Open Paleo

Agujaceratops

Lucas et al., 2006 ah-GOO-ja-SEH-ruh-tops

Named after the Aguja Formation where it was found, combined with Greek 'keras' meaning 'horn' and 'ops' meaning 'face'; meaning 'horned face from Aguja'

83.6–72.2 million years ago Campanian, Late Cretaceous
Late Cretaceous stages

Agujaceratops is a genus of chasmosaurine ceratopsid dinosaur from the Late Cretaceous (Campanian) of western Texas. Two species are known: A. mariscalensis and A. mavericus, both recovered from the Aguja Formation.

Diagnosis

  1. Anteromedial processes of the nasals intercede between the premaxillae and extend forward along the internarial bar
  2. Septal flange of the premaxillae extends along the entire posterior margin of the narial strut
  3. Accessory antorbital fenestra present
  4. Postorbital horncores posteriorly curved
  5. Cornual sinuses absent
  6. Posterior end of the squamosal with marked dorsal curvature
  7. Lateral ramus of the parietal discontinuous, the squamosal forming part of the lateral border of the parietal fenestra

Species (2)

Agujaceratops mariscalensis Lucas et al., 2006

Type species

Named for the Mariscal area of Big Bend National Park, Texas, where the holotype was collected.

Holotype
UTEP P.37.7.086 , University of Texas at El Paso
Material
Braincase, left supraorbital horncore, left maxilla, and right dentary; collected from the upper part of the formation.
Horizon
Alto Shale Member, Aguja Formation, Campanian, Late Cretaceous , 83.6–72.2 million years ago
Locality
WPA-1, Texas, United States
Diagnosis
  1. Squamosal relatively short (elongate in A. mavericus)
  2. Six episquamosals, or corresponding attachment loci on the squamosal (up to 10 in A. mavericus)
  3. Episquamosals large and triangular (small and elliptical in A. mavericus)
  4. Postorbital horncores with high basal circumference and high taper relative to length

Agujaceratops mavericus Lehman et al., 2016

From 'maverick' (an unbranded range animal or lone dissenter); refers to the Old Maverick Road, near where the holotype was collected.

Holotype
TMM 43098-1 , Texas Memorial Museum, Austin, Texas, USA (used for collections now housed in the Vertebrate Paleontology Collections at the Jackson School Museum of Earth History, Austin, Texas, USA), now called the Texas Science and Natural History Museum
Material
Nearly complete, disarticulated skull (the 'Rattlesnake Mt exemplar'), including an intact right postorbital horncore and squamosal, but lacking preserved parietal remains.
Horizon
Alto Shale Member, Aguja Formation, Campanian, Late Cretaceous , 83.6–72.2 million years ago
Locality
Rattlesnake Mountain, Texas, United States
Diagnosis
  1. Squamosal relatively elongate (width/length ratio about 0.36, versus 0.44-0.55 in A. mariscalensis)
  2. Up to 10 episquamosals or corresponding marginal undulations of the squamosal (versus six in A. mariscalensis)
  3. Episquamosals small and elliptical in cross section (large and triangular in A. mariscalensis)
  4. Postorbital horncores with low basal circumference and low taper relative to length

References

  1. Lucas, S. G.; Sullivan, R. M.; Hunt, A. P. (2006). Re-evaluation of Pentaceratops and Chasmosaurus (Ornithischia: Ceratopsidae) in the Upper Cretaceous of the Western Interior. Late Cretaceous Vertebrates from the Western Interior 35: 367-370. lucas2006a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026a
  3. Lehman, T. M.; Wick, S. L.; Macon, C. C.; Wagner, J. R.; Waggoner, K. J.; Brink, A. A.; Shiller, T. A., II (2024). Stratigraphy and depositional history of the Aguja Formation (Upper Cretaceous, Campanian) of West Texas, southwestern USA. Geosphere 20(3): 825-879. Geological Society of America. doi:10.1130/GES02662.1

    Formally recognizes the Aguja's informal upper shale member as the Alto Shale Member.

    lehman2024a
  4. Lehman, T. M.; Wick, S. L.; Barnes, K. R. (2016). New specimens of horned dinosaurs from the Aguja Formation of West Texas, and a revision of Agujaceratops. Journal of Systematic Palaeontology 15(8): 641-674. Informa UK Limited. doi:10.1080/14772019.2016.1210683

    Revision of the genus. Erects A. mavericus, diagnoses the two species against each other, and reassigns the complete Rattlesnake Mountain skull to the new species.

    lehman2016b
  5. Forster, C. A.; Sereno, P. C.; Evans, T. W.; Rowe, T. (1993). A complete skull of Chasmosaurus mariscalensis (Dinosauria: Ceratopsidae) from the Aguja Formation (late Campanian) of West Texas. Journal of Vertebrate Paleontology 13(2): 161-170. Informa UK Limited. doi:10.1080/02724634.1993.10011498

    Complete description of the skull that is now the A. mavericus holotype, published under the earlier combination Chasmosaurus mariscalensis.

    forster1993b