An Explanation of Dinosaur “Death Postures”

Many theropod dinosaur fossils if they are discovered as a reasonably complete and articulated specimen depict the animal in a twisted posture, with the neck and tail arched over the spine.  In the past these unusual positions have been interpreted as the “death spasms” of the animal.  Such postures are not restricted to dinosaurs, fossils of birds and other reptiles, especially those with long tails and necks show a similar stance as it were.  New research suggests that these positions are a result of decomposition and bare no relation to the “death throes” of the animal concerned.

More or less complete and articulated skeletons of dinosaurs with a long neck and tail often exhibit a body posture in which the head and neck are recurved over the back of the animal. This posture, also known from Late Jurassic “proto-bird) Archaeopteryx (A. lithographica) , has been fascinating palaeontologists since the first theropod (mainly meat-eating), dinosaur fossils were discovered.  The pose is often referred to as the  “opisthotonic posture”.

To read an earlier article on dinosaur “death throes”: Death Throes – Not Quite What they Seem.

Death Postures

The opisthotonic posture relates to an accessory symptom of tetanus, well known to doctors and to veterinarians.  Usually, an “opisthotonic posture” like that is the result of vitamin deficiency, poisoning or damage to the cerebellum.

The cerebellum is a brain region that controls fine muscle movement, which includes the body’s antigravity muscles that keep the head and tail upright.  If the cerebellum ceases to function, the antigravity muscles will clench at full force, tipping the head and tail back, and contracting the limbs.

A syndrome like that as a petrified expression of death throes was discussed for the first time about 100 years ago for some vertebrate fossils, but the acceptance of this interpretation declined during the following decades.  In 2007, this “opisthotonus hypothesis” was newly posted by a veterinarian and a palaeontologist.

Five years later, two scientists from Switzerland and Germany have re-evaluated the revitalised “opisthotonus hypothesis” and examined one of its icons, the famous bipedal dinosaur Compsognathus longipes from the “Solnhofen Archipelago” (Germany).  An area of Upper Jurassic strata, laid down in what was an extensive lagoonal network.

 A Picture of a Compsognathus Dinosaur Fossil Showing the Death Posture

A result of Bio-mechanics not of “Death Throes”.

Picture credit: G. Janßen, O. Rauhut, Bayerische Staatssammlung für Paläontologie und Geologie)

Sedimentologist Achim Reisdorf from University of Basel’s Institute of Geology and Palaeontology comments:

“In our opinion, the most critical point in the newly discussed scenario of the preservation of an opisthotonic posture in a fossil is the requirement that terrestrial vertebrates must have been embedded immediately after death without substantial transport.  But consigning a carcass from land to sea and the following need of sinking through the water column for only a few centimetres or metres is nothing else.”

Postmortem Alterations of the Skeleton

Convinced that the back arching was generated, not by death throes, but by postmortem alterations of a decaying carcass, the researchers made experiments with plucked chicken necks and thoraxes, immersed in water.  Submersed in water, the necks spontaneously arched backwards for more than 90 degrees.  Ongoing decay for some months even increased the degree of the pose.

Thorough preparation and dissection combined with testing revealed that a special ligament connecting the vertebrae at their upper side was responsible for the re-curved necks in the chickens.  This ligament, the so-called Ligamentum elasticum, is pre-stressed in living chickens, but also in dead ones.

One of the scientists involved in carrying out this, somewhat unusual and macabre research, palaeontologist Michael Wuttke from the Section of Earth History in the General Department for the Conservation of Cultural History Rhineland Palatinate in Mainz (Germany) stated:

“Veterinarians may often have to deal with sick and dying animals, where they see the opisthotonic posture in many cases.  Vertebrate palaeontologists, however, who want to infer the environment in which the animals perished and finally were embedded have to elucidate postmortem processes and bio-mechanical constraints too”. 

It is this tensile, ligament, essential for the effective support of a theropod dinosaur’s long tail and neck that could be responsible for the classic – “dinosaur death pose”.

Michael went onto add:

“The preloaded ligament helped them [dinosaurs] saving energy in their terrestrial mode of life.  Following their death, at which they were immersed in water, the stored energy along the vertebra was strong enough to arch back the spine, increasingly so as more and more muscles and other soft parts were decaying.  It is a special highlight that, in the Compsognathus specimen, these gradual steps of re-curvature can be substantiated, too.  Therefore, bio-mechanics is ruling the postmortem weird posture of a carcass in a watery grave, not death throes.”

For replicas and figures of Compsognathus and other theropod dinosaurs: Papo Models of Prehistoric Animals.

Study of Hazda People of Tanzania Provides Insight into our Earliest Social Networks

A team of Anglo/American scientists have concluded that early humans (H. sapiens) built similar social networks to their modern descendants.  A study of a tribe from Tanzania, that live off the land and act as a model for early human settlements reveals that despite our technology, the way we interact with each other has not changed much for the best part of 200,000 years.

Scientists have speculated that one of the reasons for our own species success when compared to the Neanderthals or indeed H.erectus may have been our ability to develop larger social networks and therefore be able to share information and exchange ideas.  A greater amount of social interaction would have helped ideas to catch on more quickly, thus contributing to our species survival in difficult times.

We carry out an experiment with school children where we split the class into two groups to represent two tribes, set them a problem involving the need to store water and then once one tribe has worked out what to do, we extend the session by getting the students to debate whether or not they would share the information with their neighbouring tribe.  Using an ostrich egg, a stick, ants and a handful of straw we can gain a fascinating insight into human psychology.

Earliest Human Social Networks

The Anglo/American study explores similar themes, permitting an insight to how H. sapiens could survive and eventually flourish despite the difficult climate conditions of the Pleistocene Epoch.  Avoiding extinction, the fate of the dinosaurs is the name of the game.

Writing in the scientific journal “Nature” the research team concludes that prehistoric humans built social networks that resemble those seen in modern societies.  The British and American scientists focused on a single tribe, known as the Hadza who make their living by foraging in the Lake Eyasi region in the Great Rift Valley (Tanzania).

Ironically, this part of Africa is often referred to as the “cradle of humanity” as it is believed, and the fossil record backs this up, that our species evolved in this part of Africa before migrating out of Africa (at least two migrations) and spreading worldwide.

In the study, several interesting patterns of human behaviour emerge.  Humans co-operate readily but also can be selfish.

Emerging Patterns

The patterns that emerged, in which both co-operation and selfishness seemed to be contagious, offer a rare perspective on the question of how the social psychology of early humans has shaped modern social life.  Several hundred Hadza tribes people were involved in the study.  They were given a series of tasks to complete, such as a survey of who their preferred camp-mates were, to whom would they offer food, such as precious sweet honey, the only sweet food item in their diet and highly prized as a result.

The research team also investigated how willing individuals were prepared to work for the good of community – how many would donate honey to a communal pool of the sweet, sticky substance.

Coren Apicella, a post PhD student at Harvard, who analysed the data from the study commented:

“The Hadza represent possibly one of the most extreme departures from life in industrialised societies, and they remain relatively isolated from modern cultural influences,” the authors write.  Yet all the examined properties of social networks seen in modernised societies also appear in the Hadza.”

In a society where the need to build social networks can make the difference between life and death certain common patterns were discovered, patterns that are reflected in modern human interactions.  Popular people befriend other popular people – a pattern of human behaviour reflected in on-line social networks such as Facebook.

People with similar backgrounds and interests are more likely to form a close social tie.  These networks can permit as well as constrain everything from coughs and colds, other diseases to important ideas.  Could this be why the wheel or early metal working caught on so quickly?

For a recent article highlighting a potential incident of human aggression preserved in the fossil record: Earliest Evidence of Human Aggression.

Friendship is something that is not preserved in the fossil record.  However, studying nomadic, hunter-gatherer peoples can provide an insight into how social ties and bonds helped our own species survive and then flourish.  Family ties are strong but social co-operation with non related people is a gamble.  The study identified a certain profile of tribe member who was prepared to take the benefits of social co-operation whilst remaining more selfish and self-interested.

The research team postulate that co-operation may be an evolved behaviour, otherwise unco-operative people would have out-competed co-operative groups long ago.  By working together, what we refer to as the “Sesame Street complex”, people can gain mutual benefit and society is strengthened as a whole.  The advantage gained, according to this study can be multiplied, catch and evolve on.

The authors of the paper suggest:

“Although natural selection is said to favour defection in unstructured populations where all individuals have an equal chance of interacting with one another, co-operation can evolve if population structure permits clustering.  This feature allows co-operators to increase in the population because they benefit from the public goods provided by fellow co-operators with whom they interact.”

The effect is for the co-operative and unco-operative to shun each other.  Among the Hadza, the researchers found that variation between groups was much greater than variation within groups.  In other words, co-operative people cluster together and boost their chances of success, while the unco-operative take their chances on their own, with the ultimate effect of making the human race more co-operative.

Technology may have moved on, but the basic human ability to build networks and develop social ties remains fundamental to our own species survival.  Certainly, with seven billion of us now on planet Earth, it is a good thing that most of us have a social nature “wired” into us.

For models and replicas of prehistoric animals and ancient hominids visit Everything Dinosaur’s award-winning website: Everything Dinosaur.

The World’s Oldest Blackbird Takes Flight

A new Archaeopteryx study suggests that this early bird could achieve powered flight and provides an indication of this Jurassic creature’s colouration.  Using an extremely powerful scanning electron microscope tell-tale melanosomes have been identified in a fossilised feather from the lithographic limestone deposits at Solnhofen.  This new research published in the scientific journal “Nature Communications” not only provides information on the colouration of Archaeopteryx wings – black, but also adds weight to the theory that this primitive bird was an accomplished flier.

New Archaeopteryx Study

The international team of researchers from Brown University (Rhode Island, USA), Yale University, the University of Akron (Ohio, USA) and the Carl Zeiss laboratory (Germany) using advanced microscopy were able to identify the pigment structures found on the fossilised tip of a single feather.  The feather was shed and ended up gently resting on the bottom of a shallow lagoon in what was to become southern Germany by a primitive bird approximately 150 million years ago.

The fine sediments being deposited in the still and anaerobic marine environment enabled the feather to be fossilised.  The unique conditions at Solnhofen, allowed the exquisite preservation of this feather and this fossil specimen is just one of ten ascribed to the prehistoric creature known as Archaeopteryx lithographica.

Black Feathers

The researchers identified the colour of the crow-sized creature’s fossilised wing feather, determining it was black at the tip.  The colour and the structures that supplied the pigment suggest that Archaeopteryx’s feathers were rigid and durable – just like a modern birds and this finding has important implications for the way scientists perceive Archaeopteryx.  It adds weight to the hypothesis that this transitional creature between dinosaurs and birds was actually quite a strong flier.

Archaeopteryx is perhaps one of the most famous of all the creatures known from the fossil record.  Identified and named just over 150 years ago, Archaeopteryx was about fifty centimetres long (most of the length being made up of its feathered covered tail).  It had large eyes, teeth in its jaws and the forelimbs had three greatly extended fingers, each ending in a small, curved claw.  The presence of feathers, so clearly seen in a number of specimens such as the “Berlin specimen” and the “London specimen”, helped scientists to interpret this creature as being a transitional fossil from the Dinosauria to birds – sometimes inaccurately called a “missing link”.

Archaeopteryx fossil cast. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

Commenting on the research work, lead author Ryan Carney, an evolutionary biologist at Brown University stated:

“If Archaeopteryx was flapping or gliding, the presence of melanosomes [pigment-producing parts of a cell] would have given the feathers additional structural support.  This would have been advantageous during this early evolutionary stage of dinosaur flight.”

An Accomplished Aeronaut

Until recently, this single feather was regarded as the holotype for Archaeopteryx.  A holotype is the specimen from which the original description of the organism is based.  This is the fossil that is used to provide a scientific description of the organism, with which all other ascribed fossil material is compared to.  Last year the ICZN (International Commission on Zoological Nomenclature) ruled that the so-called “London” specimen the fossil of Archaeopteryx purchased by Sir Richard Owen for what was to become the London Natural History Museum should be regarded as the holotype.

To read more about this development for Archaeopteryx: Natural History Museum Getting the Bird.

The Fossilised Feather Used in the Study (compared to that of a Modern Bird)

Modern Feather (left), Archaeopteryx Feather (right).

Picture credit: Brown University

If Archaeopteryx was one of the first birds, then what did it look like?  This is a question that has intrigued scientists ever since the first fossils of this Jurassic “missing-link” were found back in the late 1850s.  The single feather was analysed and found to be a covert feather, so named because these feathers cover the primary and secondary wing feathers birds use in flight.  After two unsuccessful attempts to image the melanosomes, the group tried a more powerful type of scanning electron microscope at the Carl Zeiss laboratory, where the group located patches of hundreds of the indicative tube-shaped, pigment structures still encased and preserved in the fossilised feather.

The Electron Microscopy Revealing the Dense Pigment Structures

Pointing to the melanosomes in the fossil.

Image credit: Brown University

Graduate student, Ryan Carney added:

“The third time was the charm, and we finally found the keys to unlocking the feather’s original color, hidden in the rock for the past 150 million years.”

Melanosomes can provide scientists with an indication of the colouration of long extinct animals.  Professor Mike Benton (University of Bristol) and his colleagues have pioneered this melanosome finding technique.  Such structures had been found in fossils before, but they were interpreted as being bacteria, Professor Mike Benton and his team in conjunction with a number of other research institutes were able to identify pigment structures within the fossilised feathers of a dinosaur, providing the first evidence of the colours of a member of the Dinosauria.

To read more about this research: Melanosomes provide evidence of the Colour of Dinosaurs.

The team measured the length and width of the sausage-shaped melanosomes, roughly 1 micron long and 250 nanometers wide.  To determine the melanosomes’ color, Akron researchers Matthew Shawkey and Liliana D’Alba statistically compared Archaeopteryx’s melanosomes with those found in 87 species of living birds, representing four classes: black, grey, brown, and a type found in penguins.  Based on their findings the researchers were able to predict with 95% certainty that this part of the feathers on Archaeopteryx were black.

The scientific instruments and high powered microscopes at the Carl Zeiss laboratory gave the scientists an opportunity to examine the fossilised barbules preserved in the ancient feather.  The barbules are tiny, rib-like appendages that overlap and interlock like a zip to give a feather rigidity and strength.  The barbules and the alignment of melanosomes within them, are identical to those found in modern birds.  If the feather structure of Archaeopteryx is very similar to modern neornithes (modern birds), this implies that Archaeopteryx may have been a capable flier.

A Model of Archaeopteryx with Black Feathers

At Everything Dinosaur, the Wild Safari Prehistoric World Archaeopteryx figure.

Picture credit: Everything Dinosaur

The model shown above is the Wild Safari Prehistoric World Archaeopteryx model.

To see this range: Safari Ltd. Prehistoric Animal Models and Figures.