A new, virtually complete, specimen of the enigmatic theropod Deinocheirus mirificus, discovered in the Nemegt Basin of the Gobi Desert in Mongolia looks set to shake the world of theropod phylogenetics to the core. This specimen of Deinocheirus was recovered from Upper Cretaceous deposits not too far from where the original specimen was found at Altan Ula III and provides undisputed evidence that this animal represents a new gigantic sized coelurosaurian clade.
The specimen is currently being described and will be officially published later this year in the Proceedings of Earth Sciences – this current press release appears to be a taster of what is to come and is typical of some of today’s fast moving media-driven palaeoresearch.
“This has completely surprised us and we could hardly believe our eyes as the skeleton slowly emerged from the rock. A complete specimen of Deinocheirus is a palaeontologist’s dream and to find it so close to the quarry where the holotype was found is rather fitting.” said palaeontologist Dr. Pol T’Othewan, leader of the excavation and research team at the Nemegt Basin Research Centre (NBRC) in Dalanzadgad, Ömnögovi Aimag in Mongolia.
Deinocheirus is most famously known because of its huge forelimbs which are around 8 feet long. Although clearly a theropod dinosaur, the phylogenetic affinities of Deinocheirus have long been debated and the animal has been tentatively assigned as a megalosauroid, coelurosaur or, indeed, something in between the two. The most recent phylogenetic analyses return Deinocheirus as a basal ornithomimosaur but this new specimen looks set to confound the experts.
“When Deinocheirus was originally discovered it was thought that because the forelimbs were so big that the rest of the animal could not possibly be of the same stature otherwise its size would defy imagination – they were wrong” said co-worker and palaeontologist Gotya Sukker – also of the NBRC. “What we have now appears to represent an offshoot coelurosaurian clade displaying both primitive and derived characters and that Deinocheiridae is, indeed, a very distinct family. The size of the animal is astonishing and the skull alone makes the skull of Tarbosaurus look maniraptoran in comparison.”
The specimen, which appears to be a fully mature individual, was found in the sandstones of the Upper Nemegt Beds and, despite being largely disarticulated, is essentially all there and appears to have suffered very little erosion which suggests that it had only been recently exposed at the surface before being discovered. The specimen was immediately identified as Deinocheirus, whose name means “terrible hand”, when the enormous forelimbs were excavated.
“Close examination has revealed several characters that are totally unknown in other dinosaurs – let alone other theropods. Certainly there is extensive remodelling in the vertebral column and a degree of pneumaticism only previously seen in sauropods and the hind limbs are incredibly long and strong” said another member of the team, Luke Anyulsee, of the University of Kehlsdorf in Austria.
Deinocheirus has always been an enigma in dinosaurian palaeontology but this skeleton, because of its completeness, will give us new insights into coelurosaurian evolution and has significant ramifications for dinosaurian phylogenetics as a whole.
“It has generally been accepted for some time that Deinocheirus was probably an over-sized ornithomimosaur with similar habits and lifestyle to its smaller cousins” Sukker said. “This specimen shows that, despite displaying ornithomimids traits in some parts of the skeleton, it was obviously something completely different. The skull is enormous – far bigger than any previously known theropod skull and the dentition is frightening. Deinocheirus would have unquestionably been the hyper-carnivore of its time”.
Adult tyrannosaurs too, by comparison, were enormous animals and Tyrannosaurus was around 40 feet long with a skull approaching 5 feet long. Spinosaurus, despite being poorly known, is estimated to be around 50 feet long. When asked how they compare with Deinocheirus, T’Othewan is remarkably blunt in his response.
“They don’t – there is no comparison. Deinocheirus would have them sliced and diced and ready for breakfast before they knew it. This is now THE mega-theropod of the Mesozoic.”
This research is being funded by the Avril Tromper Foundation in Paris.