“A Diplodocus? Dippy the Diplodocus!”

A reconstruction of Diplodocus carnegii, the species that Dippy belong to!
Image Credit: Fred Wierum, https://commons.wikimedia.org/wiki/File:Diplodocus_carnegii.jpg

From February 2018 to October 2021, a giant dinosaur has been travelling the UK. It’s had a long journey! Starting in Dorset, its migrated to Birmingham, then across the Irish sea to Belfast, back across to Glasgow, then south to Newcastle-upon Tyne, on to Cardiff, then to Rochdale and finally to Norwich. After a bit of a delay due to a certain virus millions of times smaller than it, the dinosaur finally reached Norwich in May 2021 and stayed there until the end of October. As Norwich is close to me this humble writer went to visit this dinosaur back in August 2021. I had not seen it since roughly the early 2010s, back when it was a star of one of the most famous museums in the world, the Natural History Museum in London. Since it was already well known, and since dinosaurs are always popular, hundreds of people had gathered to see it. The queue at its temporary home of Norwich Cathedral stretched from the entranceway of the southwest doorway all the way back through the cloisters and snaked its way past the front entrance of the cathedral. It took at least 20 minutes, but finally I reached the front of the line and entered the 900 year old cathedral nave that was big enough to house it! As I entered the huge, vaulted space, Dippy the dinosaur came into view. Dippy predates Norwich Cathedral itself by 153 million years and walked the land that would become the United States. But what was Dippy like? And how did this giant make its way across the Atlantic Ocean to Britain?

The original fossil of Dippy was unearthed in 1899 by railroad workers in Wyoming in the United States. After being fully excavated was put up on display in the Carnegie Museum, Chicago, where it still stands today. Now you might think “hang on, isn’t Dippy in the UK? Not the US!” Well, the UK skeleton we know, and love is not the same as the original fossil that’s at the Carnegie. Instead, it is one of 10 casts (or copies) of those Wyoming bones, (with other casts being present in museums in Paris, Berlin and more). The “Dippy” cast was made and sent to the UK on the order of none other than King Edward VII, who had been shown a drawing of the original skeleton by the owner of the Carnegie Museum, Andrew Carnegie, A Scottish-American Millionaire Philanthropist and Industrialist. Edward VII believed that it would make a fine addition for the Natural History Museum in London. It’s safe to say that he was right, as it has wowed millions upon millions of visitors for 111 years. Originally, Dippy was placed in the museum’s reptile gallery when it was unveiled in 1905. But in 1979 it was moved to its more recognisable position in the centre of Hintze Hall, where it greeted visitors as they entered the museum! In 2017 Dippy was dismantled to be given a deserved rest, being replaced by a hanging skeleton of an even larger animal, a Blue Whale! (Which has affectionately been named “Hope”).

Dippy itself! Standing proudly in Norwich Cathedral!
Image Credit: My own (low quality) photo that I took during my visit.

So now that we know how Dippy came to the UK, the next question is what exactly is Dippy? Well, if you were to guess that it was a big dinosaur then you would be correct! More specifically Dippy is a member of the species Diplodocus carnegii, named after Andrew Carnegie himself. Diplodocus means “Double Beam” and it stems from two strange rows of bones on the underside of its tail that helped to support it and promote flexibility. Diplodocus carnegii is not the only Diplodocus species known to science, there are in fact four! (The others being Diplodocus longus, Diplodocus lacustris and Diplodocus hallorum). First discovered in 1878 by the American fossil hunter Othniel Charles Marsh, Diplodocus were long necked, long tailed, heavily built, four-legged plant eaters that belonged to the group of dinosaurs known as the Sauropods. The first Sauropods appeared in the Early Jurassic period (a period lasting from 201-174 million years ago, exactly where Sauropods appeared in this time is still debated), and the group would last up until the very end of the Cretaceous period (66 million years ago). The ancestors of sauropods were small, upright walking, relatively lightweight generalists, a far cry from the giants that would evolve later! Later, multiple sauropod species, including Diplodocus itself, would occupy the large herbivore niche across the world, from the USA, to Argentina, to China and to Australia. The Jurassic was one of the best times for the Sauropods, with many of the most famous species originating in this period. Diplodocus fossils, alongside other famous sauropods such as Brontosaurus, Brachiosaurus and Apatosaurus, are all found in a Late Jurassic rock formation in the United States known as the Morrison Formation. This formation is HUGE! Geographically it stretches across the states of Arizona, Utah, Colorado, Wyoming, Montana and New Mexico, while chronologically it contains rock sequences and fossils dating to 155-150 million years ago. As well as Sauropods, the Morrison has preserved many other famous dinosaur species such as Stegosaurus, Allosaurus, Ceratosaurus, Dryosaurus, an early Ankylosaur known as Mymoorapelta and even an early Tyrannosaur called Stokesosaurus, as well as a collection of insects, fish, amphibians, early mammals, other reptiles (e.g. lizards, crocodilians) and flying reptiles known as Pterosaurs. The environment that Dippy and all these other spectacular dinosaurs lived in was warm, seasonal and semi-arid, that progressed to a wetter climate with floodplains and rivers, varying over the thousands to millions of years. Herbaceous (i.e., non-woody plants) were prevalent, with sporadic areas of woodland. This means that Dippy’s world would have had an almost “Savannah” like feel to it (except without any grasslands), with plentiful resources for all the giant dinosaurs. Sauropods are iconic dinosaurs because of their often absurdly huge sizes. They were so big that even a “small” sauropod would usually still be bigger than an Elephant!

Sometimes when you see your old house, city, or a treasured object again after a substantial number of years, it can seem smaller than you remember. Well, this is not what I felt when I saw Dippy again! On the contrary it seemed even bigger! Not only that but now I know more about Paleontology I can appreciate just how unusual Diplodocus is when compared with other sauropod dinosaurs. Here is what I mean.

First off, Dippy’s head is small, long and slender compared to the rest of its body, and to other sauropod skulls. Furthermore, this head contains a set of peg-like teeth which jut out slightly at the front, giving it an almost “goofy” look. This skull allowed Diplodocus to grab and strip off (or bite off) the leaves of low and medium growing plants before swallowing them whole. To sustain a Diplodocus carnegii that grew to lengths of roughly 25 metres (and up to 33 metres in Diplodocus hallorum!) and weighed roughly 11-15 tons (or somewhere between 25-50 tons in D.Hallorum), a Diplodocus would’ve needed to spend a lot of time eating. Luckily this “grab and pull” method is efficient, and by swinging their long necks around from side to side they could cover a wide area without needing to waste energy moving around. Furthermore, Diplodocus could lower their necks to access low growing plants, and even (briefly) rear up on their hind legs to access plants that would be out of reach otherwise. This skull and teeth did give Diplodocus a relatively specialized diet, limited to mostly soft leaves, but it meant that it could avoid direct competition with the other huge sauropods that it lived with. These other sauropods ate different plants that grew to different heights. For example, Camarasaurus’ boxy robust skull meant that it could have had a more generalized diet involving tougher woody stems. Furthermore, the orientation and reach of different sauropod necks meant they could access different foods. For example, while Diplodocus had a long, gently S-shaped neck and head that was held at a roughly 60 degree angle to the ground, a Sauropod like Brachiosaurus had a neck held more vertically like a giraffe, which allowed it to reach the leaves of the tallest trees. These differences in diet and head/neck anatomy allowed multiple different species of large 15-30 metre Sauropods to establish functioning populations in the same area at the same time. This is like having at least 5 different populations of animals all at least double the size of an African Elephant crammed into an area the size of Western Europe without the ecosystem collapsing!

File:Diplodocus species size comparison.svg
A size comparison between two Diplodocus species (D.carnegii & D.hallorum) and a human. Fun fact, Diplodocus hallorum wasn’t always considered a Diplodocus! It was originally called “Seismosaurus“, meaning “Earth Shaker Lizard”.
Image Credit: KoprX, https://commons.wikimedia.org/wiki/File:Diplodocus_species_size_comparison.svg

Secondly, Dippy had a relatively thin tail, with vertebrae that start off thick at the body end and thinning until they became smaller than your hand. This, along with the “Double Beam” bones mentioned earlier, made its tail strong, but mobile and whip like, very different to the thick and sluggish tails dinosaurs traditionally dragged along after themselves in classic illustrations and movies. Such a tail could’ve had multiple uses. It would’ve counterbalanced Diplodocus’ long neck and potentially been used for communication between other members of its herd (via a recognizable sequence of swings and tail movements). It could’ve also been used as a defense weapon, cracked like a whip or swung into any predators that wouldn’t have been deterred by Diplodocus’ sheer size or strength in numbers. Diplodocus would’ve needed this protection (along with the single row of small spines along it’s back and tail), as the lands of the Morrison Formation was also home to a collection of fearsome threats. Large predators such as the previously named Ceratosaurus (7 metres) and Allosaurus (9 metres), as well as Torvosaurus (10 metres)and Saurophaganax (11.5 metres) would’ve targeted sub-adult, sick or wounded Diplodocus. Also, smaller carnivores such as Stokesosaurus and Ornitholestes would’ve tried to take unwary hatchlings and exposed eggs. Life was tough for a young Diplodocus, but fortunately they didn’t stay small and vulnerable for long. It’s been estimated that, from hatchlings no more than a metre long (that hatched from eggs no bigger than footballs), Diplodocus attained lengths of roughly 3 metres by age 1, 9 metres by age 6, 19 metres by age 12 and the full 25 metres by the age of 20 (though rate of growth and final size attained could vary between different individuals). Just like with humans, Diplodocus kids grew fast and had a growth spurt as teenagers! What fueled this growth was consuming vast quantities of food. It has been found that Diplodocus youngsters had a more generalist diet (i.e., browsing on tree saplings and low growing plants), before transitioning to the more specialized adult diet. This meant they could find food more readily and keep up their fast growth.

All in all, Dippy’s time in the UK has been an unqualified success. The “Dippy on Tour” event alone has been seen by over 2 million people across the country, and the accompanying displays have helped educate people not only about the distant past but also about the current challenges faced by the world today. Not only does Dippy help tell the story of Diplodocus, how it lived, how it ate and the world it inhabited, but it also provides more evidence for why dinosaurs were such successful, remarkable and (yes I’m going to say it!) cool animals!

Further Reading

An article piece on the Natural History Museum website, written by Matthew Prosser, on the history of Dippy

Prosser, Matthew, “Dippy: this is your life”, Natural History Museum, 1st January, 2016, www.nhm.ac.uk, https://www.nhm.ac.uk/discover/diplodocus-this-is-your-life.html?gclid=Cj0KCQjws4aKBhDPARIsAIWH0JVsPEwiVHhKSzP_dK7BI-X6s9do5Sklu-ScuPBslgKvrzLzweH0ze8aArY6EALw_wcB

Young et. al. 2012 paper that analyzed the biomechanics of a Diplodocus skull to help give clues into how it ate.

Young, M.T., Rayfield, E.J., Holliday, C.M. et al. Cranial biomechanics of Diplodocus (Dinosauria, Sauropoda): testing hypotheses of feeding behaviour in an extinct megaherbivore. Naturwissenschaften 99, 637–643 (2012). https://doi.org/10.1007/s00114-012-0944-y

Fiorillo 1998 paper that looked at the dental microwear (i.e. the tiny scratches made on an animals teeth by its food, different wear patterns are made by different foods) on the teeth of Diplodocus and another sauropod named Camarasaurus, to figure out how they could co-exist in the same environment.

Anthony R. Fiorillo (1998) Dental micro wear patterns of the sauropod dinosaurs camarasaurus and diplodocus: Evidence for resource partitioning in the late Jurassic of North America, Historical Biology, 13:1, 1-16, DOI: 10.1080/08912969809386568

Dunagan & Turner 2004 paper that studied the depositional environment and paleoclimate of the Morrison Formation.

Dunagan, Stan, Turner, Christine, 2004, Regional paleohydrologic and paleoclimatic settings of wetland/lacustrine depositional systems in the Morrison Formation (Upper Jurassic), Western Interior, USA, Sedimentary Geology, VL 167, 10.1016/j.sedgeo.2004.01.007

Parrish, Peterson & Turner 2004 paper on the plant life and climate of the Morrison Formation.

Judith Totman Parrish, Fred Peterson, Christine E Turner, Jurassic “savannah”—plant taphonomy and climate of the Morrison Formation (Upper Jurassic, Western USA), Sedimentary Geology, Volume 167, Issues 3–4, 2004, Pages 137-162, ISSN 0037-0738, https://doi.org/10.1016/j.sedgeo.2004.01.004.

Woodruff et. al. 2018 paper that details the finding of a juvenile Diplodocus, and what it can tell us about its lifestyle and growth.

Woodruff, D.C., Carr, T.D., Storrs, G.W. et al. The Smallest Diplodocid Skull Reveals Cranial Ontogeny and Growth-Related Dietary Changes in the Largest Dinosaurs. Sci Rep 8, 14341 (2018). https://doi.org/10.1038/s41598-018-32620-x

• A blog article about baby sauropods, the differences between youngsters and adults, and their growth rates

Mike, “Why does a Baby Diplodocus have a Short Neck?”, Everything Dinosaur, December 12th, 2007, www.blog.everythingdinosaur.co.uk, https://blog.everythingdinosaur.co.uk/blog/_archives/2007/12/12/3405222.html

Information about the “Dippy on Tour” event, which ran from February 2018 to October 2021 and included places from across the UK.

Natural History Museum, “Dippy on Tour: A Natural History Adventure”, Natural History Museum, www.nhm.ac.uk, https://www.nhm.ac.uk/take-part/dippy-on-tour.html

• A blog article by Darren Naish, from 2009, on the biggest sauropods ever.

Naish, Darren, “Biggest… sauropod…. ever (part 1)”, scienceblogs, December 28th, 2009, https://scienceblogs.com/tetrapodzoology/2009/12/28/biggest-sauropod-ever-part-i

Stegosaurus: A Jurassic Icon

Sophie the Stegosaurus. On display at the Natural History Museum in London, England
Image Credit: Aya Reyad, https://commons.m.wikimedia.org/wiki/File:%D9%85%D8%AA%D8%AD%D9%81_%D8%A7%D9%84%D8%AA%D8%A7%D8%B1%D9%8A%D8%AE_%D8%A7%D9%84%D8%B7%D8%A8%D9%8A%D8%B9%D9%8A_8.jpg

In late 2014 the Natural History Museum revealed a new dinosaur display. It is situated almost immediately after you go through the east entrance, and is different from most fossils in that she has her own identity. Her name is Sophie, and she stands in front of the giant globe that marks the entrance to the Earth Hall as if guarding it. While she is small for her genus she is nevertheless an imposing sight; larger than any living elephant, two rows of plates lining her back and a spiked tail that she raises in defence. Her original home was the coniferous forests and floodplains that would later become the Western United States, and she walked the land 150 million years before humans. She is a special dinosaur, one that is instantly recognisable the world over by dinosaur lovers and casual observers alike. She is power, she is serenity, she is a Stegosaurus.

The first fossils of Stegosaurus (“roofed lizard”) were discovered in the state of Colorado, USA by Marshall Parker Felch in 1876. Felch was a veteran of the American Civil War and was a fossil hunter working with the palaeontologist Othneil Charles Marsh, who subsequently described and named this as a new dinosaur in 1877. The fossils were unearthed from what is known as the Morrison Formation; a 1 million square kilometre Late Jurassic rock sequence that stretches across a large area of the western USA including Arizona, Utah and Wyoming. The very first reconstructions of Stegosaurus was based on the initial assumption that it was an extinct turtle! This resulted in a wildly different animal to what we think today. In this initial reconstruction it reared on two legs, its spines were positioned on its back, its plates were laid flat on its back like roof tiles (hence “roofed lizard”) and it had two brains. That’s right those Victorian palaeontologists though Stegosaurus had TWO brains! A small, walnut sized brain in its head, and a “second brain” located in its hips. The thinking was that its main brain was so small compared to its body size that it needed a second one to help control its hind legs and tail. We know of course that it didn’t really have two brains. The “second brain” is thought to be a body cavity containing glycogen stores to help provide energy, in the form of glucose, to its muscles.

Since those early days many Stegosaurus fossils have been unearthed with Stegosaurus stenops, the species that Sophie belongs to, being the most common (in fact Sophie is the most complete Stegosaurus skeleton ever found). This has allowed palaeontologists to construct a more detailed picture of what this animal was like. It was a relatively slow moving, four legged animal belonging to its own group of ornithischian dinosaurs known as the Stegosaurs. Stegosaurus is the largest and most iconic member of the group, but Stegosaurs have been discovered across the world; such as Kentrosaurus from Africa, Tuojiangosaurus from Asia and Dacentrurus from Europe. Stegosaurus and its relatives were herbivores, using peg-like teeth to strip leaves off low growing ferns, mosses and shrubs. To help digest this, Stegosaurus would intentionally swallowed small stones (called gastroliths) that sat in its stomach and helped to grind up incoming plant matter. This diet may not seem very exciting, but consuming vast quantities of these simple shrubs allowed Stegosaurus to grow to a huge size; up to a maximum of 9 metres long and weighing 7 tons in the largest species (Stegosaurus armatus).

Size comparison between a human and two Stegosaurus species: S.ungulatus and S.stenops (the species Sophie belongs to)
Image Credit: KoprX, https://commons.m.wikimedia.org/wiki/File:Stegosaurus_size_comparison.svg

Stegosaurus is characterised by two eye-catching features. The first is the two rows of alternating pentagon shaped plates that stretch along its back from its neck to near the end of its tail. These plates were covered in a sheath of a horn like material called keratin, the same material that makes up fingernails, horns and antlers. Currently the best explanation for what these huge, lavish structures were used for is that they were multi-functional. The main use is in display and signalling to others. Whether males trying to attract a mate, Stegosaurus’ sizing each other up, ward off predators or to simply recognise each other these plates position on the body and their size would have made them very effective “billboards”. As a bit of fun speculation I wonder if these plates could have been brightly coloured, especially since it’s thought that the plates might have had an outer covering of thin skin. Unique variations in plate colours between different individuals would have acted like a fingerprint, allowing for identification and signalling. Another idea is that Stegosaurus used its plates to help regulate its body temperature. To do this Stegosaurus would have pumped blood into the plates, allowing the heat to be radiated outwards or to be taken in. This was a popular theory for a long time and while the size and positioning of the plates would have allowed them to passively radiate heat, and there are some channels within the plates that could have aided with this, the latest thinking is that the plates weren’t especially adapted for heat radiation or absorption.

The other defining feature of Stegosaurus was the two pairs of long spines that jutted out sideways from the end of its tail. This formed a structure that is referred to as a “Thagomizer”. This term is unique as it originated from a cartoon in the comic “The Far Side”, which had a caveman name the spiny tail after the fictional “late Thag Simmons”. The name has stuck since with palaeontologists accepting it as a valid scientific term. The thagomizer was a deadly weapon that Stegosaurus used by positioning itself sideways or with its tail facing its attacker, giving it room to swing and forming an impenetrable barrier to protect the more vulnerable front end. A thagomizer would have certainly been required as Stegosaurus was prey for the large predators stalking the area at the time. Large theropod dinosaurs such as Torvosaurus and Saurophagonax would have been among these, but by far the most notorious was Allosaurus. Fossil evidence of conflicts between Stegosaurus and Allosaurus have been found frequently, ranging from a damaged piece of Stegosaurus plate to large holes in Allosaurus bones caused by a Stegosaurus thagomizer (including one fossil where a thagomizer went straight through an Allosaurus pelvis, hitting a place where the sun doesn’t shine!). It seems that the two dinosaurs clashed frequently, sharing a rivalry similar to the one between T-Rex and Triceratops 90 million years later. Thagomizers may not have been Stegosaurus’ only method of defence. One theory is that Stegosaurus might have lived in small groups, with the numbers giving mutual protection. Furthermore it’s been speculated that Stegosaurus might also have formed mixed herds (like those seen between Wildebeest, Zebra and Ostrich’s on the African Savannah) with other plant eating dinosaurs such as the smaller Camptosaurus. This arrangement would have provided mutual benefits; Camptosaurus’ keen eye sight would have allowed it to act as a scout, while the Stegosaurus would have been the heavily armoured knights.

A life like model of Stegosaurus
Image Credit: DinoTeam, https://commons.m.wikimedia.org/wiki/File:Stegosaurus_02_DinoPark_Ko%C5%A1ice.jpg

For me personally Stegosaurus has held a fond place in my heart for a long time. It was my favourite dinosaur when I was young, so much so that I still have a toy one amongst my collection. I think I was fond of it it so much because not only did it have an eye catching appearance, quite unlike any animal alive today, but also because I saw it almost like a superhero. Normally it would peacefully munch on ferns and go about its business. But if it or its herd were threatened it wouldn’t hesitate to swing into action, lashing its spiked tail at any predator brave enough to take it on. While many prehistoric animals have left a mark on me over the years, none have done so quite like Stegosaurus, and for that I will always love it.

References/Further Reading

A paper (Carpenter et.al. 2005) on the predator-prey relationship between Allosaurus and Stegosaurus

Carpenter, Kenneth & Sanders, Frank & Mewhinney, Lorrie & Wood, Lowell. (2005). Evidence for Predator- Prey Relationships Examples for Allosaurus and Stegosaurus, The Carnivorous Dinosaurs, Chapter: 17, 325-350

A paper (Farlow, Hayashi & Tattersall 2010) reviewing the possible heat regulatory properties of Stegosaurus plates, using comparisons with Alligator osteoderms

Farlow, J.O., Hayashi, S. & Tattersall, G.J. Internal vascularity of the dermal plates of Stegosaurus (Ornithischia, Thyreophora). Swiss J Geosci 103, 173–185 (2010). https://doi.org/10.1007/s00015-010-0021-5

A blog article, published on Scientific American (originally on Tetrapod Zoology), by renowned palaeontologist Darren Naish on Stegosaurus plates and their research history

Naish, Darren, “The Stegosaurus Plate Controversy”, Scientific American, Jul. 11, 2016, blogs.scientificamerican.com/tetrapod-zoology/the-stegosaurus-plate-controversy/

An article by The Evolution Institute on the geology and fossils of the Morrison Formation

Marano, Michael, “Utah’s Morrison Formation: A Fossil Treasure Chest”, The Evolution Institute, Dec. 13, 2012, evolution-institute.org/utahs-morrison-formation-a-fossil-treasure-chest/

A New Scientist article on the origin of the word “thagomizer”

“The word: Thagomizer”, New Scientist, Jul. 5, 2006, newscientist.com/article/mg19125592-200-the-word-thagomizer/?ignored=irrelevant

A National Geographic article on the history of Stegosaurus reconstructions

Laelaps, “Out With the Old Stegosaurus”. National Geographic, Apr 29, 2013, nationalgeographic.com/science/phenomena/2013/04/29/out-with-the-old-stegosaurus/