The Rebor Deinonychus Trio “Cerberus Clan” is Coming to Everything Dinosaur

The Rebor “Cerberus Clan”, the third part of the Acrocanthosaurus/Tenontosaurus diorama is due to arrive at Everything Dinosaur’s warehouse in the next ten days or so.  The trio of raptors “Deinonychus antirrhopus“, nick-named Shoot, Tooth and Thrill (we think), completes the “Hercules and the Ceryneian Hind” model set, all the bases are designed to interlock to provide a seamless prehistoric scene that features a total of five dinosaurs.

Guess Who’s Coming to Dinner?

The trio of three “raptors” from Rebor.

Picture credit: Rebor/Everything Dinosaur

Deinonychus antirrhopus – Changing Perceptions

It could be argued that the scientific description of Deinonychus antirrhopus by the American palaeontologist John Ostrom in 1969, helped change the perception of the Dinosauria.  Ostrom, portrayed this predatory dinosaur as a very active, bird-like animal, helping to revolutionise thinking with the view that many dinosaurs had similar metabolic rates to mammals and birds gradually displacing the idea that dinosaurs were sluggish, dim-witted and slow-moving.

The new Rebor trio certainly echo much of Ostrom’s work, these dinosaurs are depicted as fast-running, pack hunters capable of challenging a larger meat-eating dinosaur over dining rights.

Around a dozen near complete specimens have been discovered, including remains of Deinonychus individuals next to Tenontosaurus (a large, herbivorous dinosaur), a rare example of predator and prey being found together.  It was these fossils that helped to inspire this particular Rebor sculpt.

Deinonychus and Acrocanthosaurus

At Everything Dinosaur, we are not aware of any Deinonychus fossil material being found in the same strata as Acrocanthosaurus (A. atokensis) fossil remains.  However, both these theropods lived in North America during the middle Albian , although D. antirrhopus fossil material is associated with the Upper Cloverly Formation and the much rarer Acrocanthosaurus fossils, are associated with the Antlers Formation of Oklahoma and the Twin Mountains Formation of Texas.

The Trio of Rebor Models (Hercules, Ceryneian Hind and the Cerberus Clan)

The Rebor Acrocanthosaurus, Tenontosaurus and Deinonychus diorama.

Picture credit: Rebor/Everything Dinosaur

Each item is sold separately, to see the complete range of Rebor models available at Everything Dinosaur: Rebor Dinosaur Figures and Models.

The Rebor Deinonychus Figures

With individuals measuring more than three metres in length, a pack of Deinonychus would have made a formidable and frightening sight, even a giant, eleven-metre-long, fully-grown Acrocanthosaurus might have been well advised to steer well clear of them.

Fine Details on the Rebor “Raptor” Models

The Rebor “Cerberus Clan”.

Picture credit: Rebor/Everything Dinosaur

The picture above shows the three Deinonychus dinosaur models in the Rebor “Cerberus Clan” set.  Each one is in a different pose and has different colouration.

Everything Dinosaur Comments

A spokesperson from Everything Dinosaur commented:

“We are very excited to hear that the Rebor trio of Deinonychus models are ready for shipping.  The first of these model sets should arrive before Christmas, but it is unlikely, that given the delays in post at this time of year, that we will be able to get out orders to customers in time for the big day.  However, what a fantastic way to welcome in the New Year!”

An Early Concept Illustration of the Rebor “Cerberus Clan” Models

The Rebor “Cerberus Clan” – concept illustration.

Picture credit: Rebor

Stock is expected in about ten days or so.

If you would like to see the range of dinosaur and prehistoric animal figures in stock at Everything Dinosaur: Dinosaur Models and Prehistoric Animal Figures.

Didelphodon Study Suggests a Powerful Bite

Research published in the academic journal “Nature Communications” suggests that dinosaurs in the Late Cretaceous, did not have it all their own way when it came strong teeth and powerful jaws.

This new study, conducted by scientists from the Burke Museum and the University of Washington, indicates that the stem metatherian Didelphodon vorax may have had the strongest bite relative to its body size of any known mammal.  The team estimate that D. vorax could have weighed in excess of five kilogrammes and probably would have attacked and consumed small dinosaurs.

However, microscopic analysis of the wear patterns on fossil teeth suggest that Didelphodon was not entirely carnivorous, it seems to have consumed a wide variety of food items including plants, but those robust jaws and specialised teeth were capable of crushing hard body parts such as the shells of snails and the bones of small dinosaurs.

Didelphodon with Durophagous Jaws

The research team suggest that Didelphodon may well have been durophagous (jaws and teeth adapted for crushing and coping with bones and other tough body parts, such as mollusc shells, bones and the exoskeletons of arthropods).

Didelphodon vorax Probably Ate Dinosaurs

Ancient marsupial ancestor may have attacked and eaten small dinosaurs.

Picture credit: Misaki Ouchida

Metatherians

Metatherians are the pouched mammals, the marsupials.  Didelphodon is believed to be distantly related to extant marsupials such as kangaroos, koalas and opossums.  Three genera have been named, all from fragmentary fossils found in North America.  The Didelphodon genus was erected in 1889 by the distinguished American palaeontologist Othniel C. Marsh.

Ironically, it is very likely that small isolated bones and teeth representing many different types of Late Cretaceous mammal may have been overlooked by field teams working for Marsh as they strove to uncover large dinosaur bones in a bid to overshadow the exploits of Marsh’s bitter rival, Edward Drinker Cope.

Described as being roughly the size of a badger, but with the skull reminiscent of the extant marsupial the Tasmanian Devil (Sarcophilus harrisii), very little post-cranial Didelphodon material has been formally described.  A specimen has been recently recovered from the Hell Creek Formation, it is likely that a more accurate picture of, what would have been one of the largest mammals of the Late Mesozoic, will emerge.

For the moment, there is a debate amongst palaeontologists as to whether Didelphodon was a semi-aquatic mammal with a lean, otter-like body or whether it was entirely terrestrial.

An Illustration of Didelphodon vorax

An illustration of Didelphodon vorax.

A Predator/Scavenger of the Hell Creek Formation

The research team, which included lead author, Dr Gregory Wilson (Burke Museum), examined four specimens from the Hell Creek Formation, namely a near complete skull, the most complete fossil skull of Didelphodon found to date, a partial snout and two upper jaw bones (maxillae).

All four specimens had been assigned to D. vorax based on an analysis of the cheek teeth that were present.  These fossils enabled the team to estimate the strength of this mammal’s bite and the results, coupled with a study of teeth morphology, suggest that Didelphodon occupied a durophagous predator/scavenger niche in the Hell Creek ecosystem.  Pound for pound, Didelphodon had a stronger bite than a Hyena!

For models and replicas of prehistoric animals from the Hell Creek Formation: PNSO Dinosaurs and Extinct Prehistoric Creatures.

Some of the Fossil Specimens Used in the Study

The partial snout (UWBM 94084) and the near complete skull (NDGS 431) of Didelphodon used in the bite force study.

Picture credit: Burke Museum

Didelphodon vorax

Dr Wilson stated:

“What I love about Didelphodon vorax is that it crushes the classic mould of Mesozoic mammals.  Instead of a shrew-like mammal meekly scurrying into the shadows of dinosaurs, this badger-sized mammal would have been a fearsome predator on the Late Cretaceous landscape – even for some dinosaurs.”

Most Cretaceous mammals are known from only isolated teeth and fragments of jaw.  However, with a nearly complete skull, part of the North Dakota Geological Survey State fossil collection, the scientists were able to examine in more detail the phylogenetic relationship between Didelphodon and modern-day marsupials.

The team concluded that marsupials most probably evolved in North America, as part of a Late Cretaceous diversification of the Mammalia and later dispersed to South America.  The Cretaceous extinction event that saw the demise of the Dinosauria and pterosaurs also resulted in the near extinction of the metatherian mammals.

These stem marsupials became larger and evolved to take advantage of different ecological niches before a decline in the North American metatherian diversity from the Late Campanian through to the Maastrichtian faunal stages of the Late Cretaceous, before these types of mammals died out almost entirely in North America at the end of the Mesozoic.

Marsupials survived in South America and marsupial diversity and evolution shifted to this part of the Americas.

A Closer View of the Snout of Didelphodon

A close up view of the snout of Didelphodon, one of four fossils used in a new study into Late Cretaceous metatherians.

Picture credit: Burke Museum

Marsupials from Hell Creek Formation

Marsupials seem to be the dominant types of mammal in the Hell Creek Formation, approximately sixty species have been described, Didelphodon being the largest.  An analysis of the snout bones including the premaxilla suggests that this mammal had a highly mobile snout, a feature lost in most later metatherians.

Fearsome Jaws and a Strong Skull (D. vorax)

Line drawings (various views) of the skull of Didelphodon vorax.

Picture credit: Wilson et al (Nature Communications)

The picture above shows the reconstructed jaws and skull of D. vorax (scale bar = 1 cm).  Picture (a) shows the anterior view (view from the front), whilst (b) shows the posterior view (view from the rear).  A view from the top down (dorsal) is (c), whilst (d) is a drawing viewed from underneath (ventral view).  Drawing (e), shows the skull and jaws as viewed from the right (right lateral view).

Although, these four specimens involved in the study have done much to improve our understanding of the skull morphology of Didelphodon, the areas not preserved in the actual fossils include the lower incisors, some upper incisors and parts of the back of the skull.  Some suture lines remain unclear, these are shown in the above illustrations as dashed lines.

Commenting on the significance of this new insight into Late Cretaceous mammal evolution, Dr Wilson said:

“Our study highlights how, despite decades of palaeontology research, new fossil discoveries and new ways of analysing those fossils can still fundamentally impact how we view something as central to us as the evolution of our own clade, mammals.”

The scientific paper: “A Large Carnivorous Mammal from the Late Cretaceous and the North American Origin of Marsupials”, published in Nature Communications.

Visit Everything Dinosaur’s award-winning website: Everything Dinosaur.

Dinosaur Tail Preserved in Mid-Cretaceous Amber

A team of international scientists including Lida Xing (University of Geosciences, Beijing), Phil Currie (University of Alberta), Michael Benton (University of Bristol), Ryan McKellar (Royal Saskatchewan Museum) and Xing Xu (Institute of Vertebrate Palaeontology and Palaeoanthropology) have published a paper describing the discovery of a partial dinosaur tail preserved in amber.

The Dinosaur Tail Segment Preserved in Burmite (Amber from Myanmar)

The exquisitely preserved dinosaur tail in amber.

Picture credit: R. McKellar/Royal Saskatchewan Museum

 It is the first time that non-avian theropod remains have been found preserved in amber and this remarkable fossil find may help scientists to uncover more information about dinosaur biology and the evolution of plumage.

Views of the Preserved Dinosaur Tail

Dinosaur tail preserved in amber.

Picture credit: Elsevier Ltd (Current Biology)

The picture above shows various photomicrographs of the plumage of the fossilised tail (specimen number DIP-V-15103).  The exquisite details of the individual feathers and the barbs and barbules that help to “zip” the feather together can be made out.  This fossil find confirms the theory long held by evolutionary biologists that the branching structures of feathers evolved before a modern-looking rachis (central shaft).

Photomicrographs of DIP-V-15103 Plumage

(A) Pale ventral feather in transmitted light (arrow indicates rachis apex) – scale bar = 1 mm.

(B) Dark-field image of (A), highlighting structure and visible colour – scale bar = 0.5 mm.

(C) Dark dorsal feather in transmitted light, apex toward bottom of image – scale bar = 0.5 mm.

(D) Base of ventral feather (arrow) with weakly developed rachis, scale bar = 0.5 mm.

(E) Pigment distribution and microstructure of barbules in (C), with white lines pointing to pigmented regions of barbules, scale bar 0.5 mm.

(F–H) Barbule structure variation and pigmentation, among barbs, and ‘rachis’ with rachidial barbules (near arrows); images from apical, mid-feather, and basal positions respectively, scale bars 0.25 mm.

An analysis of the preserved pigmentation signatures suggests that this little dinosaur’s tail was a light chestnut colour with a paler, or possibly white underside.

Definitely a Dinosaur

Lida Xing, the lead author of the study, discovered the remarkable fossil at an amber market in Myitkina (Kachin State, northern Myanmar).  The 99-million-year-old amber had already been polished for jewellery and the retailer had thought that the “furry looking” object visible inside the polished piece was plant remains.

However, on closer inspection, it turned out to be the tail of a feathered dinosaur about the size of a sparrow.  It was then a case of detective work, with Lida Xing eventually tracking down the amber miner who had originally found the specimen.  Once the team had an idea of the location of the fossil find, they could begin the process of analysing the remains, knowing that what was inside had lived during the Middle Cretaceous.

Scanning electron microscopy permitted the team to view the skeletal structure of the tail.  The caudal vertebrae (tail bones) are not fused into a stiff rod, nor are the vertebrae compressed into a pygostyle (the last five tail bones much reduced and fused into a plate of bone, the pygostyle, birds more advanced than Archaeopteryx of the Late Jurassic had a pygostyle), as in extant birds and their close relatives.  This tail was long and flexible with keels of feathers running down each side – the tail of a small dinosaur.

Treasures Preserved in Burmite

Earlier this year, Everything Dinosaur reported upon the discovery of bird wings preserved in burmite (the term used to describe amber from Myanmar, which was formerly called Burma), the researchers, many of whom collaborated on the study of the dinosaur tail, identified the tiny wings of a hatchling bird that had become trapped in sticky tree resin.

The wing fossil came from a bird that was a member of the Enantiornithes group of birds.  Enantiornithes are the most widespread, diverse and abundant type of bird known from the Mesozoic.  Like the more primitive Confuciusornithids, these birds had pygostyles, the long sinewy tail preserved in this piece of amber strongly suggests that this is a piece of a dinosaur, albeit a small piece the tail measures just 36.73 mm long.

Views of the Dinosaur Tail Preserved in Amber

Photomicrographs and SR X-Ray μCT reconstructions of the specimen (DIP-V-15103).

Picture credit:  Elsevier Ltd (Current Biology)

To read Everything Dinosaur’s earlier article (June 2016), about the bird wings preserved in amber: Bird Wings Preserved in Amber from Myanmar.

The picture above shows photomicrographs and synchrotron radiation X-ray images of the tail.

(A) Dorsolateral overview (view from the top) – note the insect remains also found within the amber nodule, burmite has provided palaeontologists with a large number of insect specimens to study.  Scale bar = 5 mm.

(B) Ventrolateral overview (view from underneath) with decay products (bubbles in foreground, staining to lower right).  Scale bar = 5 mm.

(C) Caudal exposure of tail showing darker dorsal plumage (top), milky amber, and exposed carbon film around vertebrae (centre).  Scale bar = 2 mm.

(D–H) Reconstructions focusing on dorsolateral, detailed dorsal, ventrolateral, detailed ventral, and detailed lateral aspects of tail, respectively, showing layout of the vertebrae and the orientation of feathers.  Scale bar in (D) and (F) = 5 mm.  Scale bar in (E), (G) and (H) = 2 mm.

Asterisks in (A) and (C) indicate carbonised film (soft tissue) exposure.  Arrows in (B) and (E)–(G) indicate shared landmark, plus bubbles exaggerating rachis dimensions; brackets in (G) and (H) delineate two vertebrae with clear transverse expansion and curvature of tail at articulation.  Abbreviations for feather rachises: d, dorsal; dl, dorsalmost lateral; vl, ventralmost lateral; v, ventral.

Vestiges of Organic Remains from a Dinosaur Tail

Chemical analysis of the carbonised soft tissues where the tail was exposed at the surface of the amber nodule indicate traces of ferrous iron Fe+2, this suggests that the specimen may contain vestiges of haemoglobin, a relic of the blood of a dinosaur.  It had been rumoured that other remains of vertebrates had been found in burmite, but these pieces quickly found their way into the hands of private collectors and they were lost to science.  This piece remains unique in that preserved dinosaur remains in amber have come to the attention of the scientific community and a study has been undertaken.

How Did it Get There?

Dr Ryan McKellar (Royal Saskatchewan Museum), stated that the dinosaur tail was not dried out or desiccated when it was trapped in the tree resin.  This suggests that a little dinosaur became stuck in the resin when it was still alive.  Co-author, Professor Mike Benton (Bristol University) commented:

 “It’s amazing to see all the details of a dinosaur tail – the bones, flesh, skin, and feathers – and to imagine how this little fellow got his tail caught in the resin, and then presumably died because he could not wrestle free.”

The resin was presumably coming out of a wound in a coniferous tree, either running down the truck or lodging in a branch.  This suggests that this little dinosaur may have been arboreal, a tree dweller.  It has long been thought that there were a large number of small types of theropod dinosaur, but the fossil record for such small, forest dwelling reptiles is virtually non-existent.

A spokesperson from Everything Dinosaur stated:

“It is likely that there were many different types of insectivorous theropod dinosaur, inhabiting woodland habitats, but their delicate bones and the fact that forest corpses have a very limited fossil preservation potential, greatly reduces the chances of palaeontologists being able to study their remains.  These types of dinosaurs are likely to be severely underrepresented in the fossil record.”

What Sort of Dinosaur?

Although feathers have been found preserved in amber before, the lack of skeletal remains associated with them frustrated scientists when it came to identifying what sort of creature the feathers belonged to.  However, in this case, with the tail segment and its preserved caudal vertebrae, the researchers can confidently assign this specimen to the Dinosauria, but what type of dinosaur was it?

An Artist’s Reconstruction of the Little Feathered Dinosaur

An illustration of the feathered dinosaur, about to become stuck in amber.

Picture credit: Cheung Chung-Tat

Arboreal Dinosaurs

In the artist’s reconstruction, the dinosaur is depicted as a ground dwelling animal, however, team members at Everything Dinosaur don’t rule out the idea of an arboreal dinosaur becoming stuck in the tree resin. A spokesman for the Cheshire based company explained:

“A number of dinosaurs show adaptations for climbing indicating that they were at least, partially arboreal.  You would have been more likely to have encountered tree resin on a resin producing tree such as a conifer and whilst we can’t completely rule out the idea that a ground dwelling dinosaur was unlucky enough to become trapped in amber, the context of this fossil raises the possibility that indeed, a number of dinosaurs lived in trees, after all, that would be one way of keeping out of the way of terrestrial predators.”

The spokesperson added:

“It is tantalising given what the amber fossil shows, but it could be speculated that this little dinosaur, if arboreal, could have been a glider or may be even capable of powered flight.”

As for honing the specimen down to a specific genus or even a family, that is quite a challenging task.

Examining the Feathers on the Dinosaur Tail

The shape of the feathers are different from a number of known feathered dinosaurs.  For example, the dromaeosaurid Sinornithosaurus has a reduced rachis and long, naked, filamentous feather barbs.  The plumage on specimen DIP-V-15103 also contrasts with the therizinosaurid Beipiaosaurus.  The researchers conclude that it was probably bipedal and this dinosaur has been assigned to the Coelurosauria clade, a sub-group of the Theropoda that includes the tyrannosaurids, compsognathids, the ornithomimids and the “raptors”.

The scientific paper: “A Feathered Dinosaur Tail with Primitive Plumage Trapped in Mid-Cretaceous Amber” published in the journal “Current Biology”.

Visit Everything Dinosaur’s website: Everything Dinosaur.

For Coelophysis Variety Might Have Been the Spice of Life

Scientists from Virginia Tech University have concluded that early dinosaurs had a wide variety of growth patterns, a trait that may have helped species survive extinction events ultimately assisting the Dinosauria to establish themselves as the dominant, large terrestrial fauna.  The study, published in the academic journal “The Proceedings of the National Academy of Sciences”, focuses on one early theropod, Coelophysis (pronounced: See-low-fy-sis), and the scientists conclude that a single dinosaur species contained a huge amount of diversity in terms of the size that the animals grew to.

Studying Coelophysis

This sets dinosaurs apart from birds, which tend to be much more uniform in terms of their growth rates and sizes within a single species.  A species that contained a broad range of different sized individuals may have had an advantage during hard times or when a sudden catastrophe occurred.  This ontogenetic variation may have helped dinosaurs like Coelophysis survive the harsh environment at the end of the Triassic some 210 to 201 million years ago, a time when a large number of other terrestrial reptile species became extinct.

Study of the Theropod Coelophysis May Provide a Clue to the Success of Dinosaurs

A flock of Coelophysis descend on a waterhole (Ghost Ranch).

Picture credit: Matt Celeskey

A Race for Supremacy Across Pangaea

The end Permian extinction event devastated terrestrial ecosystems and the early dinosaurs rapidly evolved and radiated to take advantage of vacated ecological niches.  During the Triassic, a wide variety of land animals competed with each other – cynodonts, dicynodonts, rauisuchids, phytosaurs and dinosaurs.  Scientists have put forward several theories as to why the Dinosauria eventually rose to become the dominant megafauna.  This new research, conducted by Christopher Griffin and Sterling Nesbitt (Department of Geosciences, Virginia Tech), looked at the variation in growth patterns in a mass death fossil assemblage of Coelophysis, a flock of fast-running, carnivorous dinosaurs that died together in a flood some 208 million years ago, in present-day New Mexico (Ghost Ranch).

Hundreds of individuals were buried together, ranging from youngsters, to sub-adults to fully grown animals.  In total, the researchers examined the fossilised remains of 174 specimens, housed in museums across America.

An Illustration of the Head of Coelophysis

Coelophysis of the Late Triassic.

Picture credit: Everything Dinosaur

Explaining their results, lead author, Christopher Griffin stated:

“We found that the earliest dinosaurs had a far higher level of variation in growth patterns between individuals than crocodiles and birds, their closest living relatives.  Not only were there many different pathways to grow from hatchling to adult, but there was an incredible amount of variation in body size, with some small individuals far more mature than some larger individuals, and some large individuals more immature than we would guess based on size alone.”

Ontogenetic Sequence Analysis

A technique called ontogenetic sequence analysis was used to assess the growth of the Coelophysis fossil assemblage, this data set was compared to two extant birds and one crocodile species, animals alive today that are closely related to extinct dinosaurs.  The birds (Aves) are the fastest growing terrestrial vertebrates, anyone who has observed nesting garden birds can see how, within a few weeks, the hatchlings are almost the same size as their parents.

Birds develop unlike all other living archosaurs.  As part of this postnatal development, birds possess a low amount of intraspecific variation, put simply, one bird such as a blackbird (Turdus merula) grows at much the same rate as other members of its species and there is little size variation in populations.  The Coelophysis flock shows a very different growth rate with a wide variety of adult sizes.  When did this low variation in body size amongst archosaurs evolve?  By studying the extensive fossil collection of one species of non-avian, extinct animal (Coelophysis), scientists hope to pinpoint this transition in Mesozoic theropods.

Coelophysis Study Sheds Light on the Evolution of Growth Rates Amongst the Theropoda

A scale drawing of the Triassic dinosaur Coelophysis.

Picture credit: Everything Dinosaur

To view models of Coelophysis and other prehistoric animals: Wild Safari Prehistoric World Models and Figures.

Analysing the Fossil Bones of Coelophysis

Geosciences Master’s student Christopher Griffin went onto state:

“As these animals grew, muscle attachment scars formed on the limb bones, and the bones of the ankle, hips, and shoulder fused together, similar to how the skull bones of a human baby fuse together during growth.  Fossils of even a single partial skeleton of an early dinosaur are exceptionally rare, so to have an entire group of a single species that lived and died together provided an unparalleled opportunity to study early dinosaur growth like never before.”

Variation Lost in More Derived Theropods

The team concluded that this high variation in early dinosaurs as demonstrated by the Coelophysidae was lost in more derived theropod dinosaurs such as Allosaurus of the Late Jurassic and Late Cretaceous tyrannosaurids.  This intraspecific high variance could have contributed to the rise of the Dinosauria during the Triassic-Jurassic extinction event.

Assistant professor Sterling Nesbitt added:

“Large variation in early dinosaurs may have allowed them to survive harsh environmental challenges like dry climate and high levels of carbon dioxide.  Understanding why dinosaurs were so successful has been a great mystery, and high variation may be one of the characteristics of dinosaurs that led to their success. However, it’s difficult to determine whether this trait evolved in response to the environment or was simply a stroke of luck that allowed these dinosaurs to survive and thrive and become the most dominate vertebrates on Earth for 150 million years.”

Not Down to Differences in Size Between Males and Females

Variation in those species of early dinosaurs which have a more substantial fossil record had been put down to sexual dimorphism in the past.  However, this new study, which focused on growth rate analysis as conferred by the degree of bone fusion and muscle scar evidence on the fossilised bones, did not find data to support that the fossil assemblage growth rates were solely down to differences in the adult size of males and females.

Steve Brusatte, a palaeontologist from the University of Edinburgh, who has undertaken research into the growth rates of other types of theropods, such as tyrannosaurs, commented:

“Studies like this are a perfect demonstration of how fossils can help us understand the evolution of peculiar features and behaviours of modern animals.  How dinosaurs grew may have been both the key to their early success and the reason that one particular unique subgroup, the birds, survives today.”

The scientific paper: “Anomalously High Variation in Postnatal Development is Ancestral for Dinosaurs but Lost in Birds”.

Visit Everything Dinosaur’s award-winning website: Everything Dinosaur.