Portugal’s Giant Jurassic Predator Gets a New Name

In the annals of dinosauriana, size and apparent ferocity count a great deal towards fame. By that measure, Torvosaurus should be a household name. Described by paleontologists Peter Galton and James Jensen in 1979 from bones found in Colorado’s Dry Mesa Quarry, this long-skulled, fiendishly-clawed theropod was a bulky predator that reached over 30 feet in length and weighed more than four tons. Even among the Jurassic floodplains of prehistoric North America where the impressive Allosaurus and Ceratosaurus also roamed, Torvosaurus stood out as an especially large carnivore.

And Torvosaurus has turned up in Portugal, too. In 2000 paleontologists Octávio Mateus and Miguel Antunes wrote a brief paper on a tibia – one of the bones of the lower leg – found within Portugal’s Lourinhã Formation that was referable to the North American dinosaur. A piece of Torvosaurus jaw with two teeth inside and a smattering of other fossils soon confirmed that the huge megalosaur really is present in the strata of Portugal.

The discovery of Torvosaurus so far afield from Colorado fit an emerging pattern among other dinosaurs found within Portugal’s 157 to 145 million old rocks. Along with Torvosaurus, paleontologists also uncovered Allosaurus and Ceratosaurus within the Lourinhã Formation, adding a North American flavor to the assemblage of otherwise unique dinosaurs. Despite being separated by the burgeoning Atlantic, America’s Jurassic west and prehistoric Portugal shared a dinosaurian connection.

Initially, Mateus and other researchers identified the Lourinhã Formation Torvosaurus bones as representative of the species found in North America – Torvosaurus tanneri. But now Christophe Hendrickx and Mateus have published a new assessment which proposes that the Lourinhã Formation’s Torvosaurus belongs to a new species.

Named Torvosaurus gurneyi in honor of Dinotopia artist James Gurney, the dinosaur is distinguished from its close North American relative on the basis of three anatomical characteristics. And to see those, you have to look Torvosaurus in the mouth. Using a maxilla – or the major bone of the upper jaw – as a guide, Hendrickx and Mateus note that Torvosaurus gurneyi is different in having fewer than 11 teeth in the maxilla, relatively short and blunt nubs (called interdental plates) between the teeth, and lacking a landmark called the protuberant ridge. Together, the characteristic maxilla and a broken piece of tail bone are the prime representatives of the new species.

There are other bits and pieces of Torvosaurus gurneyi. In addition to the tibia that put paleontologists on the trail of this dinosaur, Hendrickx and Mateus add another maxilla, a tooth, a piece of femur, remains of embryos, and even possible Torvosaurus tracks to the list of fossils potentially referable to the species. But even with this smattering of skeletal evidence, the question remains whether or not the Lourinhã Formation’s Torvosaurus should be split as a new species.

[A Torvosaurus gurneyi stalks sauropods in Dinosaur Revolution.]

Tooth count and interdental plates can differ between individuals and with age – something Hendrickx and Mateus note in their analysis – so these characteristics alone may not provide strong support for establishing a new species without a large sample size. And even though there are other fossils that might be attributable to Torvosaurus, additional and more complete specimens of the theropod are needed to puzzle out the identity and meaning of these clues. That’s going to take a lot more time spent in the field and scouring old collections. For reasons not yet understood, Torvosaurus is rare is Late Jurassic deposits – Allosaurus is much more abundant, and even the elusive Ceratosaurus is known from more complete skeletons.

Settling the dinosaur’s name is only an initial step, though. There’s still a great deal paleontologists don’t know about the natural history and evolution of Torvosaurus, including just how big the dinosaur grew to be. Hendrickx and Mateus estimate that the Torvosaurus gurneyi maxilla would have measured about two feet, which they extrapolate to an individual almost 33 feet long. That’s comparable to estimates for the North American species, although a lack of truly complete specimens means that even those numbers are up for revision. How long dinosaur tails actually were, for example, can significantly alter size estimates.

But a bigger mystery is how Torvosaurus – as well as neighbors Allosaurus and Ceratosaurus – wound up on both sides of the early Atlantic. That seaway had been spreading for tens of millions of years prior to the origin of these dinosaurs, and there’s no reason to believe that the dinosaurs of Jurassic North America and Portugal underwent such focused parallel evolution as to produce the same genera twice. And while getting between continents by clinging to rafts of vegetation may have worked for lemurs much later in geologic time, there’s no evidence to suggest that infant theropods did the same.

Instead, Mateus and others have suggested that an episode of continental uplift created temporary landbridges between Jurassic North America and the proto-Iberian Peninsula sometime around 163.5 million years ago. These corridors, if they stuck around long enough after the origin of Torvosaurus and contemporaries, could have allowed wide-ranging predatory dinosaurs to cross before the sea reclaimed the lost ground and the dinosaur populations became stranded on either side. Isolation is one prerequisite for evolutionary change, so the Torvosaurus of the Lourinhã Formation could have had enough time to accrue changes that differentiated them from the Morrison Formation species. To resolve this question, and many others, paleontologists will have to keep revisiting the past. Torvosaurus was big, scary, and rare, but we are really just getting to know this Jurassic ripper.

References:

Hendrickx, C., Mateus, O. 2014. Torvosaurus gurneyi n. sp., the largest terrestiral predator from Europe, and a proposed terminology of the maxilla anatomy in nonavian theropodsTorvosaurus gurneyi n. sp., the largest terrestiral predator from Europe, and a proposed terminology of the maxilla anatomy in nonavian theropods. PLoS One. 9, 3: e88905. doi: 10.1371/jounral.pone.0088905.

Mateus, O., Walen, A., Antunes, M. 2006. The large theropod fauna of the Lourinhã Formation (Portugal) and its similarity to the Morrison Formation, with a description of a new species of Allosaurushe large theropod fauna of the Lourinhã Formation (Portugal) and its similarity to the Morrison Formation, with a description of a new species of Allosaurus. New Mexico Museum of Natural History and Science Bulletin. 36: 223-232.