Lophocetus ("crested whale") is an extinct genus of dolphin belonging to the clade Delphinida that is known from late Miocene (Tortonian) marine deposits in California and Maryland.

[2][3] The phylogenetic analysis of Brujadelphis recovered Lophocetus as polyphyletic, with L. calvertensis and L. repenningi forming a clade with taxa assigned to Pithanodelphininae and Tagicetus, and L. pappus falling as the sister taxon of Lipotidae.

[5] In 1955, Remington Kellogg described a new species of Lophocetus, L. pappus, on the basis of the skull USNM 15985 from the Langhian-age Plum Point Member of the Calvert Formation.

However, in a couple of abstracts published in 2000 and 2008, Barnes and colleagues recognized Lophocetus pappus as a new genus of lophocetine distinct from Liolithax after the discovery of a skull from Middle Miocene marine deposits in Baja California Sur showed that Liolithax was a kentriodontine rather than a lophocetine and different from L. pappus in its smaller tooth diameter, smaller size, and more elongated rostrum.

[8][9] Godfrey and Lambert (2023) confirmed the generic distinctness of "L." pappus from Liolithax and erected the new genus Miminiacetus for it.