The authors have declared that no competing interests exist.
Conceived and designed the experiments: MCL H-DS ERS TRL. Performed the experiments: MCL H-DS ERS TRL. Analyzed the data: MCL H-DS ERS TRL. Wrote the paper: MCL H-DS ERS TRL.
The oviraptorosaurian theropod dinosaur clade Caenagnathidae has long been enigmatic due to the incomplete nature of nearly all described fossils. Here we describe
Oviraptorosauria is a clade of maniraptoran theropod dinosaurs with peculiar craniomandibular specializations
Most discoveries of oviraptorosaurs have been made in Asia, principally Mongolia and China, and as a result, the balance of our knowledge of the group is derived from fossils found on that continent. Most Late Cretaceous oviraptorosaurs from Asia comprise a clade, Oviraptoridae, which may have been endemic to that landmass. Nevertheless, theropods now recognized as oviraptorosaurs have long been known from North America as well
Here we describe a new, large-bodied (total length ∼3.5 m) oviraptorosaurian taxon based primarily on three well-preserved partial skeletons from the late Maastrichtian of North and South Dakota (
Localities that have yielded specimens of
Two of the specimens described in this paper (CM 78000, CM 78001) are permanently reposited in the collections of the Section of Vertebrate Paleontology at Carnegie Museum of Natural History, 4400 Forbes Avenue, Pittsburgh, Pennsylvania, United States of America. The third specimen (MRF 319) is permanently reposited in the collections of the Marmarth Research Foundation, 402 South Main Street, Marmarth, North Dakota, United States of America. The latter organization was formally certified under Section 501(c)(3) of the United States Internal Revenue Code for the explicit purposes of research and curation of fossils from exposures of the Hell Creek Formation in southwestern North Dakota and neighboring regions. The fossils currently in the trust of the collection are intended for the establishment of a museum in the town of Marmarth, and are presently housed and curated in a dedicated facility in that town. Qualified researchers who wish to access this collection should direct such requests to the fourth author (T.R.L.) or to Ms. Barbara Benty (
Detailed locality information for the CM specimens is on file in the Section of Vertebrate Paleontology at Carnegie Museum of Natural History and is available to qualified researchers upon request; that for MRF 319 is on file at the Marmarth Research Foundation and is available to qualified researchers upon request. No permits were required for the described study, which complied with all relevant regulations. All specimens were collected from privately-owned land in the United States of America with the written consent of the respective landowners.
BHM, Black Hills Institute of Geological Research, Hill City, South Dakota, United States of America; CM, Carnegie Museum of Natural History, Pittsburgh, Pennsylvania, United States of America; CMN, Canadian Museum of Nature, Ottawa, Ontario, Canada; FMNH, Field Museum of Natural History, Chicago, Illinois, United States of America; MOR, Museum of the Rockies, Bozeman, Montana, United States of America; MRF, Marmarth Research Foundation, Marmarth, North Dakota, United States of America; TMP, Royal Tyrrell Museum of Palaeontology, Drumheller, Alberta, Canada.
The electronic edition of this article conforms to the requirements of the amended International Code of Zoological Nomenclature, and hence the new names contained herein are available under that Code from the electronic edition of this article. This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information viewed through any standard web browser by appending the LSID to the prefix “
Theropoda Marsh 1881
Oviraptorosauria Barsbold 1976
Caenagnathidae Sternberg 1940
urn:lsid:zoobank.org:act:B4E094D2-8081-452E-8976-DB96DA97308D
Anzu wyliei sp. nov.
urn:lsid:zoobank.org:act:E164FB53-289F-4B0E-916C-C581F2DE57A4
CM 78000, a disarticulated but closely associated partial skeleton that includes premaxilla fragments, the incomplete braincase, both quadrates and pterygoids, additional cranial fragments, the nearly complete but disarticulated mandible, multiple cervical and caudal vertebrae, numerous cervical and dorsal ribs, gastralia, and hemal arches, both scapulocoracoids, the right humerus, the left radius, ulna, and metacarpal II, several manual phalanges including unguals, both femora, tibiae, fibulae, astragalocalcanea, and first metatarsals, the incomplete left metatarsal V, and several pedal phalanges including unguals (
(
(
(
CM 78001, a mostly disarticulated but closely associated partial skeleton that includes the nearly complete left and fragmentary right premaxillae, maxillae, and jugals, the articulated braincase, quadrates, and pterygoids, the right ectopterygoid, additional cranial fragments, all cervical and dorsal vertebrae, the incomplete sacrum, several caudal vertebrae, numerous dorsal ribs, gastralia, and hemal arches, both sternal plates, ilia, pubes, ischia, femora, tibiae, fibulae, and astragalocalcanea, the left metatarsal V, and several pedal phalanges including unguals (
(
The genus name is for Anzu, a feathered demon in ancient Mesopotamian (Sumerian and Akkadian) mythology, and alludes to the distinctive appearance of this large, presumably feathered dinosaur. The species name is for Mr. Wylie J. Tuttle, grandson of Mr. and Mrs. Lee B. Foster, in recognition of Mr. and Mrs. Foster's generous support of the scientific research and collections activities at Carnegie Museum of Natural History.
Harding County, South Dakota, United States of America (CM 78000, CM 78001 [skeletons separated by only ∼100 m]; FMNH PR 2296); Slope County, North Dakota, United States of America (MRF 319) (
The holotype of
CM 78001 comes from a site approximately 100 m east of the type locality, and from a stratigraphic level of the Hell Creek Formation that is approximately 3.5 m lower in section. The specimen was recovered from a calcite-cemented, medium yellow-brown silty mudstone with abundant organic matter that is interpreted to represent a low-energy, floodplain depositional environment adjacent to a swampy area, as indicated by an overlying coal seam. Elements of CM 78001 were found in close association with some articulation. The specimen was eroding from a low, vegetated knob, and as such, many of its bones exhibit damage from weathering and invasion by plant roots. Like that of CM 78000, the CM 78001 site displayed several normal faults with minor (2–25 cm) vertical displacement. Bones that spanned these fault zones (e.g., the right femur) were broken and separated, with up to 25 cm of vertical and 30 cm of horizontal displacement, respectively (M. Triebold and W. Stein, pers. comm.).
A large concentration of organic debris and small fossils (e.g., mollusk shells, bones of small vertebrates) was recovered between the dorsal ribs and pelvis of CM 78001. This debris was much more prevalent within this region than elsewhere in the quarry (M. Triebold and W. Stein, pers. comm.). Consequently, there is some possibility that it may represent gut contents; nevertheless, because CM 78001 was mostly disarticulated, this is difficult to demonstrate with certainty. Contamination from fluvial processes is a likely alternative explanation for the presence of this material.
MRF 319 was collected from the upper one-third of the Hell Creek Formation, from an exposure on privately-owned land approximately 5 km northwest of the town of Marmarth, North Dakota. It was found in a poorly consolidated sandstone rich in clay rip-up clasts that is herein interpreted as a channel lag deposit. The specimen was associated with numerous gar scales and a single water-worn bone of an indeterminate ornithischian dinosaur.
Caenagnathid oviraptorosaur diagnosed by the following autapomorphies (characters observable in multiple specimens are denoted with an asterisk; hypothesized reversals are denoted with a dagger): (1) tall, crescentic cranial crest formed by posterodorsal processes of premaxillae*; (2) body of maxilla lacking antorbital fossa; (3) maxillary ascending process elongate and shaped like an inverted ‘L’; (4) quadratojugal process of jugal dorsoventrally deep†; (5) quadratojugal process of jugal bifurcated posteriorly†; (6) occipital condyle transversely wider than foramen magnum*†; (7) prominent lateral flange on symphyseal region of dentary; (8) elongate retroarticular process of mandible (retroarticular process subequal in anteroposterior length to quadrate articulation)*; (9) distal end of radius divided into two rounded processes*; (10) sulcus on ventromedial aspect of manual phalanx II-1; (11) tubercle on anterior surface of astragalus near base of ascending process*. Differs from hypothesized sister taxon
We assign these four oviraptorosaur specimens to
The most prominent cranial feature of
The mandibular symphysis of
The complete presacral vertebral series of CM 78001 (
The appendicular skeleton of
Pathological bones have been identified in two individuals of
We conducted a phylogenetic analysis to investigate the affinities of
We altered the descriptions of eight characters analyzed by Longrich et al.
For most taxa, we maintained Longrich et al. 's
Furthermore, in their taxonomic revision of Caenagnathidae, Longrich et al.
We then added three operational taxonomic units (OTUs) to the analysis to encompass specimens we removed from
Finally, we added ten oviraptorosaurian species to the matrix: Banji long, Caudipteryx dongi, Ganzhousaurus nankangensis, Jiangxisaurus ganzhouensis, Nankangia jiangxiensis, Ojoraptorsaurus boerei, Shixinggia oblita, Similicaudipteryx yixianensis, Wulatelong gobiensis, and Yulong mini. Five of these taxa (C. dongi, J. ganzhouensis, O. boerei, S. yixianensis, and W. gobiensis) had never, to our knowledge, been incorporated into a numerical phylogenetic analysis before (although, in the cases of J. ganzhouensis and W. gobiensis, this is likely due to the fact that known material of each has only recently been published
The complete phylogenetic data matrix is provided as Appendix S2 in
The matrix of 41 taxa (38 oviraptorosaurs) and 230 osteological characters was analyzed using TNT (Tree Analysis Using New Technology) version 1.1 (Willi Hennig Society Edition)
Numbers adjacent to each node are Bremer support values; named nodes are indicated with black dots. (
In all trees, the clade Caenagnathoidea is supported by the following synapomorphic character states: palatal shelf of maxilla with two longitudinal ridges and tooth-like ventral process (character 11, state 1); pneumatic quadrate (character 45, state 1); dentary extremely short and deep, with maximum depth 50% or more of length (character 78, state 2); mandibular articular facet for quadrate formed exclusively of articular (character 90, state 1); cervical ribs of adults loosely attached to respective vertebrae (character 104, state 0); lateral pneumatic fossae present in caudal centra, at least in anterior part of tail (character 113, state 1); arched iliac dorsal margin (character 136, state 1); mesopubic (i.e., subvertically oriented) pubis (character 145, state 1); pubic shaft concave anteriorly (character 146, state 1); anterior and greater trochanters in contact (character 150, state 1); well-developed adductor fossa and associated anteromedial crest on distal femur (character 153, state 1); ratio of maximum length of metatarsus to that of femur 0.4–0.6 (character 160, state 0); posteroventrally directed retroarticular process (character 198, state 1); and lateral ridge of femur absent or represented by faint rugosity (character 213, state 0). Caenagnathidae is supported by the following synapomorphies: preacetabular process expanded ventrally well below level of dorsal acetabular margin (character 138, state 1); lateral surface of dentary bearing deep fossa, sometimes with associated pneumatopore (character 167, state 1); and ischial peduncle of pubis with prominent medial fossa (character 201, state 1). The unnamed node comprising
In an attempt to achieve better phylogenetic resolution within Caenagnathidae, we conducted a second analytical trial that omitted all members of this clade (as recovered by our initial analysis) for which definitive mandibular material is still unknown (i.e.,
Depicted topology is the strict consensus of seven most parsimonious trees of 498 steps resulting from an analysis of 34 taxa (31 oviraptorosaurs) scored for 230 morphological characters (
In the seven trees recovered by this second trial, Caenagnathoidea is supported by most of the same character states as in the initial trial. Nevertheless, the following characters are no longer optimized as caenagnathoid synapomorphies: palatal shelf of maxilla with two longitudinal ridges and tooth-like ventral process (character 11, state 1); cervical ribs in adults loosely attached to respective vertebrae (character 104, state 0); and arched iliac dorsal margin (character 136, state 1). Caenagnathidae and
In sum, our phylogenetic results reaffirm caenagnathid monophyly (
We estimated the body mass of the holotype of
The skull of
The mode of life of caenagnathids and other oviraptorosaurs has been the subject of much speculation. The fact that the jaws of most oviraptorosaurs lack teeth and were probably covered by a keratinous rhamphotheca has frustrated attempts to infer the diets of these theropods. The earliest suggestion was that the oviraptorid
Other previous works have offered alternative dietary hypotheses for Oviraptorosauria. Barsbold
In their recent description of the well-preserved Campanian caenagnathid mandible TMP 2001.012.0012, Funston and Currie
Intriguingly, what is perhaps the most compelling evidence for oviraptorosaurian herbivory has thus far been documented only in archaic, tooth-bearing members of the clade. Several specimens of
The behavioral implications of the distinctive appendicular skeletal anatomy of Caenagnathidae have also been a topic of frequent discussion in the literature. Currie and Russell
Various authors have provided still other interpretations of the functional morphology of caenagnathid limbs. Based on the length and proportions of the hind limb, Currie
The depositional environments in which caenagnathid fossils have been found may provide additional clues to the habitat preferences of these theropods. An apparent paleoenvironmental distinction between caenagnathids and oviraptorids has long been noted
The sedimentology of the localities in the Hell Creek Formation that have yielded associated caenagnathid specimens may provide more specific insights into the types of environments that these animals frequented
To our knowledge, ichnological evidence has not yet been brought to bear on the issue of caenagnathid paleoecology; nevertheless, fossil trackways may offer additional insights into the habits of these dinosaurs. The distinctive theropod ichnotaxon
To conclude, a considerable range of possible lifestyles has been proposed for Caenagnathidae, some of which may be mutually exclusive (e.g., strict herbivory versus predation on small vertebrates; wading versus climbing). This is in spite of the fact that, prior to the discovery of
(DOC)
We thank Fred Nuss and Robert Detrich for discovering CM 78000 and CM 78001 and Triebold Paleontology, Inc. for the preparation of these specimens. Scott Haire discovered MRF 319, and Barbara Benty, Stephen Begin, and William Wagner prepared this specimen. Bill Simpson and Olivier Rieppel loaned FMNH PR 2296 to the senior author. Jonah Choiniere, Nick Longrich, and Lindsay Zanno participated in discussions of oviraptorosaur anatomy and taxonomy. Greg Funston and Philip Currie gave permission to cite their manuscript in press. Walter Stein and Mike Triebold provided information on the provenance of the CM specimens and other North American Late Cretaceous oviraptorosaur body and putative trace fossils. Scott Williams shared information on the depositional setting of the Hell Creek oviraptorosaur skeleton that was recently discovered by the Burpee Museum of Natural History, and Daniel Malleske commented on the pathological pedal phalanx of CM 78000. Ben Creisler and David Krentz provided etymological suggestions. Kirk Johnson granted access to the map that was modified to become Figure 1, while Scott Hartman produced the skull and skeletal reconstructions that constitute Figures 2A, 4A, and 5A. Mark Klingler constructed Figure 1 from the map provided by Kirk Johnson, executed the bone illustrations in Figures 2B–G and 4B–L, assisted with the assembly of Figure 3, and slightly modified Scott Hartman's skull and skeletal reconstructions under the guidance of the senior author. The Willi Hennig Society provided the version of TNT used for phylogenetic analysis. The manuscript benefited from reviews by Jim Clark and Philip Currie and from editorial comments by David Evans.