Coping with the Heat – How Some Dinosaurs Did It

Coping with Heat – How Some Dinosaurs Stayed Cool

As temperatures soar in the United Kingdom and the southern part of the country endures temperatures in excess of 30 degrees Celsius, lots of media space is dedicated to the subject of how to keep cool in what looks like to be the hottest days of our all to brief British Summer.  Although, the weather has certainly been hot in places like central London, when the temperatures recorded at midday in Britain are compared with other places in the world where we have been, (Kenya, Canada, USA), for example, the hot UK weather is put more into context.

For some dinosaurs, keeping cool may have presented them with some serious difficulties to overcome.  Whilst horses in a field will often seek out the shade and shelter of a tree during the hottest part of the day, a Brachiosaurus for example, may not be fortunate enough to find a tree canopy big enough, or indeed tall enough to stand under.  A typical Brachiosaurid, such as Sauroposeidon, Brachiosaurus or Camarasaurus would have held their heads many metres above the ground.  In the case of Sauroposeidon, from the fossil evidence gathered to date, it has been estimated that this creature could have raised its head to over 20 metres above the ground.  Wandering around in the mid-day early Cretaceous sun, it is surprising that the brains of these animals did not cook inside the skulls.  These dinosaurs and indeed many other families of dinosaurs must have had ways in which they could modify and maintain a constant body temperature.

An Illustration of a Typical Brachiosaur

Picture Credit: Everything Dinosaur

Having a stable, almost constant body temperature is important in vertebrates, whether they are endothermic or ectothermic (warm-blooded or cold-blooded).  A stable internal body temperature will allow the animal’s chemical processes to work efficiently and constantly.  Chemical reactions in the body are controlled by enzymes and these are very temperature sensitive.  Birds and mammals maintain stable internal temperatures and it is believed that dinosaurs did too.  The trouble for a huge herbivore like a Brachiosaurid is that it would have generated a lot of heat irrespective of the weather.  For starters, these animals had huge guts, basically a series of fermentation chambers.  The fermentation of digested and digesting remains of plants would have produced a lot of heat.  Secondly, just moving around, an animal as big as a Brachiosaur would have generated a lot of heat in its huge leg muscles and this would have to be dissipated somehow.

With such a large surface area to volume, a Brachiosaur may have struggled to cool down, but just like many large animals that live in hot climates today, these dinosaurs had survival strategies for coping with heat.  Some of these strategies would involve anatomical changes in their bodies to help regulate body heat, other strategies would be related to the way these animals behaved.

African elephants for example, have evolved large ears, these act as radiators, permitting blood to be circulated close to the surface of the skin and subsequently cooled.  Some scientists have speculated that the long, cylindrical neck and tail of a Brachiosaurid would have made effective radiating surfaces, particularly if blood could be selectively channelled under the skin, as it can be in some extant reptiles.  This could be an example of an anatomical adaptation with regards to thermal regulation.

Brachiosaurs may have sought relief from the harshest part of the dry season by migrating to cooler, higher regions perhaps.  They may have wadded in lakes in order to cool down, an adult Brachiosaurus would certainly have nothing to fear from the crocodiles and other lake predators.

To keep the head cool, after all, it was perched high up in the full glare of the sun, Brachiosaurids may have had another trick up their sleeve, or to be more precise up their noses.  Brachiosaurids are classified as Macronaria (big noses), they have a distinctive, box-like head shape with the holes in the skull representing the nostrils far bigger than the holes in the head for the eyes (orbits).  Could a Brachiosaur keep a cool head by allowing blood to circulate in special channels close to the skin in these large, moist nostrils?

These big, moist, nasal cavities would have cooled the air that the animal breathed in and if blood was channelled into special tissues close to the internal surface of the nostril, this may have proved to be an effective cooling device.  The process would be similar to the ears of an elephant, which can act as a radiator to cool the blood.  By flapping its ears an elephant creates airflow which can accelerate this process.  Perhaps a Brachiosaur could have cooled its small brain simply by breathing in and out in a regimented manner, permitting a greater airflow over the moist membranes and thus increasing the speed of the cooling.  A head at 20 metres off the ground is generally moving through cooler air than the body, this difference in temperature between the head and the top of the neck compared to the bulky body, may also have had a role to play in helping to regulate temperature.

When a hot period of weather breaks, there is often a thunderstorm.  If you are 20 metres tall you could have been the highest thing around on the late Jurassic or early Cretaceous plains.  This could be dangerous especially if there was any forked lightning around.  Perhaps big Brachiosaurids were occasionally struck by lightning.

To read about a newly discovered genus of early Sauropod that may have had a trouble keeping warm, as it lived in Antarctica (Glacialisaurus): A long-necked dinosaur from the Antarctic

The BBC – Bring Back the Cretaceous

Trip to the BBC (Bring Back the Cretaceous)

This week is forecast to be one of the hottest on record in the United Kingdom, not the sort of weather for getting onto a crowded train and heading off into the big city, but for one of Everything Dinosaur’s team members, this was their first job on Monday morning.

A spokesman for Everything Dinosaur had been asked by BBC Radio Scotland to discuss the upcoming Walking with Dinosaurs tour that kicks off its British dates in Glasgow.  Fortunately, this did not mean a trip up north, but instead a team member was invited to the BBC Manchester studios to take part in the broadcast.

It can be an odd feeling sitting in a little broadcasting booth with headphones on listening to and taking part in a conversation with people who are in effect several hundred miles away, but this is all in a day’s work for us.

Armed with our notes and with some assistance from the lovely BBC staff (special mention for Ann, who kept us supplied with water), the whole interview was conducted in about 15 minutes.  The programme was going out live on BBC Radio Scotland – MacAulay and Co, a consumer affairs programme.  The feature concerned a debate between yours truly and a Scottish comedienne who could not understand why dinosaurs are still so popular.

Broadcasting at the BBC

Picture Credit: Everything Dinosaur

Looking a little hot but bearing up on the pressure of having to defend the popularity of dinosaurs – Everything Dinosaur broadcasting at the BBC.

As we were waiting for the radio programme to start, we played a game making up new meanings for the acronym BBC – the best we could come up with was “Bring Back the Cretaceous” – must have been nervous preparing for the radio interview.

Montana Palaeontologist Sentenced to 3 Years Probation for Stealing Fossils

Well-known American Palaeontologist Sentenced after Court Case

Nathan Murphy, a self-taught palaeontologist from Montana was sentenced on Wednesday to three years probation, having been found guilty of stealing fossils from Government land.  He was convicted of stealing 13 dinosaur bones from the Hell Creek Formation in 2006, earlier this year he was sentenced to 60 days imprisonment for the theft of a Dromaeosaur fossil.  He had claimed that this specimen was his own find and Mr Murphy had wanted to sell copies and casts of this particular fossil to museums.  The judge also ordered him to pay over $17,000 in restitution.

He had already pleaded guilty to charges and we covered this case in previous blog articles, an insight into the shady and murky world of black market fossil sales.

To read the earlier articles:

First article: Local Fossil Collector Charged with Theft

Second article on the Nathan Murphy charges: Guilty Plea in Montana Dinosaur Theft Case

The case has severely damaged the reputation of the 51-year old, who has been responsible for finding a number of important specimens in the Montana strata.

Notwithstanding the fact that Mr Murphy sought financial gain my having casts made from at least one stolen fossil, Murphy says the fossils themselves were never at risk and were later turned over to a not-for-profit foundation.

Mr Murphy’s lawyer, Michael Moses commented:

“This case is a lesson well learned, Mr Murphy’s reputation and status within the palaeontological community has been severely affected”.

Nathan Murphy runs a company charging tourists to take part in dinosaur excavations, he was also a director of a dinosaur research facility in the state, before resigning in July 2007, the resignation coinciding with the investigation by the federal authorities.

Recently, the laws in the USA regarding the theft of fossils from public land were tightened when President Obama signed a new law creating a maximum prison term of up to five years for stealing fossils or other artifacts.

Palaeontologists and some public land managers, including the Bureau of Land Management (BLM) had sought a stronger measure for years, but it came too late for Mr Murphy’s case.   However, the sentencing of Mr Murphy indicates the strong action the authorities are taking to help deter the stealing of fossils .

Dinosaurs and the Guinness Book of Records 2009 – Mistake

Dinosaurs and the Guinness Book of Records – A Bad Mistake

With the recently published paper from researchers at Colorado State University, identifying potential flaws in the calculations used to estimate the weight of dinosaurs, one of our team members decided to check in the Guinness Book of Records to see how this new data might affect dinosaur records.  The 2009 edition of the Guinness Book of Records was duly checked to see how this new data may change the information presented.  We have purchased the Guinness Book of Records for many years and find it an informative and helpful resource (great for settling non-dinosaur related disputes amongst team members).

If the new calculations from the American researchers are proved to be more accurate, than previous data, then the weights of many dinosaurs such as Brachiosaurus and Diplodocus may have been overestimated.  Slimmed down dinosaurs would have several implications for the compilers of the Guinness Book of Records, many statistics published about the biggest and heaviest of these creatures would have to be re-examined.

To read more about the Colorado State University research Dinosaurs were “Thinosaurs”

Surprisingly, in the 2009 edition we noticed a mistake on the pages dedicated to the fossil record (pp 79-82).  The word Theropod was spelt wrongly.  The dinosaur section features a 3-D poster pull out, packed with lots of data on dinosaurs and other extinct animals, however, in at least two places the word Theropod was spelt incorrectly.

The Theropods (means “beast foot”)  were a suborder of the Saurischia, the lizard-hipped dinosaurs.  They were bipedal and predominately meat-eaters, although a number of Theropod families evolved herbivorous habits.  The formal classification is Theropoda but in palaeontology, the formal terms in taxonomy are other interchanged with less formal ones.  However, in the 2009 edition of the Guinness Book of Records the word is spelt “Therapod”, with an “a” not an “o”.  We have not come across this particular word usage before and have checked with American colleagues to see if this is an Americanism.  No it is not, we were informed.

Perhaps this mistake has been overlooked in the proof reading process.  If time permits we will write to the Guinness Book people to see if we can find out why the word Theropod has been spelt in this manner, there may be a perfectly valid reason.  It could be a proofing error, they do happen from time to time, in even the most carefully researched reference books.

It makes us wonder what other mistakes and inaccuracies may lurk inside this publication.  Our confidence is shaken, looks like it is not as reliable as we thought, so we may not be able to defer to its pages when settling arguments in the office over some of the more unusual and bizarre things we get to discuss.

Fossil Turtle – A new Jurassic Species discovered in Thailand

Ancestor of Asian Turtles – Basilochelyes macrobios

Scientists have announced the discovery of the fossil of a previously unknown turtle species dating from the Jurassic period near Phupan mountain in the eastern Thailand province of Mukdahan.  Analysis of the shape of the carapace (shell) and the backbone of this animal indicate that this species was the ancestor of several extant species of turtle found in south-east Asia today.

Thailand is proving itself to be an important country for palaeontologists and geologists studying life in the early Mesozoic.  The fossils of one of the first species of Chelonians, Proganochelys; have been found close to the city of Khon Kaen in the northeast of the country.  Proganochelys was approximately one metre long and had a box-like carapace.  Unlike modern species, it could not retract its neck fully into its shell.  Instead the neck was protected by rows of spikes, important to protect this vulnerable part of its body from attacks as there were a number of early Theropod dinosaurs (Coelurosaurs) around during this particular time in Earth’s history.

Proganochelys (P. quenstedii) lived close to freshwater lakes and rivers.  It probably was semi-aquatic.  Unlike extant species, this primitive tortoise had small teeth in the roof of its mouth.  Modern species of tortoise/turtle have not teeth in their jaws.  Proganochelys shared its watery environment with a number of bizarre creatures, the heavy Rhynchosaurs with their powerful beaks, the unusual Gerrothorax and the huge, carnivorous amphibian Mastodonsaurus.

This new species of extinct turtle dates from the late Jurassic (approximately 150 million years ago), this part of Thailand was a lush, lowland area with many lakes and rivers crossing it.  In fact the environment was quite similar to the environment in which Proganochelys flourished sixty million years earlier.

The turtle discovery confirms the geological importance of the north-eastern region of Thailand, where many other fossils of Mesozoic animals have been found.  Two pieces of turtle fossil measuring 80cm by 90cm were discovered by geologists in 2005 in Mukdahan province.  A number of important fossils have been discovered in the area, ancient fish, primitive crocodiles and dinosaurs.

The Remains of a new Species of Turtle found in Thailand

Picture Credit: Bangkok News

Dinosaurs discovered in Thailand include Titanosaurs and large meat-eating dinosaurs, members of the Allosauroidae.

To read an article about the discovery of the largest meat-eating dinosaur known to date from Thailand: Allosaurus Fossils Discovered in Thailand

Chinese experts worked with the geologists and the paper on this new species was published earlier this year in the London-based scientific paper, the Journal of the Geological Society.  This new species has been named Basilochelyes macrobios.

Turtles and tortoises possess a shell, their most distinctive feature.  The shell is actually a modified ribcage covered in armour plates.  Unlike other vertebrates (animals with backbones), Chelonians have a modified skeleton so that their shoulder and hip girdles are inside the ribcage.  An armoured shell is not unique in the fossil record, some Placodonts, part of the Sauropterygia reptile group also developed a turtle-like shell.  Animals such as the Triassic Henodus, for example, a one metre long reptile; lived in lagoons and shallow seas.  It also lacked teeth, like modern tortoises and may have filtered its food living on phytoplankton and other small organisms.

Science Weeks – A Big Success for Schools

Science Week in Schools

Teachers at Everything Dinosaur are frequently asked to attend schools and participate in school projects, events or programmes promoting science.  Such activities can involve students in all sorts of exciting and curriculum enriching lessons and palaeontology does lend itself to become the basis for a science or maths orientated lesson plan.  After all, if the children are genuinely interested and excited about something they are doing they are likely to learn more and remember.  Everything Dinosaur team members recently took part in Lorton Primary School’s science week, we met lots of enthusiastic students and as usual we were bombarded with questions as we cast dinosaur teeth, showed fossils and demonstrated how much you can learn by looking at dinosaur foot prints.  We even took a peep inside a dinosaur’s stomach!  All part of our teaching about fossils in schools.

Nervous Moments with an Experiment

Picture Credit: Everything Dinosaur

The picture above shows a pupil at Lorton Primary School, carefully preparing a cast of a real Tyrannosaurus rex tooth, that was found in Alberta, Canada.  A steady nerve is required, but with luck the class will have their very own T. rex tooth to study in a few minutes time.

Fossils are Really Cool!

Picture Credit: Everything Dinosaur

One of the really great things about fossil hunting is that in most case, when looking in the United Kingdom, you can keep what you find.  One pupil is rather taken by this beautiful Ammonite fossil found by an Everything Dinosaur team member at Charmouth, Dorset.  We use the Ammonite fossils to explain a little about the fossilisation process and to demonstrate that not all fossils are dinosaurs.

Rather Taken with T. rex Toes

Rather taken with T. rex Toes

Picture Credit: Everything Dinosaur

With all the museum quality fossils and casts that we have in our collection, young palaeontologists get the chance to handle and get close to some amazing objects such as this cast of an adult Tyrannosaurus rex left metatarsals (II,III and IV), part of our section of the teaching programme where we try to compare the bones of a big dinosaur to those of own bodies.  With our qualified teachers we certainly get invited to a lot of schools and who knows, we might just inspire a young person to take up a career in science.

We always appreciate the hard work of the teachers, teaching assistants and the PTA for organising such activities, as part of our commitment to the Institute for Learning and other bodies we are members of, we get feedback on our work.  We get some lovely comments and team members are always thinking up new ways to inform and to educate.

Dinosaur Workshops and Dinosaur Teaching: Dinosaur Teaching and Dinosaur Workshops for School

Proof Reading and yet more Proof Reading

The Joys of Proof Reading

Today a little proof reading of some signage and information panels for an exhibition we are working on was required.  We had to proof a series of A2 sized information panels that are being printed to provide details of some prehistoric animals that are making up part of exhibition, Everything Dinosaur is going to be involved with over the Summer.

Team members are often asked to help out with such tasks, either devising the information for the panels or checking what the design team have come up with.  We try to turn things around as quickly as we can in order to minimise any hold ups.  Everything went well until we came to proof the panel associated with Ornithomimus.  Rather than describe a genus such as Ankylosaurus, and Triceratops as with the other information panels, for some reason the panel on Ornithomimus referred to Ornithomimosaur, which in taxonomic terms relates to the Superfamily level rather than to a single genus (Ornithomimosaurs).  The Superfamily is also referred to as Ornithomimosauria or indeed Ornithomimids.  The name actual means “bird mimics”, as these animals are similar anatomically to large flightless birds such as emus and ostriches.

Ornithomimus was a member of a family of dinosaurs that are sometimes called “ostrich-like dinosaurs”, as they resembled flightless, long-legged birds such as ostriches and emus.  This dinosaur may have reached lengths in excess of 4.5 metres (15 feet) long.

We added a range of facts to each of the data panels, hopefully when the exhibition opens the panels will provide visitors with extra information.  Panels were checked on Ankylosaurus, Oviraptor, Triceratops and of course Tyrannosaurus rex.

Taking a Bite out of a Record – Largest Theropod Tooth to Date found in Spain

Allosaurs on the Hunt in Spain

Scientists from the Teruel-Dinopolis Joint Palaeontology Foundation in Spain have been busy examining a single broken tooth from a large meat-eating dinosaur found in the Riodeva area, approximately 100 miles west of Madrid.  The shape and size of this tooth (9.83cm long), have left the researchers in no doubt that this is evidence of a large Allosaur roaming around this part of Spain approximately 155 million years ago.  The tooth is the largest yet found in the country and indicates that whatever type of animal lost this tooth, it probably was the apex predator in the region.

Commenting on the classification, Luis Alcalá, one of the researchers involved with the study stated:

“Given the great variations between the teeth of different kinds of Allosauroids, it would be prudent for us to assign this fossil to an indeterminate Allosauroidea”.

Allosaurs are classified as part of the Theropod tetanuran group (stiff tails).  They were large, bipedal predatory dinosaurs with deep skulls and were notable for having prominent brow bumps or ridges along the tops of their skulls.   Known from the Jurassic of northern hemisphere, this group became rare into the Cretaceous but survived in the south and became some of the largest meat-eating dinosaurs known to science with animals such as the Carcharodontids dominating the food chains of Africa and South America.

The paper on this single tooth is due to be published in the upcoming issue of Estudios Geológicos.

The single, curved and sharply pointed tooth was found by locals in Riodeva, Teruel and is from the Villar del Arzobispo Formation.  Comparisons with other Allosauroidea fossils from the Iberian Peninsula have shown that this is the largest tooth of a meat-eating dinosaur found in the country to date.  A tooth measuring 12.7cm was discovered in Portugal a few years ago, this too is believed to represent a member of the Allosauroidea.

Fancy a  Bite? The Allosaur Tooth from Riodeva

Credit: FCPT-Dinópolis y Escuela Taller de Restauración Paleontológica

The scientists hope to be able to build up an accurate picture of the ecosystem in this part of Jurassic Europe, one of the few parts of what we now know as continental Europe that was not covered with warm, shallow, tropical sea.  To date, fossils of Stegosaurids, Ornithopods and Sauropods have been found in the region, now they have evidence of a top predator, although the remains of smaller Theropods had been discovered previously.

Meat-eating dinosaurs shed teeth throughout their lives, hence one of the reasons for their nick-name “land sharks”.  This particular tooth and the condition of its crown (without any re-absorption surfaces), may indicate that this tooth was shed from the jaws of a decaying corpse.  If this is the case then further remains of the dinosaur may be uncovered and the palaeontologists may be able to get a lot closer to this giant carnivore than previously thought.

An Illustration of a Typical Allosaur

Picture Credit: Everything Dinosaur

Over the years, Allosaurus has proved to be one of the most popular of all the meat-eating dinosaurs to make models of.  The best specimens are known from the Late Jurassic strata of the USA, for example the Morrison Formation.

To view a model of a typical Allosaurus: Dinosaur Toys for Boys and Girls – Dinosaur Models

Dinosaurs were Thinosaurs – A Weighty Issue?

Dinosaurs on a Diet – Statistical Evidence over Body Mass Queried

It may be time to re-write the entry for dinosaurs in the Guinness Book of World Records as evidence from an American based research team have uncovered a series of potential flaws in the calculations used to estimate dinosaur mass and body weight.  Just when we were getting used to bigger and bigger estimates for the size of some of the larger genera such as the Titanosaurs, it seems that the calculations as to how heavy some of these creatures may have been, need to be scaled down.

The team from Colorado State University have analysed the current statistical model used to estimate the weight of extinct animals and they have found that potentially a large Sauropod such as Apatosaurus, once thought to weigh over 30,000 kilogrammes may actually weighed under 20,000 kilogrammes.  Some scientists state that Tyrannosaurus rex, the large, well-known carnivorous dinosaur of the Late Cretaceous, weighed over 7 tonnes.  According to this new model, it would have weighed about 1 tonne less.

Commenting on the research, Gary Packard of Colorado State University said:

“Palaeontologists have for 25 years used a statistical model to estimate the body weight of giant dinosaurs and other extraordinarily large extinct animals, we have found that the statistical model is seriously flawed and the giant dinosaurs probably were only about half as heavy as is generally believed”.

If dinosaurs were far lighter than previously thought, this would have very significant implications for their lifestyle, habits and behaviours.  They would be leaner and perhaps more agile and faster.  They would have needed less food to sustain them and so some of the interpretations regarding large dinosaurs may have to be revisited.

Not so Huge Perhaps?  An Illustration of an Apatosaurus

Picture Credit: Everything Dinosaur

The differences in the calculations are dependent on what type of analysis is undertaken.  The dimensions of bones such as the humerus and the femur are relatively easy to calculate, there are many fossilised bones for the scientists to use. The problem lies in the mass ascribed to the skeleton, since soft tissue is rarely preserved scientists have little to go on when it comes to accurately estimating body-weight, particularly in creatures which are so very different and much larger than extant species.

Gary Packard and his fellow researchers worked from the same information regarding dinosaur bone measurements as previous scientists, but rather than using back-transformation from logarithmic formulae, they chose to use equations fitted by non-linear regression.  The team’s results vary from the accepted statistics given for many dinosaurs and the heavier the animal studied, the greater the variation between the Colorado team’s estimated weight and the weight given in many textbooks.  However, to verify their measurements the Colorado based scientists used their amended formula to work out the weight of a modern African elephant.  Their findings estimated a weight of 5,900 kilogrammes, about what you would expect for a large adult elephant.

This work is not that unique, there have been many theories put forward regarding the actual mass of extinct animals, particularly the larger dinosaurs.  Another paper published last year in the scientific journal Fossil Record used a different technique for estimating body mass, but calculated similar results to those of the Colorado team. That study was led by Hanns-Christian Gunga of the Charité-Universitätsmedizin Berlin.

The superbly well-preserved Hadrosaurine (nick-named Dakota), an Edmontosaurus, has preservation of flesh around some of the bones, we at Everything Dinosaur have seen cross-sections through the ulna and radius (arm bones), measurements as to the depth of flesh around the bones in specimens such as this duck-billed dinosaur may help scientists clarify the estimated weight of other types of dinosaurs.  Interestingly, the vertebrae seem to be further apart in this specimen than previously thought.  This may mean that scientists are going to have to amend their estimated sizes for this type of Hadrosaur.  They may actually have been bigger than we think!  Animals such as Edmontosaurus have been estimated at lengths in excess of 13 metres, now this new find may lead to scientists having to revise these estimates.  They may have been larger than previously thought, but their actual body mass remains controversial.

John Hutchinson, a researcher in evolutionary biomechanics at the Royal Veterinary College (London), has also tried to estimate the weight of dinosaurs such as Tyrannosaurus rex, as part of his studies into Dinosauria locomotion.

Commenting on problems associated with guessing the weight of a dinosaur he stated:

“The best we can do is put the weight [T. rex] at six to eight tons for a typical adult.  There is a big question about how much skin they had and how much flesh”.

Perhaps it is time for a re-think on the body mass of the largest dinosaurs.  Everything Dinosaur team members are already working on a new, sleeker model of a Brachiosaurid – Giraffatitan.

Bizarre Jurassic Ceratosaur Points Finger at Dinosaur Avian Link

Chinese Jurassic Ceratosaur Provides Evidence of Ancestral Link between Theropods and Birds

The link between certain types of dinosaur and birds is largely accepted by many scientists today, the first rumblings about a connection can be traced back to the 1880′s the time of  Harry Govier Seeley, largely responsible for the taxonomic classification of Dinosauria.  Indeed, the likes of the Thomas Henry Huxley in the early 1860′s had remarked how similar anatomically dinosaurs were to birds; fuelled no doubt by the discovery of an almost complete skeleton of Archaeopteryx in 1861.  However, the paucity of the fossil record and the lack of key, transitional fossils showing animals evolving from one type of creature to another, the stages of evolution as it were, does mean that debate still continues as to the precise relationship between Dinosauria and Aves.

A recent study by scientists at the Oregon State University, analysing the process of bird’s breathing and their lung structure led this particular team of researchers to conclude that birds are not the direct descendants of Theropod dinosaurs.  Evidence gathered from their particular study indicated a shared, common ancestor but no direct descent.

To read more about the Oregon State University research: Controversy over the Dinosaurs/Birds Link

This is one of the fascinating aspects of palaeontology, as new fossils are found, or as new techniques are developed to study known fossils, theories and concepts regarding Dinosauria change and evolve.

When trying to demonstrate some of the anatomical links between birds and dinosaurs a roast chicken or turkey can be dissected and some of the similarities shown.  This is not recommended at Christmas, as it can interrupt the festivities and upset the cook.  However, a couple of years ago, we did publish an article pointing out some of the things to look for when you carve the Christmas dinner.

To read this article: Christmas Dinner Links Dinosaurs to Birds

One of the problems associated with the link between dinosaurs and birds was trying to explain the differences in the finger pattern seen in Theropod dinosaurs and in birds.  Put simply, the Theropod ancestors of birds and birds share a characteristic of having three fingers (digits), problem is; Theropods have digits I, II and III, whilst birds have digits II, III and IV.  Now the discovery of a new, bizarre Theropod with four fingers on each hand may provide evidence that explains this anomaly and help to unravel the mystery of how birds are descended from dinosaurs.

An international team of palaeontologists led by scientists from the Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP) in Beijing, have uncovered the articulated remains of a bizarre, beaked, herbivorous Theropod that may shed some light on the bird/dinosaur digit mystery.  In total two skeletons were found, including evidence of gastroliths (stomach stones) it is these stones that provide evidence of a tough, fibrous diet for this little, biped.

The remains were found in Jurassic strata (Oxfordian faunal stage), dating this dinosaur to the mid to late Jurassic approximately 156 million years ago.  The dinosaur has been named Limusaurus (means mud lizard), the binomial name is Limusaurus inextricabilis.

The Fossils of Limusaurus (L. inextricabilis)

Picture Credit: James Clark

The head of Limusaurus is towards the right of the picture, the beautiful and very well preserved caudal vertebrae (tail bones) of this dinosaur can be seen in the bottom left.  In the centre of the picture between the claws of the hind legs a pile of gastroliths are shown, in what would have been the stomach cavity. This section of the fossil is enlarged and the individual stones can be made out (top left corner).

A total of two skeletons of this dinosaur have been found, identified as a member of the Theropoda, but a plant-eater, Limusaurus exhibits characteristics that may identify it as a transitional fossil, providing evidence on how dinosaur digits evolved and changed over time.  The remains are of juveniles (analysis of bone fusion), these animals were 1.7 metres long, and lightly built, but it is not known how big a fully grown adult would have been.  The long hind limbs indicate that this dinosaur was a fast runner and as many other Theropods from China have been discovered with primitive feathers, Limusaurus is illustrated as a feathered dinosaur.  This dinosaur could not fly, but an active, cursorial lifestyle may indicate that this dinosaur was warm-blooded and the feathers would have helped insulate the animal and retain body heat.

An Artist’s Illustration of Limusaurus

Limusaurus drawing

Picture Credit: Portia Sloan

Limusaurus is certainly an unusual Theropod.  Classified as a primitive Asian Ceratosaur, this long-limbed, short-armed, toothless but beaked dinosaur may prove to be a transitional fossil helping to explain the evolution of Theropoda digits to the II, III, IV digit formation of birds.  The remains were found in the Junggar Basin in the Xinjiang Uygur region of northwest China.

Xu Xing, one of the principal investigators and an illustrious member of the scientists at the IVPP describes this dinosaur as having four digits (fingers) on each of its small hands.  Digits I, II, III and IV equivalent to the thumb, index finger, middle and the ring fingers in humans.  However, digit I (thumb) is greatly reduced and the second finger (digit II – index) is very much larger, perhaps compensating for the vestigial state of the first digit.

Palaeontologists who supported the dinosaur-bird theory long faced a problem on fingers. Previous fossils of Theropod dinosaurs showed earlier dinosaurs had five fingers and later ones gradually lost their ring finger and little finger, what is know as lateral shedding, the outside fingers went.  Birds show skeletal traces of former fingers, the index, middle and ring fingers, in other words digits II, III and IV.  The different digit formations is one of the major stumbling blocks when it comes to accepting the theory that birds are indeed descended from Theropod dinosaurs and in essence highly evolved, avian dinosaurs.  Limusaurus may provide evidence as to how the changes in fingers came about, Xu Xing commenting on the fingers of Limusaurus stated:

“The new Limusaurus indicated a different pattern of finger reduction.  It was the thumb that was lost, instead of the ring finger”.

Co-author of the research paper on this new dinosaur, James Clark, of the George Washington University (United States) stated:

“This new animal is fascinating by itself, and when placed into an evolutionary context it offers intriguing evidence about how the hand of dinosaurs evolved into the hand of birds”.

The Right Hand (right manus of Limusaurus)

The hand of a dinosaur.

Picture Credit: James Clark (annotation by Everything Dinosaur)

The international team re-examined hand skeletons of some previous fossils of Theropods.

“We realised the pattern of their finger reduction was much more complicated than people had thought,” Xu added.

The scientists believe that the first digit becoming smaller and the importance of the second digit becoming greater indicate the beginnings of a trend in the evolution of dinosaur digits that would eventually lead to the configuration of II, III, IV as seen in birds.  Limusaurus marks the beginning of a trend in finger development.

They also presented a new hypothesis to explain why advanced Theropods, from which birds were believed to have evolved, had the second, third and fourth fingers but they looked like the first three ones, as some fossils showed.  Previously, palaeontologists believed that Theropod dinosaurs as they evolved and changed over time, gradually lost fingers, but from the outside of the hand inwards (the lateral side).

Theropod dinosaurs have traditionally been assumed to have lost fingers from the lateral side inwards.  This differs from the bilateral reduction seen in other Tetrapod groups, i.e. losing digits from both the medial and lateral sides (inside and outside digits of the hand).  This strange reduction pattern is clearly present in primitive, basal Theropods and has also been inferred in other types of Theropod, based on the identification of their three-fingered hands (digits I, II and III present).  However, this contrasts with the evidence from the extant Theropods, the birds which have digits II, III and IV present.

The evidence from the skeletal remains of Limusaurus indicate that the index finger may well be taking on the appearance and prominence of the thumb, a case of digit II evolving into digit I.

Xu Xing went on to state: “Homeotic changes might happen on dinosaurs, which means that the index finger has the features of a thumb.  Such changes happened in humans, for example, a person usually has seven cervical vertebraes [neck bones] but, for some people, the first thoracic vertebrae has the feature of the cervical ones”.

Commenting on these findings, Alan Feduccia, (Palaeobiologist at the University of North Carolina) stated:

“If confirmed, this would be the only early dinosaur with a hand composed of the middle three digits, which is the same pattern as that of modern birds, albeit dramatically different in overall hand morphology, as well as having a highly abbreviated forelimb”.

He went on to add:
“The new fossil answers many questions and raises still another set of unknowns”.

Guenter Wagner, a renowned Yale evolutionary biologist, responded to the paper (published in the scientific journal Nature):

“There is very strong developmental evidence that there was a homeotic change in digit identity in the evolution of the bird lineage.  I find it intriguing that there is more similarity to the 2,3,4 digits proximal, and more similarity to 1, 2, 3 digit identities distally”.

Wagner, however, remained neutral on the question of whether the morphology of this animal is a derived feature that may not be informative of the stages the bird lineage went through.  This new research does provide some very interesting and intriguing questions, whether or not Limusaurus is a true transitional fossil has yet to be determined, but it does provide an interesting insight into one potential path from cursorial three-fingered dinosaurs to the birds that can be seen today.

Reference: Xing Xu et al, “A Jurassic ceratosaur from China helps clarify avian digital homologies,” Nature 459:940 doi:10.1038/nature08124

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