Elrhazosaurus is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of basal

Basal (phylogenetics)

In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...

 iguanodontian dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

, known from isolated bones found in Lower Cretaceous rocks of Niger

Niger

Niger , officially named the Republic of Niger, is a landlocked country in Western Africa, named after the Niger River. It borders Nigeria and Benin to the south, Burkina Faso and Mali to the west, Algeria and Libya to the north and Chad to the east...

. These bones were initially thought to belong to a species of the related dryosaurid

Dryosauridae

Dryosaurids were primitive iguanodonts. They are known from Middle Jurassic to Early Cretaceous rocks of Africa, Europe, and North America.-Phylogeny:...

 Valdosaurus

Valdosaurus

Valdosaurus is a genus of bipedal herbivorous iguanodont ornithopod dinosaur found on the Isle of Wight and elsewhere in England. It lived during the Early Cretaceous.-Discovery and naming:...

, but have since been reclassified.

Discovery and history

Elrhazosaurus is based on

Holotype

A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

 MNHN

Muséum national d'histoire naturelle

The Muséum national d'Histoire naturelle is the National Museum of Natural History in Paris, France.- History :The museum was formally founded on 10 June 1793, during the French Revolution...

 GDF 332, a left thigh bone

Femur

The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

 collected by Philippe Taquet

Philippe Taquet

Philippe Taquet is a French paleontologist who specializes in dinosaur systematics of finds primarily in northern Africa.He is a member of the French Academy of Sciences since November 30, 2004...

 from the upper part of the Elrhaz Formation

Elrhaz Formation

The Elrhaz Formation is a geological formation in Niger whose strata date back to the Early Cretaceous...

 of Gadoufaoua

Gadoufaoua

Gadoufaoua is a site in the Tenere desert of Niger known for its extensive fossil graveyard, where remains of Sarcosuchus imperator, popularly known as SuperCroc, have been found , including vertebrae, limb bones, armor plates, jaws, and a nearly complete 6-foot skull.Gadoufaoua is very hot...

 in the Ténéré Desert

Ténéré

The Ténéré is a desert region in the south central Sahara. It comprises a vast plain of sand stretching from northeastern Niger into western Chad, occupying an area of over...

, Agadez, Niger. This rock unit dates to the late Aptian

Aptian

The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...

 stage, approximately 115 million years ago. The bone was designated as the type specimen of a new species of Valdosaurus

Valdosaurus

Valdosaurus is a genus of bipedal herbivorous iguanodont ornithopod dinosaur found on the Isle of Wight and elsewhere in England. It lived during the Early Cretaceous.-Discovery and naming:...

(V. nigeriensis) by Peter Galton

Peter Galton

Peter M. Galton is a British vertebrate paleontologist working in America, who has to date written or co-written about a hundred papers in scientific journals or chapters in paleontology textbooks, especially on ornithischian and prosauropod dinosaurs.With Robert Bakker in a joint article...

 and Taquet in 1982. It was differentiated from the type species

Type species

In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 V. canaliculatus by the locations of trochanter

Trochanter

In human anatomy, the trochanter is a part of the thigh bone. It can refer to:* Greater trochanter* Lesser trochanter* Third trochanter-See also:* Intertrochanteric crest* Intertrochanteric line...

s and other details. Because V. canaliculatus is known from Europe, the presence of a related species in central Africa was interpreted as evidence for a land connection between the two continents.

V. nigeriensis was given its own genus, Elrhazosaurus, by Galton in 2009. This was done on the grounds of differing morphology

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

 and geologic age versus V. canaliculatus. He retained it as a dryosaurid. While Elrhazosaurus is sometimes described as only known from thigh bones, at least one upper arm

Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....

 bone has been assigned to the genus.

Paleoecology and paleobiology

The Elrhaz Formation is mostly made up of fluvial

River

A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...

 sandstone

Sandstone

Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...

s. A diverse assemblage of fossil animals has been recovered, including freshwater bivalves

Bivalvia

Bivalvia is a taxonomic class of marine and freshwater molluscs. This class includes clams, oysters, mussels, scallops, and many other families of molluscs that have two hinged shells...

, hybodont

Hybodontidae

Hybodontidae is an extinct family of sharks, first appearing in the Mississippian period, and disappearing during the Miocene....

 sharks, bony fish, turtles, several genera of crocodylomorphs

Crocodylomorpha

The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...

 (Anatosuchus

Anatosuchus

Anatosuchus is an extinct genus of notosuchian crocodylomorph discovered in Gadoufaoua, Niger, and described by a team of palaeontologists led by the American Paul Sereno in 2003, in the Journal of Vertebrate Paleontology...

, Araripesuchus

Araripesuchus

Araripesuchus is a genus of extinct crocodyliform whose species existed during the Cretaceous period of the late Mesozoic era some 125 to 65 million years ago. They are generally considered to be notosuchians , characterized by their varied teeth types and distinct skull elements...

, Sarcosuchus

Sarcosuchus

Sarcosuchus is an extinct genus of crocodyliform and distant relative of the crocodile that lived 112 million years ago. It dates from the early Cretaceous Period of what is now Africa and is one of the largest giant crocodile-like reptiles that ever lived...

, and Stolokrosuchus

Stolokrosuchus

Stolokrosuchus is an extinct genus of neosuchian crocodylomorph that lived during the Early Cretaceous. Its fossils, including a skull with a long thin snout and bony knobs on the prefontals, have been found in Niger. Stolokrosuchus was described in 2000 by Hans Larsson and Boubacar Gado. The...

), undescribed ornithocheirid

Ornithocheiridae

Ornithocheiridae is a group of pterosaurs within the suborder Pterodactyloidea. They were among the last pterosaurs to possess teeth.-Classification:Listing of genera after Unwin , except where noted.* Family Ornithocheiridae** ?Aetodactylus...

 pterosaur

Pterosaur

Pterosaurs were flying reptiles of the clade or order Pterosauria. They existed from the late Triassic to the end of the Cretaceous Period . Pterosaurs are the earliest vertebrates known to have evolved powered flight...

s, the theropod

Theropoda

Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...

 dinosaurs Eocarcharia

Eocarcharia

Eocarcharia is a genus of carcharodontosaurid theropod dinosaur from the Early Cretaceous Elrhaz Formation that lived in the Sahara 112 million years ago, in what today is the country of Niger. It was discovered in 2000 on an expedition led by University of Chicago paleontologist Paul Sereno. The...

, Kryptops

Kryptops

Kryptops is a genus of abelisaurid theropod dinosaur from the Early Cretaceous of Niger. It is known from a partial skeleton found at the Gadoufaoua locality in the western Ténéré Desert, in rocks of the Aptian-Albian age Elrhaz Formation...

, Suchomimus

Suchomimus

Suchomimus is a genus of large spinosaurid dinosaur with a crocodile-like mouth that lived sometime between 121-112 million years ago, during the late Aptian stage of the Cretaceous period in Africa.-Description:...

, and an undescribed noasaurid

Noasauridae

Noasaurids were a group of theropod dinosaurs from the Cretaceous Period . They were generally small in size...

, the sauropods Nigersaurus

Nigersaurus

Nigersaurus is a genus of diplodocoid sauropod dinosaur from the middle Cretaceous period, about 119 to 99 million years ago during the Aptian or Albian age. This dinosaur was described by Paul Sereno and colleagues in 1999...

and an undescribed titanosaur

Titanosaur

Titanosaurs were a diverse group of sauropod dinosaurs, which included Saltasaurus and Isisaurus. It includes some of the heaviest creatures ever to walk the earth, such as Argentinosaurus and Paralititan — which some believe have weighed up to 100 tonnes...

ian, and the iguanodontians Lurdusaurus

Lurdusaurus

Lurdusaurus is a genus of large ornithopod dinosaur which lived in the Aptian stage of the Early Cretaceous, sometime between 121 to 112 million years ago.-Discovery and naming:...

and Ouranosaurus

Ouranosaurus

Ouranosaurus is an unusual genus of herbivorous iguanodont dinosaur that lived during the early Cretaceous about 110 million years ago in what is now Africa. Ouranosaurus measured about seven to eight meters long...

. As a dryosaurid iguanodontian, Elrhazosaurus would have been a lightly built herbivorous

Herbivore

Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...

 bipedal runner

Cursorial

Cursorial is a biological term that describes an organism as being adapted specifically to run. It is typically used in conjunction with an animal's feeding habits or another important adaptation. For example, a horse can be considered a "cursorial grazer", while a wolf may be considered a...

.