A 1.5-m-long double sinusoidal trace from the Lance Formation of Wyoming, U.S.A, is attributed a crocodylian origin. The trace forms part of a diverse tracksite containing dinosaur and bird tracks. The double sinusoidal nature of the trace is suggested to have originated from the dual undulatory motion of body and tail. Other features such as scute and claw marks are comparable with modern crocodyle traces, even though clear footprints have not been identified. The trace therefore expands upon the already diverse dinosaurian ichnofauna of the Lance Formation to include crocodylians.