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For decades , the Yixian Formation was lie with as the " Pompeii " of the dinosaur world . Anan former Cretaceous formation in northeastChina , it holds some of the best maintain fossils on Earth and is a hoarded wealth treasure trove for paleontologists that provides a snap into life 130 million to 120 million year ago .
researcher believed that the formation ’s dodo were keep up by the ash tree posit from volcanic eruptions , similar to how Mount Vesuvius covered the city of Pompeii in 19 infantry ( 6 meters ) of ash in 79 AD .
China’s Cretaceous Yixian Formation holds some of the best preserved dinosaur fossils on Earth.
But now , a Modern studysuggests a surprising plait : these ancient creatures may have been forget in collapsed tunnel , rather than being entombed by volcanic eruptions .
The Yixian Formation is a fossil Au - mine of well - preserve and rare specimen . Past excavation have revealed animals thoroughgoing with inner organ , plume , scales , pelt and belly contents . A uncovering in 2023 even revealed an early mammalian , the sizing of a cat , locked in deadly combatwith a lowly dinosaur .
The fossils are find in two forms : flatten out specimens found in lake sediment and three - dimensional , lifelike skeletons . The latter were initially thought to be the result of catastrophic volcanic upshot that buried them in volcanic dust , freeze them in time .
One fossil assemblage from the Yixian Formation preserved the remains of aPsittacosaurusdinosaur with babies andRepenomamus, a mammal in mortal combat, frozen in mid-action.
concern : last minute of dinosaur and mammal ’s epic ' mortal fight ' conflict preserve by volcanic eruption
But grant to the young study , release Nov. 4 in the journalPNAS , many of these fossils were likely preserved by a less dramatic grounds .
To search for clues on how the fossil were preserved , scientist psychoanalyze zircon sample strike from them . Zircon is a mineral that often forms in volcanic rock and fossils , trap uranium when it forms while excluding booster cable . Uranium is radioactive and tardily decay into leash over millions of years .
By measure the proportion of uranium to lead in zircon , the scientist determined that the fossils in the Yixian Formation were deposited chop-chop around 125.8 million years ago , within a period of just 93,000 years — much short than previously thought .
During this time , three period of wet weather cause sediments to ramp up up in lake and on land far more rapidly than expected . Many of the deceased creatures were quickly buried , and O that normally fuels vector decomposition was sealed out .
The effect was most pronounced in lake , where deposit conglomerate so speedily that flaccid tissues could be keep up in ok point .
The study ’s finding challenge the long - stand theory thatvolcanic activity was responsible for for preserving the fossils . Some researchers antecedently suggested that these creatures were incase by lahar — fast - moving , concrete - like mud flows from volcanic outbreak . But harmonise toPaul Olsen , a paleontologist at Columbia Climate School ’s Lamont - Doherty Earth Observatory and lead author of the new field , lahar are extremely violent and would belike rend apart any living or dead wight in their path , make this explanation unlikely .
Another popular theory was that fast - be active waves of searing ash and natural gas , known as pyroclastic flow , sink the fossils , similar to how Mount Vesuvius inter the residents of Pompeii . These flows excellently struck down Pompeii ’s residents , then blanketed their bodies in layer of ash tree , preserving them in place . The intense heat do victims to adopt " pugilistic " military strength , their limbs drawn tightly inwards as their muscles contract and bodily fluids boiled .
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While there are layer of volcanic ash , lava , and intrusion of magma within the Yixian Formation , the scientist argue that the fogey lack the distinctive signs of a Pompeii - way death . If the Yixian creature had been buried by pyroclastic flows , their plumage , fur , and other tissues would in all likelihood have been incinerated .
Instead of pugilistic strength , many of the Yixian animal were retrieve with limbs tuck well around their dead body , as if they were sleeping when they died . The researchers offer the cause of decease to be sudden burrow crash , potentially by large dinosaurs stomping on the reason above that had become unsound from the wet weather .
" These are probably the most authoritative dinosaur breakthrough of the last 120 class , " Olsen said in a instruction . " But what was say about their method of preservation highlights an of import human bias . That is , to ascribe extraordinary causa , i.e. miracle , to average event when we do n’t understand their stemma . These [ dodo ] are just a snapshot of everyday deaths in normal term over a relatively abbreviated meter . "
