  The orthorhombic monochalcogenide SnSe has attracted much attention in recent
years as a promising high-temperature thermoelectric material. We present a
study of its thermal conductivity and specific heat of SnSe between 2~K and
300~K and quantify its anisotropic thermal diffusivity, $D$. For both
crystallographic orientations, thermal diffusivity remains above the recently
identified Planckian limit ($D > v_s^2 \tau_P$, where $v_s$ is the sound
velocity and $\tau_P= \hbar/k_BT$) and its anisotropy in $D$ is set by the
anisotropy of $v_s$. Comparison with cubic members of the IV-VI family leads to
a consistent picture, where the diffusivity in all members of the family is set
by the product of v$_s$, $\tau_P$ and the 'melting' velocity derived from the
melting temperature.
