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

22 06, 2020

Getting To Grips with the Jaws of Clevosaurus

By | June 22nd, 2020|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos|0 Comments

Did the Ancient Rhynchocephalians Out Compete Early Mammaliaforms?

Had you been around south Wales or south-western England some 200 million years ago, you would most probably have required a boat to get about.  The area around the Bristol channel today (where you still need a boat), during the Early Jurassic, consisted of a series of small islands surrounded by a warm, shallow tropical sea.  This archipelago (referred to as the Mendip Archipelago), was home to small dinosaurs and also to a variety of other reptiles including five species of Clevosaurus.  Clevosaurs are members of an ancient Order of reptiles called the Rhynchocephalia.  A new study published in the journal of the Palaeontological Association, suggests that these hardy reptiles may have filled the roles performed by early mammaliaforms on some of these small islands.

In addition, where Clevosaurus fossils are found, mammaliaform fossils tend to be lacking, so did these two types of tetrapod compete with each other for the same food resources?  This new research carried out by members of the School of Earth Sciences (University of Bristol), indicates that this could have been the case.  The scientists examined the biomechanics of the skulls of these lizard-like reptiles in a bid to gain an understanding of the likely diets of the species studied.  Different species of Clevosaur had different bite forces, which hints at a degree of niche partitioning within this genus.  This may explain why five different species were able to exist within a relatively small area.

Different Species of Clevosaurus may have had Slightly Different Diets

Niche partitioning within the Cleovosaurus genus.

Clevosaurus feeding habits – niche partitioning in Early Jurassic Clevosaurs.  The illustration shows two species of Clevosaurus associated with the Mendip Archipelago feeding on different types of insect prey.  Clevosaurus hudsoni feeding on a hard-shelled beetle, whilst (bottom), Clevosaurus cambrica consumes a softer insect without a carapace.

Picture Credit: Sofia Chambi-Trowell (University of Bristol)

Computerised Tomography Used to Analyse Skull Biomechanics

PhD student, Sofia Chambi-Trowell, from Bristol’s School of Earth Sciences, worked on CT scanned skulls of ancient rhynchocephalians and found differences in their jaws and teeth.

The student commented:

“I looked at skulls of two closely related species of Clevosaurus, Clevosaurus hudsoni and the slightly smaller Clevosaurus cambrica – the first one came from a limestone quarry near Bristol and the other one from South Wales.  Clevosaurus was a lizard-like reptile, but its teeth occluded precisely, meaning they fit together perfectly when it was feeding.  But what was it eating?”

Rhynochocephalians (beak heads), were a very successful, globally distributed group of diapsid reptiles that flourished during the Mesozoic.  The Tuatara (Sphenodon punctatus), is the only living member of this order, the Tuatara is confined to small islands off the coast of New Zealand and some specially designated and protected release sites on North Island.

Whilst studying the extant Tuatara is of great assistance to palaeontologists, expanding any findings to extinct members of this group is challenging.  Likewise, identifying the feeding habits of long extinct species is equally difficult.  However, finite element analysis conducted on two, near complete, three-dimensionally preserved skulls (Clevosaurus hudsoni and Clevosaurus cambrica respectively), provided bite force data and an assessment of jaw biometrics.  From this information, the potential feeding preferences of these two closely related reptiles could be inferred.

The Last of the Rhynochocephalians – A Tuatara

Tuatara.

A Tuatara.  It may resemble a lizard but the Tuatara is the last living example of the Order Rhynchocephalia.

Picture Credit: Everything Dinosaur

The researchers found that Clevosaurus had bite forces and pressures sufficient to break down beetles, and even small vertebrates easily, suggesting they could have taken the same prey items as the early mammals on the islands.  Calculations of muscle forces show that Clevosaurus hudsoni could take larger and tougher prey than the more slender jaws of Clevosaurus cambrica.

Co-author of the scientific paper and the project supervisor, Professor Emily Rayfield (University of Bristol) stated:

“We wanted to know how Clevosaurus interacted with the world’s first mammals, which lived on the Bristol islands at the same time.  I had studied their jaw mechanics a few years ago and found they had similar diets and that some fed on tough insects, others on softer insects.”

This study, having identified difference in jaw mechanics between different species of Clevosaurus provides a hypothesis as to why several species of Clevosaurus could co-exist in the same habitat.  Niche partitioning could have been taking place with each species avoiding competition by specialising in hunting and eating different types of prey.  As the data generated in this study is roughly comparable to what is known about the jaws of early mammaliaforms, it raises the intriguing prospect that the jaws may have been functionally similar and thus rhynochocephalians and early mammaliaforms were in direct competition with each other for food resources.

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

The scientific paper: “Biomechanical properties of the jaws of two species of Clevosaurus and a reanalysis of rhynchocephalian dentary morphospace” by Sofia A. V. Chambi‐Trowell, David I. Whiteside, Michael J. Benton and Emily J. Rayfield published in Palaeontology.

20 06, 2020

Fossil “Stick” Proves to be New Species of Ancient Plant

By | June 20th, 2020|Dinosaur and Prehistoric Animal News Stories, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Keraphyton mawsoniae – Late Devonian Fern-like Plant

A fossil found more than fifty years ago and described as a “fossilised stick” has proved to be a new species of Late Devonian plant and it is helping scientists to better understand the flora of the landmass of Gondwana.  The specimen measures a little over 9 cm in length, with a width across its ribbed surface of around 2 cm.  It was found by amateur geologist John Irving whilst exploring the banks of the Manilla River in Barraba (New South Wales, Australia), after a period of extensive flooding.  It remained unstudied in the fossil collection of the geological survey of New South Wales for five decades until it was despatched to France as part of a wider study to map plant evolution.

The Fossil and Cross-sectional Slices (K. mawsoniae)

Keraphyton mawsoniae fossil.

The newly described Keraphyton mawsoniae a fern-like land plant from the Late Devonian of Australia.  Scale bar in (B) equals 2 mm and scale bars in C-H equal 500 μm.

Picture Credit: Champreux et al (PeerJ)

The picture (above), shows (A) the fossil specimen before preparation, (B) a general view of the stem system shown in cross-section, with (C-H) highly magnified areas showing the internal structure of the plant.  The fossil is from the Mandowa Mudstone Formation (Upper Devonian) and it is believed to represent a plant stem.

A Very Rare Fossil Discovery

During the Middle to Late Devonian land plants were becoming larger, more complex and diverse.  Major groups of plants that were to dominate the flora of the Mesozoic evolved and the first widespread forests and land-based ecosystems became established.  Well-preserved plant fossils from this time in Earth’s history are exceptionally rare.  Plants related to ferns and other types that produce seeds (Euphyllophytina), became more specious during this time in Earth’s history, fossils of fern-like plants are known from the northern hemisphere but the Gondwanan record is extremely sparse.

The French laboratory of Botany and Modelling of Plant Architecture and Vegetation (AMAP) in Montpellier has been collating data on early plant species from the Devonian/Carboniferous of Australia and Antoine Champreux, studied the fossil specimen as part of his Master’s Degree before completing his research whilst a PhD student at Flinders University in South Australia.

Gondwana During the Late Devonian (Position of Australia)

Map showing the location of the Barraba fossil find in relation to Gondwana.

A map showing the location of Australia in relation to the rest of Gondwana during the Middle to Late Devonian.  The position of the fossil discovery is highlighted.

Picture Credit: University of Witwatersrand with additional annotation from Everything Dinosaur

Antoine commented:

“It’s nothing much to look at – just a fossilised stick – but it’s far more interesting once we cut it and had a look inside.  The anatomy is preserved, meaning that we can still observe the walls of million-year-old cells.  We compared the plant with other plants from the same period based on its anatomy only, which provide a lot of information.”

The research team found that this early land plant represents a new genus of plant, sharing some similarities with modern ferns and horsetails.

Antoine added:

“It is an extraordinary discovery, since such exquisitely-preserved fossils from this period are extremely rare.  We named the genus Keraphyton (like the horn plant in Greek), and the species Keraphyton mawsoniae, in honour of our partner Professor Ruth Mawson, a distinguished Australian palaeontologist who died in 2019.”

To read about a bizarre, giant predatory marine worm from the Devonian: Monster Worm of the Devonian.

The scientific paper: “Keraphyton gen. nov., a new Late Devonian fern-like plant from Australia” by Antoine Champreux​, Brigitte Meyer-Berthaud, and Anne-Laure Decombeix published in the open access journal PeerJ.

19 06, 2020

The First Dinosaur Eggs were Soft

By | June 19th, 2020|Adobe CS5, Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

The First Dinosaur Eggs were Soft like a Turtle’s

The scientific paper has a succinct title, but the repercussions for vertebrate palaeontologists are seismic.  This week has seen the publication in the journal Nature of a paper entitled “The first dinosaur egg was soft”.  Palaeontologists have inferred and implied a great deal about dinosaur reproduction, but the assumption had been that, just like living archosaurs today, the crocodiles and birds, dinosaurs laid hard-shelled eggs.  Dr Mark Norell (American Museum of Natural History) and his co-authors propose that calcified, hard eggshells were not the “default setting” for the Dinosauria, the first dinosaur eggs were soft-shelled like those of a turtle or a snake.  In addition, the researchers conclude that hard-shelled, calcified eggs evolved at least three times independently within the Dinosauria.

Protoceratops Protects a Nest from a Marauding Oviraptorosaur

Protoceratops defends its nest from Oviraptor.

Protoceratops confronts Oviraptor- the egg thief.  An inaccurate portrayal of both the Oviraptorosaur and Protoceratops, but until now, not many had questioned the accuracy of those hard-shelled eggs.

Picture Credit: Everything Dinosaur (from Zalinger)

Unscrambling Dinosaur Eggs

The research led by the American Museum of Natural History in collaboration with colleagues from Yale University, Universidad de Buenos Aires (Argentina), Montana State University, University of Calgary (Canada) and the Museo Paleontológico Egidio Feruglio, Trelew, (Argentina), applied a series of sophisticated geochemical techniques to analyse the eggs of two different non-avian dinosaurs.  They discovered that the eggs resembled those of extant turtles in their composition, microstructure and mechanical properties.

Commenting on the significance of this research, corresponding author Mark Norrell stated:

“The assumption has always been that the ancestral dinosaur egg was hard-shelled.  Over the last 20 years, we’ve found dinosaur eggs around the world.  But for the most part, they only represent three groups – theropod dinosaurs, which includes modern birds, advanced hadrosaurs like the duck-billed dinosaurs and advanced sauropods, the long-necked dinosaurs.  At the same time, we’ve found thousands of skeletal remains of ceratopsian dinosaurs, but almost none of their eggs.  So why weren’t their eggs preserved?  My guess – and what we ended up proving through this study, is that they were soft-shelled.”

Ceratopsian Eggs Were Probably Soft-shelled and This Explains their Rarity in the Fossil Record

The leathery, soft shells of turtle eggs.

The leathery, soft shell of the common snapping turtle (Chelydra serpentina). The eggs of the first dinosaurs were probably very similar.

Picture Credit: Jasmina Wiemann (Yale University)

Calcified Eggshells – An Evolutionary Hedge Against Environmental Stress

The amniotes, a group of tetrapods that includes the mammals, birds and the reptiles all produce eggs with an inner membrane, known as the amnion.  This inner membrane helps to prevent the embryo from drying out.  Some amniotes such as many turtles and squamates (lizards and snakes), lay soft-shelled, leathery eggs, whilst others such as birds and crocodilians produce eggs with a heavily calcified shell.  It is thought that these calcified eggs help to protect the developing embryos inside the eggs from environmental stresses, thus giving the calcified egg layers an evolutionary advantage.  The evolution of the hard-shelled egg is seen as a major step in the global dominance of the amniotes, it leading to greater reproductive success for those members of this group that developed this trait.

The Eggs from a Member of the Theropoda (Domestic Chicken)

Chicken eggs (theropod dinosaur eggs).

Calcified, hard-shelled eggs such as these from a theropod (domestic chicken) were thought to be representative of all Dinosauria eggs.

Picture Credit: Everything Dinosaur

The Fossil Record Shows Bias in Favour of Calcified Eggs

Soft-shelled eggs rarely preserve in the fossil record.  It is very likely that ancient turtles laid soft-shelled eggs, just like their modern counterparts, but such evidence is hard to find in the fossil record.  The same could be inferred for other amniotes, they too might have laid soft-shelled eggs but such evidence would be very difficult to find.  Therefore, studying the transition from soft-shelled eggs to biomineralised, calcified eggs is a substantial challenge for palaeontologists.  As birds and extant crocodilians lay hard-shelled eggs, this type of eggshell has been inferred for all the non-avian dinosaurs.

Protoceratops and Mussaurus

The research team undertook an intensive study of two fossil egg specimens appertaining to two very different dinosaurs – the neoceratopsian Protoceratops (P. andrewsi), known from the Upper Cretaceous Djadokhta Formation exposed in the Gobi Desert of Mongolia and Mussaurus (M. patagonicus) from the Upper Triassic-aged El Tranquilo Formation located in southern Argentina.   The beautifully preserved Protoceratops fossils include a clutch of at least a dozen eggs with embryos, half of which preserve nearly complete skeletons.  Most of the Protoceratops embryos are preserved in a posture in which their vertebrae and limbs are flexed, synonymous with a posture adopted by animals still inside their eggs.

The Protoceratops (P. andrewsi) Nest Fossil

Protoceratops Fossil Nest

The beautifully preserved nest with embryos of Protoceratops andrewsi.

Picture Credit: M. Ellison (American Museum of Natural History)

Some of the skeletal material is obscured by a black and white egg-shaped halo.  In contrast, two potentially recently hatched Protoceratops in the fossil specimen are largely free of this mineral halo.  The research team analysed tiny slices of this halo material using a petrographic microscope.  Further analysis was undertaken using Raman microspectroscopy, where light scattered by a high powered laser provides information on the molecular composition of a sample.  The scientists discovered chemically altered trace residues of the proteinaceous eggshell membrane that makes up the innermost layer of the eggshell of extant archosaurs.  Almost identical results were observed when the Mussaurus specimen was examined.

The Fossilised Remains of the Mussaurus Egg

Mussaurus fossil egg.

The fossilised remains of a Mussaurus.

Picture Credit: Diego Pol (Museo Paleontológico Egidio Feruglio, CONICET)

Comparing Biomineralisation Residue Signatures

The research team which included Diego Pol (Museo Paleontológico Egidio Feruglio CONICET), Darla Zelenitsky (University of Calgary) and Jasmina Wiemann (Yale University) then compared the data from the fossil material to eggshell data from other living amniotes such as turtles, birds, lizards and crocodiles.  They determined that the Mussaurus and the Protoceratops eggs were non-biomineralised and therefore they would have resembled the leathery, soft-shelled eggs of living turtles.

Graduate student Jasmina Wiemann explained:

“It’s an exceptional claim, so we need exceptional data.  We had to come up with a brand-new proxy to be sure that what we were seeing was how the eggs were in life and not just the result of some strange fossilisation effect.  We now have a new method that can be applied to all other sorts of questions, as well as unambiguous evidence that compliments the morphological and histological case for soft-shelled eggs in these animals.”

Creating a “Supertree” to Track Eggshell Evolution

In total, data from 112 extinct and living amniotes was analysed by the research team.  This enabled them to build a “supertree” to track the phylogeny of egg-shell evolution over geological time.  They concluded that the ancestors of the Dinosauria probably produced an egg that lacked a calcified layer, that these animals laid soft-shelled eggs and that the first, true dinosaurs had the same type of egg.  This element of the research suggests that calcified, hard-shelled eggs evolved independently at least three times throughout the Mesozoic era in the Dinosauria, explaining the bias towards eggshells of derived dinosaurs in the fossil record.  The calcified layer of eggshell evolved independently in ornithischian, sauropodomorph and theropod dinosaurs.

Co-author Matteo Fabbri (Yale University) added:

“From an evolutionary perspective this makes much more sense than previous hypotheses, since we’ve known for a while that the ancestral egg of all amniotes was soft.  From our study, we can also now say that the earliest archosaurs, the group that includes dinosaurs, crocodiles and pterosaurs had soft eggs.  Up to this point, people just got stuck using the extant archosaurs – crocodiles and birds to understand dinosaurs.”

Implications for the Pterosauria

This research has implications for the Pterosauria clade.  Pterosaur eggs are exceptionally rare, a fossil of the wukongopterid (Darwinopterus modularis), reveals the outline of a single egg inside the body cavity. The egg confirms that the pterosaur fossil represents a female that was gravid when she died.  More significantly, scientific papers detailing extensive fossil remains associated with the debris from a nesting colony of the pterosaur Hamipterus tianshanensis have been published and the three-dimensionally preserved eggs do resemble the leathery soft-shelled eggs now associated with members of the Dinosauria.

Fossilised Eggs of Hamipterus tianshanensis – Could They have the Same Biomineralisation Profile of Soft-shelled Dinosaur Eggs?

Egg fossils (Pterosaur).

Pterosaur egg fossils (Hamipterus tianshanensis).

Picture Credit: Xinhua/Wang Xiaolin

To read our 2017 blog post about the Hamipterus colony: Hamipterus Nesting Ground Discovery.

To read our recent article about the discovery of a giant soft-shelled egg associated with a marine reptile: It’s Not a Deflated Football, it’s Probably an Egg from a Mosasaur.

Everything Dinosaur acknowledges the assistance of a media release from the American Museum of Natural History in the compilation of this article.

The scientific paper: “The first dinosaur egg was soft” by Mark A. Norell, Jasmina Wiemann, Matteo Fabbri, Congyu Yu, Claudia A. Marsicano, Anita Moore-Nall, David J. Varricchio, Diego Pol and Darla K. Zelenitsky published in the journal Nature.

17 06, 2020

It’s Not a Deflated Football – It’s Probably an Egg from a Mosasaur

By | June 17th, 2020|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Antarcticoolithus bradyi – An Egg from a Giant Mosasaur

A football-sized palaeontological mystery might have been solved.   A strange object found by a research team from Chile whilst exploring the López de Bertodano Formation on Seymour Island, in Antarctica back in 2011, is probably the fossilised remains of a mosasaur egg.  That is the conclusion of a scientific paper published this week in the journal Nature.  The strange object, described as looking like a deflated football was found in Upper Cretaceous (Maastrichtian) deposits and these strata yield the fossils of dinosaurs and early birds, but they are essentially near-shore marine deposits and mosasaur fossils are found in the vicinity.  The massive egg is the largest soft-shelled egg known to science and the second largest egg ever recorded.  Only the enormous, hard-shelled eggs of elephant birds (family Aepyornithidae), that once lived on the island of Madagascar, are larger.

A Scientist Holding the Strange “Deflated Football” – Probably the Egg of a Giant Mosasaur

The largest soft-shelled egg known to science.

The strange object identified as the giant egg from a mosasaur.  It was nicknamed “the Thing” in recognition of the 1982 American science fiction horror film directed by John Carpenter that told the story of an alien life form attacking a base in Antarctica.

Picture Credit: Legendre et al (Universidad de Chile)

One of the scientific paper’s co-authors, David Rubilar-Rogers from Chile’s National Museum of Natural History had been part of the field team that found the fossil.  It remained in the Museum’s fossil collection for years, unstudied and not classified.  Visiting scientists and academics were not able to identify what it was until Julia Clarke from the University of Texas at Austin visited in 2018 and proposed that the specimen represented a giant, soft-shelled egg.

A Thin Eggshell

Microscopy confirmed that the object was indeed an egg, one with a shell five times thinner than that associated with the hard-shelled eggs of elephant birds.  The structure of the fossil was similar to vestigial eggs laid by some snakes and lizards today (lepidosaurs).  These types of eggs are laid but hatch almost immediately, the babies are fully developed and entirely altricial.  Further analysis of the fossil discovered no evidence of an embryo to help confirm identification of the egg-layer, this was an eggshell, the baby having hatched.  However, mosasaurs are lepidosaurs, (Order Squamata) and the scientists propose that the egg was laid by a giant mosasaur.

Photographs, Illustrations and Microscopic Analysis of the Fossil Egg

Photographs, drawings and a microscopic analysis of the fossil egg.

Photographs and illustrations of the fossil egg with (bottom) a microscopic structure analysis of the eggshell layers.  In the illustrations (b, d and f) actual eggshell is shown in dark grey whilst the surrounding matrix is light grey.  Note the scale comparison with a person on the far right.

Picture Credit: Legendre et al

A Massive Egg Laid by a Massive Mosasaur

The scientists, which include lead author Lucas Legendre, of the Department of Geological Sciences (University of Texas at Austin), estimate that the egg would have weighed around 6.5 kilogrammes and it would have measured about 29 cm long when it was laid.  The actual fossil measures 28 cm by 18 cm.  The team compiled a data set comparing the body sizes of living and extinct amniotes to calculate the potential size of the animal that produced the massive egg.  They calculate that the egg was probably laid by a mosasaur that had a length of around 7 metres (excluding the tail).

A Mosasaur Hatching

A hatching mosasaur.

An artist’s impression of the hatching mosasaur emerging from the soft-shelled egg moments after the egg was laid.

Picture Credit: Legendre et al (Universidad de Chile)

A Scale Drawing Showing the Proposed Size of the Female Mosasaur that Laid the Egg

Scale drawing showing the size of the female mosasaur.

Scale drawing showing the female mosasaur, the egg and the size of the hatchling with the fossil specimen.  Scale bar = 1 metre

Picture Credit: Francisco Hueichaleo

The First Fossil Egg from Antarctica

The visibly collapsed and folded fossil specimen represents the first vertebrate egg of any kind to be discovered in Antarctica.  The researchers speculate that the near-shore, marine sediments of the López de Bertodano Formation represent an estuarine environment that linked onto a large, shallow bay.  Vertebrate fossils found on Seymour Island include dinosaur bones and poorly preserved footprints, shorebird and waterfowl fossils as well as the remains of marine reptiles such as elasmosaurs and mosasaurs.

Legendre, a Postdoctoral Fellow at the Department of Geological Sciences, commented:

“Many authors have hypothesised that this was sort of a nursery site with shallow protected water, a cove environment where the young ones would have had a quiet setting to grow up.”

Was the Egg Laid on Land or Was it Laid in the Sea?

Did mosasaur females struggle ashore to lay their eggs in nests like turtles or did they lay vestigial eggs that hatched almost immediately having been laid in the open sea.  The scientific paper does not specifically discuss how mosasaurs reproduced, but there are three competing hypotheses:

1).  Mosasaur females left the water and excavated nests on the beach in which their eggs were deposited.  When the eggs hatched, the young mosasaurs would scuttle down the beach and enter the water.

2). Mosasaurs were ovoviviparous – mosasaur embryos developed inside eggs that were retained inside the mother’s body until they were ready to hatch. This method of reproduction is similar to viviparity, but the embryos have no placental connection with the mother and they receive their nourishment from the yolk sac although some gaseous exchange between the egg and the mother takes place.

Ovoviviparity Reproduction in a Mosasaur

A hypothesis that mosasaurs were ovoviviparous

Ovoviviparity reproduction in mosasaurs.

Picture Credit: Legendre et al (Universidad de Chile)

3).  The female mosasaur remained mostly in the water, which helped to support its body weight, but manoeuvred its body so that it could reverse out of the water and deposits its eggs on the shore.

Although not convinced that mosasaurs laid their eggs on land, co-author of the scientific paper Julia Clarke explained:

“We can’t exclude the idea that they shoved their tail end up on shore because nothing like this has ever been discovered.”

An Artist’s Impression of an Ovoviviparous Marine Reptile

The Seymour Island fossil site could represent a mosasaur nursery.

An ovoviviparous mosasaur lays its egg in the bay and the young mosasaur quickly emerges.

Picture Credit: Legendre et al (Universidad de Chile)

This remarkable egg fossil has been given the oogenus Antarcticoolithus which translates as “late Antarctic stone egg”.

Everything Dinosaur acknowledges the assistance of a media release from the Universidad de Chile in the compilation of this article.

The scientific paper: “A giant soft-shelled egg from the Late Cretaceous of Antarctica” by Lucas J. Legendre, David Rubilar-Rogers, Grace M. Musser, Sarah N. Davis, Rodrigo A. Otero, Alexander O. Vargas and Julia A. Clarke published in the journal Nature.

15 06, 2020

Overoraptor chimentoi On the Road to the Birds

By | June 15th, 2020|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Overoraptor chimentoi – Closer to Birds than Most other “Raptors”

Time for Everything Dinosaur team members to catch up on their reading.  Whilst browsing through the various press releases, emails and news bulletins from around the world, our attention was drawn to the scientific description of a new, gracile “raptor” from the Upper Cretaceous of Argentina.  Named Overoraptor chimentoi, fossils of this 1.3 metre-long, theropod dinosaur were first discovered in 2013 during field work on 90 million-year-old strata associated with the Huincul Formation in the Patagonian province of Rio Negro.  Further fossils were found during excavations in the same area in 2018.  Although fragmentary, the bones of this small dinosaur suggest that it was more closely related to that lineage of dinosaurs that led to the birds than it is to the likes of Velociraptor and other dromaeosaurids.

A Life Reconstruction of a Pair of Overoraptor chimentoi

Overoraptor life reconstruction.

A life reconstruction of a pair Overoraptors.  Although no feather impressions were found in association with the fragmentary fossils, it is very likely that Overoraptor chimentoi had feathers.

Picture Credit: Gabriel Lio

A Very Bird-like Theropod

The fossil record of members of the Eumaniraptora group of dinosaurs known from the southern hemisphere is sparse.  Evidence of those “raptors” that were closely related to that branch of this group that led to the modern birds is even rarer.  At present, (2020), the fossil evidence is limited to the Unenlagiinae (mostly from the Late Cretaceous of Argentina such as Buitreraptor [B. gonzalezorum]) and the bizarre, bird-like Rahonavis (R. ostromi) from the Upper Cretaceous Maevarano Formation of north-western Madagascar.

Overoraptor exhibits a range of anatomical traits.  The feet and legs are very typical of a dromaeosaurid.  There is the second toe “killing claw” associated with the “raptors” and the lower limb bones indicate that this was a fast-running, cursorial predator.  However, the upper limb bones are very different.  The ulna for example, is very robust and long, reminiscent of the upper limb bones of modern birds.

The Fragmentary Fossils of Overoraptor chimentoi

Overoraptor fossil remains.

Tiny but very significant Overoraptor fossil material including unguals.

Picture Credit: Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”

The picture above shows the fragmentary fossils associated with the new species – Overoraptor chimentoi.  The genus name is from the Spanish “overo” which means piebald, a reference to the mixed colour of the fossil bones.  The trivial name honours Roberto Nicolás Chimento who found the first remains.

Close to the Bird Part of the Dinosaur Family Tree

A phylogenetic analysis conducted by the researchers revealed that Overoraptor was closely related to Rahonavis, that roamed Madagascar some twenty million years later.   The analysis suggests that these two dinosaurs are descended from a common ancestor (they form a monophyletic clade).  Together they are stem avialans within the Eumaniraptora, a line of theropods in which some flight-related adaptations of the forelimbs are present in non-flying taxa.

Commenting on the importance of Overoraptor, one of the co-authors of the paper, Fernando Novas (Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”) stated:

“Contrary to what we originally assumed, the Overoraptor is not part of the Unenlagia family, but from another group including a Madagascan species called Rahonavis.”

The discovery of Overoraptor sheds light on the acquisition of flight-related traits in non-avian dinosaurs and on the still poorly known paravian radiation in Gondwana.

The scientific paper: “New theropod dinosaur from the Upper Cretaceous of Patagonia sheds light on the paravian radiation in Gondwana” by Matías J. Motta, Federico L. Agnolín, Federico Brissón Egli and Fernando E. Novas published in The Science of Nature.

7 06, 2020

Two New Transitional Ceratopsids – Knitting Together Horned Dinosaurs

By | June 7th, 2020|Adobe CS5, Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles|0 Comments

Two New Transitional Horned Dinosaurs – Navajoceratops sullivani and Terminocavus sealeyi

In the last few days, a scientific paper has been published that proposes a direct evolutionary link between Pentaceratops and the younger chasmosaurine Anchiceratops.  The idea that there was a link between Pentaceratops (P. sternbergii) which roamed the New Mexico portion of Laramidia around 75.3 million years ago and Anchiceratops (A. ornatus) which lived much further north (Alberta, Canada), between 72 and 71 million years ago, had been proposed for more than two decades.  This newly published paper names two transitional species – Navajoceratops sullivani and Terminocavus sealeyi, plus describes another new ceratopsid, simply named taxon C.  Between them, these new horned dinosaurs help to fill the gap (literally) in chasmosaurine evolution.

Forming Links in an Evolutionary Chain – From Pentaceratops to Anchiceratops

An evolutionary lineage linking chasmosaurines

The two new  horned dinosaurs together with an undescribed taxon form a vital link in the transition of chasmosaurine ceratopsids linking Utahceratops, Pentaceratops and Anchiceratops into an evolutionary lineage.

Picture Credit: Ville Sinkkonen & Denver Fowler

It’s All About the Embayment

The Ceratopsidae in North America during the Late Cretaceous (Campanian and Maastrichtian faunal stages), diversified and evolved into many different forms.  Two great subfamilies emerged the Centrosaurinae and the Chasmosaurinae.  The evolutionary links between these two subfamilies and between the genera associated within each subfamily, has generated a great deal of discussion.  These dinosaurs are famous for their large skulls with their elaborate, extravagant head shields and horns.  Palaeontologists use the differences in the shape, orientation and size of these frills and adornments to determine one species from another.

Although, using the symmetry of the frill of a horned dinosaur to determine a new species can be controversial: Styracosaurus Provides a Head’s up When it Comes to Naming New Ceratopsids.

The problems recently highlighted with the discovery of a Styracosaurus with an asymmetrical skull notwithstanding, authors Dr Denver Fowler of the Badlands Dinosaur Museum and Dr Elizabeth Freedman Fowler (Dickinson State University, North Dakota), propose that these three new chasmosaurines, all from the Kirtland Formation of New Mexico, form a morphological succession between Pentaceratops from the older Fruitland Formation of New Mexico and Anchiceratops from the geologically much younger Horseshoe Canyon Formation of Alberta.

The Closing of the Notch in the Frill of Pentaceratops 

New study links Pentaceratops to Anchiceratops

A newly published scientific paper plots step changes in frill shape that suggests a line of evolutionary descent from Pentaceratops to Anchiceratops via several “transitional genera”.

Picture Credit: Everything Dinosaur

Shape of the Frills Backed by the Stratigraphy

Significantly, the scientists were able to plot a gradual change in the shape of the horned dinosaurs frills, essentially the gradual and successive filling in of a deep notch at the top of the frill (the embayment).  Anchiceratops did not have a notch at the top of its frill and the researchers demonstrate that two new partial skull specimens found in rocks intermediate in age between Pentaceratops and Anchiceratops were also intermediate in shape, showing how the notch in the frill became even deeper through time and eventually closed in on itself, explaining the lack of a notch in Anchiceratops.

Writing in the open access journal PeerJ, the researchers note that this step change in frill shape is observed in chasmosaurines that do not overlap stratigraphically.  This suggests that over hundreds of thousands of years, species evolved from a direct line of descent.  In biology, this is termed anagenesis – the slow and steady evolution of species in a sequence that forms a direct line of evolutionary descent without any obvious branching.

Two New Chasmosaurine Dinosaurs from the Kirtland Formation of New Mexico

Navajoceratops and Terminocavus life reconstructions.

Two new chasmosaurine dinosaurs from the Hunter Wash member of the Kirtland Formation of New Mexico.

Picture Credit: Ville Sinkkonen & Denver Fowler

A Five Million Year Evolutionary Line

The two newly named horned dinosaurs Terminocavus sealeyi and Navajoceratops sullivani along with other chasmosaurine specimens from the Farmington and De-na-zin Members of the Kirtland Formation (Taxon C), form a sequence of horned dinosaur evolution, stretching over five million years from Utahceratops to Pentaceratops and on to Anchiceratops.

Navajoceratops sullivani is named in honour of the Navajo people who are synonymous with New Mexico.  The species name honours the now retired, Dr Robert Sullivan who led the field expedition that resulted in the discovery of the Navajoceratops fossil material.  The name translates as “Sullivan’s Navajo horned face”.

Terminocavus sealeyi translates as “Sealey’s closing cavity”, after fossil collector Paul Sealey who found the holotype and due to the fact that the notch in the skull frill is fully closed.

Holotype Parietal Frills of Terminocavus and Navajoceratops

The parietal frills of Navajoceratops and Terminoscavus.

Holotype specimens (parietal frills) of the two new genera, showing line of evolutionary descent and a not to scale silhouette to represent the actual dinosaur.  Although the specimens are fragmentary, both include the diagnostic posterior border of the parietal which permitted evolutionary comparisons to be made.

Picture Credit: Ville Sinkkonen & Denver Fowler with additional annotation by Everything Dinosaur

An Evolutionary Split

The researchers conclude that fossil material previously assigned to Pentaceratops should be examined once more as it may not represent this taxon.  Furthermore, they suggest that there was a splitting event deep in the evolutionary history of the Chasmosaurinae subfamily, after which the Pentaceratops lineage evolved a progressively deepening of the parietal notch in the frill, in contrast to a sister group, the Chasmosaurus lineage which evolved a progressively shallower notch.  The authors propose that encroachment by the Western Interior Seaway around 85-83 million years ago, effectively cut-off dinosaur populations, with a northern and southern population isolated from each other.  This permitted two distinct lineages of chasmosaurines to evolve.  When the sea retreated around 83 million years ago the two populations were able to mix again.

The isolation of northern and southern dinosaur populations during the Santonian faunal stage as a result of rising sea levels provides an explanatory mechanism.  This mechanism in which high sea level isolated northern and southern dinosaur populations for a period of 1 to 4 million years, lays the foundation for an evolutionary splitting event and provides an explanatory mechanism for the apparent differences between northern and southern dinosaur faunas in the Late Cretaceous of western North America.

Everything Dinosaur acknowledges the assistance of a press release from Dickinson Museum Centre (North Dakota) in the compilation of this article.

The scientific paper: “Transitional evolutionary forms in chasmosaurine ceratopsid dinosaurs: evidence from the Campanian of New Mexico” by Denver W. Fowler and Elizabeth A. Freedman Fowler in PeerJ.

29 05, 2020

Wightia declivirostris – A Terrific Tapejarid Pterosaur

By | May 29th, 2020|Adobe CS5, Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Jawbone Leads to an Isle of Wight Tapejarid Pterosaur

A single, fragmentary jawbone from the upper jaw of a pterosaur found on the Isle of Wight has demonstrated just how diverse and widespread the Tapejaridae family of pterosaurs were.  The fossil bone, a partial premaxilla from the Lower Cretaceous (Barremian) Wessex Formation of Yaverland (Isle of Wight), represents a new species, the first record of a tapejarid pterosaur from the Wessex Formation and one of the oldest examples of this pterosaur family to have been found outside of China.  The flying reptile has been named Wightia declivirostris.

A Life Reconstruction of Wightia declivirostris (Wessex Formation)

Wightia declivirostris from the Isle of Wight

A life reconstruction of the newly described tapejarid from the Lower Cretaceous of the Isle of Wight (Wightia declivirostris).

Picture Credit: Megan Jacobs (University of Portsmouth)

Terrific Toothless Tapejarids

The terrific toothless tapejarids with their reputation for taking head crest development to the extreme, are known from relatively abundant fossil material associated with the Santana and Crato Formations of Brazil.  In addition, several members of the Tapejaridae family are associated with the Jiufotang Formation of China.  However, fragmentary fossils are known from elsewhere in the world such as Spain (Europejara olcadesorum) and a toothless, rather deep lower jaw tip along with other partial bones from the Kem Kem beds of Morocco suggests that these types of flying reptile may have persisted into the early Late Cretaceous.

Two of the authors associated with this scientific paper, Professor David Martill and Roy Smith (both from the University of Portsmouth), recently published a report on the discovery of a north African tapejarid which was named Afrotapejara zouhrii, one of a spate of recent Moroccan pterosaur discoveries.  To read Everything Dinosaur’s article about this: That Fourth Moroccan Pterosaur.  It seems that these fancy-crested, edentulous flying reptiles were much more geographically and temporally diverse than previously thought.

A Typical Illustration of a Tapejarid Pterosaur (Tupandactylus imperator)

Tupandactylus illustration.

A scale drawing of the tapejarid Pterosaur Tupandactylus imperator.  The Tapejaridae are thought to have all sported flamboyant head crests.

Picture Credit: Everything Dinosaur

The Isle of Wight Pterosaur is More Closely Related to Chinese Tapejarids

Amateur fossil hunter John Winch discovered a pterosaur snout near the cliff at Yaverland Point in Sandown Bay, in a fossil plant debris layer.  The unusual shape and thin bone walls suggested that it was from a pterosaur.  The fragment of jaw, although eroded, demonstrates the characteristic downturned tip, with numerous tiny holes (foramina), on the occulsal surface which indicate the presence of minute sensory organs for detecting food.

The Holotype Material Wightia declivirostris

premaxilla of Wightia declivirostris.

The isolated, partial premaxilla of Wightia declivirostris.

Picture Credit: University of Portsmouth

The jaw fragment was passed to palaeontology student at Portsmouth University, Megan Jacobs, who confirmed it was a rare find and definitely pterosaurian.  Analysis of the specimen suggests that Wightia is more closely related to the older and more primitive tapejarid Sinopterus from Liaoning (Jiufotang Formation), than it is to Brazilian tapejarids.  The genus name of this newly described flying reptile honours the Isle of Wight, whilst the species (trivial) name means “slanting beak”, a reference to the typically tapejarid morphology of the partial premaxilla.

Both the Wealden Formation and the geologically younger Vectis Formation on the Isle of Wight have yielded pterosaur specimens, although they tend to consist of highly fragmentary remains.  The discovery of Wightia declivirostris demonstrates how significant the Lower Cretaceous Isle of Wight sediments are to palaeontologists as they try to plot the radiation of different types of flying reptile during the Early Cretaceous.

The scientific paper: “First tapejarid pterosaur from the Wessex Formation (Wealden Group: Lower Cretaceous, Barremian) of the United Kingdom” by David M. Martill,  Mick Green, Roy E. Smith,  Megan L. Jacobs and John Winch published in the journal Cretaceous Research.

24 05, 2020

The Most Dangerous Place and Time in the Cretaceous

By | May 24th, 2020|Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Geology, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

A Comprehensive Guide to the Fossils from the Kem Kem Beds of Eastern Morocco

A team of international researchers have documented the fossil vertebrates associated with the early Late Cretaceous (Cenomanian-Turonian) of the famous Kem Kem beds of eastern Morocco.  They conclude that with the abundance of hypercarnivores such as Spinosaurus, abelisaurids, Carcharodontosaurus and Deltadromeus, several large pterosaurs and a multitude of giant fish and crocodyliforms, no comparable modern terrestrial ecosystem exists with a similar bias toward large-bodied carnivores.

Arguably, the sediments that make up the Kem Kem Group, which is composed of the lower Gara Sbaa and upper Douira formations, represent the most dangerous place and time in the whole of the Cretaceous.

Examples of Theropod Teeth Associated with the Kem Kem Group of Eastern Morocco

Indeterminate theropod teeth from the Kem Kem Group.

Indeterminate theropod teeth from the Kem Kem Group with (H) showing the denticles of (F) and (N) close up view of denticles in (M).  Scale bar equals 2 cm in A-C and I-M whilst 3 cm in D and 5 mm in H and N.

Picture Credit: Ibrahim et al (ZooKeys)

An Ambitious Target

The researchers which included Nizar Ibrahim and Paul Sereno (University of Chicago), David Unwin (University of Leicester), Samir Zouhri (Université Hassan II, Casablanca, Morocco) and David Martill (University of Portsmouth), had an ambitious objective.  The scientists set out to document and summarise the taxonomic status of the fauna that had been described based on the major collections of Kem Kem fossils, as well as to report on the geological age of the various strata and to plot the palaeoenvironment of this part of north Africa during the early stages of the Late Cretaceous.

The team’s comprehensive report has been published with free access in the journal ZooKeys.

The Changing Palaeoenvironment Represented by the Kem Kem Group Sediments

The palaeoenvironment of the Kem Kem Beds.

Schematic paleoenvironmental stages depicting the Kem Kem region during the Cretaceous.  Stages: (1) wide rivers, (2) large river systems with substantial sandbanks, (3) deltaic conditions and (4) rise of the limestone platform.

Picture Credit: Ibrahim et al (ZooKeys)

A Very Dangerous Place to Be (Large Crocodyliforms and Pterosaurs)

The strata have provided evidence of large number of crocodyliforms from one-metre-long insectivores, herbivorous forms to giant predators such as Sarcosuchus imperator.  Several different types of pterosaur are also associated with these deposits.  The first pterosaur remains recovered consisted of isolated teeth collected in the late 1940s and early 1950s but at the time their affinity with the Pterosauria was not recognised.  For an article from Everything Dinosaur about recent pterosaur discoveries from Morocco: Pterosaurs, Pterosaurs and Even More Pterosaurs.

Cervical Vertebra (Bone from the Neck) Ascribed to an Azhdarchid Pterosaur

Third cervical? attributed to an azhdarchid pterosaur.

Near complete third cervical? of an azhdarchid pterosaur from the Kem Kem Group.  FSAC-KK 3088 in (A) ventral, (B) dorsal, (C) right lateral, (D) left lateral, (E) anterior and (F) posterior view.  Scale bar equals 5 cm.

Picture Credit: Ibrahim et al (ZooKeys)

In addition, the first tapejarid pterosaur from Africa was reported recently (Afrotapejara zouhrii), the trivial name honours Professor Samir Zouhri, one of the authors of the extensive review.  To read an article about Afrotapejara: The Fourth New Moroccan Pterosaur – Afrotapejara.

Lots and Lots of Dinosaurs – A Bias Towards the Theropoda

Dinosaurs are strongly associated with these strata, but there is only very fragmentary evidence of Ornithischians including a single, large footprint.  This suggests that bird-hipped dinosaurs were present but, in contrast to most other Cretaceous biotas, they seem very much underrepresented by the fossil material.  Sauropods such as the rebbachisaurid Rebbachisaurus garasbae and titanosaurs are known from both the Douira and Gara Sbaa formations, however, it is theropod specimens that dominate the Dinosauria associated with the Kem Kem Group.  There is evidence to support one medium-sized to large Kem Kem abelisaurid and the discovery of single neck bone (cervical vertebra) indicates a Noasauridae presence.

Huge hypercarnivores such as Carcharodontosaurus saharicus and Spinosaurus aegyptiacus have been reported.  The habitat seemed to have an overabundance of large, carnivorous dinosaurs, although extensive niche partitioning is proposed by several authors.

Perhaps the Most Famous African Dinosaur of them all – Spinosaurus aegyptiacus

Spinosaurus aegyptiacus skull and skeleton.

Skull and skeletal reconstruction of Spinosaurus aegyptiacus.  Scale bars equal 40 cm in A and B, whilst in C the scale bar is 1 metre.

Picture Credit: Ibrahim et al (ZooKeys)

Deltadromeus agilis

One of the most mysterious of all the theropods from Morocco is Deltadromeus agilis.  The taxonomic position of this meat-eater remains controversial.  A partial skeleton (UCRC PV11), was discovered in a coarse sandstone layer in the upper portions of the Gara Sbaa Formation.  The bones were found in association with teeth of the huge sawfish Onchopristis as well as teeth from crocodyliforms.  Fossils associated with D. agilis from eastern Morocco show a resemblance to isolated material recovered from the roughly contemporaneous Bahariya oasis in the Western Desert of Egypt by the German palaeontologist Ernst Stromer.  The Egyptian fossils were assigned to the taxon Bahariasaurus ingens, but the Moroccan and Egyptian material could represent the same genus.  If this is the case, then D. agilis would become a senior synonym of B. ingens.  A single thigh bone from the Bahariya oasis measures 144 cm long.  This suggests that whatever sort of carnivore Deltadromeus/Bahariasaurus was, it was huge.  Some commentators have suggested that based on femur proportions Deltadromeus could have been only slightly shorter (but more lightly built), than Tyrannosaurus rex.

Holotype of D. agilis (A)  and Compared in Size to the Egyptian Femur Specimen (B)

Deltadromeus agilis skeleton reconstruction.

Deltadromeus agilis from Morocco and Egypt.  A (A) revised reconstruction based on UCRC PV11 (B) holotype compared to a large femur (now lost) referred to the genus and species from the Bahariya Formation, Egypt.  Known elements in white.  Scale bars: 1 m.

Picture Credit: Ibrahim et al (ZooKeys)

Sadly, like much of Stromer’s material from the Egyptian expeditions, the femur has been lost.

It is very likely that there were lots of smaller predatory dinosaurs too. Dromaeosaurid teeth have been reported from several localities but bones are exceptionally rare and the only positively identified dromaeosaurid skeletal elements are some foot bones found in Sudan and recovered from Cenomanian-age rocks.

A Predominance of Aquatic Predators

The authors state that the Kem Kem assemblage is dominated by aquatic and subaquatic invertebrates and vertebrates, the majority of which are predators. They suggest that as most of the taxa are exploiting aquatic food resources, then like modern marine food chains, the habitat is predator dominated.  As to the overabundance of carnivorous dinosaurs compared to plant-eating ones, the researchers conclude that this is not due to sampling bias or preservation factors.  Large theropods in the food web were supported primarily in the case of Spinosaurus or secondarily in the case of the terrestrial carnivores by the huge amount of aquatic protein sources.

The dissected deltaic plain and nearshore environments may have enhanced aquatic resources while limiting, or rendering patchy areas of available vegetation for large-bodied dinosaurian herbivores. Hence the bias towards carnivores when it comes to assessing the fossilised remains of dinosaurs from the Kem Kem beds.

The Presence of So Many Carnivores could be Explained by the Abundance of Aquatic Food Sources such as Small Fish

Serenoichthys kemkemensis from the Douira Formation.

Serenoichthys kemkemensis from the Douira Formation.  Scale bar equals 1 cm.  The abundance of predators could be explained by the large amount of aquatic protein sources present in the environment.

Picture Credit: Ibrahim et al (ZooKeys)

The scientific paper: “Geology and paleontology of the Upper Cretaceous Kem Kem Group of eastern Morocco” by Nizar Ibrahim, Paul C. Sereno, David J. Varricchio, David M. Martill, Didier B. Dutheil, David M. Unwin, Lahssen Baidder, Hans C. E. Larsson, Samir Zouhri and Abdelhadi Kaoukaya published in ZooKeys.

22 05, 2020

13,000 Edmontosaurus Bones and Counting

By | May 22nd, 2020|Adobe CS5, Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Geology, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Massive Edmontosaurus Bonebed Provides Data on Dinosaur Decomposition

A team of scientists have produced a study mapping an astonishing dinosaur bonebed that has so far yielded a staggering total of 13,000 individual fossil elements.  In truth, the bonebed contains many more fossils, but individual dinosaur teeth, ossified tendons and other fragmentary elements under five centimetres in length have not been counted.  The site is located in eastern Wyoming and consists almost entirely of the preserved remains of a single type of dinosaur, a hadrosaur (Edmontosaurus annectens).  The bonebed study has not only provided a great deal of information about this duck-billed dinosaur but shed light on how death assemblages consisting of a large number of corpses are formed and how various bones of differing sizes might be transported before final deposition.

Dinosaur Bonebeds such as the Danek Edmontosaurus regalis Bonebed in Edmonton Have Yielded Thousands of Fossil Bones

Excavating an Edmontosaurus.

The Danek Edmontosaurus bonebed is typical of an Edmontosaurus-dominated bonebed which are widespread in the Upper Cretaceous (Campanian to Maastrichtian) of western North America).

Picture Credit: Victoria Arbour

The Hanson Ranch Bonebed (Lance Formation)

Writing in the on-line, open access journal PLOS One, the scientists which include Keith Synder of the Biology Dept. of the Southern Adventist University, Tennessee, document the taphonomy and depositional history of an extensive E. annectens bonebed known as Hanson Ranch, in the Lance Formation of eastern Wyoming.  The bonebed includes five main quarries and three exploratory quarries.  Approximately 13,000 elements including around 8,400 identifiable bones, have been recovered in 506 square metres of excavated area in twenty years (1996-2016).

Virtually all the fossils are located within a fine-grained (claystone to siltstone) bed that has a maximum depth of two metres.

Mapping the Stratigraphy of the Main Bonebeds at the Hanson Research Station (Wyoming)

The Stratigraphy of the Hanson Research station.

Local stratigraphy associated with the main bonebeds at the Hanson Research station.  The green arrow indicates position of main bonebed.

Picture Credit: Synder et al (PLOS One) with additional annotation by Everything Dinosaur

An Excellent State of Preservation

Almost all the fossils recovered from the site exhibit exquisite preservation with little or no abrasion, breakages or signs of weathering prior to deposition.  All the material is disarticulated and scattered although over a relatively confined area.  This evidence in conjunction with analysis of the sediments associated with the fossils indicates that the bones were moved and buried after a period of initial decay and decomposition of the Edmontosaurus carcasses.

Mapping the Distribution of Fossil Bones in a Bonebed

A map showing the distribution of fossil material in an Edmontosaurus bonebed.

A map showing typical disarticulated fossil bone distribution in a bonebed.

Picture Credit: Synder et al (PLOS One)

Gaining a Better Understanding of Edmontosaurus Biostratigraphy

The thousands of fossil bones represent mainly adult or sub-adult specimens.  Due to the huge number of fossils associated with the Hanson Research site, the scientists have been able to gain a deeper understanding of Edmontosaurus biostratigraphy including how elements from the skeleton can be transported over distances prior to deposition.  The most abundant fossil bones are ischia, pubes, scapulae, ribs and limb bones.  In contrast, vertebrae, ilia and chevrons are rare.

When it comes to cranial material lower jaw bones (dentaries), nasals, quadrates and jugals are prevalent whilst premaxillae (upper jaw bones), predentaries and bones associated with the braincase are seldom found.  The researchers suggest that following decay and break-up of the carcase, water action sorted and removed the articulated sections such as the backbone and the smaller bones such as the digits and toes, before, or at the same time, the remaining material was swept up in a subaqueous debris flow that created the final deposit.

The scientists suggest that similar processes may have been at work that created the other hadrosaurid-dominated Upper Cretaceous bonebeds associated with such geological formations as Hell Creek, Two Medicine, Horseshoe Canyon, Prince Creek as well as the Lance Formations of western North America.  It is noted that there is a remarkably similar skeletal composition among the fossil bonebeds studied.  It is also noted that there is a significant correlation between the hadrosaurid bonebeds and fluvial assemblages representing thanatocoenosis* events seen with modern-day vertebrate death assemblages.

Thanatocoenosis* Explained

Thanatocoenosis refers to a site where a collection of fossils representing a variety of organisms are found together.  Such sites are often referred to as death assemblages.  The organisms represented at the location may not have been associated in life, but their remains have been transported and deposited together thus forming a fossil bed composed of an extensive amount of fossilised material.

Not All of the Dinosaur Fossils are Edmontosaurus

The bonebed can be described as monodominant as the vast majority of the fossil material found can be assigned to just one species Edmontosaurus annectens.  Non-dinosaurian terrestrial taxa identified include mammals and squamates along with the remains of many aquatic creatures such as crocodiles, turtles, gar and other fishes and numerous molluscs.  Some other types of plant-eating dinosaur are represented notably, ceratopsids, pachycephalosaurs, nodosaurs and members of the family Thescelosauridae.  Numerous shed theropod teeth are also associated with this location.  Everything Dinosaur will post up a separate article detailing one rather special theropod fossil associated with a quarry close to the Hanson Research station in the near future.

A Life Reconstruction of the Hadrosaurid Edmontosaurus

Wild Safari Prehistoric World Emontosaurus model.

The new for 2020 Wild Safari Prehistoric World Edmontosaurus dinosaur model.

Picture Credit: Everything Dinosaur

The scientific paper: “Over 13,000 elements from a single bonebed help elucidate disarticulation and transport of an Edmontosaurus thanatocoenosis” by Keith Snyder, Matthew McLain, Jared Wood and Arthur Chadwick published in PLOS One.

20 05, 2020

The First Elaphrosaurine Theropod Reported from Australia

By | May 20th, 2020|Adobe CS5, Dinosaur and Prehistoric Animal News Stories, Dinosaur Fans, Main Page, Palaeontological articles, Photos/Pictures of Fossils|0 Comments

Curious Cervical Leads to Startling Conclusion

Think of a theropod dinosaur and a ferocious carnivore with a large head and big teeth probably comes to mind.  However, the Theropoda is an extremely diverse clade within the Dinosauria, not all of them were big, particularly ferocious or even had teeth.   One group the elaphrosaurines, were very bizarre indeed and the discovery of a single neck bone in Victoria has led to the conclusion that these strange, light-weight dinosaurs distantly related to Carnotaurus, roamed Australia in the Early Cretaceous.

A Life Reconstruction of the Australian Elaphrosaurine

Life reconstruction of the elaphrosaur from Victoria.

A life reconstruction of the first elaphrosaur from Australia.

Picture Credit: Ruairdh Duncan (Swinburne University of Technology, Victoria)

From the Lower Cretaceous of Australia

Volunteer Jessica Parker discovered a 5-centimetre-long bone whilst helping out at the annual Dinosaur Dreaming excavation near Cape Otway, Victoria (2015).  The sediments at the site, known as Eric the Red West, date from the late Albian faunal stage of the Lower Cretaceous and are part of the Eumeralla Formation.  At first, the bone identified as a cervical vertebra (neck bone), was thought to have come from a pterosaur.

Intriguingly for Swinburne University palaeontologist Dr Stephen Poropat and PhD student Adele Pentland, once the fossil specimen had been prepared it became clear that this was not a bone from the middle portion of the neck of a flying reptile.

Dr Poropat explained:

“Pterosaur neck vertebrae are very distinctive.  In all known pterosaurs, the body of the vertebra has a socket at the head end, and a ball or condyle at the body end.  This vertebra had sockets at both ends, so it could not have been from a pterosaur.”

The Cervical Vertebra – Evidence of Australia’s First Elaphrosaur

The cervical vertebra (elaphrosaur0.

The five-centimetre-long bone identified as a middle cervical from an elaphrosaur.

Picture Credit: Dr Stephen Poropat

Geologically Much Younger Than Most Elaphrosaurines

The taxonomic affinity of the subfamily Elaphrosaurinae within the Theropoda remains controversial.  A number of authors have placed this little-known group, characterised by their small, light, graceful bodies, tiny heads, long necks and reduced forelimbs within the Noasauridae family, which means that they are distantly related to abelisaurids such as Ekrixinatosaurus, Majungasaurus and Carnotaurus.

Most elaphrosaurs are known from the Late Jurassic, but this new elaphrosaur from Australia, lived some forty million years later. Only Huinculsaurus (H. montesi), from the Cenomanian/Turonian (early Late Cretaceous), of Argentina is geologically younger, than the Australian fossil remains.

The Fossil Find Location, Typical Elaphrosaurine Body Plan and Placing the Fossil Find in a Chronological Context

Elaphosaur timeline and typical body plan.

A silhouette of the elaphrosaur with a map showing fossil location and a timeline showing elaphrosaurine chronology.  The newly described elaphrosaurine from Victoria is geologically the second youngest member of this group known.

Picture Credit: Poropat et al (Gondwana Research)

A Dinosaur of the Polar Region

The discovery of this single, fossilised neckbone adds support to the idea that the elaphrosaurines were geographically and temporally much more widespread than previously thought.  The similarity of these dinosaurs to the much better-known ornithomimosaur theropods (bird mimics), could help to explain why few other Cretaceous elaphrosaur specimens have come to light. Fossil material may have been found but misidentified as representing ornithomimids.

As the Cape Otway location would have been situated much further south during the Early Cretaceous (110-107 million years ago), at around a latitude of 76 degrees south, this implies that elaphrosaurines were capable of tolerating near-polar palaeoenvironments.

Recently, Everything Dinosaur wrote a post about the discovery of noasaurid from an opal mine close to Lightning Ridge (New South Wales).  Noasaurids and elaphrosaurines were related, most scientists classifying them as different branches within the Abelisauroidea.  Coincidentally, the New South Wales noasaurid was identified from a single cervical vertebra too.  Both it and the Cape Otway elaphrosaurine dinosaur have not been assigned to any genus, but both fossils are likely to represent new species.

To read Everything Dinosaur’s article about the recently discovered noasaurid from New South Wales: Noasaurids from Australia.

The scientific paper: “First elaphrosaurine theropod dinosaur (Ceratosauria: Noasauridae) from Australia — A cervical vertebra from the Early Cretaceous of Victoria” by Stephen F. Poropat, Adele H. Pentland, Ruairidh J. Duncan, Joseph J. Bevitt, Patricia Vickers-Rich and Thomas H. Rich published in Gondwana Research.

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