New papers recording new occurrences of fossil Monodontidae are available online:
Hiroto Ichishima; Hitoshi Furusawa; Makino Tachibana; Masaichi Kimura (2018). First monodontid cetacean (Odontoceti, Delphinoidea) from the early Pliocene of the north‐western Pacific Ocean. Papers in Palaeontology. Online edition. doi:10.1002/spp2.1244. (describes Haborodelphis japonicus)
Pesci et al. (2018). First record of Monodontidae (Cetacea, Odontoceti) in the Mediterranean Basin from the Pliocene sands of Arcille (Grosseto, Tuscany, Italy). Fossilia, Volume 2018: 37-39.
Denebola and Bohaskaia were long the only described fossil monodontid species from the pre-Pleistocene, but Haborodelphis and the new monodontid skull from Tuscany shed new light on the distribution of monodontids.