Internal Sources of Preserved Melanin Throw Doubt on Dinosaur Colour

One of the most exciting discoveries in the last two decades or so when it comes to the Dinosauria, was the recognition that fossilised, microscopic structures containing melanin (called melanosomes), could provide an indication of colour.  The shape of the preserved melanosome when compared to the same type of structures found in living animals, gave scientists an insight into the potential colouration of long extinct creatures.

However, new research from a team of palaeontologists led by scientists from Bristol University and University College Cork (Ireland), has upset the colour scheme somewhat.  They have discovered new sources of the pigment melanin such as in the liver, lungs and spleen preserved in fossils, this means how palaeontologists reconstruct the dinosaurs and other extinct prehistoric animals is going to have to be revisited.

Implications for the Dinosauria

This study has implications for the interpretation of colour within the Dinosauria.

A Fossil Frog from the Miocene of Spain – Dark Areas in the Chest Cavity and Legs are Melanosomes

Picture credit: Museo Nacional de Ciencias Naturales, Madrid, (Spain)

Study Published in “Nature Communications”

Writing in the academic journal “Nature Communications”,  the researchers looked at living and extinct amphibians.  It is known that extant vertebrates have melanosomes within internal tissues, the scientists demonstrated that these internal melanosomes have a high fossilisation potential and can vastly outnumber those from the skin.  This means that there could be a bias in fossils for preserved internal melanosomes thus “blurring” the picture when it comes to interpreting the colour of extinct animals.

Back to the Drawing Board?  Do we Really Know the Colour of Extinct Creatures?

Picture credit: Everything Dinosaur

The picture (above) shows a brown Papo Giganotosaurus dinosaur model. Is this an accurate reflection of Dinosauria colouration?

To view the Papo dinosaur model range: Papo Dinosaur Models and Figures.

Powerful microscopes in conjunction with the chemical analysis of body tissues demonstrated that internal melanosomes are abundant.  Lead author of the study, Dr Maria McNamara (University College Cork), stated:

“This means that these internal melanosomes could make up the majority of the melanosomes preserved in some fossils.”

However, all might not be lost as according to Dr McNamara, the shape and size of skin melanosomes are usually different from the melanosomes found in internal tissue.  If this is the case, it might permit palaeontologist to refine their melanosome assessments, differentiating between internal and skin melanosome types.  This could lead to more accurate depictions of extinct animals including dinosaurs.

Experiments with Decaying Frogs

Dr Paddy Orr (University College Dublin), along with Dr McNamara’s PhD student Valentina Rossi, also participated in the research, plotting the decay profiles of frogs in order to gain more information on how internal melanosomes can leak into other body parts during the fossilisation process.

Collaborator, Professor Mike Benton from the University of Bristol’s School of Earth Sciences, commented:

“Understanding the origin of melanosomes is crucial in the new studies of colour in dinosaurs and other extinct beasts.”

Slab and Counter Slab Splitting Can Influence the Picture

How a fossil is found in a slab or concretion can also influence any analysis of melanosomes.  The researchers examined the distribution of soft tissues in the slab and counter slab of fossil amphibians.  If the plane of splitting passes through the middle of the soft tissues, non-integumentary melanosomes can be exposed at the surface, producing nearly identical distributions of soft tissues in the slab and counter slab.

Distribution of Soft Tissues in the Slab and Counter Slab

Picture credit: Nature Communications

The photographs (above), labelled a to f, show near identical distributions of soft tissues in the slab and counter slab components of a fossil.  However, if the fossil is split, not quite in the middle (not a medial split), then the slab and counter slab are likely to show different distributions of soft tissue components.  Internal melanosomes may still be exposed at the surface of the fossil.

Uneven Distribution of Soft Tissue Between Slab and Counter Slab

Picture credit: Nature Communications

The picture (g), is the slab and counter slab of the prehistoric salamander Chelotriton from the Miocene of Spain.  The part of the fossil on the right shows more black staining, the remnants of soft tissues preserved in the fossil.  The plain of splitting of this fossil is not precisely medial, therefore leading to one side of the fossil showing greater staining than its counterpart.

A spokesperson from Everything Dinosaur commented:

“This newly published research, rather than thwarting attempts to reconstruct dinosaurs and other prehistoric animals, might actually lead to a refining of the illustration process, allowing palaeontologists and the palaeoartists that work closely with them to create more accurate reconstructions.”

Everything Dinosaur acknowledges the assistance of a media release from the University of Bristol in the compilation of this article.

Visit the Everything Dinosaur website: Everything Dinosaur.

New Research Examines the Diets of Giant Dinosaurs

How many plants would a ten tonne Diplodocus need to eat to keep it happy and healthy?  For that matter, what about one of its larger cousins such as the macronarian Camarasaurus that tipped the scales at an estimated twenty tonnes?  If you had a pet Dreadnoughtus  (D. schrani), a long-necked, herbivorous dinosaur that was heavier than a dozen African elephants, how much food would you need to feed it each day?

Super-sized Sauropods and Their Super-sized Digestive Tracts

Picture credit: Dean Lomax

Palaeontologists have puzzled over the dietary requirements of these super-sized animals for many years.  One of the theories put forward to explain the huge size of sauropods is that they needed to grow big so that they could carry around their vast digestive tracts that were needed to process the huge volumes of plant matter required to provide them with enough energy to do what dinosaurs needed to do.

Sauropoda body mass becomes a sort of self-fulfilling prophecy.  You grow up fast and grow big to avoid predation, so you require a lot food to sustain your body, the bigger you get the more food you need to keep you going, the larger the stomach, especially as your teeth don’t play any role in helping to break up tough stems and foliage.

A Novel Approach

A team of scientists, including researchers from Leeds University, Nottingham University and the University of Göttingen (Germany), have conducted a novel piece of research so that the dietary needs of the largest terrestrial vertebrates can be better understood.  The team grew their own dinosaur food in atmospheric conditions that replicated the environment of the Late Jurassic.  Writing in the journal “Palaeontology”, the research team report on an experiment in which they grew typical plants that would have played a role in the diet of giant, herbivorous dinosaurs, ferns, horsetails, monkey puzzle trees and ginkgos.

The Ancient Ginkgo (Maidenhair) Tree – Dinosaur Food Assessed in this Plant Growth Experiment

Picture credit: Everything Dinosaur

Plants of the Jurassic Had a Low Nutritional Value

It had been thought that plants growing in an atmosphere with a high amounts of carbon dioxide had low nutritional value.  As a result, herbivorous dinosaurs had to consume vast quantities of plant material in order to obtain enough energy to sustain themselves.

A new experimental approach led by Dr Fiona Gill (School of Earth & Environment, Leeds University), has demonstrated that this may not be the case.  To explore the nutrition of a typical sauropod’s diet, a range of plants were chosen.  Plants representing the understory community, such as a fern (Polypodium vulgare), a type of horsetail (Equisetum hyemale) as well as Ranunculus acris, a member of the buttercup family to represent an early Cretaceous angiosperm (flowering plant), were selected.  Plants representing the forest canopy included the Ginkgo (G. biloba), Araucaria araucana, the monkey puzzle tree and a type of redwood conifer (Metasequoia glyptostroboides).

A Sauropod Stomach Study

The atmosphere was controlled as the plants were grown in walk-in growth chambers and the carbon dioxide concentrations were selected to represent a range of recent estimated CO2 values for the Mesozoic.  Although we are seeing a rise in atmospheric amounts of carbon dioxide today, it has been estimated that during the Age of Dinosaurs there was considerably more CO2 in the atmosphere.  By simulating prehistoric atmospheres, the research team could then cut leaves from the plants and test their nutritional value.  The understory plants were exposed to a Mesozoic climate for three months, the slower growing plants representing the canopy were give six months in the Mesozoic atmospheric conditions.

The Researchers Set Out to Create a Growing Room Atmosphere that Replicated the Conditions of the Mesozoic

An Artificial Sauropod Stomach

An artificial fermentation system was used to simulate digestion of the plant leaves in the sauropods’ enormous stomachs.  This permitted the research team to calculate the leaves’ nutritional value.  The results showed many of the plants had significantly higher energy and nutrient levels than previously believed.

The scientists concluded that these megaherbivores would have needed to consume much less plant material per day than previously thought.  Dinosaur numbers may not have been as constrained by the amount of plant food available.  Ecosystems could have potentially supported a much bigger dinosaur population density.  This might go some way to helping to explain the presence of lots of megaherbivores, including several different genera of sauropod present in the Upper Jurassic Morrison Formation of the United States.

Lead author Dr Gill, explained:

“The climate was very different in the Mesozoic Era, when the huge Brachiosaurus and Diplodocus lived with possibly much higher carbon dioxide levels.  There has been the assumption that as plants grow faster and/or bigger under higher CO2 levels, their nutritional value decreases.  Our results show this isn’t the case for all plant species.”

Higher CO2 Levels

Having modelled the effect of different food metabolisable energy (ME), contents in digested plants and plotted this against estimated energy requirements for different sized sauropods, the scientists concluded that instead of having to consume over a hundred kilograms of plants per day much smaller quantities would be required.  For example, a 10 tonne Diplodocus with an assumed energy requirement of 280 kJ of metabolisable energy per kilogram of body weight per day, feeding exclusively on ferns would need to eat 33.2 kg per day.  If it dined exclusively on horsetails it would need to eat 23.8 kilograms per day.  An elephant, although smaller, as an endothermic mammal has a much greater energy requirement and would need to consume around 40 kilograms of plant material to sustain it.

An African Elephant Compared to a Diplodocid

Picture credit: Everything Dinosaur

Studying Dinosaur Diets

Dr Gill stated:

“The large body size of sauropods at that time would suggest they needed huge quantities of energy to sustain them.  When the available food source has higher nutrient and energy levels it means less food needs to be consumed to provide sufficient energy, which in turn can affect population size and density.  Our research doesn’t give the whole picture of dinosaur diet or cover the breadth of the plants that existed at this time, but a clearer understanding of how the dinosaurs ate can help scientists understand how they lived.”

This research is not limited to the Dinosauria, the same methodology can be utilised to model the atmospheric conditions at other points in geological deep time, to assess the nutritional requirements and feeding habits of long extinct, Miocene and Oligocene mammals for example.

The scientific paper: “Diets of Giants: the Nutritional Value of Sauropod Diet during the Mesozoic” by Fiona L. Gill, Jürgen Hummel, A. Reza Sharifi, Alexandra P. Lee, and Barry H. Lomax published in Palaeontology, the journal of the Palaeontological Association.

Visit the Everything Dinosaur website: Everything Dinosaur.

Ingentia prima – Giant Late Triassic Sauropodomorph from Argentina

Argentina might have been home to huge, plant-eating dinosaurs associated with Cretaceous-aged strata, after all, one of the biggest terrestrial vertebrates known to science is the titanosaur called Argentinosaurus (A. huinculensis), just one of a number of super-sized leviathans from this part of the world.  However, a team of scientists, writing in the academic journal “Nature Ecology & Evolution” have announced the discovery of yet another giant, South American dinosaur. However, this one is a Triassic dinosaur. One that roamed northern Argentina around 210 million years ago.

A Giant Triassic Dinosaur

The dinosaur, classified as a member of the Sauropodomorpha, has been named Ingentia prima and it was certainly very big for a Late Triassic animal, with an estimated body weight of around ten tonnes and a length of approximately ten metres.  To provide a comparison, the sauropodomorph Plateosaurus (P. engelhardti), from the Late Triassic of western Europe, that would have been a contemporary of Ingentia prima, is estimated to have reached a length of about eight metres with a body mass of around four tonnes.  The later sauropodomorph Lufengosaurus (L. huenei), from the Early Jurassic of China, might have been around six metres long and is estimated to have weighed more than 1.5 tonnes, Ingentia is much, much bigger.

Sauropodomorpha Size Comparison

Picture credit: Everything Dinosaur with I. prima illustration by Jorge A. González

First Giant

The discovery of Ingentia prima does rather upset the dinosaurian apple cart.  It had been thought that gigantism in the sauropodomorphs evolved in the Early Jurassic, however, here was a ten-tonne giant, comparable in size to those Early Jurassic sauropods that roamed some thirty-five million years later.  The evolution of giant, plant-eating, long-necked dinosaurs came about as a result of the development of numerous anatomical characteristics but I. prima displays many features of the body plan of basal, small sauropodomorphs and lacks most of the anatomical traits previously regarded as adaptations to gigantism.

The Fossilised Material in the Field (Partial Exposure)

Picture credit: Cecilia Apaldetti

Lead author of the scientific paper, Dr Cecilia Apaldetti (Universidad Nacional de San Juan, San Juan, Argentina), commented:

“It [Ingentia] was enormous.  It was at least twice as large as the other herbivores of the time and until now it was believed the first giants to inhabit the Earth originated in the Jurassic, about 180  million years ago.”

The dinosaur’s scientific name pays tribute to its size, the name translates from the Latin to “first giant”.  It had been thought, that if the first dinosaurs appeared around 230 million years ago, it took fifty million years for the first giants to evolve, the discovery of a partial skeleton in San Juan Province (north-western Argentina), has changed all that.

Quebrada del Barro Formation

The fossil material consisting of shoulder blades, cervical vertebrae (neck bones) and elements from the forelimbs, heralds from the Quebrada del Barro Formation.  The Ingentia fossil material was found adjacent to the fossilised remains of three individuals belonging to the already known and closely related species Lessemsaurus sauropoides, which had been named and scientifically described back in 1999.

The researchers, in addition to describing I. prima formally for the first time, were able to examine the three new specimens of Lessemsaurus sauropoides.  Ingentia has been placed in a newly erected family of long-necked dinosaurs, the Lessemsauridae, a branch of the Sauropoda that evolved gigantic forms like the later Eusauropods (true sauropods).  The Eusauropoda includes those famous Jurassic giants such as Diplodocus, Brontosaurus and Brachiosaurus, as well as the later titanosaurs such as the mighty Argentinosaurus, which roamed Argentina some 115 million years after Ingentia became extinct.

Circular Saws were used to Help Extract the Large Fossil Bones

Picture credit: Cecilia Apaldetti

Why was a Triassic Dinosaur so Big?

Early sauropodomorphs were small, agile bipeds, but the ancestors of Ingentia adopted a different evolutionary strategy.

A spokesperson from Everything Dinosaur commented:

“Developing a larger gut would allow more effective processing of tough vegetation, enabling these types of dinosaurs to extract more nutrients from the plants that they consumed.  Furthermore, by becoming big, these dinosaurs would have had less to fear from the predators that shared their environment, including theropod dinosaurs.  If you are very large, a meat-eating dinosaur might avoid you and look for an easier meal elsewhere.  Becoming a giant is an evolutionary strategy found in a number of herbivorous animals”.

The Remarkable Skeleton of Ingentia prima

The lessemsaurids (Ingentia, Lessemsaurus and a third Early Jurassic dinosaur from South Africa named Antetonitrus), may have lacked the extremely long necks found in later eusauropods, but their bones reveal some remarkable adaptations nonetheless.  Pneumatic structures have been identified in the vertebrae (air sacs), this indicates that these dinosaurs had a sophisticated and extremely efficient bird-like respiratory system.  These air sacs will have also helped to prevent these animals from overheating, a problem with large creatures, (surface area to volume ratio – hence one of the reasons why African elephants have large ears).  This kind of respiratory system implies the presence of cavities in their bones – a pneumatised skeleton that would have helped to lighten the animal and make locomotion more efficient.

Although Ingentia shows these adaptations to gigantism, it lacks many of the features associated with the later sauropods.  For example, its legs were more bent and not the huge, weight-bearing columns associated with the Diplodocidae and the Macronaria.

The Remarkable Bones and Respiratory System of Ingentia prima

Picture credit: Jorge A. González

A Triassic Dinosaur Ahead of its Time

The quality of bone preservation permitted the research team to examine the histology of the dinosaur’s bones.  The scientists compared the bone growth in the new fossils with those of an earlier, bipedal sauropodomorph as well as a later eusauropod.  The histology of the earlier sauropodomorph revealed a cyclical growth pattern, the animal growing in spurts, whereas, the eusauropod bones, when examined in cross-section, revealed another pattern of growth.  This dinosaur grew acyclically, growing throughout its long life.  Members of the newly erected Lessemsauridae family grew differently.  Their bones show evidence of growth spurts, a trait found in their ancestors but when they grew, they really put on a spurt.  The researchers identified a growth rate of around two to three times faster than the already impressive rate of the later eusauropods.

Ingentia demonstrates that the first wave of colossal giant dinosaurs evolved some thirty-five million years earlier than previously thought.  In addition, with an accelerated growth rate, unique limb adaptations and a bird-like respiratory system, the Lessemsauridae got big but they did it in a different way when compared to the later long-necked dinosaurs.

When it comes to the “LESSemsauridae” – Less may actually mean more…

The scientific paper: “An Early Trend Towards Gigantism in Triassic Sauropodomorph Dinosaurs” by Cecilia Apaldetti, Ricardo N. Martínez, Ignacio A. Cerda, Diego Pol & Oscar Alcober published in the journal Nature Ecology & Evolution.

Visit the Everything Dinosaur website: Everything Dinosaur.