Strong and selective magnon-phonon coupling in the van der Waals antiferromagnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>CoPS</mml:mi> <mml:mn>3</mml:mn> </mml:msub> </mml:math>

The Raman scattering response of the biaxial antiferromagnet ${\mathrm{CoPS}}_{3}$ has been investigated as a function of both magnetic field and temperature. The peaks observed in the low-frequency spectral range $(90--200 {\mathrm{cm}}^{\ensuremath{-}1})$ have been identified as hybrid magnon-phonon excitations. The energies of the bare magnon and phonon modes and the effective coupling strengths between different excitation pairs have been determined. The strong and selective magnon-phonon interaction largely accounts for the pronounced splitting of two phononlike modes observed at 152 and 158 ${\mathrm{cm}}^{\ensuremath{-}1}$ in the antiferromagnetic phase of ${\mathrm{CoPS}}_{3}$. Based on the identification of bare magnon excitations and their magnetic-field dependence, we propose an updated set of parameters for the effective exchange $({J}_{\mathrm{eff}}=9.9 \mathrm{meV})$ and biaxial magnetic anisotropy $(D=4.3 \mathrm{meV} \text{and} E=\ensuremath{-}0.7 \mathrm{meV})$ and advocate for an apparent anisotropic $g$ factor $({\mathrm{g}}_{x} = {\mathrm{g}}_{y} = 2, {\mathrm{g}}_{z}=4)$ in the ${\mathrm{CoPS}}_{3}$ antiferromagnet.