In 1998 and 1999 two skeletons were collected from the badlands of the Great Plains of South Dakota, USA. Discovered by Fred Nuss barely 80m apart, they would go on to be one of the most intriguing and strong denizens of the Hell Creek fauna.
(This article originally appeared with a different frontis. The image was borrowed, without permission, from Brian Switek’s article on a possible additional specimen, including foot bones(!) of this species, or even a potential different species. I replaced it with the image above. That image now appears below, with proper attribution and permission.)
But through the long process of preparation and consolidation (a cooperative venture between Nuss and Mike Triebold’s TPI), the bones being heavily damaged through action of roots and geology, the two skeletons eventually become a single animal, and then from there those who’d taken the painstaking task upon themselves to prepare and present the material sought to find a fair home for it. They (being Nuss and Triebold and his merry band of fossil collectors and preparators) wanted a public institution, if possible: the material appeared to represent a new species. Called Triebold’s oviraptor, or an unnamed caenagnathid, or the Hell Creek oviraptorosaur, this specimen would become famous, mounts of it cast and sent around the world. For years, the specimens were called “Triebold’s oviraptor,” “Trieboldraptor,” and even an informal nod toward Caenagnathus or Chirostenotes.
Specimens of this animal have been discovered before. A fragment of one was mixed up with Sue, the giant tyrannosaur that ended up at Chicago’s Field Museum, but it was so incomplete not much could be made of it, as little else was known of caenagnathids. But these two specimens, representing most parts of the skeleton, provided substantial information.
Those specimens ended up at the Carnegie Museum, and so began work to fully describe and relate them to the awaiting world. On Wednesday, 19 March, the specimens were crowned by the Carnegie’s Matt Lamanna, the Smithsonian’s Hans-Dieter Sues and Tyler Lyson, and by University of Utah’s Emma Schachner. Anzu wyliei, named for a Sumerian demigod which took avian form (and also incidentally a very coincidental bird “god” with enormous hand claws in the game World of Warcraft, named for the same reason) and also the Wylie Tuttle, whose grandparents had given musch support to the Carnegie Museum where the specimens now reside, meets the world.
(As an added bonus, Anzū translates as “to know heaven” and has been characterized as a gryphon-like figure, which is comparable to the second largest oviraptorosaur from North America, Hagryphus giganteus.)
It stands almost 8 feet, 5 at the shoulder and the rest head and neck. Much like an ostrich or some demented chicken-monster, Anzu like other oviraptorosaurs would have been a fully feathered, long-legged bird-like dinosaur. The head is crowned with what has been called a “dinner plate” of a crest, much like some hadrosaurs, though it doesn’t seem to be hollow, also unlike many crested oviraptorids.
An oviraptorid it is not, but a caenagnathid; and what that meant has been debatable. In the early 1920′s the Sternberg family had discovered a trove of fossils at a site in Alberta along the Red Deer River called Steveville. Specimens from this trove included fragments of this or that species. Charles Gilmore named the first of these fragments (a partial pair of hands) Chirostenotes gracilis. The Sternbergs would add a partial foot (Macrophalangia canadensis) and then a real prize: a fused pair of mandibular rami, forming nearly an entire lower jaw, Caenagnathus collinsi. Another partial jaw, Caenagnathus sternbergi, would join later, from Joel Cracraft. It would not take long before someone started speculating these would all belong to a similar type of animal. Yet even earlier a partial foot had been discovered named by William Parks: Ornithomimus elegans. I go into far more depth on this topic, why the species should stay separate, and how to treat them, here. It is refreshing that the paper helmed by Lamanna and colleagues have done much the same.
Anzu wyliei enters into this debate because it preserves features of each of these animals, and strengthens support that many of them belong, if not to the same animal then to a single grade of animal. Anzu creates the first substantial illustration of what a caenagnathid would look like. Most importantly, it expands the potential variation of jaw morphology in caenagnathids. Over the last few decades numerous partial jaws have been found in Alberta and, now, the southern US, producing a robust idea of jaw variation, which neatly fills in many gaps between the then-suggested variation shown. Small jaws from Texas, such as Leptorhynchos gaddisi, had a straight, upturned jaw, whereas the Alberta jaws varied in being upturned to slightly curved upwards. Anzu wyliei, however, has a relatively flat jaw.
The intricacies of caenagnathid jaws fascinate me, and for various reasons I’ve been looking into turtle and bird jaws to see if these morphological variations are even more interesting, or merely boring. Anything but. Anzu implies much more complexity in caenagnathids, with ridges and deep fossae and whatnot. A trove of fascination. And that’s not all preserved of the head: the upper jaw is there, and this allows comparison of the jaw to that of Epichirostenotes curriei, whose skull is known from a maxilla and fragment of palate, along with the rear of the skull, as in Anzu.
To test their idea of a caenagnathid identity, the authors undertook the most comprehensive phylogenetic analysis covering specifically oviraptorosaurs to date, on the basis of the analysis by Nick Longrich and co-authors describing Leptorhynchos gaddisi. And correcting various codings to separate the lumped in species so that holotypes and specimen complexes attached to names would be correctly evaluated without conflating assumptions of referral. Adding in new characters, the most complete set of relationships for caenagnathids has been recovered.
One of these was the recovery of the positively titanic Gigantoraptor erlianensis as a caenagnathid. I’d hypothesized this a while back, but since then new analyses have supported caenagnathid relationships, including Longrich’s analysis. Lamanna’s new matrix further supports this relationship, and I think at this point the relationship is convincing.
It should be noted that Anzu wyliei comes from the Hell Creek Formation, and was thus a contemporary of the latest nonavian dinosaurs. Tyrannosaurus rex. Triceratops prorsus. Ankylosaurus magniventris. As one of the last oviraptorosaurs, it occurs almost 10 million years after the caenagnathids of Steveville, amongst which it is nested. First, this is not surprising given that only a few species are known with relatively complete mandibles and many more, including Epichirostenotes curriei and Ojoraptorsaurus boerei, are not. But those taxa are also both older than Anzu, and younger than the Steveville taxa, which makes them important and potential intermediates. We will need more data to properly assess these taxa.
Anzu was also a contemporary of Ornithomimus elegans, referred by the authors as some do and should as Elmisaurus elegans (rather than, say, as Chirostenotes elegans, and synonymized with Chirostenotes sternbergi on account merely of gracility). There is also the tiny Lancian “parrot,” from the contemporaneous Lance Formation, but this is the subject of ongoing research. Elegans is primarily known from the Dinosaur Park Formation, which is late Campanian in age, but the Hell Creek material referred to it is morphologically very similar, but may indeed belong to Anzu. This cannot be confirmed, as the Carnegie skeletons lack metatarsal bones.
No matter the final fate of these taxa, the Hell Creek oviraptorosaur has been long due, and its arrival well received.
Anzu has come.
Cracraft, J. 1971. Caenagnathiformes: Cretaceous birds convergent in jaw mechanism to dicynodont reptiles. Journal of Paleontology 45: 805-809.
Currie, P. J. & Russell, D. A. 1988. Osteology and relationships of Chirostenotes pergracilis (Saurischia, Theropoda) from the Judith River (Oldman) Formation of Alberta, Canada. Canadian Journal of Earth Sciences – Revue canadienne de sciences de la Terre 25: 972-986.
Currie, P. J., Godfrey, S. J. & Nessov, L. A. 1994. New caenagnathid (Dinosauria: Theropoda) specimens from the Upper Cretaceous of North America and Asia. Canadian Journal of Earth Sciences – Revue canadienne de sciences de la Terre 30: 2255-2272.
Sues, H.-D. 1997. On Chirostenotes, a Late Cretaceous oviraptorosaur (Dinosauria: Theropoda) from western North America. Journal of Vertebrate Paleontology 17: 698-716.
Gilmore, C. W. 1924. A new coelurid dinosaur from the Belly River Cretaceous of Alberta. Canada Geological Survey Bulletin 38: 1-12.
Lamanna, M. C., Sues, H.-D., Schachner, E. R. & Lyson, T. R. 2014. A new large-bodied oviraptorosaurian theropod dinosaur from the Latest Cretaceous of western North America. PloS ONE 9 (3): e92022.
Longrich, N. R., Barnes, K., Clark, S. & Millar, L. 2013. Caenagnathidae from the Upper Campanian Aguja Formation of West Texas, and a revision of the Caenagnathinae. Bulletin of the Peabody Museum of Natural History 54: 23-49.
Parks, W. A. 1933. New species of dinosaurs and turtles from the Upper Cretaceous formations of Alberta. University of Toronto Studies, Geological Series 34: 1-33.
Sternberg, C. M. 1932. Two new theropod dinosaurs from the Belly River Formation of Alberta. The Canadian Field-Naturalist 46: 99-105.
Sternberg, R. M. 1940. A toothless bird from the Cretaceous of Alberta. Journal of Paleontology 14: 81-85.
Sullivan, R. M., Jasinski, S. E. & van Tomme, M. P. A. 2011. A new caenagnathid Ojoraptorsaurus boerei, n. gen., n. sp. (Dinosauria, Oviraptorosauria), from the Upper Cretaceous Ojo Alamo Formation (Naashoibito Member), San Juan Basin, New Mexico. New Mexico Museum of Natural History and Science, Bulletin 53: 418-428.