Eotrachodon
From Greek eos (dawn) + Trachodon (an early hadrosaurid genus): 'dawn Trachodon', indicating it is a primitive relative of hadrosaurids.
Late Cretaceous stages
Eotrachodon is a genus of hadrosaurid dinosaur that lived in the Late Cretaceous of eastern North America. The holotype was found in the Mooreville Chalk Formation (Upper Santonian) of Alabama in 2007 and includes a well-preserved skull and partial skeleton, making it a rare find among dinosaurs of Appalachia.
Diagnosis
- Tripartite circumnarial depression divided longitudinally into dorsal and ventral fossae, the latter subdivided into caudoventral and lightly incised rostroventral fossae.
- Dorsal fossa of circumnarial depression above bony naris extending further caudally than caudal extent of caudoventral fossa.
- Caudodorsal region of circumnarial depression above bony naris excavating lateral nasal surface, deeply rostrally but gradually fading caudally.
- Premaxillary lateral process abruptly deflected ventrally, forming a 165-degree angle with long axis of circumnarial depression.
- Maxilla with subtriangular joint surface for jugal that is more laterally than dorsally facing and prominent dorsal jugal tubercle projected caudally.
- Steeply down-warped sagittal crest of parietal substantially elevated above temporal bar.
Species
Eotrachodon orientalis Prieto-Márquez et al., 2016
Type species
From Latin 'orientalis' meaning 'of the east', referring to its discovery in eastern North America.
- Holotype
- MSC 7949 , McWane Science Center
- Material
- Nearly complete, partially articulated cranium and fragmentary postcranium; cranial elements plus axis, cervical/dorsal/sacral/caudal vertebrae, partial left pubis and ischium, partial right tibia, two manual phalanges.
- Horizon
- lower Mooreville Chalk Formation, Santonian, Late Cretaceous , 85.7–83.6 million years ago
- Locality
- AMg-1, Alabama, United States
References
- Prieto-Márquez, A.; Erickson, G. M.; Ebersole, J. A. (2016). A primitive hadrosaurid from southeastern North America and the origin and early evolution of 'duck-billed' dinosaurs. Journal of Vertebrate Paleontology 36(2). Informa UK Limited. doi:10.1080/02724634.2015.1054495 prieto-márquez2016a
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Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.
Source of the body length, mass, and hip height estimates.
jones2026a -
Prieto-Márquez, A.; Erickson, G. M.; Ebersole, J. A. (2016). Anatomy and osteohistology of the basal hadrosaurid dinosaur Eotrachodon from the uppermost Santonian (Cretaceous) of southern Appalachia. PeerJ. PeerJ.
Gives the holotype's locality as AMg-1 and places it less than 24 cm above the Eutaw contact, low in the Mooreville Chalk.
prieto-márquez2016b