Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2018 Aug 24;6:e5435.
doi: 10.7717/peerj.5435. eCollection 2018.

A New Nodosaurid Ankylosaur (Dinosauria: Thyreophora) From the Upper Cretaceous Menefee Formation of New Mexico

Affiliations
Free PMC article

A New Nodosaurid Ankylosaur (Dinosauria: Thyreophora) From the Upper Cretaceous Menefee Formation of New Mexico

Andrew T McDonald et al. PeerJ. .
Free PMC article

Abstract

Nodosauridae is a clade of armored dinosaurs with a rich fossil record and long history of study in North America. Nodosaurid fossils have been collected throughout the western United States and Canada. Here, we report three new nodosaurid specimens from the Upper Cretaceous (lower Campanian) Allison Member of the Menefee Formation, San Juan Basin, northwestern New Mexico. The three specimens belong to a new genus and species, Invictarx zephyri, characterized by a unique combination of features pertaining to the morphology of the osteoderms. Among the three specimens there are representative cervical/pectoral and thoracic osteoderms, as well as components of a probable co-ossified pelvic shield. The new tax on is most similar to Glyptodontopelta mimus from the Maastrichtian of New Mexico.

Keywords: Allison Member; Ankylosauria; Invictarx zephyri; Menefee Formation; Nodosauridae.

Conflict of interest statement

The authors declare that they have no competing interests. Andrew T. McDonald is employed by Western Science Center, Hemet, California, and Douglas G. Wolfe is employed by White Mountain Dinosaur Exploration Center, Springerville, Arizona.

Figures

Figure 1
Figure 1. Stratigraphic occurrences of Invictarx zephyri and other ankylosaurs from the San Juan Basin.
Generalized stratigraphic column of Upper Cretaceous strata in the San Juan Basin, northwestern New Mexico, showing the stratigraphic positions of the nodosaurids I. zephyri and Glyptodontopelta mimus and the ankylosaurids Ahshislepelta minor, Nodocephalosaurus kirtlandensis, and Ziapelta sanjuanensis. Ankylosaur occurrence data are from Sullivan & Lucas (2015). Nodosaurid silhouette by Scott Hartman (https://creativecommons.org/publicdomain/zero/1.0/), and ankylosaurid silhouette by Andrew A. Farke (https://creativecommons.org/licenses/by/3.0/), both available from PhyloPic. Stratigraphic column is derived from data in Miller, Carey & Thompson-Rizer (1991), Molenaar et al. (2002), Sullivan & Lucas (2006), and Fowler (2017).
Figure 2
Figure 2. Reconstructions of identifiable osteoderm placements in the three specimens of I. zephyri.
WSC 16505 (holotype) osteoderms (A) and color-code (B). UMNH VP 28350 osteoderms (C) and color-code (D). UMNH VP 28351 osteoderms (E) and color-code (F). All osteoderms are set to the same scale. Body outlines based upon skeletal reconstruction of S. edwardsorum (Fig. 2 in Carpenter (1984)). Scale bars equal 50 cm.
Figure 3
Figure 3. Cervical/pectoral osteoderms of WSC 16505, holotype of I. zephyri.
WSC 16505.1, right medial cervical/pectoral osteoderm in (A) external, (B) basal, (C) medial, (D) lateral, (E) cranial, and (F) caudal views. WSC 16505.2, left medial cervical/pectoral osteoderm in (G) external, (H) basal, (I) medial, (J) lateral, (K) cranial, and (L) caudal views. WSC 16505.3, left distal osteoderm from the second cervical half-ring in (M) external, (N) basal, (O) medial, (P) lateral, (Q) cranial, and (R) caudal views. Study site: bng, bifurcated neurovascular groove. Cranial is toward the top of the figure in A, B, G, H, M, and N. Scale bars equal five cm.
Figure 4
Figure 4. Thoracic osteoderms of WSC 16505, holotype of I. zephyri.
WSC 16505.4, lateral thoracic osteoderm in (A) external, (B) basal, (C) medial, (D) lateral, (E) cranial, and (F) caudal views. WSC 16505.5, thoracic osteoderm in (G) external, (H) basal, (I) medial or lateral (orientation uncertain), (J) medial or lateral (orientation uncertain), (K) cranial, and (L) caudal views. WSC 16505.6, thoracic ossicle in (M) external, (N) basal, and (O–R) marginal views (orientation uncertain). Scale bars equal five cm.
Figure 5
Figure 5. Dorsal vertebrae of UMNH VP 28350, referred specimen of I. zephyri.
Middle dorsal vertebra in (A) cranial, (B) caudal, (C) right lateral, and (D) left lateral views. Middle dorsal vertebra in (E) cranial, (F) caudal, (G) right lateral, and (H) left lateral views. Middle dorsal vertebra in (I) cranial, (J) caudal, (K) right lateral, and (L) left lateral views. Study sites: par, parapophysis; prz, prezygapophysis. Scale bars equal five cm.
Figure 6
Figure 6. Appendicular elements of UMNH VP 28350, referred specimen of I. zephyri.
Distal end of left humerus in (A) cranial, (B) caudal, and (C) distal views. Distal end of left ulna in (D) medial and (E) distal views. (F) Proximal end of left radius, orientation uncertain. Proximal end of right radius in (G) proximal, (H) lateral, (I) cranial, (J) medial, and (K) distal views. (L) Metacarpal, orientation uncertain. Study sites: clr, craniolateral ridge; rc, radial condyle; uas, articulation surface for ulna; uc, ulnar condyle. Scale bars equal five cm.
Figure 7
Figure 7. Osteoderms of UMNH VP 28350, referred specimen of I. zephyri.
Cervical/pectoral osteoderm fragment in (A) external view and (B) medial or lateral view (orientation uncertain). Distal osteoderm of second cervical half-ring in (C) external, (D) basal, and (E) medial views. Dorsal thoracic osteoderm in (F) external view, (G) medial or lateral view (orientation uncertain), (H) medial or lateral view (orientation uncertain), (I) cranial or caudal view (orientation uncertain), and (J) cranial or caudal view (orientation uncertain). Lateral thoracic osteoderm in (K) external, (L) medial, (M) lateral, (N) cranial, and (O) caudal views. Lateral thoracic osteoderm in (P) external, (Q) basal, (R) lateral, (S) medial, (T) cranial, and (U) caudal views. Pelvic osteoderm fragment in (V) external view and (W) marginal view (orientation uncertain). Scale bars equal five cm.
Figure 8
Figure 8. Cervical/pectoral osteoderms of UMNH VP 28351, referred specimen of I. zephyri.
Medial cervical/pectoral osteoderm in (A) external, (B) basal, (C) medial or lateral (orientation uncertain), (D) medial or lateral (orientation uncertain), and (E) caudal views. Base of pectoral or thoracic distal spine in (F) external, (G) medial or lateral (orientation uncertain), (H) medial or lateral (orientation uncertain), (I) cranial, and (J) caudal views. Tip of pectoral or thoracic distal spine in (K) view of preserved external surface and (L) view of cross-section. Cranial is toward the top of the Figure in A, B, and F. Scale bars equal five cm.
Figure 9
Figure 9. Thoracic osteoderms of UMNH VP 28351, referred specimen of I. zephyri.
Dorsal thoracic osteoderm in (A) external, (B) medial or lateral (orientation uncertain), (C) medial or lateral (orientation uncertain), (D) cranial, and (E) caudal views. Dorsal thoracic osteoderm in (F) external, (G) medial or lateral (orientation uncertain), (H) medial or lateral (orientation uncertain), (I) cranial, and (J) caudal views. Scale bars equal five cm.
Figure 10
Figure 10. Thoracic osteoderms of UMNH VP 28351, referred specimen of I. zephyri.
Lateral thoracic osteoderm in (A) external, (B) medial or lateral (orientation uncertain), (C) medial or lateral (orientation uncertain), (D) cranial or caudal (orientation uncertain), and (E) cranial or caudal (orientation uncertain) views. Lateral thoracic osteoderm in (F) external, (G) lateral, (H) medial, (I) cranial, and (J) caudal views. Thoracic osteoderm fragment in (K) external and (L) cross-sectional views. Thoracic interstitial ossicle in (M) external and (N) marginal views. Thoracic interstitial ossicle in (O) external view. Scale bars equal five cm.
Figure 11
Figure 11. Pelvic osteoderm of UMNH VP 28351, referred specimen of I. zephyri.
Pelvic osteoderm in (A) external and (B) marginal views. Scale bar equals five cm.

Similar articles

See all similar articles

References

    1. Arbour VM, Burns ME, Currie PJ. A review of pelvic shield morphology in ankylosaurs (Dinosauria: Ornithischia) Journal of Paleontology. 2011;85(2):298–302. doi: 10.1666/10-071.1. - DOI
    1. Arbour VM, Currie PJ. Euoplocephalus tutus and the diversity of ankylosaurid dinosaurs in the Late Cretaceous of Alberta, Canada, and Montana, USA. PLOS ONE. 2013;8(5):e62421 doi: 10.1371/journal.pone.0062421. - DOI - PMC - PubMed
    1. Arbour VM, Currie PJ. Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs. Journal of Systematic Palaeontology. 2016;14(5):385–444. doi: 10.1080/14772019.2015.1059985. - DOI
    1. Arbour VM, Zanno LE, Gates T. Ankylosaurian dinosaur palaeoenvironmental associations were influenced by extirpation, sea-level fluctuation, and geodispersal. Palaeogeography, Palaeoclimatology, Palaeoecology. 2016;449:289–299. doi: 10.1016/j.palaeo.2016.02.033. - DOI
    1. Baron MG, Norman DB, Barrett PM. A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature. 2017;543(7646):501–506. doi: 10.1038/nature21700. - DOI - PubMed

Grant support

The field work that led to the discovery of the fossils was supported by grants from the Western Interior Paleontological Society, Geological Society of America, and University of Pennsylvania. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

LinkOut - more resources

Feedback