Tiny Mongolian Dinosaur may shed “Light on the Origin of Flight”
A combined team of palaeontologists and researchers from the North Carolina State University and the North Carolina Museum of Natural Sciences have published evidence that contradicts many scientists views on how dinosaurs may have evolved into birds.
A widely accepted doctrine had been that miniaturisation was one of the last stages in the long series of changes required in order for dinosaurs to evolve into flying animals, the first avians – birds. However, the US team’s analysis of a small Mongolian dinosaur, recovered from Cretaceous deposits, throws an evolutionary spanner into the works.
Dr Julia Clarke, assistant professor of palaeontology at the university, led the analysis of the new dinosaur species called Mahakala omnogovae (derived from the words for Lord Shiva), which had been discovered in the Gobi desert. This small, basal Dromaeosaur was only 70 cms long and weighed little more than 2-3 kgs. Although, the fossil is far from complete, the researchers are confident that this specimen represents an adult of the species and not a still growing juvenile, so Mahakala is one of the smallest dinosaurs known.
In order to achieve powered flight, animals have to become lighter so that they are able to take off under their own muscle power. Modern birds (Neornithes) have a number of anatomical adaptations to help them fly, for example no teeth, a reduction in the number of digits, the development of a pygostyle and so on; all helpful in making their skeletons lighter and thus assisting in powered flight. It had been thought that miniaturisation would have assisted the evolution of birds, with smaller and smaller dinosaurs able to run faster and leap higher into the air; and over many generations; slowly powered flight evolved from this.
However, with Dromaeosaurs small size was relatively common well before the ability to fly evolved. There are a number of small light-weight dinosaurs known from the late Cretaceous, dinosaurs such as the 1 metre tall Bambiraptor from the Western United States and Byronosaurus. These swift and agile hunters show many bird-like adaptations in their skeletons. Perhaps there was a biological advantage in being small and fast running. Clearly, such small fleet-footed animals would have not been on the menu of the large Tyrannosaurs, even young Tyrannosauridae would have had little chance of catching them. There would have been plenty of food around for such animals, many small mammals, lizards, snakes, insects, even larger dinosaur’s eggs. The feathers on these small dinosaurs would have been essential for insulation, helping these animals to retain body heat.
The evolution of flight and the eventual rise of the birds may have been an “evolutionary side-shoot”, an indirect consequence of being small, feathered and nimble. Many dinosaur families seem to have small members within them whose descendants got bigger not smaller as previously thought. Small size in members of the Dromaeosaur group occurs well before many other innovations in locomotion and growth strategy that would have helped these animals eventually evolve into true birds.
Dr Julia’s work has been published in this month’s edition of the journal “Science”.
The trouble with small, light weight animals whether they are true birds or the dinosaur ancestors of birds, is that they tend not to be found as fossils. Their skeletons are light and delicate and not able to withstand the rigours of fossilisation. Many animals are scavenged and their remains scattered, so there is little chance for scientists to recover an articulated specimen. Chances are there were probably many thousands of different types of small Theropod around in the latter stages of the Mesozoic. The bipedal Theropod body plan is a very successful design, after all it had been around for most of the age of reptiles with very few modifications. These animals would have inhabited areas with plenty of cover such as forests and scrub-land. Forest environments do not lend themselves to the prevailing conditions that allow rapid burial and fossilisation to occur. Only in rare circumstances can such animals be preserved; such as the sediments that went on to form the lithographic limestone of Solnhofen that permitted remains of Archaeopteryx to be fossilised or the amazing fossils found in the Sihetun region of the Liaoning Province, China.
At best, we still have a very patchy fossil record of the evolution of birds and it may be many more years before scientists are able to piece together the relationship between true birds and non-avian dinosaurs.
The evolution of birds and the roles that certain groups of dinosaurs had to play in this is likely to remain contentious for sometime to come. One puzzle is that an animal such as Archaeopteryx can be found in Late Jurassic sediments and yet more primitive avian features are found in specimens from the Liaoning deposits which are approximately 30 million years younger.
A number of manufacturers have introduced feathered dinosaur models. The American Museum of Natural History have approved a “tube of feathered dinos”, which includes animals such as a feathered Velociraptor, Dilong and Microraptor.
Our favourite feathered friend remains Archaeopteryx, a truly amazing and enigmatic animal with only 7 fossils known to date (one of them consists of a single feather)!
To see a collectible dinosaurs including feathered dinosaurs: Dinosaur and Prehistoric Animal Models.