Akmonistion: The Bearsden Shark

“Through shoal and shining flock and froth and freath and freaky frisky flashers, like a liner, The Bearsden shark coasts casually, kinglily, killingly casual, casing the scales, lazily pacing and chasing, lord of the place, of the plaice, lordly diner.”

The Bearsden Shark, Edwin Morgan.

Glasgow was a very different place 330 million years ago. What is now the largest city in Scotland, covered in sandstone buildings frequently splattered by rain, was once a warm shallow sea teeming with marine life. This ranged from molluscs, corals and fish to now extinct creatures such as straight coned Belemnites (ancient relatives of squids) and Sea Scorpions (which could grow bigger than a human!). Just like in today seas, sharks were a key part of this ancient ecosystem. At this point in their history, sharks and their close relatives were still in their early evolutionary days and, just like any teenagers, were going through “a phase”. They were experimenting with different body types and features not found in modern sharks. One of the weirdest shark-like creatures from this time was unearthed in the Bearsden area of Glasgow in 1982 by a local fossil collector named Stan Wood. This shark is known scientifically as Akmonistion zangerli (meaning “Zangerles anvil sail”) but it is more commonly referred to as “The Bearsden Shark”.

The 1982 Bearsden Shark fossil was quite an astonishing find. The cartilaginous fishes (a group that contains Sharks, Rays and Chimera fish), despite having existed on Planet Earth for over 400 million years, actually have a poor fossil record. This is because their skeletons are almost entirely made up of cartilage instead of bone. Cartilage is relatively soft and doesn’t fossilise well at all. So as a result an ancient shark’s body is almost always lost to time. The only exception is their teeth which due to being hard and resilient, and the sharks shedding and replacing them frequently, are more commonly preserved. In fact much of what we know about a number of extinct sharks (including the famous Megalodon) only comes from fossilised teeth. This limits what we can discern about the rest of their anatomy. But the Bearsden Shark was different. The fossil that Stan Wood found in 1982 preserved not just the teeth but the entire body. This happened because, by a stroke of luck, the Bearsden Shark was buried by thick mud very quickly after it died. This protected the carcass from being broken down by scavengers, decay and/or the surrounding environment. The preservation was so good that palaeontologists were able to identify muscles, blood vessels and even its last meal! It’s truly a unique fossil, and if you want to see it for yourself it’s on display at Glasgow University’s Huntarian Museum.

The Bearsden Shark belonged to a group of extinct relatives of sharks known as the Stethacanthidae. This group is known as the “Ironing Board Sharks” due to their most iconic feature; a large ironing-board like structure attached to their back. This board extends outwards into a wide, flat surface covered in small spines and is often described as being like an upturned ironing board or an anvil in shape (hence Akmonistion’s name meaning “anvil sail”). This structure is known scientifically as a “Spine Brush Complex” and only appears in male Ironing Board Sharks. So from this we can already deduce that the Bearsden Shark was male. What could possibly have been the purpose of this bizarre ironing board/brush structure? Palaeontologists still don’t know for sure! The fact that this structure only appears in males could indicate that they were display structures. The male with the largest board would be “more impressive” to the females and more intimidating to rival males. As a result over millions of years this board could evolve to become larger and more extravagant. Another suggestion is that the spines on the board could somehow have allowed males to attach themselves to a female during mating. Outside of this structure the Bearsden Shark (and its relatives) also possessed a patch of spines on the top their head (again only in males) and long thin strips trailing from their front fins (which palaeontologists also don’t know the function of!). Put this all together and you get a unique looking animal that would have been distinctly recognisable if you were out scuba diving in the Carboniferous seas. These features would also have affected the Bearsden Shark’s lifestyle outside of courtship. They meant that it wasn’t as streamlined and hydrodynamic as other sharks. Therefore it wouldn’t have been a fast swimmer and instead it would have cruised the sea floor, snapping at any small fish that wandered too close.

Akmonistion has not only influenced the field of palaeontology (by increasing our understanding of early sharks and their relatives) but has also been an influence on the local community of Bearsden. In 2016 a cairn and plaque were placed on the site of its discovery to simultaneously commemorate it and inform people about it. The Bearsden Shark is even the subject of a poem by Edwin Morgan, which I quoted at the beginning of this blog article. It’s a fun read and I’ve provided a link to it in the “References and Further Reading” below. Not many prehistoric animals can say that they have a poem in their honour!

The Bearsden Shark is an astonishing animal of earths’ past, and a great example of how diverse and wonderful sharks and their relatives both were and are. The week this blog article is coming out is the same week as “Shark Week”, a week-long event that is supposed to celebrate and educate people about sharks. While some places promote incorrect, negative ideas and stereotypes about sharks I hope that through the story of the Bearsden Shark you can catch a glimpse at their rich history, and why they absolutely should NOT be seen as simply monsters.

File:Akmonistion NT small.jpg - Wikipedia
The Bearsden Shark itself!
Image Credit: Nobu Tamura, http://paleoexhibit.blogspot.com/

References/Further Reading

Coates & Sequeira 2001 paper that fully described the Bearsden Shark fossil

M. I. Coates & S. E. K. Sequeira (2001) A new stethacanthid chondrichthyan from the lower Carboniferous of Bearsden, Scotland, Journal of Vertebrate Paleontology, 21:3, 438-459, DOI: 10.1671/0272-4634(2001)021[0438:ANSCFT]2.0.CO;2

The full Bearsden Shark poem by Edwin Morgan

A BBC news article about the plaque and cairn commenerating the Bearsden Shark

BBC News, “Shark ‘fossil wonder’ find commemorated at Bearsden site”, Glasgow & West, BBC News, https://www.bbc.co.uk/news/uk-scotland-glasgow-west-35092689

Enhydriodon: The Bear Otter

Enhydriodon, the bear-otter : Naturewasmetal
An Enhydriodon surprising an unlucky Aepyceros
Image Credit: Joschua Knüppe, https://www.deviantart.com/hyrotrioskjan

Well it was coming eventually! After 24 blog articles on this humble little site, it’s time that an article on Prehistoric Otter was actually about a Prehistoric Otter! There were a few candidates for the otter of choice for this momentous occasion, but ultimately I decided that Enhydriodon shall be the one in the spotlight. So sit back, grab some snacks, and let’s learn about the life and times of the “Bear Otter”.

Enhydriodon lived in East Africa and India from 5 to 2 million years ago during the Pliocene period of the Cenozoic era. As previously stated Enhydriodon was an otter and like all otters it belonged to a larger mammalian group known as the Mustelids, whose members also include Wolverines (the animal not the superhero!), Ferrets and Badgers. The earliest otters evolved around 23 million years ago with the first “modern” otters arriving on the scene 7 million years ago; a full 2 million years before Enhydriodon. Otters evolved from land based ancestors who became semi aquatic partly due to the exciting food resources available (e.g. fish, crustaceans and shellfish) and partly to help escape larger, scarier predators. Modern Sea Otters take this concept to the extreme and have become fully aquatic marine animals but the majority of todays otters still maintain a tie to the land. Otters took to their watery home with gusto and over millions of years they evolved webbed feet and a snazzy waterproof fur coat. This coat is so snazzy that unfortunately humans would hunt otters specifically for it, or even just for sport, to use the fur in the fashion business. Once these adaptations were in place the otters diversified and spread across the globe producing a wide variety of species. Along the way many species came and went, and Enhydriodon was one of them.

The first Enhydriodon fossils were discovered way back in the early 19th century, with the first known species, Enhydriodon sivalensis from the Sewalik hills in Northern India, being described and named by Dr Hugh Falconer of the British Museum. Since then further fossils have been unearthed of other Enhydriodon species. One notable species was described in 2011 and named Enhydriodon dikikae, which was found in East Africa; specifically Dikika in Ethiopia and Kanapoi in Kenya. What we know about Enhydriodon comes from a few fossils of a snout, lower jaw, back of the skull humerus and fragments of a femur. That’s not a lot to go on, but from what palaeontologists do have they can ascertain a few key features. For example, we know that its short snouted skull had a battery of broad incisors, powerful canines and crushing molar teeth. Luckily because we know of other similar extinct giant otters (such as the wolf sized Siamogale from South-West China, which lived just) we can compare these finds against these extinct otters and similar modern day otters in order to give us a rough reconstruction of its probable life appearance.

File:Enhydriodon campanii.JPG
A fossilised lower jaw of Enhydriodon campanii, another of the numerous Enhydridon species, from the Museo di Paleontologia di Firenze in Florence, Italy
Image Credit: Ghedoghedo, https://commons.wikimedia.org/wiki/File:Enhydriodon_campanii.JPG

So what makes Enhydriodon a particularly special otter? Well, from the aforementioned fossils scientists have estimated that Enhydriodon sivalensis was roughly the size of a panther. However this was topped by Enhydriodon dikikae, which grew to over 2.1 metres long and weighed somewhere between 200-400 pounds, making it the largest otter (and largest mustelid) that has ever lived. By comparison Enhydriodon dikikae was larger than your average Leopard or Wolf and even approached Lion size! This was certainly not the small, cute animal that most people associate with otters today. Instead it was a large and powerful beast (though in all honesty it was probably still cute).

How this otter is thought to have lived is a matter of some debate. The original paper that described Enhydriodon dikikae (Geraards et. al. 2011) concluded that it was more land based than modern otters. However others have argued against this stating that it was more semi-aquatic like an Asian Short-Clawed Otter. However long it spent in water what is clear is that it would have ventured in at least on occasion as its variety of powerful teeth indicate a diet of water and land based prey. Potential items on Enhydriodon’s menu ranged from large fish, such as catfish, and shellfish to even small-medium sized land based mammalian herbivores like antelope. This wide ranging diet is plausible based on what we know of modern otter species. For example the modern day Giant Otter from South America is known to prey on small-medium sized Caimans and Anacondas alongside its usual diet of fish.

The East African landscape that Enhydriodon dikikae lived in consisted of open forest and Savannah grassland, crisscrossed by rivers that fed into the occasional huge lake (not to far removed from today). The animals that this Enhydriodon would see on a daily basis were a real uncanny mix of different species. On the one hand, there were animals familiar to anybody who has either been on an African Safari or watched nature documentaries, like Antelope, Hippos and Leopards to name a few. But on the flipside there were a few strange faces. These included extinct animals such as Deinotherium; a gargantuan 4.5-5 metre tall relative of elephants that weighed twice as much and possessed downward curving tusks; the “Scimitar-Toothed” cat Homotherium, Sivatherium; a 3 metre tall relative of giraffes; and giant species of Wolverines (Plesiogulo) and Baboons (Dinopithecus).

There was another, very special animal that I haven’t mentioned yet that also lived alongside the large and powerful Enhydriodon; our very own ancestors! Those same Dikika and Kanapoi deposits where Enhydriodon dikikae fossils were found also contain the fossils of the 3.5 million year old Australopithecus afarensis (specifically the skeleton of a youngster nicknamed “Salem”) and the 4.2 million year old Australopithecus anamensis respectively. Australopithecus is a landmark human ancestor because it was one of, if not the first, to walk upright, a key feature that distinguishes humans from other great apes. It’s unknown just how much Enhydriodon and Australopithecus would have interacted with one another, but based on Enhydriodon’s diet and the comparative sizes of the two (Australopithecus was only 1 to 1.5 metres tall at most) it’s probable that the Bear Otter wouldn’t have said no to hunting an Australopithecus that was lingering too close to the waters edge. That’s such a strange thought. Nowadays people generally adore otters but in the distant past your great great etc. grandparents lived in fear of being eaten by one!

Enhydriodon dikikae | Dinopedia | Fandom
Enhydriodon compared to one of our ancestors. From this image you can see why encountering an Enhydriodon might have been a bad thing for these early human relatives!
Image Credit: Victor Leshyk, http://novataxa.blogspot.com/2012/04/2011-enhydriodon-dikikae-ethiopia.html

So why is the bear otter no longer with us? Well this may again be linked to our human ancestors. Enhydriodon went extinct roughly 2 million years ago during a time of significant decline of multiple large African carnivore species. Coinciding with this was the evolution and diversification of a couple of different new species of human (or “Homo”) such as Homo Habilis; one of the first human ancestors to make stone tools. Some of these human species were starting to incorporate more meat into their diet becoming omnivorous and active hunter gatherers. As a result they competed with Enhydriodon and other carnivores for prey, and this increased competition may have played a role in the otter’s decline. On top of this the climate was also changing, becoming drier and promoting more open Savannah and less forest. This new habitat wouldn’t have been as suitable for Enhydriodon and would have definitely affected its population.

To me, the most fascinating aspect of Enhydriodon is not its size, it’s not whether it was semi-aquatic or not, or even its appearance (though otter fans would surely go bananas if it was alive today). It’s the connection that it has to the history of humankind. As time has passed the relationship between our ancestors and Enhydriodon changed from an animal that was feared by the Australopithecines into one that early human species actively competed with on an equal footing. The relationship between humans and otters developed further after Enhydriodon went extinct with humans hunting its otter cousins for fur and sport, and now to protecting them through conservation efforts. I guess it just goes to show that otters have always had a relationship with the human species in one form or another, and Enhydriodon was the start of it all.

References/Further Reading

Geraards et. al. 2011 paper describing fossils of Enhydriodon dikakae from Ethiopia

Denis Geraads, Zeresenay Alemseged, René Bobe & Denné Reed (2011) Enhydriodon dikikae, sp. nov. (Carnivora: Mammalia), a gigantic otter from the Pliocene of Dikika, Lower Awash, Ethiopia, Journal of Vertebrate Paleontology, 31:2, 447-453, DOI: 10.1080/02724634.2011.550356

A book titled “Palæontological Memoirs and Notes of the Late Hugh Falconer: Fauna antiqua”, written by Dr Hugh Falconer where he describes his paleontological discoveries, which included Enhydriodon sivalensis

Falconer, Hugh, 1868, Palæontological Memoirs and Notes of the Late Hugh Falconer: Fauna antiqua, Fauna Antiqua sivalensis.

Mindat.org datasheet on Enhydriodon dikikae

Mindat, “Enhydriodon dikikae”, Mindat.org, https://www.mindat.org/taxon-8570226.html

A 2012 Nature article, written by Jeff Tollefson, detailing Lars Werdelin’s research on how competition with human ancestors may have played a role in Enhydriodons and other large African carnivore extinctions

Tollefson, Jeff, “Early humans linked to large-carnivore extinctions”, News, Nature, 26th April, 2012, https://www.nature.com/news/early-humans-linked-to-large-carnivore-extinctions-1.10508

Bobe et. al. 2020 paper on the ecology of Australopithecus anamensis, which includes details of the animals it shared its environment with (e.g. Enhydriodon).

René Bobe, Fredrick Kyalo Manthi, Carol V. Ward, J. Michael Plavcan, Susana Carvalho, The ecology of Australopithecus anamensis in the early Pliocene of Kanapoi, Kenya, Journal of Human Evolution, Volume 140, 2020, 102717, ISSN 0047-2484, https://doi.org/10.1016/j.jhevol.2019.102717.

Argentinosaurus: The largest the land has ever known

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A reconstruction of the skeleton of Argentinosaurus from the Museo Municipal Carmen Funes, Plaza Huincul, Neuquén, Argentina.
Image Credit: William Irvin Sellers, Lee Margetts, Rodolfo Aníbal Coria, Phillip Lars Manning, http://www.ploscollections.org/article/info:doi/10.1371/journal.pone.0078733;jsessionid=441A913F8D576BBA46BF0960D01599FD

35 metres long. Longer than a Blue Whale!

21.5 metres tall. Tall enough to look into a 6th story window.

80 tons. Heavier than the Space Shuttle “Endeavour”!

These aren’t the measurements of a building, they are not the dimensions of a ship, and they are not the specifications for a new jumbo jet. They belong to a single, now extinct animal. The largest to have ever walked on this world.

Its name is Argentinosaurus huinculensis (meaning “Argentina lizard of Huincul”). It was first discovered in the Neuquén Province of Argentina (hence the name) in the 1987 by a local rancher named Guillermo Heredia then revealed to the world in a paper written by Bonaparte & Coria in 1993. Remains of Argentinosaurus skeletons are fragmentary with only 13 intact bones having ever been found. These include vertebrae, ribs and a single incomplete femur all of which are huge in themselves. Even a single vertebrae is about 1.5 metres (5 feet) tall. But with only fragments such as these how can palaeontologists estimate Argentinosaurus’ enormous size? Well, one way that the weight can be estimated is by taking measurements of the minimum circumference of the upper arm bone (humorus) and thigh bone (femur), ideally from the same individual animal, then plugging them into a mathematical formula. This method can produce a range of estimates however, especially if we don’t have a humorus and femur from the same animal. So 80 tons may be an over or under estimation depending on who you talk to. The current estimated range of possible weights is between 77-110 tons! As for the height and length, it’s a matter of comparing the Argentinosaurus fossils with fossils of more complete close relatives and then determining the size based on the proportions of these relatives, taking into account the varying size, shapes and relative weights of the bones. This has problems too as it is based on assumptions about similarities close relatives. So the estimated proportions may not be 100% accurate, but it’s the best that palaeontologists can do at present.

File:Argentinosaurus 9.svg
A size comparison between an average person and Argentinosaurus. The bones shown are among the only ones palaeontologists have ever found. Image Credit: User:Slate_Weasel, https://commons.wikimedia.org/wiki/File:Argentinosaurus_9.svg

Argentinosaurus lived during the Mid-Cretaceous period, roughly 100-95 million years ago, and belonged to an order of dinosaurs known as the sauropods. The sauropods are among the most popular and recognisable dinosaurs out there and are typically characterised by long necks, long tails, elephant like bulk and of course by their large size. They first evolved during the Late Triassic/Early Jurassic period (roughly 200 million years ago) and the best known members (i.e. Diplodocus, Brachiosaurus and Brontosaurus) are from the Late Jurassic, around 155-150 million years ago. However by the time of Argentinosaurus the sauropods were a totally different group than how they were in the Jurassic. The Diplodocids, Brachiosaurids and Brontosaurs were long gone and in their place rose a group of Sauropods known as the Titanosaurs. The Titanosaurs were the largest herbivores of the Cretaceous, dominating the Southern Hemisphere (and bits of the Northern Hemisphere) for pretty much all of it, right up until the meteorite impact that marked the end of the non-avian dinosaurs 65 million years ago.

I’m sure the main question that a lot of people will have regarding Argentinosaurus is; How could a land animal have possibly grown this big? Well the reasons why Argentinosaurus could reach this size is due to the remarkable biology of sauropods, and dinosaurs as a whole. Firstly they had special bird-like lungs known as a unidirectional lung. In our mammalian lungs oxygen is extracted from the air we breathe in once as it cycles through the lungs, with the same air then being breathed out. However in birds, theropod dinosaurs and sauropod dinosaurs such as Argentinosaurus some of the air breathed in is stored in cavities, known as air sacs, which are attached to the lungs. These are specialised in these dinosaurs so that when they breathe out the air sacs push the stored air through the lungs again, giving them a second chance to extract oxygen. This increases the lungs efficiency and results in more energy being produced via respiration, enough to sustain larger body sizes. Secondly the bones of these large dinosaurs were more lightweight than you might expect. This is because they also contain air sacs that penetrated through the bones giving them an air filled honeycomb like structure. This hollows out the bones which lightens them, while allowing them to retain their strength. For example air sacs in the neck vertebrae of sauropods such as Argentinosaurus lightened the whole neck and reduced the force required to support them. These air sacs also provided a large surface area that allowed any excess heat to be dissipated. Those air sacs really were the key and without them an animal as big as Argentinosaurus wouldn’t have been possible. Other features of sauropods that allowed them to get very big were long necks and four column-like legs. Their necks allowed them to access vegetation that was out of reach of other animals and could also reach a wide area without them needing to move a lot. This means they could eat more food (and so generate more energy) while not wasting energy moving. Meanwhile their columnar legs, like those of an Elephant, were very effective at supporting and spreading weight out equally.

File:Argentinosaurus BW.jpg - Wikimedia Commons
Argentinosaurus huinculensis as it may have look in life.
Image Credit: Nobu Tamura, http://spinops.blogspot.com/

Argentinosaurus was, unsurprisingly, the largest herbivore in its environment and would have needed to have spent the majority of its life ploughing through vegetation to sustain itself. But even with its huge size it still would’ve needed to watch for predators. This was especially the case when they were young. An Argentinosaurus hatchling was comparatively tiny and wouldn’t have received much parental care or protection. So to survive they would have had to grow pretty quickly and their estimated growth rate was quite something. It is estimated that at its peak growth rate an Argentinosaurus could have gained 40kg in a day. That’s just over 6 stone! (for context that’s heavier than a Dalmatian, or even two). Even as an adult large predators such as Mapusaurus (a large predatory theropod dinosaur belonging to the Carcharodontosaurids) would have been a threat. However they may not always have hunted Argentinosaurus in the traditional sense. Instead they may have employed a tactic known as “flesh grazing”. This is where a predator bites chunks off an herbivore without killing it. An Argentinosaurus would have been so big that even a group of 12 metre long Mapusaurus may have preferred to attack Argentinosaurus in this way rather than risk exhaustion and death trying to bring it down. So in effect, to a Mapusaurus each Argentinosaurus would’ve been like a walking butcher shop!

While Argentinosaurus is generally considered by many to be the largest land animal ever, this is still a matter of debate. This is because other sauropod candidates have been put forward as the largest. One is called Bruhathkayosaurus (….yeah I can’t pronounce it either!) which is a Late Cretaceous (70-66 million years ago) titanosaur known from a few bones unearthed in India. Another is Amphicoelias, which has a whopping size estimate of 180 feet in length. However this is based on one set of measurements, made over a century ago by the palaeontologist Edward Drinker Cope, of a single vertebrae which has since mysteriously disappeared. Because that vertebrae was the only known fossil of Amphicoelias to date there’s no way to test the validity of this measurement. Another possible contender is Patagotitan, another mid-Cretaceous titanosaur from South America. Recent estimates have put Patagotitan at just a fraction smaller than Argentinosaurus. However almost all of these titanic titanosaurs share a problem. They are all reconstructed from fragmentary remains. This means that their size estimations often change as more material is found. Furthermore, different palaeontologists come up with different estimates. For example the most recent size estimates of Argentinosaurus and Patagotitan come from a study published in February of this year conducted by the palaeontologist Greg Paul. From his own measurements he revised the size estimations of many large sauropods and concluded that, as of right now, Argentinosaurus was slightly larger than Patagotitan. The debate will rage on until enough complete remains of the two are found to give more accurate estimations. To be honest, these two sauropods were so similar in size that I suspect that while the largest Argentinosaurus were the biggest land animal ever, some large Patagotitan may well have been bigger than many Argentinosaurus.

The sauropod dinosaurs were marvels of biological engineering, with multiple biological features combining to allow them to exist. Argentinosaurus pushed those features to their absolute limit. Its effect on the world around it, being a key cog in the ecosystem that it lived in, and its impact on the imagination of dinosaur lovers everywhere should not be underestimated. In the history of life on Earth there had been nothing quite like it before, there has been nothing like it since, and it’s quite possible that there won’t be anything like it ever again!

References/Further Reading

Bonaparte & Coria 1993. The paper that first described Argentinosaurus

J. F. Bonaparte and R. A. Coria. 1993. Un neuvo y gigantesco saurópodo titanosaurio de la Formación Rio Limay (Albanio-Cenomaniano) de la Provincia del Neuquén, Argentina [A new and huge titanosaur sauropod from the Rio Limay Formation (Albian-Cenomanian) of Neuquén Province, Argentina]. Ameghiniana 30(3):271-282

Paul 2019: A study conducted by Gregory Paul that rexamined the bones of the largest dinosaurs, concluding that Argentinosaurus was the largest

Paul, G. (2019). “Determining the Largest Known Land Animal: A Critical Comparison of Differing Methods for Restoring the Volume and Mass of Extinct Animals.” Annals of Carnegie Museum 85(4): 335-358, 324.

• Pages 114-117 of “The Rise and Fall of the Dinosaurs” by Dr Steve Brusatte gives a fantastic overview of the reasons why sauropods could grow so big. I highly recommend this book for anybody whose into dinosaurs as it details the group as a whole, the different types of dinosaur, how they lived, how they evolved and how they went extinct.

Brusatte, Steve, “The Rise and Fall of the Dinosaurs”, 2018, Macmillan, chapter 3, pg 114-117.

An article on Live Science by Laura Geggel on the topic of the worlds largest dinosaur.

Geggel, Laura, “What’s the World’s Largest Dinosaur?”, Live Science, January 27th, 2019, https://www.livescience.com/34278-worlds-largest-dinosaur.html

A National Geographic article, by Laelaps, discussing the biggest dinosaurs

Laelaps, “Biggest Dinosaur Ever? Maybe. Maybe Not.”, National Geographic, https://www.nationalgeographic.com/science/phenomena/2014/05/18/biggest-dinosaur-ever-maybe-maybe-not/

Aepyornis and the Elephant Birds of Madagascar

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A front view reconstruction of Aepyornis.
Image Credit: Acrocynus, https://it.wikipedia.org/wiki/File:Aepyornis_maximus_01_L.D..jpg

While it seems like I already know a bit about prehistoric life, before each of these blog articles I make sure to do my research on the animal that I aim to talk about, as any blog writer should do regardless of their subject area. During my research I not only broaden my knowledge, but also gain an extra appreciation for the animal in question. In the case of todays subject, Aepyornis (Greek for “high bird”), more commonly known as the “Elephant Bird”, my research showed just how little I actually knew about it. Aepyornis was a much more fascinating animal than I had realised (not just “a big ostrich”), and in this blog I aim to put the spotlight on this underrated animal.

For starters there wasn’t just one “Elephant Bird”; there was a whole family of them! “Elephant Bird” is the common name given to a family of flightless, bipedal, ostrich-like herbivorous birds from Madagascar known as the Aepyornithae. The “Elephant Bird” name originates from tales of the “Roc”; a legendary giant bird spoken of by Arab traders and written about by the famous explorers Marco Polo (13th century) and Ibn Battuta (14th century). It was also one of the monsters that the adventurer Sinbad encountered in “The Arabian Nights” tales (first published in the 18th century). It was said to be so big that it could carry an elephant in its talons. Polo in all likelihood based his Roc description on accounts of large, lemur hunting Malagasy Crowned Eagles that lived on Madagascar until the 16th century. However reports from other travellers of massive eggs, which belonged to Aepyornis, became associated with the Roc, and so the Aepyornithae family became collectively known as “Elephant Birds”. The Aepyornithae belonged to a larger order of birds known as the Ratites. This is the same group that contains ostriches, emus and cassowaries. You may think that since the Elephant Birds lived on Madagascar their closest relatives would be African ostriches since Madagascar lies off the East African coast. However this is not the case. Their closest living relatives are actually kiwis; small flightless birds which have long, thin beaks, reduced eyesight and are also ratites. Kiwis live only on New Zealand, which is 7,000 miles east of Madagascar! So how are these two birds so closely related despite living so far apart? Well the theory is that around 60 million years ago the common ancestor of kiwi’s and Elephant Birds still possessed flight and flew to these two separate islands, establishing colonies. Then, over millions of years, the two islands drifted further apart from each other (out of flying range) and the two separated populations both evolved flightlessness, independently of one another.

Another result of living on an isolated island for much of their evolution, and with no large mammalian herbivores to compete with, is that the Elephant Birds could grow to massive sizes. Aepyornis was no different and was thought to have been the largest bird that ever lived until relatively recently. Originally it was believed that Aepyornis maximus could grow to heights of more than 3 metres and weigh up to 800kg. However a study in 2018 by Hansford & Turney showed that there were enough skeletal differences between these largest specimens and other Aepyornis for these large Aepyornis to be re-classified as a new member of the Aepyornithae family (alongside Aepyornis and another Elephant Bird named Mullerornis). It was given the rather striking name of Vorombe titan, which is a combination of Malagasy and Greek and translates to “big bird” (Vorombe = Malagasy for bird, titan = Greek for big). As a result the size estimates of Aepyornis is now considered to be a more modest 2.5 metres tall and 400-500kg in weight on average, which is still larger than any living bird! Another of Aepyornis’ (and other Elephant Birds’) claims to fame is their humongous eggs. At their biggest they measured 34cm long, had a circumference of a metre and weighed 15 kilos. That’s 150 times bigger than a chicken egg, larger than any dinosaur egg and the largest eggs of any animal ever. Imagine the fried egg you would get from that! It wouldn’t just be enough for your breakfast; it would be enough to feed your entire family for the whole day! Such huge eggs would have meant that Elephant Bird chicks would have been more highly developed compared to other birds and the lack of any large egg thieves (before humans arrived) meant that it would have been safer for Elephant Birds to lay these eggs.

An Aepyornis egg (the large one!) from Museo Capellini in Bologna, Italy.
Image Credit: Ghedoghedo, https://commons.m.wikimedia.org/wiki/File:Aepyornis_egg.JPG

Aepyornis held the ecological niche of “large herbivore” on Madagascar. Its diet consisted of fruit, grasses and leaves and Aepyornis used its strong neck and overall size to reach them, before biting off and swallowing chunks with its beak. Unlike a lot of other large herbivores recent research has suggested that Aepyornis was a mostly nocturnal animal. The evidence comes from another 2018 study (by Torres & Clarke) where Aepyornis braincases were examined with a CT scanner. This produced a 3D model that the researchers could manipulate and examine in detail. Using this they discovered that Aepyornis had enhanced olfactory lobes (the part of the brain that processes smells) and reduced optic lobes (the part of the brain that processes vision). This is a similar, albeit less extreme, version of the brain structure of kiwis; which are nocturnal birds with limited vision and a reliance on smell to sense their environment. Furthermore Torres & Clarke also showed that different Aepyornis species had slightly different sensory lobes. You see there are two recognised species of Aepyornis; Aepyornis maximus (the larger, forest dwelling one) and Aepyornis hildebranti (the smaller, plains dwelling one). In A.maximus the olfactory lobes were proportionally larger, and the optic lobes proportionally smaller, than in A.hildebranti. This is presumably because A.maximus lived in dense rainforests, where eyesight is less useful due to the dense trees, while A.hildebranti lived in the open plains where the lack of dense trees meant they could see greater distances.

Aepyornis shared its Madagascan home with a menagerie of recognisable animals still alive today, such as Ring-tailed lemurs, Fossas and Chameleons. However it also lived alongside some strange animals that are no longer around. These included Archaeoindris, a giant lemur that was the size of a Silverback gorilla, the aforementioned Malagasy crowned eagle which modern lemurs still possess an innate fear of even though it is now extinct, and giant tortoises similar in size and lifestyle to the modern day Galapagos giant tortoise. So once upon a time Madagascar had an even greater diversity of life than it does now. However there are no Elephant Birds, giant lemurs, huge tortoises or giant eagles anymore. This is thought to have been mainly due to change in climate, which lead to changes in food availability. The actions of humans are also commonly linked to the disappearance of many Madagascan animals. However they may not have played as big of a role as previously thought. Yet another 2018 study (2018 should be renamed “Year of the Elephant Bird” due to all the studies carried out that year!) dated Elephant Bird bones that showed distinctive cut marks made by human tools to 10,500 years ago, the end of the Pleistocene period and start of the Holocene period. This was a whole 8,000 years earlier than humans had previously been thought to have reached Madagascar. Since Aepyornis and other Elephant Birds became extinct sometime between the 10th-12th Centuries (though sightings had been reported to as late as the 17th century) this means that humans co-existed with the birds for longer than previously thought. So they couldn’t have quickly hunted them to extinction as had been previously assumed. However this doesn’t mean that Aepyornis wasn’t a target for humans or that human activity wouldn’t have affected their numbers. For one the sheer size of both the animal and especially its eggs (which could be quickly poached from Aepyornis nests) would have been an attractive prospect for human hunters. For another humans were converting the Madagascan forests and plains into farmland, destroying Aepyornis’ habitat, and domesticated chickens and guinea fowl brought to Madagascar may have passed on bird related diseases to Aepyornis, which it had no immunity to.

Aepyornis skull from a skeleton at the Muséum national d’Histoire naturelle in Paris, France
Image Credit: LadyofHats, https://zh.m.wikipedia.org/wiki/File:Aepyornis_skull.JPG

So overall, Aepyornis was a truly splendid animal, with a much more varied and detailed history and lifestyle than at first glance. The Elephant Birds are reminiscent of a time 65 million years ago when the close relatives of birds ruled the world. The dinosaurs were long gone, but in this little corner of the world Aepyornis and its family carried on their legacy.

References/Further Reading

Torres & Clarke 2018: a study of the braincases of the Elephant Bird, and what it tells us about their noctournalism

Christopher R. Torres and Julia A. Clarke 2018, Nocturnal giants: evolution of the sensory ecology in elephant birds and other palaeognaths inferred from digital brain reconstructions, Proc. R. Soc. B.28520181540, http://doi.org/10.1098/rspb.2018.1540

Hansford & Turney 2018: a study on the diversity of the Elephant Bird (Aepyornithae) family, showing that the largest Aepyornis were actually a different species of Elephant Bird: Vorombe Titan

James P. Hansford and Samuel T. Turvey 2018, Unexpected diversity within the extinct elephant birds (Aves: Aepyornithidae) and a new identity for the world’s largest bird, R. Soc. open sci.5181295, http://doi.org/10.1098/rsos.181295

Hansford et. al. 2018: a study on Elephant Bird bones with human made cut marks dating from as far back as 10,500 years ago

James Hansford, Patricia C. Wright, Armand Rasoamiaramanana, Ventura R. Pérez, Laurie R. Godfrey, David Errickson, Tim Thompson, Samuel T. Turvey. Early Holocene human presence in Madagascar evidenced by exploitation of avian megafauna. Science Advances, 2018; 4 (9): eaat6925 DOI: 10.1126/sciadv.aat6925

An American Museum of Natural History page about the association of the Roc and Aepyornis, part of their “Mythic Creatures” exhibition

“Strike from the Sky”, Mythic Creatures Exhibition, American Museum of Natural History, https://www.amnh.org/exhibitions/mythic-creatures/air/strike-from-the-sky

A Smithsonian magazine article about the giant eggs of the Elephant Birds

Katz, Bridget, “Giant, Intact Egg of the Extinct Elephant Bird Found in Buffalo Museum”, Smithsonian Magazine, April 23rd, 2018, https://www.smithsonianmag.com/smart-news/giant-intact-egg-extinct-elephant-bird-found-buffalo-museum-180968850/

Bolton, Houston & Monaghan 1992: A study on the link between large eggs and survivability of baby birds

Bolton, M., Houston, D., & Monaghan, P. (1992). Nutritional Constraints on Egg Formation in the Lesser Black-Backed Gull: An Experimental Study. Journal of Animal Ecology, 61(3), 521-532. doi:10.2307/5607

Basilosaurus: The Tale of King Basil

A Reconstruction of how Basilosaurus (and the one and only King Basil) would have looked!
Image Credit: Dmitry Bogdanov, https://commons.wikimedia.org/wiki/File:Basilosaurus1DB.jpg

35 Million years ago during the Late Eocene period, in a shallow sea that would one day become the Sahara Desert, a king ruled the waters. His name was Basil, he was 20 years old and one of the largest of his kind. He has reached this age in large part because of the excellent early parental care of his mother, a key trait of mammals like him. He was taught how to navigate, to hunt and his mother used every ounce of her might to protect him from danger. Now he is in his prime, has fathered many offspring and has his pick of food that sustains his enormous appetite. Life is good for the king and there is nothing that can threaten him……for now.

Basil is a Basilosaurus, a name meaning “King Lizard” in Latin. However Basil and his kind are far from lizards! They are part of what was at the time a relatively new group of sea faring animals; the whales. Two species of Basilosaurus have been discovered. The first is Basilosaurus cetoides, which ranged from the coast of what is now Alabama and New Mexico in the USA to Egypt. The second is Basilosaurus isis, which swam in waters covering much of Morocco and Egypt. Combining the localities of these two species we can see that Basilosaurus had a wide geographical distribution, stretching across almost half the globe. Along this distribution both Basilosaurus species are thought to have resided in coastal and shallow water regions rather than the deep ocean; a slightly unusual habitat considering their huge size. Furthermore both Basilosaurus species lived in an ocean which no longer exists! This ocean was known as the Tethys, a once mighty watery expanse that linked the Indian and Atlantic Ocean. During the Late Eocene period it covered where much of Arabia, North Africa and the Mediterranean Sea area are now. The Tethys would eventually disappear around 23 million years ago but the coastal margins of this strange, primordial ocean was a place where Basilosaurus (and many other marine fauna) called home.

The fossilised skull of Basilosaurus isis (top) and Basilosaurus cetoides (bottom). Note the slight differences in teeth and skull shape between the two species.
Image Credit: Ghedoghedo, Ninjatacoshell, https://en.m.wikipedia.org/wiki/File:Basilosaurus_isis_and_cetoides_skulls_compared.png

The first Basilosaurus fossils were found in the 1830s. Rather curiously, when they were first unearthed, the large vertebrae were used as furniture! After this the fossils were initially studied by Richard Harlan, a Philadelphia based Naturalist, before being passed on to Sir Richard Owen, the famous British Naturalist who’s best known for coining the term “dinosaur” and for founding the Natural History Museum in London. Harlan at first thought that these bones belonged to a giant marine reptile, partly due to the animal’s unusually long body (like an actual sea serpent!) and superficially reptile-like skull. This is why it was given the name of Basilosaurus, or “King Lizard”. However later studies revealed Basilosaurus’ characteristic mammalian features. For example it was found to have heterodont dentition, which means they have teeth of various shapes each with their own function (in this case sharp incisors and flattened serrated molars). In contrast reptiles have homodont dentition, meaning their teeth are all the same shape and have the same function. Once he realised the mistake Sir Richard Owen suggested that this animal’s name should be changed to Zeuglodon; which means “Yoke Teeth” on account of their distinct shape. However this would have violated the golden rule of scientifically naming an organism; “The first name that is given is the one that is always used (unless the name is already in use or the new organism turns out to actually be one we’ve previously discovered and named)”. Therefore the name Basilosaurus stayed, resulting in the rather bizarre situation where a whale (which is a mammal) is called a lizard (which is a reptile). A great example of how palaeontology is full of weird names that sometimes don’t make sense!

A serpentine shape isn’t the only feature that differentiated Basilosaurus from modern whales. It also possessed small, stumpy and external hind limbs. While modern whales also possess hind limbs they are internal, hidden beneath the large layers of fat, muscle and skin. These tiny legs are remnants from a time (roughly 20 million years or so before Basilosaurus) when the ancestors of whales were small, four-legged hoofed mammals that were first dipping their toes back into water. Whereas these ancestors used their hind limbs for walking, Basilosaurus’ were way too small and stumpy for such a “feet” (sorry, couldn’t resist the pun). Instead it’s thought that the hind limbs were used to help lock and intertwine the long bodies of two Basilosaurus’ together during mating. Basilosaurus also lacked some characteristic anatomy that modern whales possess. This included a “melon” in their heads; a mass of tissue which modern whales use for echolocation. Furthermore Basilosaurus’ blowhole, which it used to take breaths at the surface, was positioned further forward (between the snout and top of its head) than in modern whales. As Basilosaurus preferred shallow water environments it is also thought that they didn’t dive to great depths (like Sperm Whales and Cuvier’s beaked whales do).

Mounted skeleton of Basilosaurus isis from the Museum d’Histoire Naturelle in Nantes, France
Image Credit: Asmoth, https://commons.m.wikimedia.org/wiki/File:Basilosaurus_isis_fossil,_Nantes_History_Museum_01.jpg

Basilosaurus was a giant of its time; measuring up to 20 metres long and weighing up to 20 tons. This meant that it was the undisputed top predator of the Late Eocene seas. The size of Basilosaurus varied between the two species; with B.cetoides measuring between 17-20 metres while B.Isis was between 15-18 metres. As you can see from this range in lengths there was also size variation between members of the same Basilosaurus species. One reason for this is that they exhibited sexual dimorphism. We know this because on average male Basilosaurus vertebrae measure 20% longer than in females of the same age. In terms of its lifestyle a modern day comparison to Basilosaurus might be the Orca (aka “The Killer Whale”). Both are large predatory whales that are top predators in their environments. Like Orcas, the diet of Basilosaurus consisted of fish (e.g. Pycnodus) and other marine mammals. One particular marine mammal that was on the menu was Dorudon atrox, a 5 metre long prehistoric whale which actually belonged to the same family as Basilosaurus; “The Basilosauridae” (guess what animal the family was named after). Fossils discovered in the last two decades have shown a direct predator-prey relationship between these two whales. Skulls of Dorudon have been found with bite marks that perfectly match the size and shape of Basilosaurus teeth. Furthermore these marks form a pattern on the Dorudon skull that indicate that the bite was across the head, a tactic that’s often used by predators to quickly immobilise and cripple their prey. In addition approximately 50% of these skulls were deduced to be of young Dorudon. This was due to the presence of deciduous (i.e. baby) teeth, while accompanying vertebrate had open growth plates which is the part of the bone that grows, before hardening when animal matures. This suggests that Basilosaurus targeted Dorudon “nursery groups” that consisted of young Dorudon and a few adults. It undoubtedly would have been a waking nightmare for the young Dorudon to see a large and hungry Basilosaurus burst into their nursery. But from the Basilosaurus’ perspective hunting the more vulnerable prey (e.g. young, old, injured and/or sick) gives them a greater chance of getting a vital meal, one that could prevent them from starving, and is a tactic employed by every predator from Lions, to Eagles, to Orcas.

King Basil eventually reached the end of his road as the years of swimming, hunting and fighting finally caught up to him. His latest wounds, sustained from a fight with a younger and faster male, are this time going to be fatal. As blood loss starts to take its toll Basil takes one last breath at the surface, before his body eventually gives out. The king has been dethroned. The younger male has long since swum off to start his own reign, but the line of succession will eventually end 33 million years ago. A drop in sea levels and a changing climate would push all Basilosaurus to extinction. As for Basil his body eventually sinks to the bottom of the sea and over time is picked clean by scavengers, buried by ocean sediment, and undergoes the fossilisation process that will turn his bones into hard rock. 35 million years later his bones will eventually resurface as another Basilosaurus fossil, with an intrepid palaeontologist meticulously dusting the sand of the Sahara Desert away to expose his remains. His final resting place is Wadi Al Hitan, a fossil site located 150km South-West of Cairo in Egypt. This place is also known as the “Valley of the Whales”. This is fitting, as just like the Egyptian pharaohs buried in the “Valley of the Kings”, Basil was a monarch among his own kind.

References/Further Reading

Fahlke 2012 paper that further examined the bite marks on Dorudon skulls, reinforcing the hypothesis that they match the teeth of Basilosaurus and that Basilosaurus actively hunted Dorudon

Fahlke, J. M. (2012). Bite marks revisited—evidence for middle-to-late Eocene Basilosaurus isis predation on Dorudon atrox (both Cetacea, Basilosauridae). Palaeontologia Electronica, 15(3), 32A.

Voss et. al. 2019 paper describing the preserved stomach contents of a Basilosaurus isis fossil

Voss M, Antar MSM, Zalmout IS, Gingerich PD (2019) Stomach contents of the archaeocete Basilosaurus isis: Apex predator in oceans of the late Eocene. PLoS ONE 14(1): e0209021. https://doi.org/10.1371/journal.pone.0209021

Uhen 2004 paper that first described the bite marks on Dorudon skulls and suggested that they were due to Basilosaurus predation

Uhen MD. Form, function, and anatomy of Dorudon atrox (Mammalia, Cetacea): an archaeocete from the middle to late Eocene of Egypt. University of Michigan Papers on Paleontology. 2004; 34: 1–222.

Fossilworks database on Basilosaurus species, synonyms and papers related to it

Fossilworks, “Basilosaurus Harlan 1834 (whale)”, Fossilworks, http://fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=36681

The New York Institute of Technology College of Osteopathic Medicine (try saying that five times fast!) page describing Basilosaurus (written by Robert Boessenecker and Jonathan Geisler)

Boessenecker, Robert, Geisler, Jonathan, “Basilosaurus spp.”, College of Osteopathic Medicine, The New York Institute of Technology, https://www.nyit.edu/medicine/basilosaurus_spp#

A Comparative Anatomy website page, from the University of the Cumberlands, giving an overview of Heterodont and Homodont Dentition

Comparative Anatomy, “The Teeth of Vertebrate Animals”, Comparative Anatomy, https://inside.ucumberlands.edu/academics/biology/faculty/kuss/courses/Digestive%20system/TeethOf%20Vertebrates.htm

“All hail the Great Beast Megatherium!”

File:Megatherium NT small.jpg - Wikimedia Commons
A reconstruction of the Great Beast
Image Credit: Nobu Tamura, (© N. Tamura), http://spinops.blogspot.com/2015/02/megatherium-americanum.html

“Deluded! Madman! Fake Scientist!”

The Cryptozoologist had been called these a lot throughout his professional career, (as well as other, more mean things). Time after time after time he had failed to discover any of the amazing creatures’ people claimed to have seen, with the majority being proven to never have existed in the first place. Now, nearing his retirement, he was wandering the amazon rainforest looking for yet another cryptid; the “Mapinguari”. “Just turn around” the voice in his head said (not for the first time). “They’re just stories made up to attract tourists or hoaxers trying to make a name for themselves or misidentified animals. None of them are real!”. The Cryptozoologist sighed, and for the first time in his life he wondered “Maybe I am a crazy old man”. Then he heard it, a crash of vegetation coming from the trees just to the left of him. He turned round, straining to locate exactly where the noise had come from. Then he saw it, and his jaw dropped. What he was seeing was an animal believed to have gone extinct 8,000 years ago. It was a great beast taller than an elephant and just as bulky, which possessed huge claws that it was currently using to pull down branches from a nearby tree towards its mouth. As he took out his camera and frantically took pictures two more large adults shuffled out of the forest, one of which had a baby clinging onto to its back. “They wouldn’t believe me” the Cryptozoologist thought. “But just wait till they see you!”

This “Great Beast” is known scientifically as Megatherium Americanum (meaning “Great Beast from the Americas”). Megatherium is an animal that palaeontologists have known about for a very long time. The first fossils were discovered in 1787, four decades before the first dinosaurs would be found, in Argentina by a man named Manuel Torres. After their discovery these bones were shipped to the Museo Nacional de Ciencias in Madrid, Spain, where they still reside today (another reason to visit Spain!). It was from these bones that French naturalist Georges Cuvier first described and named Megatherium, noting its close relation to modern day tree sloths. After these first fossils more were discovered, including bones found by Charles Darwin from 1832-1833 during the first Beagle expedition. Even nowadays new discoveries are revealing more insights. For example a paper published in 2017 (by Bocherens et. al.) looked at preserved collagen proteins in Megatherium fossils to give insights into its diet. Some people have gone a step further and claimed that Megatherium is still alive somewhere in South America. Stories from Brazil tell of the “Mapinguari” or “sloth monster”; a shaman who was transformed by the gods into a giant sloth-like creature. Cryptozoologists (like the one in the story) think the Mapinguari is actually a late surviving species of Megatherium, however scientists (and yours truly) don’t take these stories seriously due to absence of any concrete evidence.

A mounted skeleton of Megatherium with a awe inspired human for scale!
Image Credit: Beatrice Murch, https://www.flickr.com/photos/blmurch/3495336846

Megatherium belonged to a large order (or “superorder”) of mammals known as the xenarthans. Modern xenarthans include Tree Sloths, Anteaters & Armadillos, but during the Cenozoic era this group was much more diverse. From their origins in South America they ended up colonising North America, grew to a range of shapes and sizes and occupied a wide variety of habitats ranging from the treetops (e.g. modern tree sloths) to even the ocean (e.g. the swimming ground sloth Thalassocnus). Megatherium itself belonged to a sub-order of xenarthans commonly known as the “Giant Ground Sloths”. These sloths were very different from their slow moving and tree dwelling modern counterparts. They were bulky, ground living herbivores with large and sharp claws. While Megatherium itself was confined to South America other species of Giant Ground Sloths migrated across the Isthmus of Panama into Central and North America. This was during the great American interchange; a time where multiple species from South America migrated into North America (and vice-versa). As a result Giant Ground Sloths established populations in places such as Costa Rica, Texas and California.

Because multiple fossils of the “Great Beast” have been known to palaeontologists for some time we have a pretty good idea of what it would have been like. Megatherium roamed the South American pampas, mostly in Argentina, Bolivia and Uruguay, from the Pleistocene (roughly 400,000 years ago) to Early Holocene (roughly 8,000 years ago) periods of the Cenozoic era (a timespan commonly known as the “Ice Age”). This beast stood over 3.5 metres tall when fully upright and weighed up to 4 tonnes, making it the largest animal in South America during the Ice Age and the largest xenarthan ever. Its potbellied frame was supported by column-like hind legs that would have given it a long reach. Furthermore preserved Megatherium track-ways and its skeletal anatomy indicate that it could have walked on two legs as well as on all fours. Its front limbs were tipped with large, non-retractable claws which were used for pulling branches closer to them to eat and for digging up roots and tubers. In fact the claws were a reason that Megatherium was initially thought to have been a burrower, living like giant mole! Big claws would have undoubtedly been very effective defensive weapons with Megatherium using them, alongside its large size, to protect itself from predators, such as the large Sabre-Tooth Cat Smilodon populator. Other distinctive features include a relatively narrow snout, a prehensile upper lip (like a black rhino) and a thick shaggy coat. This coat is found on most Megatherium reconstructions and is based on the discovery of exceptionally preserved hair and hide specimens of related Giant Ground Sloths. However a study from 2002 (Fariña 2002) has speculated that Megatherium might’ve been nearly hairless! This is based on the observation that modern large mammals, such as elephants and rhinos, are mostly hairless to prevent them from overheating in hot climates (large animals produce a lot more excess heat). Megatherium may seem very different to what we would think of a typical large herbivore today. However the overall body plan of a large, bulky, bipedal herbivore with large claws has actually appeared a few times throughout earth’s history. One example is the Therizinosaur dinosaurs; a group which lived a full 65 million years earlier than Megatherium but is thought to have lived a similar lifestyle. This is an example of convergent evolution; where two completely unrelated organisms, often separated by millions of years of evolution, evolve similar body plans to live in similar ways. It’s a very fascinating phenomenon that has resulted in a lot of symmetry between modern and extinct animals (e.g. Dolphins and Ichthyosaurs).

A Megatherium looking at the horizon as two glyptodonts waddle by!
Image Credit: D. Bogdanov (DiBgd), https://commons.m.wikimedia.org/wiki/File:Pleistocene_SA.jpg#mw-jump-to-license

Such a majestic animal is another example how diverse the megafauna were during the last Ice Age. However the majority of these animals are not around anymore. Megatherium’s story is similar to other megafauna. Climate change at the end of the last Ice Age played a part, resulting in a loss of habitat and decline in population. This was combined with the arrival of modern humans into South America roughly 14,500 years ago. Some Megatherium bones bear distinct marks on them that indicate that they were cut by human tools. Furthermore other bones have been unearthed alongside human made stone tools and weapons. Tools, high intelligence and co-operation made humans a terrifying predator for a Megatherium to try and defend itself against and humans were so efficient that Megatherium numbers dwindled further. Eventually the dynasty of the Great Beast would come to a close 8,000 years ago. This unfortunate end makes one wish that the Cryptozoologists were right, and that Megatherium was somehow still living in South America to this day. If this were the case then I’m sure many more people would see what a “Great Beast” it really was.

References/Further Reading

Bocherens et. al. 2017 paper reconstructing the diet of Megatherium from analysis of collagen in the fossils

Bocherens et. al. (2017), Isotopic insight on paleodiet of extinct Pleistocene megafaunal Xenarthrans from Argentina. Gondwana Research, 2017; 48: 7 DOI: 10.1016/j.gr.2017.04.003

Billet et. al. 1997 paper examining the inner ear anatomy of Megatherium and what it tells us about its body mass and agility

Billet, G et al. “The inner ear of Megatherium and the evolution of the vestibular system in sloths.” Journal of anatomy vol. 223,6 (2013): 557-67. doi:10.1111/joa.12114

Natural History Museum website article profiling Megatherium and detailing a project that was digitally scanning all the fossils Charles Darwin collected on the 1831-1836 Beagle voyage

Brewer, Pip, “What was Megatherium?”, Natural History Museum, https://www.nhm.ac.uk/discover/what-was-megatherium.html

Fariña 2002 paper suggesting that the largest Giant Ground Sloths, such as Megatherium, were mostly hairless

Fariña, Richard. (2002). Megatherium, the hairless: appearance of the great Quaternary sloths (Mammalia;Xenarthra). AMEGHINIANA. 39. 241-244.

Politis et. al. 2019 paper, published in Sciences Advances, on the discovery of Megatherium remains that show evidence of Human Hunting

Politis, Gustavo & Messineo, Pablo & Stafford Jr, Thomas & Lindsey, Emily. (2019). Campo Laborde: A Late Pleistocene giant ground sloth kill and butchering site in the Pampas. Science Advances. 5. eaau4546. 10.1126/sciadv.aau4546.

Acanthostega: The shape of things to come

File:Acanthostega MLCS.JPG - Wikipedia
Acanthostega wondering what you’re looking at!
Image Credit: Conty, https://en.wikipedia.org/wiki/File:Acanthostega_MLCS.JPG

Throughout earth’s history there have been many major leaps in evolution; the evolution of eyes, the first multicellular animals and (from our point of view) the first time our hominid ancestors walked upright. However one that sticks out in a few people’s minds is when vertebrates first hauled themselves out of the water and started walking on land. To illustrate just how big this step was, imagine an alternate reality where it never happened. This parallel world would contain no reptiles, birds or mammals, and human civilisation would’ve never emerged. The vertebrates in this world are comprised of a wide variety of fish species swimming in seas, lakes and rivers across the world alongside a range of molluscs, crustaceans and corals (to name a few). On land the world is still covered in thousands of plant species but the only animals are invertebrates. Beetles, arachnids, and ants of all possible sizes scuttle along the ground. Dragonflies, wasps and flies buzz and dance through the air and worms bury through the soil keeping the ecosystem together. All in all, it is a world radically different to what we know.

As a result documenting how and why this important moment in life on earth occurred is key to understanding the world around us. One animal that has helped palaeontologists to do this is a 60 cm long stem-tetrapod that swam the rivers of Greenland during the Devonian Period (360 million years ago). Its name was Acanthostega gunnari, meaning “Gunnars spiny roof”.

File:Acanthostega model.jpg
A model of a swimming Acanthostega
Image Credit: Dr. Günter Bechly, https://commons.wikimedia.org/wiki/File:Acanthostega_model.jpg

While fossils of Acanthostega were first discovered in 1933 (and described in 1952 by Gunnar Säve-Söderbergh, who the species is named after, and Erik Jarvik) the majority of what we know about it comes from a magnificent bone bed, part of the Celsius Bjerg Group rock sequence found in East Greenland, that was discovered in 1987 by a team led by Palaeontologist Jenny Clack. These beds contains the remains of multiple Acanthostega buried and preserved with their skeletons almost completely intact. A paper released in 2016 (Sanchez et. al. 2016) detailed another interesting observation about these fossils. Micro CT synchrotron scans of the interior of the arm bones showed that the bones were still reasonably cartilaginous and had yet to fully ossify (i.e. harden into fully formed bones). This ossification happens as animals mature, so it was deduced that all of the 1987 fossils were of juvenile Acanthostega (roughly around 6 years old) who seem to have been living together. The ossification process also seemed to have progressed further in some individuals than in others, suggesting that there was size variation between members of the group, either through genetic variation, sexual dimorphism or even both. Tragically for this ragtag group of youngsters, it seems that they all died together. It is thought that a flash flood might have washed all of them into a small pool of water. This then dried up after the flood receded leaving them stranded and exposed to the elements, away from the water that kept their skin from drying out.

Acanthostega is a great example of a transitional fossil. Its anatomy is comprised of both basal fish-like features (e.g. internal gills, fish-like teeth, fleshy tail fins and a lateral line system) and derived tetrapod-like features (e.g. simple lungs and limbs tipped with digits). Curiously all these features would have made Acanthostega perfectly suited for its river home. It used its fleshy tail to power itself through its river home, snapping at any fish that wondered too close, and to help locate its prey and navigate through its watery environment it used a lateral line system to sense movement and pressure gradient changes. These features (along with its internal gills) meant it stayed underwater for long stretches of time, though its simple lungs enabled it to take breathes of air if required. What surprised palaeontologists the most about Acanthostega was the structure and function of its limbs and the number of digits on each limb. The limbs were not large or robust enough to bear Acanthostega’s weight for long, meaning it would only rarely spend time on land (if at all). Instead the limbs acted as paddles, aiding with swimming and manoeuvring underwater. This is important because it showed that the early tetrapods didn’t evolve limbs when they started walking on land, but instead first evolved them to better aid them underwater. Then later in time they would adapt this pre-existing feature to use for walking on land. The story is the same for its digits. Each of Acanthostega’s limbs were tipped with 8 digits. This showed that the number of digits on stem-tetrapod limbs wasn’t restricted to a set number (originally thought to have been 5). These early digits would have had webbed and made the early limb a more effective paddle. Then later in evolutionary time digits (like limbs) evolved to help bear and spread out the vertebrate’s weight when it was on land.

File:Acanthostega gunnari.jpg - Wikimedia Commons
A skeletal of reconstruction of Acanthostega. Note its 8 digits, flat skull and paddle-tail.
Image Credit: Ryan Somma, https://commons.wikimedia.org/wiki/File:Acanthostega_gunnari.jpg

Looking at all of its features its certain that Acanthostega would have actually spent almost all of its time in water, patrolling the waterways and hunting for small fish and arthropods. Its fish like skull features and relatively weak bite force (adapted more for gripping prey) compared to later tetrapods were perfectly adapted for catching slippery aquatic prey, meaning it didn’t hunt terrestrial animals. Like modern day amphibians Acanthostega would have laid its eggs in water as the eggs lacked a hard watertight casing. Throughout its life Acanthostega would also have had to watch its back! Multiple species of large freshwater fish were alive during the Late Devonian and many of them would have seen Acanthostega as a tasty meal.

So while Acanthostega wouldn’t have been much of a “land lubber”, it was a shape of things to come. This small river dweller helped palaeontologists to figure out the early evolutionary history of the stem-tetrapods and showed that limbs and digits, those features that you use every day, were first developed for underwater use, and only later on evolved for use on land.

All that we know about Acanthostega, the evolution of limbs and digits and how vertebrates first ventured out of the water, couldn’t have been possible without the hard work and dedication of Jenny Clack. Before her work this evolutionary transition period wasn’t particularly well understood. However her meticulous research on every facet of Acanthostega (whose fossils she sometimes gave nicknames to, such as “Boris”, “Rosie” and “Grace”) and its relatives, revolutionised our understanding of this key period of vertebrate evolution. She was one of the world’s leading experts on stem-tetrapods and Acanthostega in particular. This is clear to see as almost every scientific paper released about Acanthostega over the last three decades has carried her name either as a researcher or as a source. Sadly Jenny Clack passed away in March of this year (at time of writing). She will be greatly missed by her friends, family and the wider scientific community. With her passing, the world has lost one of the great palaeontologists.

References/Further Reading

Sanchez et. al. 2016 paper detailing the growth and life history of Acanthostega

Sanchez, S., Tafforeau, P., Clack, J. et al. Life history of the stem tetrapod Acanthostega revealed by synchrotron microtomography. Nature 537, 408–411 (2016). https://doi.org/10.1038/nature19354

Clack 2002 paper on the skull roof of Acanthostega

Clack, J. (2002). The dermal skull roof of Acanthostega gunnari, an early tetrapod from the Late Devonian. Transactions of the Royal Society of Edinburgh: Earth Sciences, 93(1), 17-33. doi:10.1017/S0263593300000304

Neenan et. al. 2014 paper on the feeding biomechanics of Acanthostega

James M. Neenan, Marcello Ruta, Jennifer A. Clack and Emily J. Rayfield (2014) Feeding biomechanics in Acanthostega and across the fish–tetrapod transition, Proc. R. Soc. B.28120132689, https://doi.org/10.1098/rspb.2013.2689

Porro, Rayfield & Clack 2015 paper on a 3d reconstruction of an Acanthostega skull. This allowed the trio to infer how Acanthostega caught prey.

Porro, Laura B et al. (2015) “Descriptive anatomy and three-dimensional reconstruction of the skull of the early tetrapod Acanthostega gunnari Jarvik, 1952.” PloS one vol. 10,3 e0118882, doi:10.1371/journal.pone.0118882

Tree of Life web project section on Acanthostega, written by the Late Jenny Clack

Clack, Jennifer A. 2006. Acanthostega. Acanthostega gunnari. Version 13 June 2006. http://tolweb.org/Acanthostega_gunnari/15016/2006.06.13 in The Tree of Life Web Project, http://tolweb.org/

Another Tree of Life project section written by Jenny Clack on the definition of “Tetrapod” and how it is debated

Clack, Jennifer A. 1997. The Definition of the Taxon Tetrapoda, 1997, http://tolweb.org/accessory/Definition_of_the_Taxon_Tetrapoda?acc_id=471 in The Tree of Life Web Project, http://tolweb.org/

The University of Cambridge Department of Zoology news article on the passing of Professor Jenny Clack

Aucott, Rachael, “Professor Jenny Clack, FRS, 1947-2020”, University of Cambridge, 26th March, 2020, https://www.zoo.cam.ac.uk/news/professor-jenny-clack-frs-1947-2020

A Science Direct web page about lateral line systems

Science Direct, “Lateral Line System”, Science Direct, https://www.sciencedirect.com/topics/medicine-and-dentistry/lateral-line-system

Clack & Neininger 2000 paper on the Celsius Bjerg Group, a rock sequence that Acanthostega fossils have been found in

Clack, J. A. and S. L. Neininger (2000). “Fossils from the Celsius Bjerg Group, Late Devonian sequence, East Greenland; significance and sedimentological distribution.” Geological Society, London, Special Publications 180(1): 557-566.

Yi qi: The Dragon of the Jurassic

The Jurassic Dragon takes flight!
Image Credit: Emily Willoughby, https://commons.m.wikimedia.org/wiki/File:Yi_qi_restoration.jpg

In a dense forest, full of hissing, rumbling and bellowing noises, a dragon perches on a branch. Using its sharp eyesight it locates its next meal; a large beetle crawling along a tree trunk 50 metres away. The dragon stretches its leathery wings and takes flight, swooping down silently with barely a flap towards its prey. However, just before the dragon can strike the beetle notices and unfurls its own wings in a desperate attempt to escape. But with a couple of quick flaps the dragon adjusts in mid-air and intercepts, snapping it out of the air with its toothy jaws. The beast lands and swallows the meal. But this is only a starter, and the little dragon surveys the forest again before moving on in search of the main course.

Believe it or not this really did occur in the Late Jurassic forests of China. But with one difference. The animal in question was not a mythological dragon, but a dinosaur named Yi qi.

The binomial name Yi qi, meaning “Strange Wing” in Chinese, is the shortest scientific name given to any dinosaur, and one of the shortest names of any animal living or extinct. It belonged to a family of theropod dinosaurs known as the Scansoriopterygidae (a real tongue twister of a name). Yi qi is one of only three known members of this group (the others being Epidexipteryx and Epidendrosaurus/Scansoriopteryx) and as a result relatively little is known about their evolutionary history and general lifestyle. The Scansoriopterygidae were part of a wider theropod order known as the paravians; which includes the dromaeosaurs (i.e. raptors) and all birds (that’s right ALL birds). However the Scansoriopterygidae seem (unless future discoveries say otherwise) to be an example of an evolutionary dead end as they are only known from sites from the Mid-Late Jurassic (and potentially Early Cretaceous) China and nowhere else.

Size comparison between Yi qi and a human being
Image Credit: Matthew Martyniuk, https://commons.m.wikimedia.org/wiki/File:Yi_scale.png

Yi qi was roughly the size of a pigeon with toothed jaws, forward facing eyes, sharp claws, long thick tail feathers and simple filament feathers covering its body, head and upper arms. The fossilised feathers are so well preserved that even the melanosomes (the small organelles that give feathers and other biological structures colour) were clearly preserved. Examination of the shape of these melanosomes, and comparison with melanosomes in living birds, showed that Yi qi had a black/grey body with reds and yellow colours on its arms. This gave it a distinctive contrasting colour scheme with the red/yellow arms perhaps used for signalling or species recognition. So far from this description Yi qi sounds more like a bird than a dragon! However when palaeontologists examined its forearms they made an astonishing discovery. An elongated third finger extended from both its hands and a long rod like bone (known as a styliform) jutted out from its wrist. These supported a skin membrane, known as a patagia, connecting the ends of its elongated fingers to the end of the styliform. It’s theorized that this membrane would also have stretched from the end of the styliform to the body, giving Yi qi “bat-like” wings (though another competing theory is that Yi qi would have had skin membranes like those of a modern gliding tree frog). These unique wings give Yi qi and its close relatives an appearance unlike any dinosaur, bird or pterosaur, one that draws comparisons with a dragon (specifically a “wyvern”). Whether Yi qi would have used these wings for powered flight or gliding (like a flying squirrel) is unclear. However it may have employed a combination of the two; long distance gliding (or as Buzz Lightyear would say “falling with style!”) and powered flapping for initial take off and manoeuvring through the air. Yi qi’s discovery also shows that flight had evolved in dinosaurs on multiple occasions, with the bat winged Yi qi being only one such evolutionary experiment.

The one and only Yi qi fossil. Note the feather covering around its body and head, as well as the styliform on its elongated wrist.
Image Credit: Kumiko, https://www.flickr.com/photos/kmkmks/27011985534/

All we know about Yi qi so far comes from one remarkable fossil that was discovered in 2007 in the Hebei province of China. It was found in the Mid-Late Jurassic age Tiaojishan formation of rocks. This is important as a large proportion of feathered dinosaurs are known from the Early Cretaceous onwards (20-30 million years after Yi qi). Therefore its discovery shows that feathers were present on dinosaurs far earlier than initially thought, with some palaeontologists suggesting that they originated even earlier than Yi qi. After its discovery the fossil was studied by a team led by the eminent Palaeontologist Xu Xang, who has described and named a whole menagerie of Chinese dinosaurs (e.g. the feathered tyrannosaur Yutyrannus). Yi qi was revealed to the world in a paper released in 2015 and it’s strange, dragon like appearance meant that it, like many dinosaur discoveries from China in the last few decades, made headlines around the world.

Yi qi is one of the most unusual dinosaur discoveries of the last decade. It proves, beyond a shadow of a doubt, that the world of palaeontology continues to unearth astounding discoveries. Discoveries that add more paint to the canvas that is the history of life on earth.

References/Further Reading

The original Xu et. al. 2015 paper describing Yi qi

Xu, X., Zheng, X., Sullivan, C. et al. A bizarre Jurassic maniraptoran theropod with preserved evidence of membranous wings. Nature 521, 70–73 (2015). https://doi.org/10.1038/nature14423

A blog (originally from tetrapod zoology) published in Scientific American by palaeontologist Darren Naish on Yi qi and theories on its lifestyle and features

Naish, Darren “Yi qi Is Neat but Might Not Have Been the Black Screaming Dino-Dragon of Death”. Scientific American, May. 5, 2015, blogs.scientificamerican.com/tetrapod-zoology/yi-qi-is-neat-but-might-not-have-been-the-black-screaming-dino-dragon-of-death/

A blog written by Nick Garland and published in Earth Archives on Yi qi

Garland, Nick “Meet Yi qi, the dinosaur with bat-like wings and feathers”. Earth Archives, 2015, eartharchives.org/articles/meet-yi-qi-the-dinosaur-with-bat-like-wings-and-feathers/

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/

Daeodon the Terminator

How the Terminator Pig is thought to have looked like!
Image Credit: Max Bellomio, https://commons.m.wikimedia.org/wiki/File:Daeodon_shoshonensis_.png

Daeodon is an animal that has had a lot of rather intimidating nicknames associated with it over the years. These have ranged from the “Terminator Pig” (which makes me think of a pig wearing sunglasses and travelling through time on a mission to destroy!) to the “Hell Pig” (which suggests a giant boar rising from a fiery pit accompanied by heavy metal!). Even its name “Daeodon” translates as “Dreadful Teeth”, a name that would strike fear into the hearts of dentists everywhere. But what was Daeodon really like? And did it deserve its reputation?

Daeodon belonged to a now extinct branch of the “artiodactyls”, a mammal group that also contains pigs, horses and even whales, known as the Entelodontidae, or “Entelodonts”. In life Entelodonts would have looked superficially pig-like with a long snout, hooved feet, tall shoulder hump, short tail and a round body. The “terminator” and “hell” parts of its nicknames stem from its huge size, Daeodon was the size of a bison, and it’s grotesque looking face which possessed side flanges, bony bumps and fearsome looking teeth. However despite appearances the Entelodonts’ closest relatives are not actually pigs. A study published in 2009 by Michael Spaulding, Maureen O’Leary and John Gatesy found that, whilst studying the ancestry of the artiodactyl group, they were more closely related to the whippomorpha subgroup (which contains hippos, whales and dolphins) than modern pigs. This has changed some reconstructions of entelodonts into a more bulky animal than previously thought, more akin to a land-based hippo than an oversized pig. So maybe the famous nickname of “terminator pig” should now be “terminator hippo”, which is just as horrifying considering how aggressive and dangerous modern hippos are! Entelodonts were a very successful group of mammals. First evolving in Mongolia roughly 40 million years ago during the Eocene they diversified into multiple different species that spread into Europe and North America during the Oligocene and Miocene. Daeodon was in many ways the culmination of this line, being not only the largest entelodont but also one of the last.

The skull of Daeodon showing its strong build and differentiated teeth.
Image Credit: Matt Celeskey, https://commons.m.wikimedia.org/wiki/File:Daeodon_skull.jpg

Roaming the plains of North America from 25-18 million years ago, Daeodon lived alongside a weird menagerie of life consisting of animals both familiar and unfamiliar. Alongside the ancestors of today’s horses and camels were extinct animals like the Chalicotheres, relatives of horses that walked on their knuckles like gorillas and possessed large claws that they used to pull down vegetation, and Hyaenodonts, mammalian carnivores that belonged to the now extinct Creodont group. Standing 1.8 metres tall and weighing roughly half a tonne Daeodon would have been an imposing animal in this environment. The distinctive flanges on its 3 ft. long head covered large cheek bones and were anchor points for large jaw and neck muscles, giving it a very powerful bite. Despite its fearsome appearance however, Daeodon was an omnivore. It possessed differentiated teeth just like in humans; gripping incisors at the front, large canines in the middle and crushing molars at the back. This enabled it to eat almost anything it came across including roots and tubers, fruit, leaves and meat. It would have been a very effective scavenger as a highly developed sense of smell would allow it to locate a carcass accurately from a distance, tracking the smell in a zig-zagging fashion. Furthermore its large size would have enabled it to drive off other animals from the kill. Make no mistake however, Daeodon would have dabbled with hunting live prey as well. It is thought to have been an ambush hunter, using its large size and powerful jaws to overpower and crunch through prey. But it’s not just other animals that Daeodon would have fought. Puncture marks found on the skulls of other entelodont species have shown that they fought each other, whether for mates, territory or both. So in many ways, given its large size and omnivorous lifestyle, Daeodon might have had a similar lifestyle to a modern day Grizzly Bear. Sadly this magnificent beast isn’t around today to give Grizzly Bears a contest. The last Daeodon went extinct around 18 million years ago. This coincided with the first emergence in North America of the large Bear-Dog Amphicyon (see my Amphicyon blog for more!), which had migrated from Asia. This predator, while smaller, was swifter and most importantly; more intelligent. As a result it seems to have partly out-competed Daeodon. Combining this with a climate which was becoming drier as the Miocene progressed resulted in Daeodon being driven to extinction, leaving only their fossils as remnants of a once widespread group.

Speaking of these fossils, the first Daeodon fossils were discovered in 1879 by the American fossil collector Edward Drinker Cope. Cope is a big name in the field of palaeontology, being responsible for the discovery of many extinct species such as the sauropod dinosaur Camarasaurus and the sail backed stem-mammal Dimetrodon. He is also known for his bitter rivalry with fellow American fossil hunter Othniel Charles Marsh. The two were locked in a race to discover and describe the most new species in a rivalry that has been termed “The Bone Wars”. When Cope examined Daeodon he determined it to be a member of the perissiodactyls, a group of mammals that contain modern day Zebras and Rhinos. It was only in 1909 when it was found that this wasn’t the case and it was actually an artiodactyl. For a long time Daeodon wasn’t the most widely known entelodont, with Dinohyus (meaning “terrible pig”) taking that title. However later it was found that Dinohyus and Daeodon, and another entelodont named Ammodon were actually one and the same animal. Because the rules of species dictate that the first name given to a species is the one that is kept Daeodon was the winner out of the three, with Dinohyus and Ammodon becoming synonyms.

A skeletal of Daeodon, showing how the bones all fit together and how big the animal was compared to a human.
Image Credit: bLAZZE92, https://blazze92.deviantart.com/art/Daeodon-shoshonensis-419367474

Entelodonts were a bizarre group of mammals, with Daeodon being the most eye-catching and iconic of them all. It dominated the North American landscape and while its size and power certainly earns it the “Terminator Pig” nickname (minus the pig part of course) that was only one side to it. As well as being a big and intimidating hunter and fighting for what it wanted, Daeodon would have eaten its greens, rolled happily in the mud and napped peacefully in the sun!

References/Further Reading

Spaulding, O’Leary and Gatesy 2009 paper on the family tree of artiodactyls, including who Entelodonts are most closely related to

Spaulding, Michelle et al. “Relationships of Cetacea (Artiodactyla) among mammals: increased taxon sampling alters interpretations of key fossils and character evolution.” PloS one vol. 4,9 e7062. 23 Sep. 2009, doi:10.1371/journal.pone.0007062

Joeckel 1990 paper on entelodont paleoecology and jaw function

Joeckel, R. (1990). A functional interpretation of the masticatory system and paleoecology of entelodonts. Paleobiology, 16(4), 459-482. doi:10.1017/S0094837300010198

A blog, written by Joe Sawchak and published on the Carnegie Museum of Natural History website, about a life size model of Dinohyus named “hyus”. This model was characterised by the weirdly human eyes!

Sawchak, Joe, “Dinohyus: “Terrible Pig” in more ways than one”, Carnegie Museum of Natural History, carnegiemnh.org/dinohyus-terrible-pig-in-more-ways-than-one/

An article, written by Vasika Udurawane and published on Earth Archives, about the rise of the “Terminator Pigs”

Udurawane, Vasika, “Terminator pigs: Rise of the entelodonts”, Earth Archives, 2016, eartharchives.org/articles/terminator-pigs-rise-of-the-entelodonts/