New dinosaur competes to be Europe’s largest ever land predator

This was originally posted at: https://theconversation.com/new-dinosaur-competes-to-be-europes-largest-land-predator-23997

Say hello to Torvosaurus gurneyi, the newly discovered theropod dinosaur that lived in Europe around 157-145 million years ago. It is potentially the largest land predator discovered in Europe and one of the largest carnivorous dinosaurs from the late Jurassic period. The identification of this new species plays an important role in developing our understanding of how different dinosaur species were distributed across the globe, as well as the ecology of large European predators at this time.

Similar in appearance to the North American species Torvosaurus tanneri, the remains found in Portugal were initially regarded as near-identical to them. But closer scrutiny and greater knowledge of the anatomy of theropod dinosaurs has led to several key features being identified in the new species.

Key differences

Although the remains assigned to T. gurneyi are quite fragmentary – usually not enough to confidently announce an entirely new species – the cheek bones of theropods have a strong track record of identifying new species. In this regard, T. gurneyi has three features that distinguish it from its sister, T. tanneri. While these have been classified as sufficient to distinguish a new species, it is likely that there will be a few eyebrows raised from other palaeontologists about the strength of this diagnosis.

One of the most important of these features is the number of teeth. T. tanneri is known to have had up to 12 teeth, whereas T. gurneyi only had a maximum of ten, according to the number of holes preserved where the teeth would have fitted into the bone. The number of cheek teeth can vary as a dinosaur grows up, however, and can even change between the maxillae of the same animal. This means that a third of the diagnosis of this new species is questionable. One explanation is that it could be a specimen that died before coming of age.

Christophe Hendrickx, the lead author of this new study, remarked: “I highly doubt that an estimated 10 metre Torvosaurus with a 60 centimetre maxilla (cheek bone) could be an immature individual”. He is, of course, correct.

The evolutionary evidence for differentiating two species of Torvosaurus is also weak. The Bremer support value – a method of identifying how stable the relationships between species are – is very low. This means that the observational and statistical support for identifying these remains as a new species is rather weak, based on the material currently known. What is clear, however, is that it undoubtedly represents a specimen of Torvosaurus, and is geographically distinct from its North American cousins.

Biogeographical implications

Many links between the animal life of the Iberian Peninsula and North America during the Late Jurassic period have been known with fossils of similar species found on each. Shared species include allosaurs, stegosaurs, and the giant sauropods, all of which may have close cousins in Tanzania too. The implication is that there were exchanges of species between the two areas, despite thousands of kilometres of the Atlantic Ocean’s precursor separating them.

The Portuguese specimens are geologically older than the North American ones and it is possible that they made the journey across on temporary bridges of land, created during a period of relatively low sea-level around 163.5 million years ago. With the discovery of this new Torvosaurus gurneyi species in Portugal, there is more evidence for this theory.

Predator among predators

The Late Jurassic of Portugal must have been a quite terrifying place to live, no matter which species you happened to belong to. No less than four super-predator theropods are now known to have lived alongside each other there: Allosaurus, Ceratosaurus, Lourinhanosaurus and now Torvosaurus gurneyi.

Torvosaurus may have been the largest of all these fearsome beasts, but the material is quite incomplete. This assertion may not hold if more complete specimens are found. But, if estimations from these remains are correct, with a skull more than a metre long, it would have been comparable in size to giant Cretaceous period super-predators like the Gorgosaurus and Tarbosaurus.

Exactly how all these large predators co-existed with one another is another matter. As Hendrickx said to me: “Only time, with the discovery of new material of Torvosaurus from Portugal and the US, will give an answer to these questions.”

If you’d like to no more, see the tweets of Thomas Holtz and Steve Brusatte, two mega dinosaur experts, from the last couple of days. Well worth it – science can happen in real time online! 🙂