Project 437: M. D. Ezcurra, A. Lecuona, A. Martinelli. 2010. A New Basal Archosauriform Diapsid from the Lower Triassic of Argentina. Journal of Vertebrate Paleontology. 30 (5):1433-1450.
Specimen: † Koilamasuchus gonzalezdiazi Ezcurra, Lecuona and Martinelli, 2010 (MACN/PV:18119)
View: Natural external molds


The best-known South American Early Triassic archosauriform belongs to a putative proterosuchid briefly reported by José Bonaparte in 1981, collected from the Quebrada de los Fósiles Formation (Puesto Viejo Group, Argentina). This specimen consists of well-preserved natural external molds of a partial postcranium that preserve dorsal vertebrae, osteoderms, a dorsal rib, a possible gastralium, a chevron, a humerus, an ilium, two metapodials, and an ungual. We re-describe this specimen and identify autapomorphies that allow us to recognize Koilamasuchus gonzalezdiazi, gen. et sp. nov. The presence of an iliac blade with a slightly convex dorsal margin and with a maximum length more than 3 times its maximum height places Koilamasuchus within Archosauriformes. A cladistic analysis of basal Archosauriformes positions Koilamasuchus more crownwards than Proterosuchus, Sarmatosuchus, Fugusuchus, and Osmolskina, as the sister taxon of the clade that includes Erythrosuchidae and Archosauria. Proterosuchidae is found to be paraphyletic. The presence of an iliac preacetabular process, a pubic peduncle that forms an angle lower than 45° to the longitudinal axis of the ilium, and dorsal body osteoderms positions Koilamasuchus in Archosauriformes more crownwards than proterosuchids. Koilamasuchus is more basal than erythrosuchids within Archosauriformes because of the presence of dorsal ribs with a poorly developed proximal end. Koilamasuchus importantly increases the diversity of Archosauriformes during the biotic recovery following the Permo-Triassic mass extinction.

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Project DOI: 10.7934/P437,
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MorphoBank Project 437
  • Creation Date:
    15 November 2010
  • Publication Date:
    06 February 2013
  • Project views: 20592

    Authors' Institutions

    • Museo Paleontológico Egidio Feruglio

    • Museo Argentino de Ciencias Naturales Bernardino Rivadavia

    • Universidade Federal de Uberlandia


    member name taxa specimens media
    MorphoBank Curator
    Project Administrator
    Maureen Admin
    Full membership
    Martin Ezcurra
    Full membership
    Seth Kaufman

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