Dinosaur

**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

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 mirificus. Nature 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/

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Deinocheirus: The tale of the horrible hands