  Theoretical predictions for the spectrum of heavy meson-baryon bound states
are a fundamental tool for disentangling the nature of the different pentaquark
states that have been observed in experimental facilities. Here we explore this
spectrum in a phenomenological model that describes the heavy meson-baryon
interaction in terms of a contact-range interaction, where the coupling
strength is saturated by the exchange of light scalar and vector mesons, i.e.
$\sigma$, $\rho$ and $\omega$ exchanges. Saturation determines the couplings
modulo an unknown proportionality constant that can be calibrated from a
molecular candidate. If we use the $P_{\psi}^N(4312)$ as input, we predict a
series of molecular pentaquarks including the $P_{\psi}^N(4440)$ and
$P_{\psi}^N(4457)$, the recent $P_{\psi s}^{\Lambda}(4338)$ and the $P_{\psi
s}^{\Lambda}(4459)$.
