Some Dinosaur Detective Work


The Dinosaur skeleton in Kelvingrove Art Gallery and Museum has always been a major tourist attraction and childhood favourite of mine. Yet there is a 150 million year old secret hidden in its fossil bones in plain sight of museum visitors. This blog post will equip you in uncovering these secrets with the use of some of the basic observations paleontologists employ when trying to uncover the lifestyle of a particular long dead fossil.

A rainy day in Glasgow's west end inevitably led me to take shelter in Kelvingrove Art Gallery and Museum (left). As one of Scotland's top visitor attractions and having an excellent selection of fossils representing Scotland's geological past, I would definitely recommend a visit.

The centre piece of that particular exhibit would have to be the dinosaur skeleton, you find it leaping at you as you enter the exhibit from under the archway. This, like many others I imagine, is a must go to spot when I come to Kelvingrove. The impressive specimen with those claws, dagger-like teeth and interesting horns on its head still gets me every time. It would have definitely been a ferocious beast when it was alive, something you wouldn't want to meet in a dark alleyway. This dinosaur (which this particular blog post will intensively focus on) like all others typically has a long, arduous Latin or Greek name, in this case 'Ceratosaurus nasicornis'. It translates to 'horn lizard' referring to those unique horns on its head that characterises the genus. Another characteristic trait is its four fingered claws, a primitive feature as many of the meat-eating dinosaurs, known collectively as 'theropods' are three fingered. As impressive as 'Ceratosaurus nasicornis' is, it has never to date been found in Scotland, even though it is the main feature of the exhibition! This is not a total deception on the museum's part as dinosaur fossils have been in Scotland; on the Isle of Skye - Scotland's Jurassic Park. However, this has been in the form of isolated material, one which includes a possible leg bone of a small ?Ceratosaur. Not really something that is going to grab the public's imagination. For a complete skeleton and the public wow factor, I imagine that's why the museum used the larger, more complete American relative; 'Ceratosaurus nasicornis' (Wikipedia, 2017).

The Dinosaur skeleton at Kelvingrove (left) is identified by its nameplate description (right) as 'Ceratosaurus nasicornis'. In life, Ceratosaurus was a ferocious predatory dinosaur yet despite this it only occupied the middle level of the Late Jurassic food web.

Life reconstruction of 'Ceratosaurus nasicornis' (below) (DiBgd, 2007).

'Ceratosaurus nasicornis' is a quite formal, long winded name to keep calling our skeleton, which tells us a unique story about the animal that we will investigate in detail. From now on I will refer to our skeleton as 'Sara' from the pronunciation of 'seh-RAT-oh-SORE-us' - ('Sara' for short).

Imaginary scene of Sara's world during the Late Jurassic Period ~150 mya ©John Sibbick.

Sara (foreground) would have inhabited semi-arid plains of what is now western North America, which she shared with a huge variety of other dinosaurs. This assemblage was dominated by various types of giant, long-necked sauropods (midground) which fed on the conifer forests (background) that grew by temporary river systems that existed from time to time. The changeable climate led to drought and flash floods that would concentrate dinosaur bones in bone beds, preserving them for millions of years. (Selden & Nudds, 2004).

'Palaeontological CSI'

The forelimbs (left), the coracoid bone, which makes up part of the shoulder and is the attachment point of the forelimbs, via the humerus (upper arm bone) (Wikipedia, 2017) (middle) and the hindlimbs (right).

If we want to better understand how Sara (as an individual) lived, we have to start thinking like a paleontologist. While an expertise in Ceratosaur anatomy would aid you here, all you really need is to use some basic observation of the skeleton as her bones tell a story. Take the middle image for example, do you notice the rough, knobbly structure on the left flat, disc-like coracoid bone? Looks rather unusual doesn't it? It doesn't feature on the right coracoid bone so it shouldn't be there. But what is it? It can't be excess rock still attached to the fossil as this would have been removed when preparing the specimen for museum display. Perhaps you are thinking as it is a cast the structure formed as the material was setting, however, we find this same structure on the original skeleton. So, what is it? As this structure is present on the original fossil bone, this oddity is unique to Sara herself. It is what palaeontologists refer to as a 'pathology'; an abnormality on the fossil formed as a result of injury or disease (Vocabulary.com, 2017). It could be a possibility that we be looking at an 150 million year old example of bone cancer here (however, I discuss all the identified pathologies in context later on). These pathologies didn't immediately kill Sara, as her bones show signs of healing and fusing together as if they were broken or damaged. However, it is quite likely these injuries contributed to Sara's untimely death, as she was not yet fully grown when she died. We will now look at Sara's other pathologies (below) and further discuss there significance.

(Pathologies identified on "Sara's skeleton" are highlighted (see left)).

Notice that all the pathologies surprisingly occur on the left side of the skeleton. Is this a coincidence? Possibly, but I think it is a reasonable deduction to say that the multiple injuries Sara was inflicted with, in life could have all occurred in the same event. If so, what was this terrible event happened to Sara??? Again, we can only speculate however, to my knowledge dinosaur pathologies are not rare, especially amongst those predatory meat-eating dinosaurs, the theropods. This is because that Sara and her kin led a 'live fast die young' lifestyle in which being a predator especially during the Jurassic Period would put you directly in all sorts of danger. This is particularly true for Sara who hadn't reached her full size before her death (adult Ceratosaurus could reach an impressive size of 6 metres in length when fully grown (Dixon, 2006)). There are many possibilities to what might have happened to Sara. So, I've listed my two favourite theories below:

1) Sara was injured while hunting other dinosaurs

Hunting is one of the most perilous times for a predator and it doesn't always result in a successful kill. There is the serious risk of becoming seriously injured or killed yourself by your prey item. This risk would have only been more paramount in the Jurassic as Sara and others of her kind were preying on plant eating dinosaurs. We only have to look at the fossils of plant eating dinosaurs from the same rock layers Sara was found in (the famous dinosaur-rich Morrison Formation) to see what she would be up against. There were various types of huge long necked sauropod dinosaurs, who's immense size alone would present a challenge. There were also heavily armoured dinosaurs like the famous Stegosaurus present. These creatures were armed with a spiky tail which would have been a formidable deterrent against predators. I'd like to think Sara got her injuries due to a failed attack on a Stegosaurus, it could explain the rather odd circular pathology on Sara's left coracoid bone, which might have originated from a strike from one of the spikes of a Stegosaur's tail. Such an epic fight is hard to imagine, so I recommend you check out the link below (if it still works) to better picture this awesome clash of titans:

https://www.youtube.com/watch?v=TaComRFcRTc&t=28s

2) Sara was injured fighting others of her kind

The fact that scientists believe Ceratosaurus would have hunted in packs, would bring Sara into direct competition with other larger, more aggressive animals. Being a sub-adult and not yet fully grown would see Sara at the bottom of the pecking order when it came to who got first dibs after a kill. Its quite likely too that Sara sustained her injuries from fighting for her 'place at the dinner table' (below left)(Editors of Publications International, Ltd. 2008).

Whatever the reason of Sara's unfortunate demise, we can be thankful to the process of fossilisation, which was able to preserve her original skeleton in exquisite detail. It is this which greatly aids our understanding in trying to piece together the story of this particular Ceratosaurus some 150 million years later. I hope you have enjoyed this particularly long blog entry which now should equip you with some basic observations a paleontologist would employ. With this in your toolset, you will never quite see fossils in the same light again.

Regards

Matthew Staitis.