''Rayososaurus'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

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 b ...

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

in the family

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 ...

. ''Rayososaurus'' was 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. He has been described by paleontologist ...

in 1996. Its

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. * ...

and only accepted species is ''Rayososaurus agrioensis''. The species ''

Limaysaurus tessonei ''Limaysaurus'' ("Limay lizard") is a genus represented by a single species of Rebbachisauridae, rebbachisaurid Sauropoda, sauropod dinosaurs, which lived during the mid-Cretaceous period, about 99.6 to 94 million years ago, in the Cenomanian, in ...

'' was at one point included in ''Rayososaurus'' as ''Rayososaurus tessonei''.

History of discovery

The only known specimen of ''Rayososaurus agrioensis'' was discovered in 1991 by a team led by José F. Bonaparte, at a locality three kilometers south of Agrio del Medio in

Picunches Department Pehuenches is a department located in the west of Neuquén Province, Argentina. Geography The Department is surrounded by Loncopué Department in the north, Confluencia Department in the northeast, Zapala Department in the southwest, Catán Li ...

, Neuquén Province, Argentina. In 1996, Bonaparte described the remains as a new genus and species of sauropod, ''Rayososaurus agrioensis''. Bonaparte believed that the strata the specimen was excavated from belonged to the

Rayoso Formation The Rayoso Formation is a geological Formation (geology), 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 f ...

, and named the genus after it. The species name refers to the Agrio River, which the specimen was found near. Bonaparte argued that the distinctive morphology of the scapula indicated that ''Rayososaurus'' was closely related to ''

Rebbachisaurus ''Rebbachisaurus'' (meaning " 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. Remains at ...

'', which was considered a

diplodocid Diplodocids, or members of the family Diplodocidae ("double beams"), are a group of sauropod dinosaurs. The family includes some of the longest creatures ever to walk the Earth, including '' Diplodocus'' and '' Supersaurus'', some of which may ha ...

at the time, and suggested that the two probably represent a previously-unrecognized clade of sauropods distinct from diplodocids. The following year, Bonaparte proposed the family

to encompass ''Rayososaurus'' and ''Rebbachisaurus''. Efforts undertaken in 2008 and 2009 re-located the original locality and determined that the specimen actually came from the upper layers of the

Candeleros Formation The Candeleros Formation is a geologic formation that outcrop, crops out in the Rio Negro Province, Río Negro, Neuquen Province, Neuquén, and Mendoza Province, Mendoza provinces of northern Patagonia, Argentina. It is the oldest formation in the ...

. In 1998, Jeffrey Wilson and Paul Sereno proposed assigning ''Rebbachisaurus tessonei'' to ''Rayososaurus''. In 2004, Salgado and colleagues rejected this assignment and proposed the new genus ''

Limaysaurus ''Limaysaurus'' ("Limay lizard") is a genus represented by a single species of rebbachisaurid sauropod dinosaurs, which lived during the mid-Cretaceous period, about 99.6 to 94 million years ago, in the Cenomanian, in what is now South America (n ...

'' for ''R. tessonei'', which is now known as ''Limaysaurus tessonei''.

Fossil record

The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

and only known specimen of ''Rayososaurus agrioensis'', MACN-N 41, consists of two partial

scapulae The scapula (: 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 either side ...

, most of the left

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

, and the proximal half of the left

fibula The fibula (: fibulae or fibulas) 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. ...

. The

, where the specimen was found, dates to the

Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...

age of the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent 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 ''cre ...

. Specimens from Brazil were assigned to ''Rayososaurus'' in 2004, but this was based on the now-rejected inclusion of ''Limaysaurus tessonei'' in ''Rayososaurus'', so the specimens would better be referred to ''Limaysaurus'', although they might actually be fragmentary remains of ''Amazonsaurus''.

Description

''Rayososaurus'' has been considered a medium-sized sauropod, with a body mass estimated at 9,353 kg. Like other rebbachisaurids, ''Rayososaurus'' had a racquet-shaped scapula.

References

{{Portal bar, Dinosaurs, Paleontology Rebbachisauridae Dinosaur genera Cenomanian dinosaurs Candeleros Formation Taxa named by José Bonaparte Fossil taxa described in 1996 Dinosaurs of Argentina