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, 9 (3), e92022
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A New Large-Bodied Oviraptorosaurian Theropod Dinosaur From the Latest Cretaceous of Western North America

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A New Large-Bodied Oviraptorosaurian Theropod Dinosaur From the Latest Cretaceous of Western North America

Matthew C Lamanna et al. PLoS One.

Erratum in

Abstract

The oviraptorosaurian theropod dinosaur clade Caenagnathidae has long been enigmatic due to the incomplete nature of nearly all described fossils. Here we describe Anzu wyliei gen. et sp. nov., a new taxon of large-bodied caenagnathid based primarily on three well-preserved partial skeletons. The specimens were recovered from the uppermost Cretaceous (upper Maastrichtian) Hell Creek Formation of North and South Dakota, and are therefore among the stratigraphically youngest known oviraptorosaurian remains. Collectively, the fossils include elements from most regions of the skeleton, providing a wealth of information on the osteology and evolutionary relationships of Caenagnathidae. Phylogenetic analysis reaffirms caenagnathid monophyly, and indicates that Anzu is most closely related to Caenagnathus collinsi, a taxon that is definitively known only from a mandible from the Campanian Dinosaur Park Formation of Alberta. The problematic oviraptorosaurs Microvenator and Gigantoraptor are recovered as basal caenagnathids, as has previously been suggested. Anzu and other caenagnathids may have favored well-watered floodplain settings over channel margins, and were probably ecological generalists that fed upon vegetation, small animals, and perhaps eggs.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Exposures of the Upper Cretaceous Hell Creek and Lance formations in western North America.
Localities that have yielded specimens of Anzu wyliei gen. et sp. nov. are marked by white stars. Map modified from . Scale bar  = 100 km.
Figure 2
Figure 2. Craniomandibular skeleton of Anzu wyliei gen. et sp. nov.
(A) Reconstructed skull and mandible in left lateral view, with preserved bones in gray. (B) Left premaxilla of CM 78001 in lateral view. (C) Left maxilla of CM 78001 in lateral view. (D) Left jugal of CM 78001 in lateral view. (E) Braincase with articulated quadrates and pterygoids of CM 78001 in posterior view. Reconstructed mandible of CM 78000 in left lateral (F) and dorsal (G) views (hatching indicates broken areas, dashed lines indicate restoration). Abbreviations: ang, angular; aof, antorbital fenestra; ap, ascending process; bpt, basipterygoid process; d, dentary; emf, external mandibular fenestra; fm, foramen magnum; lf, lateral flange; lg, lateral groove; lgl, lateral facet of mandibular glenoid; lr, lingual ridge; mgl, medial facet of mandibular glenoid; oc, occipital condyle; pdp, posterodorsal process; pop, paroccipital process; por, postorbital process; pt, pterygoid; pvp, posteroventral process; q, quadrate; qjp, quadratojugal process; r, retroarticular process; sac, surangular–articular–coronoid complex. Scale bars  = 10 cm in A; 1 cm in B–G.
Figure 3
Figure 3. Photographs of craniomandibular elements of Anzu wyliei gen. et sp. nov.
(A) Left premaxilla of CM 78001 in lateral view. Left maxilla of CM 78001 in lateral (B) and medial (C) views. Left jugal of CM 78001 in lateral (D) and medial (E) views. (F) Braincase with articulated quadrates and pterygoids of CM 78001 in posterior view. Right quadrate of CM 78000 in dorsal (G), anterior (H), posterior (I), ventral (J), medial (K), and lateral (L) views. (M) Fused pterygoids of CM 78000 in ventral view. Right ectopterygoid of CM 78001 in lateral (N) and medial (O) views. Fused dentaries of CM 78000 in left lateral (P), dorsal (Q), and ventral (R) views. Left surangular–articular–coronoid complex of CM 78000 in lateral (S) and dorsal (T) views. Left angular of CM 78000 in lateral (U) and medial (V) views. Abbreviations: aof, antorbital fenestra; ap, ascending process; bpt, basipterygoid process; emf, external mandibular fenestra; fm, foramen magnum; lf, lateral flange; lg, lateral groove; lgl, lateral facet of mandibular glenoid; lr, lingual ridge; mgl, medial facet of mandibular glenoid; oc, occipital condyle; pdp, posterodorsal process; pop, paroccipital process; por, postorbital process; ps, palatal shelf; pt, pterygoid; pvp, posteroventral process; pvpf, facet for posteroventral process of dentary; q, quadrate; qjp, quadratojugal process; r, retroarticular process. Scale bars  = 1 cm.
Figure 4
Figure 4. Postcranial skeleton of Anzu wyliei gen. et sp. nov. as preserved in the CM specimens.
(A) Skeletal reconstruction in left lateral view, with illustrated bones in gray and other preserved bones in white (hatching indicates heavily reconstructed portions of the ilia of CM 78001). (B) Anterior dorsal vertebra of CM 78001 in anterior view. Anterior (C) and posteriormost preserved (D) caudal vertebrae of CM 78000 in left lateral view. (E) Right humerus of CM 78000 in anterior view. (F) Manual ungual I of CM 78000 in lateral view. Left pubis (G) and ischium (H) of CM 78001 in lateral view. Right femur (I) and left tibia (J) and astragalocalcaneum (K) of CM 78000 in anterior view. (L) Pedal ungual of CM 78000 in lateral view. Abbreviations: ap, ascending process; atc, ‘accessory trochanteric crest’; cal, calcaneum; cc, cnemial crest; dpc, deltopectoral crest; el, extensor ‘lip’; f, foramen; fh, femoral head; hy, hypapophysis; isp, ischial peduncle; ns, neural spine; op, obturator process; pb, pubic ‘boot’; pf, pneumatic fossa; prz, prezygapophysis; tp, transverse process; tu, tubercle; vg, vascular groove. Scale bars  = 50 cm in A; 1 cm in B–L.
Figure 5
Figure 5. MRF 319, a partial oviraptorosaurian skeleton referred to Anzu wyliei gen. et sp. nov.
(A) Skeletal reconstruction in left lateral view, with preserved bones in gray and bones represented in other Anzu specimens in white (hatching indicates heavily reconstructed portions of the ilia of CM 78001). Middle-posterior (ninth?) cervical vertebra in (B) anterior, (C) left lateral, and (D) dorsal views. Posterior (11th?) cervical vertebra in (E) anterior, (F) left lateral, and (G) dorsal views. Posterior (12th?) cervical vertebra in (H) anterior, (I) left lateral, and (J) dorsal views. Anteroposteriorly crushed left radius in lateral (K) and anterior (L) views. Mediolaterally crushed left ulna in lateral (M) and anterior (N) views. (O) Partial left scapulocoracoid in lateral view. Dorsal rib in anterior (P) and posterior (Q) views. Abbreviations: acr, acromial process; cr, cervical rib; dip, distal processes; pat, pathology; pf, pneumatic fossa. Scale bars  = 50 cm in A; 1 cm in B–Q.
Figure 6
Figure 6. Strict consensus trees resulting from successive trials of phylogenetic analysis.
Numbers adjacent to each node are Bremer support values; named nodes are indicated with black dots. (A) Strict consensus of 2,610 most parsimonious trees of 509 steps recovered by initial analysis of all 41 taxa (38 oviraptorosaurs) included in the matrix. (B) Strict consensus of seven most parsimonious trees of 498 steps resulting from an analysis of 34 taxa (31 oviraptorosaurs), excluding all members of Caenagnathidae (as recovered by the initial trial) for which definitive mandibular material has not yet been discovered.
Figure 7
Figure 7. Calibrated phylogeny of oviraptorosaurian theropods showing hypothesized position of Anzu wyliei gen. et sp. nov.
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 (Figure 6B). Numbers adjacent to each node are Bremer support values; named nodes are indicated with black dots. Thick black bars indicate stratigraphic ranges of each taxon; small crossbars at ends of some bars indicate taxa that are especially poorly stratigraphically constrained (e.g., most Asian Late Cretaceous forms). Time scale follows . Sources for stratigraphic ranges of included taxa are provided in Table S9 in File S1.

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Grant support

Funding was provided by the Carnegie Museum of Natural History (http://www.carnegiemnh.org), an American Association of Anatomists Postdoctoral Fellowship (http://www.anatomy.org/content/postdoctoral-fellowship-criteria), and an American Philosophical Society Franklin Research Grant (http://www.amphilsoc.org/grants/franklin) to E.R.S., and a National Museum of Natural History Peter Buck Postdoctoral Fellowship (http://vertebrates.si.edu/vz_buck_fell_info.html) to T.R.L. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
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