''Eousdryosaurus'' ("eastern ''

Dryosaurus ''Dryosaurus'' ( , meaning 'tree lizard', Greek ' () meaning 'tree, oak' and () meaning 'lizard'; the name reflects the forested habitat, not a vague oak-leaf shape of its cheek teeth as is sometimes assumed) is a genus of an ornithopod dinosaur ...

''") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

basal Basal or basilar is a term meaning ''base'', ''bottom'', or ''minimum''. Science * Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure * Basal (medicine), a minimal level that is nec ...

iguanodontia Iguanodontia (the iguanodonts) is a clade of herbivorous dinosaurs that lived from the Middle Jurassic to Late Cretaceous. Some members include ''Camptosaurus'', '' Dryosaurus'', '' Iguanodon'', '' Tenontosaurus'', and the hadrosaurids or "duck- ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

known from a partial skeleton discovered in

Upper Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

rocks in western

Portugal Portugal, officially the Portuguese Republic, In recognized minority languages of Portugal: :* mwl, República Pertuesa is a country located on the Iberian Peninsula, in Southwestern Europe, and whose territory also includes the Macaronesian ...

. The type, and only species, is ''Eousdryosaurus nanohallucis'', named and described in 2014.

Discovery and naming

''Eousdryosaurus'' is based on SHN(JJS)-170, kept in the Sociedade de História Natural in

Torres Vedras Torres Vedras () is a municipality in the Portuguese district of Lisbon, approximately north of the capital Lisbon in the Oeste region, in the Centro of Portugal. The population was 83,075, in an area of . History In 1148, Afonso I too ...

, Portugal. The articulated and well-preserved specimen includes a

hip In vertebrate anatomy, hip (or "coxa"Latin ''coxa'' was used by Celsus in the sense "hip", but by Pliny the Elder in the sense "hip bone" (Diab, p 77) in medical terminology) refers to either an anatomical region or a joint. The hip region ...

vertebra and eight

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characterist ...

e from the

proximal Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position ...

part of the tail, their

chevrons Chevron (often relating to V-shaped patterns) may refer to: Science and technology * Chevron (aerospace), sawtooth patterns on some jet engines * Chevron (anatomy), a bone * '' Eulithis testata'', a moth * Chevron (geology), a fold in rock l ...

, the left

ilium Ilium or Ileum may refer to: Places and jurisdictions * Ilion (Asia Minor), former name of Troy * Ilium (Epirus), an ancient city in Epirus, Greece * Ilium, ancient name of Cestria (Epirus), an ancient city in Epirus, Greece * Ilium Building, a ...

, the entire left leg, and the right

thigh bone The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with t ...

(femur). These bones were discovered in

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

of the late

Kimmeridgian In the geologic timescale, the Kimmeridgian is an age in the Late Jurassic Epoch and a stage in the Upper Jurassic Series. It spans the time between 157.3 ± 1.0 Ma and 152.1 ± 0.9 Ma (million years ago). The Kimmeridgian follows the Oxford ...

-age (

late Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the ...

, approximately 152 million years old) Praia da Amoreira-Porto Novo Member of the

Lourinhã Formation The Lourinhã Formation () is a fossil rich geological formation in western Portugal, named for the municipality of Lourinhã. The formation is mostly Late Jurassic in age (Kimmeridgian/Tithonian), with the top of the formation extending into the ...

Porto das Barcas Porto or Oporto () is the second-largest city in Portugal, the capital of the Porto District, and one of the Iberian Peninsula's major urban areas. Porto city proper, which is the entire municipality of Porto, is small compared to its metropo ...

Lourinhã Lourinhã () is a municipality in the District of Lisbon, in the Oeste Subregion of Portugal. The population in 2011 was 25,735, in an area of 147.17 km². The seat of the municipality is the town of Lourinhã, with a population of 8,800 inhab ...

, Portugal. The genus name is a reference to ''Eousdryosaurus'' being a relative of ''Dryosaurus'' on the east side of the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth#Surface, Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Afr ...

. The

type Type may refer to: Science and technology Computing * Typing, producing text via a keyboard, typewriter, etc. * Data type, collection of values used for computations. * File type * TYPE (DOS command), a command to display contents of a file. * Ty ...

and only

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

is ''E. nanohallucis'', meaning "small

hallux Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''pla ...

", in reference to the small size of that toe. ''Eousdryosaurus'' was named in 2014 by Fernando Escaso and colleagues, after having been described briefly in 2000.

Description

The only known individual of ''Eousdryosaurus'' was a small dryosaurid, estimated at in length, comparable to immature individuals of ''

'' and ''

Dysalotosaurus ''Dysalotosaurus'' ("uncatchable lizard") is a genus of herbivorous iguanodontian dinosaur. It was a dryosaurid iguanodontian, and its fossils have been found in late Kimmeridgian-age rocks (Late Jurassic) of the Tendaguru Formation of Lindi Reg ...

''. The right femur measures long and the left shin bone (

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

) measures long. It is differentiated from other dryosaurids by various details of the vertebrae, hip, and hind limb. The foot is unique among

ornithopod Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (), that started out as small, bipedal running grazers and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous worl ...

s in that the first digit (the hallux or big toe) includes a single

phalanx bone The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones ...

; most basal ornithopods had two phalanges, and most derived ornithopods, including

hadrosaurs Hadrosaurids (), or duck-billed dinosaurs, are members of the ornithischian family Hadrosauridae. This group is known as the duck-billed dinosaurs for the flat duck-bill appearance of the bones in their snouts. The ornithopod family, which inclu ...

("duckbills"), lost this digit.

Classification

Escaso ''et al.'' performed a

phylogenetic analysis In biology Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that pro ...

and found ''Eousdryosaurus'' to be a basal

dryosaurid Dryosaurids were primitive iguanodonts. They are known from Middle Jurassic to Early Cretaceous rocks of Africa, Europe, and North America. Phylogeny Until recently many dryosaurids have been regarded as dubious (''Callovosaurus'' and ''Kangnas ...

, a type of small

bipedal Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...

herbivore A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthp ...

near the base of

Iguanodontia Iguanodontia (the iguanodonts) is a clade of herbivorous dinosaurs that lived from the Middle Jurassic to Late Cretaceous. Some members include ''Camptosaurus'', '' Dryosaurus'', '' Iguanodon'', '' Tenontosaurus'', and the hadrosaurids or "duck- ...

. On the other hand, Dieudonné ''et al.'' (2020) found ''Eousdryosaurus'' to be a sister taxon to the

Elasmaria Elasmaria is a clade of ornithopods known from Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At ...

References

{{Taxonbar, from=Q18061165 Iguanodonts Kimmeridgian life Late Jurassic dinosaurs of Europe Jurassic Portugal Fossils of Portugal Lourinhã Formation Fossil taxa described in 2014 Ornithischian genera