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Temporal range: Middle Triassic
~236–234 Ma
Lewisuchus NT small.jpg
Life reconstruction of Lewisuchus admixtus
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Clade: Dracohors
Clade: Silesauridae
Genus: Lewisuchus
Romer, 1972
L. admixtus
Binomial name
Lewisuchus admixtus
Romer, 1972

Lewisuchus is a genus of archosaur that lived during the Middle Triassic (Ladinian); it was a silesaurid dinosauriform, a member of the group of reptiles which led to the dinosaurs. Lewisuchus was about 1 metre (3.3 ft) long. Fossils have been found in the Chañares Formation of Argentina.[1] It exhibited osteoderms along its back.[2]


Some of the fossils originally assigned to Lewisuchus have since been moved to other genera,[clarification needed] and the remaining portions closely resemble those of Pseudolagosuchus. A 2010 study in the Journal Nature indicated that the two may be synonymous. They were approximately the same size and came from the same locality and strata, but the fossil material is fragmentary and there is very little overlapping material. If it is shown the two are synonymous (through the discovery of additional fossils) the name Lewisuchus will get priority.[3] A large phylogenetic analysis of early dinosaurs and dinosauromorphs by Matthew Baron, David Norman and Paul Barrett (2017) and published in the journal Nature treated Lewisuchus as being synonymous with Pseudolagosuchus.[4]


  1. ^ Roman, Alfred Sherwood (1971). "The Chanares (Argentina) Triassic Reptile Fauna. XIV. Lewisuchus admixtus, gen. et sp. nov., a further thecodont from the Chanares Beds". Breviora: 380–409.
  2. ^ Bittencourt, Jonathas; Arcucci, Andrea; Marsicano, Claudia; Langer, Max (15 December 2014). "Osteology of the Middle Triassic archosaur Lewisuchus admixtus Romer (Chañares Formation, Argentina), its inclusivity, and relationships amongst early dinosauromorphs". Journal of Systematic Palaeontology. pp. 1–31. doi:10.1080/14772019.2013.878758.
  3. ^ Nesbitt, Sterling J., Sidor, Christian A., Irmis, Randall B., Angielczyk, Kenneth D., Smith, Roger M.H. and Tsuji, Linda A. (2010) "Ecologically distinct dinosaurian sister group shows early diversification of Ornithodira." Nature 464(7285):95-8 Supplement
  4. ^ Baron, M.G., Norman, D.B., and Barrett, P.M. (2017). A new hypothesis of dinosaur relationships and early dinosaur evolution. Nature, 543: 501–506. doi:10.1038/nature21700