Paleo Profiles: Gojirasaurus

A hypothetical reconstruction of Gojirasaurus. From © Nobu Tamura, spinops.blogspot.com, 01/01/2008

This week, as of writing, the new trailer for Godzilla: King of Monsters was released so I thought it would be interesting to look at a dinosaur named after the 'King of Dinosaurs'. The Gojirasaurus was one of the first truly large carnivorous dinosaurs, but it may not actually be a real dinosaur at all. 

Discovery and Fossils

A common occurrence in palaeontology is that fossils are often found but are left years, sometimes decades, before being examined. The same happened with Gojirasaurus. This dinosaur was originally named by Adrian Hunt in 1994 as he looked at some fossils from the Triassic naming the animal 'Revueltoraptor lucasi'. However, as this name was coined in his dissertation based on flimsy remains this classification was deemed a nomen nudum. A nomen nudum is used to describe a scientific name given to an organism that hasn't been formally published, and therefore, reviewed by other experts. In 1997 Kenneth Carpenter formally described the bones giving them the name Gojirasaurus quayi - 'Gojira lizard from Quay'. As you can tell Gojirasaurus got its name from the iconic movie dinosaur Godzilla - as a side-note Gojira means 'Gorilla whale' referencing the monster's original design of gorilla-whale hybrid. Gojira is a portmanteau of the Japanese words for gorilla, gorira, and whale, kujira. 

Gojirasaurus is only known from a few poorly preserved bones. Bones only preserve in optimal conditions, including soil acidity and the type of soil, so not all fossils are known from well-preserved remains. With Gojirasaurus we only have a handful of bones and they are not well-preserved to boot. What we know of Gojirasaurus comes from a mix of disarticulated bones, a tooth, four dorsal vertebrae, a pubis, a tibia, a scapula (shoulder bone), ribs, and a chevron (tail bone). It was enough to formally name the animal, and create a holotype and reconstructions. In 2007 a small group of palaeontologists, (Sterling Nesbitt, Randall Irmis and William Parker), decided to look at early carnivorous dinosaur remains and found issues with the Gojirasaurus bones. Here we need to bring in the pseudosuchians; this is a clade closely related to the dinosaurs which consists of modern crocodilians and their extinct relatives. During the Triassic the pseudosuchians were an incredibly diverse group, far more diverse than the dinosaurs. Steve Brusatte's research has shown that for the 30 million years that the two groups co-existed during the Triassic the pseudosuchians overshadowed the dinosaurs. It has been said that several pseudosuchians resembled dinosaurs, like Effagia, but it is more accurate to say that the dinosaurs resembled the pseudosuchians! Analysis of Gojirasaurus' bones found not all of them came from a dinosaur - the vertebrae were found to likely be from a pseudosuchian called Shuvosaurus. Even with well-preserved bones it can be difficult to classify dinosaurs never mind poorly preserved remains. Furthermore, the tibia resembled that of a different dinosaur called Coelophysis. These similarities had long before been used to classify the Gojirasaurus as a coelophysid. The paper was reluctant to classify Gojirasaurus as Coelophysis as the tibia was so much more robust compared to that of Coelophysis. Hence, Gojirasaurus has been declared a dubious genus. For the rest of this post we'll treat Gojirasaurus as a separate genus for the sake of simplicity, but we'll bring in Coelophysis biology to better understand the dubious dinosaur.

Biology

The size of Gojirasaurus, from prehistoric-wildlife.com

One thing that can be certain about Gojirasaurus is that it was a large predator. One thing unifying palaeontologists is that Carpenter's description of the dinosaur's size is correct - it was between 5.5 to 6 metres long. In comparison the Coelophysis bauri, the most common coelophysid from North America and a possible contemporary, was only 3 metres long. It was fitting it got the name Gojira - it was a true giant during the Triassic. During the Late Triassic the dinosaurs started getting big - ancestors to the sauropods (including Brachiosaurus and Diplodocus) like the Plateosaurus could grow to 9 metres (30 foot) in length. Why the dinosaurs came to replace the pseudosuchians we don't have a clear idea yet, but their increase in size could be due to the dinosaurs evolving to fill a vacuum left by them. Gojirasaurus, like all coelophysids, were theropods - a bipedal group of dinosaurs which would include Velociraptor, Tyrannosaurus, and modern birds. Theropods would become a diverse group evolving to fill many environmental niches, but at this early stage most had fairly similar adaptations. This included diet and Gojirasaurus had serrated teeth indicating that it was a carnivore. Coelophysids were uniformly lightly built with long, slender tails; fairly long arms; and a long neck. It is fairly likely that Gojirasaurus was also built this way, especially if it turns out to be a species of Coelophysis.

Although now inaccurate the body of Coelophysis from Walking with Dinosaurs would resemble what Gojirasaurus looked like

Now we're getting into more hypothetical territory. In the past palaeontologists just expected to find bones but over the last twenty years, mostly thanks to the discovery of feathered dinosaurs, palaeontologists have been increasingly on the look out for other features. Gojirasaurus may have had a crest - later coelophysids, like Jurassic Park's Dilophosaurus, had crests and some species of Coelophysis had very small crests. We cannot be certain if Gojirasaurus had a crest - especially as we are still unsure if Gojirasaurus is a valid genus. These crests would be used for display so were likely very brightly coloured to attract a mate, or intimidate a rival. There is a chance that Gojirasaurus, and Coelophysis, were feathered; albeit these 'feathers' would be far more basic compared to the feathers of modern birds. It could even be considered more like fluff than 'true' feathers. Increasingly palaeontologists have highlighted how more and more species of dinosaurs were in fact feathered, however, Gojirasaurus was a very early dinosaur. Feathers and feathering have, so-far, only been found on dinosaurs from the Jurassic and Cretaceous, not the Triassic. Feathers had to come from somewhere, but when did somewhere start? As Gojirasaurus lived at the end of the Triassic it likely had a very basic proto-feathering. 

When and Where

A map of Pangea with modern continents 

Gojirasaurus lived 210 million years ago, Coelophysis from 221 to 196 million years ago, during the first period of the Mesozoic era called the Triassic. Dinosaurs appeared sometime between 243 and 233 million years ago making Gojirasaurus one of the first dinosaurs. The fossils were found in the Cooper Canyon Formation in New Mexico - the southern US (especially New Mexico and Texas) is particularly good for Triassic fossils. The New Mexico of the Triassic was very different from the New Mexico of today. Instead of the deserts we would instead find well-watered forests full of conifers occasionally subject to flooding - at Ghost Ranch in New Mexico around 1,000 almost Coelophysis were caught in a flash flood leaving their remains perfectly preserved. The world of the Triassic that Gojirasaurus called home was very different to our world. There was just one continent, a supercontinent, called Pangea and one giant ocean, Panthalassa. Steve Brusatte has described the climate as living in a 'sauna'. More carbon dioxide in the atmosphere caused higher temperatures, something we're experiencing now thanks to human caused climate change, which was exacerbated by the planet's geography. Air currents moved unimpeded from equator to pole as there was just one continent making the poles extremely warm - the poles had the same temperature as modern London or San Francisco. Intense monsoons, called megamonsoons, were created thanks to a scorching land which were so large that they could provincialise the environment. Vast stretches of desert (which had temperatures exceeding 35 degrees Celsius) were divided from hot and humid equatorial regions. New Mexico lay on the equator creating the hot and humid environment that Gojirasaurus existed in.

Gojirasaurus' New Mexico

What would become north Mexico and the southern US would create a vibrant habitat for Late Triassic animals. As we only have these scatty remains of Gojirasaurus it is possible that it was a rare animal - very large carnivores are generally rarer compared to smaller ones due to increased competition. With its large size Gojirasaurus would have been near the top of the food chain, although it would have had to fight to be at the top. The Postosuchus, a large crocodilian cousin which you might recognise from Walking with Dinosaurs, could potentially rival Gojirasaurus as the animal at the top of the food chain. The warm climate created a perfect environment for diverse plants to evolve which in turn allows a diverse range of herbivores to prey upon. Herbivorous early dinosaurs and other reptiles were potential food for the Gojirasaurus although some could fight back. The Desmatosuchus was a very large and armoured reptile with spikes on its side which would leave it protected from predators. We know very little on how social dinosaurs were so we don't know if Gojirasaurus was a pack hunter - it was once believed that Coelophysis flocked together but we now know that they were actually victims of a flash flood. Judging how birds and many reptiles, including crocodiles, care for their young we can imagine that so did Gojirasaurus and other coelophysids. 

Thank you for reading. The sources I have used are as follows:

-Gregory S. Paul, The Princeton Field Guide to Dinosaurs, Second Edition, (Princeton, NJ: Princeton University Press, 2016)

-Steve Brusatte, The Rise and the Fall of the Dinosaurs: The Untold Story of a Lost World, (London: Macmillan, 2018)

-'Gojirasaurus', Prehistoric-Wildlife.com, (Accessed 13/12/2018)

-Kenneth Carpenter, 'A Giant Coelophysoid (Ceratosauria) Theropod from the Upper Triassic of New Mexico, USA', Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen, 205:2, (1997), 189-208

-Sterling J. Nesbitt , Randall B. Irmis & William G. Parker, 'A critical re‐evaluation of the Late Triassic dinosaur taxa of North America', Journal of Systematic Palaeontology, 5:2, (2010), 209-243

-Robert Sullivan and Spencer Lucas, 'Eucoelophysis baldwini, a New Theropod Dinosaur from the Upper Triassic of New Mexico, and the Status of the Original Types of Coelophysis', Journal of Vertebrate Paleontology, 19:1, (1999), 81-90

-'Coelophysis', Prehistoric-Wildlife.com, (Accessed 13/12/2018)

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