A fossilised giant mouse that would have scurried around with dinosaurs has been discovered in Cretaceous-era rocks in northeast China.
The palaeontologists’ description of the mouse as being a giant may be a touch misleading thought – at fifty grams “It was about the size of a vole – or huge mouse,” said researcher Yuanqing Wang.
But the furry little creature, named Jeholbaatar kielanae, did have one superpower. It had amazing hearing, which may have helped it avoid the fast moving ‘raptor’ dinosaurs of the period.
“Based on the shape of the lower cheek, Jeholbaatar would have had an omnivorous diet – feeding on worms, arthropods and plants. It had a distinct jaw movement while chewing” Wang, from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, said.
The spectacularly well-preserved skeleton of Jeholbaatar is virtually complete – and even includes its upper and lower teeth.
The fossil was dug up at a famous animal graveyard known as the Jiufotang Formation in Liaoning Province.
Collectively called the Jehol biota, animals found there include the first-known feathered dinosaurs, early mammals, birds, fish and insects.
Jeholbaatar may well have been a big part of a small dinosaur’s diet. While it would have looked a lot like a modern mouse it was actually part of a separate branch or mammal evolution – the multituberculates.
Multituberculates are the only major branch of mammals to have become completely extinct, and have no living descendants.
They have a 100 million-year fossil history – the longest of any mammalian line.
Mr Wang said: “Owing to the well-preserved nature of the left middle-ear bones, the specimen reveals a unique configuration with more complete components than those previously reported in Cretaceous multituberculates.”
These mammals flourished alongside the dinosaurs because they adapted to eating flowering plants, or angiosperms, that began to appear 140 million years ago.
They even survived the asteroid strike which wiped out the giant reptiles 65 million years ago – and continued to prosper long afterwards.
They eventually vanished from the Earth some 34 million years ago after losing out to other mammals such as primates, hoofed species and rodents.
Mr Wang said: “Here we report a definitive mammalian middle ear preserved in a multituberculate mammal, with complete teeth that are well-preserved and detached from the dentary bones.
“The specimen reveals the transformation of the jaw bone from an independent element into part of the middle ear.”