Subfamily SCAPHOKOGIINAE Muizon, 1988

EMENDED DIAGNOSIS. — Scaphokogiinae are recognized as Kogiidae by the following combination of characters: strongly asymmetric skull in dorsal view; relatively small skull size (i.e., bizygomatic width <40 cm); presence of a broad supracranial basin that extends over most of the dorsal surface of the neurocranium; external nares greatly asymmetric; absence of both nasals; presence of a sagittal facial crest; and right maxilla reaching the sagittal plane of the skull on the posterior wall of the supracranial basin.

Scaphokogiinae differ from all other kogiids by the following presumed autapomorphies: on the right side of the skull, maxillapremaxilla suture distinctly anterolaterally directed anterior to the antorbital notch; lateral maxillary crests high, vertical, and plate-like (c. 5[1]); nuchal crest strongly shifted backwards in lateral view; occipital shield flat or concave in lateral view, forming an angle distinctly greater than 90° with the long axis of the rostrum (c. 30[3]); supracranial basin deep to very deep and spoon-shaped; right anterolateral border of the supracranial basin marked by a distinct supracranial step; absence of distinct premaxillary or peripheral fossae within the supracranial basin; right premaxilla covering a small fraction (i.e., less than 1/ ª) of the total area of the supracranial basin. They are further diagnosed by the following combination of characters: right premaxilla neither reaching, nor even approaching the occipital crest (shared with Aprixokogia Whitmore & Kaltenbach, 2008); presence of discrete dental alveoli on the maxilla (shared with Aprixokogia, Koristocetus Collareta, Lambert, Muizon, Urbina & Bianucci, 2017 and, possibly, Pliokogia Collareta, Cigala Fulgosi & Bianucci, 2019; condition unknown in Praekogia and Thalassocetus Abel, 1905); antorbital notches not opening onto the supracranial basin (shared with Aprixokogia and Thalassocetus); antorbital notches forming a narrow slit (shared with Nanokogia Vélez-Juarbe, Wood, De Gracia & Hendy, 2015, Kogia, Koristocetus, Pliokogia and, possibly, Praekogia Barnes, 1973); lateral maxillary crests mediolaterally thin (shared with Koristocetus, Nanokogia and Praekogia); posterodorsal corner of the lacrimojugal complex shaped as a pointed process that wedges between the maxilla and the frontal (shared with Kogia, Nanokogia, Pliokogia, and Praekogia; condition unknown in Thalassocetus); and presphenoid not covered by the vomer in ventral view (shared with Aprixokogia, Kogia, Nanokogia, and Pliokogia; condition unknown in Thalassocetus).