Monotone invariant valuations on convex cones

We classify the monotone $\SOn d$-invariant valuations, $d\ge2$, on the space of all closed convex cones. They are precisely the linear combinations of the conic intrinsic volumes with increasing coefficients, or equivalently, the nonnegative linear combinations of intrinsic volume tails, up to an additive constant. On nonzero pointed cones we obtain the corresponding characterization by Grassmann angles, settling a conjecture of McMullen. Every such valuation is automatically continuous in the spherical Hausdorff topology and is $\On d$-invariant. Our proof builds on the proof of the spherical Hadwiger theorem by Wang and Wu.