''Rayososaurus'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of plant-eating

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their bo ...

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 ...

of the superfamily

Diplodocoidea Diplodocoidea is a superfamily of sauropod dinosaurs, which included some of the longest animals of all time, including slender giants like ''Supersaurus'', ''Diplodocus'', ''Apatosaurus'', and ''Amphicoelias''. Most had very long necks and long, ...

. It was found in the

Candeleros Formation The Candeleros Formation (formerly known as the Candeleros Member of the "Río Limay Formation") is a geologic formation that crops out in the Río Negro, Neuquén, and Mendoza provinces of northern Patagonia, Argentina. It is the oldest formati ...

, but was named ''Rayososaurus'' after the Rayoso Member, which later has been elevated to the older

Rayoso Formation The Rayoso Formation is a geological formation in the Neuquén Province of Argentina whose strata date back to the Aptian-Albian stages of the Early Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.Weis ...

. The formations are located in the

Neuquén Basin Neuquén Basin ( es, Cuenca Neuquina) is a sedimentary basin covering most of Neuquén Province in Argentina. The basin originated in the Jurassic and developed through alternating continental and marine conditions well into the Tertiary. The bas ...

of northern

Patagonia Patagonia () refers to a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and gl ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

. ''Rayososaurus'' lived during the

Cenomanian The Cenomanian is, in the ICS' geological timescale, the oldest or earliest age of the Late Cretaceous Epoch or the lowest stage of the Upper Cretaceous Series. An age is a unit of geochronology; it is a unit of time; the stage is a unit in the s ...

epoch of the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

, about 99 to 96 million years ago.L. M. Ibiricu, G. A. Casal, M. C. Lamanna, R. D. Martínez, J. D. Harris and K. J. Lacovara. (2012). The southernmost records of Rebbachisauridae (Sauropoda: Diplodocoidea), from early Late Cretaceous deposits in central Patagonia. ''Cretaceous Research'' 34:220-232 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 specimen ...

is ''R. agrioensis'', named by Argentinian paleontologist

José Bonaparte José Fernando Bonaparte (14 June 1928 – 18 February 2020) was an Argentine paleontologist who discovered a plethora of South American dinosaurs and mentored a new generation of Argentine paleontologists . One of the best-known Argentine paleo ...

in 1996.Bonaparte, J. (1996). "Cretaceous tetrapods of Argentina". ''Münchner Geowissenschaften Abhandlungen'' 30: 73-130. The species

epithet An epithet (, ), also byname, is a descriptive term (word or phrase) known for accompanying or occurring in place of a name and having entered common usage. It has various shades of meaning when applied to seemingly real or fictitious people, di ...

''agrioensis'' refers to the Agrio del Medio locality.''Rayososaurus''
at

Fossilworks Fossilworks is a portal which provides query, download, and analysis tools to facilitate access to the Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals ...

.org

Description

''Rayososaurus'' is extremely similar to ''

Rebbachisaurus ''Rebbachisaurus'' (meaning "Khebbash, Aït Rebbach lizard") is a genus of sauropod dinosaur of the superfamily Diplodocoidea, that lived during the Late Cretaceous period in Africa and possibly also South America about 99-97 million years ago. R ...

'' and there is some debate as to whether ''Rayososaurus'' is indeed a separate genus. However, morphological and temporal differences tend to support the distinction. Fossil finds include the holotype, MACN-N 41, a

scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...

femur 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 ...

and part of

fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is ...

, and the paratype (''Rayososaurus'' sp.), one broken dorsal vertebra and four broken caudal vertebrae. The racket-shaped scapula is characteristic of the

Rebbachisauridae Rebbachisauridae is a family of sauropod dinosaurs known from fragmentary fossil remains from the Cretaceous of South America, Africa, North America, Europe and possibly Central Asia. Taxonomy In 1990 sauropod specialist Jack McIntosh included t ...

Phylogeny

References

Rebbachisaurids Cenomanian life Late Cretaceous dinosaurs of South America Cretaceous Argentina Fossils of Argentina Candeleros Formation Fossil taxa described in 1996 Taxa named by José Bonaparte {{Sauropodomorph-stub