Origins of Feathers More Complex Than Previously Thought

Over the last week or so, team members at Everything Dinosaur have reported upon new research into whether dinosaurs were warm-blooded or not.  In addition, in response to requests from readers, we discussed the lack of feathers in dinosaurs such as the fearsome Velociraptors that are featured in the forthcoming movie “Jurassic World”.

Feathered Dinosaurs

This morning, we turn once again to the “were dinosaurs feathered” debate as a new study published in the journal “Biology Letters” suggests that the common ancestor of the Dinosauria was not covered in feathers and indeed, most dinosaurs probably were scaly.

Analysis undertaken by scientists from the Natural History Museum (London), Uppsala University (Sweden) and the Royal Ontario Museum (Toronto, Canada) suggest that feathered dinosaurs were probably the exception amongst the Order Dinosauria.  A comprehensive review of known dinosaur skin fossils coupled with an in-depth study of the dinosaur family tree was used to assess the probability of feathers appearing in different types of dinosaur.

The team conclude that the majority of non-avian dinosaurs were more likely to have had scales like a crocodile or lizard rather than exhibiting signs of feathers or “feather-like” structures.

Once Again Palaeontologists Debate the Extent of Feathers in the Dinosauria

Adult and juvenile feathered dinosaurs.

Picture credit: Xing Lida and Song Qijin

Why do Scientists Get into a Flap over Feathers?

If the majority of dinosaurs had feathers then this has huge implications for dinosaur biology and behaviour.  Insulating feathers infer that the animal that possesses them must be warm-blooded (endothermic), so this argument links directly into the cold-blooded versus warm-blooded dinosaur debate.

To read the article on the research from Stony Brook University that challenges 2014 data on mesothermic dinosaurs and argues that dinosaurs were indeed warm-blooded: Dinosaur Warm-blooded Debate Hots Up.

Thanks to the astonishing fossils from Liaoning Province (China) scientists have been able to identify feathers in a number of different types of theropod dinosaur.  It is widely accepted that many different types of meat-eating dinosaur were feathered or at least partially feathered.

Those dinosaurs which are believed to be closely related to birds provide the greatest number of candidates for feathers rather than scales.  Dinosaurs such as Caudipteryx (Oviraptoridae), Beipiaosaurus (Therizinosauridae), Microraptor (Dromaeosauridae) and Deinocheirus (Ornithomimosauria) were all very probably feathered.  All these dinosaurs are classified as coelurosaurian theropods, the clade of dinosaurs that taxonomically are placed close to the evolutionary line leading to the Aves (birds) fossil evidence supports this hypothesis.

Beautifully Feathered Dinosaur Fossil from Liaoning Province (Microraptor)

Feathers found preserved in many dinosaur fossils from China.

Scored for the Presence of Absence of Feathers

The researchers included thirty-four ornithischian dinosaurs, six sauropods and forty theropods (which included some Mesozoic birds).  These taxa along with a number of others were scored for the presence of feathers or proto-feathers in the fossil record.  Where on the body feathers had been found was also taken into account along with the type of depositional environments that allowed the preservation of filamentous feathers or scaly skin.

Pterosaurs as a group related to the Dinosauria and also archosaurs were included in the study.  Although the fossil record is extremely poor, the team were able to conclude that, based on the probability analysis and the consensus tree that was constructed, it was likely that the ancestor of the dinosaurs was not feathered.  In addition, the research suggests that although the majority of coelurosaurian theropods were indeed feathered to some degree, the majority of other dinosaurs were very probably not feathered.

Commenting on the research, one of the authors of the paper, Nicolás E. Campione (Uppsala University) stated:

“As palaeontologists we are at the mercy of available data, which given the interest in the field are ever changing.  Our study shows that dinosaurs experimented extensively with their “outer look” and potentially independently along separate evolutionary lineages.  That is what the data allows us to say at present.”

The Way Flying Reptiles (Pterosaurs) Were Assessed Affected the Results

Intriguingly, the single biggest influence on the feather versus scales debate in this analysis was the way in which the Pterosauria (flying reptiles) were treated.  Pterosaurs are not dinosaurs, but a related group belonging to the archosaurs just like the Dinosauria.  How closely related the pterosaurs are to the dinosaurs remains an area of controversy.  This research showed that if the ancestor of the Pterosauria was assumed to be scaly then different feather probabilities in the Dinosauria resulted when compared with the study with a fuzzy Pterosaur ancestor included in the database.

Professor Paul Barrett, (Natural History Museum), one of the co-authors of this report summarised the team’s findings:

“Using a comprehensive database of dinosaur skin impressions, we attempted to reconstruct and interpret the evolutionary history of dinosaur scales and feathers.  Most of our analyses provide no support for the appearance of feathers in the majority of non-avian dinosaurs and although many meat-eating dinosaurs were feathered, the majority of other dinosaurs, including the ancestor of all dinosaurs, were probably scaly.”

Feathered Dinosaurs

The biology of the dinosaurs is going to remain a hotly debated topic.  Work such as this new study helps to move the debate forward by reflecting evidence put forward by new fossil discoveries.  However, the fossil record is far from complete and conclusions such as the ones made in this research need to be tested in the light of further fossil finds that help to fill in important and significant gaps in our knowledge of the epidermal coverings of dinosaurs and their close relatives.

To read an article about a fossil find that suggests a Jurassic Ornithischian dinosaur was feathered: Kulindadromeus – Did All Dinosaurs Have Feathers?

A consequence of the inference that most coelurosaurian theropods were probably feathered is that the most famous dinosaur of all Tyrannosaurus rex may also have been covered in a coat of feathers.  Perhaps a young T. rex had a shaggy coat of feathers to help keep it warm.  As the animal grew and became more massive, the need to insulate its body (surface area to volume ratio), became less important.  An adult Tyrannosaurus rex, however, may indeed have been feathered, at least in part.

As fossils of filaments and feathers are associated with low energy depositional environments and finely grained substrates (not a description readily given to much of the Hell Creek Formation), then palaeontologists may never find a feathered T. rex fossil.

CollectA Will Introduce a Feathered T. rex Model in the Summer of 2015

1:40 scale model of a feathered T. rex.

To view the CollectA scale model range and the feathered T. rex (from late summer 2015): CollectA Prehistoric Life Models.

Partial Theropod Femur – Right People, in the Right Place at the Right Time

News broke this week of the discovery and subsequent description of a partial left femur from a theropod dinosaur that had been found on the south-west tip of Sucia Island, which is part of Washington State.  This is the first time that a dinosaur fossil has been recorded from Washington State.  Sucia Island is part of the San Juan archipelago group of islands, it is a conservation area, part of a marine park (Washington State Marine Park).  Sucia Island is very small, it covers approximately 0.88 square miles, making the island about the size of the Queen Elizabeth Olympic Park in London, the site of the 2012 Olympic Games.

The Shoreline where the Theropod Fossil was Discovered (Sucia Island State Park)

The shoreline where the fossil was found.

Picture credit: Burke Museum

The First Dinosaur

The fossil was collected by a team of palaeontologists from the Burke Museum of Natural History and Culture (Seattle) in May 2012.  The partial femur was located in very hard, silty sandstone rocks which represent a shallow marine environment.  The discovery of the fossil had been made earlier by Burke museum field workers who had been excavating ammonite fossils and other invertebrates from the same bed.  It has taken three years to prepare the fossil for further study by carefully removing the extremely hard matrix and then to identify what type of animal the partial thigh bone might represent.

Based on comparative studies the bone has been ascribed to a tyrannosaur, but more about that later.

Scientists Proudly Show Off Washington State’s First Dinosaur Fossil

Dr Christian Sidor (right), Burke Museum curator of vertebrate palaeontology, and Brandon Peecook (left), University of Washington graduate student, show the size and placement of the fossil fragment compared to the cast of a Daspletosaurus femur.

Picture credit: Burke Museum

Right People at the Right Time

This really is an example of the right people, in the right place at the right time.  Occasionally vertebrate fossils are found in marine deposits, in the United Kingdom, the Dorset coast provides an example of this.  The “Jurassic Coast” around Charmouth and Lyme Regis in Dorset represent a shallow marine environment but the fossilised bones of a dinosaur (Scelidosaurus) have been found.  It seems likely that the corpses of dinosaurs were washed out to sea and once the body cavity had ruptured the carcase sank to the bottom and became covered in sediment permitting the fossilisation process to begin.

The picture above shows Dr Sidor holding the partial femur fossil, Brandon is holding a cast of femur from a tyrannosaur called Daspletosaurus (D. torosus) to allow a visual comparison to be made.  Both scientists are showing the back view of the objects (the posterior view), the photographer is looking at the back of the fossil, this is important to note as an anatomical feature located at the back of the fossil bone is helping palaeontologists to classify the sort of dinosaur the Washington State bone represents.

A Rare Find

To find a dinosaur fossil in an marine environment is very rare and given the strong waves and tides associated with Sucia Island the fossil material could have been quickly washed out to sea and lost forever, so it really is a question of the right people being in the right place at the right time.  The analysis and identification of the femur was undertaken by Dr Sidor (Burke Museum of Natural History and Culture) and Brandon Peecock (University of Washington), their paper has just been published in the on line journal PLOS One.  It is highly unlikely that other fossils related to this individual will be found at the site.

Why a Tyrannosaur?

To answer this question we first have to take a step back.  How do we know that this is a dinosaur bone in the first place?  The fossils are found in a horizon that makes up a member of the Cedar District Formation, Upper Cretaceous strata that outcrops along the north-western coast of the United States and the extreme southern portion of the Canadian Pacific coast around Vancouver.

The exact age of these rocks is debated, but the rocks were probably laid down in the Campanian faunal stage and are perhaps around 80 million-years-old.  During this time, in the Late Cretaceous, North America was divided into several landmasses by the Western Interior Seaway.

Laramidia

The island of Laramidia lay to the west and this strip of land is represented by strata found in Alaska all the way down to Mexico on the western seaboard of this continent.  Dinosaurs were the dominant terrestrial megafauna and much is known about the dinosaurs that roamed the eastern side of Laramidia.  Less is known about those from the western provinces of this landmass, this is due to the relative paucity of fossil material found to date on America’s Pacific coast.  Hence the significance of the Sucia Island discovery.

Dinosaur and Prehistoric Bird Fossil Locations (Western Laramidia)

The Sucia Island fossil site is 3 (highlighted in red).

Picture credit: PLOS One

Three Tell-tale Signs

There are three tell-tale signs that indicate that this fossil fragment represents a potential tyrannosaur, let’s briefly go through these:

• The Size of the Fossil (UWBM 95770)

Although only a fragment of the top part of the femur (see picture below to gain an understanding of which part of the thigh bone has been preserved), the fossil measures a whopping 42.5 cm long and 22.4 cm wide at its widest part (the top end of the fossil, this represents that portion of the femoral head that articulates with the hip socket.  This fossil is from a very large animal, hence the confident dinosaur diagnosis.

The researchers writing in PLOS One undertook a comparative analysis study, comparing this fragment to the bones of theropod dinosaurs.  Based on this analysis, the projected actual size of this thigh bone would be about 1.17 metres long (1.167 metres +/- 63 mm with 95% degree of confidence in the result).

• Anatomical Features Indicate a theropod dinosaur

Although the bone is fragmentary, there is evidence of matrix infill in the medullary cavity (the middle of the bone, where marrow was present).  This indicates that this bone was hollow in the middle, this feature is only seen in theropod dinosaurs in this geological period. Thus, the hollow middle cavity is diagnostic of this bone having come from a theropod dinosaur.

The Fourth Trochanter

• The Clincher!  The Fourth Trochanter

An anatomical feature on the back of the thigh bone (posterior), called the fourth trochanter suggests a theropod dinosaur.  The fourth trochanter is a prominent bump or ridge of bone that indicates muscle attachment.  In this specimen, the fourth trochanter is located in the top third portion of the thigh bone, close to the hip socket.  Its shape and position on the bone suggests Theropoda.  All dinosaurs (all archosaurs for that matter), have this characteristic, but in other big, Late Cretaceous dinosaurs such as ceratopsians and hadrosaurs, the fourth trochanter is shaped differently and in a different position at the back of the femur.

In hadrosaurids for example, the fourth trochanter is located near the middle of the femur and is triangular in shape.  In horned dinosaurs (ceratopsians) the fourth trochanter is typically a long, low, straight ridge, which is also positioned towards the middle portion of the thigh bone.

An Illustration of the Fossil Fragment and Comparison with Left Femur of Daspletosaurus

An illustration of the fossil find.

Picture credit: Burke Museum of Natural History and Culture with additional annotation by Everything Dinosaur

 If you look carefully at the picture above, the bottom end of the fourth trochanter is wider and roughened (distal end).  The top portion (proximal) appears smooth and thinner.  A similar morphology is found on the fourth trochanter of the Late Cretaceous tyrannosaur known as Daspletosaurus (D. torosus).

Daspletosaurus spp.

This explains why the research team have tentatively assigned this fossil fragment to the tyrannosaur family and used Daspletosaurus fossil material as a direct comparison.

An Illustration of Daspletosaurus (D. torosus)

Larger tyrannosaur present in the ecosystem.

Picture credit: Everything Dinosaur

Commenting on the significance of the fossil discovery, Dr Sidor stated:

“This fossil won’t win a beauty contest.  But fortunately it preserves enough anatomy that we were able to compare it to other dinosaurs and be confident of its identification.”

The First Dinosaur from Washington State – A Tyrannosaur?

The partial thigh bone, now tentatively assigned to the same dinosaur clade as Tyrannosaurus rex is on display at Burke Museum.  It is worth noting that based on the thigh bone’s total estimated size, the individual meat-eater the fossil material represents would have been over eight metres in length.  The dinosaur would have been approximately the same size as a Daspletosaurus, a Gorgosaurus or an Albertosaurus (all tyrannosaurids).  Although the tyrannosaurid diagnosis cannot be confirmed with absolute certainty and a definition down to genus level is not possible, the tyrannosaurs dominate the apex predator positions within the Laramidia fossil sites.

Perhaps as many as nine genera have been identified to date, the Late Cretaceous seems to mark the peak in the Superfamily Tyrannosauroidea diversity.

Tyrannosaurs Present in Laramidia

Team members at Everything Dinosaur have tried to list the nine genera of tyrannosaurs identified thus far from strata that represent Laramidia.

1. Albertosaurus
2. Gorgosaurus
3. Tyrannosaurus
4. Daspletosaurus (to read an article about face biting in potential Daspletosaurs): Cannibal Daspletosaurus?
5. Lythronax (to read an article about this dinosaur discovery): The King of Gore.
6. Nanotyrannus (Nomen dubium) – to read more about this potential new genus of tyrannosaurid and the debate surrounding it: Duelling Dinosaurs.
7. Bistahieversor (for a review on the CollectA Bistahieversor model: CollectA Bistahieversor Reviewed.
8. Teratophoneus (refer to the Lythronax article for more information): “Monstrous Murderer” of a Tyrannosaur.
9. Nanuqsaurus – the polar tyrannosaurid: Nanuqsaurus hoglundi.

Dinosaur Provinciality

Palaeontologists have proposed that there was a great deal of dinosaur provinciality within the landmass of Laramidia.  The idea of different parts of the landmass being home to different types of dinosaur has been studied for the last two decades.

Unfortunately, due to the tectonic activity on the Pacific coast of western North America, it is difficult to determine where exactly in Laramidia this new tyrannosaur came from.  It has been suggested that since the end of the age of dinosaurs there has been around 1,800 miles of tectonic displacement in roughly a northerly direction.  This tyrannosaur could have lived as far south as what is now southern California.

CollectA have introduced a wide selection of tyrannosaur models into their not-to-scale range of replicas including a model of Daspletosaurus: CollectA Prehistoric Life Figures.

New Research Suggests Colourful Dinosaur Eggs

Birds today lay many different sized eggs, the New Zealand Kiwi (genus Apteryx), for example, lays an egg that is up to 25% of its entire bodyweight.  The Kiwi lays the biggest egg in proportion to its body size of any living bird.  The Bee Hummingbird (Mellisuga helenae), which we at Everything Dinosaur believe to be the smallest species of bird alive today, lays an egg that is not much bigger than a garden pea.

Palaeontologists know that dinosaurs laid different sized eggs too.  The eggs of a giant titanosaur being many times bigger than the eggs of a small dromaeosaurid.

Dinosaur Eggs

Images released show a selection of the 3,000 dinosaur eggs taken off smugglers by Chinese customs officials.   The pictures nicely illustrates the huge variety of dinosaur egg size and shape.

However, birds today lay eggs not only of different sizes but of many different colours as well and until recently there had not been much research undertaken as to the pigmentation of dinosaur eggs.

Scientists had studied melanosomes to uncover information about feather colour in the Dinosauria, but little work had been undertaken to assess the potential colours of dinosaur eggs.  For many years, scientists had assumed that dinosaurs and primitive birds laid plain, white eggs which were most certainly not coloured.  Intriguingly, if you look at pictures of dinosaur nests as illustrated in many dinosaur books, the eggs tend to be coloured pale or almost white

The Convention is to Colour Dinosaur Eggs White or Pale

Why have white coloured dinosaur eggs?

Coloured Eggs

Pale or white coloured eggs would not necessarily help with camouflage, especially when you consider that due to the size of some of those dinosaur mothers, they could not have laid eggs in a secluded, hidden location.  The chances are that many dinosaurs laid eggs in open and exposed places, hence the need to breed in colonies to afford some protection to their offspring.  Two new studies have shed some light on the potential colour of dinosaur eggs, suggesting that they might have been blue-green instead of pale or plain white.

One study conducted by scientists at Bonn University (Germany) discovered that two pigments that provide colour for extant bird eggs also existed in the eggshells of an oviraptorid dinosaur from China called Heyuannia huangi.

Heyuannia huangi

H. huangi, was typical of the Oviraptoridae. Fossils of several individuals have been excavated from Upper Cretaceous sediments in Guangdong Province (southern China).  The fleet-footed dinosaur was most probably feathered and measured a little over 1.5 metres long when fully grown (about 40% of its body length was made up of its tail)

Thousands of small theropod eggshell fragments have been found in association with the body fossils and it is thought that the sediments represent a H. huangi nesting site.  The German study, which has yet to be peer-reviewed, concludes that the two pigments protoporphyrin and biliverdin, responsible for colouring chicken eggs brown and the eggs of emus and other birds blue, were present in the eggshells of this dinosaur.  The German scientists also related egg colour to the type of nesting habit of the bird concerned.  Birds that lay more open, exposed nests tend to have specific egg colours to help camouflage the eggs.

The team suggest that based on this evidence, dinosaurs such as oviraptorids that laid open nests may have laid eggs that were camouflaged.  Heyuannia huangi for example, could have laid blue/green eggs of a similar colour to that of an emu’s egg.  The researchers also propose that the discovery of eggshell pigments may have implications on how the adult dinosaurs looked after the nests.  Behaviours similar to extant birds could perhaps be inferred.

Mapping Pigments

This research builds upon an earlier study undertaken by a team of animal behaviourists at Hunter College in New York.  Professor Mark Hauber, one of the lead authors of the scientific paper, published recently in the academic journal “Biology Letters”, and his team effectively mapped the presence of two pigments protoporphyrin and biliverdin and used the way they combine with each other and blend with the calcium carbonate of the eggshell to predict egg colour.

The New York based team produced a series of computer models that plotted the ways in which these two pigments combine in various ratios and used these models to work out what colour eggs would occur as a result.

Taken together these two studies suggest that different types of dinosaurs may have laid different coloured eggs just as birds do today.  In addition, it seems that the ability to lay camouflaged eggs goes back a long way into the Mesozoic, with the dinosaurs evolving this ability which was then inherited by the Aves.

Oviraptorids May Have Laid Coloured Eggs

Oviraptors may have laid camouflaged eggs.

Picture credit: University of Bonn/PeerJ

Everything Dinosaur and Coloured Eggs

A spokesperson from Everything Dinosaur commented:

“Given the great many hues and colours seen in modern Aves it makes sense that ground-nesting dinosaurs in open environments would have produced eggs that enabled them to blend in with the background of the nest.  Colours seen in fossils, such as the oviraptorid eggs from China pictured above, however, do not normally reflect the actual “true” colours as they would have been in life.  Colouration of the fossil is strongly influenced by the permineralisation process and so readers should not be deceived into seeing fossils of different colours and assuming that is what they were like when, as in this case, the eggs were laid.”

Could it be time for Papo, to change the colour of the dinosaur egg that their model Oviraptor is grasping in its claws?

The Papo Oviraptor Model (with Egg)

A Papo Oviraptor with a blue egg.

Picture credit: Everything Dinosaur

To visit the Papo models section of the Everything Dinosaur website: Papo Prehistoric Animal Models.