Xiphactinus: The Beautiful Bull of the Sea

File:XiphactinusDB cropped.png - Wikimedia Commons
An artists impression of Xiphactinus, showcasing its characteristic face, jaws and Tarpon-like body.
Image Credit: Dmitry Bogdanov, https://commons.wikimedia.org/wiki/File:XiphactinusDB_cropped.png

The large (but masked and socially distanced) crowd bubbled with excitement as the artist they had come to see readied himself for the presentation of his masterpiece. Behind him is a large rectangular box covered by a brown sheet. His nervous hands sending flutters through the sheet he is holding, he readies himself for the biggest moment of his life.

“This is my latest and greatest work. An unknown fish pulled from the deep ocean, presented and preserved in exquisite detail in the box behind me using a formalin solution!”.

“I give you. Beauty!”

The artist pulls off the sheet, revealing a 5 metre long fish with upturned, bulldog like jaws filled to the brim with razor sharp teeth! The crowd are in complete shock. Beauty is not a word that comes into their mind. After the surprise wears off the crowd grumble their disappointment.

“Is this another example of unfathomable modern art? One naysayer says.

“Didn’t Damien Hirst once do something like this?” another asks

“I don’t get it? It’s just a weird looking fish?” yet another comments

After a while the crowd, once expectant and now disappointed, move on. The sounds of their footsteps carrying them away from the scene are accompanied by the cries of despair of the disappointed artist. Eventually only one person remains. A shaggy haired man who looked like he hadn’t had a haircut for months stares intently at the fish. He approaches the artist, who is wiping away his tears.

“Firstly, that is indeed beautiful!”

“Oh really?! That means so much! Thank you!” the artist replies with excitement.

“Secondly” the shaggy haired man continues. “Where did you get this fish?! It’s supposed to have been extinct for 66 million years?!!”

First discovered in Kansas, USA, in 1870 and named by Professor Joseph Leidy of the University of Pennsylvania; Xiphactinus (Latin for “Sword-Ray”) was a huge fish that had the size and power to compete with the large Sharks and even the medium sized Mosasaurs that it shared the oceans with. Two species of Xiphactinus are currently known to science. The first is Xiphactinus audax. This was the first species discovered, and is the larger of the two. X.audax had a wide geographical range, with fossils being discovered across North America from Saskatchewan in Canada, to Texas, New Jersey, Mississippi, Georgia and Delaware in the United States. The second species is Xiphactinus vetus. This species was discovered much more recently in 1997 and is known from the Eastern United States. This large range is just the North American distribution however! Fragments of an upper jaw bone and vertebrae from Xiphactinus audax were discovered in Patagonia in Argentina, South America, and described in 2020. These finds have expanded its range much further south west than was previously thought. Furthermore Xiphactinus fossils have also been unearthed in Western Europe and even as far as Australia. This almost worldwide distribution indicates that you would’ve had a good chance of spotting a Xiphactinus no matter where you ventured in the Late Cretaceous seas and that this multi-fanged fish was an incredibly successful animal for its time.

The most striking feature of Xiphactinus was undoubtedly its short, bulldog like face complete with a protruding and upturned lower jaw. This face was attached to a sleek, streamlined body complete with a “wing-like” pair of pectoral fins, a backward pointing dorsal fin, downward facing pelvic and anal fin, a broad tail and smooth scales. In essence Xiphactinus would’ve looked like a modern day Tarpon but larger and with a blunter, more fanged-teeth filled face. Just like the tarpon Xiphactinus was built for speed. Powerful strokes from its tail accelerated it through the water, and combined with jaws filled with large and sharp teeth would’ve made Xiphactinus a formidable hunter. This appearance is unique and begs the question; who was Xiphactinus related to? Well, Xiphactinus was a member of the Teleosts, a large group of bony fish which are also known as the “Ray-Finned Fish”. Teleosts are a massively successful group, so much so that they make up nearly 96% of all modern fish species, and nearly half of all modern vertebrate species. Yes, this includes ALL mammals, birds, reptiles, amphibians and other fish alive today! Within this huge Teleost group Xiphactinus belonged to a family known as the Icthyodectidae; a family of fish that became totally extinct at the end of the Cretaceous period 66 million years ago, leaving no living descendants.

The diet of Xiphactinus included Fish, Small Marine Reptiles, Ancient Seabirds (e.g. Hesperornis, a flightless human sized seabird from the USA) and even Pterosaurs. These potential prey items would have not been easy to catch. But Xiphactinus had a secret weapon. It is theorized that it was endothermic, meaning that it could generate and maintain a higher body temperature than the surrounding environment (in a similar way to mammals and birds). This is actually not unheard of for a fish, who are usually thought to be exothermic, meaning their body heat is determined largely by their surroundings. Bluefin Tuna, Swordfish and Great White Sharks are also able to maintain a higher body temperature, independent of their environment. This strategy gives them the potential to produce the heat (and therefore energy) required to be fast active predators who can swim at high speeds. With this in mind maybe Xiphactinus could’ve leapt out of the water to grab flying animals or while hunting water bound animals in a manner akin to a Great White Shark! Obviously this is speculative behaviour, but what a sight that would have been if it did pull off such manoeuvres! Some remarkable fossils of Xiphactinus have allowed palaeontologists to gain further insight into its hunting behaviour. One fossil, discovered in 1952 at Smokey Hill in Kansas, USA, and stored in the Sternberg Museum (also in Kansas), preserves a complete 4 metre long Xiphactinus skeleton in the process of swallowing a 2 metre long fish named Gillicus. That’s right this Gillicus was half the size of Xiphactinus! It seems that this Xiphactinus perished due to a combination of choking and its internal organs being punctured by the struggling Gillicus. Such a hunting strategy would also helped explain the large fang like teeth and upturned jaw. The teeth would’ve pierced and held the animal in place while the up and down movement of its lower jaw would’ve helped Xiphactinus gulp down its prey. With this beautiful fossil in mind, it’s almost a good thing that Xiphactinus isn’t swimming around in today’s oceans. Being swallowed alive by one would not have been a fun way to go!

File:Xiphactinus audax Sternberg Museum.jpg
The “Fish within a fish” fossil of a Xiphactinus and a Gillicus on display at the Sternberg Museum in Kansas, USA.
Image Credit: Spacini, https://commons.wikimedia.org/wiki/File:Xiphactinus_audax_Sternberg_Museum.jpg

Despite its size and fearsome appearance Xiphactinus was NOT the top predator in its seas. A Xiphactinus audax individual, estimated to have been “only” 3 metres long, discovered in Kansas, and described in 2004, was found to have a shark tooth embedded in its third vertebrae. This tooth belonged to an estimated 3.1 metre long specimen of a Late Cretaceous shark called Cretoxyrinha. What seems to have happened is that the shark inflicted a powerful bite into the back of the Xiphactinus, breaking off and embedding one of its teeth in its vertebrae in the process. While it is not clear whether the shark was actively hunting Xiphactinus, or if it was just scavenging its remains, it is clear is that the two species not only co-existed in the same place and at the same time but also actively interacted with each other. As well as Cretoxyrinha, Xiphactinus would’ve had to look out for other large oceanic predators. One such group were the Mosasaurs; Marine Reptiles that were closely related to lizards and snakes. These Mosasaurs included the 13 metre long Tylosaurus and the 15 metre long Mosasaurus (see my article on Mosasaurus for more about these fascinating sea faring reptiles!), both of whom were powerful predators with strong bites. All of these animals lived together in a large sea known as the “Western Interior Seaway”. This was an ancient sea that covered the middle of North America, and was so big that it split the continent into two large islands; Laramidia to the west (which is where the famous dinosaurs Tyrannosaurus and Triceratops lived) and Appalachia to the east. With Xiphactinus, Cretoxyrinha and the Giant Mosasaurs lurking in the water it’s no wonder that Nigel Marven in the BBC documentary “Sea Monsters” called this Late Cretaceous Sea “Hells Aquarium”! Despite Tyrannosaurus rex stalking Laramidia at the time, you arguably would have been better off sticking to the land!

However despite being incredibly successful and widespread, Xiphactinus would end up being lost to extinction. 66 million years ago a large asteroid 10km wide smashed into the Yucatan Peninsula in Mexico. This resulted in an extinction event known as the “K/T” Extinction Event, which was so devastating that an estimated 70% of all living species at the time went extinct. While it is best known for wiping out all of the Non-Avian (or “non-bird”) Dinosaurs it also had a massive effect on marine life. When the meteorite smashed into the earth it led to the release of massive amounts of sulfur from impacted rocks into the atmosphere, causing a worldwide “rain out” of sulfuric acid. This resulted in a big drop in the pH of the oceans, making them more acidic. This ocean acidification in turn prevented calcifying foraminifera and other tiny invertebrates from making their shells (as the low pH would dissolve the shells before they formed). Furthermore a number of plankton and algae species sensitive to pH changes were badly affected, leading to a mass die off of these species. These tiny organisms may not seem like much but they are the foundations for the survival of all marine life further up the food chain. Once these small species disappeared, there was a massive ecological collapse. This was because the fish that ate the plankton died off from starvation, and then in turn fish that ate those fish died off. It was this horrible domino effect that ultimately ended up causing the extinction of Xiphactinus as eventually there was not enough food to support them. In fact marine life was so badly affected by the K/T extinction event that it would take roughly 3 million years for marine ecosystems to fully recover.

In conclusion, Xiphactinus may not have been the most attractive of prehistoric animals, but it was unique, innovative and successful. It deserves to be regarded as an iconic prehistoric animal, and perhaps the most successful large predator of the Late Cretaceous seas!

File:Styxosaurus and Xiphactinus.jpg - Wikimedia Commons
Xiphactinus would’ve co-existed with many strange creatures in the Western Interior Seaway, including Styxosaurus; a Marine Reptile that was a member of the Plesiosaur group.
Image Credit: ABelov2014, https://www.deviantart.com/abelov2014/art/Styxosaurus-Xiphactinus-audax-var-1-658020267

References/Further Reading

Ferrón 2019: a paper that built upon previous work and provided further evidence for endothermy in Xiphactinus

Humberto G. Ferrón (2019) Evidence of endothermy in the extinct macropredatory osteichthyan Xiphactinus audax (Teleostei, Ichthyodectiformes), Journal of Vertebrate Paleontology, 39:6, DOI: 10.1080/02724634.2019.1724123

Shimada & Everhart 2004: a paper reporting on a Xiphactinus fossil that possesses bite marks made by a large shark

Shimada, K., & Everhart, M. J. (2004). Shark-bitten Xiphactinus audax (Teleostei: Ichthyodectiformes) from the Niobrara Chalk (Upper Cretaceous) of Kansas. The Mosasaur, 7, 35-39.

Schwimmer & Stewart 1997 paper describing the second species of Xiphactinus; Xiphactinus vetus.

Schwimmer, D., et al. (1997). “Xiphactinus vetus and the distribution of Xiphactinus species in the eastern United States.” Journal of Vertebrate Paleontology – J VERTEBRATE PALEONTOL 17: 610-615.

Everhart, Hageman & Hoffman 2010 journal article talking about another “fish within a fish” fossil discovery similar to the Xiphactinus/Gillicus specimen.

Everhart, Michael J., et al. “Another Sternberg ‘Fish-within-a-Fish’ Discovery: First Report of Ichthyodectes Ctenodon (Teleostei; Ichthyodectiformes) with Stomach Contents.” Transactions of the Kansas Academy of Science (1903-), vol. 113, no. 3/4, 2010, pp. 197–205. JSTOR, www.jstor.org/stable/41309609. Accessed 3 Jan. 2021.

Henehan et. al. 2019 paper on the ocean acidification that occurred in the worlds oceans during the K/T extinction event 66 million years ago.

Henehan, M. J., et al. (2019). “Rapid ocean acidification and protracted Earth system recovery followed the end-Cretaceous Chicxulub impact.” Proceedings of the National Academy of Sciences 116(45): 22500-22504.

An online copy of a chapter from Richard Cowans 1999 book titled “History of Life” which details the effects of the K/T extinction

Cowan, Richard, “The K/T Extinction”, History of Life, 1999, www.ucmp.berkeley.edu, https://ucmp.berkeley.edu/education/events/cowen1b.html

The Prehistoric Wildlife website factfile on Xiphactinus

Prehistoric Wildlife, “Xiphactinus”, www.prehistoric-wildlife.com, http://www.prehistoric-wildlife.com/species/x/xiphactinus.html

A short National Geographic profile on Xiphactinus

National Geographic “Xiphactinus audax”, Animals Photo Ark, nationalgeographic.com, https://www.nationalgeographic.com/animals/prehistoric/xiphactinus/

A University of Pennsylvania archives fact file on Professor Joseph Leidy, who first described and named Xiphactinus in 1870

University of Pennsylvania, “Joseph Mellick Leidy”, www.archives.upenn.edu.com, https://archives.upenn.edu/exhibits/penn-people/biography/joseph-mellick-leidy

Yutyrannus: The Feathered Tyrant

Image result for yutyrannus
Reconstruction of Yutyrannus huali, Feathers and all!
Image Credit: Tomopteryx, https://commons.wikimedia.org/wiki/File:Yutyrannus_huali.png

Tyrannosaurs are arguably the most famous members of the great dinosaur pantheon. Their traditional look has been set in stone in the public eye for decades, being immortalised in various media, of a giant scaly lizard with tiny arms and a massive head full of sharp, banana shaped teeth. However what if I were to tell you that this picture isn’t completely accurate, and that at least some tyrannosaurs were in fact a lot more on the soft and fluffy side! While it’s still being debated to this day whether the mighty Tyrannosaurus Rex had feathers (a story for another blog!), there was another tyrannosaur that not only possessed feathers, but was completely covered in them! Revealed to the world in 2012 Yutyrannus huali (meaning “Beautiful Feathered Tyrant” in a mix of Mandarin and Latin) shaked pre-existing ideas about Tyrannosaurs to the core.

Yutyrannus was discovered in the Yixian formation, in the Liaoning Province of China by a Chinese palaeontologist named professor Xing Xu. This particular corner of the world is extremely rich in dinosaur fossils, mostly dating to the Early Cretaceous period (125 million years ago). A large majority of the feathered dinosaur finds in the last few decades originated from this area. Xu is a big name in the world of contemporary palaeontology as described and named a lot of these feathered dinos, such as the “four winged” Microraptor and another feathered tyrannosaur called Dilong. The Yutyrannus fossils discovered by Xu and his team consisted of an adult and two juveniles, all of them almost complete. This is remarkable as tyrannosaurs are often only known from incomplete fossils. So in this case we have a vividly detailed picture of this particular animal.

One of the most surprising observations about Yutyrannus is not only that it had feathers, but that this was a big animal. Previously other known feathered tyrannosaurs, such as Dilong and Guanlong (both also discovered in China), were relatively small; ranging around the sizes as modern big cats. However Yutyrannus bucked this trend by growing up to 9 metres long, 3 metres tall and weighing up to 1 and a half tonnes. This makes Yutyrannus the largest animal with direct definitive evidence of feathers ever discovered. While other dinosaurs like Therizinosaurus and Gigantoraptor are likely to have had feathers, there’s been no direct evidence found yet, so Yutyrannus keeps the crown for now. Unlike other large tyrannosaurs Yutyrannus shares many features with other early tyrannosaurs, such as possessing three fingers instead of two and a lack of a specialised weight-bearing middle toe (used by later tyrannosaurs to support their weight). By comparing its anatomy with other tyrannosaurs it was also deduced that Yutyrannus was not a direct ancestor to T-Rex, but instead belonged to a family of tyrannosaurs that split off during the Early Cretaceous, meaning that Yutyrannus was essentially T-Rexs great great uncle. Unlike later Tyrannosaurs Yutyrannus also possessed a small, midline crest at the end of its snout. This could have been used to attract a mate or to signal other individuals, saying for example “I’m the biggest and baddest of the Yutyrannus! Keep away!”. As the fossils were of an adult and two juveniles this could potentially be a family group. It has been theorised that tyrannosaurs may have lived in groups, so perhaps this find represents the sad end of a mum or dad raising its offspring.

Size comparison between a full grown Yutyrannus and a fully grown human. As you can see this was certainly a large feathered animal!
Image Credit: Conty, https://en.m.wikipedia.org/wiki/File:Yutyrannus_SIZE.png

The feathers themselves have been found preserved in patches across the whole body of all 3 fossils. In life they were relatively simple “proto-feathers”, consisting of long simple filament like structures. These filaments would have intertwined to produce a fluffy down; somewhere between the down on a baby chicken and the longer, fibrous feathers of an emu. The primary function is likely to have been to keep Yutyrannus warm. A study by Amiot et. al. in 2011 looked at oxygen isotope compositions found in reptile fossils from East Asia. These seem to indicate that at the place and time where Yutyrannus lived was a relatively cold, compared to the hothouse that was the rest of the Mesozoic, so a feathery coat would have helped to keep an active hunter like Yutyrannus at the right temperature. Other possible usages of this coat of feathers could have been to assist with attracting mates, as has been speculated to have been the case in other feathered dinosaurs (e.g. Caudipteryx), and any shed feathers could have been used to line their nests, as it is employed by modern birds. It has even been suggested that the colour of the feathered coat would have helped Yutyrannus camouflage itself against its surroundings, a trick that is employed by most predators today. Some reconstructions have given Yutyrannus a fully white coat to blend in with a snowy background (like a polar bear). While this is a neat bit of speculation, it can’t be proven until any melanosomes that may be preserved are examined. If so then palaeontologists would be able to discover the colour of a tyrannosaur for the first time!

An illustration showing a group of Yutyrannus hunting a juvenile Dongbeititan
Image Credit: PaleoEquii, https://commons.m.wikimedia.org/wiki/File:Dongbeititan_and_Yutyrannus.jpg

A lot of criticism of these feathered dinosaurs, and particularly with ideas about feathers existing on dinosaurs that were previously thought to be scaly, is that it makes dinosaurs “less cool looking” and more like giant turkeys. However I think that Yutyrannus is an excellent example of how feathers can enhance the interest in dinosaurs, providing another side to how we see these great lizards. An animal like this would certainly make a cute pet when it’s young. However, like pet owners who buy young tiger cubs, it’ll grow up over the years into a giant unmanageable carnivore, leaving the owner thinking “I REALLY didn’t think this through!”

References/Further Reading

Xu et. al. 2012 paper describing the 3 complete skeletons of Yutyrannus, including the description of its feathers

Xu, X., Wang, K., Zhang, K. et al. A gigantic feathered dinosaur from the Lower Cretaceous of China. Nature 484, 92–95 (2012). https://doi.org/10.1038/nature10906

American Museum of Natural History blog on getting to know Yutyrannus

AMNH, “Get to Know a Dino: Yutyrannus huali”, American Museum of Natural History, Apr. 11, 2016, amnh.org/explore/news-blogs/on-exhibit-posts/get-to-know-a-dino-yutyrannus-huali

Amiot et. al. 2011 paper on oxygen isotope compositions in fossils from the Early Cretaceous East Asia

Amiot, Romain et al. “Oxygen isotopes of East Asian dinosaurs reveal exceptionally cold Early Cretaceous climates.” Proceedings of the National Academy of Sciences of the United States of America vol. 108,13 (2011): 5179-83. doi:10.1073/pnas.1011369108

A National Geographic article, written by Cliff Tarpy, about the fossils of Liaoning

Tarpy, Cliff, “Liaoning Province—China’s Extraordinary Fossil Site”, National Geographic, nationalgeographic.com/science/prehistoric-world/china-fossils/

Leaellynasaura: A dinosaur that called the South Pole home

A drawing of the South Poles resident dinosaur Leaellynasaura
Image Credit: El fosilmaníaco, https://commons.m.wikimedia.org/wiki/User:El_fosilman%C3%ADaco

It’s hard to imagine any land based animal living at the South Pole. The frozen wastes, completely prevents any significant plant growth, complete darkness covers the area for about half the year, and temperatures are nearly always well below freezing. This results in an environment where the largest life-form is no more than microscopic. However for a sizeable chunk of earth’s history there was no permanent ice cap at the South Pole. Instead temperate forests covered the continents that were located there. During the Early to Mid-Cretaceous period, (around 105-110 million years ago), a landmass that would eventually break up to become Antarctica and Australia was present at the south pole of our planet. If you trekked through this land, often with only the southern lights illuminating the landscape, you might be able hear the chirps of a small, unassuming little dinosaur piercing the otherwise silent frozen forest. These sounds belonged to an ornithopod known as Leaellynasaura amicagraphca (Latin for “Leaellyn’s lizard”, with “amicagraphica” referring to the friends of Museum Victoria who helped with the research).

When a prehistoric animal is given its scientific name, the usual procedure is to either; 1. Name it because of a distinguishing feature; 2. Name it after the area it was discovered in; or 3. Give it an eye catching name that involves the words “terror” or “massive” or “weird”. However Leaellynasaura bucks this trend by instead being named after Leaellyn Rich, the young daughter of Palaeontologists Thomas and Patricia Rich, who first discovered Leaellynasaura in 1989 (a great present for any person!). The fossils were found at a place known as Dinosaur Cove, which is located just outside of Melbourne, Australia. This site, and others in Australia, have shown that Leaellynasaura lived alongside a wide range of other animals. This included other dinosaurs, such as the large vegetarian iguanodontid Muttaburrasaurus and the mid-sized hunting theropod Australovenator, as well as a giant 5 metre long amphibian named Koolasuchus. Fans of the hit BBC documentary “Walking with Dinosaurs” might recognise some of the names I’ve just mentioned. This is because the fifth episode, titled “Spirits of the Ice Forest”, is actually based on this fossil assemblage.

A selection of Leaellynasaura amicographica fossils.
Image Credit: Kumiko, https://www.flickr.com/photos/kmkmks/8086848566/

Leaellynasaura itself was a small dinosaur, with estimates varying between 1-3 metres. It is unclear what specific group of Ornithopod Dinosaurs it belonged to, however it is similar in anatomy to the Hypsilophodontids (try saying that five times fast!). These dinosaurs are characteristically small, bipedal, nimble herbivores, using their beaks to browse vegetation, all whilst scampering between larger herbivores (the best modern analogue might be modern day Gazelles). When you look at the skeleton of Leaellynasaura a few features stand out. Firstly it had large eye sockets relative to its skull. Combined with a large optic lobes in its brain cavity this suggests that Leaellynasaura had excellent eyesight, allowing it to spot predators and locate juicy plants to eat. Secondly its tail was very long, nearly 3/4 of its entire length! This tail contained over 70 vertebrae and lacked many of the ossified tendons involved in stiffening and strengthening the tail of other dinosaurs. This means that Leaellynasaura probably possessed a remarkably flexible tail, capable of a wide variety of movement (maybe even curling round up and around its body). The function of this long tail is unclear at the moment, though it has been theorised that it was involved in display, especially when combined with any feather covering that it likely possessed.

Size comparison between Leaellynasaura amicagraphica and an adult human. Note Leaellynasaura’s proportionally long tail that takes up 2/3rds of its total length!
Image Credit: Slate Weasel, https://en.m.wikipedia.org/wiki/File:Leaellynasaura_Size.svg

The biggest challenge that Leaellynasaura would have faced would have certainly been surviving the elements. As Dinosaur Cove was located well within the Antarctic Circle it would have endured the same seasonal variations that Antarctica does today; 6 months of near permanent sunshine followed by 6 months of near permanent darkness. So how could a dinosaur possibly have coped with these long periods of darkness, where temperatures would’ve regularly dropped well below freezing? This is where its key distinguishing features come into play. Its large eyes would have allowed it to see well in the dim light, key for spotting what little edible plant matter could be found in the frozen ground. Its long flexible tail could potentially have been wrapped round itself when the animal rested in order to keep itself warm (rather like your pet cat does when it is taking a nap!). Another strategy to protect itself against the cold could have been taking shelter in burrows. Fossil burrows have been found at Dinosaur Cove and it has been suggested they could have been made by Leaellynasaura. Support for this theory comes from fossils in Montana of a close cousin, named Oryctodromeus. Fossilised remains have been found preserved in the burrows that they lived in. Also because of fossil evidence from ancestral relatives (such as Tianyulong) it has been suggested that Leaellynasaura was covered in feathers. Speculations range from simple velvety fuzz to a multi-layered fluffy coat according to different reconstructions. The feathered coat makes sense considering the cold climate, certainly allowing it a much greater degree of insulation than traditional reptilian scales.

It may not be the biggest, or possess giant claws, bone clubs or spines, but Leaellynasaura in its own way was just as remarkable a dinosaur as any that have ever existed, perfectly adapted to an environment that was previously thought to be impossible for a reptile to live in. Also, especially if we assume it did possess a thick fluffy coating of feathers with its big eyes and long tail, Leaellynasaura would have certainly been a contender for the cutest dinosaur to ever exist! If it were alive today dog grooming shows would have serious competition from Leaellynasaura grooming shows!

References/Further Reading

Article on Australian Dinosaurs (including Leaellynasaura) and Dinosaur Cove

Udurawane, Vasika, “Dinosaurs down under”, Earth Archives, 2016, eartharchives.org/articles/dinosaurs-down-under/

A 2017 study by Sharp et al. which put a Leaellynasaura fossil through a CT scanner

Sharp, Alana & Regalado Fernandez, Omar & Siu, Karen & Rich, Tom. (2017). Revealing the skeleton of the polar dinosaur Leaellynasaura amicagraphica using synchrotron computed tomography, Society of Vertebrate Paleontology (SVP) 77th Annual Meeting.

The Western Australian Museum’s article about Leaellynasaura, talking about its anatomy, size and growth.

“Leaellynasaura”, Western Australian Museum, 2014, museum.wa.gov.au/explore/dinosaur-discovery/leaellynasaura

Dakotaraptor: The Thief from Hell Creek

Dakotaraptor in all its feathered glory!
Image Credit: Emily Willoughby, https://commons.m.wikimedia.org/wiki/File:Dakotaraptor_wiki.jpg

If there was only one place and time that I could take someone new to the topic of dinosaurs, it would undoubtedly be Hell Creek, 65 million years ago. Here, in an environment of lush forests and temperatures similar to Spain today, lived a variety of instantly recognisable dinosaur icons. You could see a Triceratops lumbering through the woods, view a herd of Edmontosaurus browsing the nearby vegetation, hear two Pachycephalosaurus crashing their heads together and ensure to keep us a safe distance from the solid club tail of an Ankylosaurus. To cap it all off you would see the most famous dinosaur of them all, Tyrannosaurus Rex. In one area I could show someone a ceratopsian, a hadrosaur, a pachychephalosaur, an ankylosaur and a tyrannosaur all in one afternoon. Now, thanks to new fossils described only four years ago, you can add a large dromaeosaur (aka, “raptor”) to that list.

This animal has been given the name Dakotaraptor steini (“Stein’s Dakota Thief”), after the State of Dakota where Hell Creek is located and in honour of palaeontologist Walter Stein. It was discovered by a team led by Robert DaPalma, who described some partially articulated fossilised skeletons of a few individuals including arm and leg bones, some tail vertebrae and teeth. There was also a “wishbone” that was thought to belong to Dakotaraptor, however a study by Arbour et al in 2016 showed that this was actually a turtle bone (an honest mistake on the DePalma and his teams part!) These fossils showed that this dinosaur was no chicken! Measuring 5 and a half metres long and 1.8 metres tall it would have been almost exactly the same size as the famous Velociraptors from the film Jurassic Park. However for a large raptor Dakotaraptor was relatively lightweight, partly due to its vertebrae having air spaces within them. Combing this with legs built for long strides and Dakotaraptor would have been able to achieve top speeds of around 30-40 mph, that’s as fast as a greyhound! Just like the Jurassic Park raptors, Dakotaraptor would have been a lethal predator, hunting in packs to take down large herbivorous dinosaurs. To do this Dakotaraptor needed some serious weaponry, luckily that’s just what it had in the form of the raptors signature weapon; the killing claw on its feet. Dakotaraptor’s was especially big, measuring 9 and a half inches, with a serrated hook shaped end. It used to be thought that raptors used their claw in order to violently slash and disembowel prey. However it is now thought that the claws were mainly used to hold onto large struggling prey and to pin down smaller animals, rather like a modern bird of prey.

A illustration of Dakotaraptor showing the position of all the known bones (highlighted in white).
Image Credit: PaleoNeolitic, https://commons.m.wikimedia.org/wiki/File:Dakotaraptor_Skeleton_Reconstruction.jpg

The resemblance to birds doesn’t end there. Dakotaraptor, just like all other raptors, was completely covered in feathers (sorry if I’ve just ruined your childhood memories of scaly raptors!). In fact Dakotaraptor is the first large raptor to have direct evidence of feathers (previously it had been inferred that they had them based on smaller relatives possessing them). On its ulna (one of the arm bones) palaeontologists discovered a series of 15 regular notches running along the bone. These notches are called quill knobs and their purpose is to act as anchor points for long pennaceous feathers to attach to. As a result Dakotaraptor would have sported a small pair of wings! However these wings weren’t strong enough for flight (Dakotaraptor was already lethal enough without needing to fly!) Instead, through flapping and balancing motions it could have helped keep the raptor steady while running or holding on to prey. Wing feathers could also have been for display, with potentially bright colours being used to attract a mate or to show off to rivals (a trait common in modern birds). Feathers could have made the animal look bigger and more intimidating and could even be used to cover its young while nesting. With a full head and body of soft feathers, a feathery tail fan and small wings, you might have mistaken Dakotaraptor (and other raptors for that matter) for a giant grounded eagle or hawk from a distance.

Being discovered at Hell Creek also means that Dakotaraptor, just like Tyrannosaurus and Triceratops, was one of the last of the dinosaurs. It would have lived right up until the end of the Cretaceous period and would have been another victim of the asteroid strike on the Gulf of Mexico 65 million years ago. After the impact and resultant climate change the vegetation that its plant eating prey relied on disappeared. With its prey gone Dakotaraptor would disappear too, and with it the entire line of fast, remarkably bird like dinosaurs known as the dromaeosaurs would be no more.

Size comparison between Dakotaraptor and an adult human. With how close the human is he won’t be waving for long!
Image Credit: Matthew Martyniuk, https://commons.m.wikimedia.org/wiki/File:Dakota_raptor_scale_mmartyniuk.png

Now I’m going to end this blog with the question that I’m sure some people would be asking. Would Tyrannosaurus Rex and Dakotaraptor have clashed? Such confrontations would have certainly been possible as the two dinosaurs lived in the same place at the same time, and might have hunted similar prey at times. However fights may not actually have been that common. Dakotaraptor would have mostly targeted smaller and faster prey than T-Rex. As a result of this it would have occupied a different role (or “niche”) in the Hell Creek environment, that of a medium sized predator. This idea is called “niche partitioning” and we see it happen today on the African savannah, where cheetahs hunt fast gazelles while lions hunt the larger wildebeest, and so don’t compete with each other (except over a carcass). As a result Dakotaraptor might not have directly competed with Tyrannosaurus Rex for food. But for the sake of fun, what if they had come into conflict? Well a single Dakotaraptor would probably have fared against an adult T-Rex about as well as the Velociraptor at the end of Jurassic Park did! However a pack of Dakotaraptors against an adult, or an adolescent T-Rex would have been a different proposition. One could even envision a Dakotaraptor pack chasing a Tyrannosaurus off a kill in exactly the same way as a pack of Hyenas do to Lions on the African Savannah. So that fight between a T-Rex and a raptor at the end of Jurassic Park could have happened, just with a lot more feathers flying around!

UPDATE: A new study (Frederickson, Engel & Cifelli 2020), published in the journal Palaeonon the 3rd of May 2020, has cast doubt on the theory that raptors like Dakotaraptor lived and hunted in packs. The study examined the level of tooth carbon isotopes in juvenile and adult Deinonychus, a smaller and earlier relative of Dakotaraptor. What they found was the carbon isotope levels were rich in juveniles but depleted in adults. This indicates that they were eating different prey and this difference is consistent with animals like crocodiles who don’t live in packs. In pack hunting animals, such as Lions, both young and adult individuals eat the same food as they’re often sharing a kill between members of the group, so have the same or similar tooth carbon isotope level. In short, raptors like Dakotaraptor May have lived a more solitary life.

References/Further Reading

A National Geographic article, written by Ed Yong, on the use of the raptors killing claw

Yong, Ed, “Deinonychus and Velociraptor used their killing claws to pin prey, like eagles and hawks”, National Geographic, Dec 14, 2011, nationalgeographic.com/science/phenomena/2011/12/14/deinonychus-and-velociraptor-used-their-killing-claws-to-pin-prey-like-eagles-and-hawks/

The DePalma et. al. 2015 paper describing the first Dakotaraptor fossils

DePalma, Robert A., Burnham, David A., Martin, Larry D., et. al., The first giant raptor (Theropoda: Dromaeosauridae) from the Hell Creek Formation, Paleontological Institute, Paleontological Contributions;14, (2015), https://doi.org/10.17161/paleo.1808.18764

The Arbour et. al. 2016 paper that pointed out that one of the fossils was actually a turtle

Arbour VM, Zanno LE, Larson DW, Evans DC, Sues H. 2016. The furculae of the dromaeosaurid dinosaur Dakotaraptor steini are trionychid turtle entoplastra. PeerJ 4:e1691 https://doi.org/10.7717/peerj.1691

Another blog, by Brian Switek, talking about possible interactions between Dakotaraptor and T-Rex

Switek, Brian, “Did Dakotaraptor Really Face Off Against Tyrannosaurus?”, goodreads, Nov. 25, 2015, goodreads.com/author/show/3958757.Brian_Switek/blog?page=23

Frederickson, Engel & Cifelli 2020 study that used tooth carbon isotope data to indicate that raptors may not have been pack hunters (EDIT)

J.A. Frederickson et al, Ontogenetic dietary shifts in Deinonychus antirrhopus (Theropoda; Dromaeosauridae): Insights into the ecology and social behavior of raptorial dinosaurs through stable isotope analysis, Palaeogeography, Palaeoclimatology, Palaeoecology (2020). DOI: 10.1016/j.palaeo.2020.109780

Hatzegopteryx: The King of Hațeg Island

The Kings of the Island
Image Credit: Mark Witton, https://commons.m.wikimedia.org/wiki/File:Hatzegopteryx.png

A wildlife safari to the island of Hațeg was going to be perfect they said. Warm sunny beaches, unspoiled wilderness and herbivorous dinosaurs small enough to ride like ponies. What could possibly go wrong!

But now the tourists are running for their lives through the fields of ferns, not daring to stop as the top predators of the island follow closely behind. They had been warned that they were dangerous, but their guide had said that they would be fine, they wouldn’t get too close and he would use his gun if they did. Sadly the guide had been eaten about fifteen minutes ago. The tourists keep going, trying to get as far away from the rasping squawks as they can. One of them is picked up of the ground, disappearing out of sight. Another suffers the same fate. Suddenly the last one trips and rolls forward. Coughing and spluttering he turns around, and sees one of the beasts towering over him. It regards him with its beady eyes before leaning its large head down and grabbing his leg with its beak. The beast leans its head back and with one final gulp the tourist joins his friends. The island once again belongs to its king.

The movie executives look up from the script they’d just read. “Okay who sent this in?”, one asks. “I think it was the same guy who sent in the one about the giant killer centipede, Arthro-something?” the other replied. With a sigh the first executive tosses the script onto a large pile in the corner.

Who needs alien monsters when prehistory keeps giving us animals to make movies about! First there was the giant creepy-crawlies of the Carboniferous, now this!

Hatzegopteryx (meaning “Hațeg basin wing”) was a wonder of the Late Cretaceous. It was first discovered only 17 years ago in 2002, and described from fragmentary remains of skull, humerus and femur. Initially these fossils were thought to belong to a large carnivorous dinosaur. However further study showed that they belonged to a flying reptile – a Pterosaur. Pterosaurs were a group of reptiles that dominated the skies during the Mesozoic era, going extinct sixty five million years ago at the end of the Cretaceous period. They had wings consisting of thin complex structures that stretched from their lower bodies to the end of an elongated fourth finger. Hatzegopteryx in particular belonged to the sub group of pterosaurs known as the azhdarchids. The azhdarchids appeared in the Late Cretaceous and grew to gigantic proportions even by pterosaur standards. They were the largest flying animals to ever live. Hatzegopteryx was no exception, with a wingspan of up to twelve metres long. Despite its large size (and some palaeontologists claiming that they had evolved to be flightless) such a large animal was able to fly because it was surprisingly lightweight. Even the largest azhdarchid pterosaurs have been estimated to weigh only 550 pounds. This is due to a combination of weight saving hollow bones and soft tissue air sacs, which also provided an oxygen reserve for powered flight. In flight azhdarchids such as Hatzegopteryx would have wasted little energy flapping, instead soaring on rising air currents like a modern day vulture. This allowed them to cover great distances, up to 10,000 miles in some estimates. Like almost all pterosaurs Hatzegopteryx would also likely have had a body covering of soft down known as pycnofibres. This down, while feather-like, was different to the feathers of birds and used in insulation rather than for display or flight.

Hatzegopteryx humorous bones from above (A) and from the side (B)
Image Credit: Mark Witton & Michael Habib, http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0013982

However despite being able to fly Hatzegopteryx would not have done its hunting whilst airborne. Instead, and rather unusually for a pterosaur, it hunted on the ground. When grounded Hatzegopteryx stood at a height of around five metres, which is as tall as a modern day giraffe! From this high vantage point Hatzegopteryx could survey the landscape, looking for any small dinosaurs it could catch. Able to comfortably stride across the landscape using all four limbs, Hatzegopteryx would pick up and swallow whole any small animals it could find while using its sharp beak to kill any larger individuals. Such a hunting strategy is not too dissimilar to that employed by modern day storks and hornbills, except on a much larger scale. Hatzegopteryx managed this hunting style because of its huge skull. At three metres long and half a metre wide it was the longest skull of any land based animal. This was a powerful beaked weapon that was supported by a relatively short but hugely muscular neck. This short neck is a relatively new discovery and stems from a 2017 paper written by Palaeontologists Mark Witton and Darren Naish. This skull and neck is different to other azhdarchids, such as Quetzelcoatlus and Cryodrakon, which tended to have longer necks and thinner skulls.

A 3 metre long skull of Hatzegopteryx (Top) compared with the 1.5 metre long skulls of Spinosaurus (Bottom right) and Giganotosaurus (bottom left)
Image Credit: Wikimedia Commons, https://commons.m.wikimedia.org/wiki/File:Skulls_length_comparison_of_Hatzegopteryx,_Spinosaurus_and_Giganotosaurus.png. Based on images from Therrien & Henderson 2007 and Buffetaut, Grigorescu & Csiki 2002.

Hatzegopteryx was first discovered in Transylvania in Romania, in the same area that Bran Stokers Dracula lived (though I’m sure Hatzegopteryx would have eaten Dracula for lunch then eyed up Van Helsing as seconds!). 70 million years ago this area was an island, roughly the size of Ireland, known as Hațeg Island. Hațeg was a subtropical environment, consisting of broadleaf forests, open plains and a hot climate. If it were around today it would be heaving with tourists – Hatzegopteryx permitting. What makes the island uniquely interesting were the dinosaurs that lived there. Consisting of a mix of sauropods, hadrosaurs and small theropods, they were of a smaller size compared to their mainland counterparts. For example Magyarosaurus dacus, a species of titanosaur sauropod, had a maximum length of only six metres on Hațeg, compared to fifteen metres on mainland species. This is equivalent to finding an elephant the size of a donkey and is an example of “insular dwarfism”. This is when animals on an isolated island adapt to the limited resources by growing to smaller sizes. Hatzegopteryx on the other hand is an example of “island gigantism”, where in order to fill an empty ecological niche (in this case the role of “top predator” – there were no large carnivorous dinosaurs on Hațeg) an animal grows larger than usual. A modern day counterpart to Hațeg Island would be the Galapagos Islands, where we see similar diverged island evolutionary processes (e.g. the giant tortoise and numerous species of finches). Another example would be New Zealand, where in the absence of large mammals birds such as the Kiwi, the Moa and the Haast Eagle evolving to occupy the major ecological niches (the latter two only going extinct within the last 1000 years).

Hatzegopteryx would have been a marvel to witness flying. An extraordinary and complex achievement of natural aeronautical engineering, there has never been an animal quite like it. If Hatzegopteryx was alive today I’m sure the reptile/stork/giraffe hybrid would generate the same (if not more) fear as another famous blood sucking Transylvanian does.

EDIT: By a weird coincidence 3 days after this blog went up a new paper came out by (Solomon et. al. 2019) about the discovery of a new species from azhdarcid pterosaur from Transylvania! Known from fragments of beak and vertebrae and thought to represent a juvenile this new pterosaur has been named Albadraco tharmisensis. It has been estimated to have been only a little bit smaller than Hatzegopteryx and further illustrates the wide range of life that was present on Hațeg Island 70 million years ago!

References/Further Reading

Solomon et. al. 2019 paper on the new azhdarchid pterosaur Albadraco, which lived at the same place and time as Hatzegopteryx.

Solomon, A. A., et al. (2020). “A new species of large-sized pterosaur from the Maastrichtian of Transylvania (Romania).” Cretaceous Research 110: 104316.

A paper by Darren Naish and Mark Witton (Naish & Witton 2017) on Hatzegopteryx neck length and biomechanics

Naish D, Witton MP. 2017. Neck biomechanics indicate that giant Transylvanian azhdarchid pterosaurs were short-necked arch predators. PeerJ 5:e2908 https://doi.org/10.7717/peerj.2908

A paper, written by a team led by Michael Benton (Benton et. al. 2010), on the dwarf dinosaurs of Haţeg Island.

Benton, M. J., et al. (2010). “Dinosaurs and the island rule: The dwarfed dinosaurs from Haţeg Island.” Palaeogeography, Palaeoclimatology, Palaeoecology 293(3): 438-454.

An article, written by Elizabeth Martin-Silverstone and published on The Conversation website, on Azdarchid Pterosaur flight.

Martin-Silverstone, Elizabeth, “Pterosaurs should have been too big to fly – so how did they manage it?”, The Conversation, Jun. 30, 2016, theconversation.com/pterosaurs-should-have-been-too-big-to-fly-so-how-did-they-manage-it-60892

Another interesting paper, Yang et. al. 2018, on Pterosaur’s feather-like pycnofibres

Yang, Z., Jiang, B., McNamara, M.E. et al. Pterosaur integumentary structures with complex feather-like branching. Nat Ecol Evol 3, 24–30 (2019). https://doi.org/10.1038/s41559-018-0728-7

The Legend of the Sea Serpent Mosasaurus

Mosasaurus as it may have looked when it swam in Earth’s seas 70-65 million years ago.
Image Credit: Dmitry Bogdanov, https://commons.m.wikimedia.org/wiki/File:Mosasaurus_beaugei1DB.jpg

The idea of a large, serpentine like animal living in the depths of the ocean and battling heroes of legend has been a favourite tale of a whole host of myths and legends. Since early human history people seem to have been attracted to the idea of such an animal, quite unlike anything that lives today. Even in recent times this is a concept that has people enthralled. Just ask anybody who is convinced that there is a plesiosaur like animal living in Loch Ness. However while a large sea serpent probably doesn’t exist today (not counting real life sea snakes) there was a similar beast that ruled the seas of the Late Cretaceous period 70 million years ago. Its full scientific name, is Mosasaurus hoffmanni (Meaning “Hoffmanns Meuse Lizard”).

Mosasaurus was discovered back in 1764 near the town of Maastricht in the Netherlands. This was a time when the word “dinosaur” hadn’t been spoken yet, and proper scientific research on fossils was in its infancy. The fossil itself was a disarticulated skull, a cast of which is on display in the Sedgwick Museum in Cambridge. This fossil went through an eventful journey before it was first scientifically examined in the early 19th century, which includes being hidden from French occupation and being traded (allegedly) for 600 bottles of wine! Scientists of the time, including the famous French naturalist Georges Cuvier, correctly deduced that this animal was a reptile. Now “Meuse Lizard” may seems like a weird name to give an animal like this, but it was named after the Meuse River which runs through Northern Europe close to Maastricht.

This sea faring animal was very much the top predator of its day, reaching up to 15.2 metres long and weighing 15 tons. While there were other formidable hunters around (one example being Xiphactinus, a 5 metre long predatory fish known for swallowing prey whole!) there was no other marine predator that could rival it. Mosasaurus was an opportunistic hunter, eating almost anything that it could fit its powerful jaws around. This included a whole range of marine animals, from fish to squid, other marine reptiles and even smaller species of Mosasaurs! Mosasaurus was also quite different from other marine reptiles in that its lizard ancestors took to the water at a much later date than other marine reptiles such as Ichthyosaurs and Plesiosaurs. Also, unlike its lizard ancestors Mosasaurus gave birth to live young instead of laying eggs (just like modern day sea snakes). However Mosasaurus, along with the rest of its family, could not survive the asteroid that struck the earth 65 million years ago, dying out alongside the dinosaurs. They are survived by their closest living relatives; monitor lizards and snakes. Which funnily enough makes the sea serpent comparison even more fitting!

The fossilised head of Mosasaurus, showing its frightening battery of teeth!
Image Credit: Tim Evanson, https://www.flickr.com/photos/timevanson/9322551651

In the last couple of years Mosasaurus has been getting attention both in film, where it steals the show in the film Jurassic World, and in the world of paleontological research. This research has changed our understanding of how Mosasaurs both looked and behaved, with the following three studies being particularly insightful:

First. A study carried out by Johan Lindgreen, Hani Kaddumi and Michael Polycin in 2013 discovered a new anatomical feature in Mosasaurs. Previously it had been thought that they powered their long bodies through the water with a broad, straight tail, moving in a undulating manner like a modern day sea snake. However, after examining a fossil Mosasaur, named Prognathodon, from Jordan in Africa the palaeontologists noted that the outline of its skin had been fully preserved. This impression clearly showed a tail fluke like those of sharks or Ichthyosaurs, albeit with the upper fluke being smaller than the lower fluke. This tail, a product of convergent evolution, would have enabled mosasaurs to perform fast, powerful strokes to catch prey by surprise.

Second. A study in 2014, carried out by a team of palaeontologists based at Lund University in Sweden (which also included Lindgreen and Polycin, among others), gave us our first look at the colour of a mosasaur. This was an exciting find as evidence of colour is very rarely preserved in extinct animals and had never before been seen in a marine animal. The study looked at tiny blob like structures on the skin of an 85 million year old fossil mosasaur named Platecarpus tympaniticus. These had previously been thought to be bacteria. However as it turns out these blobs were actually melanosomes, the cells that produce skin colour. The structure of these preserved melanosomes showed that this mosasaur, and by extension other mosasaurs such as Mosasaurus, had what is known as “countershading”. Countershading is a colouration pattern that consists of a dark upper body and a light lower body (an example of this being the colouration of a modern day Killer Whale). This has a few advantages; it provides camouflage against the dark ocean depths (when looked at from above) and against the sunlight lit surface (when looked at from below). The dark upper surface also allows the mosasaur to absorb more heat from the sun when it surfaces for air and gives it protection from UV light when at the surface.

Third. A recent study conducted at the University of California, and only published in September 2019, looked in detail at how Mosasaurs swam. What they found was that Mosasaurs could perform a “breaststroke” like action with their front flippers. In conjunction with powerful beats of their tails, this would have allowed them to achieve great bursts of speed through the water. This is interesting because it was thought that marine animals swim using either their tails or their fins, but not both at the same time. As a result this swimming style is unlike any other known animal and makes mosasaurs even more remarkable.

And so, thanks to studies both old and new, we have a detailed picture of Mosasaurus, and its family, as one of the most unique sea faring animals ever. It further proves that the world of paleontological research is still capable of putting fresh spins on iconic animals of the past!

Mosasaurus enjoying a dinosaur dinner!
Image Credit: Jonagold2000, https://commons.m.wikimedia.org/wiki/File:Mosasaurus_hoffmanni_life.jpg

References/Further Reading

Lindgren, Kaddumi & Polcyn 2013 paper about Mosasaur tail flukes.

Lindgren, J., Kaddumi, H. & Polcyn, M. Soft tissue preservation in a fossil marine lizard with a bilobed tail fin. Nat Commun 4, 2423 (2013). https://doi.org/10.1038/ncomms3423

Lindgren et. al. 2014 paper about Mosasaur coloration. This study also discovered the colour of a 55 million year old turtle (which had the same colour as a modern day leatherback turtle) and a 200 million year old Ichthyosaur (which was a dark colour).

Lindgren, J., Sjövall, P., Carney, R. et al. Skin pigmentation provides evidence of convergent melanism in extinct marine reptiles. Nature 506, 484–488 (2014). https://doi.org/10.1038/nature12899

A paper, written by Kiersten Formoso and published in September 2019 (Formoso 2019), on new theories on Mosasaur swimming motions.

Formoso, Kiersten K., Reassessment of the Mosasaur pectoral girdle and its role in aquatic locomotion, Geological Society of America Abstracts with Programs. Vol. 51, No. 5, (2019), doi: 10.1130/abs/2019AM-333823

Further information, from the FossilEra website, about Mosasaur size, diversity, lifestyle and history of discovery

FossilEra “Mosasaurus & Mosasaurs”, FossilEra, fossilera.com/pages/about-mosasaurs

Get the all new Spinosaurus while stocks last!

The skeleton of an ancient river monster!
Image Credit: Mike Bowler, https://commons.m.wikimedia.org/wiki/File:Spinosaurus_swimming.jpg

Let me tell you a story. Three time travellers meet in a bar. They decide that they want to journey back to Mid Cretaceous North Africa, around 95 million years ago. They plan to have a dinosaur safari, just like the safaris that are conducted across the modern day Serengeti. However the area is dangerous as there are plenty of dangerous dinosaurs roaming around, some big enough to take out the jeep faster than the time travelling tourists can say “holy cow is that a dinosaur!” So they come up with a plan. Instead of going by jeep, they will use a river boat. “It’s perfect!” they say, “no dinosaur will be able to reach us as we are on the water and because it’s inland there’s no need to fear any sea faring marine reptiles”. After some time planning the time travellers undertake their boat journey. They marvel at the herds of the huge sauropod Paralititan and see an impressively large Carcharodontosaurus watching the herd hungrily. However as they are distracted by what they are seeing they don’t notice a large object moving in the river. Suddenly one of them hears the sound of rushing water and turns round to see a large sail poking out of the water like Jaws’ fin and heading right towards the boat. In five minutes, the time travellers will have seen their last dinosaur….

The unidentified river monster in this story is not a fish, nor a crocodile. It is instead the largest of all theropod dinosaurs: Spinosaurus aegyptiacus (meaning “Egyptian spine lizard”). The first Spinosaurus fossils were discovered in Egypt by German palaeontologist Ernst Stromer in 1912, however sadly these remains were destroyed during allied bombings raids on Munich during World War Two. Spinosaurus has gained more attention in recent years as new research has shown that this theropod had a lifestyle unlike any other dinosaur. The research suggests that Spinosaurus is the first known aquatic dinosaur.

There are certain anatomical features that support this interpretation. One area is the shape and design of the skull. The teeth were long and conical, well suited for gripping and holding on to slippery prey such as fish. The nostrils were placed high on its snout so it could hold it submerged in water while still being able to breath. It’s also thought that holes at the end of Spinosaurus’ snout contained pressure sensors, similar to those seen in modern crocodiles, which are used to detect disturbances in the water. The water based adaptations don’t stop there; one specimen of a Spinosaurus upper jaw has a barb embedded in it that belonged to a species of giant swordfish called Onchopristis. This suggests that Onchopristis was one of Spinosaurus‘ main sources of food. So taking all these adaptations together it suggests that Spinosaurus had a mostly fish based diet (however it is still possible that it ate meat as well).

An illustration of the head of Spinosaurus. Note the distinctive long, crocodile like jaws, conical teeth and small head crest.
Image Credit: Steveoc 86, https://commons.m.wikimedia.org/wiki/File:Spinosaurus_skull_steveoc.jpg

All these adaptations are well and good, however the biggest evidence for Spinosaurus‘ aquatic lifestyle was detailed in a paper released in 2014, written by a team of palaeontologists led by Spinosaurus expert Nizar Ibrahim. The paper examined and described a new 11.3 metre long specimen (that wasn’t fully grown, Spinosaurus could reach a maximum length of 15 metres) that is the most complete Spinosaurus skeleton ever found. Examination of the hind limb bones and pelvic girdle showed that they were much shorter than previously thought. These hind limbs were so short that Spinosaurus could not have walked on two legs for long periods of time as its legs couldn’t support its massive, front heavy bulk. This meant only one thing, Spinosaurus walked on all fours (at least occasionally). This is certainly very different to the bipedal, T-Rex killing beast that terrorised Alan Grant and the Kirbys in the 2001 film Jurassic Park 3. This new discovery also fits with the theory of a mostly aquatic based Spinosaurus. Short hind legs reduce drag when swimming and diving through water and is something that other aquatic and semi-aquatic animals, such as crocodiles and otters, exhibit today. These hind limbs were also solid and dense, helping with buoyancy control, and it has been speculated that feet would have been webbed to further aid in swimming. This means that Spinosaurus would have been comfortable and manoeuvrable in water, and a somewhat clumsy walker on land!

This reconstruction, which has commonly been dubbed “new Spinosaurus“, has caused quite a stir in the palaeontology community, Not everyone is on board with the idea and a few have even written articles and papers questioning the findings of the Ibrahim et al. 2014 paper. For example palaeontologist Scott Hartman questioned the length measurements of Spinosaurus’ hind limbs and Donald Hendersons 2018 paper questioned its buoyancy. However both these counter papers have their own issues; for example the Henderson paper based their buoyancy calculations on bone density data from other theropods and birds, except Spinosaurs have been shown to have proportionately thicker bones than these animals. The debate is still ongoing to this day, and so it is still not known for certain whether Spinosaurus truly was a quadruped or a biped.

So let us rejoice in the quadrupedal walking, gracefully swimming, humongously sized, sail-backed fish eater that Spinosaurus has become! Proof that during their 170 million year reign there were few habitats that the dinosaurs couldn’t reach.

UPDATE: Spinosaurus reconstructions continue to change with every new paper! A new study was published on the 29th April 2020 in the journal nature. Written by a team led by Nizar Ibrahim, has revealed that Spinosaurus had unusually tall neural spines and elongated chevrons on its tail vertebrae. These special vertebrae supported a flexible, paddle-like tail and it’s theorised that Spinosaurus used it to swim through the water! The image below illustrates what most palaeontologists now think Spinosaurus aegypticus looked like.

The most up to date (as of 29th April 2020) look of the river monster that our time travelling tourists had the misfortune of encountering!
Image Credit: Gustavo Monroy-Becerril, https://en.m.wikipedia.org/wiki/File:Spinosaurus_aegyptiacus_underwater.png

EDIT: One key piece of evidence, that I missed when writing this blog (my apologies!), from the Donald Henderson 2018 paper is that Spinosaurus’ centre of mass was located closer to its hips than to its torso. This is further evidence that Spinosaurus was a biped, walking on its short stubby legs (almost like a duck!). At the time of writing this Nizar Ibrahim has yet to publish his latest research on Spinosaurus so the two legged/four legged debate rages on. But currently the common consensus, at time of writing, is that Spinosaurus was a biped.

References/Further Reading

Ibrahim et al. 2014 paper, published in Nature, describing “New Spinosaurus

Ibrahim, N., et al. (2014). “Semiaquatic adaptations in a giant predatory dinosaur.” Science 345(6204): 1613-1616.

Henderson et. al. 2018 paper countering the Ibrahim et. al. 2014 paper

Henderson DM. 2018. A buoyancy, balance and stability challenge to the hypothesis of a semi-aquatic Spinosaurus Stromer, 1915 (Dinosauria: Theropoda) PeerJ 6:e5409 https://doi.org/10.7717/peerj.5409

Nizar Ibrahim’s response to Scott Hartman, published on Scott Hartman’s Skeletal Drawing.com.

Ibrahim et. al., “Aquatic Spinosaurus – The authors respond”, Scott Hartman’s Skeletal Drawing.com, Sept. 18, 2014, skeletaldrawing.com/home/aquatic-spinosaurus-the-authors-responsd9182014

An article in Smithsonian Magazine on the history of Spinosaurus research

Smithsonianmag.com, “Cracking the Code of Spinosaurus”, Smithsonian Magazine, Apr. 19, 2017, smithsonianmag.com/sponsored/spinosaurus-lost-dinosaur-paleontology-new-discovery-great-courses-plus-180962953/

New Ibrahim et. al. 2020 paper on the structure of Spinosaurus’ tail (USED FOR UPDATE)

Ibrahim, N., Maganuco, S., Dal Sasso, C. et al. Tail-propelled aquatic locomotion in a theropod dinosaur. Nature (2020). https://doi.org/10.1038/s41586-020-2190-3

Deinocheirus: The tale of the horrible hands

When I was a young boy who was madly into palaeontology and had significantly less adult responsibilities, I remember walking through the ever popular dinosaur exhibition in the Natural History Museum in London. Among the many displays, which ranged from models of dinosaur nests to the big skeleton of the Triceratops, there was one that always stood out to me. It was a pair of huge arms, complete with hands tipped with large claws. Unlike the proportionately tiny arms of Tyrannosaurus Rex, (I say proportionately as T-Rex arms were still as long as a humans) or the backwards facing stump like arms of Carnotaurus these arms were long with highly developed “hands”, displayed in such a way that it seemed like they could either give you a large hug or grab you and carry you away into the night. These arms, discovered in 1965, belonged to a dinosaur known as Deinocheirus mirificus; meaning “terrible hand which is unusual”. Quite a fitting description for a giant pair of arms! This beast lived in Mongolia 70 million years ago during the Late Cretaceous. At the time I first saw this fossil palaeontologists still didn’t really know what kind of dinosaur it was as no other fossils had been found except for the arms. It was a tricky task, how can you build up the image of an animal from just its arms. Imagine trying to construct what a human looked like, how we behaved, what we ate and what our social lives were like from just our arms. From this incredible looking fossil palaeontologists were able to deduce that it was a species of theropod dinosaur, but apart from that it was only guesswork.

That is, until new fossilised material was discovered in 2009 by a team from South Korea’s Institute of Geoscience and Mineral Resources in Kigam, lead by a palaeontologist named Yuong-Nam Lee. These were not only more giant arms, but also two nearly complete skeletons that finally solved the almost 50 year mystery.

It was much weirder than anything my younger self could have imagined. For starters, it was not a vicious giant carnivore like other large theropods such as Giganotosaurus. Instead it was an omnivore, using its duck-like beak to eat vegetation with a helping of small fish on the side. Deinocheirus was a slow, lumbering giant stretching to eleven metres in length, and weighing up to 6 tonnes. To add to the weirdness, it also possessed back spines that may have formed part of a hump like structure on its back, and it may also have even been covered in feathers. The end of its tail bones were fused together into a pygostyle. This same structure is seen today in modern birds and is used to support long tail feathers, so it’s possible that Deinocheirus also had a feathery tail fan! The large arms were probably used to gather out of reach plants closer to its mouth, rather like a giant panda grabbing bamboo, or as a defence against predators, such as the tyrannosaurid Tarbosaurus whose bite marks are seen on the bones. The fossils did confirm that it was a theropod dinosaur and part of the ornithomimids, a group of dinosaurs which also included Gallimimus of Late Cretaceous North America. However Deinocheirus is very bizarre even when compared to other ornithomimids. Other species were smaller, with slender bodies and legs built for speed (not too dissimilar in lifestyle to the modern day Ostrich).

So as it turns out, Deinocheirus is not the terrifying monster that I thought it was when I saw those fossil arms all those years ago. Instead, in looks and lifestyle, it seems like the result of a group of mad scientists genetically splicing a T-Rex, a duck and an ostrich together to see what they get. However this new depiction, in my view, is just as fascinating and awe inspiring, and shows how diverse dinosaurs really were.

The Horrible hands, along with the rest of Deinocheirus!
Image Credit: Johnson Mortimer, https://commons.m.wikimedia.org/wiki/File:Deinocheirus_by_johnson_mortimer-d9npnef.jpg

References/Further Reading

Lee et al 2014 paper, published in the journal Nature, describing new fossil material of Deinocheirus

Lee, Y., Barsbold, R., Currie, P. et al. Resolving the long-standing enigmas of a giant ornithomimosaur Deinocheirus mirificusNature 515, 257–260 (2014). https://doi.org/10.1038/nature13874

An article on National Geographic, written by Ed Yong, on the 2014 study of Deinocheirus that revealed its true form

Yong, Ed “Deinocheirus Exposed: Meet The Body Behind the Terrible Hand”, National Geographic, Oct. 22, 2014, nationalgeographic.com/science/phenomena/2014/10/22/deinocheirus-exposed-meet-the-body-behind-the-terrible-hand/

An article on NewScientist, written by Jeff Hecht, about the re-discovery of a fossil Deinocheirus‘ head and feet, which had been previously smuggled out of Mongolia!

Hecht, Jeff. “Stolen dinosaur head reveals weird hybrid species” NewScientist, May. 12, 2014, newscientist.com/article/dn25551-stolen-dinosaur-head-reveals-weird-hybrid-species/