|A more naturalistic stance. NPS photo of the Carnegie's new mount.|
On to the guest of honor, Eousdryosaurus:
- Genus and species: Eousdryosaurus nanohallucis, the genus name meaning "eastern Dryosaurus" in reference to this dinosaur being a Dryosaurus-like animal on the east side of what was then a young Atlantic ocean, and the species name referring to the reduced hallux, or big toe
- Citation: Escaso, F., F. Ortega, P. Dantas, E. Malafaia, B. Silva, J. M. Gasulla, P. Mocho, I. Narváez, and J. L. Sanz (2014). A new dryosaurid ornithopod (Dinosauria, Ornithischia) from the Late Jurassic of Portugal. Journal of Vertebrate Paleontology 34(5):1102–1112.
- Stratigraphy and geography: Praia da Amoreira-Porto Novo Member of the Alcobaça Formation, upper Kimmeridgian Stage (Upper Jurassic), Porto das Barcas, Lourinhã, west-central Portugal
- Holotype: SHN(JJS)-170 (Sociedade de História Natural, Torres Vedras, Portugal), a partially articulated specimen including the last sacral (hip) vertebra, the first eight tail vertebrae and their chevrons, the left ilium (the main bone of a dinosaur hip, usually being substantially longer than tall and forming roughly the upper half of the hip socket), the left hind leg, and the right thigh bone (femur).
So, how does Eousdryosaurus fit in with the other dryosaurids? Conveniently, it is known from leg and pelvic remains, which means it is comparable with practically all other dryosaurids. The type individual seems to be a bit on the small side, estimated around 1.6 m long, appropriate for an immature Dryosaurus or Dysalotosaurus (curiously, dryosaurids seem to have had different growth patterns than other dinosaurs, and experienced indeterminate growth; we don't have evidence for skeletally "adult" examples of Dryosaurus or Dysalotosaurus [Horner et al. 2009; Hübner 2012]). Eousdryosaurus differed from other dryosaurids in a number of skeletal details. The feature that inspired its species name is the greatly reduced "big toe"; there's only a metatarsal and a single lonely phalanx bone. Most ornithopods either had two phalanges or eliminated this toe altogether.
Below is a sort of "flash card" for known dryosaurids, providing a quick reference to the time and place (you'll have to click to expand). I've been toying with doing something like this for a while; the continents are easy, but geologic ages tend to vary between publications over decades: formation ages become better refined, they occasionally move up or down a stage, and the dating of the stages has changed over time. No, Kangnasaurus did not exist over 45 million years; there's just poor age constraint on the rocks it was found in.
|Click to embiggen; it expands like one of those spongesaurs.|
Escaso, F., F. Ortega, P. Dantas, E. Malafaia, B. Silva, J. M. Gasulla, P. Mocho, I. Narváez, and J. L. Sanz (2014). A new dryosaurid ornithopod (Dinosauria, Ornithischia) from the Late Jurassic of Portugal. Journal of Vertebrate Paleontology 34(5):1102–1112.
Horner, J. R., A. de Ricql es, K. Padian, and R. D. Scheetz. 2009. Comparative long bone histology and growth of the ‘hypsilophodontid’ dinosaurs Orodromeus makelai, Dryosaurus altus, and Tenontosaurus tillettii (Ornithischia: Euornithopoda). Journal of Vertebrate Paleontology 29:734–747.
Hübner, T. R. 2012. Bone histology in Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia)—variation, growth, and implications. PLoS ONE 7:e29958. doi: 10.1371/journal.pone.0029958.
Mateus, O. 2006. Late Jurassic dinosaurs from the Morrison Formation, the Lourinhã and Alcobaça Formations (Portugal), and the Tendaguru Beds (Tanzania): a comparison. New Mexico Museum of Natural History and Science Bulletin 36:223–231.