The genus Dinofurcula was erected by Kofoid & Skogsberg (1928), based on Phalacroma ultima, described in 1907. The genus and its two species (D. ultima and D. ventralis) have not been reported in the literature since their first description and renaming. Here we provide morphological information obtained by light and scanning electron microscopy on D. cf. ultima, recorded in the tropical Mexican Pacific. The cells have a ‘molariform body’, due to the presence of two large posterior processes; the dorsal-posterior one is triangular and acute, and different from the ‘horn’ originally described. A short crest runs on the left epithecal plate parallel to the suture band of the epitheca. The sulcus is located laterally, displaced toward the right side of the hypotheca. The theca is scattered with areolae and pores, but they are less dense on or absent from the ventral-posterior process and on the dorsal margin of the dorsal-posterior one. Specimens found in this study are smaller (31–36.5 μm in length) than those described originally. Dinofurcula ultima may be regarded as a tropical form distributed in tropical and subequatorial waters of the Pacific Ocean.