All about dinosaurs, fossils and prehistoric animals by Everything Dinosaur team members.
/Palaeontological articles

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 03, 2017

Root and Branch Reform for the Dinosaur Family Tree

By | March 23rd, 2017|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

Dinosaur Family Tree Given a Hefty Shake

So, the scientific paper is out, published in the journal Nature and with the snappy title “A New Hypothesis of Dinosaur Relationships and Early Dinosaur Evolution”.  Just about everything that we thought we knew about when, where and how the dinosaurs evolved has been turned on its head.  In addition, the dinosaur family tree has been re-drawn, all the text books written about these iconic prehistoric animals published since 1887, basically got it wrong!  It’s a big story, it dwarfs Argentinosaurus!  So, let’s take a step back and examine what exactly does this new paper mean.

New Study Suggests Tyrannosaurus rex was put on the Wrong Branch of the Dinosaur Family Tree

"Stan" - Gracile T. rex at Manchester Museum.

Theropods like T. rex re-assigned and united with the bird-hipped dinosaurs in this new model.

We have tried to summarise the key findings as:

  • The clades that make up the Order Dinosauria, need to be rearranged.
  • Theropod dinosaurs which are closely related to modern birds, previously classified as Saurischian dinosaurs (lizard-hipped), need to be grouped with the bird-hipped forms in a new clade proposed as the Ornithoscelida.
  • Bird-hipped dinosaurs (Ornithischia) clade now directly associated with the evolution of birds.
  • Lizard-hipped Sauropodomorpha, the clade that includes Diplodocus, Plateosaurus and Argentinosaurus et al would now fall outside the Order Dinosauria.
  • The definition of what a dinosaur is (Dinosauria) would have to be changed to allow the Sauropodomorpha back in.
  • The first dinosaurs may not have evolved in the southern hemisphere (South America or southern Africa – Gondwana), but they may have evolved further north on the landmass called Laurasia.
  • Under this new redrawing of the dinosaur family tree, some of the Dinosauriforms (ancestors of the Dinosauria), such as Saltopus (fossils from Scotland) and the controversial Agnosphitys (fossils from Avon), provide evidence to support the idea that some of the very first dinosaurs may have evolved in the area we now know as the UK.
  • The first types of dinosaur may have been omnivores and not carnivores as generally accepted.
  • With this re-definition of dinosaur evolution, the first dinosaurs evolved some 247 million years ago, pushing the origins of the Dinosauria back some 15 million years.

The Traditional Dinosaur Family Tree Compared to the New Model

Comparing different views on the dinosaur family tree.

Simplified diagram comparing traditional view of the dinosaur family tree with the new model.

Picture Credit: Everything Dinosaur (from Baron et al 2017)

The picture above shows (top) the traditional view of the dinosaur family tree as proposed by Henry Govier Seeley in a paper entitled “On the Classification of the Fossil Animals Commonly Named Dinosauria” published in the Proceedings of the Royal Society (London) back in 1887.   This has been the accepted, conventional interpretation for the last 130 years or so.

The new model is depicted (bottom), this interpretation reflects in part, the dinosaur family proposed by Thomas Huxley in a paper published in 1870, entitled “On the Classification of the Dinosauria with Observations on the Dinosauria of the Trias” in the quarterly journal of the Geological Society.

Back in 1870, Huxley looked at compsognathids, iguanodontids, Megalosaurs and the primitive armoured dinosaur Scelidosaurus and found enough common characteristics amongst these different types of dinosaur to unite them into a single clade, which he called the Ornithoscelida (orn-nith-oh-skel-lie-dah).  The research team, writing in the academic journal “Nature” had many thousands more fossils to study than either Huxley or Seeley, they conclude that Huxley’s interpretation has more validity than the conventional view that gives precedence to Seeley’s interpretation.  Baron et al suggest that the term Ornithoscelida be resurrected to apply to Ornithischians and the Theropoda.

Hypercarnivory (Meat-eating) Evolved Twice

Everything Dinosaur’s comparison of the two family trees shows something else.  The green lines lead to those groups of dinosaurs that were predominantly herbivorous, whilst the red lines lead to dinosaur types that comprise mainly carnivores.  In the new model, the Sauropodomorpha, dinosaurs like Diplodocus and their kind are placed outside the new definition of the Dinosauria.  The herrerasaurids (Herrerasauridae), with their confusing array of dinosaur and non-dinosaur traits, are also placed outside the new strict definition of what dinosaurs are.  Dinosaurs like Herrerasaurus are not classified as Theropods in this new model, which means that meat-eating in dinosaurs evolved twice, once in the herrerasaurids and once in the Theropoda.

Herrerasaurus Gets a New Status within the Revised Dinosaur Family Tree

An illustration of a Triassic dinosaur Herrerasaurus.

Herrerasaurus Illustration

Science Itself Evolves

At Everything Dinosaur, we define science as “the search for truth”.  The authors of this new paper, graduate student Matthew Baron, Dr David Norman (Cambridge University) and Professor Paul Barrett (London Natural History Museum), reviewed a total of seventy-four different types of dinosaur and looked at their common traits and characteristics.   They started with a blank sheet of paper, bravely set aside conventional thinking and tried to find the best fit for the scientific evidence.

Explaining the researcher’s approach, a spokesperson from Everything Dinosaur commented:

“When you put together a jig-saw puzzle, you might refer to the picture on the front of the box to guide you.  What these scientists did was to look at the jigsaw pieces, ignoring the picture on the front of the box and they worked out which pieces fitted together well and which pieces didn’t.  They took a fresh look at the evidence and came up with a new way of mapping out the dinosaur family tree.  Based on the evidence, they found a better way to put the jigsaw pieces together.”

The researchers carefully studied thousands of fossil bones and mapped 457 anatomical characteristics across the 74 different types of dinosaur.  This meticulous study led them to re-draw the cladogram that represents the dinosaur family tree.

A Phylogenetic Relationship of Early Dinosaurs Plotted Against Geological Time

Re-drawing the dinosaur family tree.

The phylogenetic relationships between early dinosaurs.

The diagram above show the newly proposed phylogenetic relationship plotted against geological time for the early dinosaurs and their close relatives (Dinosauriformes).

A = the least inclusive grouping (clade) that includes the House Sparrow, Triceratops and Diplodocus.
B = the least inclusive grouping (clade) that includes the House Sparrow and Triceratops (the Ornithoscelida).
C = the most inclusive clade that contains Diplodocus but not Triceratops – (the new definition of the Saurischia).

Not “Throwing the Baby Out with the Bathwater”

This is a fascinating and intriguing insight into the phylogenetic relationships of the Dinosauria and their closest relatives.  However, numerous studies have been conducted in the past and Henry Govier Seeley’s analysis has held sway.  Some of the conclusions drawn are likely to be challenged by other palaeontologists and the debate as to the cladistic relationships and the implications for how, when and where the dinosaurs evolved is going to continue.

Take for example, the idea that the dinosaurs may have evolved further north than previously thought.  The fossils from Scotland and the west country of England (Avon) are highly fragmentary and far from complete.  Indeed, much of the Triassic material ascribed to early types of dinosaur or their near relatives, the Silesauridae, is very piecemeal.  Many more fossils need to be found before a clearer picture as to the origins of the Dinosauria can be established.

Footnote

Back in April 27th 2015, Everything Dinosaur published a blog article all about the discovery of a bizarre new Theropod dinosaur named Chilesaurus (C. diegosuarezi).  Although it was classified as a member of the lizard-hipped Theropoda, a group that were predominately meat-eaters, this Late Jurassic, South American dinosaur took a very different evolutionary path – it seems to have become a herbivore.  Chilesaurus, shows anatomical characteristics quite unlike any other Theropod dinosaur.   Not least, the pubis bone is projecting backwards, which is similar in orientation to the layout of the pelvic girdles of Ornithischian (bird-hipped) dinosaurs.  Our article about this very curious dinosaur required us to use an annotated diagram that showed the differences in the hip bones of the Saurischia (lizard-hipped) and the Ornithischia (bird-hipped) dinosaurs.  We are honoured that this same illustration was used by the BBC in the coverage of this new scientific paper.

Classifying the Dinosauria by Their Hip Bones

The shape of the hip bones help to classify the Dinosauria.

Classifying dinosaurs by the shape of their hip bones.

Picture Credit: Everything Dinosaur

The scientific paper: “A New Hypothesis of Dinosaur Relationships and Early Dinosaur Evolution” M. Baron et al published in the journal Nature.

22 03, 2017

Newly Described Silurian Fossil Honours Sir David Attenborough

By | March 22nd, 2017|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

Fossil Discovery Named in Honour of Sir David Attenborough’s 90th Birthday

Sir David Attenborough has been honoured by an international team of scientists who have named a newly described Silurian Arthropod after the veteran broadcaster and naturalist.  Sir David has had a number of new species named in his honour, this 430 million-year-old, distant relative of today’s crabs and lobsters joins a long list of flora and fauna that includes wild flowers and a Jurassic Pliosaur (Attenborosaurus conybeari).

To read an article about a kitten-sized marsupial lion named after Sir David: Attenborough’s New Kitty”

Honouring Sir David Attenborough – Cascolus ravitis

An image (computer generated) of the Silurian Arthropod Cascolus ravitis.

A computer generated image of the newly described Silurian Arthropod Cascolus ravitis.

Picture Credit: Professor David Siveter et al

Sir David grew up in Leicestershire, he and his family lived on the campus of the former University College Leicester, where his father was the principal.  As a boy, Sir David often explored the exposed Jurassic outcrops, near to his Leicester home hunting for fossils.  His love of the local countryside and the animals and plants that surrounded his home, fuelled his passion to become a scientist.

Three-Dimensional Arthropod Fossil

The fossil specimen, which measures less than ten millimetres long, is described as “exceptionally well-preserved in three-dimensions”.  The researchers, which include scientists from Imperial College (London), Oxford University and Yale (United States), as well as Leicester University, have been able to identify the exoskeleton and other parts of the animal, such as the delicate antennae, legs and the compound eyes.  It has been assigned to the Crustacea sub-phylum and joins a remarkable fossil assemblage representing a marine biota preserved when ash from a volcano covered an ancient underwater ecosystem.  The actual location of the fossil site is a closely guarded secret, the site can be found in the county of Herefordshire, close to the Welsh border.  At this location, the limestone rock sequence is interrupted by a fine-grained bedding plane that represents ash from a volcanic eruption that smothered the seabed.  The ash buried all the creatures in and around the seafloor at the time, creating a unique opportunity for palaeontologists to study this ancient habitat.

Professor David Siveter (Department of Geology, Leicester University), commented:

“Such a well-preserved fossil is exciting, and this particular one is a unique example of its kind in the fossil record, and so we can establish it as a new species of a new genus.”

Cascolus ravitis

The genus name is derived from “castrum” meaning stronghold and “colus” which translates from the Old English as “dwelling in”, terms from which the surname Attenborough is derived.  The species name is a combination of “Ratae”, the Roman name for Leicester, “vita” which means life and “commeatis” a messenger.

Sir David Attenborough Receiving a High-Resolution Image of the Fossil Named in His Honour

Sir David Attenborough receiving a copy of the high resolution image of Cascolus ravitis

Sir David Attenborough receiving a high-resolution image of the newly described Silurian fossil.

Picture Credit: Leicester University

Left to right: Derek Siveter, (University of Oxford), Sir David Attenborough, Professor Paul Boyle, President and Vice-Chancellor of University of Leicester and David Siveter, University of Leicester.

Speaking about his latest honour, the nonagenarian, who will be celebrating his 91st birthday in a few weeks’ time, stated:

“The biggest compliment that a biologist or palaeontologist can pay to another one is to name a fossil in his honour and I take this as a very great compliment.  I was once a scientist so I’m very honoured and flattered that the Professor should say such nice things about me now.”

To read about other fossil discoveries from the Herefordshire site: The Kite Runner from the Silurian of England

Prehistoric marine parasites: Prehistoric Parasites from the Silurian

Sir David Attenborough has had a Genus of Jurassic Pliosaur Named in His Honour

Attenborosaurus conybeari

Named in honour of Sir David Attenborough – Attenborosaurus

Picture Credit: Everything Dinosaur

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

The research is published in the journal Proceedings of the Royal Society B (Biology).

19 03, 2017

Dinosaurs Learn to Stand on Their Two Feet

By | March 19th, 2017|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

New Theory as to Why Bipedalism Evolved in the Dinosauria

Iconic dinosaurs such as Tyrannosaurus rex, Velociraptor, Coelophysis and Carnotaurus were all bipeds.  That is, they evolved the ability to walk on their hind legs.  Bipedalism is a trait that seems to have evolved early in history of the Dinosauria and it is a characteristic that is widespread amongst both lizard-hipped and bird-hipped forms.  It had been suggested that bipedalism arose in the ancestors of dinosaurs, to allow the forelimbs to be freed from a locomotive role, allowing them to have other uses, primarily to seize and grasp prey.  However, a team of scientists from the Department of Biological Sciences at the University of Alberta (Canada), have put forward a new theory to explain why some dinosaurs stood on two feet instead of four.  The ancestors of the dinosaurs had a “need for speed”!

The Basal Dinosauriform Marasuchus (M. lilloensis) is Typical of a Bipedal Ancestor of the Dinosauria

The basal dinosauriform Marasuchus from the Late Triassic of Argentina

The basal dinosauriform archosaur Marasuchus of the Middle Triassic. A potential ancestor of the Dinosauria.

 

Picture Credit: Pterosauriablog (author Taylor Reints)

The picture above shows the crow-sized Marasuchus, fossils of which come from the La Rioja Province (north-eastern Argentina), specifically from the Chañares Formation.  This fast running, bipedal reptile lived some 242 – 235 million years ago and the University of Alberta researchers argue that the presence of big muscles (the caudofemoralis), associated with the back of the legs and tail were central to driving the evolution of bipedalism amongst the archosaurs that were to eventually lead to the evolution of the dinosaurs.

From All Fours to Just Two Legs

Publishing in the academic periodical “The Journal of Theoretical Biology” lead author, Scott Persons and is co-worker Professor Phil Currie, argue that basal dinosauriforms were essentially quadrupeds but they evolved to stand upright, a characteristic that was passed onto their descendants the dinosaurs.

The scientists challenge the idea that bipedalism came about in order to help with the seizing of prey.

Persons stated:

“While that works for some of the very, very early dinosaurs, which were certainly carnivorous, you see a bunch of herbivorous dinosaurs evolve later on and a good many of those groups actually keep their bipedal stance, which is a little strange.”

Big Muscles in the Tail

The researchers argue, that strong muscles at the base of the tail helped to power the hind legs of these prototype dinosaurs.  This allowed them to run faster and for longer.  Hind legs evolved to become longer, whilst the forelimbs became shorter to reduce body weight and to improve balance and agility.  Some of these proto-dinosaurs gave up quadrupedalism entirely.   However, as all young dinosaur fans will happily tell you, there were lots of four-legged dinosaurs, examples being Triceratops, Stegosaurus and Diplodocus.  These dinosaurs were herbivores, they evolved heavy defensive weapons, horns and armour which meant that a faster, cursorial lifestyle was sacrificed.  As plant-eaters, they evolved ever larger stomachs and digestive tracts to help them process the tough plant material they ate, bigger guts also led to a reversion back to being a quadruped.

Palaeontologist Scott Persons added:

“In the groups where speed was no longer a concern, they often went back to being a quadruped”

A Rearing Diplodocus – A Four-Legged Dinosaur

CollectA Rearing Diplodocus.

A rearing Diplodocus!

Picture Credit: Everything Dinosaur

If you take the lizard-hipped, Sauropoda for instance, these herbivores evolved into a myriad of forms, but they all had the same basic body plan and there was a trend towards gigantism within this infraorder.  However, it has been suggested that those strong, muscular tails and powerful back legs enabled these dinosaurs to rear up to feed higher up in the vegetative canopy.  It has been suggested that baby Sauropods may have retained the ability to run on their hind legs, probably to help them escape predators.

To read an article about proposed bipedalism in juvenile Sauropods: Facultative Bipedalism in Young Sauropods

The powerful caudofemoralis muscle provides a greater source of propulsion to the back legs and it is the presence of this tail muscle that may have given the impetus to developing a two-legged stance.

Modern Lizards Provide a Clue

Modern facultatively bipedal lizards offer an analog for the first stages in the evolution of dinosaurian bipedalism.   In biology, the term facultative refers to the ability of many organisms to do things by choice rather than by obligation.  Facultatively bipedal lizards may spend most of the time on all fours, but when the need arises, such as to escape danger, these reptiles can revert to a bipedal stance.  An example of a living facultative biped lizard is the Australian frilled lizard (Chlamydosaurus kingii).

The Australian Frilled Lizard – An Example of a Living Reptilian Facultative Biped

Australian Frilled Lizard

The Australian frilled lizard – a facultative biped.

Why Don’t Fast Running Mammals Run on Two Legs?

Biomechanically, running on four legs is more efficient than running on two legs.  However, the University of Alberta researchers concluded that the behaviour of synapsid reptiles, distant ancestors of today’s fast running horses, cats, camels, and grey hounds, during the Permian, may explain the lack of bipeds amongst the Mammalia.

In the Permian geological period, it seems some animals started losing the reptilian trait of a strong leg-powering tail muscle.  Around that time, many creatures were becoming burrowers, (adapting to a fossorial lifestyle), so they needed strong front limbs for digging.  Big back legs and a long, powerful tail would have made it tough to manoeuvre in the confines of a burrow, as well as making it easier for a pursuing predator to snatch them by their tail.  The scientists postulate that living underground may have helped those proto-mammals survive the Permian mass extinction.  Their descendants would have evolved to run fast, but without the tail muscles that would have caused them to stand upright.

Commenting on the biological merits of Tetrapods evolving to favour one set of legs for running Scott Persons stated:

“That’s a really funny and strange adaptation.  Why would you choose to use just one set of limbs to help you run away when you’re most desperate?  And the answer has to do with that great big tail muscle [caudofemoralis].  It effectively sort of overpowers the back legs relative to the front legs.  What the lizards are effectively doing is popping a wheelie as they speed off.”

That cursorial advantage explains the relative abundance of cursorial facultative bipeds and obligate bipeds among fossil diapsids and the relative scarcity of either amongst the Mammalia and their close relatives.  Having lost their caudofemoralis in the Permian, perhaps in the context of adapting to a fossorial lifestyle, the mammalian line has been disinclined towards bipedalism, but, having never lost the caudofemoralis of their ancestors, the basal dinosauriforms and their relatives were more inclined to adopting a bipedal stance.

A Tale in a Tail!  Researchers Explain the Presence of Bipedalism within the Dinosauria

 

Gorgosaurus libratus illustrated.

A tale in the tail – the caudofemoralis provides propulsion leading to an evolutionary bias towards a bipedal stance.

Picture Credit: Everything Dinosaur

17 03, 2017

Primitive Neornithischian Dinosaurs and Seed Dispersal

By | March 17th, 2017|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

Plant-Eating Dinosaurs Probably Played an Important Role in Seed Dispersal

Time to catch up on our reading and first on the list of papers is this fascinating insight into the relationship between plant-eating dinosaurs and seed dispersal.  An international team of scientists from Portugal, Spain and Argentina have described a new species of primitive, bird-hipped dinosaur and an assessment of the body cavity led to the discovery of the dinosaur’s last meal.  Permineralised seeds, most of which having been identified as coming from cycads (Cycadales), suggest that herbivorous dinosaurs played an important role in seed dispersal, just as many plant-eating mammals do today.

The New Argentinian Dinosaur Isaberrysaura mollensis is Related to Kulindadromeus from Siberia

A scale model of the feathered dinosaur Kulindadromeus.

A 1:1 scale model of Kulindadromeus, closely related to Isaberrysaura.

Picture Credit: T. Hubin/RBINS

The researchers which include lead author, Leonardo Salgado (CONICET – Universidad Nacional de Río Negro), conducted a phylogenetic analysis and assigned this new dinosaur species to the basal Ornithopoda, suggesting that it is closely related to Kulindadromeus (K. zabaikalicus), fossils of which are known from geologically younger strata found in Siberia.  However, this new dinosaur, named Isaberrysaura was much larger, with an estimated body length of approximately six metres.

The Feeding Habits of Herbivorous Dinosaurs

Despite some two-thirds of all the dinosaurs described to date being plant-eaters, there is little direct evidence of the feeding habits of herbivorous dinosaurs that matches the stomach contents preserved within a carcase.  Most unaltered gut content that has been found is associated with much later dinosaurs -hadrosaurids and ornithopods.  This is the first time that gut contents have been identified in association with the remains of a basal neornithischian.

The specimen, representing a single individual, consists of an almost complete skull, vertebrae, part of the left shoulder blade (scapula), along with ribs and elements from the pelvic girdle.  It was excavated from the Los Molles Formation (Neuquén Basin, Argentina), from sediments that suggest a coastal-delta environment, the presence of the zone ammonite Sonninia altecostata in the same fossil bed, indicate that Isaberrysaura lived some 170 million years ago (Early Bajocian faunal stage of the Middle Jurassic).  These are the first dinosaur remains found in this geological unit and the one of the oldest dinosaurs known from the Neuquén Basin.  In addition, this is the first neornithischian dinosaur known from the Jurassic of South America.  The skull and the teeth show some affinity with basal stegosaurids which suggests that both the Thyreophora and neornithischian dinosaurs shared a lot of similar features (potential evidence of convergent evolution amongst plant-eating dinosaurs).

Isaberrysaura mollensis – Views of the Skull and Teeth

Isaberrysaura mollensis - views of the skull and teeth.

The skull in (a) dorsal and left lateral view (c) with corresponding line drawings (b and d).  Premaxillary tooth (e) and maxillary teeth (e and f).

Picture Credit: Scientific Reports

 Why Isaberrysaura?

This month, we have once again been celebrating International Women’s Day (March 8th), it is pleasing to note that the female form of “saurus” has been chosen when it came to naming this new dinosaur, as the genus has been erected to honour Isabel Valdivia Berry, who reported the finding of the holotype material.  In the body cavity, the researchers were able to identify a mass of permineralised seeds.  These were identified as belonging mostly to the Cycadales group of plants.  These tough seeds would have passed through the dinosaur’s gut and would have been deposited in the dung.  This fossil discovery suggests a possible and unexpected role of bird-hipped dinosaurs, that of Jurassic seed-dispersal agents.

An Analysis of the Gut Contents of Isaberrysaura 

The gut contents of Isaberrysaura mollensis.

Permineralised seeds identified in the gut cavity of Isaberrysaura mollensis.

The photograph above shows images of the body cavity showing evidence of the seed fossils.

Some of the fossils show that their fleshy seed-coats are still intact (sc = sarcotesta), this indicates that these seeds were swallowed whole with little or no chewing action in the mouth.

The scientific paper: “A New Primitive Neornithischian Dinosaur from the Jurassic of Patagonia with Gut Contents”, published in the journal “Scientific Reports”

15 03, 2017

Not All Mesozoic Crocodiles Were Giants

By | March 15th, 2017|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

Knoetschkesuchus – Living on an Island

Last month, scientists published in the on line academic journal “PLOS ONE” a paper that provided details of the discovery of a new species of Late Jurassic terrestrial crocodile, but this animal was no ground-shaking giant, like most of its kind (atoposaurids), it probably had a maximum length of under a metre and it would have weighed a couple of kilogrammes or so.

Lead author of the research paper, Daniela Schwarz (Leibniz Institute for Evolutionary and Biodiversity Research, Germany), in collaboration with colleagues, re-examined fossils including skull material (an adult and a juvenile specimen), that had previously been assigned to the atoposaurid Theriosuchus – a genus of crocodile-like reptile that is known from a large number of fossils dating from the Late Jurassic and into the Early Cretaceous from places as far apart as Thailand and southern England.  However, when the beautifully preserved fossils were studied using CT scans and three-dimensional images of the fossil material created, a number of autapomorphies were identified to allow the erection of a new genus.

A View of the Larger Specimen of Knoetschkesuchus langenbergensis

Knoetschkesuchus langenbergensis fossil material (larger specimen).

Knoetschkesuchus langenbergensis fossil material.

Picture Credit: PLOS ONE

The little crocodile has been named Knoetschkesuchus langenbergensis, the fossils come from the famous Langenberg Quarry, located near the town of Goslar, Lower Saxony, northern Germany.  The limestones and marls that form the quarry site, were laid down in shallow inlets associated with an island archipelago.  The Knoetschkesuchus material comes from Bed 83, the same location as the fossils of the dwarf Sauropod Europasaurus (E. holgeri).

Lots of Terrestrial Crocodiles in the Mesozoic

Knoetschkesuchus langenbergensis fossil material has been dated to the Upper Kimmeridgian stage of the Jurassic, approximately 154 million years ago, like most members of the Atoposauridae it had large eyes and it may have been a fast runner.  The researchers conclude that the Langenberg Quarry fossils represent a new species because of unique features of the skull, such as openings in the jaw bone and in front of the eye, as well as the shape and placement of the animal’s tiny teeth.  The teeth are heterodont in nature (different shapes), at the tip of the snout they are pointy and needle-like, very typical of a small crocodilian, but towards the back of the jaws they are broader and more rounded, particularly in the lower jaw.  It has been suggested that these teeth were adapted for crushing hard-shelled prey, such as snails, which are known from abundant gastropod fossils associated with Bed 83.

Line Drawings Showing Various Views of Both the Adult and Juvenile Skull Specimens

Knoetschkesuchus skull illustrations

Knoetschkesuchus skull drawings.

Picture Credit: PLOS ONE with additional annotation by Everything Dinosaur

Note

Elements of the adult skull fossil have been drawn based on scaled-up material from the juvenile specimen.

Dr Schwarz commented:

“The study describes a new diminutive crocodile Knoetschkesuchus langenbergensis that lived around 154 Million years ago in north-western Germany.  Knoetschkesuchus belongs to the evolutionary lineage that leads to modern crocodiles and preserves for the first time in this group two skulls in 3-D, allowing us detailed anatomical studies via micro-CT images.  Our research is part of the Europasaurus-Project which studies the remains of a unique Jurassic island ecosystem in northern Germany.”

A Unique Island Ecosystem

The Langenberg Quarry preserves the remains of a unique Late Jurassic European ecosystem.  The islands were relatively small and this led to a divergence between residents of these islands and their ancestors which lived on the larger landmasses to the east.  For example, in response to limited food resources and space, the Sauropod Europasaurus became a dwarf form.  The atoposaurid crocodiles probably filled a number of ecological niches within the food chain, including that of arboreal predators.  These distant ancestors of today’s crocodiles were in turn preyed upon by a variety of Theropod dinosaurs, the majority of which are only known from fragmentary teeth.  What is quite remarkable, is the diversity of the Theropod teeth found in Upper Jurassic deposits of northern Germany.  Studies have suggested that representatives of the Tyrannosauroidea, as well as Allosauroidea, Megalosauroidea and probably Ceratosauria roamed this part of the world some 155 to 150 million years ago.

The genus name (Knoetschkesuchus) is a combination of the family name of Nils Knötschke, and suchus (from the Greek meaning crocodile).  The genus name honours of Nils Knötschke (Dinosaurier-Freilichtmuseum Münchehagen), who collected, prepared, and curated several important fossil specimens from the Langenberg Quarry.

14 03, 2017

Pushing Back the Origins of Complex Life

By | March 14th, 2017|Dinosaur and Prehistoric Animal News Stories, Main Page, Palaeontological articles|0 Comments

Scientists Uncover Evidence of the Earliest Plants

One of the most significant steps in the history of life on Earth may have occurred earlier than previously thought, according to a new study published by Scandinavian scientists in the on line academic journal “PLOS Biology”.  The evolution of simple, non-nucleated cells (prokaryotes) to large, more complex and specialist cells (eukaryotes) may have taken place some 400 million years earlier.  The team might have uncovered evidence of the oldest plants known to science.

Red Algae – Look Out for the Stacked Plates

The researchers which include Therese Sallstedt (Swedish Museum of Natural History), examined exquisitely preserved, three-dimensional fossils, found in very ancient sedimentary rocks from central India (Vindhyan basin).  These rocks are known for their abundance of micro-fossils, and the researchers analysed the minute fossil remains that represent a biota that once existed in a shallow sea.  The team identified structures within the micro-fossils that correspond to chloroplasts, which are found within plant cells today.  The strata has been dated to approximately 1.6 billion years ago, the photosynthetic biomats amidst extensive cyanobacterial micro-fossils, had filaments and other features such as plate-like discs that represent stacked cells that are very reminiscent of red algae (Rhodophyta).  Prior to this discovery, experts believed that the earliest eukaryotes evolved some 1.2 billion years ago, as demonstrated by the oldest known multicellular organism Bangiomorpha pubescens, found in Canadian rocks around 1.2 billion years old.  Bangiomorpha is related to today’s red algae, it seems, from this new evidence, that the multicellular Rhodophyta, complete with their complex cells containing a nucleus, have been on Earth for far longer than previously thought.

Two Forms of Red Algae

The fossils appear to show two distinct types of red algae: Rafatazmia chitrakootensis, characterised as filamentous in shape and containing large plate-like, stacked discs that the researchers think may be parts of algal chloroplasts and Ramathallus lobatus, which would have been more rounded in shape and fatter.

Digital Images of Rafatazmia chitrakootensis

Evidence of the oldest plants uncovered.

Rafatazmia chitrakootensis digital images of the ancient eukaryote (chloroplast structures highlighted green).

Picture Credit: PLOS Biology

The picture above shows (A–L) Holotype, NRM X4258.  (A) Surface rendering.  (B) Volume rendering with rhomboidal disks coloured for visibility.  (C) Virtual slice. (D) Surface.  (E) Volume. (F–L) Transverse slices (positions indicated in B).  (M–O) NRM X5620, surface, volume, slice.  (P–R) NRM X5574, surface, volume, slice.  Scale bars 50 μm.

Most scientists already believed that red algae (Rhodophyta) to be some of the earliest eukaryotic organisms to evolve.  Pushing the date back by some 400 million years or so, has implications for our understanding of evolution as a whole and may help clear questions about the rates at which mutations occur in the genome over time.

The scientific paper: “Three-dimensional Preservation of Cellular and Subcellular Structures Suggests 1.6 billion-year-old Crown-group Red Algae”, published in “PLOS Biology.”

10 03, 2017

Late Jurassic Crocodile Eggs and Meat-Eating Dinosaurs

By | March 10th, 2017|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Crocodylomorph Ootaxa and the Theropod Connection

A number of media outlets have reported upon a paper published in the on line journal PLOS One which describes two new ootaxa (the name given to a species described just from egg fossils), of crocodilians from the Upper Jurassic rocks of western Portugal.  The focus on many of these reports has been on the age of the fossilised crocodile eggs.  Having been laid more than 150 million years ago, they are the oldest crocodilian eggs described to date.  However, the research paper itself, hints at a remarkable potential relationship between these ancient reptiles and their close cousins, Theropod dinosaurs.

A Clutch of Unhatched Late Jurassic Crocodylomorph Eggs (Lourinhã Formation)

Suchoolithus portucalensis fossil eggs.

The unhatched crocodylomorph eggs (Cambelas) ascribed to Suchoolithus portucalensis.

The Famous Lourinhã Formation

The first crocodylomorph eggs were found in 1987 and over the years a number of egg and egg shell fragment discoveries have been made.  The eggs are very similar to the eggs of extant crocodiles but the scientists have been able to identity distinctions between the fossil specimens (not least the size).  This has led to the erection of two new ootaxa.  The eggs of the smaller of the two crocodylomorphs – Suchoolithus portucalensis are shown in the photograph above.  The eggs are quite small and the researchers estimate that the adult female that laid these eggs would have been around seventy centimetres in length.  The second ootaxa to be named – Krokolithes dinophilus, which is known from a number of fossil specimens collected from four locations, is represented by larger but broken eggs and shell fragments.  The research team estimate that the female croc that laid these eggs would have been around the size of a female American Alligator (A. mississippiensis), probably more than two metres long.

Location of the Egg Fossil Finds Referred to in the New Study

Map showing the location of the fossil finds.

A map showing the location of the crocodylomorph egg fossil sites.

Picture Credit: PLOS One with additional annotation from Everything Dinosaur

Key

The picture above shows the five fossil locations that are covered in the scientific paper as well as indicating the position of the Lourinhã Formation in relation to the rest of Portugal.  A total of thirteen fossilised eggs collected at the Cambelas site have been ascribed to the ootaxa Suchoolithus portucalensis (the name translates from Latin as “egg stone crocodile from Portugal”), the fossils represent a clutch of unhatched eggs.  Eggs laid by a much larger crocodylomorph are associated with the other four locations, namely North and South Paimogo, Casal da Rola and Peralta.  These fossils comprise broken eggs and numerous shell fragments, they have been ascribed to the ootaxa Krokolithes dinophilus (which is from the Greek and means “crocodile eggs found in association with dinosaurs”).

Holotype of Krokolithes dinophilus (Specimen Number ML760 from Paimogo N, Praia da Amoreira-Porto Novo Member, Lourinhã Formation)

Krokolithes dinophilus fossil material.

Holotype of the oospecies Krokolithes dinophilus.

Found in Association with Theropod Dinosaur Nests

All the egg fossils (except for the Cambelas site fossils), were found in association with Theropod dinosaur nests and eggs.  So in essence, the palaeontologists, which included João Russo and Octávio Mateus (Museu da Lourinhã, Portugal), have identified four occurrences where the fossils of the large crocodylomorph K. dinophilus are found in the same place as the eggs and nests of large, meat-eating dinosaurs.  This could suggest some sort of biological relationship between the crocodiles and the Theropods.  This is certainly an intriguing thought and there are no parallels that can be drawn between this idea and the behaviour of modern crocodiles.  Extant crocodilians tend to lay eggs in relatively secluded places and a parent (usually the female), will stand guard helping to protect the nest and the subsequent hatchlings from predators.

It can be speculated that these prehistoric crocodiles preferred to nest in close proximity to large meat-eating dinosaurs as perhaps the presence of two different types of large predator helped to protect all the nests from potential danger.  With so many threats to eggs and recently hatched animals around in the Late Jurassic, it could be suggested that there was a degree of mutual benefit between various species – a symbiotic relationship with both the Theropods and the crocodilians gaining an advantage.

Some of the K. dinophilus egg fossils come from sites associated with the nests of Lourinhanosaurus (Lourinhanosaurus antunesi), a formidable Late Jurassic hunter, which may have reached lengths of eight metres or more.  The beautifully preserved Theropod embryos were the inspiration behind the limited edition “Baby Bonnie” 1:1 scale replicas created by Rebor.

The Rebor “Baby Bonnie” Scale Model of a Lourinhanosaurus antunesi Embryo

"Bony Bonnie" from Rebor.

The Rebor Club Selection Lourinhanosaurus replica.

Picture Credit: Everything Dinosaur

Other Krokolithes dinophilus fossils have been found in proximity to the nests and eggs of the ootaxon Preprismatoolithus coloradensis (which could represent the eggs of a large Allosaurus).  We expect palaeoartists to have a field day illustrating nesting site scenes featuring a mix of large predators together.

The Theory has Drawbacks

The absence of any modern parallels and the incomplete fossil record provides considerable drawbacks when it comes to the plausibility of crocodiles nesting alongside meat-eating dinosaurs.  Some of the fossil eggs shell fragments from the Paimogo locations might have been transported and deposited close to the Theropod nests, therefore their placement in the strata is not necessarily their original nesting context.  We at Everything Dinosaur have proposed that it is possible that crocodiles and Theropod dinosaurs preferred to use the same nesting locations, but they may not have bred at the same time.  After all, using an already dug out nest, one that had been used recently by a large, carnivorous dinosaur might prove advantageous for a wily crocodile.

The scientists conclude that this potential egg-laying symbiosis is a mystery and that going forward, further findings and studies are needed to ascertain if there was indeed some kind of reproductive relationship between crocodylomorphs and Theropods in the Late Jurassic of Portugal.

Views of the Lourinhã Formation

Views of the Lourinha Formation.

(A), location of Paimogo, Northern Lourinhã Formation, Praia da Amoreira-Porto Novo and Praia Azul Members. (B), location of Cambelas, Southern Lourinhã Formation, Assenta Member.

Picture Credit: PLOS One

8 03, 2017

Unravelling a Fishy Tale

By | March 8th, 2017|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|1 Comment

Reassessment of Ichthyosaur Material Solves Century Old Mystery

Ichthyosaurs were a very successful group of marine reptiles. They originated during the Triassic and thrived in the seas of the Mesozoic and had a global distribution, but towards the end of the Cretaceous, these dolphin-shaped animals, that seemed so perfectly adapted to their environment, became extinct.  They were the first, large extinct reptiles brought to the attention of the scientific world.  It is difficult to avoid mention of the Ichthyosaurs when looking at information that outlines the history of palaeontology, however, despite first having been described nearly 200 years ago, (1821), there is still a lot we don’t know about these iconic “fish lizards”.

The Iconic Ichthyosaurus

An Ichthyosaur illustration.

An Ichthyosaur (courtesy of Robert Richardson).

Picture Credit: Robert Richardson

The Long History of Ichthyosaur Research

It is the long history of scientific study and research into the Ichthyosaurs that has proved to be a bit of a headache for today’s palaeontologists.   Dean Lomax, a palaeontologist and Honorary Scientist at The University of Manchester, working with Professor Judy Massare of Brockport College, New York, have studied thousands of Ichthyosaur specimens and have delved through hundreds of years of records to solve an ancient mystery, a mystery that dates back to the early 1820’2, when the English geologist William Conybeare, described the first species of Ichthyosaurus.

Many Ichthyosaur fossils were found in England during the early 19th century, but it was not until 1821 that the first Ichthyosaur species was described called Ichthyosaurus communis.  This species has become one of the most well-known and iconic of all the British fossil reptiles, after all, an Ichthyosaurus even featured on a set of specially commissioned Royal Mail stamps to celebrate 150 years of British palaeontology!

To read article about the Royal Mail commemorative stamps: Royal Mail Issues New Prehistoric Animal Stamps

In 1822, three other species of Ichthyosaurus were described, based on differences in the shape and structure of their teeth.  Two of the species were later re-identified as other types of Ichthyosaur, whereas one of these species, called Ichthyosaurus intermedius, was still considered closely related to I. communis.

In the years that followed, many eminent scientists, including Sir Richard Owen (the man who coined the word dinosaur), studied “fish lizard” fossils collected from Dorset, Somerset, Yorkshire and other locations in England.  Their studies and observations of Ichthyosaurus communis and I. intermedius resulted in confusion with the species, with many skeletons identified on unreliable grounds.

Commenting on this palaeontological puzzle, Dean Lomax stated:

“The early accounts of Ichthyosaurs were based on very scrappy, often isolated, remains.  This resulted in a very poor understanding of the differences between species and thus how to identify them.  To complicate matters further, the original specimen of Ichthyosaurus communis is lost and was never illustrated.  Similarly, the original specimen of I. intermedius is also lost, but an illustration does exist.  This has caused a big headache for palaeontologists trying to understand the differences between the species.”

Hunting for Clues to Help Solve a “Fish Lizard” Mystery

Dean Lomax and Judy Massare examining Ichthyosaur specimens.

Dean Lomax and Judy Massare examining Ichthyosaur specimens in the marine reptile gallery at the Natural History Museum (London).

Picture Credit: Dean Lomax

In the mid-1970’s, palaeontologist, Dr Chris McGowan was the first to suggest that Ichthyosaurus communis and I. intermedius may represent the same species.  He could not find reliable evidence to separate the two species.  Subsequent studies argued for and against the separation of the species.

In this new research, Dean and Judy have reviewed all of the research for and against the separation of the two species.  This is the most extensive scientific study ever published comparing the two Jurassic-aged marine reptiles.   The pair of scientists have confirmed that the species are the same and that features of Ichthyosaurus intermedius can be found in other Ichthyosaur species, including I. communis.

It seems that the fossil material ascribed to the species Ichthyosaurus intermedius lack any autapomorphies – distinctive features or derived characteristics and traits that are unique to that taxon.

Thanks to the efforts of these two researchers, a fishy tale that is over a hundred years may have been resolved.

In recent years, the duo have described three new species and have provided a reassessment of historical species.  Their work has provided a far superior understanding of the species than has ever been produced.

The research has been published in Journal of Systematic Palaeontology: http://dx.doi.org/10.1080/14772019.2017.1291116.

2 03, 2017

Very Near to “Near Bird”

By | March 2nd, 2017|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

Closest View Yet of Anchiornis “Near Bird”

More than 225 fossils of the Late Jurassic feathered dinosaur Anchiornis (A. huxleyi) have been found to date and this relative abundance of fossil specimens in conjunction with some very sophisticated laser technology, has enabled scientists to gain the best idea yet as to what dinosaurs actually looked like.  Anchiornis huxleyi fossils come from the Tiaojishan Formation of Liaoning (China) and the dinosaur’s name means “Huxley’s near bird”, honouring the 19th Century English scientist Thomas Henry Huxley, an early supporter of Darwin’s theory of evolution, and one of the first academics to propose a close evolutionary relationship between the birds and the Dinosauria.  How apt that the use of a relatively new technique in palaeontology, that of the production of laser-stimulated fluorescence images, has enabled palaeontologists to get closer to “near bird” than ever before.

An Illustration of the Late Jurassic Dinosaur Anchiornis (A. huxleyi) Based on the New Images

An illustration of Anchiornis huxleyi.

An illustration of Anchiornis huxleyi.

Picture Credit: Julius Csotonyi

Laser-stimulated fluorescence (LSF)

Writing in the journal “Nature Communications”, researchers from the University of Hong Kong in collaboration with scientists from Linyi University (Shandong Province), the Chinese Academy of Sciences and a number of American research institutions, report on the reconstruction of a feathered dinosaur’s body outline based on high-definition images of preserved soft tissues and their integumental covering.

The Body Plan of Anchiornis huxleyi Created from the High-Definition Images

Anchiornis reconstructed body outline.

Reconstructed body outline of the bird-like feathered dinosaur Anchiornis using laser-stimulated fluorescence images.

Picture Credit: Wang X L, Pittman M et al

The coloured areas represent different fossil specimens and the black areas are approximated reconstructions.  For the first time palaeontologists have an accurate body outline of a bird-like dinosaur.  The scale bar in the image is 1 cm and the body length of Anchiornis (head to tail) is approximately 40 cm.

Laser-stimulated fluorescence (LSF), is a revolutionary new technique using high power lasers that makes unseen soft tissues preserved alongside the bones, literally “glow in the dark” by fluorescence, until the application of this new technique, palaeontologists had to infer body plans based on the fossilised bones and evidence of muscle scars using extant animals as comparisons.  One of the corresponding authors of the scientific paper, Dr Michael Pittman (Department of Earth Sciences, the University of Hong Kong), explained how he and his co-workers reconstructed the first highly detailed body outline of a feathered dinosaur based on high-definition images of its preserved soft tissues.

A View of the Wing of Anchiornis Under Laser-stimulated Fluorescence

The wing of Anchiornis seen under laser-stimulated fluorescence.

The wing of the bird-like feathered dinosaur Anchiornis under laser-stimulated fluorescence.

Picture Credit: Wang X L, Pittman M et al

This ground-breaking research has helped palaeontologists to see just how closely, Anchiornis of the Late Jurassic, resembled modern birds.  For example, in the image above, folds of skin in front of the elbow and behind the wrist (referred to as a patagium), can be made out.  The patagium was covered in feathers, just like in modern birds.

The laser-stimulated fluorescence method was developed by collaborator Tom Kaye (Foundation for Scientific Advancement, Arizona, USA).  The technique involves scanning fossils with a violet laser in a dark room. The laser “excites” the few skin atoms left in the matrix making them glow, revealing what the shape of the dinosaur actually looked like.

Dr Michel Pittman with the Laser Scanner

Dr Pittman and the laser scanner.

Dr Pittman holding the laser scanner pictured behind is an illustration of Anchiornis.

Picture Credit: Dr M Pittman

Dr Pittman commented:

“For the last 20 years, we have been amazed by the wondrous feathered dinosaurs of north-eastern China.  However, we never thought they would preserve soft tissues so extensively.”

Over Two Hundred Specimens Examined

Dr Pittman and his colleagues examined over two hundred specimens of the feathered bird-like dinosaur Anchiornis to find the dozen or so that showed special preservation.  The quantitative reconstruction that the team developed shows the contours of the wings, legs and even perfectly preserved foot scales, providing new details that illuminate the origin of birds.  It seems that Anchiornis had “drumsticks” just like a modern bird too.

Dr Pittman at Work Checking a Specimen Using the Laser Technique

Scanning Anchiornis fossils.

Dr Pittman examines fossils using LSF in Shandong TianYu Museum of Natural History.

Picture Credit: Dr M Pittman

When first described in 2009, Anchiornis was heralded as an important transitional fossil between feathered dinosaurs and volant (flying) forms.  Using this new technique (LSF), Dr Pittman and his colleagues found that the shape of wing was in many ways similar to modern birds, but it also had some seemingly primitive characteristics like feathers arranged more evenly across the wing rather than in distinct rows.  This research suggests that Anchiornis could produce a relatively straight arm, a posture broadly found in many living gliding birds (for example, Cormorants, Albatrosses and Pelicans).  The research identifies a previously unknown aspect of arm morphology differentiation at the earliest stages of paravian evolution (at least by the Oxfordian stage of the Late Jurassic), that may even have been widespread.  These new insights provide crucial information for reconstructing how dinosaurs experimented and eventually achieved flight.

Dr Pittman Pictured with Images Created to Illustrate This New Research

Dr Pittman with a body Plan and drawing of Anchiornis.

Dr Pittman holding a drawing and a body plan of Anchiornis.

Picture Credit: Dr M Pittman

To read an article about the discovery of Anchiornis huxleyiOlder than Archaeopteryx

The scientific paper: Wang, X. et al. “Basal Paravian Functional Anatomy Illuminated by High-detail Body Outline” published in Nature Communications (Nat. Commun. 8, 14576 doi: 10.1038/ncomms14576 2017).

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

22 02, 2017

The Half Tonne Rat

By | February 22nd, 2017|Dinosaur and Prehistoric Animal News Stories, Main Page, Palaeontological articles|0 Comments

Super-sized Rodent Re-Writes Family Tree

The skull and jaws from a pair of giant rodents, that represent an extinct species that could have weighed as much as half a tonne, are helping to re-shape the rodent family tree.  Study of these new fossils have led researchers to propose a formal revision of the three known species of the genus Isostylomys into just one species, Isostylomys laurillardi.

These are the best-preserved fossils to date of this extinct group, which was previously known only from skull fragments and individual teeth, the scientists report in a new study, published in the “Journal of Systematic Palaeontology”,

The new fossils of the two rodents, an adult and a juvenile, paint a more complete picture of these extinct and massive rat-like animals.  For example, the fossil discoveries raised questions about how these giant rodents were classified within their genus, and hint that several species that were thought to be related may instead be a single species.  The fossils add to our knowledge regarding giant members of the Dinomyidae family and is helping palaeontologists to reappraise the phylogeny of this once diverse and speciose group of South American mammals.

The Giant Miocene Rodent Isostylomys laurillardi (Adult and Juvenile)

Isostylomys laurdillardi a giant prehistoric rodent.

Isostylomys laurillardi (adult and juvenile).

Picture Credit: Renzo Vaira/Taylor & Francis

The fossil material comes from the exposed cliffs in the Río de la Plata coastal region of southern Uruguay.  The fossils have been dated to the Miocene Epoch (9.5 to 10 million-years-ago approximately).  The researchers, including lead author, Dr Andres Rinderknecht of the Museo Nacional de Historia Natural (Uruguay), examined the teeth and skulls of fossil specimens, comparing them to the bones and teeth of the largest living rodent the Capybara (Hydrochoerus hydrochaeris).

The research team conclude that, due to similarities in the adult’s and the juvenile’s teeth structure, previously found fossils, which were smaller and thought to belong to a different species, were in fact from the same species.

Skull and Jaw Fossils of Isostylomys laurillardi

Isostylomys laurillardi fossil material (MNHN 2187)

Skull in ventral view (A), skull and mandible in left lateral view (B), and mandible in occlusal view (C).

Picture Credit: Taylor & Francis

The picture above shows the adult skull in ventral view seen from underneath, (A), and the skull and jaw viewed from the side (B).  Picture (C) shows the jaw in occlusal view, the scale bar is five centimetres.

The authors have consequently proposed that members of the subfamily Gyriabrinae could represent juveniles belonging to other subfamilies of Dinomyidae and that three known species of the genus Isostylomys should be merged into just one species, Isostylomys laurillardi.

Commenting on the team’s conclusions, Dr Rinderknecht stated:

“Our study shows how the world’s largest fossil rodents grow and we describe fossil remains of a giant rodent baby and an adult.  Comparing them we conclude that from very young the giant rodents already were very similar to the adults which allows us to deduce that the great majority of the hypotheses before posed were wrong.  The juvenile and the adult analysed here represent some of the largest rodents known to science with some of these animals weighing almost a ton.”

The Giant Incisor of the Adult Isostylomys

Giant rodent tooth fossil (Isostylomys)

MNHN 2187 the giant lower right incisor of (Isostylomys),

Picture Credit: Taylor & Francis

The adult remains found consist of an almost complete skull with a partial jaw, while the juvenile’s remains are of a complete lower jaw and the right calcaneum (heel bone).  Almost all previous discoveries of this kind have consisted of isolated teeth, and small fragments of skulls or jaws, which make this discovery some of the best-preserved remains of giant dinomids known to science.

“Making a Giant Rodent: Cranial Anatomy and Ontogenetic Development in the genus Isostylomys (Mammalia, Hystricognathi, Dinomyidae)”.

By Andrés Rinderknecht, Enrique Bostelmann and Martin Ubilla, published by Taylor and Francis.

The scientific paper: Access the scientific paper here.

Load More Posts