Eousdryosaurus

Eousdryosaurus ("eastern Dryosaurus") is a genus of basal iguanodontian dinosaur known from a partial skeleton discovered in Upper Jurassic rocks in western Portugal. The type, and only species, is Eousdryosaurus nanohallucis, named and described in 2014.

Eousdryosaurus
Temporal range: Late Jurassic,
152 Ma
↓
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: †Ornithischia
Suborder: †Ornithopoda
Family: †Dryosauridae
Genus: †Eousdryosaurus
Escaso et al., 2014
Species:
†E. nanohallucis
Binomial name
†Eousdryosaurus nanohallucis
Escaso et al., 2014

Discovery and naming

Eousdryosaurus is based on SHN(JJS)-170, kept in the Sociedade de História Natural in Torres Vedras, Portugal. The articulated and well-preserved specimen includes a hip vertebra and eight vertebrae from the proximal part of the tail, their chevrons, the left ilium, the entire left leg, and the right thigh bone (femur). These bones were discovered in sandstone of the late Kimmeridgian-age (late Jurassic, approximately 152 million years old) Praia da Amoreira-Porto Novo Member of the Lourinhã Formation in Porto das Barcas, Lourinhã, Portugal. The genus name is a reference to Eousdryosaurus being a relative of Dryosaurus on the east side of the Atlantic Ocean. The type and only species is E. nanohallucis, meaning "small hallux", in reference to the small size of that toe.[1] Eousdryosaurus was named in 2014 by Fernando Escaso and colleagues,[1] after having been described briefly in 2000.[2]

Description

The only known individual of Eousdryosaurus was a small dryosaurid, estimated at 1.6 metres (5.2 ft) in length, comparable to immature individuals of Dryosaurus and Dysalotosaurus. The right femur measures 188.5 millimetres (7.42 in) long and the left shin bone (tibia) measures 200 millimetres (7.9 in) long.[1]

It is differentiated from other dryosaurids by various details of the vertebrae, hip, and hind limb. The foot is unique among ornithopods in that the first digit (the hallux or big toe) includes a single phalanx bone; most basal ornithopods had two phalanges, and most derived ornithopods, including hadrosaurs ("duckbills"), lost this digit.[1]

Classification

Escaso et al. performed a phylogenetic analysis and found Eousdryosaurus to be a basal dryosaurid, a type of small bipedal herbivore near the base of Iguanodontia.[1]

References
  1. Escaso, F.; F. Ortega, P. Dantas; E. Malafaia, B. Silva; J. M. Gasulla, P. Mocho & I. Narváez, J. L. Sanz (2014). "A new dryosaurid ornithopod (Dinosauria, Ornithischia) from the Late Jurassic of Portugal". Journal of Vertebrate Paleontology. 34 (5): 1102–1112. doi:10.1080/02724634.2014.849715.
  2. Dantas, P. P.; C. J. Yagüe, F. Hazevoet; V. Ortega, J. L. dos Santos; M. Sanz, A. M. Cachão & de Carvalho Galopim, J. J. Santos (2000). "Estudo preliminar de um novo Iguanodontia basal do Jurássico Superior Portugûes". In J. B. Diez & A. C. Balbino (eds.). Livro de Resumos do I Congresso Ibérico de Paleontologia/XVI Jornadas de la Sociedad Española de Paleontología, Évora (Portugal), 12–14 Outubro 2000. Évora, Portugal: Universidade de Évora. pp. 12–13.
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