Malawisaurus
Extinct genus of dinosaurs
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Malawisaurus (meaning "Malawi lizard") is an extinct genus of titanosaurian sauropod dinosaur. It is known from the Dinosaur Beds of northern Malawi, which probably date to the Aptian stage of the Early Cretaceous. The type species is M. dixeyi and the specific name honours Frederick Augustus Dixey.
| Malawisaurus Temporal range: Early Cretaceous | |
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| Display at the Royal Ontario Museum | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Clade: | †Titanosauria |
| Clade: | †Lithostrotia |
| Genus: | †Malawisaurus Jacobs et al., 1993 |
| Species: | †M. dixeyi |
| Binomial name | |
| †Malawisaurus dixeyi (Haughton, 1928) [originally Gigantosaurus, preoccupied] | |
| Synonyms | |
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Discovery and naming
Malawisaurus dixeyi was originally described in 1928 by Sidney H. Haughton as a species of Gigantosaurus (an invalid name for the diplodocid currently known as Tornieria). Haughton considered it closely related to the species G. robustus (later the type species of Janenschia). The holotype was discovered c. 1924 in the "Dinosaur Beds" of Malawi (then known as the Nyasaland Protectorate),[1] which are usually considered to be of Barremian-Aptian age based on K–Ar dating, though they have also been suggested to be Late Cretaceous in age based on the vertebrate assemblage.[2] In 1993 it was placed in the newly named genus Malawisaurus by Louis L. Jacobs and colleagues, based on newly collected material from the locality.[3] The holotype is SAM 7405, a partial skeleton and its type locality is Mwakasyunguti.
Malawisaurus is not known outside of Africa - however, an isolated tooth resembles those associated with Malawisaurus and was found in the Late Cretaceous (Cenomanian)-aged Alcântara Formation of Brazil according to a report in 2007.It is currently listed as "Titanosauria indet., possibly Malawisaurus .sp".[4]
Description
Relatively small by sauropod standards, Malawisaurus reached lengths of about 15 metres (49 ft), and weighed about 10 tonnes (11 short tons).[5] In 2020 it was given a smaller estimation of 11 meters (36 ft) and 2.8 tonnes (3.1 short tons).[6] Like some other titanosaurs, ossicles have been found which are believed to represent dermal scutes that covered the skin.
The vertebrae from the middle part of its tail had elongated centra.[7] Malawisaurus had vertebral lateral fossae that resembled shallow depressions.[8] Fossae that similarly resemble shallow depressions are known from Saltasaurus, Alamosaurus, Aeolosaurus, and Gondwanatitan.[8]
Classification
By definition, Malawisaurus has to be the most basal lithostrotian. The cladogram below follows Franca et al. (2016).[9]
| Lithostrotia |
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