Scientists believe that the creatures from the lower Cretaceous era in north-east China were instantly killed by volcanic eruptions similar to the blast that hit the Roman city of Pompeii.
Much like the residents of the doomed city, the animals were entombed in ash and frozen in their death throes.
The fossil beds of Liaoning province in north-east China dating to 120-130 million years ago has an eclectic array of animals buried there, including the first-known feathered dinosaurs, early mammals, birds, fish and insects, the BBC reported.
According to the scientists, the conifer forests and lakes where these animals once lived were surrounded by volcanoes, and a deadly blast would have sent a surge of incredibly hot gas, ash and rock - known as pyroclastic flow - across the landscape.
The team said that the eruption would have been similar to Mount Vesuvius' eruption in 79 AD, which wiped out Pompeii.
Like people who resided in the city, the ancient animals would have been killed in an instant, and gotten buried under a dense layers of ash.
The study has been published in the journal Nature Communications.
