''Melanorosaurus'' (meaning "Black Mountain Lizard", from the Greek ''melas/'', "black", ''oros/'', "mountain" + ''/'', "lizard") is a

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 ...

of basal sauropodomorph

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 ...

that lived during the

Late Triassic The Late Triassic is the third and final epoch (geology), epoch of the Triassic geologic time scale, Period in the geologic time scale, spanning the time between annum, Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch a ...

period. An omnivore from

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

, it had a large body and sturdy limbs, suggesting it moved quadrupedally. Its limb bones were massive and heavy like the limb bones of true sauropods.

Description

''Melanorosaurus'' had a skull which measured approximately 250 mm. The snout was somewhat pointed, and the skull was somewhat triangular when seen from above or below. The premaxilla had four teeth on each side, a characteristic of primitive sauropodomorphs. The maxilla had 19 teeth on each side of the jaw. ''Melanorosaurus'' was around long, with a weight of .

Discovery and species

The

type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...

s, syntypes SAM-PK-3449 and SAM-PK-3450, were discovered, described and named in 1924 by Sidney H. Haughton. They were collected from the Triassic Lower Elliot Formation, dating to the early

Norian The Norian is a division of the Triassic geological period, Period. It has the rank of an age (geology), age (geochronology) or stage (stratigraphy), stage (chronostratigraphy). It lasted from ~227.3 to Mya (unit), million years ago. It was prec ...

, on the north slope of the Thaba 'Nyama (Black Mountain) in Transkei, South Africa. In 2024, ''Melanorosaurus'' was redescribed and SAM-PK-3449 was designated the lectotype of the species. However, SAM-PK-3450 differs in many aspects from SAM-PK-3449 so was excluded from ''Melanorosaurus'', representing a probable sauropodomorph. Haughton also referred SAM-PK-3532 to ''Melanorosaurus,'' a partial skeleton discovered from a different locality than the lectotype. Nevertheless, it too differs from the lectotype in aspects of the ulna and ilium, thus it can only be regarded an indeterminate sauropodomorph for now. In 1985, Peter Galton suggested the referral of NMQR 1551, an exemplar of the postcranial remains of two individuals to ''M. readi'', and in 2024, this was considered a strong possibility due to similarities with the lectotype specimen. However, the authors stressed that a detailed reassessment of the material was necessary before any formal referrals were to be made. The first complete skull referred to ''Melanorosaurus'', NM QR3314, was described in 2007.Yates, Adam M., "The first complete skull of the Triassic dinosaur ''Melanorosaurus'' Haughton (Sauropodomorpha: Anchisauria)". In Barrett & Batten (eds.), ''Evolution and Palaeobiology'' (2007), pp. 9–55. However, this specimen comes from the Upper Elliot, unlike the ''Melanorosaurus'' type material and NM QR1551, rendering its referral to the genus untenable. ''Melanorosaurus thabanensis'' was named in 1993 by Gauffre, based on

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 ...

MNHN LES-16, a

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 ...

found in the Upper Triassic lower Elliot Formation. However, a recent review of the material demonstrated that the femur, along with six other bones, can't be referred to the genus ''Melanorosaurus'', and a new combination ('' Meroktenos thabanensis'') was created.

Classification

''Melanorosaurus'' was once classified as a prosauropod, but Prosauropoda no longer appears to be a natural group. According to some definitions of

Sauropoda Sauropoda (), whose members are known as sauropods (; from ''wikt:sauro-, sauro-'' + ''wikt:-pod, -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative t ...

, ''Melanorosaurus'' is an early sauropod. However, these definitions also take in many other former "prosauropods", and Adam Yates has proposed a definition of Sauropoda that will specifically exclude ''Melanorosaurus'' (Sauropoda as all sauropodomorphs closer to '' Saltasaurus'' than ''Melanorosaurus''). This definition would allow Sauropoda to retain its traditional concept. The following cladogram shows the position of ''Melanorosaurus'' within Massopoda, according to Oliver W. M. Rauhut and colleagues, 2020:

References

Bibliography

* {{Taxonbar, from=Q132584 Massopoda Dinosaur genera Norian dinosaurs Rhaetian dinosaurs Elliot Formation Dinosaurs of South Africa Fossil taxa described in 1924 Taxa named by Sidney H. Haughton