Farmer finds Ancient Dinosaur Trackways

A Bolivian farmer called Primo Rivera who, had since childhood wondered about the strange marks in a rocky hill near his family home has helped a team of palaeontologists discover the oldest dinosaur trackways ever found in his country.

As a boy, Primo had often examined the strange potholes and dents exposed halfway up a rock face but he did not know what to make of them.  It was only when he visited a dinosaur exhibit at Sucre, (the provincial capital), that he realised that the marks etched into the rock near his home might be dinosaur footprints.

“I used to come to look at the prints when I was a kid … but I didn’t know what had made them,” the farmer commented at a press conference.

The fossilised tracks are believed to date from the very beginning of the Cretaceous period, approximately 140 – 145 million years ago (Berriasian faunal stage).

In pictures, one of the researchers is measuring the stride length of a trackway.  A lot of data can be gathered from such sets of prints, for example, an estimate of the size of the animal and its travelling speed.  Scientists who study fossilised footprints, tracks and other trace fossils are called Ichnologists.

At least three different types of dinosaur are represented by the trackways, including an armoured Ankylosaur type dinosaur.  These are the oldest footprints of Ankylosaurs ever found in the southern hemisphere.  Some of the prints are over 30 cms long and indicate dinosaurs that would have been about 10 metres in length.

Dinosaur Trackways

Pictures show the approximate size of one of the prints (the hand is facing in the same direction as the dinosaur was walking).  The prominent toes indicate ankylosaur, the depth to which the print has sunk shows that this animal was extremely heavy.

Close to the larger prints, the palaeontologists found smaller ones that probably belonged to baby dinosaurs.  This might indicate that ankylosaurs were capable of providing parental care.  Perhaps these large animals protected their offspring.  Ankylosaur trackways have been found in South America before, in fact one such trackway indicates a trotting armoured dinosaur, moving at quite a speed, approximately 10 miles an hour, quite impressive for a large animal.

An Illustration of A Typical Ankylosaurid

Picture credit: Everything Dinosaur

The farmer by chance met a team of scientists carrying out research in the area and took them to see the strange marks in the rocks, once the team had examined them they quickly realised that they were looking at a very special site.

The Thyreophora

This group of armoured dinosaurs, part of the Thyreophora (shield bearers) along with stegosaurs, were built like tanks.  They possessed heavy body armour and in the ankylosaurids – a defensive tail club.  The group persisted right up until the end of the Mesozoic.  The body armour, some species even had armoured eye shields, probably evolved to help protect these relatively slow moving herbivores from large theropods, allosaurs and carcharodontosaurids in South America at the start of the Cretaceous and tyrannosaurs in the northern hemisphere up to the end of the Age of Reptiles.

A Models of Ankylosauridae (Ankylosauridae)

Armoured dinosaur models.

Picture credit: Everything Dinosaur

To view the model of this dinosaur and other armoured dinosaurs: Dinosaur Models and Prehistoric Animal Toys.

Neolithic Grave indicates “Nuclear Family” who met a Violent Death

Analysis of the human remains found buried together in Neolithic graves indicate that our Stone Age ancestors lived in similar family groups as we do.  Genetic study of four bodies found in a 4,600-year old grave near Eulau in Germany shows that four unfortunate victims of a tribal raid were all related to each other and that they were buried together in an intimate arrangement, together in one another’s arms.

This burial site has been studied over the last few years and has yielded remarkable insights into the lives of our ancestors as they moved from a nomadic, hunter-gatherer existence into a more sedentary one.  Earlier research indicated that social groups were built around the menfolk who raided other tribes and stole women.

To read an earlier related article: Evidence of Neolithic Violence – Fighting over the Girls.

The Neolithic remains, which demonstrate evidence of a genetic relationship belong to a man aged between 40 and 60, a woman aged between 35 and 50, and boys aged 4 to 5 and 8 to 9 years of age.  Together they provide the earliest firm evidence for the existence of nuclear family units.

Neolithic Graves

Scientists know that burials were extremely ritualistic, a trait that has remained with us, adults, for example were buried in a particular way with females laid out on one side of their body and males on the opposite side in most ancient burials found in this part of central Europe dating from Neolithic Times.

Pictures show the layout of the skeletons within one of the burial pits. The bodies have been positioned carefully in a close and intimate position, the illustration at the top shows more detail.

The whole site paints a macabre scene, a number of bodies have been uncovered, most showing signs of violent death and defensive wounds such as broken wrists and fingers as they tried to protect themselves from blows.

The majority of the bodies in the graves were children or women, and only one of the skeletons belonged to a man in his prime, aged between 25 and 40.  It is likely that these people were murdered in a raid by a rival tribe, out to steal young women, before the survivors returned to bury their dead.

Studying Ancient Communities

Many anthropologists have assumed, based on observations of sometimes polygamous modern-day hunter-gatherers, that the basic social unit of early humans was the band or tribe rather than the family.  Figuring out when the nuclear family became central to human social organisation has been difficult.

Archaeologists have dug up thousands of skeletons at early farming sites across the Near East and Europe, and many of them are buried together in ways that might suggest family ties.  For example, at the 9500-year-old early farming site of Çatalhöyük in Turkey, excavators have uncovered two skulls with their foreheads touching and the skull of a man cradled in the arms of a woman.  But without DNA evidence, researchers are reluctant to ascribe modern-day interpretations to ancient burials.

Now, a team led by Wolfgang Haak, a geneticist at the Australian Centre for Ancient DNA in Adelaide, claims to have worked out some family relationships in a remarkable series of burials uncovered in central Germany in 2005.  At the early farming site of Eulau, German archaeologists found four graves containing 13 individuals who had apparently met a violent death.

Working with the German team, Haak and colleagues were able to extract enough mitochondrial and nuclear DNA from the skeletons in one of the graves to conclude that the two adults were the parents of the two boys.  In a second, nearby grave, the team concluded that the bodies of three children were probably brothers and sisters, although the adult female found with them was not their mother. Rather, the researchers suggest, she might have been an aunt or a step-mother, perhaps some other close relative.

Commenting on the research, published in the scientific journal “The Proceedings of the National Academy of Sciences”,  Haak and his co-workers state that:

“We have established the presence of the classic nuclear family in a prehistoric context”.

In further analysis, the team studied the strontium isotope content of a number of the skeletons’ teeth, which varies according to the chemistry of the soil where an individual spends his or her childhood. The researchers found that the children and the adult men grew up in the Eulau area of Germany, whereas the adult women came from at least 35 miles away; an indication that nuclear families in this region were organised around local men who mated with women from outside their own community.

“A Great Piece of Work”

“This is a great piece of work,” commented Alexander Bentley, an anthropologist at Durham University. Bentley adds that the new findings, including the signs of violence on the skeletons, such as multiple skull fractures, a flint arrow head lodged in spine of one of the females and defensive marks on the hands and arms, are consistent with other archaeological evidence from Central Europe that men raided outside communities and captured their women.

Other archaeologists argue that the evidence is inconclusive and the author’s claims regarding the biological relationship between the skeletons is stretching matters a little.  The genetic markers the team used are “very widespread in Europe”, according to one source meaning that they cannot be used to work out exact family relations without a broader study of prehistoric skeletons from the region.

Everything Dinosaur stocks the CollectA range of prehistoric animal models, this series also includes models of Stone Age people: CollectA Prehistoric Life Models.

Amargasaurus – A Bizarre Late Diplodocid

As an increasing number of bizarre forms of sauropod have been unearthed for example Amargasaurus. The family tree of these huge long-necked dinosaurs is becoming more complicated.  Although, thanks to recent discoveries of more basal sauropods and prosauropods the evolution of these saurischians has become a little clearer, there is still a lot of confusion over the taxonomic relationships between the various families.

To read further about this: Changing Views on Sauropods.

The Argentine Amargasaurus for instance, is an example of a strange looking, long-necked dinosaur and the strata from which the single fossil skeleton so far known was discovered adds to the mystery of the sauropods.  The global fossil record indicates that the diplodocid type of sauropod was beginning to become rare during the Early Cretaceous. Their heyday appears to have been the Late Jurassic when behemoths such as Diplodocus, Barosaurus and Apatosaurus roamed.  However, the fossils of Amargasaurus date from the early Cretaceous (Hauterivian faunal stage – approximately 135-130 million years ago).  This indicates that this particular group of long-necked dinosaurs were still present, at least in the southern hemisphere during the Early Cretaceous.

Amargasaurus also had a very strange appearance, being relatively small compared to the diplodocids known from the Upper Jurassic deposits of the Morrison Formation of the western United States.  For a start, it was only about 12 metres in length, considerably smaller than Diplodocus and Apatosaurus and it had a much shorter neck, compared to other diplodocids.

The most distinguishing feature though was that along the neck and back of the animal was an array of long, spines extending up from the back bone.  These spines consisted of two rows of long spines over the neck and shoulders, gradually reducing to a set of single spines running along the back to the hind quarters.

An Illustration of Amargasaurus

Picture credit: Everything Dinosaur

To view a model of Amargasaurus and other long-necked dinosaurs: Dinosaur and Prehistoric Animal Models.

The exact purpose of these spines is hotly debated by scientists.  Some believe that they supported a brightly coloured sail that could have been used as signalling device amongst members of the herd, whilst others suggest that the spines were for defence against attack from large meat-eaters that shared the same environment.  Those spines on the neck which are paired, may not have supported a sail, but been covered in horn helping to protect a vulnerable part of this animal’s body.  Certainly, with the likes of members of the Allosaur family wandering around it would pay to have some form of protection, but the precise purpose of these spines remains unclear.

Amargasaurus may be a member of the Dicraeosauridae, a group of sauropods that all possessed long neural spines.  Amargasaurus may have been a descendant of the genus Dicraeosaurus, a diplodocid from the Late Jurassic of East Africa.

Close up of Amargasaurus Head

Picture credit: Everything Dinosaur

As can be seen in this illustration of Amargasaurus, the presence of skin stretched between the large neural spines is played down, instead they are depicted as having more of a defensive purpose.  What ever they were for, this is certainly a very peculiar looking sauropod, with its large neural spines, so of which were over 5 feet tall.

Nesting Dinosaurs – More Evidence from North America

Imagine the scene, it is late in the Cretaceous and a small theropod dinosaur has a difficult decision to make, should it stay, guarding its nest on the banks of a rapidly rising river or make a run for it before the fast rising waters engulf both it and its brood  It’s a tough decision for brooding meat-eating dinosaurs.

That is the scenario imagined by a team of Canadian researchers as they study a unique fossilised dinosaur nest dating from the Campanian faunal stage (dated to approximately 77 million years ago), found in the Medicine Hat Formation of Montana.  The research team have used this fossil dinosaur nest to learn more about how these ancient reptiles constructed nests and brooded eggs.

Brooding Meat-eating Dinosaurs

However, working out what type of dinosaur was responsible for the nest was quite a challenge, the team’s efforts to study this unique find and identify the culprit are written up in the scientific journal Palaeontology.

“Working out who the culprit was in this egg abandonment tragedy is a difficult problem to crack,” commented Darla Zelenitsky, University of Calgary palaeontologist and co-author of a paper, in a statement, part of a Calgary press release.  Dr Zelenitsky, an Associate Professor of the Deparment of Geoscience at Calgary University has worked on a number of North American dinosaur eggshell discoveries, particularly egg fragments discovered in the Oldman Formation (Judith River Group – Alberta), which also date from the Campanian faunal stage.

“After further investigation, we discovered that this find is rarer than we first thought.  It is a one of a kind fossil.  In fact, it is the first nest of its kind in the world.”

It is often difficult to relate the fossil material to a particular dinosaur family (taxonomic reference).  In this case, the specimen of a fossil nest was part of a private collection and had been labelled as belonging to a Hadrosaur (duck-billed dinosaur).  Such misidentification is unstandable, as in the absence of any fossil bones either from brooding adults or embryos still inside the unhatched eggs or the fossil remains of baby dinosaurs, it is difficult to work out what type of dinosaur laid the eggs.

Dinosaur Eggshell Fragments

However, by analysing the eggshell fragments, the team were able to identify that this was the nest of a small meat-eating dinosaur and not from a plant-eating ornithopod.

“Nests of small theropods are rare in North America and only those of the dinosaur Troodon have been identified previously,” added Dr Zelenitsky.

“Based on characteristics of the eggs and nest, we know that the nest belonged to either a caenagnathid or a small raptor, both small meat-eating dinosaurs closely related to birds.  Either way, it is the first nest known for these small dinosaurs.”

Raptors, more appropriately termed dromaeosaurids, were small, agile, hunters of the Late Cretaceous, a typical dromaeosaur would be Saurornitholestes (the name means “lizard bird thief”), a swift predator that reached lengths in excess of two metres.  A number of dromaeosaurid fossils are known from Montana, animals such as the fearsome Deinonychus and the smaller, meat-eater called Bambiraptor – a dinosaur named after the deer in the Disney film.

An Illustration of a Typical Dromaeosaurid

Picture credit: Mike Fredericks/Everything Dinosaur

The picture above shows a typical dromaeosaur, covered with proto-feathers, grasping hands and the three-toed claws with the single retractable claw on each foot.

“Our research tells us a lot about the dinosaur that laid the eggs and how it built its nest,” commented Francois Therrien, another member of the scientific team and curator of Dinosaur Palaeoecology at the Royal Tyrrell Museum in Drumheller (Alberta).

Dinosaur Fossil Nests

The fossil nest is a mound of sandstone, approximately 50 cm in diameter.  The eggs were laid in pairs on the sloping sides of the mound to form a ring of eggs.  The flattened top of the mound was where the adult dinosaur sat to brood the clutch.  Whether, this was the duty of just one of the breeding pair is unknown, perhaps the female brooded the eggs whilst her mate brought food to the nest, or perhaps these little dinosaurs worked in shifts to protect the eggs and keep them warm.  Unfortunately, evidence of behaviour such as this is not preserved in the known fossil record.

A Theropod Dinosaur Nest (Oviraptor)

An Oviraptor and its nest. Picture credit: Everything Dinosaur.

Picture credit: Everything Dinosaur

By studying the fossil the scientists have been able to determine that this dinosaur dug its nest in freshly deposited, loose sand, possibly along the shore of a river.  An analysis of the substrate under the actual fossil indicates that the dinosaur disrupted the rock underneath, indicating that there was a substantial amount of effort put into the digging when excavating the nest.  Perhaps this indicates that the mated pair worked together or that both the front claws and the strong hind limbs were used to construct the nesting mound.

Approximately, a dozen asymmetrical, slightly elongated eggs were laid in pairs against the sides of the mound.  The raised central area was flat, a comfortable place for the dinosaur to crouch down to brood the clutch.   These type of feature can be clearly seen in the fossilised nest of a dromaeosaur shown in many pictures.

The Montana specimen may also represent the nest of a Caenagnathidae dinosaur, a type of dinosaur closely related to the bird-like oviraptorids.  The word caenagnathid means “recent jaws”.  When these Cretaceous animals were first researched, it was noted that the lower jaws possessed several features that resembled the jaws of ostriches and other modern flightless birds.  It was due to this resemblence that these animals were called caenagnathids.

Using high powered microscopes the detail on the outer surface of the eggshells was revealed.  The eggs had a ridge-like pattern on them.  The fact that the eggs were laid in pairs is significant.  This indicates that these dinosaurs had two oviducts (the tubes through which the eggs pass through whilst being laid).  Modern birds have only one oviduct.  Scientists believe that birds lost the second oviduct as this helped them become lighter which was an aid to flight.  The changes in the Aves reproduction processes occurred to prevent them having to fly around with a body full of eggs, this is why a bird may take several days to lay its clutch with one egg being laid at a time.

The evidence from these fossil theropod nests indicate that they laid eggs in pairs, laying from both oviducts at the same time and their exact placement in the nest may show that the mother pushed the eggs down into the sand to secure them in place.  As far as we know from the fossil record no other animal has ever laid eggs in this manner; laying eggs out of both oviducts at the same time.  It is also likely that the eggs were laid in one big clutch with no long interval between laying.  This can be assumed as it would have been difficult for a dinosaur, even one as nimble as a small theropod to return to egg laying, say after laying half her batch.

It would be quite tricky to keep glancing around your legs to make sure that you were laying the next pair of eggs in the right position relative to the previous pair laid.  Best thing to do would be to try to complete the egg laying in one rhythmic sequence, after all, crocodiles lay all their eggs at once.

Finding evidence of two oviducts in theropod dinosaurs is significant, particularly if the nest is suspected of having been made by a dromaeosaur.   This has implications for a theory put forward by the American palaeontologist Greg Paul.  In his book “Dinosaurs of the Air”, published in 2002, Paul puts forward the theory that dromaeosaurs such as Velociraptor and Deinonychus are descended from flying ancestors.  He speculates that the ancestor of these agile, carnivores would have been an animal with the capability of flight but with teeth and claws – something like an Archaeopteryx (Late Jurassic).

At some time between the end of the Jurassic and the Late Cretaceous the descendants of these birds would have lost their power of flight and taken to a ground dwelling existence.  The wings would have gradually become smaller over many generations and the powerful chest muscles required for flight would have been reduced.  The jaws, teeth and the long tail would have been retained, the tail acting as a balancing device rather than a rudder and stabiliser in powered flight.  These dromaeosaurs would have retained feathers as insulation and their warm-blooded metabolism, like flightless birds today such as emus and rheas.  These animals would have gradually become heavier, until the only connections between them and their flying ancestors were subtle similarities in the skeleton.

However, the fact this fossil nest shows evidence of two oviducts in the animal that laid the eggs, challenges this particular theory.  If a dromaeosaur had built this nest then how could an animal such as this have two oviducts, whilst in Paul’s thesis the creatures that it is supposed to be descended from were on their way to having only one?  Unless of course primitive birds did not lose the ability to lay eggs in pairs until much later in their evolution, or this fossilised nest from Montana is not evidence of dromaeosaur activity but caenagnathid instead.

Such fossils as the one studied by the Canadian team, help provide fresh insight into dinosaur behaviour and their anatomy, but they also open up lots and lots of new intriguing questions.

As part of our many dinosaur themed activities the team at Everything Dinosaur published a dinosaur chocolate nest recipe, a fun recipe idea for young palaeontologists to make their own dinosaur nests – and get to eat them as well.  They are easy to make (we have all had a go) and great for parties or just an occasional treat.

Our Dinosaur Chocolate Eggs

Picture credit: Everything Dinosaur

Notice how the mini eggs have been placed in our little dinosaur nests, they have been laid in pairs, just like the eggs laid in the fossil studied by the Canadian palaeontologists.

To view the many dinosaur and prehistoric animal themed gifts and toys available from Everything Dinosaur, visit the company’s website: Everything Dinosaur.

Pleurocoelus – A wastebasket taxon for American Sauropods

As an increasing number of bizarre forms of sauropod are unearthed, the family tree of these huge long-necked dinosaurs is becoming more complicated.  Although, thanks to recent discoveries of more basal sauropods and prosauropods the evolution of these saurischians has become a little clearer, there is still a lot of confusion over the taxonomic relationships between the various families.

Pleurocoelus

To read further about this: Changing Views on Sauropods.

Within the Macronaria (big noses), sub-families that include the camarasaurids and the brachiosaurids for example, there is still a great deal we have to learn about the relationships between these different types of sauropod.  In particular, there is very little in the fossil record to provide clues regarding the classification of brachiosaurs, particularly those found in Late Jurassic and Early Cretaceous rocks.  Even those specimens that have dominated museum exhibits for many years hold their secrets.  The mounted Brachiosaurus fossil in the Humboldt museum, Berlin is actually a composite made up of at least 5 different animals and recently some palaeontologists have argued that this type of brachiosaur from Africa is sufficiently different enough from the North American form to warrant its own genus – Giraffatitan.

Giraffatitan Model Compared to a Tyrannosaurus rex Model

W-Dragon Giraffatitan Compared to a Papo standing T. rex dinosaur model.

To read more about the Brachiosaurus/Giraffatitan debate: Is it Brachiosaurus or Giraffatitan?

Many fossils of North American brachiosaurs have been classified as belonging to the genus called Pleurocoelus (name means hollow sided vertebrae).  Fossils from brachiosaurids from all over the United States (Maryland, Texas as well as the American mid-west) have been attributed to this genus, it has become a “wastebasket taxon” for North American brachiosaurs in a similar fashion to the genus Megalosaurus was used to describe miscellaneous theropod remains from Europe.

Changing Views on Sauropods

Originally described by the famous American palaeontologist Ohniel C. Marsh from fossils discovered in the 1880s this dinosaur is typical of the brachiosaurs with forelimbs bigger than hindlimbs and a long neck.  Estimates of the size of Pleurocoelus vary (depending on which fossil bones are studied), but some scientists have estimated that this dinosaur could have reached lengths in excess of 20 metres and weighed perhaps as much as 40 tonnes.

Pleurocoelus is a state fossil of Texas, an honour awarded to it to this genus in 1997.  Fossils of another dinosaur called Astrodon may actually represent the same genus.  This is unfortunate as Astrodon is the state fossil of Maryland.  Pleurocoelus may be a junior synonym for Astrodon.   In taxonomy, the earliest of several names given to an organism is considered to be senior to any subsequent names and descriptions.  As Astrodon was formerly named in 1865, it is the senior synonym to Pleurocoelus, whilst Pleurocoelus named in 1888 is the junior synonym to Astrodon.

Everything Dinosaur stocks a large range of sauropod models and figures, for example in the scale model range from CollectA: CollectA Deluxe Prehistoric Life/World Figures.