By Hans-Dieter Sues, Curator of Vertebrate Paleontology
To date, paleontologists have identified and named well over 1,000 species of dinosaurs (not including birds) from rocks ranging in age from about 230 to about 66 million years before present. Even using conservative estimates, this represents only a fraction of the total number of dinosaur species that ever lived. New dinosaurs are still being discovered around the word on an almost monthly basis. A few countries, especially China, Mongolia, and Argentina, are “hotspots” for finding new species. However, many discoveries of new dinosaurs have been made here in the United States in recent years.
Today my colleagues and I published the first report on a new species of North American dinosaur, Anzu wyliei, in the open-access scientific periodical PLOS ONE. A quick look reveals our new animal to be amazing in appearance even by dinosaurian standards. Imagine a cassowary, a crested bird that looks like an emu, crossed with a reptile – a head with the toothless beak and surmounted by a tall, thin crest, long feathered arms ending in huge claws, long, powerful hind legs, and a long tail ending in a fan of feathers. The composite skeleton now on display in Pittsburgh at the Carnegie Museum of Natural History is about 11 feet long and stands about five feet at the hip.
One of the frustrating aspects of fossils is that most of them are incomplete, and dinosaurs are no exception. Few species are known from more than a single skeleton, and finding even one nearly-complete or even partial skeleton is already a very lucky break. Historically, many species were named on the basis of a single bone or tooth. We know about Anzu because of the discovery of several partial specimens made over the course of more than two decades.
The sedimentary rocks of the Hell Creek Formation in the Dakotas and Montana are from the end of the Cretaceous Period, about 68 to 66 million years before present. They are famous for their dinosaurs, including the famous Tyrannosaurus rex and Triceratops. There are also other large-bodied dinosaurs such as the duckbilled dinosaur Edmontosaurus and the dinosaurian “dreadnought” Ankylosaurus. In addition, researchers have found bones and teeth of smaller dinosaurs ever since exploration of the Hell Creek fossil beds began in the late nineteenth century.
Starting with a pair of disembodied hands reported by the Smithsonian’s legendary dinosaur expert Charles Whitney Gilmore in 1924, paleontologists kept finding isolated bones or sets of bones of smaller predatory dinosaurs in Cretaceous-age rocks in the West and the prairie provinces of Canada. In 1940 a Canadian paleontologist described a large toothless mandible from Alberta. He named it Caenagnathus and assigned it to a new group of Mesozoic birds. Former Smithsonian Secretary Alexander Wetmore, the leading expert on living and fossil birds in his day, questioned that identification but had no evidence to support a different interpretation. In 1976, a Polish dinosaur expert noticed close similarities between the lower jaws of Caenagnathus and those of Oviraptoridae, a group of predatory dinosaurs with strange, parrot-like heads known only from Mongolia and China. Two later discoveries of partial skeletons of Caenagnathus-like dinosaurs from Alberta further confirmed this relationship but did not substantially improve our understanding of these mysterious dinosaurs. One of those skeletons had already been collected in 1923 but I was the first person to identify and report this fossil, which had languished in its plaster jacket at the Royal Ontario Museum in Toronto since its collection.
In the 1990s private collectors found and excavated two partial skeletons of a rather large, bird-like dinosaur from rocks of the Hell Creek Formation at a site in Harding County, South Dakota. They recognized that these finds represented a species new to science and offered them for sale to museums. Eager for new attractions to spruce up the section on Cretaceous dinosaurs in its dinosaur gallery, Carnegie Museum of Natural History (Pittsburgh) acquired them.
Given my interest in Caenagnathus-like dinosaurs from North America and Asia, my friend Matt Lamanna, curator of dinosaurs at Carnegie, invited me to join him in the study of the two skeletons. As we started the project we learned that two graduate students, Tyler Lyson and Emma Schachner, were studying the bones of a third, less complete skeleton of a Caenagnathus-like dinosaur that a team led by Tyler had found in North Dakota. The four of us decided to pool our specimens, which all turned out to belong to the same new species. (Tyler is now a postdoctoral fellow in Vertebrate Zoology at the National Museum of Natural History, making collaboration a lot easier.) An illustration of the composite skeleton is shown below.
The scientific name Anzu wyliei was chosen to underscore its bizarre appearance and the presence of feathers (inferred from related dinosaurs). Anzu is a winged monster or minor deity in various Mesopotamian mythologies, and Wylie is the name of the dinosaur-obsessed grandson of two generous supporters of the Carnegie Museum.
The function of the large hand claws is not clear. Perhaps they were used for grasping objects or even for defense. The long, powerful hind legs indicate that Anzu was an excellent runner, much like present-day emus and ostriches. The diet of the new dinosaur remains a bit of mystery because the jaws were covered by a beak and lacked teeth. The structure of the jaw joint indicates that Anzu could move its mandible back and forth. This jaw motion would have facilitated cutting food between the upper and lower halves of the beak. Based on the combination of features in the skeleton, we surmised that Anzu was possibly an omnivore. Perhaps future finds will bring a more definite answer.
The next step in our research is a detailed anatomical description and analysis of the skeleton of the new dinosaur, which will help us in answering questions about its biology and its ecological role in the Hell Creek ecosystem. We recently learned of the existence of unreported bones of Anzu in several museum collections, which will further increase our study sample. Working with a Russian colleague, I am now also studying bones of a geologically somewhat older, smaller relative of Anzu that a team I co-directed collected in Central Asia between 1997 and 2006.
The discovery of Anzu shows that continued exploration in long-studied rocks close to home (and in museum collections!) can still yield phenomenal discoveries. Nearly two hundred years since the first scientific description of a dinosaur, we still have so much to learn about these fascinating creatures and the worlds they inhabited and shaped.
Read the paper by Matthew C. Lamanna, Hans-Dieter Sues, Emma R. Schachner, and Tyler R. Lyson in PLOS ONE.