Anzu wyliei – Probably Feathered and an Omnivore from the very end of the Cretaceous
With the publication of the scientific paper on the newest member of the very bird like Oviraptorosauria published this week in the on line journal PLoS One (Public Library of Science), team members at Everything Dinosaur attempt to put the discovery of the “chicken from Hell” into context. The dinosaur has been named Anzu wyliei and this genus has been erected based on the fossils of three individual dinosaurs discovered in Upper Cretaceous deposits of North and South Dakota (United States). The fossil sites are around fifty kilometres apart and they represent a dinosaur, whose presence in the Hell Creek Formation (Maastrichtian faunal stage) had long been suspected but these fossils provide definitive proof that such creatures roamed the western United States at the end of the Cretaceous.
Most discoveries of oviraptorosaurs have been made in Asia, most notably in China and Mongolia. Much of what has been inferred about A. wyliei has been based on comparisons with Asian Oviraptors, even though the remains of the three individuals when combined together represent about 80% of the total skeleton. For example, Anzu wyliei has been pictured as a feathered dinosaur, although no fossilised feathers have been associated with the Hell Creek Formation specimens. The covering of a shaggy coat of feathers is inferred, as a result of Asian specimens preserved in finer grained matrices which have permitted feather preservation. The discovery of skull material, including a hyper extended premaxilla indicates that this dinosaur had a large rounded crest on the top of its skull. This feature is common to a number of Oviraptor genera.
An Illustration of Anzu wyliei
Picture credit: PLoS One/Everything Dinosaur
The picture above gives an overall impression of what this new dinosaur species looked like. The post cranial bones coloured grey represent fossil specimens. The skull material indicated represents the extent of the fossil material found to date. The Oviraptorosauria can be split into a number of families, one such family is the Caenagnathidae (the name means “recent jaws” – as the group were originally thought to be a Cretaceous clade of birds). The jaws are very bird-like and these dinosaurs had no teeth. Intriguingly, compared to other North American members of the Caenagnathidae such as Chirostenotes spp. known from older rocks found in Alberta, Canada (Campanian faunal stage), Anzu wyliei was a real bruiser! Body mass estimates based on femur (thigh bone) measurements suggest that this dinosaur weighed between 200 and 300 kilogrammes and that it probably stood around 1.5 metres high at the shoulder and had an overall length approaching 3.5 metres. Some of the Canadian caenagnathines were probably only around 20 kilogrammes in weight when fully grown.
The Reconstructed Skull of Anzu wyliei
Picture credit: Donald E. Hurlbert (Smithsonian Institute)
The American scientists from Utah University, the Smithsonian Institute and the Carnegie Museum of Natural History re-examined the fossil material that had been collected a few years earlier. Their research helps palaeontologists to piece together a little more about the other types of dinosaur that shared the same environment with more famous dinosaurs like Triceratops and Tyrannosaurus rex.
Phylogenetic analysis suggests that this new species of dinosaur was most closely related to Caenagnathus collinsi (known from Campanian-aged strata from Alberta, Canada). The fossils have also suggested that A. wyliei and other caenagnathines may have preferred open expanses such as floodplains, as to what they might have been eating way back at the end of the Cretaceous, these animals were probably generalist omnivores. It is likely that the bulky Anzu wyliei fed on small mammals, insects, lizards, baby dinosaurs and plants. It may even have specialised in eating the eggs of other dinosaurs. Scientists have nick-named this dinosaur the “chicken from Hell” a reference to the Hell Creek Formation where the fossils were found.
An Illustration of a Typical Oviraptor
Picture credit: Everything Dinosaur
A spokes person from Everything Dinosaur commented:
“This research is extremely important as it helps to fill in the gaps in terms of the smaller, theropods that lived at the very end of the Cretaceous. These fossils represent some of the youngest Oviraptor fossils discovered to date.”