''Genusaurus'' ( ; meaning "knee lizard") 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 nom ...

of abelisauroid

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 ...

from the Early Cretaceous. Its fossils were found in

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of overseas regions and territories in the Americas and the Atlantic, Pacific and Indian Oceans. Its metropolitan area ...

. ''Genusaurus'' is believed to have lived during the

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0 ...

stage Stage or stages may refer to: Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly British theatre newspaper * Sta ...

, around 112-100 million years ago.

Description

''Genusaurus'' possesses several distinguishing traits. The dorsal vertebrae are elongated. The elements of the pelvis are strongly fused. The thighbone shows a low bone plateau below the major trochanter; to the front an accessory trochanter is present. The epicondyle of the inner femoral condyle is well-developed. The cnemial crest strongly extends to the front and is curved upwards. The fibula has a distinctive boss serving as an attachment for the '' Musculus iliofibularis''. The upper inner side of the fibula is strongly hollowed out.

Size

''Genusaurus'' was originally estimated to have been long. From the thighbone, a weight of was extrapolated. Later estimates, while confirming the length of , have reduced the weight to , or even . In 2016, its length was estimated at , making it the smallest abelisaurid.

Discovery and naming

The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...

, ''Genusaurus sisteronis'', is the only named species. It is based on a partial skeleton found in 1984-1986 in the Albian Bevons Beds,

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...

MNHN Bev.1. The holotype contains seven partial dorsal vertebrae, a piece of a sacral, a piece of an ilium, the top of a

pubic bone In vertebrates, the pubic region ( la, pubis) is the most forward-facing ( ventral and anterior) of the three main regions making up the coxal bone. The left and right pubic regions are each made up of three sections, a superior ramus, inferior ...

, a thighbone, the top of a shinbone, the top of a fibula and a

metatarsal The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes. Lacking individual names, the metatarsal bones are numbered from the me ...

. It was named and described by Hugues Accarie, Bernard Beaudoin, Jean Dejax, Gérard Friès, Jean-Guy Michard and

Philippe Taquet Philippe Taquet (b. April 25, 1940 Saint-Quentin, Aisne) 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, president ...

in 1995.Accarie, H., B. Beaudoin, J. Dejax, G. Fries, J.C. Michard, and P. Taquet (1995). "Découverte d'un Dinosaure théropode nouveau (''Genusaurus sisteronis n. g., n. sp''.) dans l'Albien marin de Sisteron (Alpes de Haute-Provence, France) et extension au Crétacé inférieur de la lignée cératosaurienne". ''Compte rendu hebdomadaire des scéances de l'Académie des Sciences à Paris''. 320 (2): 327-334
Translation into English.
/ref> The genus name is derived from the Latin word ''genu'' (knee) and refers to the

cnemial crest The cnemial crest is a crestlike prominence located at the front side of the head of the tibiotarsus or tibia in the legs of many mammals and reptiles (including birds and other dinosaurs). The main extensor muscle of the thigh In human anat ...

in front of the proximal end of the

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 ...

. The specific name refers to

Sisteron Sisteron (; , oc, label=Mistralian norm, Sisteroun; from oc, label=Old Occitan, Sestaron) is a commune in the Alpes-de-Haute-Provence department, Provence-Alpes-Côte d'Azur, southeastern France. Sisteron is situated on the banks of the rive ...

, the town near which the specimen was found.

Classification

Accarie ''et al.'' assigned ''Genusaurus'' to the

ceratosaur Ceratosaurs are members of the clade Ceratosauria, a group of dinosaurs defined as all theropods sharing a more recent common ancestor with ''Ceratosaurus'' than with birds. The oldest known ceratosaur, ''Saltriovenator'', dates to the earlies ...

group of

theropods Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ca ...

, more precisely to the

Coelophysoidea Coelophysoidea were common dinosaurs of the Late Triassic and Early Jurassic periods. They were widespread geographically, probably living on all continents. Coelophysoids were all slender, carnivorous forms with a superficial similarity to the ...

. A 2008

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

analysis by Carrano and

Sampson Sampson may refer to: Military * , several Royal Navy ships * , several US Navy ships * Sampson-class destroyer, a World War I US Navy class * Sampson Air Force Base, near Seneca Lake, New York, closed in 1956 * SAMPSON, a multi-function radar ...

placed ''Genusaurus'' in the

Noasauridae Noasauridae is an extinct family of theropod dinosaurs belonging to the group Ceratosauria. They were closely related to the short-armed abelisaurids, although most noasaurids had much more traditional body types generally similar to other th ...

along with ''

Laevisuchus ''Laevisuchus'' (, "light crocodile") is a genus of theropod dinosaur from the Late Cretaceous. Its remains were discovered by Charles Alfred Matley near Jabalpur in Maastrichtian deposits in the Lameta Formation in India, and were named and de ...

'', ''

Masiakasaurus ''Masiakasaurus'' is a genus of small predatory noasaurid theropod dinosaurs from the Late Cretaceous of Madagascar. In Malagasy, ''masiaka'' means "vicious"; thus, the genus name means "vicious lizard". The type species, ''Masiakasaurus knopfl ...

'', '' Noasaurus'', and ''

Velocisaurus ''Velocisaurus'' ("swift lizard") is a genus of noasaurid theropod dinosaur from the Late Cretaceous period of Argentina. Description ''Velocisaurus'' was probably around long, based on a tibia length of . This makes it the smallest noasaur ...

''; in turn, noasaurids are part of the

Abelisauroidea Abelisauroidea is typically regarded as a Cretaceous group, though the earliest abelisauridae remains are known from the Middle Jurassic of Argentina (classified as the species Eoabelisaurus mefi) and possibly Madagascar (fragmentary remains of ...

group, which is part of the ceratosaur group. Subsequent phylogenetic analyses found ''Genusaurus'' to be a member of the

Abelisauridae Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are fou ...

, specifically the

Majungasaurinae Majungasaurinae (after ''Majungasaurus'', itself named after the city of Mahajanga in Madagascar) is a subfamily of large carnivorous theropods from the Upper Cretaceous, found in Madagascar, India, and France. It is a subgroup within the thero ...

References

External links

"Our Exhibitions: ''Genusaurus sisteronis''" (in French)
at the Réserve Naturelle Géologique de Haute-

Provence Provence (, , , , ; oc, Provença or ''Prouvènço'' , ) is a geographical region and historical province of southeastern France, which extends from the left bank of the lower Rhône to the west to the Italian border to the east; it is bor ...