Important Prehistoric Animal Tracks Discovered in Angola

Amongst the many exciting news stories that have come out of the annual Society of Vertebrate Palaeontology meeting held this week in Berlin, is the report from the Paleo Angola Project about the discovery of extensive vertebrate tracks preserved in sediment that now makes up part of a diamond mine in north-eastern Angola.

A New Frontier for Palaeontology

Angola is one of the new frontiers for palaeontology.  This vast, yet underdeveloped country in southern Africa is believed to contain a number of Mesozoic aged, highly fossiliferous deposits and it is likely that any dinosaur fossils excavated from this country are likely to be species new to science.

Researchers Map the Trace Fossil Locations

Mapping the fossil locations.

Picture credit: Paleo Angola Project

The picture above shows an aerial view of some of the trace fossils with their locations highlighted by the research team.  Dinosaur tracks are highlighted in the centre and on the right of the photograph, whilst the mammalian tracks can be seen highlighted towards the bottom left portion of the picture.

Angolan Fossil Exploration

To read an article from Everything Dinosaur about Angolan fossil exploration: Angola Starts to Share its Fossil Secrets.

In a report to the Society of Vertebrate Palaeontology, researchers from the Paleo Angola Project described a location in the silt and sand deposits that represents a lacustrine (lake) environment dating from approximately 118 million years ago (Aptian faunal stage).  Approximately, seventy distinct footprints have been identifed so far.  These trace fossils represent footprints made by sauropod dinosaurs, crocodiles and a relatively large prehistoric mammal.  The mammal print is particularly intriguing.

Most mammals during this part of the Cretaceous were very small, no bigger than rats, but the five-toed print measuring more than three centimetres across indicates that a mammal the size of a Bedlington Terrior dog or a North American Raccoon.  The scientists stated that the tracks were probably made over a substantial period of time, as the lake dried out over several seasons.

A Close Up and Line Drawing of a Single Mammalian Print

Five digits can be clearly seen.

Picture credit: Paleo Angola Project

Studying the Mammalian Track

The mammalian track suggests that in at least this part of Africa, mammals were much larger than previously thought.  The mammal track has been described as “a very rare find.”

Working out what kind of mammal left the rare footprints may not be possible, after all, no body fossils have been found.

Commenting on the discovery, Marco Marzola, one of the palaeontologists with the Paleo Angola Project explained:

“We cannot narrow down to a species but we can say what they [the footprints] do belong to.  They were made by an exceptionally large mammal, that we can say for sure.”

Cretaceous Trace Fossils

In the same location, eighteen sauropod tracks have been discovered, the Paleo Angola Project team have already named and described one giant, long-necked dinosaur that once roamed Angola.  The fossils of this dinosaur were found in marine sediments.  It is likely that the corpse floated out to sea and there is evidence preserved on the fossilised bones of feeding from sharks, that were scavenging the carcase.

To read about the discovery of Angola’s first dinosaur: Angolatitan – Dinosaur that Ended Up as Fish Food.

Praising the action of the consortium which owns the diamond mine (Catoca mine, the fourth largest diamond mine in the world), the scientists said that the mine owners stopped all activity at the mine to allow the researchers to map and plot the trace fossils.  The mine owners put the promotion of vertebrate palaeontology in Angola ahead of their own desire to make money.

Complicated Nasal Passages Helped Keep Ankylosaurs Cool

Animals have a number of ways of controlling their body temperatures and cooling down.  Some warm-blooded animals like kangaroos and antelopes seek shade during the heat of the day.  Elephants cover themselves with mud or take a cooling dip.  Dogs pant and humans sweat, but how did the heavily armoured dinosaurs keep cool?  These “living tanks” with their huge, armoured bodies could have been in danger of overheating as they wandered around in the Mesozoic.

Ankylosaurs with Air Conditioning

A new paper suggests that their complicated nasal passages not only would have helped these animals with their sense of smell, but they would have acted as very efficient heat transfers.

Ankylosaurids with Built in Air Conditioning

Armoured dinosaur models.

Picture credit: Everything Dinosaur

A team of scientists based at Ohio University used CAT scans of ankylosaurid cranial material to map the anatomy of the complex nasal passages in two different North American ankylosaur species.  The team then modelled the air flow in three dimensions using a computer programme that interpreted the CAT scan data.  Palaeontologist Jason Bourke, one of the authors of the scientific paper stated that the complex nasal passages would have given the inhaled air more time to warm up to body temperature by drawing heat way from blood vessels in the nasal cavity.  This would have helped cool the blood and in turn this would have cooled vital organs such as the brain.

Brain Size in Ankylosaurids

The brain of even the largest ankylosaurids was extremely small when compared to their body size.  The dinosaur experts at Everything Dinosaur regularly compare the brain of a large ankylosaur such as Euoplocephalus tutus to the size of a child’s fist.  The nasal passages would have helped to keep the brain in its heavily armoured skull cool and stable.

Mammals and birds use scroll-shaped bones called conchae, otherwise known as turbinates to warm air that is breathed in, but the armoured dinosaurs seem to have achieved the same result with a completely different anatomical configuration.

Transferring Heat Whilst Breathing

Commenting on the study, Jason Bourke stated:

“There are two ways that animal noses transfer heat while breathing.  One is to pack a bunch of conchae into the air field, like most mammals and birds do, it is spatially efficient.  The other option is to what lizards and crocodiles do and simply make the nasal airway much longer.  Ankylosaurs seem to have taken this second approach to the extreme.”

Doctor Lawrence Witmer (Ohio University), who was also involved in this research explained:

“Our team discovered these “crazy-straw” airways several years ago, but only recently have we been able to scientifically test hypotheses on how they functioned.  By simulating airflow through these noses, we found that these stretched airways were effective heat exchangers.  They would have allowed these multi-tonne beasts to keep their multi-ounce brains from overheating.”

Complext Nasal Passages

Ohio University researchers had previously studied the complex nasal passages of another group of ornithischian dinosaurs – the pachycephalosaurs.

To read this earlier article: Nosing Around Pachycephalosaurs.

Just like noses in humans, (Homo sapiens) ankylosaurid noses are likely to have served more than one function.  As the complex nasal passages helped condition the air that was breathed in and out, water may have been removed from exhaled breath helping these dinosaurs to retain water, important when you live in arid environments.  In addition, the convoluted passageways may have added resonance to the low-pitched sounds this dinosaur made.  The nose could have amplified these sounds acting as a resonator, making the noises made by ankylosaurs  heard over greater distances.

A Model of an Ankylosaurus

“Sede” the Ankylosaurus dinosaur model.  A PNSO “Age of Dinosaurs” replica.

Picture credit: Everything Dinosaur

The model (above) is “Sede” the Ankylosaurus from PNSO. To view the range of PNSO prehistoric animal models and figures in stock: PNSO Age of Dinosaurs.

New Study Suggests Egg Shape Might Hint at Clues to Survival

Eggs come in many different shapes and sizes.  There are large ones, small ones, those that are more rounded, others that can be more ovoid in shape and so on.  However, a new study, conducted by evolutionary biologists at Lincoln University (UK), suggests that egg shape could have been a factor in why some birds survived the Cretaceous extinction event, whilst other types of bird and the Dinosauria did not.

New Research

The research published in the on line journal of the Royal Society, looks at the geometry of eggshells and highlights morphological differences between the eggs of birds and those of their extinct, but very close relatives, the theropod dinosaurs.

Birds, Reptiles and Mammals are linked as all these types of creature are descended from Carboniferous tetrapods that evolved an ability to reproduce from an egg that was contained within a semi-permeable eggshell.  These early terrestrial animals were no longer dependent on the presence of water in order to breed and reproduce successfully.  These types of eggs are called amniotic eggs.

A Diagram Showing the Structure of an Amniotic Egg

The growing embryo is protected by a semi-permeable egg shell.

Picture credit: Everything Dinosaur

Amniote Eggs

Safe from drying out, the embryo inside the egg is further protected by a robust, internal membrane called the amnion.  It is the evolution of the amniote egg that permitted tetrapods to conquer all terrestrial environments.

In this new study, the research team noted that there were notable differences between the eggs of birds that survived the Cretaceous mass extinction event that took place around sixty-five million years ago, and the shape of the eggs of those creatures that become extinct.  Although, the fossil record is far from complete when it comes to preserving evidence of eggs and reproductive strategies, the results suggest that early birds from the Mesozoic laid eggs that had different shapes to those of modern birds.

It is possible that egg morphology indicates different physiologies or different rates of embryonic development and this may have implications when it comes to surviving a mass extinction event, such as that which led to demise of around 70% of all terrestrial life, including all the non-avian dinosaurs.

Could Theropod Egg Shape Have Doomed the Dinosauria?

An Oviraptor (theropod) dinosaur sitting on her nest.

Picture credit: Everything Dinosaur

Egg Shape

One of the authors of this new paper, Dr Charles Deeming (School of Life Sciences, Lincoln University) explained:

“These results indicate that egg shape can be used to distinguish between different types of egg-laying vertebrates.  More importantly they suggest Mesozoic bird eggs differ significantly from modern day bird eggs, but more recently extinct Cenozoic birds do not.  This suggests that the range of egg shapes in modern birds had already been attained in the Cenozoic.”

Comparing Extinct and Extant Egg Shapes

As extant amniotic eggs vary considerably in size and shape and this variety reflects different patterns of egg formation and development, then the variation seen in the fossil record of eggs may also reflect different patterns of egg formation, egg development and even nesting behaviour.

Dr Deeming commented:

“From a biological perspective, it is self-evident that different egg shapes by birds, both past and present, might be associated with different nesting behaviours or incubation methods.  However, hardly any research has been carried out on this topic and fossil data are insufficient to draw firm conclusions.  We hope that future discoveries of associated fossil eggs and skeletons will help refine the general conclusions of this work.”

Other Factors to Consider

Although there might be a link between eggshell shape and the ability to survive the Cretaceous mass extinction, it is likely that a lot of other factors contributed to the survival of one group of vertebrates whilst others died out.  The eggshell shape itself may be a part of the story, but palaeontologists are confident that dinosaurs, including many theropod dinosaurs engaged in complex nesting behaviours, brooded eggs on nests and invested a great deal of time and effort in raising the next generation.

A spokesperson from Everything Dinosaur stated:

“Although the fossil record for eggs and nesting sites is extremely fragmentary, there is evidence to suggest that members of the Dinosauria exhibited altricial and precocial behaviours.  How one group of birds, the Neornithines were able to dominate the Aves remains uncertain, more research in this area is needed.  However, this data adds a fresh perspective and it is certainly intriguing.” 

Dr Deeming advised that this new paper does not provide all the answers, but it hints at the tantalising possibility that eggshell morphology could have been an contributory factor in the extinction of the dinosaurs.  Dr Deeming and this paper’s co-author Dr Marcello Ruta (Lincoln University), are continuing their investigations.  The scientists intend to explore how highly variable amounts of yolk (food for the embryo) and albumen (egg white) could possibly effect egg shape.

For models and replicas of prehistoric animals including dinosaurs: Dinosaur Models and Prehistoric Animal Figures.

Short Snouted Basal Ichthyosauriform from the Lower Triassic of China

It had long been predicted, but until now one of the enduring mysteries of the marine reptiles had remained unsolved.  One of the most successful clades of marine vertebrates ever to have existed were the ichthyosaurs , reptiles that form the Order Ichthyosauria (fish lizards), also known as the Ichthyopterygia (fish flippers).  These animals thrived in the seas and oceans for much of the Mesozoic but unlike other types of back-boned animals that had adapted to a life in water, no fossils of transitional forms showing a link with terrestrial ancestors had been found.

Ichthyosaur Origins

However, this week a team of researchers led by scientists from the University of California have published a paper detailing the discovery of an amphibious ichthyosaur, an animal that, although adapted to a life in the sea was still capable of clambering about on land.  This specimen is believed to represent a transitional form, between the Ichthyosauria and their terrestrial ancestors.

Writing in the science Journal “Nature”, the researchers document a nearly complete specimen (just the end of the tail is missing), of a forty-centimetre-long, amphibious reptile that is probably part of a group of animals that were the ancestors of the nektonic ichthyosaurs, widely regarded by many palaeontologists as the most well-adapted to a marine existence of all the reptiles.

The Fossil Specimen that Indicates a Transitional Form

Picture credit: University of California – Davis/Professor Motani

Commenting on the research, lead author Professor Ryosuke Motani (University of California, Department of Earth and Planetary Sciences) stated:

 “But now we have this fossil showing transition.  There’s nothing that prevents it from coming onto land.”

From Anhui Province

Professor Motani and his colleagues uncovered the fossil specimen in eastern China (Anhui Province) from Lower Triassic strata believed to date from around 248 million years ago (Olenikian faunal stage).  Unlike the long-snouted fully marine ichthyosaurs this animal, which has been named Cartorhynchus lenticarpus, had a short snout, its bones were also heavier, traits associated with fully terrestrial ancestors.

Cartorhynchus lenticarpus

Unlike later ichthyosaurs, the flippers were large in proportion to the body size and the wrists flexible.  These features helped this creature crawl around on land, in a similar way to extant seals.  C. lenticarpus means “truncated snout with flexible wrists”, an apt name for this little reptile that spent part of its life on land.  During the early part of the Triassic, eastern China was covered by a shallow tropical sea, there were numerous small islands, the whole area resembled the Caribbean today.  The isolated islands with their limited resources probably acted as a spur for vertebrate evolution.  There was plenty of food in the sea but it was a question of being able to reach it, this probably led to the evolution of reptiles that were more at home in water than their ancient ancestors.

The researchers also had to consider the implications of the Permian mass extinction event on the evolutionary pressures that these animals were under.  Just four million years earlier, planet Earth had undergone the most devastating extinction event known in the history of our planet.  More than 95% of all life on Earth died out.

A spokesperson from Everything Dinosaur explained:

“Extinction events mean the inevitable demise of many genera and families.  However, for those organisms able to survive, such events open up a whole range of new opportunities and often there is a “burst” of evolution as animals and plants adapt to take advantage of vacated niches and new resources.”

Scientific Collaboration

Collaborating with the University of California were scientists from the Chinese Academy of Sciences, Peking University, Anhui Geological Museum, the University of Milan, and the Field Museum (Chicago).  As a basal Ichthyosauriform has been discovered in China, and the most primitive true ichthyosaurs are also known from Triassic rocks from this region, then it is likely that the Ichthyosauria evolved in this part of the world.  This clade then radiated out and occupied a number of ecological niches including apex predatory positions before dying out in the Late Cretaceous.

Later ichthyosaurs were agile, swimmers, although the end of the tail is missing, scientists speculate that Cartorhynchus lenticarpus was probably a relatively poor swimmer.  It probably hunted soft bodied animals and arthropods in coastal waters.

For replicas and figures of ichthyosaurs and other marine reptiles: CollectA Age of Dinosaurs Popular Figures.