| Meroktenos Temporal range: Late Triassic, | |
|---|---|
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| Right femur | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | † Sauropodomorpha |
| Clade: | † Anchisauria |
| Genus: | † Meroktenos Peyre de Fabrègues & Allain, 2016 |
| Type species | |
| †Meroktenos thabanensis (Gauffre, 1993) | |
| Synonyms | |
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Meroktenos is a genus of basal sauropodomorph dinosaur that lived during the Late Triassic period of what is now Lesotho.
In 1959, François Ellenberger, Paul Ellenberger, Jean Fabre and Leonard Ginsburg discovered the type specimen, a thighbone or femur and other assorted bones, south of the village of Thabana Morena. In 1962 these were addressed in a thesis by D. Costedoat. [1] The exact location the bones were recovered, is today unknown. [2]
In 1993, François-Xavier Gauffre assigned the remains to a second species of Melanorosaurus: Melanorosaurus thabanensis. The description was provisional, and in 1997 the fossil was described in more detail in a publication by Jacques van Heerden and Peter Malcolm Galton. The specific name refers to the site Thabana-Morena in Lesotho. [3]
Gauffre assumed that the specimen had been found in the Upper Elliot Formation dating from the Hettangian-Sinemurian and thus was about twenty million year younger than Melanorosaurus readi. [3] In 1996, he revised the date to the Lower Elliot Formation of the late Triassic in his non-published dissertation. He also referred the thighbone to a new genus and species Thotobolosaurus (now Kholumolumo [4] ). This remained a non-valid nomen ex dissertatione, as the name would never be published; furthermore the type material of this species does not coincide with that of M. thabanensis. [5]
In 2016, M. thabanensis was appointed to the separate genus Meroktenos by Claire Peyre de Fabrègues and Ronan Allain. The genus name is a combination of ancient Greek μηρός, meros ("thigh") and κτῆνος, ktènos ("beast"). [2] The combinatio nova thus becomes Meroktenos thabanensis, the type species is the original Melanorosaurus thabanensis.
The holotype, MNHN.F.LES 16, consists of a right thighbone (MNHN.F.LES16c), a portion of the right ilium, with a piece of a vertebral neural arch (MNHN.F.LES16a); a left pubic bone (MNHN.F.LES16b); and a second right metatarsal (MNHN.F.LES16d) associated with the skeleton. In 2016, a new specimen, MNHN.F.LES351, was referred to the species; consisting of a cervical vertebra, a left ulna and a, probably left, radius. It might have belonged to the same individual as the holotype, but this cannot be strictly proven. [2]
Meroktenos has a femur length of around forty-eight centimeters, [2] suggesting a body length of about four meters.
In 2016, a revised list of distinguishing traits was given. The blade height of the ilium, measured from the highest point of the antitrochanter to the upper edge of the blade is 60% of the total height of the ilium, including peduncles. The rear blade of the ilium is roughly triangular in side view. The femur is very compact with a robusticity index, length divided by the circumference of the shaft, of 2.09. The femur has a straight shaft in both side and front views. The femoral shaft is substantially wider transversely than it is wide in side view, with a ratio of 1.58. On the rear of the femoral shaft, the fourth trochanter is oriented obliquely, running from the upper and inner side to the lower and outer side. [2]
In 2016, Meroktenos was placed in the Sauropodomorpha, in a basal position. According to a cladistic analysis, Meroktenos formed a polytomy with Blikanasaurus and more derived taxa, above Aardonyx in the evolutionary tree and below a polytomy including Camelotia , Melanorosaurus and more derived groups: [2]
| Massopoda |
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A 2021 study by Pol and colleagues found Meroktenos to be a member of Lessemsauridae, being the sister taxon of a clade formed by Kholumolumo and Ledumahadi : [6]
| Sauropodiformes |
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The relative transverse width of the femur, the eccentricity, is remarkably high for such a small animal. These proportions were known previously only from Sauropoda and explained as an adaptation to a very high absolute weight. Because the holotype probably was not a young animal and is unlikely to have attained giant proportions, the trait must have had a different function. [2]
Melanorosaurus is a genus of basal sauropodomorph dinosaur that lived during the Late Triassic period. A herbivore from South Africa, it had a large body and sturdy limbs, suggesting it moved about on all fours. Its limb bones were massive and heavy like the limb bones of true sauropods.
Isanosaurus means "North-eastern thailand lizard" was a sauropod dinosaur from Thailand. It was originally dated to approximately 210 million years ago during the Late Triassic, which would make it one of the oldest known sauropods. Its age was later considered uncertain, and may be as young as Late Jurassic. The only species is Isanosaurus attavipachi. Though important for the understanding of sauropod origin and early evolution, Isanosaurus is poorly known. Exact relationships to other early sauropods remain unresolved.
Antetonitrus is a genus of sauropod dinosaur found in the Early Jurassic Elliot Formation of South Africa. The only species is Antetonitrus ingenipes. As one of the oldest known sauropods, it is crucial for the understanding of the origin and early evolution of this group. It was a quadrupedal herbivore, like all of its later relatives, but shows primitive adaptations to use the forelimbs for grasping, instead of purely for weight support.
Blikanasaurus is a genus of sauropodomorph dinosaur from the late Triassic of South Africa. The generic name Blikanasaurus is derived from Greek, meaning "lizard from Blikana". The species name cromptoni is taken from the surname of A.W. “Fuzz” Crompton, an American paleontologist who led numerous field expeditions in Elliot Formation outcrop localities in South Africa. Blikanasaurus is only known from partial hindlimb bones that were recovered from the lower Elliot Formation (LEF) in the Eastern Cape.
Euskelosaurus is a sauropodomorph dinosaur from the Late Triassic of South Africa and Lesotho. Fossils have only been recovered from the lower Elliot Formation in South Africa and Lesotho, and in one locality in Zimbabwe.
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Chindesaurus is an extinct genus of basal saurischian dinosaur from the Late Triassic of the southwestern United States. It is known from a single species, C. bryansmalli, based on a partial skeleton recovered from Petrified Forest National Park in Arizona. The original specimen was nicknamed "Gertie", and generated much publicity for the park upon its discovery in 1984 and airlift out of the park in 1985. Other fragmentary referred specimens have been found in Late Triassic sediments throughout Arizona, New Mexico, and Texas, but these may not belong to the genus. Chindesaurus was a bipedal carnivore, approximately as large as a wolf.
Glacialisaurus is a genus of sauropodomorph dinosaur. It lived during the Pliensbachian stage of the Early Jurassic period around 186 to 182 million years ago in what is now the central region of the Transantarctic Mountains of Antarctica. It is known from two specimens; the holotype, a partial tarsus (ankle) and metatarsus, and a partial left femur. The fossils were collected by a team led by paleontologist William R. Hammer during a 1990–91 field expedition to the Hanson Formation of Antarctica. They were described in 2007, and made the basis of the new genus and species Glacialisaurus hammeri. The genus name translates as “icy” or "frozen lizard”, and the species name honors Hammer.
Massopoda is a clade of sauropodomorph dinosaurs which lived during the Late Triassic to Late Cretaceous epochs. It was named by paleontologist Adam M. Yates of the University of the Witwatersrand in 2007. Massopoda is a stem-based taxon, defined as all animals more closely related to Saltasaurus loricatus than to Plateosaurus engelhardti.
Ignavusaurus is a genus of basal sauropodomorph dinosaur that lived during the Early Jurassic in what is now Lesotho. Its fossils were found in the Upper Elliot Formation which is probably Hettangian in age. It was described on the basis of a partial, well preserved articulated skeleton. The type species, I. rachelis, was described in 2010 by Spanish palaeontologist F. Knoll.
Arcusaurus is an extinct genus of sauropodomorph dinosaur from the Early Jurassic of South Africa.
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Ixalerpeton is a genus of lagerpetid avemetatarsalian containing one species, I. polesinensis. It lived in the Late Triassic of Brazil alongside the sauropodomorph dinosaur Buriolestes.
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