Paleo Profiles: Dilophosaurus

The reconstructed holotype at the Royal Ontario Museum

One of the most iconic dinosaurs from Jurassic Park is the crested Dilophosaurus which blinded and ate the hapless Dennis Nedry in one of the most iconic scenes of the movie. The Jurassic Park version of the Dilophosaurus has gone on to inspire recreations of the dinosaur in popular media, ranging from toys to video games. However, the real Dilophosaurus was fairly different from its Hollywood counterpart.

Discovery and Fossils

The Dilophosaurus was first discovered in 1942 by American palaeontologist Charles Camp, who was on an expedition to find vertebrate fossils in northern Arizona. In the Kayenta Formation, guided by local Navajo, the expedition found three dinosaur skeletons. While two were very eroded, the first one they found was almost complete. As always with fossils, there was a large gap in time between initial discovery and description, and the dinosaur was not named until 1954 by palaeontologist Samuel P. Welles. However, he believed that the new dinosaur was a species of an already discovered dinosaur called Megalosaurus, which was actually the first discovered/named dinosaur. Welles named the fossil Megalosaurus wetherelli after a Navajo councillor whose nephew had help discover the fossil, and who had helped the expedition himself. Megalosaurus has been seen as a 'wastebasket taxon' - a taxon where organisms don't seem to fit anywhere else are put in there. In 1964 Welles returned to the Kayenta Formation to find more fossils, and he found another near complete skeleton where the three earlier ones had found. What he found made him realise that Megalosaurus wetherelli was not as they initially thought. The skull of the new discovery had crests, and the dinosaur was overall larger than the earlier finds. Upon re-examining the holotype Welles realised that the crests had become dislodged from the skull, so he had the dinosaur renamed to Dilophosaurus wetherelli - 'Two-crested Lizard'. New fossils were found and in 1987 a near complete skeleton was discovered in Lufeng Province, China, and a few years later named Dilophosaurus sinensis. It was later discovered to not be actually a Dilophosaurus, but instead another species of a different dinosaur called Sinosaurus in 2017.

Biology

The real life Dilophosaurus differed greatly from its appearance in Jurassic Park

Dilophosaurus was a theropod dinosaur - this was a suborder of dinosaurs characterised by bipedal stances. This order includes many different species ranging from modern birds to the Tyrannosaurus. Existing at the very start of the Jurassic Period Dilophosaurus this means that it was one of the earliest theropods, and definitely one of the earliest large carnivores. When it was alive it would have been one of the largest carnivorous dinosaurs on the planet; from snout to tail it could reach 6 metres long, and could reach heights of up to 2 metres. Very different from the diminutive version in the movies. The initial three skeletons found were determined to be juveniles as the fossil found by Welles was much larger than the first three. An adult would therefore be the size of a brown bear. Just like a bear Dilophosaurus had very powerful arms - this will become important later. They were likely quite hardy animals. Phil Senter and Sara Juengst in 2016 found that one specimen had eight fairly bad injuries. However, most of the injuries showed signs of healing indicating that it could have lived years after getting initially wounded. A reason why it might have survived so long is possible evidence of pack behaviour. As specimens of similar ages have been found together it has led to the suggestion that they worked and lived together to survive - it would explain how the injured one lived. However, we cannot be entirely certain - a flash flood could explain why they were found together, especially considering how well preserved some specimens are. We now know that most dinosaurs would be feathered by the end of the Jurassic, but palaeontologists have been debating about when feathers developed. We have yet to find evidence of feathers on Dilophosaurus itself, but in 2004 Martin Kundrat reported finding traces of filaments from downy feathers on a theropod dinosaur from early Jurassic Massachusetts. If this dinosaur had some form of feathers it is not out of the question that Dilophosaurus also did so. Senter and Juengst even found that their specimen had a deformed humerus and finger thanks to developmental osteodysplasia - a condition previously only found in modern birds. If a Dilophosaurus has been found with this condition, this indicates that it more than likely had feathering.

A skull in the Royal Tyrell Museum

The most iconic part of Dilophosaurus is easily its crest. Unlike in Jurassic Park, the Dilophosaurus never had a frill - that was made up for the film, likely so audiences would not get it confused with the Velociraptors. The v-shaped crest shaped have often been disarticulated from the skull so for a while palaeontologists were not sure how it would go on the animal's head. Quite possibly the initial three specimens had their crests preserved, but as the expedition team did not know they existed consequently did not look for them. Initial reconstructions had the crest resting on the back of the skull and going onto the neck; this has since been rejected as it would restrict the neck's movement. Instead the crest started at the front of the skull and ended at the back. A real life equivalent could be the crest of a male cassowary, as shown below:

What were the crests used for? Initial theories of combat or thermoregulation have been rejected, so visual display is a likely function. Theropod dinosaurs likely could see bright colours as modern birds do, so the crests would be brightly coloured. Male Dilophosaurus would have the brightest crests in order to attract a mate, or scare off rival males. Finally, we have the jaw, which features a large notch in the upper jaw. This made it very weak - Dilophosaurus would be unable to break through bone. This led to questions about how or what it could eat - when writing Jurassic Park Michael Crichton theorised that they were venomous. We have no evidence for this, but palaeontologists have theorised how and what it ate.

Diet 

One of the biggest questions concerning the Dilophosaurus is its diet. With a weak jaw hunting down prey like a modern lion or wolf could be potentially dangerous. One wrong bite and its jaw would be broken. Different theories about how Dilophosaurus could have eaten. For one, it had very strong arms. Long, powerful arms, like a bear, could be used instead of its jaws to attack prey, and potential pack behaviour could improve the chances of a successful kill. One swipe could do serious damage, and an injured animal would be unable to escape when surrounded by other dinosaurs. Hence, its jaw would only need to be strong enough to tear flesh from a carcass, and even then the strong arms could also be used to break a carcass into smaller, manageable pieces. Some palaeontologists did suggest that Dilophosaurus was a scavenger, but as no living large animal exists entirely by scavenging this hypothesis has been rejected. A later theory suggested that the jaws weren't used for killing prey, but rather holding prey. Dilophosaurus lived alongside many smaller animals ranging from herbivorous dinosaurs to frogs, so they would be its primary food source. A Dilophosaurus would catch a small animal where its front teeth would slash the prey, by the time it reached the back of the jaws the prey would be too weak to resist. Andrew Milner and James Kirkland in 2000 suggested a new theory which has become increasingly accepted. The Kayenta Formation has been discovered to be rather wet, and many fish fossils have been found there. Most importantly, wading marks have been found from carnivorous dinosaurs indicating the diet of Dilophosaurus: fish. The strong arms show signs of being even able to grip prey so a diet of fish would be ideal. Like a bear, Dilophosaurus would wade into water where it would swipe up fish to eat in its weak jaws. Milner and Kirkland have found that Dilophosaurus had similar adaptations to the known fish-eating Spinosaurus: long teeth near the front of the skull to hold fish in place; long and strong arms; and nostrils further back in the skull to avoid water entering them. It is therefore likely that Dilophosaurus waded into water to catch fish and other aquatic life.

When and Where

The reconstructed model 'Dyzio' in the Geological Museum of the State Geological Institute in Warsaw

Dilophosaurus lived 193 million years ago in the Early Jurassic. Dinosaurs had begun to fully evolve as a distinct group during the Mid to Late Triassic, and the Late Triassic extinction left them as the dominant terrestrial group. At this time most of the best known dinosaur orders - like stegosaurids, sauropods, and tyrannosaurids - had yet to evolve. Dilophosaurus would have been one of the largest carnivores, especially as large terrestrial life had yet to bounce back from the Triassic-Jurassic extinction. This is also a reason why Dilophosaurus likely had a diet consisting of fish: there were few large herbivorous dinosaurs to hunt. We have currently only found Dilophosaurus in Arizona, but the formation group which the Kayenta Formation is part of comprise most of the South-west United States. We probably could have seen Dilophosaurus in this region as well. Unlike contemporary Arizona, the Kayenta Formation was humid and wet with plenty of lakes and rivers. Rivers preserve fossils well as the sediment protects specimens from the elements. The high number of well preserved specimens, including the first Dilophosaurus to be found, and high number of aquatic animals in the area show this. Dilophosaurus lived in an environment closer to modern Florida than modern Arizona.

Thank you for reading. The sources I have used are as follows:

-Gregory S. Paul, The Princeton Field Guide to Dinosaurs, Second Edition, (Princeton: Princeton University Press, 2016)

-S.P. Welles, 'New Jurassic Dinosaur from the Kayenta Formation of Arizona', GSA Bulletin, 65:6, (1954), 591-598

-S.P. Welles, 'Dilophosaurus (Reptilia: Saurischia), A New Name for a Dinosaur', Journal of Paleontology, 44:5, (1970), 989

-S.P. Welles, 'Dilophosaurus wetherilli dinosauria theropoda osteology and comparisons', Palaeontographica Abteilung A Palaeozoologie-Stratigraphie,185:4-6, (1984), 85-180

-Robert Gay, 'New specimens of Dilophosaurus wetherilli (Dinosauria: Theropoda) from the early Jurassic Kayenta Formation of northern Arizona', Western Association of Vertebrate Paleontologists Annual Meeting Volume Mesa, Arizona, 1:1, (2001)

-'Dilophosaurus', Prehistoric-Wildlife.com, [Accessed 12/07/2019]

-Phil Senter and Sara Juengst, 'Record-Breaking Pain: The Largest Number and Variety of Forelimb Bone Maladies in a Theropod Dinosaur', PLoS ONE, 11:2, (2016), 1-13

-Martin Kundrat, 'When did Theropods Become Feathered? - Evidence for Pre-Archaeopteryx Feathery Appendages', Journal of Experimental Zoology Part B: Molecular and Developmental Evolution, 320B:4, (2004), 355-364

-Andrew Milner and James Kirkland, 'The Case for Fishing Dinosaurs at St. George Dinosaur Discovery Site at Johnstone Farm', Survey Notes of the Utah Geological Survey, (2007), 39, 1-3

Thank you for reading and I hope you found it interesting. For other Paleo Profiles we have a list here, and for future blog updates please see our Facebook page or catch me on Twitter @LewisTwiby.

Paleo Profiles: Yi qi

A reconstruction of the Yi qi. From Emily Willoughby, emilywilloughby.com, (May 2015)

Today on Paleo Profiles we will be looking at a very unique dinosaur from Jurassic China: the Yi qi (Strange Wing). This bat like dinosaur is a recent discovery and shows us how diverse dinosaurs were. So let's look at China's bat-like 'Strange Wing'.

Discovery and Fossils

Currently, we only have own partial specimen of Yi and it was only formally described in 2015. It was initially discovered by a farmer called Wang Jianrong in Qinglong County back in 2007; he recognised it as a possible dinosaur fossil so he sold it to the Shandong Tianyu Museum of Nature. As often with fossil discoveries, it remained in storage until someone could formally describe the fossil in 2015. A group of ten palaeontologists evaluated the fossil including Xu Xing - Xu is one of China's most prominent palaeontologists describing, or co-describing, many major discoveries including the bird-like Microraptor and the fossil which showed tyrannosaurs were feathered, Yutyrannus. In 2015 their findings were published in Nature and the little dinosaur was named Yi. Although partial, major sections of the Yi has been preserved including the majority of the pigeon-sized body, parts of the skull, and imprints from a membrane which made up the animal's wings.

Biology

Examples of the Yi qi soft tissue

Yi was in a family known as Scansoriopterygids - a family which was closely related to the ancestors to modern birds. Three genera, including Yi, made up the Scansoriopterygids which are all biologically similar and lived alongside one another. The largest, and best known before 2015, was the Epidexipteryx due to it being the best preserved. However, for years it had been reconstructed incorrectly. Yi was the first Scansoriopterygid to be discovered with preserved membranes which connected the long fingers together, and palaeontologists, and paleo-artists, at times have a general fault of 'skin-wrapping' fossils. This means that non-mammalian fossils are regularly reconstructed with the skin tracing the skeletons - features like muscles, filaments, or extra skin are often overlooked. As a result Epidexipteryx was reconstructed without membranes leading to palaeontologists believing that it lived similar to a species of lemur called the aye-aye. The BBC documentary Planet Dinosaur reconstructed Epidexipteryx in this way as well:

The discovery of the Yi showed that Scansoriopterygids were not like aye-ayes, but really bats or more likely flying squirrels. This had been suggested before the discovery of Yi - most notably by Andrea Cau. Although we have the membrane of the Yi it is not fully preserved so there are several different reconstructions of the wing - the discoverers stated that 'the flight apparatus of Yi cannot be confidently reconstructed...However, the range of possible flight apparatus configurations can be explored by considering different reconstructions'. When first discovered the media reported it as being a 'dinosaur bat' but the paper itself disagreed with that interpretation - Yi just vaguely resembled one. They argued that based on realistic membrane placement it would be a glider. Yi and other Scansoriopterygids had long tail feathers which have traditionally been seen as being for display. Likely that it still true, possibly brightly coloured it could be used to assert dominance or attract a mate, like with the feathers of a male peafowl. With the Scansoriopterygids they were also possibly used to help the dinosaurs glide - like the tail on a flying squirrel it could act as a rudder to steer. It did not have the exact body for relying solely on gliding so it could possibly rely on short bursts of powered flight.

One of the key discoveries associated with Yi and other Scansoriopterygids are the presence of feathers covering the body. They were closely related to the ancestors of modern birds, just instead being an evolutionary dead end, so it would be natural for them to be covered in feathers - albeit these were simple feathers, not something you would expect to see on a fully grown modern bird. Nevertheless, by use of an electron microscope it is possible to know, vaguely, what colour the feathers were. Preserved pigments leads us to believe that Yi had black feathers except on the head which was a yellow-brown hue. Yi and its cousins were perfectly adapted to life in the trees with flattened bodies and long fingers which allowed it to grip hold of tree trunks. The diet of Yi is still unknown but reasonable guesses can be made. Teeth and the presence of pterosaurs in the area with similar teeth would suggest that Scansoriopterygids were primarily insectivores, although their diet could include berries.

When and Where
Yi and other Scansoriopterygids lived during the Jurassic period, in particular the Callovian or Oxfordian, around 160 million years ago. During this time the world was warmer, wetter, and richer in oxygen. Where Yi came from was no exception. The Tiaojishan Formation in Northeast China has been believed to be either a sub-tropical or temperate climate, as well as being both warm and humid based on fossilised tree rings. As a result, the Yi would never experience the cold. Based on its arboreal lifestyle, and limited ability to undertake powered flight, this would mean that the Yi would be limited to forests. The region was very volcanic. Tiaojishan Formation has many layers showing occasional ash fall from volcanic eruptions - something that many Chinese fossil sights experienced. This is why Chinese dinosaurs are so well preserved that they regularly show evidence of feathers. Ash buries and preserves those unfortunate enough to be caught in the cloud - just think of how well-preserved the unfortunate victims of Pompeii are. Consequently, Chinese fossil sites every year gives us more and more well-preserved dinosaur remains - Yi is far from the only dinosaur that we know what colour they were due to their pigments being preserved.

Neighbours

A Jeholopterus, a pterosaur which lived alongside Yi

Yi had a wide variety of animal life living alongside it. Among these included the other two Scansoriopterygids genera, Scansoriopteryx and Epidexipteryx, but both were a lot smaller than the Yi. In fact, three of the smallest dinosaurs lived at the same time in the same place - Scansoriopteryx, Epidexipteryx, and Aurornis. Other arboreal dinosaurs resembled modern birds - such as Anchiornis - and likely competed with Yi. Pterosaurs were common in the region with around fifteen species being known to live alongside Yi. The Scansoriopterygids were not the only gliding animals - the flying squirrel like Volaticotherium could be found in the Tiaojishan forests. What about terrestrial dinosaurs? There are a few including a heterodontosaurid called Tianyulong and a few dinosaurs, including Anchiornis, lived alongside them. From other Chinese fossil sights around the same time we do know larger dinosaurs were roaming Jurassic China - such as Sinraptor, actually a relative of Allosaurus and not raptors. There is a possibility that a large carnivore related to Sinraptor stalked the land.

Thank you for reading. The sources I have used are as follows:
-Xing Xu, Xiaoting Zheng, Corwin Sullivan, Xiaoli Wang, Lida Xing, Yan Wang, Xiaomei Zhang, Jingmai K. O’Connor, Fucheng Zhang, & Yanhong Pan, 'A Bizarre Maniraptoran theropod with preserved evidence of membranous wings', Nature, 521:7550, (2015), 70-73
-'Yi', prehistoric-wildlife.com, [Accessed 20/03/2019]
-'Epidexipteryx', prehistoric-wildlife.com, [Accessed 20/03/2019]
-Gregory S. Paul, The Princeton Field Guide to Dinosaurs, Second Edition, (Princeton: Princeton University Press, 2016)
-Trey the Explainer, 'Paleo Profile - Yi qi', Youtube, (29/04/2015), [Accessed 20/03/2019]
-Wang Yongdong, Saiki Ken'ichi, Zhang Wu, and Zheng Shaeolin, 'Biodiversity and palaeoclimate of the Middle Jurassic floras from the Tiaojishan Formation in western Liaoning, China', Progress in Natural Science, 16:9, (2006), 222-230

Paleo Profiles: Brachiosaurus

Today on Paleo Profiles we're looking at one of the best known dinosaurs to ever walk the face of the planet: Brachiosaurus. When first discovered it was described as being 'the largest known dinosaur' and is one of the dinosaurs which come to mind when we think of the prehistoric reptiles. One of the most iconic scenes in Jurassic Park featured the Brachiosaurus - when we first fully see a dinosaur. However, quite ironically our image of the Brachiosaurus over the last decade has been shown to be inaccurate - another dinosaur for almost a century believed to be Brachiosaurus was used for reconstructions.

Discovery and Fossils

An excavator next to the humerus of a Brachiosaurus

Dentist and amateur collector Stanton Merill Bradbury wrote to palaeontologists believing that he had found signs of dinosaur fossils. He struck up a conversation with one in particular - Elmer Riggs - who believed they were more likely to be mammal fossils from the Eocene, a time not too long after the dinosaurs went extinct. Going out to Colorado in 1900 he discovered something far bigger than any mammal to walk the land. During excavation they happened upon the humerus which was so long that Riggs thought it be to a deformed femur - the longest bone in the body. He quickly surmised that the bones were from a group of dinosaurs called sauropods - large herbivorous dinosaurs characterised by long necks and tails. At first he believed it to be an Apatosaurus but looking at the ribs realised it was a new animal. Due to the length of the femur and the size of the animal's chest he named it Brachiosaurus altithorax - 'Arm lizard of deep chest' - in 1903. The specimen wasn't complete - it lacked a head for one - but other specimens were discovered. In 1914 German palaeontologist Werner Janensch found several specimens from the Tendaguru Formation in what is now Tanzania which he described as being two new species of Brachiosaurus - B. altithorax and B. fraasi. However, since then, as well as another one from Portugal and a much younger specimen, they have been separated into a new genus entirely. The African species were reclassified as Giraffititan and most reconstructions were based on Giraffatitan before it was known to be distinct.

We have discovered several different specimens of Brachiosaurus since the initial one in 1900. However, they are far from complete, and it is only because of how closely Brachiosaurus resembles its African cousin that we picture what it looked like. In fact, the most complete specimen that we have is from a sub-adult so it died before all of its bones could fuse together. In 2012 in Wyoming a 2-metre long skeleton missing a skull was discovered, and for some time was it was initially thought to be a diplodocid. In 2018 a foot was discovered, the largest to be discovered in the region, in Wyoming but missing the femus - it is thought to be the largest Brachiosaurus discovered based on the foot's size.

Biology

Femur (left) and the humerus (right) of a Brachiosaurus

As mentioned Brachiosaurus was a sauropod which were some of the largest land animals to ever exist - a giant named Patagotitan weighed the same as 10 African elephants. Brachiosaurus was a giant in both height and weight. With what fossil evidence we have it is very difficult to estimate how much one weighed so we have results varying from 28 metric tons to a staggering 58 tons! To put it in perspective, the smallest estimate will put Brachiosaurus as weighing the same as four and a half bull African elephants. Sauropods normally had long tails to act as a counterbalance their long necks so Brachiosaurus had a shorter but muscly tail - about 7 metres in length. A large part of this is due to the dinosaur's neck posture - although long it was held in an S-pose or at an angle. Past depictions in museums, which continue in popular media, try and portrayed extinct animals as large as they could, so Brachiosaurus was portrayed holding its long neck directly upwards. Instead, it likely would have held it at a slight angle in the same way that giraffes do. From snout to tail the Brachiosaurus was around 26 metres long. Due to their size it was once believed that sauropods were aquatic using the water to support their immense size - Elmer Riggs argued against this when he described the Brachiosaurus. The theory has, for a very longtime, been disproved - if anything the water could have crushed the dinosaur's chest.

A Giraffatitan in the Berlin Natural History Museum

Most of what we know about Brachiosaurus comes from what we know about Giraffatitan. Luckily, several important parts of the dinosaur is known. The arms were exceptionally long, the humerus was longer than the femur causing confusion for Riggs, making the shoulders very high. This allowed Brachiosaurus to be like a giraffe and browse from the tops of trees. Like many other sauropods the feet were wide, mostly for balance, but they could also be used for communication. Elephants make rumbles which humans cannot detect which travel along the ground - their wide feet pick up these rumbles. Quite possibly sauropods did so as well. How did such a large animal function? Steven Perry and Christian Reuter have hypothesised what types of lungs the dinosaur would have, and they believed that one found in birds would be the best. In 2016 Mark Hallett and Mathew Weddel used Brachiosaurus to find how sauropods managed to breathe. Instead of acting like a bellows, as in our lungs, birds have 'air sacs' where one pumps in air and another pumps waste out allowing quick air exchange. Sauropods had openings in their bones to allow air sacs to sit in and pump the oxygen to their muscles. As we discover more fossils we have begun to understand that all dinosaurs were closer to birds than crocodiles - before the discovery of the air sacs it was thought that if it was warm-blooded Brachiosaurus would overheat. Air sacs also served to cool the body so they were likely endothermic and homeothermic. 

A reconstructed skull in the Denver Museum of Nature and Science

Finally, we get to the skull - the most iconic and yet dubious part of the dinosaur. We only have a partial skull and most reconstructions are based on Giraffatitan. There were enough distinctions between the two skulls, however, to present evidence that they were distinct. The skull was small for its size - so small, in fact, that Fabien Knoll and Daniel Schwarz-Wings believed that they could not accurately work out the animal's intelligence. A key feature of the skull is the crest and there have been various theories about what its use was. One major theory is that these crests were where the nostrils were located; as the animal drank it could keep its nostrils out of the water. Another theory has been suggested that they were really a resonating chamber for communication. Finally, we have the dinosaur's teeth. These chisel-shaped teeth were replaced across the animal's life, and would nip off vegetation. Brachiosaurus could not chew - instead it had to slice through vegetation with its very muscular jaws and leave the rest to ferment in its gut. Due to that it had to eat a lot - possibly up to 400 kg of foliage a day.

When and Where

Brachiosaurus lived around 154 million years ago in the Jurassic period - in the original Jurassic Park it is one of two dinosaurs to appear on-screen which actually came from the Jurassic. The supercontinent Pangea had started to break apart, most of the world was humid, and the air was rich in oxygen. Brachiosaurus was found in the Morrison Formation - perhaps the most famous dinosaur fossil formation, tied with the home of the Tyrannosaurus Hell Creek. Today it covers a huge area of the US; most of it is in Colorado and Wyoming with outreaches into Montana, North and South Dakota, Nebraska, Kansas, and even parts of Oklahoma and Texas. The Great Hall of Dinosaurs at Yale's Peabody Museum even has a mural by Rudolph Zallinger entitled The Age of Reptiles mostly depicts the inhabitants of Morrison Formation. The Morrison Formation was made of semiarid most of the year with the exception of the wet seasons - floodplain prairies and riverine forests were where Brachiosaurus could be found.

Neighbours

Zallinger's now outdated mural depicting some of the Morrison Formation dinosaurs

The Morrison Formation was rich in dinosaur life. Brachiosaurus was far from the only sauropod - Diplodocus, Camarasaurus, Apatosaurus, Brontosaurus, and Barosaurus were just some of the sauropods to call Morrison Formation their home. Brachiosaurus likely filled the same role as a giraffe; competition with other sauropods would drive it to reach the top of the trees, out of the way of the shorter sauropods. Other herbivores lived alongside the sauropods including nimble Dryosaurus and the formidable Stegosaurus. An adult Brachiosaurus had few natural predators - much like an elephant they were too big to attack without injury. However, younger ones had several potential predators. The horned Ceratosaurus, giant Torvosaurus and Saurophaganax, and the 'Lion of the Jurassic' Allosaurus all could prove deadly for a growing Brachiosaurus. As the Morrison Formation had floodplains and rivers which could easily burst their banks or flood the land during the wet season. These flash floods could easily drown helpless dinosaurs, and these floods help preserve their fossils. As a result, we know quite a bit about fauna in Jurassic Colorado and Wyoming, and every year we make new discoveries. 

Thank you for reading. The sources I have used are as follows:

-Gregory S. Paul, The Princeton Field Guide to Dinosaurs, Second Edition, (Princeton: Princeton University Press, 2016)

-Steve Brusatte, The Rise and Fall of the Dinosaurs: The Untold Story of a Lost World, (London: Macmillan, 2018)

-Mark Hallett and Mathew Wedel, The Sauropod Dinosaurs: Life in the Age of Giants, (Baltimore: Johns Hopkins University Press, 2016)

-'Brachiosaurus', Prehistoric-wildlife.com, [Accessed 06/02/2019]

-'Giraffatitan', Prehistoric-wildlife.com, [Accessed 06/02/2019]

-E.S. Riggs, 'Brachiosaurus altithorax, the largest known dinosaur', American Journal of Science, 4:15, (1904), 299-306

-Micahel Taylor, 'A Re-evaluation of Brachiosaurus altithorax Riggs 1903 (Dinosauria, Sauropoda) and Its Generic Separation from Giraffatitan brancai (Janensch 1914)', Journal of Vertebrate Paleontology, 29:3, (2009), 787-806

-Steven Perry and Christian Reuter, 'Hypothetical Lung Structure of Brachiosaurus (Dinosauria: Sauropoda) Based on Functional Constraints', Fossil Record, 2:1, (1999), 75-79

-Fabian Knoll and Daniela Schwarz-Wings, 'Palaeoneuroanatomy of Brachiosaurus', Annales de Paléontologie, 95, (2009), 165-175

-Anthony Maltese, Emanuel Tschopp, Femke Holwerda, and David Burnham, 'The real Bigfoot: a pes from Wyoming, USA is the largest sauropod pes ever reported and the northern-most occurrence of brachiosaurids in the Upper Jurassic Morrison Formation', PeerJ, 6, (2018)

Thank you for reading. As this is a hobby of mine, not my speciality, if you feel that I have got something wrong or have omitted something please mention it in the comments. For other Paleo Profiles please see our list. For future blog updates please see our Facebook or catch me on Twitter @LewisTwiby.