[D] Gryposaurus monumentensis [Su]
Sampson & Fates 2007
Cretaceous Late Campanian
Ornithischia Ornithopoda Hadrosauridae Hadrosaurinae Gryposaurini
Kaiparowits Formation, Utah, US
Gryposaurus (Lambe, 1914) > Gryposaurus notabilis (Lambe, 1914) = \\\\\\\"Hadrosauravus\\\\\\\" (Lambert, 1990)
Gryposaurus > Gryposaurus latidens (Horner, 1992)
Gryposaurus > Gryposaurus monumentensis (Sampson & Fates 2007)
Gryposaurus > Gryposaurus incurvimanus (Parks, 1920) > \\\\\\\"Kritosaurus incurvimanus\\\\\\\" (Parks, 1920)
Genus Derived from the Latin for ‘hooked beak’, intended by Lambe to reference the arch on the dorsal surface of the nasal, resembling a gryphin, and the Greek ‘saurus’ for lizard. Species In reference to the Grand Staircase-Escalante National Monument in southern Utah, where all referred materials of this species have been recovered.
RAM 6797, largely articulated skull lacking most of the right side of the skull.
Referred materials: UMNH VP 13970, partial, disarticulated subadult skull that includes both maxillae and dentaries, right nasal, partial quadrate, right jugal, right vomer, right prefrontal; UMNH VP 12265, partial skull and skeleton preserving both maxillae, left dentary, left quadrate, and partial jugal, left humerus, right and left scapulae, right coracoid, multiple ribs, both ilia, pubes, and ischia, most of the dorsal, sacral, and caudal series, including skin impressions on the right side of the vertebral series.
Hadrosaurids of the genus Gryposaurus possessing: anterodorsal process of maxilla seen through the external nares; subparallel anterior and posterior margins of the infratemporal fenestra; anteroposterior width of the infratemporal fenestra approximately half of the width of the orbit; predentary with large, pronged denticles; anterior portion of the dentary sharply downturned; surangular with distinct dorsal process on the median ridge of surangular; and ovoid mandibular foramen.
The following suite of characters is also present: sigmoidal lateroventral margin of the maxilla; large nasal arch located near the orbits rising above the level of the frontals; narrow ‘U’-shaped posterior margin of the external naris; and squamosal raised well above the level of the skull roof. Gryposaurus monumentensis is significantly more robust than any other species of Gryposaurus. It is most similar to Gryposaurus notabilis, but differs in having more steeply angled premaxillae, mediolaterally wider dentary, and generally more prominent jugal tubercle.