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Coelophysis

Cope, 1889 SEE-low-FY-sis /ˌsiːloʊˈfaɪsɪs/

From Greek 'koilos' (hollow) and 'physis' (form, nature), referring to the hollow vertebrae.

227.3–201.4 million years ago Norian–Rhaetian, Late Triassic
Late Triassic stages

Coelophysis is the type genus of Coelophysidae and one of the best-known Triassic dinosaurs. The type and only valid species, Coelophysis bauri, was erected by Edward Drinker Cope in 1889 on fragmentary syntypes collected by David Baldwin from Arroyo Seco, Rio Arriba County, New Mexico. Cope's original syntypes were diagnostically inadequate, and the taxon's modern hypodigm overwhelmingly comes from the Whitaker Quarry at Ghost Ranch — a Late Triassic mass-mortality bonebed first opened in 1947 that has yielded hundreds of articulated skeletons across a complete ontogenetic series. Following decades of dispute about whether the Ghost Ranch material truly belonged to Cope's nominal taxon, the ICZN issued Opinion 1842 in 1996, designating the articulated Whitaker Quarry skeleton AMNH 7224 as the neotype of C. bauri and rejecting the rival genus Rioarribasaurus colberti (Hunt and Lucas, 1991) as a junior objective synonym. Rinehart and colleagues (2009) reanalyzed the entire hypodigm and showed that Coelophysis was sexually dimorphic (gracile and robust morphs distinguished by skull/neck length and sacrum fusion), preserved the oldest known furcula in any non-avian dinosaur, had hawk-like vision (sclerotic-ring geometry), and engaged in genuine cannibalism (juvenile bones in adult coprolites and regurgitalites — separate from Colbert's earlier in-ribcage 'cannibalism' claim, which Nesbitt and colleagues 2006 showed was actually a small crurotarsan).

Diagnosis

  1. Skull long and narrow with an elongate preorbital region bearing a prominent preorbital groove anterior to the orbit, promoting binocular overlap of the visual fields.
  2. Ten cervical vertebrae with elongate, rod-like cervical ribs that overlap up to five consecutive vertebrae posteriorly.
  3. Thirteen dorsal vertebrae; cervical centra amphicoelous with elliptical pleurocoels on the lateral surfaces; pleurocoels absent in dorsals.
  4. Sacrum of five vertebrae; variable fusion of s4-s5 centra constitutes a sexually dimorphic character (gracile-morph specimens unfused; robust- morph fused).
  5. Pubis bears two foramina — an elliptical obturator foramen and a larger accessory 'ceratosaur foramen' medial to it.
  6. V-shaped furcula present, with epicleidial facets near the distal rami tips — the oldest known furcula in any non-avian dinosaur.
  7. Femur midshaft diameter shows an allometric growth constant of ~1.5 indicating cursorial adaptation; tibiotarsus longer than femur.

Species

Coelophysis bauri Cope, 1889

Type species

Honors George Baur, the German-American paleontologist who had earlier studied the syntype material.

Neotype
AMNH 7224 , American Museum of Natural History
Material
Articulated complete skeleton of an adult robust-morph individual.
Horizon
Chinle Formation, Norian–Rhaetian, Late Triassic , 227.3–201.4 million years ago
Locality
Whitaker Quarry, Ghost Ranch, New Mexico, United States The quarry lies in the informal 'siltstone member' of the Chinle Formation, whose correlation with the formation's named subdivisions is unresolved. Nesbitt and Sues (2020) record that it "remains contentious", listing a Petrified Forest Member correlation after Schwartz and Gillette (1994) against a Rock Point Member one after Lucas and Hunt (1993). Cather and colleagues (2013) note that magnetostratigraphic analysis "has called into question" the Rock Point correlation and favor reverting to the siltstone member. No member is recorded while that stands.

Synonyms

  • Rioarribasaurus colberti junior objective

    Hunt and Lucas (1991) erected Rioarribasaurus colberti for the Whitaker Quarry skeleton AMNH 7224. ICZN Opinion 1842 (1996) simultaneously designated AMNH 7224 as the neotype of Coelophysis bauri (under plenary powers, setting aside Cope's diagnostically inadequate syntypes), making Rioarribasaurus a junior objective synonym of Coelophysis and colberti a junior objective synonym of bauri. Both were placed on the Official Index of Rejected and Invalid Names.

Synonyms of the genus

Name Type Reason
Longosaurus longicollis junior subjective Welles (1984) erected Longosaurus as a replacement genus for "Coelurus" longicollis Cope, 1887 (a Ghost Ranch coelophysoid). Subsequent work treats the material as referable to Coelophysis, making Longosaurus a junior synonym.

Notable specimens

  • NMMNH P-44551

    New Mexico Museum of Natural History and Science gut contents

    Additional preparation of excavated matrix revealed regurgitate material in and around the mouth, including tooth and jaw bone fragments considered morphologically identical to a juvenile Coelophysis, cited as evidence of cannibalism.

    Rinehart et al. (2009)

  • NMMNH P-4200

    New Mexico Museum of Natural History and Science sensory

    Juvenile preserving a complete scleral ring, used to infer that Coelophysis was a diurnal, visually oriented predator whose vision rivaled that of modern birds of prey and was closest to eagles and hawks.

    Rinehart et al. (2004)

ICZN cases

References

  1. Rinehart, L. F.; Heckert, A. B.; Lucas, S. G.; Hunt, A. P. (2004). The sclerotic ring of the Late Triassic theropod dinosaur Coelophysis. New Mexico Geological Society Spring Meeting 26: 64.

    Spring meeting abstract.

    rinehart2004a
  2. Cope, E. D. (1889). On a new genus of Triassic Dinosauria. The American Naturalist 23(271): 626. American Society of Naturalists.

    Brief paragraph (~130 words) erecting Coelophysis to receive three species (C. bauri, C. longicollis, C. willistoni) previously described under Coelurus.

    cope1889b
  3. Colbert, E. H. (1989). The Triassic Dinosaur Coelophysis. Bulletin of the Museum of Northern Arizona 57: 1-160. Museum of Northern Arizona.

    Pre-Rinehart-2009 canonical monograph on the Whitaker Quarry hypodigm; cited as the seminal Ghost Ranch reference.

    colbert1989a
  4. Colbert, E. H.; Charig, A. J.; Dodson, P.; Gillette, D. D.; Ostrom, J. H.; Weishampel, D. B. (1992). Coelurus bauri Cope, 1887 (currently Coelophysis bauri; Reptilia, Saurischia): proposed replacement of the lectotype by a neotype. Bulletin of Zoological Nomenclature 49(4): 276-279. International Trust for Zoological Nomenclature.

    Case 2840; the petition that led to Opinion 1842, requesting that AMNH 7224 be designated the neotype of Coelophysis bauri.

    colbert1992a
  5. International Commission on Zoological Nomenclature (1996). Opinion 1842. Coelophysis Cope, 1889 (Reptilia, Saurischia): a neotype designated under the plenary powers. Bulletin of Zoological Nomenclature 53(2): 142-144. International Trust for Zoological Nomenclature.

    Plenary-powers ruling on Case 2840 (Colbert and colleagues, 1992). Designates AMNH 7224 as neotype of Coelophysis bauri and rejects Rioarribasaurus colberti.

    iczn1996a
  6. Nesbitt, S. J.; Irmis, R. B.; Parker, W. G. (2007). A critical re-evaluation of the Late Triassic dinosaur taxa of North America. Journal of Systematic Palaeontology 5(2): 209-243. Taylor & Francis. doi:10.1017/S1477201907002040

    Reassesses Cope's syntype material element-by-element, shows it is multitaxic; reassigns Eucoelophysis baldwini to a non-dinosaurian basal ornithodiran.

    nesbitt2007a
  7. Rinehart, L. F.; Lucas, S. G.; Heckert, A. B.; Spielmann, J. A.; Celeskey, M. D. (2009). The paleobiology of Coelophysis bauri (Cope) from the Upper Triassic (Apachean) Whitaker quarry, New Mexico, with detailed analysis of a single quarry block. New Mexico Museum of Natural History and Science Bulletin 45: 1-260. New Mexico Museum of Natural History and Science.

    Comprehensive 260-page monograph on the Whitaker Quarry hypodigm; documents sexual dimorphism, hawk-like vision, the oldest non-avian-dinosaur furcula, and genuine juvenile cannibalism.

    rinehart2009a
  8. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the appearance features.

    paul2024a
  9. Welles, S. P. (1984). Dilophosaurus wetherilli (Dinosauria, Theropoda): osteology and comparisons. Palaeontographica Abteilung A 185: 85-180.

    Erected Longosaurus as a replacement genus for "Coelurus" longicollis.

    welles1984a
  10. Cope, E. D. (1887). The dinosaurian genus Coelurus. The American Naturalist 21(4): 367-369. University of Chicago Press. doi:10.1086/274464

    Named the species longicollis, as Coelurus longicollis.

    cope1887a
  11. Hunt, A. P.; Lucas, S. G. (1991). Rioarribasaurus, a new name for a Late Triassic dinosaur from New Mexico (USA). Paläontologische Zeitschrift 65(1-2): 191-198. Springer Science and Business Media LLC. doi:10.1007/BF02985783

    Proposed Rioarribasaurus for the Ghost Ranch material, later rejected in favor of Coelophysis.

    hunt1991a
  12. Nesbitt, S. J.; Sues, H. D. (2020). The osteology of the early-diverging dinosaur Daemonosaurus chauliodus (Archosauria: Dinosauria) from the Coelophysis Quarry (Triassic: Rhaetian) of New Mexico and its relationships to other early dinosaurs. Zoological Journal of the Linnean Society 191: 150-179. doi:10.1093/zoolinnean/zlaa080 nesbitt2020a
  13. Cather, S. M.; Zeigler, K. E.; Mack, G. H.; Kelley, S. A. (2013). Toward standardization of Phanerozoic stratigraphic nomenclature in New Mexico. Rocky Mountain Geology 48(2): 101-124. Geological Society of America. doi:10.2113/gsrocky.48.2.101 cather2013a
  14. Lucas, S. G.; Hunt, A. P. (1993). Tetrapod biochronology of the Chinle Group (Upper Triassic), western United States. New Mexico Museum of Natural History and Science Bulletin 3: 327-329. lucas1993a
  15. Schwartz, H. L.; Gillette, D. D. (1994). Geology and taphonomy of the Coelophysis quarry, Upper Triassic Chinle Formation, Ghost Ranch, New Mexico. Journal of Paleontology 68(5): 1118-1130. doi:10.1017/S0022336000026718 schwartz1994a