TYPE SPECIES. — Mesocetus poucheti Moreno, 1892, by monotypy, known from a single specimen thought to originate from Burdigalian deposits of the Gaiman Formation, in the Chubut province, Argentina (see Paolucci et al. 2020 for the complex taxonomic history of this species).
OTHER REFERRED SPECIES. — Diaphorocetus ortegai n. sp.
REMARKS
The referral of a new species to the genus Diaphorocetus allows for the addition of one synapomorphy to the detailed emended diagnosis provided by Paolucci et al. (2020): dorsoventral flattening of the maxilla on the rostrum (ratio between maximum dorsoventral height of maxilla along the anterior half of the rostrum and bizygomatic width <0.1, only shared with Acrophyseter deinodon Lambert, Bianucci & Muizon, 2008 and Zygophyseter varolai Bianucci & Landini, 2006). Whereas most differential characters provided by Paolucci et al. (2020) apply to the new species, we propose to remove the following characters from the genus diagnosis: i) ‘rostrum [...] contributing 50% of CBL’, as the rostrum is incomplete on the types of both the included species; ii) ‘zygomatic process of squamosal with ventrally deflected apex’, as we interpret this condition as at least partly resulting from an inaccurate reconstruction of the type neurocranium of D. poucheti (see below); and iii) the differential character ‘more open jugular notch’, which appears to vary within the genus and could be easily impacted by postmortem deformation and/or reconstruction inaccuracies.