Back in March of last year, when we first reported on the project, the historians behind the restoration told us that the clock held many questions — more than it had answers. Markings on the movement which showed it was an original movement from Jaquet Droz himself differed from markings left on the inside of the wooden cabinet and the bronze decorations. These new creations will perhaps become a part of museum collections around the world someday. Revolution Hong Kong.
By Kevin Cureau.
By Stephanie Ip. By Ken Kessler. Pierre Jaquet-Droz — Keith W. Effectively they would have looked and functioned like the wings of a biplane, with the rear set held below the front pair to avoid turbulence.
The feathered revolution: How dinosaurs became birds | Cosmos
A number of other small dinosaur protobirds also had elongated feathers on their hind limbs; however, in most cases, these appear to be ornamental rather than flight worthy. But it seems dinosaur flight experiments were not restricted to feathers. In came news of a very weird theropod named Yi qi that was only distantly related to the protobirds. Found in Hebei province , which borders Liaoning, Yi is around million years old, the size of a small bantam and estimated to have weighed around grams. What was so weird about this little fella was only apparent because of the extraordinary preservation of skin and feathers alongside the front end of the skeleton.
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Similar to its close relatives, Yi had an elongated third finger as well as a bony strut extending from the wrist. But the beautifully preserved specimen also shows a flap of skin stretching between that long finger, the bony strut and the side of the body. Rather than using its feathers for flight, Yi was gliding on bat-like wings.
With all this aerial experimentation going on, the question remains: why were all these dinosaurs seemingly hell bent on learning to fly, with feathers or without? Recommended How Chinese fossils are rewriting the history of feathered dinosaurs Palaeontology. The short answer seems to be that small theropods had already taken to the trees.
They probably did so to avoid larger predators and to source meaty prey such as insects and small vertebrates nestled among the branches.
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Once they were arboreal tree-dwellers , the ability to glide from tree to tree like flying lizards and possums do today could have allowed them to extend their range and chase other gliders while staying clear of dangers on the ground. When it came to evolving true aeronautical ability, they already had a head-start thanks to a suite of features they had inherited from their theropod ancestors. For starters, they were lightweight. All theropods had hollow but strong bones, an adaptation their ancestors developed to be faster at hunting prey.
Being lightweight helped with gliding, but progressing to powered flight depended on another inherited feature. The shoulder sockets of theropods had rotated so that instead of swinging the arms backward and forward for walking, the arms could come together in front of the animal in a grasping motion to capture prey. This grappling action also appears to be assisted by the furcula acting in a spring-like manner, linking the muscles in the chest to the actions of the arms.
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Any gliding protobird using this grasping action would be performing the first down stroke of powered flight. A further modification was the development of pockets extending from the lungs, which not only increased overall lung capacity but led to a one-way breathing system where air circulates continually through the lungs instead of being pumped in and out the way humans breathe. This breathing system, a characteristic of all modern birds, was also very useful for a pursuit predator.
Feathers, which evolved alongside these other avian characteristics, would complete the journey towards modern birds. They may also have served as ornaments. This set of features — small with lightweight bones, rotated shoulder sockets with a furcula, turbocharged breathing systems and feathers — developed in theropods long before they took to the air and set the scene for protobirds.
Fossil quills have already forced multiple revisions of textbooks. And still, a finding just last year showed that feathers are not done with their revolutionary work. For years, we thought we understood the broad architecture of the dinosaur family tree. British palaeontologist Harry Seeley pointed out in that dinosaurs could be divided into two groups based on whether their hips were lizard-like where the pubis points forward or bird-like where the pubis points back.
Confusingly, it was members of the lizard-hipped rather than bird-hipped variety that gave rise to birds. The lizard-hipped saurischians were in turn divided between the long-necked plant-eating sauropods, such as Brachiosaurus , and the meat-eating theropods. The bird-hipped ornithischians included a huge variety of plant-eating dinosaurs that could be divided into three smaller groups: the armoured dinosaurs including Stegosaurus , the bird-footed ornithopods such as Iguanodon and the horned dinosaurs like Triceratops. Bottom line: Brachiosaurus and Tyrannosaurus were relatively close cousins.
Iguanodon , Stegosaurus and Triceratops were more distantly related. Palaeontologists were quite happy with this binary arrangement until , when another British palaeontologist, Matthew Baron from Cambridge University, completely redrew the family tree.
Baron looked at 74 species of exceedingly rare early dinosaurs from the first half of the Age of Dinosaurs. By analysing a very large set of characters from all over the skeletons, he was able to tease out how the early branches divided right down at the base of the tree. His first finding pushed back the origin of dinosaurs by around five million years to about million years ago. The second completely rewrote dinosaurian prehistory. Instead of a neat, early split between the lizard-hipped and bird-hipped branches, Baron found an even earlier split that placed the lizard-hipped theropods onto the same branch as the bird-hipped group.
Feathers and their hairy antecedents have been found on many theropod dinosaurs and also on several different bird-hipped dinosaurs. But they have never been found among the sauropods. So the new group of dinosaurs consisting of the theropods and the bird-hipped dinosaurs which has been named the ornithoscelidans may be defined by the presence of feathers or feather-like structures covering some portion of the animal.
They may actually be the defining feature of one of the most fundamental splits in the dinosaur tree that occurred very early in their evolution.
The revolution is still underway and many of the preliminary conclusions presented here are far from settled and confirmed. There is still a lot of work to be done, more species to find and classify. This article appeared in Cosmos 79 - Winter under the headline "The feathered revolution". The Royal Institution of Australia has an education resource based on this article.