[D] Titanoceratops ouranos [sG] [T]
Describer
Longrich 2010
Time
Cretaceous Late Campanian
Classification
Ornithischia Genasauria Cerapoda Marginocephalia Ceratopia Neoceratopia Ceratopidae Chasmosaurinae
Diet
Herbivore
Fossilsite
upper Fruitland Formation or the lower Kirtland Formation, San Juan County, New Mexico, US
Info
Abstract
At the end of the Cretaceous, 65.5 million years ago, the giant ceratopsids Triceratops and Torosaurus dominated North America’s dinosaur fauna. The origins of these giant ceratopsids, the Triceratopsini, are poorly understood. This paper describes Titanoceratops ouranos, a giant ceratopsid from the late Campanian (73–74 Ma) of New Mexico, and the earliest known triceratopsin.
The holotype was previously interpreted as an aberrant and exceptionally large specimen of Pentaceratops sternbergii, but the animal does not show the diagnostic features of Pentaceratops. Instead, cladistic analysis shows that Titanoceratops is the sister taxon of a clade formed by Eotriceratops, Triceratops and Torosaurus. With an estimated mass of 6.5 tons, Titanoceratops is among the largest dinosaurs known from the Campanian of North America, and rivaled Triceratops in size.
The recognition of Titanoceratops suggests that giant chasmosaurines evolved once, among the Triceratopsini, and that the group evolved large size five million years earlier than previously thought. The giant horned dinosaurs probably originated in the southern part of the North American continent during the Campanian but only became widespread during the Maastrichtian.
Body length: 6 m , Skull length: 2 m
Holotype
(OMNH 10165): partial skeleton consisting of a partial skull and jaws, syncervical, cervical, dorsal and sacral vertebrae, caudal certebrae, ribs, humeri, right radius, femora, tibiae, right fibula, ilia, ischia, and ossified tendons
Etymology
The generic name is derived from titan (Greek, mythical race of ancient giants), ceras, (Greek, horned), and ops (Greek, face).| The specific name refers to Ouranos, the father of the Titans in Greek mythology.
Horizon and loaclity
upper Fruitland Formation or the lower Kirtland Formation. Upper Cretaceous (Campanian), San Juan County, New Mexico.
Diagnosis
Triceratopsin differing from Triceratops in having thin squamosals, parietal fenestrae, and a hornlike epijugal; differing from Triceratops and Torosaurusin having a narrow parietal median bar and a vertical narial strut with a narrow base; differing from Triceratops, Torosaurus, and Eotriceratops in having an enlarged epoccipital on the caudal end of the squamosal and an extremely large premaxillary fossa, and in lacking a dorsally inflected narial process of the premaxilla; differing from Eotriceratops in having a premaxilla that is elongate relative to its height.
The following characters differentiate Titanoceratops from Pentaceratops: 1. large size (exceeding 5000 kg), 2. parietal median bar with a dorsal ridge, 3. anterior squamosal epoccipitals low and broad, 4. posteriormost squamosal epoccipital smaller and directed caudally, rather than laterally, 5. postorbital horns with massive bases extending caudal to the orbit, 6. extensive cornual sinuses invading the base of the postorbital horns, 7. anterior frontal sinus, 8. postorbital horns strongly curved anteriorly, 9. postorbital horns extremely elongate, about 75% skull basal length,10. nasal horn over anterior part of external naris, 11. narial strut of premaxilla slender, 12. premaxillary fossa extremely large and anteroposteriorly elongate, 13. premaxillary fossa extends caudoventrally to excavate the inside of the narial strut and premaxilla, and bounded laterally by an auxiliary wall, 14. premaxillae extremely elongate, 15. maxillary ramus of nasal short, 16. maxillary ramus of premaxilla unforked, 17. external naris extended caudally over the maxillary tooth row, 18. accessory antorbital fenestra absent, 19. scapular blade straight, 20. humeral deltopectoral crest extended distally; 1. femur straight and vertically oriented; 22. ischium expanded at midshaft with a broad caudal flange. A single autapomorphy, the extreme enlargement of the premaxillary fossa, differentiates Titanoceratops from all other chasmosaurines.