The small ichthyosaur Mixosaurus is the most widely distributed ichthyosaur. It is known from Lower Triassic rocks of British Columbia, Canada (Callaway and Brinkman, 1989), and Middle Triassic rocks of northwestern North America (Alaska, British Columbia), China, Timor, the western Tethys (Switzerland, Italy, Turkey), the Germanic Triassic, and the high Arctic (Spitsbergen, Exmouth Island) (Mazin, 1986; Callaway and Brinkman, 1989; Callaway and Massare, 1989). The presence of Mixosaurus in one of the richest ichthyosaur provinces, the Middle Triassic of Nevada (Merriam, 1908), has been difficult to establish. The history of this problem is very colorful and is the topic of this note together with the description of a new specimen from the Nevada Middle Triassic.

When the existence of juveniles, eggs, and nesting sites of the hadrosaur Maiasaura peeblesorum and the hypsilophodontid Orodromeus makelai from the Upper Cretaceous Two Medicine Formation of western Montana were reported, they provided powerful insights into the reproductive strategies of these animals (Horner and Makela, 1979; Horner, 1982, 1984; Horner and Weishampel, 1988). Dinosaur eggs had been known since 1923 when nests attributed to the ceratopsian Protoceratops andrewsi were discovered in Mongolia (Brown and Schlaikjer, 1940), but there was no direct information about behavior or survival strategies in hatchling dinosaurs until the Maiasaura and Orodromeus findings. These recent discoveries have generated a number of hypotheses on the reproductive behavior of dinosaurs relating to the extent of parental care, fidelity in nesting sites, and the aggregation of juveniles into groups.