Jurassic squirrel's secret is out after 165m years

Discovery of furry animal with sharp teeth and poisonous spur provides more clues to the evolution of mammals

The discovery of a small furry beast from the Jurassic era has given scientists fresh insights into the evolution of the first mammals on Earth. The fossilised remains of the squirrel-sized animal that plodded rather than scampered, came from rock dated to 165m years ago, when feathered dinosaurs shared the land.

Named Megaconus, or "large cusp", after its distinctive teeth, the animal was unearthed in Inner Mongolia where it had been preserved in volcanic ash that settled in a freshwater lake. It is thought to be an early relative of mammals, and has some mammalian features, while others are more commonly seen in reptiles.

Preserved among the remnants is evidence of fur and a keratinous spur that jutted from the hind ankle and was probably used to deliver poison to predators. The bones of its middle ear were more primitive, and attached to the jaw as in reptiles. The discovery shows that animals evolved to have fur before the first true mammals emerged. The fur was primarily for insulation, but may also have served a sensory purpose.

The animal belongs to a group called the haramiyids, whose existence was previously based on the scant fossil evidence of isolated teeth. Megaconus had long, rodent-like teeth able to chew plants and munch on insects and worms.

"The teeth have been studied since the 19th century, but nobody had an idea what these animals looked like," said Thomas Martin, a scientist on the team at the University of Bonn.

Details of the discovery are reported in the journal Nature.

Martin said the warm-blooded animal foraged at night and lived on the shores of the shallow freshwater lake where its remains were eventually recovered 165m years later.

In the same issue of the journal, another team of scientists, headed by Jin Meng at the American Museum of Natural History, describe another haramiyid, but come to very different conclusions. The creature, named Arboroharamiya, was of a similar age, to Megaconus, but had long toes and fingers, suggesting it lived in the trees. Meng's team argue that their creature was a fully-fledged mammal, and date the origin of all mammals to more than 200m years ago.

Richard Cifelli at the Oklahoma Museum of Natural History told the Guardian that more fossils were needed to clarify which team was right, and whether the animals were true mammals or more primitive forms.

But he added that the two fossils revealed the great diversity of lifestyles among the animals. Other early mammals evolved to burrow, swim and even glide from tree to tree.


Ian Sample, science correspondent

The GuardianTramp

Related Content

Article image
Making old bones: Joint Mitnor cave reopens with replica fossils
Experts use 3D printing to restore mound of fossilised remains in Devon quarry plundered by thieves in 2015

Maev Kennedy

07, Aug, 2017 @2:43 PM

Article image
Darwin Centre opens to the public

Natural History Museum's £78m cocoon will allow the public to watch – and quiz – scientists in action

Rachel Williams

14, Sep, 2009 @3:00 PM

Article image
'Tired of medals': new letters reveal how Alfred Russel Wallace shunned Darwin's fame
From declining royal honour to refusing to sit for a portrait, correspondences show co-discoverer of evolutionary theory avoiding publicity

Hannah Devlin Science correspondent

14, Jul, 2017 @4:20 PM

Article image
Coral reefs: secret cities of the sea | @GrrlScientist
GrrlScientist: In today’s “Museum Monday” video, we watch a time-lapse as a coral reef aquarium is set up in the Natural History Museum’s Jerwood Gallery. This aquarium will be featured in their upcoming exhibition where the public can learn about the importance of marine coral reef communities.


16, Mar, 2015 @9:57 AM

Article image
Scientists discover Welsh ‘dragon’ dinosaur – the size of a chicken
Pendraig milnerae was related to T rex and likely to have been apex predator despite its size, say experts

Steven Morris

05, Oct, 2021 @11:01 PM

Article image
‘The sheer scale is extraordinary’: meet the titanosaur that dwarfs Dippy the diplodocus
One of the largest creatures to have walked the Earth is to become the Natural History Museum’s new star attraction

Robin McKie Science Editor

26, Nov, 2022 @1:00 PM

Article image
How a heroic hunt for penguin eggs became 'the worst journey in the world'

Scott centennial at Natural History Museum recalls horrific trip across polar wastes to prove link between birds and reptiles

Robin McKie, science editor

14, Jan, 2012 @8:42 PM

Article image
Treasures of the Darwin Centre

A glimpse inside the Natural History Museum's new Darwin Centre

Maev Kennedy

16, Jul, 2009 @11:05 PM

Article image
Animatronics and prehistoric poo bring dinosaurs alive for young visitors

Natural History museum's Age of the Dinosaur exhibition fuses hi-tech models with interactive displays – and fossilised faeces

Adam Gabbatt

20, Apr, 2011 @3:14 PM

Article image
Natural History Museum's Dippy the dinosaur to go on holiday
One of Natural History Museum’s best-loved exhibits – a giant Victorian cast of a diplodocus – to be loaned to any museum in UK big enough to host it

Maev Kennedy

21, Jul, 2015 @7:16 AM