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Kawanectes (meaning "Kawas swimmer") is an extinct genus of elasmosaurid plesiosaur, a type of long-necked marine reptile, that lived in the marginal marine, probably estuary, environment of Late Cretaceous Patagonia. The genus contains a Monotypic taxon, Kawanectes lafquenianum, described in 2016 by José P. O'Gorman.
A combination of Autapomorphy traits can be used to distinguish Kawanectes from all other elasmosaurids: the centra of the vertebrae are wider than they are long; the projections known as the parapophyses on the caudal vertebrae are knob-like; the ischium and pubis form a "bar" of bone that encloses two diamond-shaped openings; the ratio between the length of the humerus and the femur is unusually high (1.2); the end of the humerus bears a backward projection of bone which forms an articulating surface; and the capitulum of the femur, which likewise forms an articulating surface, is strongly .
Although Kawanectes is similar to the somewhat-larger Vegasaurus, its bones clearly represent that of an adult due to the fusion in the vertebrae, the proportions of its cervical vertebrae are the same as Vegasaurus (if Vegasaurus was an older Kawanectes, its cervical vertebrae would be longer, as with other elasmosaurids), and Vegasaurus does not have a pelvic bar (since the pelvic bar is absent in juvenile elamosaurids but present in adults, the emergence then disappearance of the pelvic bar contradicts a hypothetical growth sequence), suggesting that Vegasaurus is not the adult form of Kawanectes. On the basis of three known specimens, it is proposed that the genus exhibits sexual dimorphism in terms of ilium shape, humerus to femur size ratio and sacral centrum proportions, and that females are larger than males.
Initially recognized as a species of Trinacromerum, polycotylidae affinities were later rejected for "T." lafquenianum. O'Gorman named the new monotypic taxon Kawanectes for "T." lafquenianum in 2016. The name combines Kawa, which refers to the Kawas Sea, an ancient ocean that covered Patagonia from the Campanian to the Danian, and Greek nectes, which means "swimmer". The original specific name, lafquenianum, is the Mapuche word for "sea".
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