The world was a dangerous place for the first birds. Palaeontologists have found a fossil bird preserved where the stomach of a dinosaur would have been – the first direct evidence that dinos preyed on their feathered relatives.

Palaeontologists have long suspected that birds made up part of the predatory dino diet, but proof has been lacking. No longer: and colleagues at the Chinese Academy of Sciences in Beijing found the near-intact skeleton of a primitive bird nestling suspiciously inside a fossilised predator.

The bird belonged to an extinct group called Enantiornithes and was lying in the ribcage of an early Cretaceous winged theropod called Microraptor gui. They were part of the prehistoric ecosystem known as the Jehol biota, which existed in what is now China and has also yielded numerous spectacular feathered dinosaurs.

The bird skeleton was nearly intact, suggesting it was swallowed whole as live prey rather than scavenged.

Not only do the remains provide clues as to how and what the dinosaur ate, but also where it hunted. The bird’s feet were adapted for perching, suggesting it lived in trees. Microraptor had four wings, which may have allowed it to glide between trees to hunt prey there, says O’Connor’s team.

at the Natural History Museum of Los Angeles County says we need to be cautious about reaching that kind of conclusion, however. “The fact that Enantiornithes are largely viewed as arboreal animals doesn’t mean that they didn’t frequent the ground – like most living arboreal birds, from parrots to woodpeckers,” he says.

Journal reference: , DOI: 10.1073/pnas.1117727108

We may be one of the only animals to move around upright on two legs, but babies learn to walk in the same way that rats, cats, monkeys and birds do.

Francesco Lacquaniti at the University of Rome Tor Vergata, Italy, and colleagues used an (EMG) to record the activity of 20 muscles in the arms, legs and torso during walking.

They took measurements from adults, preschoolers, toddlers and even newborns, who take baby steps when supported and made to walk forwards. The EMG picked up two patterns of activity during newborn “walking”: one pattern causes the legs to flex and extend, the other makes sure that they move alternately as the baby moves forward.

Things become more complicated by the time toddlers are taking their first steps solo, though. Lacquaniti found four neural patterns at this stage: the two patterns seen in newborns, and two more that control subtle movements, such as shifting the weight from heel to toe before the leg leaves the ground and making sure that the knee bends only after the toes are lifted.

Although even as toddlers we are beginning to move in a way that no other animal does, the motor patterns controlling walking in other animals are nearly identical. When Lacquaniti’s team looked at previously published results, they found that newborn rats show the same two patterns as newborn babies. By the time rats reach adulthood they show the four patterns seen in toddlers. Adult cats, rhesus monkeys and guinea fowl also show the four patterns of toddling.

Late development

“During evolutionary history, nature didn’t scrap the old hardware,” says Lacquaniti. “Instead it was modified and tuned to adapt to our needs.”

Human adults differ, though. By adulthood, the four phases have changed subtly in a way not seen in other animals. This might allow us to accommodate complicated arm movements such as grasping objects as we walk, Lacquaniti says.

The results make sense, thinks of the Karolinska Institute in Stockholm, Sweden. We might appear to stand apart from the rest of the animal kingdom because of our unusual posture and the fact that babies take so long to learn to walk – but it’s all a matter of perspective.

“In fact, the reason humans take so long before starting to walk is that the human baby is born very early in the maturation process,” Grillner says. “If age is measured from conception rather than birth, the relationship between brain size and walking age is linear, and humans follow this relationship closely.”

Journal reference: , DOI: 10.1126/science.1210617