pollywog ever line up .
The fossil , unearth in the La Matilde Formation in Patagonia , may finally settle a public debate aboutfrogevolution , the scientist describe Wednesday ( Oct. 30 ) in the journalNature .
A depiction of tadpole and adultNotobatrachus degiustoiin a mid-Jurassic pond in Patagonia.
The fogy is a incredibly save specimen of the frog speciesNotobatrachus degiustoi , all over with imprints of soft tissues , including the animal ’s orb , lamella and nerves , grant to the research .
The specimen date to around 161 million long time ago during the middle Jurassic . Thenext oldest tadpolehad been date to the earlyCretaceous , 145 million to 100 million years ago . The newfound fogey is also the first ancient polliwog that has been matched to its grownup opposite number in the fogy record . It may settle a argumentation about when the tadpole stage of frog ontogenesis evolved .
" There are some researcher that say that probably the most [ ancient ] frogs did n’t have a tadpole stage , " saidMariana Chuliver , an evolutionary biologist at Maimónides University in Buenos Aires and first writer of the theme . That ’s because the honest-to-god frog fossil on record date to the late Triassic ( around 217 million years ago ) , tens of millions of years before the oldest known tadpole fossil . But by discovering this fogey , " we demonstrated that was not true , " she said .
The tadpole fossil has well-preserved features, including the eyes, gills and nerves.
Related : Dinosaur - epoch frog found fossilized with venter full of orchis and was likely toss off during pair
Generally , tadpole dodo are heavy to come by , as the jejune natator usually die while still in water . With scavengers quick to feast on fall critters , the water can sometimes be a bad spot for fossilization . In plus , pollywog are made mostly of gristle and soft tissue ; they do n’t shape the hard bones that fossilise more well until adulthood .
" fortunately , this polliwog is in an innovative point of growth , " Chuliver separate Live Science . The vertebra of the tadpole had begun to ossify , allow researchers to see the hump and ridges of the rachis that helped them identify the species and connect the polliwog to its adult counterpart .
The tadpoles of the Jurassic had ample resources and plenty of time to develop their gigantic bodies.
" The most amazing thing for me is the saving of such soft structures , " Chuliver said , " which is really toilsome to find in the dodo disk . " The size of the specimen was also helpful for name the species , she added . The tadpole was about 6 inch ( 16 centimetre ) long — like a baseball game with a 3 - inch - long ( 7.6 cm ) rear end . The adult frog is just as big , which surprised the researchers .
" Both [ adolescent and adult ] level being gargantuan is really tough to retrieve in nature today , " Chuliver say . But forN. degiustoi , the ponds of the Jurassic had ample resources , and the tadpole could afford a long maturation time , she suggested .
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However , other than its size , the physical structure of theN. degiustoitadpole is very similar to that of a modernistic pollywog . Imprints of spiny projections on the lamella indicated that the tadpole likely even ate the same direction modern tadpoles do , with a filter - feeding system that reserve it to suck plankton , alga and dust from the weewee around it . Considering these complex systems had already evolved in tadpole 161 million years ago , tadpoles have probably been around just as long as adult anuran have , the researchers suggested .
Chuliver hopes to get more funding to repay to the La Matilde Formation in search of more tadpoles to expand the fogy record .
