Irregularities at high spin in the odd-odd nucleus ${}_{}{}^{158}{}_{}{}^{}\mathrm{Tm}$

High spin states in the odd-odd nucleus ${}_{69}{}^{158}{}_{}{}^{}\mathrm{Tm}_{89}^{}{}_{}{}^{}$ were populated in the ${}_{}{}^{110}{}_{}{}^{}\mathrm{Pd}({}_{}{}^{51}{}_{}{}^{}\mathrm{V}, 3n)$ reaction at 220 MeV. It has been possible to construct a level scheme with states up to spin ${36}^{\mathrm{}(+)\mathrm{}}$ (tentatively ${38}^{+}$), the highest spins measured in an odd-odd nucleus to date. The proposed high-spin level scheme for ${}_{}{}^{158}{}_{}{}^{}\mathrm{Tm}$ and its interpretation differ considerably from previous work on this nucleus. Irregularities in the $\gamma$-ray energy spacings observed at the highest spins are also discussed.