We present results on the entropy and heat capacity of spin-S honeycomb-lattice Kitaev models using high-temperature series expansions and thermal pure quantum state methods. We study models with anisotropic couplings Jz=1≥Jx=Jy for spin values 1/2, 1, 3/2, and 2. We show that for S>1/2, any anisotropy leads to well-developed plateaus in the entropy function at an entropy value of 12ln2, independent of S. However, in the absence of anisotropy, there is an incipient entropy plateau at Smax/2, where Smax is the infinite temperature entropy of the system. We discuss the possible underlying microscopic reasons for the origin and implications of these entropy plateaus.
