[D] Fruitadens haagarorum [sG] [T]
Describer
Butler, Galton, Porro, Chiappe, Henderson, and Erickson 2009
Time
Jurassic Late Tithonian
Classification
Ornithischia Ornithopoda Heterodontosauridae
Diet
Omnivore
Fossilsite
Morrison Formation, Brushy Basin Member, Colorado, US
Info
Abstract
The extremes of dinosaur body size have long fascinated scientists. The smallest (,1 m length) known dinosaurs are carnivorous saurischian theropods, and similarly diminutive herbivorous or omnivorous ornithischians (the other major group of dinosaurs) are unknown. We report a new ornithischian dinosaur, Fruitadens haagarorum, from the Late Jurassic of western North America that rivals the smallest theropods in size. The largest specimens of Fruitadens represent young adults in their fifth year of development and are estimated at just 65–75 cm in total body length and 0.5–0.75 kg body mass. They are thus the smallest known ornithischians. Fruitadens is a late-surviving member of the basal dinosaur clade Heterodontosauridae, and is the first member of this clade to be described from North America. The craniodental anatomy and diminutive body size of Fruitadens suggest that this taxon was an ecological generalist with an omnivorous diet, thus providing new insights into morphological and palaeoecological diversity within Dinosauria. Late-surviving (Late Jurassic and Early Cretaceous) heterodontosaurids are smaller and less ecologically specialized than Early (Late Triassic and Early Jurassic) heterodontosaurids, and this ecological generalization may account in part for the remarkable 100-million-year-long longevity of the clade.
Etymology
Fruitadens, from Fruita (hypodigmlocality) and dens (Latin, tooth); haagarorum, for Paul Haaga, Jr, Heather Haaga, Blythe Haaga, Paul Haaga III and Catalina Haaga, to honour their support of the Natural History Museum of Los Angeles County (LACM, Los Angeles, USA).
Holotype
LACM 115747, associated jaws, vertebrae and limb bones of a nearly full-grown individual; includes incomplete maxillae and dentaries, disarticulated vertebrae including cervicals, dorsals, six sacral vertebrae and caudals, proximal end of the right femur, both ends of both tibiae, and partial right metatarsal I.
Referred material
LACM 115727, nearly full-grown individual, fragmentary cervical, dorsal and caudal vertebrae, partial femora, and partial tibiae with articulated astragalus/calcaneum LACM 120478, juvenile individual, left humerus, partial left femur, and articulated left tibia, fibula and astragalus/ calcaneum LACM 128258, juvenile individual, right premaxilla, partial left maxilla, dentaries, dorsal vertebra, distal caudal vertebra
Horizon and locality
The base of the Brushy Basin Member of the Morrison Formation (Late Jurassic: early Tithonian) at the LACM Fruita Paleontological Area, northwest of Grand Junction, Colorado, USA (figure 1 and figure S1 in the electronic supplementary material; Kirkland 2006).
Diagnosis
Small heterodontosaurid ornithischian characterized by the following unique combination of characters, including autapomorphies (indicates character that is autapomorphic within Heterodontosauridae; indicates character that is autapomorphic within Ornithischia): (premaxillary crowns small and subequal in size, expanded labiolingually and mesiodistally above the root; maxillary caniniform absent; (axillary/dentary crowns low and triangular, with symmetrically distributed enamel; denticles extend over half of the maxillary/dentary crowns, not restricted to apical third; dentary caniniform present but apicobasal height does not exceed that of the largest dentary cheek tooth crown; small, unserrated, peg-like and procumbent tooth present anterior to the dentary caniniform; distal end of the tibia with anteromedial flange; apex of the ascending process of astragalus is formed by a separate ossification; two large foramina pierce anterior surface of the ascending process of astragalus
Butler, Galton, Porro, Chiappe, Henderson, and Erickson 2009
Time
Jurassic Late Tithonian
Classification
Ornithischia Ornithopoda Heterodontosauridae
Diet
Omnivore
Fossilsite
Morrison Formation, Brushy Basin Member, Colorado, US
Info
Abstract
The extremes of dinosaur body size have long fascinated scientists. The smallest (,1 m length) known dinosaurs are carnivorous saurischian theropods, and similarly diminutive herbivorous or omnivorous ornithischians (the other major group of dinosaurs) are unknown. We report a new ornithischian dinosaur, Fruitadens haagarorum, from the Late Jurassic of western North America that rivals the smallest theropods in size. The largest specimens of Fruitadens represent young adults in their fifth year of development and are estimated at just 65–75 cm in total body length and 0.5–0.75 kg body mass. They are thus the smallest known ornithischians. Fruitadens is a late-surviving member of the basal dinosaur clade Heterodontosauridae, and is the first member of this clade to be described from North America. The craniodental anatomy and diminutive body size of Fruitadens suggest that this taxon was an ecological generalist with an omnivorous diet, thus providing new insights into morphological and palaeoecological diversity within Dinosauria. Late-surviving (Late Jurassic and Early Cretaceous) heterodontosaurids are smaller and less ecologically specialized than Early (Late Triassic and Early Jurassic) heterodontosaurids, and this ecological generalization may account in part for the remarkable 100-million-year-long longevity of the clade.
Etymology
Fruitadens, from Fruita (hypodigmlocality) and dens (Latin, tooth); haagarorum, for Paul Haaga, Jr, Heather Haaga, Blythe Haaga, Paul Haaga III and Catalina Haaga, to honour their support of the Natural History Museum of Los Angeles County (LACM, Los Angeles, USA).
Holotype
LACM 115747, associated jaws, vertebrae and limb bones of a nearly full-grown individual; includes incomplete maxillae and dentaries, disarticulated vertebrae including cervicals, dorsals, six sacral vertebrae and caudals, proximal end of the right femur, both ends of both tibiae, and partial right metatarsal I.
Referred material
LACM 115727, nearly full-grown individual, fragmentary cervical, dorsal and caudal vertebrae, partial femora, and partial tibiae with articulated astragalus/calcaneum LACM 120478, juvenile individual, left humerus, partial left femur, and articulated left tibia, fibula and astragalus/ calcaneum LACM 128258, juvenile individual, right premaxilla, partial left maxilla, dentaries, dorsal vertebra, distal caudal vertebra
Horizon and locality
The base of the Brushy Basin Member of the Morrison Formation (Late Jurassic: early Tithonian) at the LACM Fruita Paleontological Area, northwest of Grand Junction, Colorado, USA (figure 1 and figure S1 in the electronic supplementary material; Kirkland 2006).
Diagnosis
Small heterodontosaurid ornithischian characterized by the following unique combination of characters, including autapomorphies (indicates character that is autapomorphic within Heterodontosauridae; indicates character that is autapomorphic within Ornithischia): (premaxillary crowns small and subequal in size, expanded labiolingually and mesiodistally above the root; maxillary caniniform absent; (axillary/dentary crowns low and triangular, with symmetrically distributed enamel; denticles extend over half of the maxillary/dentary crowns, not restricted to apical third; dentary caniniform present but apicobasal height does not exceed that of the largest dentary cheek tooth crown; small, unserrated, peg-like and procumbent tooth present anterior to the dentary caniniform; distal end of the tibia with anteromedial flange; apex of the ascending process of astragalus is formed by a separate ossification; two large foramina pierce anterior surface of the ascending process of astragalus