Feathered Dinosaurs: Questions and Answers

Dr Maria McNamara (Image: UCC/Tomas Tyner)

Dr Maria McNamara (Image: UCC/Tomas Tyner)

BEES scientist Dr Maria McNamara is part of an international research team who published a paper on a new species of dinosaur this week. The discovery suggests that all dinosaurs were feathered. More on this story here.

How do we know how old the dinosaurs are?

The Kulinda locality is Middle to Late Jurassic in age, about 169-144 million years ago, and probably in the older part of this range, say from 169-150 million years ago. Its age is established from regional mapping in Siberia and from preliminary K/Ar dating. The Kulinda locality rocks belong to the lower part of the Ukureyksaya Formation, which covers large areas around Kulinda, and this geological formation (body of rocks with a certain thickness and geographic extent) is dated from associated plant and insect fossils which can be compared, and correlated, with fossils from other places to give the age. More exact study is needed, and perhaps some radiometric dates from the volcanic rocks at the Kulinda locality to narrow down the age range more closely.

How does the age of these specimens compare with that of other feathered dinosaurs?

The Russian feathered dinosaurs are similar in age to some of the feathered Chinese dinosaurs, such as Anchiornis from the Tiaojishan Formation in NE China. In fact, neither the Russian nor the Chinese rock formations are really well dated, and it will take further work by geologists in both China and Russia to determine the ages of the rocks better, and then to discover whether the Kulinda or Tiaojishan fossils are older.

What environments did they live in?

The Kulinda dinosaur bones are associated with abundant, well preserved fossils of plants, insect larvae, and freshwater crustaceans that suggest deposition in a low-energy, likely lacustrine, fresh-water environment. Probably Kulindadromeus fed on the plants that are found with it, including conifers, seed ferns, and horsetails. The dinosaur bones are not in the form of complete skeletons, which indicates that the bones have been transported by rivers, but not far, because some elements are associated, such as bones of an arm or leg, and the skin, bearing scales and feathers, is close to the relevant bones.

How are the ‘feathers’ preserved?

The feathers and scales are preserved as carbon-rich films on the rock. These show three types of scales on the lower legs and along the tail, and three types of feather-like structures. The carbon within the feathers and scales appears to have survived (but not necessarily the original biomolecules such as proteins), and so the fine detail of the scales and feathers is preserved with high fidelity.

Why are the feathers preserved?

Normally hair, scales, and feathers disappear during fossilization. This usually happens very early in the long road from the dead animal to the fossil. After the dinosaur died, its carcass would have been picked over by scavengers, including flesh-eating dinosaurs, and perhaps some early mammals, as well as insects. These might well remove all flesh from the bones over a week or so. In the case of the Kulinda dinosaurs, their carcasses did not undergo this scavenging phase, but they were probably washed away by a river and dumped on a slow-moving stretch, perhaps at a bend in the river. They were rapidly covered with muddy sand, and, together with plant and other debris, quickly buried. The mud seems to be still rich in organic matter, so this suggests that there was not a great deal of oxygen in these river-bottom sediments, and the whole site might have been black and sulphurous, so inhibiting further decay.

How important is this new locality?

The Kulinda locality opens a new window on ecosystem evolution. Middle Jurassic terrestrial sites are very rare worldwide, being known mainly from England and China so far. To find a nearly complete ecosystem, from plants to dinosaurs, is very exciting, and each group of fossils requires detailed study. The fossils are also immensely abundant – there are dozens of dinosaur individuals represented – so a detailed ecosystem reconstruction can be made. Of course, to find diverse feather types in an ornithischian dinosaur is of key importance.

How were the specimens discovered?

The site was discovered by Sofia M. Sinitsa, and her team from the Institute of Natural Resources, Ecology, and Cryology, Siberian Branch of the Russian Academy of Sciences, while they were conducting a geological survey in the Olov Depression along the small Kulinda River, close to Chernyshevsk village, in 2009. Four trenches were opened in the lower part of the Ukureyskaya Formation, and they found dinosaur bones. Then, they conducted a further series of excavations nearby in 2010 onwards (during the summer – winters in Siberia are not a good time for such work). In 2012, they invited Dr Pascal Godefroit from the Royal Belgian Institute of Natural Sciences , a world expert on ornithischian dinosaurs, to be involved.

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How common are ornithischians?

Ornithischians represent about half of all dinosaurs, and all of them were plant-eaters. They include unarmoured, two-legged forms that ranged in length from 1-10 m, such as Iguanodon and Lambeosaurus. The most abundant were the hadrosaurs of the Late Cretaceous. Other ornithischians sported armour of various kinds, such as the stegosaurs, with bony plates and spikes down their backs and tails, the ankylosaurs, enclosed in a chain mail of armour plates, the thick-headed pachycephalosaurs, and the ceratopsians, with bony frills over their necks and horns over their eyes and snouts. There are 300 or more species of ornithischians so far known, and they have been found worldwide. Dinosaurs are, however, rare in Russia, with only isolated finds reported from Siberia before.

What is the key significance of the new find?

The new find proves that all dinosaurs had feathers.

Up to now, feathers have been reported from numerous species of theropod dinosaurs, the flesh-eating groups, and this has confirmed a remarkable evolution in feather type and complexity through 50 million years of the Late Jurassic and Cretaceous. Feathers in theropods had begun as simple bristles that provided two functions: insulation and signalling (through bright colours and patterns). They were associated with miniaturization of the advanced theropods, called Paraves, and their wide experimentation with flight.

‘Feathers’ have been reported before in two ornithischians, Tianyulong and Psittacosaurus, but palaeontologists had been cautious about the significance of these because they appeared to be rather simple quills, and perhaps limited in extent over the body. Our new find shows that feathers occurred all over the body in a primitive ornithischian, and that there were three types of feathers, including branching, down-type feathers.

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