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EOUSDRYOSAURUS

a plant-eating dryosaurid ornithopod dinosaur from the Late Jurassic of Portugal.
eousdryosaurus.png
Pronunciation: yuss-dry-o-sor-us
Meaning: Eastern Dryosaurus
Author/s: Escaso et al. (2014)
Synonyms: None known
First Discovery: Lourinhã, Portugal
Chart Position: 724

Eousdryosaurus nanohallucis

Small ornithopods were shy unassuming critters in life, spending most of their day trying to avoid being squished or eaten by the giant dinosaurs that surrounded them. And they're afforded precious little attention in death 'cos they don't have sharp teeth, terrorize herbivores or weigh thirty tons and thus aren't headline-makers. A prime example is Eousdryosaurus, which was about average size, average weight and average build for a member of the average ornithopods known as dryosaurids. However, it's the first representative of Dryosauridae ever found in the Iberian Penninsula and the only one known from the Eastern side of the Atlantic, hence the name. But those facts were so utterly underwhelming that paleontologists dragged their heels for 14 years before christening its remains. And since then it's acted like a complete media tart by shamelessly thrusting its hallux into the limelight. Sometimes you have to make your own headlines.

With a hallux (big toe) that has shrunk to a splint and sports just one phalanx (toe bone), the "big toe" of Eousdryosaurus is only a shadow of the toe that it used to be. Basal ornithopods had four weight-bearing toes amongst which the big toe was made up of two phalanges (plural of phalanx), while the more derived ornithopods, including the duck-billed hadrosaurids, lost this digit altogether. Eousdryosaurus and its diddy single-boned hallux, then, appears to sit somewhere between the former and the latter, and represents an evolutionary step, perhaps the last step, from four to three toed-ness in ornithischian dinosaurs.

Dryosaurids in general are around two to three meters in length, with short arms, a small skull with a stumpy snout and beetle brow, and leaf-shaped teeth. A finger-like bone (the fourth trochanter) and a trench on the rear of their thigh bones anchored a muscle that was also attached to the base of a disproportionately large tail, and this lump of meat (known as the caudofemoralis) combined with massive hind legs are what made dryosaurids some of the swiftest dinosaurs.
(Eastern Dryosaurus with a small hallux)Etymology
Eousdryosaurus is derived from the Latin "eous" (of the east, eastern, orient), and the Greek "drys" (tree) and "sauros" (lizard) in reference to Eousdryosaurus being a relative of Dryosaurus ("tree lizard") on the east side of the Atlantic Ocean. The species epithet, nanohallucis, is derived from the Latin "nanus" (dwarf) and "halluxcis" ("of the great toe") referring to the small size of its "big" toe (aka the hallux).
Discovery
The remains of Eousdryosaurus were discovered in the Praia da Amoreira-Porto Novo Member of the Alcobaça Formation, at the foot of a cliff near the town of Porto das Barcas, Lourinhã, Portugal, in 1999 by a fossil-collecting carpenter called Jose Joaquim dos Santos who sold them to Torres Vedras Council. The holotype (SHN(JJS)-170) includes a hip vertebra, eight tail vertebrae and their chevrons, the left ilium (a hip bone), the entire left leg, and the right femur (thigh), belonging to a sub-adult.
Estimations
Timeline:
Era: Mesozoic
Epoch: Late Jurassic
Stage: Kimmeridgian
Age range: 156-151 mya
Stats:
Est. max. length: 2 meters
Est. max. hip height: 0.6 meters
Est. max. weight: 75 Kg
Diet: Herbivore
Family Tree:
Dinosauria
Ornithischia
Cerapoda
Ornithopoda
Iguanodontia
Dryosauridae
Eousdryosaurus
nanohallucis
References
• Escaso F, Ortega F, Dantas P, Malafaia E, Silva B, Gasulla J.M, Mocho P, Narváez I. and Sanz J.L. (2014) "A new dryosaurid ornithopod (Dinosauria, Ornithischia) from the Late Jurassic of Portugal".
• Dantas P.P, Yagüe C.J, Hazevoet F, Ortega V, dos Santos J.L, Sanz M, Cachão A.M. and Santos J.J. (2000) "Estudo preliminar de um novo Iguanodontia basal do Jurássico Superior Portugûes".
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To cite this page:
Atkinson, L. "EOUSDRYOSAURUS :: from DinoChecker's dinosaur archive".
›. Web access: 25th Nov 2017.
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