Open Paleo

Fruitadens

Butler et al., 2010 FRU-tah-denz

From Fruita (the city of Fruita, Colorado, USA, where fossils were found) + Latin dens (tooth): 'Fruita teeth'.

154.8–149.2 million years ago Kimmeridgian, Late Jurassic
Late Jurassic stages

Fruitadens is a genus of heterodontosaurid dinosaur. The name means "Fruita teeth", in reference to Fruita, Colorado (USA), where its fossils were first found. It is known from partial skulls and skeletons from at least four individuals of differing biological ages, found in Tithonian (Late Jurassic) rocks of the Morrison Formation in Colorado. Fruitadens is one of the smallest known ornithischian dinosaur, with young adults estimated at 65 to 75 cm (26 to 30 in) in length and 0.5 to 0.75 kg (1.1 to 1.7 lb) in weight. It is interpreted as an omnivore and represents one of the latest-surviving heterodontosaurids.

Diagnosis

  1. Premaxillary crowns small and subequal in size, expanded labiolingually and mesiodistally above the root (autapomorphic within Heterodontosauridae).
  2. Denticles extend over half of the maxillary/dentary crowns, not restricted to apical third (autapomorphic within Heterodontosauridae).
  3. Dentary caniniform present but apicobasal height does not exceed that of the largest dentary cheek tooth crown (autapomorphic within Ornithischia).
  4. Small, unserrated, peg-like and procumbent tooth present anterior to the dentary caniniform (autapomorphic within Ornithischia).
  5. Distal end of tibia with anteromedial flange (autapomorphic within Ornithischia).
  6. Apex of ascending process of astragalus formed by a separate ossification; two large foramina pierce anterior surface of ascending process (autapomorphic within Ornithischia).

Species

Fruitadens haagarorum Butler et al., 2010

Type species

Named for Paul Haaga Jr., Heather Haaga, Blythe Haaga, Paul Haaga III, and Catalina Haaga, in recognition of their support for the Natural History Museum of Los Angeles County.

Holotype
LACM 115747 , Natural History Museum of Los Angeles County
Material
Associated jaws, vertebrae and limb bones of a nearly full-grown individual; incomplete maxillae and dentaries, disarticulated vertebrae including cervicals, dorsals, six sacral vertebrae and caudals, proximal end of right femur, both ends of both tibiae, and partial right metatarsal I.
Horizon
lower Brushy Basin Member, Morrison Formation, Kimmeridgian, Late Jurassic , 154.8–149.2 million years ago
Locality
Fruita Paleontological Area, Colorado, United States Butler and colleagues (2010) place the holotype at "The base of the Brushy Basin Member of the Morrison Formation (Late Jurassic: early Tithonian)" in the Fruita Paleontological Area. Sombathy and colleagues (2025) date that area at "ca. 152–150 Ma", and Chure and Loewen (2020) the base of the Brushy Basin at a recalibrated 152.77 ± 0.3 Ma, both Kimmeridgian on the ICS chart v2024/12.

References

  1. Butler, R. J.; Galton, P. M.; Porro, L. B.; Chiappe, L. M.; Henderson, D. M.; Erickson, G. M. (2010). Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America. Proceedings of the Royal Society B: Biological Sciences 277(1680): 375-381. The Royal Society. doi:10.1098/rspb.2009.1494 butler2010a
  2. Sombathy, R.; O'Connor, P. M.; D'Emic, M. D. (2025). Osteohistology of the unusually fast-growing theropod dinosaur Ceratosaurus. Journal of Anatomy 247(3-4): 765-789. doi:10.1111/joa.14186

    Dates the Fruita Paleontological Area at about 152 to 150 Ma.

    sombathy2025a
  3. Chure, D. J.; Loewen, M. A. (2020). Cranial anatomy of Allosaurus jimmadseni, a new species from the lower part of the Morrison Formation (Upper Jurassic) of Western North America. PeerJ 8: e7803. doi:10.7717/peerj.7803

    Gives a recalibrated 152.77 Ma for the base of the Brushy Basin Member.

    chure2020a