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Articles, features and information which have slightly more scientific content with an emphasis on palaeontology, such as updates on academic papers, published papers etc.

23 09, 2018

Chemical Clues to the Earliest Animal Fossils

By | September 23rd, 2018|Dinosaur and Prehistoric Animal News Stories, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Cholesterol Proves Dickinsonia was an Animal

A team of international scientists including researchers from the Australian National University (Canberra) and the Russian Academy of Sciences (Moscow), have finally solved one of the great puzzles in palaeontology.  They have detected molecules of cholesterol in an ancient fossil to confirm that the bizarre Dickinsonia, part of the enigmatic Ediacaran biota, was an animal and therefore distantly related to all other animals including humans.

A Fossil of Dickinsonia – A Bizarre Disc-like Organism But What Exactly Was It?

Dickinsonia costata fossil.

The Ediacaran fossil Dickinsonia costata, specimen P40135 from the collections of the South Australia Museum

Picture Credit: Fr Alex Liu (Cambridge University)

The Enigmatic Ediacaran Biota

Before the Cambrian explosion and the evolution of hard-bodied organisms, there existed a strange biota formed of bizarre, soft-bodied organisms that did not show much affinity to Late Cambrian fossil groups and to any form of living organisms today.  Fossils appear in sedimentary rock dated between 570 to 541 million years ago and have been found in Australia, (the Ediacara Hills of South Australia, from which this period in Earth’s history is named) and notably in Namibia, England, China, Canada and Russia.  They were the first complex multi-cellular organisms to appear on Earth.  Although the Ediacaran biota immediately preceded the rapid appearance and diversification of animals in the Cambrian, where these strange organisms fit within the tree of life remained a mystery.  Some of these fossils appear segmented and show some bilateral symmetry, Dickinsonia for example, but most lack any obvious signs of a gut, a mouth, an anus or any appendages that might link them to the Animalia.

This new study, published in the journal “Science”, identified biomarkers, specifically the fat, cholesterol in the fossilised remains of Dickinsonia.  This discovery confirms that at least one bizarre Ediacaran group, Dickinsonia and related taxa are members of the animal kingdom (Metazoa).

Finding Fossils Can Be Dangerous

Australian National University PhD student Ilya Bobrovskiy and his fellow collaborators in this research project, explored a remote area of exposed cliff on the White Sea coast of north-western Russia.  The field team were looking for strata laid down in the Ediacaran so that they could study any fossils preserved within the ancient rocks.  The sedimentary material they were interested in was exposed high up on a steep cliff face and ropes had to be used to get the field team down the cliff face so that they could dislodge sandstone boulders which fell to the beach below and then could be collected for further analysis.

Palaeontology Can Be a Dangerous Business – Dislodging Ancient Marine Sandstone Boulders From the Cliff Face

Extracting sandstone blocks from the cliff face.

Digging out huge blocks of sandstone to find Ediacaran fossils on the Russian White Sea coast.

Picture Credit: Australian National University

Dickinsonia – The Earliest Known Animal in the Geological Record

Some Dickinsonia fossils are a whopping 140 centimetres in length, indicating that these organisms were much bigger than most of the Ediacaran and later Cambrian biota, but where they fitted in the classification of life on Earth remained open to conjecture.  Previously, it had been suggested that these fossils represented giant, single-celled amoeba, lichens or dead-end evolutionary experiments that have no connection to other life forms.  The research team discovered a Dickinsonia fossil that was so well preserved that a molecular analysis revealed traces of tiny amounts of cholesterol, a type of fat that is only produced by animal life.  The scientists postulate that this is the conclusive evidence that confirms that Dickinsonia was an animal.

Cholesterol Found in Dickinsonia Proves it was an Animal

Dickinsonia fossil.

A beautifully preserved 558 million-year-old fossil of Dickinsonia, now classified as an animal (Metazoan).

Picture Credit: Australian National University

Co-author of the study, Associate Professor Jochen Brocks from the ANU Research School of Earth Sciences commented:

“The fossil fat molecules that we’ve found prove that animals were large and abundant 558 million years ago, millions of years earlier than previously thought.  Scientists have been fighting for more than 75 years over what Dickinsonia and other bizarre fossils of the Ediacaran biota were.  The fossil fat now confirms Dickinsonia as the oldest known animal fossil, solving a decades-old mystery that has been the Holy Grail of palaeontology.”

Preparing Fossil Specimens for Analysis

Searching for traces of organic materials such as fats in Dickinsonia.

Preparing a fossil specimen for the organic matter analysis.

Picture Credit: Australian National University

Molecular Analysis

Using extremely sensitive techniques to assess the chemical nature of fossil material has opened up whole new areas of study for palaeontologists.  Prior to the employment of such technologies as computerised tomography, synchrotron radiation light sources, biomarker analysis and four-dimensional scanning, palaeontologists were restricted to studying the shape and the form of fossils.  Today, palaeontologists can utilise these new methodologies, drawn from a variety of disciplines such as engineering and medicine to undertake complementary areas of study.

To read an article published in 2017 that postulated that Dickinsonia was a member of the Animal Kingdom and likely to be a Metazoan: Growth Analysis Suggests Dickinsonia was Definitely an Animal

17 09, 2018

Stay Small if you Want to Survive the Mesozoic

By | September 17th, 2018|Dinosaur and Prehistoric Animal News Stories, Main Page, Palaeontological articles|0 Comments

Tiny Fossils Reveal How Shrinking Was Essential for Successful Mammalian Evolution

Mammals and Dinosaurs may have shared a common reptilian ancestor, but these two tetrapod lineages diverged from one another a very long time ago.  However, mammals lived alongside the dinosaurs for many millions of years and a new study published in the academic journal “Nature”, suggests that staying small and inconspicuous was a key factor contributing to the evolution of mammals.  It was only after the extinction of the dinosaurs and other types of reptile, pterosaurs and marine reptiles, for example, that mammals were able to grow much larger.

Most Mammals Remained Small During the Mesozoic and Many were Probably Nocturnal

Purbeck (Dorset) 145 million years ago.

Purbeck Lagoon 145 million years ago, small placental mammals living alongside dinosaurs.  As darkness falls Durlstodon (top left) looks on whilst two Durlstotherium scurry through the undergrowth.  In the centre a Durlstotherium has been caught by Nuthetes destructor.

Picture Credit: Mark Witton

The Origins of Mammals

There are three types of mammals living today, there are the monotremes, the egg-laying mammals such as the platypus and the echidna, remnants of a once very widespread and diverse group of egg-laying mammals called the Australosphenida, that existed in the southern hemisphere for much of the Jurassic and Cretaceous.  Secondly, there are the pouched mammals, the marsupials, familiar creatures such as kangaroos, possums, koalas and such like.  Thirdly, there are the much more common and geographically widespread placental mammals (humans are a placental mammal).  The first true mammals such as the Late Triassic Eozostrodon, Megazostrodon and Morganucodon lived over 200 million years ago and a team of scientists from the United States and the UK have concluded that whilst the dinosaurs grew into giants, the ancestors of all modern mammals opted for a different strategy, they stayed small.

A Life Reconstruction of the Morganucodont Morganucodon of the Late Triassic

Staying small helped A model of the Late Triassic mammaliaform evolution during the Mesozoic.

A model of the Late Triassic mammaliaform Morganucodon.

Picture Credit: University of Birmingham

Getting to Grips with the Mammalian Jaw

The researchers used modern computer analysis to examine what happened to the skeleton of our tiny, shrew-like mammal ancestors.  Modern mammals have a unique lower jaw, consisting of a single bone that bears teeth (the dentary).  In contrast, other vertebrates have more complex lower jaws formed by several bones fused together.  In the course of the evolution of mammals, the complex jaws became simplified and a new jaw joint was formed, whilst some of bones that once formed the back of the jaws (the articular in the lower jaw and the quadrate in the back of the upper jaw), became much reduced in size, moving to the middle ear to evolve a role to aid hearing.

For an article that looks at the evolution of hearing in the mammaliaform and true mammals: Let’s Hear It For Mammalian Evolution

A Transitional Process

The scientists looked at how it was possible for the jaw to be restructured, whilst the animal was still able to feed and to hear.  X-ray computed tomography (CT scans) were employed to assess the skulls and jaws, computer models were then built to simulate the evolutionary process.  The team’s results showed that the small size of the fossil mammals significantly reduced the stresses in the jaw bones when feeding, while still being powerful enough to capture and bite through prey, such as insects.

Early Mammals were Small and Shrew-like

The Middle Jurassic mammaliaform (W. rex).

An illustration of Wareolestes rex.  An early mammaliaform that probably was nocturnal and insectivorous.

Picture Credit: Elsa Panciroli

Commenting on the study, lead author and lecturer at Birmingham University, Dr Stephan Lautenschlager stated:

“Our results provide a new explanation of how the mammalian jaw evolved over 200 million years ago.  Getting very small appears to have been crucial for our mammalian ancestors.  This allowed them to reduce the stresses in the jaw during feeding and made the restructuring of the jaw bones possible.”

Professor Emily Rayfield (Bristol University), who lead the study added:

“The evolution of the mammalian jaw joint has perplexed palaeontologists for over 50 years.  Using computational methods, we can offer explanations to how our mammalian ancestors were able to maintain a working jaw while co-opting bones into a complex sound detection system.  Our research is about testing ideas of what makes mammals unique among the animal kingdom, and how this may have come about.”

The scientific paper: “The Role of Miniaturisation in the Evolution of the Mammalian Jaw and Middle Ear” by Stephan Lautenschlager, Pamela Gill, Zhe-Xi Luo, Michael J. Fagan and Emily Rayfield published in the journal Nature.

Everything Dinosaur acknowledges the assistance of a press release from the University of Birmingham in the compilation of this article

5 09, 2018

Tracing the Origins of Biodiversity in the Animal Kingdom

By | September 5th, 2018|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Illuminating the Evolution of Animal Life – Humbling Thoughts

Recently two scientific papers have been published that delve deep into the origins of life on Earth.  In one paper, published in the “Proceedings of the National Academy of Sciences USA”,  the origins of animal body plans were explored, analysing the anatomical designs of animals, looking at how animal life half a billion years ago evolved and changed over time to bring us the biodiversity we see today and that which is preserved in the fossil record.  This study mapped shared characteristics and one of the conclusions drawn from the research was that all those weird and wonderful Cambrian creatures, as preserved in the Burgess Shales of British Columbia or in the Sirius Passet Lagerstätte of Greenland, are actually less weird than the butterflies and birds that you might see in your own garden.

The Body Plans of Bizarre Cambrian Creatures Such as Hallucigenia are not that Bizarre According to a New Study

A Hallucigenia specimen (Burgess Shale).

A Hallucigenia specimen (Royal Ontario Museum).  The red arrow is pointing towards a teardrop shaped object that might represent the fossilised remains of this strange creature’s head.

Picture Credit: Royal Ontario Museum/Dr Jean Bernard Caron with additional annotation by Everything Dinosaur

In the second scientific paper, which shares a number of authors with the first publication and was published last month in the journal “Nature: Ecology & Evolution”, researchers examined the evolution of all life as a whole, conducting research using a new molecular clock analysis to plot a unified timescale for the early evolution of life on our planet.

What is the Molecular Clock?

The idea of a molecular clock is based on the idea that evolutionary changes occur at regular time intervals, that the rate of genetic change (mutation), has remained constant over time.  The molecular clock uses this premise, it plots the number of differences in the genomes of two living species (for example a human and a bacterium) and these changes are proportional to the time since they shared a common ancestor.  Using this methodology, the scientists, from the universities of Bath and Bristol were able to avoid putting too much reliance on a very fragmentary and often highly controversial early life fossil record.   This research team concluded that the last universal common ancestor of cellular life existed more than 3.9 billion years ago and that the crown clades of two primary divisions of life – Eubacteria and Archaebacteria emerged less than 3.4 billion years ago.  Furthermore, the scientists concluded that modern eukaryotes (organisms whose cells have a nucleus enclosed within membranes – animals, protists, plants and fungi), don’t constitute a primary lineage of life and emerged relatively late during life on Earth’s evolutionary history (around <1.84 billion years ago).

Eukaryote Cell Compared to the Prokaryote Cell Typical of Eubacteria and Archaebacteria

Eukaryote Cell Compared to a Prokaryote Cell.

Simple diagram showing differences in eukaryote cells and prokaryote cells.  In a new study, scientists conclude that prokaryotes such as Eubacteria and Archaebacteria emerged less than 3.4 billion years ago whilst our branch of life on Earth, the eukaryotes emerged much more recently about 1.84 billion years ago.

Picture Credit: Everything Dinosaur

Did Animal Body Plans Emerge Over Deep Time or Come About in Response to Sudden Changes?

This was the question that the researchers set out to answer in the paper published the “Proceedings of the National Academy of Sciences USA”.  It is agreed that complex animal life evolved from single celled eukaryotes and that multi-cellular animals diversified into thirty or forty distinct anatomical body plans, but when and how did these body plans emerge?  Were the majority of these different body plans already in existence after the Cambrian explosion, some 500 million years ago?

To answer these questions the research team, consisting of scientists from Bristol University, Dartmouth College in New Hampshire and the University of West Georgia, looked at features from living groups of animals and cross-referenced those characteristics against what can be identified from the fossil record.

Professor Philip Donoghue (Bristol University) a co-author of both scientific papers explained:

“This allowed us to create a ‘shape space’ for animal body plans, quantifying their similarities and differences.  Our results show that fundamental evolutionary change was not limited to an early burst of evolutionary experimentation.  Animal designs have continued to evolve to the present day, not gradually as Darwin predicted, but in fits and starts, episodically through their evolutionary history.”

Mapping the Evolution of Different Types of Animal Body Plan

Mapping the evolution of animal body plans.

Grouping similar body plans and separating dissimilar body plans in the Animalia.

Picture Credit: Bristol University

The research team propose that major expansions in the type of animal following the Cambrian explosion aligns with other major ecological transitions such as the conquest of terrestrial environments.

Bradley Deline (University of West Georgia) added:

“Our results are important in that they highlight the patterns and pathways in which animal body plans evolved.  Many of the animals we are familiar with today are objectively bizarre compared with the Cambrian weird wonders.  Frankly, butterflies and birds are stranger than anything swimming in the ancient sea.”

Trying to Fit Extinct Animals into the Study

Contributors to both scientific papers, James Clark (Bristol University) and Mark Puttick (Milner Centre for Evolution, University of Bath), looked at how fossils could be incorporated into this research.

Dr Puttick stated:

“One of the problems we had is that our study is mostly based on living species and we needed to include fossils.  We solved the problem through a combination of analysing the fossils and using computer models of evolution.”

James Clark added:

“The fossils plot intermediate of their living relatives in shape space.  This means that the distinctiveness of living groups is a consequence of the extinction of their evolutionary intermediates. Therefore, animals appear different because of their history rather than unpreserved jumps in anatomy.”

Jenny Greenwood, also from the University of Bristol’s School of Earth Sciences, wanted to explore how this study might be reflected in the genomes of different organisms.  She wanted to work out which of the many proposed genetic mechanisms drove the evolution of animal body plans.

Jenny commented:

“We did this by collecting data on the different genomes, proteins, and regulatory genes, that living animal groups possess.  The differences in anatomical designs correlate with regulatory gene sets, but not the type or diversity of proteins.  This indicates that it is the evolution of genetic regulation of embryology that precipitated the evolution of animal biodiversity.”

These researchers have concluded that animal evolution has been permitted or driven by gene regulatory evolution.

Two Papers Helping to Improve our Understanding of the Evolution of Life on Earth

A fossil of an Trilobite.

A beautiful Trilobite fossil.  The two scientific papers each contribute to our understanding of the evolution of complex life on our planet.

Everything Dinosaur acknowledges the help of a press release from Bristol University in the compilation of this article.

The two scientific papers:

“Integrated Genomic and Fossil Evidence Illuminates Life’s Early Evolution and Eukaryote Origin” by Holly C. Betts, Mark N. Puttick, James W. Clark, Tom A. Williams, Philip C.J. Donoghue and Davide Pisani published in the journal Nature: Ecology & Evolution.

“Evolution of Metazoan Morphological Disparity” by B. Deline, J. Greenwood, J. Clark, M. Puttick, K. Peterson and P. Donoghue  published in the Proceedings of the National Academy of Sciences USA.

3 09, 2018

Marine Reptile Teeth Tell the Tale of Changing Seas

By | September 3rd, 2018|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

Study of Marine Reptile Teeth Hints at Faunal Turnover as Sea Levels Changed

New research undertaken by scientists at Edinburgh University in collaboration with colleagues at the University of Bristol, has revealed that marine faunal turnover during the Jurassic could well reflect what is likely to happen to apex marine predators today, as sea levels rise.  With global warming, so sea levels are likely to rise as ice sheets and glaciers melt.  This will have a significant impact on our planet, not least of all for our own species, but scientists are trying to predict the extent of the impact on changing sea levels on marine food chains and ecosystems.  Computer modelling can help, but surprisingly, so can studying the fossils of long extinct sea creatures.

Sea levels have risen and fallen on numerous occasions throughout deep geological time.  It really is a question of history repeating itself and the scientists writing in the academic journal “Nature: Ecology & Evolution”, report on the study of marine reptile teeth fossils from the Jurassic, which shed light on how reptiles adapted to major environmental changes and how these adaptations might provide a useful metaphor for extant marine life.

The researchers conclude that marine predators that lived in deep waters during the Jurassic Period, thrived as sea levels rose, whilst in contrast, those species that lived in shallower environments, such as near-coastal areas, became extinct.

A Jurassic Marine Ecosystem (Jurassic Sub-Boreal Seaway)

Life in the Jurassic seas.

A Jurassic marine ecosystem.  A life reconstruction based on fossils found in the Oxford Clay Formation (England).

Picture Credit: Nikolay Zverkov

The picture (above) depicts a marine ecosystem from the late Middle Jurassic (Callovian faunal stage).  A marine crocodile (metriorhynchid crocodyliform) avoids the attention of a large pliosaur attacking a plesiosaur, whilst sharks and a pair of giant, filter feeding Leedsichthys swim nearby.  A trio of ammonites can be seen (bottom right).

Marine Food Chains Unchanged for 15o Million Years

The study also indicates that the broad structure of food chains in today’s oceans have remained largely unchanged since the Middle Jurassic.  Naturally, the species are very different with mammals taking over the role once occupied by many types of extinct marine reptile, but the underlying structure of the food chain remains similar to what you would have seen had you been scuba diving in the shallow, tropical Jurassic Sub-Boreal Seaway some 160 million years ago.

For more than 18 million years, a very diverse, reptile-dominated megafauna co-existed in the Jurassic Sub-Boreal Seaway, a stretch of shallow water that covered present-day northern France to Yorkshire on England’s north-east coast.  By examining the shape and size of teeth spanning this 18-million-year period when sea levels fluctuated, the researchers found that species belonged to one of five groups based on their teeth, diet and which part of the ocean they inhabited.

Five Feeding Groups Identified Based on the Shape of Fossil Teeth

The fossil teeth were placed into one of five groups depending on their shape.  The shape of the tooth provides a guide to the feeding strategy of the animal and using this data plotted against rising and falling sea levels, the researchers were able to plot how the marine animal populations changed over time as sea levels fluctuated.

The five groups (referred to as feeding guilds), identified were:

  1. Pierce
  2. Generalist
  3. Cut
  4. Smash
  5. Crunch

One of the key findings of the study, was that those predators with fine, piercing teeth useful for grabbing fast-moving, slippery prey such as small fish and squid made up a substantial portion of the marine predator population around 165 million years ago (Callovian faunal stage), when sea levels were low and the water relatively shallow.  However, as sea levels rose and the sea became much deeper, the teeth of these types of predators were less common in younger rocks dating from around 150 million years ago (Tithonian faunal stage of the Late Jurassic).

Using Fossil Teeth to Map How Marine Apex Predator Populations Changed Over Time

Jurassic Sub-Boreal Seaway feeding guilds.

A study of fossil teeth identified five types of feeding guild in Jurassic seas.  The fossil finds were then plotted against data for changing sea levels to map how animal populations changed as the environment changed.

Picture Credit: Nature: Ecology & Evolution

The scientists concluded that the pattern that was identified is very similar to the food chain structure of modern oceans, where many different species are able to co-exist in the same area because they do not compete for the same resources.  Species used the resources in the environment differently and this permitted them to live together, this is termed niche partitioning.

Niche Partitioning

This niche partitioning enabled many species to co-exist.  Although a highly diverse fauna was present throughout the history of the Jurassic Sub-Boreal Seaway, as the scientists studied the teeth found at different stratigraphic levels they found that fish and squid eaters with piercing teeth declined over time while hard-object and large-prey specialists diversified, in concert with rising sea levels.

Larger species that inhabited deeper, open waters began to thrive.  These reptiles had broader teeth for crunching and cutting prey.  Deep-water species may have flourished as a result of major changes in ocean temperature and chemical make-up that also took place during the period, the researchers postulate.  This could have increased levels of nutrients and prey in deep waters, helping the species that lived there.  This research provides an analogy for modern ocean environments providing an insight into how species at the top of the marine food chain might respond to rising sea levels brought on by global climate change.

The Fate of Jurassic Predators May Well Provide an Analogy for Modern Marine Ecosystems

Marine crocodile (Plesiosuchus).

Marine crocodiles such as the large, broad-snouted Plesiosuchus manselii were apex predators specialising in hunting other marine reptiles.  These types of predator may have thrived as water depth increased, whereas, other smaller fish-eating marine crocodiles declined along with the long-necked plesiosaurs.

Picture Credit: Fabio Manucci/University of Edinburgh

The scientific paper: “The Long-term Ecology and Evolution of Marine Reptiles in a Jurassic Seaway” by Davide Foffa, Mark T. Young, Thomas L. Stubbs, Kyle G. Dexter  and Stephen L. Brusatte published in the journal Nature: Ecology and Evolution.

2 09, 2018

Jurassic Stem Mammal Bred Like a Reptile

By | September 2nd, 2018|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Scientists find Kayentatherium wellesi Fossil Along with Young

The Order Mammalia has a number of distinguishing characteristics when compared to the other vertebrates.  For example, mammals tend to have bigger brains and tend to produce some of the smallest numbers of offspring per litter.  Mammals evolved from reptiles and at some point in their evolutionary history, larger brains developed and smaller broods became the norm.  Scientists writing in the academic journal “Nature”, have published details of the discovery of the fossilised remains of a stem mammal, one that was found in association with thirty-eight babies.  The fossilised specimens might help palaeontologists to work out how mammals developed a different approach to reproduction when compared to their reptilian ancestors.

A Skeletal Reconstruction of the Probable Mother (Kayentatherium wellesi) and Offspring

Kayentatherium wellesi skeletal reconstruction (mother and offspring).

Offspring and a probable mother found in association (Kayentatherium wellesi).

Picture Credit: Eva Hoffman/The University of Texas at Austin

Kayentatherium wellesi

The fossils represent Kayentatherium wellesi, a cynodont, it was only as the specimen was being prepared that the researchers realised that this was an exceptional fossil.  The find of a 185 million-year-old K. wellesi with offspring are the only known fossils of baby stem mammals with what is believed to the mother.  The presence of so many offspring, probably only recently hatched from their eggs when they died, indicates that these types of stem mammal had litters more than twice the size of any living member of the Mammalia.  The size of the brood is akin to the breeding strategy of extant reptiles

Lead author of the study, Eva Hoffman (who studied the fossils whilst a graduate student at the University of Texas at Austin), commented:

“These babies are from a really important point in the evolutionary tree.  They had a lot of features similar to modern mammals, features that are relevant in understanding mammalian evolution.”

Hoffman co-authored the study with her graduate adviser, Jackson School Professor Timothy Rowe, who collected the specimen during fieldwork exploring the Early Jurassic sediments of the Kayenta Formation in Arizona, more than eighteen years ago.

Computerised tomography was used to reveal the bones inside the matrix back in 2011.  However, advances in CT-scanning finally permitted researchers at the University of Texas at Austin to reveal the babies, including complete skulls and partial postcranial material.

Advances in Computerised Technology Over the Last Seven Years Permitted the Fine Details of the Babies to be Discerned

Adult Kayentatherium skull with probable offspring.

Kayentatherium skull and images of the baby’s skulls indicating brood size.

Picture Credit: Eva Hoffman/The University of Texas at Austin

The Skulls of the Babies – The Same as the Adult’s Only Smaller

The highly detailed computer-generated images permitted the researchers to verify that the tiny bones were Kayentatherium wellesi, the same as the adult.  The analysis revealed that the skulls were scaled-down replicas of the adult, only ten percent the size of an adult skull, but otherwise proportional.  This contrasts with extant mammals, as their babies are born with shortened faces and large skulls to accommodate a big brain.  The brain of mammals is a very energy demanding organ, for example, in humans the brain needs more energy than any other organ of the body.  It has been estimated that the brains of human beings require around 20% of the total energy needed by our bodies each day.  Breeding and producing offspring also requires a lot of energy.  The discovery that Kayentatherium, a stem mammal, had a tiny brain and many babies, despite otherwise having much in common with extant mammals, suggests that a critical step in the evolution of the Mammalia was trading large litters for large brains.  This evolutionary change is therefore likely to have taken place more recently than 185 million-years-ago.

Professor Rowe explained:

“Just a few million years later, in mammals, they unquestionably had big brains and they unquestionably had a small litter size.”

Where does Kayentatherium Sit on the Mammalian Evolutionary Tree?

Kayentatherium was very probably endothermic (warm-blooded) and the skeleton shows a number of anatomical traits associated with modern mammals.

The Place of Kayentatherium on the Mammalian Family Tree

The evolution of modern mammals.

A simplified family tree showing mammalian evolution, the placement of Kayentatherium is shown in red.

Picture Credit: Eva Hoffman/The University of Texas at Austin

The mammalian approach to reproduction directly relates to our own species development (Homo sapiens), including the development of our own brains.  By looking back at our early mammalian ancestors, we can learn more about the evolutionary process that helped shaped the development of humans.

Professor Rowe added:

“There are additional deep stories on the evolution of development and the evolution of mammalian intelligence and behaviour and physiology that can be squeezed out of a remarkable fossil like this now that we have the technology to study it.”

The scientific paper: “Jurassic Stem Mammal Perinates and the Origin of Mammalian Reproduction and Growth by Eva A. Hoffman and Timothy B. Rowe published in Nature.

Everything Dinosaur acknowledges the assistance of a press release from the University of Texas at Austin in the compilation of this article.

 

1 09, 2018

Devon Fossil Links England with Russia

By | September 1st, 2018|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Kapes bentoni Saved by a Scan

The fossilised remains of a little reptile that roamed the land we now know as Devon has helped make links with the prehistoric vertebrate fauna of the Middle Triassic of Russia.  Thanks to the use of computerised tomography (CT) scans, palaeontologists have had the rare opportunity to study the skull and postcranial elements of a procolophonid reptile.  The fossil was found by co-author of the scientific paper, Dr Rob Coram of Swanage in November 2014, from a foreshore exposure of the Pennington Point Member of the Otter Sandstone Formation located close to the town of Sidmouth on the south Devon coast.  The Triassic sandstone deposits in these cliffs, which ironically form part of the famous UNESCO World Heritage site the “Jurassic Coast” contain vertebrate remains, but they are quite rare and often show signs of extensive weathering and transportation prior to burial and fossilisation.

The Fossil Specimen (BRSUG 29950-13) and Two Computer Generated Images

Kapes bentoni fossil and images of the fossil specimen.

Kapes bentoni fossil (top) and two images generated from the CT scans (BRSUG 29950-13).

Picture Credit: Bristol University/Papers in Palaeontology

Procolophonid Reptiles (Procolophonidae)

The reptile has been identified as an example of Kapes bentoni, several species are included in this genus, all of which, including the type species K. amaenus, which was named in 1975, come from Russia.  Procolophonids looked superficially like lizards, but they are not closely related to the Squamata.  They are parareptiles, which evolved in the Permian and had a wide distribution during the Triassic, before becoming extinct shortly before the Triassic came to an end.  When Dr Coram tried to clean and prepare the fossil, he found that the fossil material was too fragile and conventional preparation techniques would have resulted in permanent damage to the fossil bones.

Dr Coram commented:

“I tried everything I could.  I have had a lot of experience of removing rock from fossils using a fine needle and working under the microscope, but this was a nightmare.  When I touched it with a needle, small pieces of bone fell off.”

In order to allow the fossil to be studied, Dr Coram contacted colleagues at Bristol University and a CT scan of the small fossil was organised.  The job of interpreting the scans and the resulting computer generated images was given to PhD student Marta Zaher, who was at the Bristol University for a few months, normally she is based in Zagreb (Croatia).  The three-dimensional scans of the skull and postcranial material turned out to be far better than the scientists had hoped.  Even wear facets on the tiny teeth of the Kapes specimen could be discerned and studied.

Once all the scans had been compiled the researchers could examine the procolophonid fossil in great detail.  Most of the procolophonid fossils from England are highly fragmentary, but the scans revealed the presence of a skull, cervical vertebrae, the shoulder girdle, forelimbs and the front half of the torso.

An Illustration of the Skeleton of Kapes bentoni (Lateral and Dorsal Views)

Kapes bentoni skeletal reconstruction.

A skeletal reconstruction of Kapes bentoni. Fossil material from the Sidmouth specimen (BRSUG 29950-13) is shown in grey. Lateral view (A) and dorsal view (B).  Scale bar = 10 mm.

Picture Credit: Bristol University/Papers in Palaeontology

Spectacular CT Scans of a Triassic Specimen

Student Marta explained:

“The scans are amazing.  They show every detail of the tiny, five-centimetre (two inch) long skull.  You can see each tooth, and even the wear patterns.  Almost all the tiny bones of the palate and braincase are there.”

She added:

“This identifies the animal without question as a procolophonid.  These lived worldwide at the time, and they were important plant-eaters, with broad teeth fused to their jaws, and which wore down under grinding from the tough plant food.”

Several years ago, less complete specimens of the procolophonid had been found in the Devon rocks, and two academics then at the University of Bristol, Patrick Spencer and Glenn Storrs, had suggested the Devon animal was the same as Kapes from central Russia.

A spokesperson from Everything Dinosaur commented:

“Thanks to the use of computerised tomography, the researchers were able to get an unprecedented insight into the anatomy of an anapsid.  This non-destructive technique has helped scientists to identify that this Devon specimen is very closely related to other reptiles, fossils of which come from the terrestrial red beds of Russia.”

A Diagram of the Skull Produced from the CT Scan Data

Kapes bentoni skull illustration.

An illustration of the skull of Kapes bentoni recreated from the CT scans.  Scale bar = 10 mm.

Picture Credit: Bristol University/Papers in Palaeontology

Co-author of the scientific paper published in “Papers in Palaeontology”, Professor Mike Benton (Bristol University) stated:

“The new study confirms that the two animals are very close relatives, two species of the genus Kapes.  This is most unusual, to have evidence of a biogeographic connection over thousands of kilometres.  In the Middle Triassic, there was dry land in the UK and in Russia, but the area in between was filled with the Muschelkalk Sea, covering Germany and much of central Europe.”

Kapes bentoni

Many of the early procolophonids were insectivorous, however, Kapes bentoni was a plant-eater.  This idea is reinforced by the heavy wear on the teeth as observed in the CT scans from this study.  K. bentoni had a short, stocky body and it may have been fossorial (lived in a burrow).  The spines on the skull have provided the scientists with a bit of a puzzle.  It has been suggested that these spines had a defensive function, making the reptile seem bigger and more intimidating to a potential predator.  The spines would also have obstructed any predator attempting to swallow Kapes head-first.

A Life Reconstruction of the Procolophonid Kapes bentoni

Kapes bentoni illustrated.

An illustration of the procolophonid K. bentoni.

Picture Credit: Marta Zaher

The scientific paper: “The Middle Triassic Procolophonid Kapes bentoni: Computed Tomography of the Skull and Skeleton” by Marta Zaher, Robert A. Coram and Michael J. Benton published by Papers in Palaeontology.

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

25 08, 2018

Two New Chinese Dinosaurs Prove Handy

By | August 25th, 2018|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Plotting the Evolution of the Alvarezsauridae with Bannykus and Xiyunykus

A team of international scientists writing in the journal “Current Biology” have published details of two new Chinese alvarezsaurid dinosaurs that will help palaeontologists to better understand the evolution of this group of bizarre Theropods.  Some later genera becoming the  prehistoric equivalents of today’s aardvarks and anteaters.  The dinosaurs have been named Bannykus and Xiyunykus and their fossilised bones are proving handy, as palaeontologists seek to understand how the Alvarezsaurian dinosaurs reduced and lost most of their digits, except the thumb, which became very large and robust.  These sleek, fast-running and very bird-like dinosaurs seemed to have become very specialised over some ninety million years.

Two Newly Described Chinese Dinosaurs Help to Plug an Evolutionary Gap in the Alvarezsauridae

Chinese fossils shed light on the evolution of the specialised Alvarezsaurian monodactyl hand.

New alvarezsaurid fossils help to shed light on the evolution of the specialised alvarezsaurid hand.  Over millions of years the long forelimbs and three fingered hands evolved into the much reduced limbs with a single digit.

Picture Credit: Vikto Radermacher

The Alvarezsauroidea have a long history, basal forms such as Haplocheirus lived in Asia around 160 million years ago and the very last members of the Alvarezsauridae family were present in the Late Cretaceous, a temporal range of at least ninety million years.  The last of these bizarre, very bird-like dinosaurs have been classified into the sub-clade Parvicursorinae and these animals seem to have been very specialised insect eaters, with a strong single thumb digit with an oversized claw, powerful arm and chest muscles (although the length of the arm was much reduced), long snouts, with thin narrow jaws.  It has been speculated that these dinosaurs could rip apart the nests of termites or dig into logs to find insects.  It has even been suggested that they evolved a long tongue to help them lap up their prey in the same way that an extant anteater does.

The earliest alvarezsaurids were not insectivores, dinosaurs like Haplocheirus were probably hunters of small vertebrates.  Haplocheirus (H. sollers), had the teeth of a typical meat-eating Theropod and grasping hands to catch prey.  Only later alvarezsaurids had much reduced teeth and evolved a hand with a single, large curved thumb claw.

Digit Reduction in Tetrapods

The loss of fingers and toes has occurred numerous times amongst Tetrapods.  Perhaps the most famous example of all, is the evolution of the foot of the horse.  It was the notable American palaeontologist Charles Othniel Marsh, who plotted the evolution of equines by studying the toe bones of ancient horses.  Marsh was able to demonstrate how primitive horses gradually lost their toes evolving into the single-toed, fast running animal we know today.

To read more about the contribution of Marsh and the evolution of horses: The Contribution of Othniel Charles Marsh

Both Bannykus and the slightly smaller Xiyunykus are important because they show transitional steps in the process of Alvarezsaurs adapting to new diets.

Mapping the Evolutionary History of the Alvarezsauroidea

Alvarezsaurid evolution.

The discovery of two new Chinese alvarezsaurids helps to plug a seventy million year gap in the evolutionary history of the Alvarezsauroidea.

Picture Credit: Current Biology

The image (above) shows the temporal position of the two, newly described species.  Both Xiyunykus and Bannykus lived during the Early Cretaceous, their fossils are helping to bridge a seventy million year gap between Late Jurassic basal forms and the advanced and highly specialised Late Cretaceous forms.

Xiyunykus pengi

Xiyunykus was the first of these new dinosaurs to be discovered.  Its fossils were found in 2005, by an international expedition to the Junggar Basin (Xinjiang Uyghur Autonomous Region of north-western China).  The fossil remains consist of a partial, disarticulated skeleton and the material has been dated to the Barremian-Aptian faunal stages of the Early Cretaceous.  The researchers, including Xu Xing from the Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP) have estimated that this dinosaur weighed around fifteen kilograms.

Skeletal Remains of Xiyunykus pengi

Xiyunykus pengi fossils.

Xiyunykus pengi fossil material.  Picture A shows a skeletal outline (scale bar 10 cm), the known fossil material is shaded grey, whilst B, shows a cross-section through the fibula used to give an approximate age for the specimen.  Images C-N show various fossil elements used to identify and define the species.

Picture Credit: Current Biology

A cross-sectional analysis of lower leg bone (B) in the image above, indicates that this dinosaur was around nine years of age when it died and probably a sub-adult.  The genus name is from “Xiyu”, the Mandarin for denoting the western regions of Central Asia and from the Greek “onyx” meaning claw.  The trivial name honours Professor Peng Xiling, who has played a significant role in the study of the geology of this region.

 Bannykus wulatensis

The second alvarezsaurid was discovered in 2009 in western Inner Mongolia.  The fossils come from the Bayingobi Formation  (Aptian faunal stage of the Early Cretaceous).  Histological analysis of a cross-section of bone taken from the fibula indicates that this dinosaur was around eight years of age when it died. It, like the Xiyunykus specimen, was probably a sub-adult.

Skeletal Remains of Bannykus wulatensis

Bannykus wulatensis fossil material and skeletal drawing.

Skeletal remains and a limb bone cross-section with an accompanying line drawing of Bannykus (known fossils shaded grey).  Bannykus wulatensis shown as a skeletal drawing (A), note scale bar equals 10 cm, with (B) showing the cross-section of the fibula.  Images C-O represent elements of the fossil material.

Picture Credit: Current Biology

The genus name comes from the Mandarin “Ban” meaning half, a reference to the transitional anatomical features seen in this dinosaur and “onyx”, from the Greek for claw.  The trivial name refers to Wulatehouqi (Wulate Rear Banner), the county-level administrative division in which the type locality is situated.

Long Arms and Grasping Hands to Reduced Arms and Digits

These two newly described Alvarezsaurian dinosaurs have helped to determine that these peculiar Theropods very probably originated in Asia, before migrating to other parts of the world such as North and South America over their long evolutionary history. Bannykus and Xiyunykus are important because they show transitional steps in the process of Alvarezsaurs adapting to new ecological niches, Bannykus, which may have lived slightly later than Xiyunykus, is showing signs of that mechanically efficient forearm, a more robust and powerful upper arm and an enlarged thumb.

The Manus (Hand) of Bannykus Showing a Transitional Stage in Alvarezsaurid Evolution

Image of the fossil bones comprising the Bannykus hand.

A digital image of the fossil hand of Bannykus.  Note the larger thumb with proportionally bigger bones and a big claw (hypertrophied first digit).

Picture Credit: Current Biology

Still a Puzzling Group of Bird-like Dinosaurs

The discovery and scientific description of these new members of the Alvarezsauridae is very significant.  These fossils will help scientists to better understand the evolution of the specialised hand of alvarezsaurids and provide assistance when it comes to phylogenetic placement for group members.

Lead author of the scientific paper, Xu Xing commented on the evolutionary changes that had been highlighted stating:

“This transition plays out in an incremental fashion over more than 50 million years.  It could one day potentially serve as a classic example of macroevolution akin to the ‘horse series’ of North America.”

These dinosaurs are some of the more bizarre and peculiar forms of Theropod.  Ancestral forms seemed to have anatomical features quite typical of carnivorous dinosaurs, before evolving much more specialised forms, probably in response to exploiting a particular ecological niche.

Co-author James Clarke (George Washington University), added:

“The fossil record is the best source of information about how anatomical features evolve and like other classic examples of evolution such as the “horse series,” these dinosaurs show us how a lineage can make a major shift in its ecology over time.”

The Alvarezsaurian dinosaurs remain a puzzle.  They may have evolved into specialist insectivores, but they retained their long legs and the ability to run fast throughout their evolutionary history.  The forelimbs, hands and digits may have undergone a radical change, but these dinosaurs always seem to have remained quite graceful and agile animals.  Why these animals retained their ability to run very quickly when their prey was to be found in a termite mound or a rotting log is not clear.  However, it is likely, that the ability to run fast was continued to be selected for in this group as an adaptation to avoiding being eaten by larger predatory dinosaurs.

Palaeontologists Xu Xing and James Clarke Searching for Dinosaur Fossils

Scientists looking for alvarezsaurid fossils.

Xu Xing (IVPP) collecting fossils with James Clark (George Washington University).

Picture Credit: Xu Xing

The scientific paper: “Two Early Cretaceous Fossils Document Transitional Stages in Alvarezsaurian Dinosaur Evolution” by Xing Xu, Jonah Choiniere, Qingwei Tan, Roger B.J. Benson, James Clark, Corwin Sullivan, Qi Zhao, Shuo Wang, Hai Xing and Lin Tan published in Current Biology.

23 08, 2018

Turtle Evolution – Complicated

By | August 23rd, 2018|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Oldest Turtle with a Beak but No Shell – Eorhynchochelys sinensis

A beautifully preserved and very nearly complete fossilised skeleton of a turtle is helping scientists to unravel the evolutionary story of these ancient reptiles.  However, it seems that the evolution of turtles, tortoises and terrapins (the Order Testudines, sometimes referred to as the Chelonii), may be even more complicated than previously thought, just like a large terrapin in a small aquarium, the discovery of this new fossil, might just have muddied the water somewhat.

A Life Reconstruction of the Newly Described Late Triassic Turtle Eorhynchochelys sinensis

Eorhynchochelys sinensis life reconstruction.

A life reconstruction of Eorhynchochelys sinensis.

Picture Credit: Yu Chen (Institute of Vertebrate Palaeontology and Palaeoanthropology)

Early Turtle From the Late Triassic

The skeleton was excavated from Upper Triassic rocks in Guanling County, (Guizhou Province, south-west China).  It has been named Eorhynchochelys sinensis, the name means “dawn turtle with a beak from China”.  As the scientific name suggests, this is the oldest turtle ever found with a toothless beak.  Its discovery might help to close a gap in the evolutionary history of the Chelonii, as although it did not have a shell (the fossil lacks a carapace or plastron), the skull is very similar to the skull of extant turtles, but the rest of the animal’s skeleton resembles that of an earlier basal turtle that lived some ten million years previously.  Eorhynchochelys was over two metres long and it lived in an estuarine environment, it was most likely amphibious and the presence of strong claws and well-developed forelimbs suggests that this ancient animal may have lived in a burrow.

A View of the Fossil Material E. sinensis

Eorhynchochelys sinensis fossil - an early turtle without a shell.

Eorhynchochelys sinensis fossil (dorsal view).

Picture Credit: National Museums of Scotland

Mosaic Evolution

The researchers, which included scientists from the National Museums of Scotland, the Chicago Field Museum, the Canadian Museum of Nature and the Institute of Vertebrate Palaeontology and Palaeoanthropology in Beijing, were intrigued by the modern-looking turtle skull with its characteristic edentulous (toothless) beak.  This feature had not been seen in early fossil turtles before and the dating of  Eorhynchochelys indicates that this trait seems to have disappeared in some lineages and reappeared millions of years later.  This suggests that the evolutionary development of the Chelonii was much more complicated, after all, here was a Late Triassic ancestral turtle with a modern-looking skull but lacking a shell, although the broad, enlarged ribs and other anatomical features of the skeleton indicated that this type of reptile was on the way to evolving such a feature.

The fact that Eorhynchochelys developed a beak before other early turtles but didn’t have a shell is evidence of mosaic evolution, the idea that characteristics can evolve independently from each other and at a different rate and that not every ancestral species has the same combination of these traits.  All living turtles have both shells and toothless beaks, the evolutionary path that led to these traits was not a simple linear progression.  Some ancient turtles evolved partial shells, whilst others evolved beaks, eventually the genetic mutations and natural selection that allowed these traits to develop became unifying characteristics of the group as a whole.

A Life Reconstruction of the Head of Eorhynchochelys

Eorhynchochelys sinensis with its beak.

An illustration showing the head of Eorhynchochelys sinensis with its beak.

Picture Credit: Institute of Vertebrate Palaeontology and Palaeoanthropology

Family Links

Although the discovery of Eorhynchochelys sinensis helps to provide further information on the evolution of turtle traits, it does not resolve a long-standing argument about where in the Class Reptilia the Testudines (Chelonii), should be placed.  However and whenever these reptiles evolved their characteristic features might be complicated, but it seems that by around 210 million years ago, the turtle body plan with its carapace, plastron and beak had come about and this group have remained relatively unchanged since.  The Testudines seem to lack a feature that is common in most other reptiles, a pair of holes (fenestrae), in their skulls behind the eyes.  For many years, turtles were thought to be anapsids (members of the  Anapsidae), a very primitive subclass of the Reptilia.  Genetic studies have suggested that turtles, tortoises and terrapins are closely related to diapsid reptiles and their close relatives, Archosaurs such as crocodilians, dinosaurs and birds.  However, other studies have concluded that turtles and their kind might actually, be more closely related to snakes and lizards (Squamata).

Eorhynchochelys had a single pair of holes behind its eye sockets, this might suggest an anapsid origin or it might indicate that Eorhynchochelys is a transitional form that evolved from diapsid ancestors.

Commenting on the taxonomic position of the Chelonii in the light of this new Chinese fossil discovery, co-author of the research, Xiao-Chun Wu (Canadian Museum of Nature), explained that when the physical characteristics of Eorhynchochelys were considered in an analysis with other fossilised reptiles, it is likely that turtles are not closely related to either the Archosauria or the Squamata, but it is more likely that they are an offshoot from earlier, more primitive reptiles.

In the absence of more fossils, this debate is not going to be resolved anytime soon.

To read an article from 2013 looking at research into the evolution of Chelonians: How the Turtle Got Its Shell

For an article that discusses the discovery of Pappochelys rosinae a basal turtle that lived some 20 million years earlier than Eorhynchochelys, that has been classified as a diapsid but had the beginnings of a plastron: Pappochelys – The Grandfather of the Chelonii

22 08, 2018

A Challenge to the Aquatic Spinosaurus Theory

By | August 22nd, 2018|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

Was Spinosaurus aegyptiacus at Home in the Water?

New research utilising computer modelling to study the buoyancy of Spinosaurus (S. aegyptiacus) by Dr Donald Henderson of the Royal Tyrrell Museum (Alberta, Canada), challenges the idea that this sail-backed Theropod was adapted for a semi-aquatic way of life.  The research suggests that Spinosaurus could float and keep its head clear of the water to enable it to breathe, but other Theropods could also float in positions that enabled them to breathe freely, but with its pneumatised skeleton and system of air sacs, diving for food was probably beyond Spinosaurus, thus hindering its ability to be an effective semi-aquatic, pursuit predator.  Dr Henderson concludes that Spinosaurus may have been more at home wading through water, specialising in hunting along the shoreline or in shallow water, but still remaining a competent terrestrial predator.

Spinosaurus May Have Been a Shallow Water or Shoreline Predator

Spinosaurus

From paddler to swimming the “evolving” image of Spinosaurus.  New research proposes that Spinosaurus aegyptiacus was a shallow water predator and not capable of diving for its dinner.

Picture Credit: Everything Dinosaur/BBC

Challenging the 2014 Scientific Paper

Dr Henderson set about creating three-dimensional computer models of Spinosaurus and several other Theropods including Allosaurus, Coelophysis, the ornithomimid Struthiomimus, Tyrannosaurus rex and another member of the Spinosauridae family – Suchomimus tenerensis.  Dr Henderson, who is the Curator of Dinosaurs at the Royal Tyrrell Museum of Palaeontology, located in Drumheller, southern Alberta, wanted to test the hypothesis proposed by Dr Nizar Ibrahim and colleagues published in September 2014, that hypothesised that S. aegyptiacus was quadrupedal and a semi-aquatic dinosaur, a first for a member of the Theropoda.

To read Everything Dinosaur’s article about the 2014 scientific paper: Spinosaurus – Four Legs are Better than Two

Intriguingly, the interpretation of Spinosaurus, as proposed by Ibrahim et al, was used as the basis for the digital Spinosaurus model by the Royal Tyrrell Museum researcher.

Views of the Theropod Body Plans Used to Test Buoyancy

Digital models of Theropods used in floatation tests.

Theropod body plans used in the floatation tests, dorsal and lateral views.

Picture Credit: PeerJ/Dr Henderson (Royal Tyrrell Museum)

The picture above shows the digital body plans used to test the theoretical buoyancy of different types of Theropod dinosaur.

Key

A).  Coelophysis bauri

B).  Struthiomimus altus

C).  Allosaurus fragilis 

D).  Suchomimus tenerensis (Baryonyx tenerensis) – it has been suggested that Suchomimus and Baryonyx fossil material might represent the same genus (Holtz, 2012; Sues et al., 2002), this conclusion was used in this study.

E).  Spinosaurus aegyptiacus – the body plan based on the body shape proposed by Ibrahim et al in the 2014 paper.

F). Tyrannosaurus rex

Testing Buoyancy in Freshwater

To ensure that the digital models were able to replicate the orientation and depth of immersion in freshwater, Dr Henderson tested the software using a model of an alligator (A. mississippiensis).  Furthermore, he assessed the buoyancy of a computer generated model of an emperor penguin (Aptenodytes forsteri), which is also a member of the Theropoda.

Dr Henderson explained:

“Science is self-correcting.  Research is a competitive scientific process that continually generates new information and ideas, so here’s some of the self-correcting in action.”

Testing the Stability and Buoyancy of Spinosaurus (S. aegyptiacus)

Testing the buoyancy and stability of Spinosaurus.

Testing the stability and buoyancy of Spinosaurus in freshwater.

Picture Credit: PeerJ/Dr Henderson (Royal Tyrrell Museum)

Spinosaurus Could Float But So Could Other Theropods

Dr Henderson’s digital models demonstrated that Spinosaurus could indeed float with its head above water, enabling it to breathe freely.  However, the models of other Theropod dinosaurs demonstrated similar results.  This was not unexpected as most Tetrapods can successfully float and swim, the shape of Spinosaurus did not necessarily give it an advantage over the body shape of other dinosaurs when it came to stability in water.

Alligators Much Better Suited to Water Than Spinosaurus

The stability of a Spinosaurus in freshwater was also compared to the digital alligator. When tipped to the side, the alligator model returned to its original topside position.  Such behaviour is seen in semi-aquatic animals, they have the ability to right themselves when floating.  The Spinosaurus model did not perform well in the same tests.  When tilted, the model rolled over onto its side, demonstrating very little lateral stability in water.  The research implies that Spinosaurus would have easily tipped over and would have had to use its limbs constantly to maintain an upright posture in the water.

Based on the Digital Model Analysis Alligators Are Much Better Suited to an Aquatic Habit Than Spinosaurus

Alligator swimming.

An American alligator.

Picture Credit: Everything Dinosaur

Assessing the Centre of Mass

One of the key points of the 2014 paper, was that an anatomical study based on the known Spinosaurus fossil material (which represented numerous individuals of different sizes), indicated that this dinosaur walked on all fours.  In this new research, the centre of mass of the digital model of Spinosaurus was found to be close to the hips, similar to what is seen in other Theropods.  This contradicts the 2014 research, as Dr Ibrahim and his colleagues proposed that S. aegyptiacus had a centre of mass located towards the centre of the torso.  With the centre of mass located further forward, it suggests a quadrupedal form of locomotion, however, Dr Henderson’s research indicating a centre of mass positioned over the hips suggests that Spinosaurus could have walked around on land quite happily on just its hind legs (bipedal).

The Position of the Centre of Mass Would Affect Locomotion on Land

Different interpretations of Spinosaurus fossil material.

Different interpretations of the body plan of Spinosaurus.  The red asterisk suggests the centre of mass for each figure.

Picture Credit: Everything Dinosaur

Spinosaurus Probably Couldn’t Dive

Dr Henderson’s models also found Spinosaurus to be unsinkable.  Living aquatic birds, reptiles, and mammals all have the ability to submerge themselves to pursue their prey underwater. Although the bones of Spinosaurus might be more dense than other carnivorous dinosaurs, they still were substantially pneumatised.  This anatomical feature in conjunction with the air sac breathing system found in living Theropods (birds), probably made it very difficult, if not impossible, for this dinosaur to dive underwater in search of prey.

Dr Henderson concludes that this inability to dive, combined with a centre of mass close to the hips and a tendency to roll onto its side, suggests that Spinosaurus was not a specialised semi-aquatic predator after all.

He added:

“Spinosaurus may have been specialised for a shoreline or shallow water mode of life, but it would have still have been a competent terrestrial animal.”

However, as there are so very few Spinosaurus fossil bones to study, it is possible that this dinosaur lacked a significant number of avian style air sacs and pneumatised bones.  Even with an increased mass offered by a denser skeleton the digital model when “tweaked” in this way, still suggested that being able to submerge and go underwater would have been a considerable challenge.  Dr Henderson does concede that if it could be shown that the mass deficit represented by the lungs and air sacs was offset by the increased mass of a denser skeleton that might help the claim of a semi-aquatic Spinosaurus.

This is essentially, the central point of the Spinosaurus controversy.  This dinosaur did live in a habitat dominated by large bodies of water.  There were plenty of large fish around for an aquatic predator to eat, but in the absence of fossil evidence, the actual role of Spinosaurus in the North African Cretaceous ecosystem and its habits remain very much open to debate.

The scientific paper: “A Buoyancy, Balance and Stability Challenge to the Hypothesis of a Semi-aquatic Spinosaurus Stromer, 1915 (Dinosauria: Theropoda)” by Donald M. Henderson and published in the academic on-line journal PeerJ.

14 08, 2018

Toothy, Pterosaur Terror from the Saints and Sinners Quarry

By | August 14th, 2018|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

Caelestiventus hanseni – Rare Pterosaur Fossil Sheds Light on Triassic Pterosaur Diversity

A team of scientists have published a paper in the journal “Nature Ecology & Evolution”, detailing the discovery of a new type of Triassic pterosaur.  The exquisitely preserved fossils, including skull and jaw material excavated from strata laid down at a desert oasis that existed around 210 million years ago, has got vertebrate palaeontologists in a flap.  Firstly, only around thirty fossils of Triassic pterosaurs are known, most of these from only fragmentary remains and secondly, as this flying reptile fossil is associated with a desert environment, it suggests that by the Late Triassic the Pterosauria were very specious and had already adapted to a variety of different habitats.  If all this wasn’t enough to get scientists excited, the exceptional state of preservation has revealed anatomical features previously obscured in other early pterosaurs and shows that this new flying reptile from Utah, was closely related to Dimorphodon macronyx which is known from Lower Jurassic rocks from Dorset (southern England).

The flying reptile was large, very large for a Triassic Pterosaur, it had an estimated wingspan of 1.5 metres.  It has been named Caelestiventus hanseni (pronounced Sel-less-tees-vent-us han-son-eye).

A Life Restoration of the Newly Described Late Triassic Pterosaur Caelestiventus hanseni

Caelestiventus hanseni illustration.

Caelestiventus hanseni illustration. Study of the fossil bones suggests the presence of a throat pouch.

Picture Credit: Michael Skrepnick

From Saints and Sinners Quarry (Utah)

The fossils come from a vertebrate bone bed located in the Saints and Sinners Quarry, within sandstone deposits in north-eastern Utah.  Numerous vertebrate fossils have been associated with this locality including Crocodylomorphs and Theropod dinosaur material.  The bones come from silty, fine-grained sandstones laid down in near-shore waters of an oasis, that was surrounded by arid desert.  More than 18,000 individual bones representing a total of nine Tetrapod taxa (including two Theropod dinosaurs), have been found.  The flying reptile bones described in the scientific paper are the only ones known from this deposit and Caelestiventus hanseni is the first Triassic pterosaur from the western hemisphere from outside Greenland.  Whether this flying reptile was a resident of the oasis is unclear, but it is possible that this individual was an occasional visitor, to what would have been, an isolated oasis surrounded by extensive dune fields.

One of the Delicate Skull and Jaw Fossils Held by Professor Brooks Britt (Brigham Young University)

Holding fossils of Caelestiventus hanseni.

Professor Brooks Britt (Brigham Young University) holds one of the pterosaur fossils (jaw and skull fossils). His finger is pointing to roughly where the eye socket would have been.

Picture Credit: Brigham Young University

The picture above, shows a prepared piece of the fossilised skull of C. hanseni (maxilla and other elements from the jaws and skull), the specimen is held by Professor Brooks Britt of Brigham Young University and the lead author of the scientific paper.  It is not possible to remove the delicate, three-dimensional fossils from the matrix, the fossils would collapse under their own weight, but CT scans in conjunction with computer modelling enabled the production of precise plastic replicas of the fossil pieces, that gave the researchers the opportunity to reconstruct the skull.

Related to Dimorphodon (D. macronyx)

The beautiful state of preservation enabled the research team to gain fresh insights into the morphology of skull and jaws of Late Triassic pterosaurs.  The reconstructed brain case reveals that those parts of the brain responsible for processing vision were particularly well-developed, reinforcing the theory that flying reptiles had very keen eyesight.

A phylogenetic analysis undertaken by the researchers reveals that Caelestiventus is a sister taxon of Dimorphodon macronyx, which is known from Lower Jurassic rocks from Dorset.

A Three-Dimensionally Printed Skull of Caelestiventus hanseni

Line drawings and three dimensional model.

C. hanseni model skull and line drawing comparisons between C. hanseni and D. macronyx.

Picture Credit: Brigham Young University with additional annotation by Everything Dinosaur

The use of CT scans and computer software to digitally remove the fossils from their matrix without damaging them has enabled the scientists to produce extremely accurate three-dimensional images of the specimen, these data files can then be shared with other vertebrate specialists across the world.

A spokesperson from Everything Dinosaur commented:

“The scans permitted the production of finely detailed and extremely accurate three-dimensional models of the individual bones.  When these were fitted together this gave the scientists the opportunity to study the entire skull and to share this information very easily with other palaeontologists.  The use of technology is now helping scientists to gain much easier access to important fossil finds.”

The Geographical Significance of Caelestiventus hanseni

Not only is Caelestiventus hanseni the first record of a Triassic pterosaur from North America, the discovery suggests that by the Late Triassic, flying reptiles were not only quite large but also that they may have already adapted to a wide variety of habitats.  Similarly aged fossils from Greenland and Europe indicate pterosaurs living in forested areas and coastal environments on the super- continent of Pangaea.  This fossil discovery demonstrates that early pterosaurs were geographically widely distributed and ecologically diverse, even living in harsh desert environments.  C. hanseni is the only record of a desert-dwelling, non-pterodactyloid pterosaur and predates all known desert living pterosaurs by more than sixty-five million years.

The Geographical Significance of the Utah Pterosaur Fossil Discovery

The geographical location of the pterosaur find.

The location of the Triassic pterosaur find from Utah plotted against a map of Pangaea during the Late Triassic and other pterosaur fossil discoveries from Triassic strata.

Picture Credit: Brigham Young University

The picture above shows (top left), the location of Utah in the United States and (insert), the geological formations associated with north-western Utah.  The world map shows the location of Triassic pterosaur fossil discoveries superimposed on an illustration of Pangaea with a colour key to indicate different habitats.  Caelestiventus is the first Triassic pterosaur identified from a desert environment.

The genus name is from the Latin for “heavenly wind”, in recognition of the volant capabilities of this reptile.  The trivial name honours geologist Robin L. Hanson of the Bureau of Land Management, who has played a crucial role in the excavation of the Saints and Sinners Quarry material.

Photographs Showing Some of the Fossil Material Associated with the Caelestiventus Genus

Caelestiventus hanseni fossil material.

Views of the Pterosaur fossil material – Caelestiventus hanseni.

Picture Credit: Brigham Young University

To read Everything Dinosaur’s 2015 article that first broke the news of this Pterosaur fossil discovery: Fearsomely-fanged Triassic Pterosaur from Utah

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