Malawisaurus

Malawisaurus; Temporal range: Early Cretaceous; Aptian PreꞒ Ꞓ O S D C P T J K Pg N
	Display at the Royal Ontario Museum
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
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
	Gigantosaurus dixeyi Haughton, 1928 (preoccupied); Tornieria dixeyi (Haughton, 1928); Janenschia dixeyi (Haughton, 1928);

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.

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

Malawisaurus

References

^ Dixey, F. (1925). The discovery of fossil reptiles. Annual Report of the Geological Survey Department for the Year 1924, Nyasaland Protectorate 1924:7
^ Andrzejewski, Kate A.; Polcyn, Michael J.; Winkler, Dale A.; Chindebvu, Elizabeth Gomani; Jacobs, Louis L. (2019-02-13). "The braincase of Malawisaurus dixeyi (Sauropoda: Titanosauria): A 3D reconstruction of the brain endocast and inner ear". PLOS ONE. 14 (2): e0211423. Bibcode:2019PLoSO..1411423A. doi:10.1371/journal.pone.0211423. ISSN 1932-6203. PMC 6373922. PMID 30759166.
^ L. L. Jacobs, D. A. Winkler, W. R. Downs and E. M. Gomani. 1993. New material of an Early Cretaceous titanosaurid sauropod dinosaur from Malawi. Palaeontology 36(3):523-534
^ Freire, Pedro Carvalho; Medeiros, Manuel Alfredo; Lindoso, Rafael Matos (2007). "Sauropod teeth diversity in the Laje do Coringa fossiliferous site, Eocenomanian of Northeastern Brazil". Paleontologia: Cenários de Vida: 523–532.
^ Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 207
^ Molina-Pérez & Larramendi (2020). Dinosaur Facts and Figures: The Sauropods and Other Sauropodomorphs. New Jersey: Princeton University Press. p. 264. Bibcode:2020dffs.book.....M.
^ "Caudal Vertebrae," Tidwell, Carpenter, and Meyer (2001). Page 145.
^ ^a ^b "Caudal Vertebrae," Tidwell, Carpenter, and Meyer (2001). Page 147.
^ França, M.A.G.; Marsola, J.C.d A.; Riff, D.; Hsiou, A.S.; Langer, M.C. (2016). "New lower jaw and teeth referred to Maxakalisaurus topai (Titanosauria: Aeolosaurini) and their implications for the phylogeny of titanosaurid sauropods". PeerJ. 4: e2054. doi:10.7717/peerj.2054. PMC 4906671. PMID 27330853.

Footnotes

S. H. Haughton. 1928. On some reptilian remains from the Dinosaur Beds of Nyasaland. Transactions of the Royal Society of South Africa 16:67-75
Paul, Gregory S. (2010) The Princeton Field Guide to Dinosaurs.
Tidwell, V., Carpenter, K. & Meyer, S. 2001. New Titanosauriform (Sauropoda) from the Poison Strip Member of the Cedar Mountain Formation (Lower Cretaceous), Utah. In: Mesozoic Vertebrate Life. D. H. Tanke & K. Carpenter (eds.). Indiana University Press, Eds. D.H. Tanke & K. Carpenter. Indiana University Press. 139-165.