Category: Palaeontological articles

Did Boy Stegosaurs have Bigger Plates than the Girls?

Evidence for Sexual Dimorphism in the Stegosaurs

Show most five year olds, a picture of a Stegosaurus and the chances are they will be able to name it.  The plated plant-eater with its small head, stout limbs and its tail spikes is one of the most recognisable of all the dinosaurs.  However, palaeontologists still know remarkably very little about this Late Jurassic herbivore.  A new paper, written by a researcher from Bristol University and published in the on line academic journal PLoS One (public library of science), suggests that the shape and size of those famous back plates varied between the males and females.  If the researcher’s conclusions are correct, male Stegosaurs had back plates that were more rounded and up to 45% bigger than the females.

One of the Best Loved but Not that Well Understood Dinosaurs

Still lots to learn about this Ornithischian dinosaur.

Still lots to learn about this Ornithischian dinosaur.

Picture Credit: Everything Dinosaur

In Everything Dinosaur’s annual survey of popular prehistoric animals, Stegosaurus is nearly always recorded in the top five.  It seems most popular with girls.  In this new research, University of Bristol MSc student Evan Saitta proposes that skeletal evidence from a bone bed in central Montana referred to as quarry JRDI 5ES, suggests sexual dimorphism in a Stegosaur species known as S. mjosi.  Evan spent a total of six summers working as part of a field team from Princeton University (New Jersey), excavating the Stegosaurus fossils as part of his undergraduate thesis.

To view the results of Everything Dinosaur’s most recent prehistoric animal survey: Top Ten Prehistoric Animals of 2014 (Part 1)

The top five in our most recent survey can be found here: Top Five Most Popular Prehistoric Animals of 2014

Professor Michael Benton, Director of the Masters in Palaeobiology at Bristol University commented:

“Its very impressive when an undergraduate makes such a major scientific discovery.”

This is certainly true, but let’s not get too carried away for the moment at least.  Take for example the species name Stegosaurus mjosi, there is some uncertainty whether the fossils represent a Stegosaurus.  About thirty years ago, palaeontologists discovered the fossilised remains of a large Stegosaur during field work on the oldest part of the Morrison Formation exposed in Montana.  This dinosaur was formally named in 2001 as Hesperosaurus mjosi.  Although there have been many fossils found, including an almost complete skull, it is still debated whether these fossils represent a distinct Stegosaur genus or a species of Stegosaurus.  The strata from which the fossils come from has been estimated to be around 155 million years old, it has been suggested that Hesperosaurus mjosi, or if you prefer the junior synonym Stegosaurus mjosi, is a basal member of the Stegosaur family.  Its exact phylogenetic place in the Stegosaur family tree remains controversial.

However, this issue does not detract from the research carried out into the shape and size of the plates.  The dig site known as JRDI 5ES, as it is one of the sites managed by the Judith River Dinosaur Institute, provides a fascinating and tantalising glimpse into the lives of these large, Late Jurassic plated dinosaurs.  The site contains the remains of at least five individuals preserved in mudstone.  Although two distinct types of plates can be observed, the rest of the bones indicate that this group of Stegosaurs represent a single species.  The bones, although disarticulated for the most part, are found within the same stratigraphic horizon and they were probably not transported very far prior to burial.  This is indicated by the presence of many smaller bones such as unguals and skull elements as well as a lack of wear on the bones from transportation.  The absence of shed crocodilian and Theropod teeth indicate that the corpses were not scavenged and so burial must have been quite rapid.  It could be inferred that this was a group of Stegosaurs that died together, could this species of Stegosaur have lived in social groups?  Does this suggest Stegosaur co-existence?

Suggested Silhouettes of a Male and Female

Females may have had reduced plates that were more spiky.

Females may have had reduced plates that were more spiky.

Picture Credit: Evan Saitta (additional annotation by Everything Dinosaur)

Detailed measurements and quantitative analysis indicated that there were two distinct types of plates present.  Of the fairly complete plates found within the bone bed, four could be described as large and wide, whilst five more could be classified as being taller and more spiky in appearance.  These are distinct characteristics and what is more, Mr Saitta’s analysis suggests that there are no plates present that show traits of both wide and spiky characters.

Evan commented:

“Simply looking at them by eye, you can identify two varieties.  But then you can also measure them and do a more quantitative analysis and demonstrate that, yes, there are two distinct varieties of plates, and that there don’t appear to be any clear-cut intermediates.”

Two Distinct Plate Morphologies have been Described

The widest plate morph compared to the tallest plate morph (scale = 10cm)

The widest plate morph compared to the tallest plate morph (scale = 10cm)

Picture Credit: PLoS One

The plate shapes suggest sexual dimorphism in Stegosaurs, males and females evolved different shaped plates.  But which is which?  The Bristol based scientist cannot say for sure whether the males or the females had the broader, larger plates however he speculates that the boys had the bigger more rounded plates.

“We know from modern animals that males typically invest more into their ornaments than do the females.  In this case, the broader variety reaches sizes 45% larger in surface area than do the tall plates.  And I argue that these wide plates would create a great ‘billboard’ for male Stegosaurs if they were using them to attract a mate.”

If the fossils represent a single species, then sexual dimorphism seems the “best fit” for an explanation.  Analysis of the fossil material indicates that the animals were fully grown and so the shape of the plates cannot be put down to dinosaurs at different stages of growth.  Plates from all positions on the body can be classified as being of the rounded or taller shape so the variation cannot be due to the location of the plate on the animal.  Other isolated Stegosaur fossils found in Wyoming and ascribed to the same genus/species support the idea of sexual dimorphism in plate shape as these specimens too show only one plate shape.

Evan Saitta Cutting a Thin Section of Stegosaur Plate for Ontogenetic Analysis

Evan Saitta prepares a section of plate for cross-sectional study.

Evan Saitta prepares a section of plate for cross-sectional study.

Picture Credit: Judith River Dinosaur Institute

A spokesperson from Everything Dinosaur commented:

“This is a remarkable study.  We made one of our “palaeontological predictions” that 2015 would bring Stegosaurus into the limelight once more and this new research provides tantalising evidence of sexual dimorphism in Ornithischian dinosaurs.  We can speculate that the plates evolved as defensive armour or possible temperature regulators and over countless generations of females selecting mates with the most impressive plates, two distinct sets of plates formed in the species.  At first glance the spiky, taller plates associated with the females may have offered better defence against predator attack.  The more rounded plates ascribed to the males may not have been as effective.  The male Stegosaurs sacrificing some defensive capability in order to have a more impressive visual display to woo a female.  Although sexual dimorphism is not common in extant reptiles and birds, there are examples seen today.  For instance, the male peacock has sacrificed the ability to camouflage itself from predators by evolving a very obvious, huge tail feather display, all for the purpose of attracting a mate.”

Female peacocks may have influenced the tail length and plumage of the males by selecting males in the peacock population that had slightly longer tails and more flamboyant plumage. These traits are then passed onto offspring and this form of sexual selection by females leads to more ornate tail feathers in males as they have an advantage in terms of mating success.  It could be inferred that sexual selection by female Stegosaurs led to the evolution of larger, broader plates on the backs of the males.  The bigger more rounded plates providing the males with an advantage when it comes to mating, despite being less helpful when it came to fending off an attack from a Theropod.

The conclusions from this study are likely to be debated for a very long time.  This new paper provides a new “angle” on the purposes of those enigmatic plates and further research into “Sophie” the Stegosaurus stenops specimen at the Natural History Museum in London may help to “round off” the debate.

To read more about “Sophie” the Stegosaurus specimen exhibited at the Natural History Museum: All about “Sophie”

To see the list of Everything Dinosaur’s “palaeontology predictions” for 2015: Palaeontology and Fossil Predictions for 2015

Dinosaur Nest Site Vandalised

Vandals Destroy Dinosaur Nests and Footprints

Everything Dinosaur has received press reports that vandals have smashed a number of dinosaur eggs and footprints that made up part of an outdoor display at the Mirador del Cretáceo dig site  in Coll de Nargó, Catalonia (north-eastern Spain).  The tourist attraction was opened in 2005 and combines a serious palaeontological study of Upper Cretaceous highly fossiliferous sediments with a tourist attraction, which permits onlookers to walk round the site and to view some of the fossil specimens in situ as well as other exhibits that show how dinosaurs nested.

Some of the items believed to have been smashed include dinosaur eggs that had been reassembled from the fossil remains to give the impression that they had just been laid.

Sites containing dinosaur egg remains and evidence of nesting behaviour are extremely rare and the dig site in the Pyrénéen village is believed to represent the largest location of its kind yet discovered in Europe.  In addition, the fossils are very well preserved and these in conjunction with the numerous dinosaur footprints that have been mapped in the area indicate the presence of at least six different types of dinosaur present in this Late Cretaceous ecosystem.

One of the Fossilised Eggs Preserved at the Site

An important Late Cretaceous dig site.

An important Late Cretaceous dig site.

Picture Credit: (Xavier Delclòs, Faculty of Geology UB)

Sadly, this is not the only example of vandalism reported upon by Everything Dinosaur, back in 2012, team members from Everything Dinosaur published an article about an act of dinosaur vandalism in Alberta, Canada.

To read more about this incident: Hooligans smash duck-billed dinosaur fossils

More recently, a Sauropod bone at the Dinosaur Monument in Utah was broken and a piece stolen, this theft and the damage to that part of the bone that remained led to the specimen having to be removed.

Salvador Moyà, the manager at the Palaeolithic Institute of Catalunya (ICP) called the destruction of the fossils “inconceivable” and the mayor of Coll de Nargó, Senor Benito Fité stated that this was a “catastrophe”.

These incidents are all to frequent, especially at sites which are relatively open and allow public access.  Back in 2013, the site was raided by a local resident and several specimens stolen.  These were only returned when it became public knowledge that whoever was responsible for the theft would face prosecution for their criminal action.

Those Highly Adaptable Humans

Research Suggests that H. sapiens Adapted Quickly to Different Environments

If the onset of a period of deforestation resulting from climate change provided the stimulus for the evolution and development of that part of the Homo genus that would eventually give rise to our own species H. sapiens, then how did our species cope when encountering extensively forested habitats?  The answer according to new research conducted by scientists from Oxford University, Sri Lanka and the University of Bradford is that our big-brained ancestors coped remarkably well.

Writing in the on line edition of the academic journal “Science” the research team report on carbon and oxygen isotope analysis carried out on the teeth of twenty-six individuals whose remains are associated with archaeological sites in Sri Lanka that date from the Pleistocene into the Holocene Epochs.  The isotope analysis provides evidence of human diet and it seems that humans as far back as 20,000 years ago were obtaining a significant proportion of their food requirements from the rainforest.

Early Homo sapiens – Made their Home in the Forest

Some early humans made the rainforest their home.

Some early humans made the rainforest their home.

Tropical rainforest environments are nutritionally poor and their dark and often treacherous interiors are difficult to navigate.  They would have represented challenging environments for human hunter/gatherers and up until now they had been little concrete evidence presented to suggest human habitation of rainforest environments prior to the advent of the Holocene, some 10,000 years ago.  This new study suggests that humans were exploiting rainforests for food, rather than more open habitats at least 20,000 years ago and in the scientific paper, the research team postulate that our species could have been making a home in tropical forests perhaps as far back as 45,000 years ago.  Previous archaeological research provides “tantalising hints” that humans could have been occupying rainforest ecosystems back in the Late Pleistocene (Late Tarantian stage), although it is not clear whether these early rainforest inhabitants were seasonal visitors or whether they permanently occupied the forests.   The research represents a collaborative effort between Britain-based scientists and their counterparts from Sri Lanka (The Institute of Archaeology and the Department of Archaeology, both based in Colombo).

Commenting on the research findings, co-author Professor Julia Lee-Thorp (Oxford University) stated:

“The isotopic methodology applied in our study has already been successfully used to study how primates, including African great apes, adapt to their forest environment.  However, this is the first time scientists have investigated ancient human fossils in a tropical forest context to see how our earliest ancestors survived in such a habitat.”

If the “Out of Africa” theory of H. sapiens evolution is accepted, then it is from Africa that modern humans migrated, this migration eventually leading to the colonisation of the rest of the world.  Fossils found in south-west Asia, Jordan for example, indicate a complex pattern of human and Neanderthal migrations most likely driven by climate change.  From around 60,000 years ago, modern humans moved eastwards across Asia into India, south-east Asia and eventually into Australia.  This migration may have taken as little as fifteen thousand years.

The scientists examined the fossilised teeth of humans from three archaeological sites in Sri Lanka, which are today surrounded by rainforest or more open terrain.  The isotope analysis revealed that all of the humans in the study had a diet sourced from slightly open, “intermediate rainforest” environments, only two individuals showed signs of a diet mainly sourced from an open grassland habitat.  However, the teeth that showed the “grassland signature” were dated to around 1,000 B.C. (Late Bronze Age to Early Iron Age), some of the youngest teeth used in the study.

Early Humans Exploited Different Environments

A Prehistoric Scene

A Prehistoric Scene

This new research supports the notion of just how adaptable early, modern humans were.  Back in 2011, Everything Dinosaur published an article about a remarkable discovery in East Timor that suggests as early as 40,000 years ago humans were catching Tuna.

To read this article: Prehistoric Fisherman Able to Catch Fast Swimming Tuna

Lead author of the scientific paper, Patrick Roberts (Oxford University) explained:

“This is the first study to directly test how much early human forest foragers depended on the rainforest for their diet.  The results are significant in showing that early humans in Sri Lanka were able to live almost entirely on food found in the rainforest without the need to move into other environments.  Our earliest human ancestors were clearly able to successfully adapt to extreme environments.”

The rapid spread of our species across the globe after the initial out of Africa migration does seem to support the idea that early H. sapiens were extremely adaptable, although they are not the only member of the Homo genus to have made the rainforest their home.  Homo erectus,  was the first widespread hominin species.  Fossils have been found in China and Indonesia.  It is very likely that H. erectus also adapted to forested regions.  In addition, the mysterious Homo floresiensis, fossils of which come from the remote Indonesian island of Flores was very well adapted to its mostly forested island home.  H. floresiensis may have survived to 13,000 years ago, but islanders talk of stories of strange little people living in the forest from much more recent times, perhaps until just a few hundred years ago.

The Very Complicated Human Family Tree

New Research and New Discoveries Shed Light on our Ancestry

If anyone has had an opportunity to trace their family tree, then they know that given the wealth of data around today, a few clicks of the keyboard can provide a great deal of information about your family.  However, when it comes to tracing the origins of the “human family”, the evolution of our own species, then things are much more tricky.  New research published today in the journal “Nature” is helping to unravel the complicated journey that hominins have taken, a journey that eventually saw the emergence of our species, Homo sapiens sometime around 220,000 years ago.

Using a fossilised very human-like partial jawbone found at Ledi-Geraru, (Ethiopia), which has been dated to around 2.8 million years ago, in addition with already described material, an international team of scientists have reconstructed the skull of the early hominin Homo habilis (handy man) and looked at the ancestry of this species.  The research team included scientists from the University College London, in collaboration with the National Museums of Tanzania and the Max Planck Institute for Evolutionary Anthropology (Leipzig, Germany).  This new research helps to establish the human lineage and to determine what makes H. habilis so distinctive from the early Australopithecines such as the famous “Lucy” fossil –  A. afarensis which ironically, was discovered not too far from where the 2.8 million year old hominin lower jaw was found.  However, the fossils of “Lucy” are much older.  The partial skeleton of “Lucy” has been dated to around 3.2 million years ago.

To read more about an exhibition that features the remarkable preserved remains of “Lucy”: Pictures from an Exhibition

The first fossils of “handy man”, Homo habilis were described in 1964.  They consisted of a distorted lower jaw, hand bones and a highly fragmented braincase, all representing the bones of a single individual.  These fossils were catalogued as Olduvai hominin (OH7).   The rarity of early human bones, along with the very distorted remains associated with the earliest evidence of H. habilis made determining the unique characteristics and features of this species extremely difficult.  However, this research team utilised state-of-the-art computerised tomography and sophisticated computer modelling to unscramble the distorted remains and to piece together a reconstruction of the skull and jaws of Homo habilis.

The question that has puzzled palaeoanthropologists since the scientific description of Homo habilis and the subsequent discovery of more Australopithecine fossil remains was, could the likes of “Lucy” have evolved into the very first human-like creatures? Professor Brian Villmoare (University of Nevada), believes that the discovery of this 2.8 million year old jaw bone, complete with five teeth helps to confirm this hypothesis.

The Fossilised Jaw Bone (2.8 million years old)

Something for the palaeoanthropologists to get their teeth into.

Something for the palaeoanthropologists to get their teeth into.

Picture Credit: Brian Villmoare (University of Nevada)

The problem is this, the fossil record between the time period when “Lucy” and her kin were alive and the emergence of Homo erectus (with its relatively large brain and human-like body proportions), some two million years ago, is extremely sparse.  What has been found, is also very fragmentary, making tracing evolutionary links difficult.  The ancient human-like jawbone is highly significant.  The molar teeth are much smaller and less robust than those of other hominins known from the fossil record.  It is the size of the jaws and the teeth wherein that helps scientists to distinguish more human-like species from those which are more ape-like.

Commenting on the significance of this fossil find, scientists have stated that this new discovery pushes back the human evolutionary line by some 400,000 years or so.  The fossilised jawbone with its mix of primitive and more advanced traits makes it a candidate for a transitional species between the Australopithecines and the human family tree.

The Digital Reconstruction of the Skull and Jaws of Homo Habilis

The digitally mapped and reconstructed skull of H. habilis.

The digitally mapped and reconstructed skull of H. habilis.

Picture Credit: University College London

The “handy man” fossil material having undergone its computer modelling reveals new information about the jaw shape.  The computer having reassembled the distorted jaw described in 1964, to provide a more accurate reflection of the living bone.  The research published in “Nature” suggests that Homo habilis has older evolutionary roots than previously thought.  This research supports the idea that many different types of Homo species existed in Africa between 2.1 and 1.6 million years ago.  Climate change, leading to a much drier, deforested habitat may have led to a spurt in evolutionary experimentation as species adapted to the new environment and exploited new niches in the changing ecosystem.  The modelled lower jaw reveals primitive traits such as seen in Australopithecine fossil material, but it also has more advanced features, distinguishing H. habilis from its contemporary Homo rudolfensis.

The potential transitional link between hominins and Australopithecines remained elusive until the University of Nevada discovery of the 2.8 million year old jawbone.  The fossil, known as LD 350-1 is an excellent candidate for the ancestor of Homo habilis and other early hominins.

 Commenting on the fossil jawbone discovery, Dr. Villmoare stated:

“LD 350-1 reveals that many of the anatomical patterns we see in two million year old Homo were established much earlier in the evolution of the genus.  At 2.8 million years ago we see relatively evolved Homo traits in combination with other, much more primitive anatomical features, a result that is particularly interesting in light of the shape of the OH7 reconstruction.”

New Ichthyosaurus Species Honours Mary Anning

Dorset to Doncaster – New Species of Ichthyosaurus Described

It might be one of the best known of all the genera of Mesozoic marine reptiles, but the Ichthyosaurus genus has been becalmed in terms of new additions to the species list.  That is, until a remarkable discovery in the fossil collection of the Doncaster Museum and Art Gallery led to the naming of a new species.  Ichthyosaurus anningae, the first “new” Ichthyosaurus for 127 years.  A paper describing this new species is due to be published in the prestigious academic publication “The Journal of Vertebrate Paleontology” and it is great to see that the trivial name honours Dorset fossil collector Mary Anning, it was Mary along with her brother Joseph, who found the first Ichthyosaurus fossils to be scientifically studied (1811).

The First New Species of Ichthyosaurus to be Described Since the 19th Century

Dolphin-like prehistoric animals.

Dolphin-like prehistoric marine reptiles.

The fossil, representing a sub-adult specimen, had resided in the collection of the Doncaster Museum and Art Gallery since it had been acquired sometime in the early 1980′s.   It was excavated from Lower Jurassic strata of West Dorset, but we at Everything Dinosaur, are unable to provide further information as to who exactly discovered it.  The fossil is believed to have come from the Lower Pliensbachian Stonebarrow Marl Member (Charmouth Mudstone Formation), which forms part of the geology of southern England’s famous “Jurassic Coast”.  The specimen, which measures around 1.5 metres in length is nearly complete, there is a beautifully preserved skull, much of the front portion of the body including ribs and preserved stomach contents.  The assigned holotype (DONMG:1983.98) had been mislabelled as a plaster cast replica.  Team members at Everything Dinosaur recall seeing the image of the fossil used to help promote children’s holiday activities at the Museum, it emphasises the importance of regional museums and their collections.  There are probably a significant number of new species awaiting discovery, not in the cliffs of Monmouth Beach, Lyme Regis, but in the draws and cabinets of museums.

Newest Ichthyosaurus on the Block (I. anningae)

A new species of Ichthyosaurus.

A new species of Ichthyosaurus.

Picture Credit: Dean Lomax and Judy Massare

This is not the first time that a new Mesozoic species has been identified from a museum collection.  Back in 2007, Everything Dinosaur wrote about the discovery made by then PhD student Mike Taylor at the Natural History Museum (London), which led to the naming of a new species of Sauropod dinosaur.

To read the article: How to Find a New Dinosaur – Look in a Museum

Dean Lomax, Honorary Scientist at The University of Manchester, examined the specimen in 2008.  He noticed a number of anatomical differences between this specimen and other types of Ichthyosaur.  Working with Professor Judy Massare (Brockport College, New York), Dean spent over five  years comparing and contrasting the Doncaster Ichthyosaur that had been nicknamed “Fizzy” with other museum specimens from around the world.  Unusual features in the humerus and femur (upper limb bones) along with the humerus length to femur ratio led him to believe that the Doncaster fossil represented something not seen before.  Over 1,000 other Ichthyosaurus fossils were examined during the course of the research, a further four fossils (three most likely of juveniles), were identified as having the same anatomical features as “Fizzy”.

Dean commented:

“After examining the specimen extensively, both Professor Massare and I identified several unusual features of the limb bones that were completely different to any other Ichthyosaur known.  That became very exciting.  After examining over a thousand specimens we found four others with the same features as the Doncaster fossil.”

Professor Massare has worked on a number of Ichthyosaur specimens, most notably a remarkable fossil found in Wyoming.  She used her knowledge of Ichthyosaur anatomy and locomotion to compare and contrast the fossil material.  The strata from which this fossil was extracted dates from the Early Jurassic (Lower Jurassic - Hettangian/Sinemurian–Pliensbachian).  It has been estimated that this fossil material is around 189 million years old. (Pliensbachian faunal stage).  Most Ichthyosaur fossils that date from this stage of the Jurassic are fragmentary, very few articulated specimens with cranial material are known.  The Doncaster fossil is the most complete Ichthyosaur fossil that dates from this time interval.

The upper arm bone (humerus) is short and robust.  The femur (thigh bone), in comparison is very much smaller.  The morphology of the fossil specimens ascribed to this new species, suggest that there were differences in the limb bones of males and females.  Such differences have not been identified before in Ichthyosaurs.  The species name pays tribute to Mary Anning (1799-1847), it was Mary along with other family members who found the fossils of the first scientifically described “fish lizard”.  The very first formal, academic paper describing an Ichthyosaur was published in 1814, the study being based on fossil material found in the Lyme Regis area by the Anning family.  Last year, Everything Dinosaur wrote a short article commemorating the 200th anniversary of this event.

To view this article: Two Hundred Years of Ichthyosaurs

Dean explained:

“Mary worked tirelessly to bring Ichthyosaurs, among other fossils, to the attention of the scientific world.  It is an honour to name a new species, but to name it after somebody who is intertwined with such an important role in helping to sculpt the science of palaeontology, especially in Britain, it is something that I’m very proud of.  In fact, one of the specimens in our study was even found by Mary herself!  Science is awesome.”

It has been a very busy couple of years for Dean, as well as helping to increase our understanding of British marine reptiles, in 2014, his book “Dinosaurs of the British Isles”, co-authored with Nobumichi Tamura was published.  This book provides a comprehensive account of the dinosaur fossils associated with the British Isles and we at Everything Dinosaur strongly recommend it to anyone with an interest in dinosaurs.

“Dinosaurs of the British Isles” – A First, Comprehensive Account of British Dinosauria

A comprehensive guide to British dinosaurs over 400 pages.

A comprehensive guide to British dinosaurs over 400 pages.

Picture Credit: Siri Scientific Press

For more details about the book and to order a copy: Dinosaurs of the British Isles Available Here

This new specimen, helps palaeontologists to understand in greater detail the evolution and radiation of the Ichthyosauria.  I. anningae adds to the number of Ichthyosaurus known from the Pliensbachian faunal stage.  There has now been recorded at least three species (possibly as many as five species) from this time interval.  This is significant, as the discovery of this new species falls between two of the three known major radiations of Ichthyosaur genera.  The numbers and types of Ichthyosaur seemed to have increased around 200 million years ago (Triassic/Jurassic boundary) – Neoichthyosaurian radiation.  A second major radiation occurred around 175 million years ago (Aalenian faunal stage), the Ophthalomosaurid radiation, when many new kinds of “fish lizard” also evolved.

Widespread Ecological Diversity Amongst Early Mammals

Tree-dwellers and Burrowers – Early Mammals More Diverse than Previously Thought

Fossils of two mouse-sized, mammals from China, indicate that some of the earliest known mammaliaforms (extinct relatives of modern mammals), had already diversified and become highly adapted to different ecological niches.  A joint Chinese/U.S. scientific team reporting in the academic journal “Science” discuss the implications for mammalian evolution and describe two new early mammals, one that was arboreal (tree dwelling) and fed on insects and tree sap, the other, a mole-like creature that probably spent much of its life underground.

The tree dweller, named Agilodocodon scansorius lived around 165 million years ago, the subterranean creature called Docofossor brachydactylus was discovered preserved in slightly younger strata, it burrowed underground whilst dinosaurs roamed overhead some 160 million years ago.  Both these creatures are Middle Jurassic Docodonts, an extinct Order of early proto-mammals.

The discovery of these two very different fur covered animals further supports the theory that just like modern-day mammals, Jurassic forms were highly adaptable and early mammals diversified to take advantage of a large range of ecological habitats.

Agilodocodon scansorius – Artists Impression and Skeleton Reconstruction

Early arboreal mammal from north-eastern China.

Early arboreal mammal from north-eastern China.

Picture Credit: University of Chicago (illustration by April Neander)

Commenting on the significance of these fossil finds, Dr. Zhe-Xi Luo (University of Chicago’s Department of Organism Biology and Anatomy), who co-authored the scientific papers stated:

“Before the turn of this century, it was generally thought that Mesozoic mammals could not diversify much in the dinosaur dominated ecosystem.  But fossil discoveries in recent years have built up a different picture.  In the last ten to fifteen years palaeontologists have found many Mesozoic mammals with very interesting functional and ecological specialisations.”

The research team that studied these fossils, was made up of scientists from the Beijing Museum of Natural History and the University of Chicago.  They conclude that Docodonts adapted to a very broad range of environments such as arboreal and subterranean habitats, despite competition from the Dinosauria, other reptiles and early birds.  Agilodocodon was a small, swift  animal with limb and finger bone dimensions that are comparable to modern tree dwelling mammals.  Study co-author David Grossnickle, a graduate student at Chicago University emphasised that it was amazing to see arboreal adaptations occurring so early in the evolutionary history of mammals.  He reflected that this research suggests that some extinct mammalian relatives exploited evolutionarily significant niches, long before true mammals.

An Artists Impression  and Skeleton Reconstruction of Docofossor brachydactylus

Ancient mole-like animal.

Ancient mole-like animal.

Picture Credit: University of Chicago (illustration by April Neander)

The Agilodocodon fossil material came from the Ningcheng County of Inner Mongolia, whilst the Docofossor material came from Hebei Province of China, to the south-east.  Docofossor lived around 160 million years ago. It lived in burrows on shores of  lakes and fed on worms and insects in the soil.  This small creature had reduced bone segments in its fingers, leading to shortened but wide digits, perfect adaptations for digging.  African Golden Moles possess almost the exact same adaptation.  This characteristic is due to the fusing of bone joints during embryonic development.  With African Golden Moles, the development of the digits is influenced by the genes GDF-5 and BMP.  As the extinct Docofossor has a very similar anatomy, the research team conclude that this genetic mechanism may have played a comparable role in early mammal evolution.

Mammals from the Middle Jurassic were once thought to have a very limited ecological footprint, only occupying a few niches in the food web.  However, these two new fossil discoveries along with early finds studied by the Chinese team, fossils such as Castorocauda, a fish-eating, swimming Docodont described back in 2006, provide strong evidence that early mammals adapted to a very wide range of environments.

The Phylogenetic Relationship Between Docodonts, Early Mammals and Extant Mammalia

Examining the phylogeny of early mammaliaforms.

Examining the phylogeny of early mammaliaforms.

Picture Credit: University of Chicago (illustration by April Neander)

Although not closely related to modern placental mammals such as our own species, the Docodonts are revealing themselves to have been a highly successful and very adaptable group of warm-blooded creatures.  It is the mammalian trait of being very adaptable that many scientists believe was key to them becoming the dominant megafauna after the demise of the Dinosauria, Pterosauria and marine reptiles.  It seems this adaptability runs deep in the mammal family tree.

Everything Dinosaur acknowledges the help of the University of Chicago in the compilation of this article.

To read another article that explores the diverse fauna of the Middle Jurassic strata of China: The Amazing and Diverse Daohugou Biota

Fossil Hunting Down Under

Local Fossil Hunters Get the Chance to Work with Professionals

On Sunday 22nd February amateur fossil hunters will get the chance to visit one of the state of Victoria’s most important fossil sites and get advice from leading palaeontologists.  Museum Victoria is holding a special event at the historic Beaumaris Bay fossil site.  The sandstone cliffs preserve evidence of marine fauna from Australia’s prehistoric past.  Many types of shark teeth have been discovered along with the fossilised bones of a number of marine vertebrates.

The day will involve talks from professional fossil hunters Dr Erich Fitzgerald (Museum Victoria), Professor Tim Flannery and Professor John Buckeridge of RMIT University (Melbourne).  Local amateur fossil hunters will also have the chance to have their finds identified by these experts.

Local Fossil Collectors and Professional Scientists Working Together in Beaumaris Bay

Fossil site has open day.

Fossil site has open day.

Picture Credit: David Hastie/Museum Victoria

Commenting on the special, interactive day dedicated to fossil collecting, Dr Erich Fitzgerald (Senior Curator of Vertebrate Palaeontology, Museum Victoria) stated:

“There is simply no better place to find fossils in Melbourne than Beaumaris.  They have helped us paint a rich portrait of what Victoria was like millions of years ago.  The abundance of fossils of large marine animals, especially sharks and whales, suggests that between 6 and 5 million years ago the coastal waters of Victoria were far richer in nutrients than they are today.”

But fossil hunting is not just for professional scientists, as most professional scientists are happy to admit.  Fossils are being eroded out of the sandstone cliffs all the time and if it was not for the dedicated community of local fossil hunters, many potentially significant finds could be severely abraided by wave action or lost all together before a professional palaeontologist got the chance to explore the area.

Dr. Fitzgerald added:

“In Museum Victoria’s collection there are thousands of stunning fossils from Beaumaris, many collected by enthusiastic members of the public with a keen interest in palaeontology.  The public can provide an extremely valuable insight from their fossil discoveries, which would potentially not have been uncovered otherwise.”

Back in 2012, Everything Dinosaur reported on the discovery of a fossilised leg bone found in the Beaumaris Bay area that was identified as belonging to a new genus of “toothed” marine bird.

To read more about this discovery: Giant “Toothed” Birds Once Soared over Southern Australia

With such a huge country to explore, Everything Dinosaur has predicted on numerous occasions that this continent will provide palaeontologists with a number of new fossil discoveries, even new types of dinosaur.  Members of the public who participate in sensible, careful fossil hunting and who are sensitive to the environment and wish to work within the fossil hunting code can make a huge contribution to the Earth sciences.

Everything Dinosaur acknowledges the support of Museum Victoria in the preparation of this article.

Strange Hominin Fossils From China – A New Species?

Hominin Fossils from Northern China Could be a New Species

A new study of fossilised teeth and jaw fragments found in a cave back in 1976, suggests the possibility of an unknown species of human living in northern China between 120,000 and 60,000 years ago.  A paper published in the American Journal of Physical Anthropology concludes that the teeth have similarities with Homo neanderthalensis and the much older hominid species H. erectus.

The research was carried out by a team of scientists from Beijing’s Institute of Vertebrate Palaeontology and Palaeoanthropology in conjunction with anthropologists from the National Research Centre on Human Evolution (Burgos, Spain).  The fossils represent the remains of four individuals and the teeth do not resemble those of modern humans.  Instead, they possess a range of primitive and more derived features, this could indicate a new species, yet to be described or possibly a hybrid hominid, a result of interbreeding between two already described species.  The fossils were found in a cave close to the village of  Xujiayao, Yanggao County in Northern China.  The site is approximately 120 miles west of Beijing.

María Martinón-Torres (National Research Centre on Human Evolution), explained that the research team examined the size and shape of the tooth crowns and their associated root system, the groves, cusps and crests.  These features were then compared to over five thousand fossil teeth representing nearly all the known hominin species.  The features of teeth are diagnostic when it comes to determining species and phylogenetic relationships.

The Xujiayao Fossil Teeth Compared to a Modern Human

The Xujiayao cave teeth (left) are compared to a modern human (right).

The Xujiayao cave teeth (left) are compared to a modern human (right).

Picture Credit: Dr. Martinón-Torres with additional annotation from Everything Dinosaur

Dr. Martinón-Torres, a specialist in ancient hominin dentition stated:

“Teeth are like landscapes in miniature.  Each of those slopes, grooves and valleys define a pattern or combination of features that can be distinctive of a population.”

Although a number of palaeoanthropologists have challenged the team’s results and all agree that more fossil material from ancient Asian hominins is required so that a more complete picture can be built up, this study does raise the possibility that there may have been an as yet, unknown species of human living in northern China as recently as sixty thousand years ago.

Given the size of Asia and its relative remoteness thanks to foreboding geological features such as the Ural mountains and the Himalayas, it is not surprising that isolated pockets of early hominins could have evolved distinct characteristics.  Or indeed, given the harsh environment and tough lives of these ancient humans it is not entirely surprising that interbreeding did occur between closely related species that overlapped territories.  Team members at Everything Dinosaur predict that more hominin fossils will be found in Asia that further complicate the relationships between the various recognised species.

Back in 2012, Everything Dinosaur reported on a study of human fossil remains found in south China that could represent a new species of hominin.  These ancient humans were nicknamed the “Red Deer People” and they lived much more recently than the Xujiayao hominins.  The research was carried out by scientists from the University of New South Wales and one of the researchers involved in this earlier study, Darren Curnoe, supports the idea of the Xujiayao fossils being a separate species.  He stated that although the sample was small, the unique characteristics of the teeth did suggest that a new species had been found.

The Associate Professor commented:

“It strongly suggests the presence of a previously unrecognised species.  There’s little doubt in my mind that these teeth stand out as something unique.”

To read more about the research into China’s “Red Deer People”:  Stone Age Remains from Southern China Might Represent Entirely New Human Species

Most palaeoanthropologists accept that from the Middle to the early Late Pleistocene Epoch, a time interval that spans from about 340,000 years ago to 90,000 years ago, Neanderthals occupied Europe and western Asia.  Anatomically modern humans were present in Africa, but the paucity of fossil material prevents scientists from describing the hominin populations of most of Asia.  Furthermore, the evolutionary interaction between eastern populations of hominins and those from Europe and Africa remains poorly understood.  The Xujiayao teeth sample expands the variability for early Late Pleistocene hominin fossils and also suggest that a primitive early human lineage may have survived into the Late Pleistocene in northern China.

Casting Doubts on Global Firestorms

Extraterrestrial Impact May Not Have Caused Global Firestorms

The debate over the consequences of the extraterrestrial impact that took place around sixty-six million years ago continues with the publication of pioneering new research that investigates whether or not the Yucatan impact caused extensive firestorms on a global scale.  It is now widely believed that at least one huge object from outer space crashed into Earth which very probably contributed to the mass extinction event that marks the end of the Cretaceous.  This is perhaps the most famous of all the mass extinction events recorded in the Phanerozoic fossil record, as no significant quantities of dinosaur fossils are found in younger strata.  The end Cretaceous mass extinction event saw the demise of the Dinosauria, the Pterosaurs, most of the marine reptiles and a number of other significant casualties.  It had been thought  that a consequence of the impact was a series of huge fires that ravaged the Earth, destroying much of the plant-life on the planet.  Plenty of evidence for this catastrophic event has been cited, for example, large amounts of carbon preserved in strata at the K-T boundary, believed to be the preserved remains of such conflagrations.

In 2013, for example Everything Dinosaur published an article on this blog citing research which suggested that intense heat in the atmosphere did indeed cause huge fires: Cretaceous Mass Extinction Study Provides Evidence of Global Firestorm

Scientists have also recorded evidence of a “fern spike” that occurred immediately after the extinction event.  Large numbers of fossilised fern spores have been recorded (microfossils), in contrast to a very low level of other plant remains such as pollen from flowering plants being recorded.  Ferns are quick to re-colonise an area after a devastating volcanic eruption.  The “fern spike” data was taken as supporting evidence for the massive destruction of much of the planet’s green matter.

To read more about the “fern spike” research: Humble Ferns – Evidence to Support the Impact Theory

Did the Extraterrestrial Impact Cause Global Firestorms?

Cataclysmic impact event.

Cataclysmic impact event, but was there a global firestorm?

Picture Credit: Don Davis commissioned by NASA

However, a team of UK based researchers (University of Exeter, Imperial College London and the University of Edinburgh), have challenged the idea of world-wide fires.  The scientists recreated the massive energy released from the impact event and they found that the blistering heat near the impact site was too short-lived to ignite living plants.  The scientists conducted a series of experiments using pulses of heat and writing in the Journal of the Geological Society, the team conclude that close to the actual impact, the heat wave would have lasted less than a minute, too short a time to set fire to living plants.  However, using computer models they discovered that the effects of the blast would have been felt as far away as New Zealand, some 12,000 kilometres from the site of the explosion.  The further away from the blast centre, the less intent the heat wave, but it would have been longer lasting.  In New Zealand, the heat blast would have lasted for around seven minutes, long enough to ignite living plant material.

Experiments conducted suggest that dry and dead plant matter could be set alight, but live plants such as conifer needles were not ignited.

Having a Blast with Heat Wave Experiments

Global firestorm study.

Global firestorm study.

Picture Credit: University of Exeter

The picture above shows the fire propagation apparatus recreating the impact induced thermal pulse at the Cretaceous/Palaeogene (K-T boundary).  Halogen lamps are delivering the intense, thermal radiation.

Commenting on the study, Dr. Claire Belcher (Earth System Science group in Geography at the University of Exeter) stated:

“By combining computer simulations of the impact with methods from engineering we have been able to recreate the enormous heat of the impact in the laboratory.  This has shown us that the heat was more likely to severely affect ecosystems a long distance away, such that forests in New Zealand would have had more chance of suffering major wildfires than forests in North America that were close to the impact.  This flips our understanding of the effects of the impact on its head and means that palaeontologists may need to look for new clues from fossils found a long way from the impact to better understand the mass extinction event.”

Fauna and flora populations are generally resistant to localised fire events, animals can hide or hibernate/enter aestivation and the seeds of plants can survive the intense heat of forest fires.  Some plants even rely on seasonal fires to help them spread.  Based on these assumptions, it can be suggested that wildfires on their own are unlikely to be directly responsible for extinctions.  However, large dinosaurs which were unable to run very far, or shelter may have suffered terribly from such fires.

Dr Rory Hadden from the University of Edinburgh added:

“This is a truly exciting piece of inter-disciplinary research.  By working together engineers and geoscientists have tackled a complex, long-standing problem in a novel way.  This has allowed a step forward in the debate surrounding the end Cretaceous impact and will help geoscientists interpret the fossil record and evaluate potential future impacts.  In addition, the methods we developed in the laboratory for this research have driven new developments in our current understanding of how materials behave in fires particularly at the wildland-urban-interface, meaning that we have been able to answer questions relating to both ancient mass extinctions at the same time as developing understanding of the impact of wildfires in urban areas today.”

Everything Dinosaur would like to thank Exeter University for the use of a press release that enabled this article to be compiled.

Dinosaurs – Going through the Motions

Fossilised Dinosaur Wee and Poo Mapped In Brazil

A lot can be learned from the skulls, teeth and jaws of prehistoric animals.  However, what goes in one end has to come out the other.  Quite exactly how the dinosaurs voided their digestive tracts (went to the toilet), remains a mystery, but a pair of scientists based in Brazil have mapped the fossilised excreta associated with a number of Mesozoic formations in that South American country.  The research has just been published in the “Journal of South American Earth Sciences”.

So let’s get down and dirty with the Dinosauria.  Many people might be aware that fossilised faeces are called coprolites.  The word coprolite comes from ancient Greek, it means “dung stone” from the words kopros for dung and lithos for stone.  We suspect that rather less people are aware that trace fossils believed to represent displaced sediment as a result of a stream of urine coming from a vertebrate are referred to as urolites.  The word urolite is also derived from the Greek.  Uro meaning urine and lithos for stone.

The Joy of Studying Coprolites

"Shiny side up" the joys of "dino dung".

“Shiny side up” the joys of “dino dung”.

Picture Credit: Everything Dinosaur

Back in 2004, the two scientists responsible for this latest research paper, Marcelo Adorna Fernandes (University of São Carlos), and Paul Roberto Figueiredo Souto (University of Rio de Janeiro), published a ground-breaking study (no pun intended) into trace fossils believed to be represent the disturbance caused in sand when a stream of urine hits that spot.  These traces of animal behaviour were preserved as fossils and so scientists had the opportunity to study the patterns made from splashes of urine.  The urolite fossils studied in 2004 and also examined in this latest paper, come from Cretaceous sandstone deposits of São Paulo State, in south-eastern Brazil (Botucatu Formation).  They have been found in association with the fossilised footprints of two different types of dinosaurs, a meat-eating Theropod and an Ornithopod.  It is not known which type of dinosaur created the urolites.

Studies of Urolites and Experiments to Recreate Sediment Redistribution

Study into the trace fossils made by the elimination of water from ancient creature's bodies.

Study into the trace fossils made by the elimination of water from ancient creature’s bodies.

The Society of Brazilian Palaeontology (2004)

The above photographs show three trace fossils that are believed to correspond to liquid wastes (A,B and C).  Photograph D shows an excavation created by dropping two litres of water from a height of eighty centimetres as the scientists experimented to try to recreate the impressions.  In all of the photographs the scale bar is in centimetres.

One of the reasons why scientists believe that the dinosaurs came to dominate life in the Mesozoic is that they were very efficient at retaining moisture inside their bodies compared to other types of terrestrial vertebrates .  Most types of birds excrete very little water with their faeces.  In fact, the way in which birds and reptiles deal with processing waste products, particularly those wastes and toxins associated with protein digestion, differs from the way that mammals handle the problem of expelling waste.

Ammonia, a by product of protein digestion, is toxic, it has to be got rid of.  Mammals convert ammonia in the body into a concentrated form (urea), this is expelled as urine, but it means we lose water.  Reptiles and birds tackle the problem of getting rid of ammonia in a slightly different way.  These other types of amniotes convert the ammonia into uric acid, which is much less toxic than urea.  It therefore does not need to be diluted with water to such an extent.  Indeed, uric acid does not need to mix with any water at all, it can be excreted as a semi-solid and thus, a lot of water can be conserved in this way.

The internal plumbing of birds and reptiles also varies.  Crocodiles and some types of Ratite, such as the Ostrich, can expel urine and faeces separately, the urine first followed by the solids (usually).  Most birds and most reptiles tend to expel what liquid they wish to get rid of as well as any solids at the same time.  Kind of a “one flush system” as we call it.  The mystery about dinosaur waste elimination is this – did the Dinosauria expel urine and faeces separately like ostriches and crocodiles or were they to a “one flush system”?

Perhaps different types of dinosaur expelled waste in different ways.  Ostriches for example, can store their urine in a urodeum, an organ similar in function to the mammalian bladder.  The solid waste is stored in another organ called a coprodeum, this is eliminated subsequently to the urine expulsion.  Observations of Ostriches spending a penny as it were, shows that they produce a strong jet of urine that hits the ground with quite a force. They create similar patterns in unconsolidated soil as seen in the trace fossils found in the Botucatu Formation (pictures A, B and C above).

So why bother to map the places in Brazil where coprolites and urolites are found?  These fossils provide important evidence to palaeontologists. They help scientists build up a picture of the diet of vertebrates and evidence of plant remains as well as depositional data can provide information about the palaeoclimates.  For example, the sandstones of the Botucatu Formation where the urolites were found, represent a dune environment interspersed with oasis and wadis.   In this latest research paper, coprolites from Upper Cretaceous as well as potential Jurassic aged deposits have been mapped.  This all helps to extend our knowledge with regards to the Gondwana biota during the Mesozoic.

Putting Brazil’s Coprolites and Urolites on the Map

The location of coprolite and urolite fossil specimens included within the 2014 study.

The location of coprolite and urolite fossil specimens included within the 2014 study.

Picture Credit: Journal of South America Earth Sciences/annotation by Everything Dinosaur

This area of research is often overlooked.  There is a lot we do not know about the Dinosauria.  Take for example the Late Cretaceous Hadrosaurine dinosaur Maiasaura (Maiasaura peeblesorum).  The Two Medicine Formation of Montana provided an extraordinary amount of evidence about this Ornithopod and its nesting behaviour.  The fossil deposit location was referred to as “egg mountain”, as these sediments preserved evidence of huge nesting colonies.  In addition, this location is one of very few in the world where large amounts of coprolite directly associated with a single genus was discovered.  It seemed appropriate as well as polite to nick-name these highly fossiliferous sites “egg mountain”, naming the location “*h!# mountain” would have been scientifically valid, but perhaps not as acceptable in popular literature.

Lots of Coprolite Fossils Associated with Maiasaura (M. peeblesorum)

Model of "Good Mother Lizard"

Model of “Good Mother Lizard”

Picture Credit: Everything Dinosaur

The only other locations where urolites associated with the Dinosauria have been described (as far as we know), are France and Germany.

Staypressed theme by Themocracy