High-spin states in Yb155 have been studied via the Sm144(O16,5n)Yb155 reaction at a beam energy of 118 MeV. One negative-parity and one positive-parity cascade built on the νf7/2 and νi13/2 states, respectively, are established for the first time. The structures observed in Yb155 are compared with those in the neighboring N=85 isotones and with semiempirical shell-model (SESM) calculations. According to adiabatic and configuration-fixed constrained triaxial covariant density functional theory (CDFT) calculations, a coexistence of prolate and oblate shapes is predicted to exist in Yb155. © 2016 American Physical Society.