Two ancient cave-dwellers from the age of the dinosaurs have been found perfectly preserved in amber.
The 99 million-year-old find of two complete cockroaches in a mine in Hukawng Valley, in Myanmar’s Kachin Province, pushes back the date of such "troglomorphic" organisms by over 30 million years.
Troglomorphic organisms are animals that are completely adapted to living in caves. Scientists have long believed that such adaptations must have been made during the millennia-long reign of the dinosaurs but the oldest such fossils found so far date to less than 65 million years ago.
The researchers, led by Hemen Sendi from the Slovak Academy of Sciences, wrote in a paper describing their find: "there is no relevant fossil record of any troglomorphic fauna before K/Pg [the geologic boundary that marks the massive extinction event that killed off the dinosaurs] with the exception of the present find.”
They describe the two dinosaur-age roaches as “exquisitely preserved.”
They added that "Cave environments are well suited for fossilisation of bones and coprolites [or fossilised poo] and the fossil record of cave mammals includes rodents, ungulates, marsupials, ursids, felids, hyaenids, canids, primates and humans,"
The researchers admit that they can’t explain how cave-dwelling cockroaches came to be preserved in amber. The substance is secreted from the bark of trees, which don’t tend to be found in caves.
The researchers speculate that tree roots must have extended into the cave and dripped resin onto the cockroaches, preserving them for millions of years.
They think that the cockroaches may have fed on dinosaur poop in the same way that their modern cousins feed on guano left by birds and bats.
They are currently trying to determine if the exact species of cockroach they have discovered is now extinct, or whether the deceased insects have living relatives.