Gengasaurus is an extinct genus of ophthalmosaurid ichthyosaur from the Jurassic. The type and only species, Gengasaurus nicosiai, was named in 2017, after the locality of Genga, Marche. It lived in Italy about 152 million years ago.

History The near complete holotype was discovered in 1976 in the Late Jurassic (Tithonian) Calcari ad aptici e Saccocoma Formation at Camponocecchio and it was described in 1980Fastelli, C. & Nicosia, U. (1980). L'Ittiosauro di Genga (Ancona). In I vertebrati fossili italiani (eds Parisi, G. & Seppi, G.), pp. 95–101. Verona: Catalogo della Mostra. and 2000De Marinis, G. & Nicosia, U. (2000). L'Ittiosauro di Genga. Castelferretti, Ancona: Cassa di Risparmio di Fabriano e Cupramontana Edizioni, 220 pp. as the "Genga ichthyosaur" before it was named and described in 2016Ilaria Paparella, Erin E. Maxwell, Angelo Cipriani, Scilla Roncacè and Michael W. Caldwell (2016) - The first ophthalmosaurid ichthyosaur from the Upper Jurassic of the Umbrian–Marchean Apennines (Marche, Central Italy). Geological Magazine (advance online publication) - this paper was eventually published in 2017. The holotype is now housed at the Spaelaeo-Palaeontologic Museum in Genga.

Phylogeny The following cladogram shows a possible phylogenetic position of Gengasaurus in Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020).

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