Open Paleo

Protohadros

Head, 1998 PROH-to-HAD-ros

From Greek 'protos' meaning 'first' and 'hadros' meaning 'thick' (as in Hadrosauridae), meaning 'first hadrosaur.' The specific name byrdi honors discoverer Gary Byrd.

100.5–93.9 million years ago Cenomanian, Late Cretaceous
Late Cretaceous stages

Protohadros is a genus of hadrosauromorph dinosaur from the early Late Cretaceous (Cenomanian stage, approximately 100-93.9 million years ago) of what is now Texas, United States. It is represented by the species Protohadros byrdi, known from a partially complete skull and associated postcranial remains recovered from the Lewisville Formation of the Woodbine Group. It is among the earliest hadrosauroids known from North America.

Under dispute

Protohadros byrdi was described as the most basal hadrosaurid under the expanded Hadrosauridae of Head (1998), which he diagnosed without the loss of the surangular foramen that Protohadros retains. Later analyses place it outside Hadrosauridae. Most recover it closer to hadrosaurids than Probactrosaurus, within Hadrosauromorpha as Norman (2014) defines it, often as the sister of Eolambia (Prieto-Márquez, 2010; Xing and colleagues, 2014; Wang and colleagues, 2017). Analyses on Norman's matrices instead place it below Probactrosaurus, outside Hadrosauromorpha (Norman, 2004, 2014).

Diagnosis

  1. Ventrally deflected muzzle with massive predentary and robust, rostrally expanded and deflected dentary
  2. Strongly bilobate jugal-maxillary articulation
  3. Elongate maxillary rostral processes
  4. Retention of jugal-ectopterygoid contact
  5. Short jugal-postorbital articulation
  6. Ventral orientation of angular
  7. Retention of surangular foramen

Species

Protohadros byrdi Head, 1998

Type species

Named for Gary Byrd, the part-time paleontologist who discovered the first remains of the species in 1994.

Holotype
SMU 74582 , Shuler Museum of Paleontology, Southern Methodist University
Material
Nearly complete skull and isolated postcrania. Skull lacking left mandible, most braincase, and occipital region.
Horizon
Arlington Member, Lewisville Formation, Cenomanian, Late Cretaceous , 100.5–93.9 million years ago
Locality
SMU 303, Texas, United States

References

  1. Head, J. J. (1998). A new species of basal hadrosaurid (Dinosauria, Ornithischia) from the Cenomanian of Texas. Journal of Vertebrate Paleontology 18(4): 718-738. Informa UK Limited. doi:10.1080/02724634.1998.10011101 head1998a
  2. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the appearance features.

    paul2024a
  3. Norman, D. B. (2014). Iguanodonts from the Wealden of England: do they contribute to the discussion concerning hadrosaur origins?. Hadrosaurs 10-43. Indiana University Press, Bloomington.

    Named Hadrosauromorpha and recovered Protohadros below Probactrosaurus, outside it.

    norman2014b
  4. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Reports the placement within Hadrosauromorpha.

    jones2026a
  5. Norman, D. B. (2004). Basal Iguanodontia. The Dinosauria, Second Edition (Weishampel, D. B.; Dodson, P.; Osmólska, H., eds.) 413-437. University of California Press, Berkeley.

    Recovered Protohadros below Probactrosaurus, which is the sister of Hadrosauridae in that analysis.

    norman2004a
  6. Xing, H.; Wang, D.; Han, F.; Sullivan, C.; Ma, Q.; He, Y.; Hone, D. W. E.; Yan, R.; Du, F.; Xu, X. (2014). A New Basal Hadrosauroid Dinosaur (Dinosauria: Ornithopoda) with Transitional Features from the Late Cretaceous of Henan Province, China. PLoS ONE 9(6): e98821. Public Library of Science (PLoS). doi:10.1371/journal.pone.0098821

    Recovered Protohadros with Eolambia as a North American clade more derived than Probactrosaurus.

    xing2014a
  7. Wang, R. F.; You, H. L.; Wang, S. Z.; Xu, S. C.; Yi, J.; Xie, L. J.; Jia, L.; Xing, H. (2017). A second hadrosauroid dinosaur from the early Late Cretaceous of Zuoyun, Shanxi Province, China. Historical Biology 29(1): 17-24. Informa UK Limited. doi:10.1080/08912963.2015.1118688

    Recovered Eolambia and Protohadros as slightly more derived than Probactrosaurus and the other basal Asian hadrosauroids.

    wang2017c
  8. Prieto-Márquez, A. (2010). Global phylogeny of Hadrosauridae (Dinosauria: Ornithopoda) using parsimony and Bayesian methods. Zoological Journal of the Linnean Society 159(2): 435-502. Oxford University Press (OUP). doi:10.1111/j.1096-3642.2009.00617.x

    Recovered Protohadros as the sister of Eolambia, above Probactrosaurus, in a global hadrosaurid analysis.

    prieto-márquez2010c