58 



THE QUARTERLY REVIEW OF BIOLOGY 



from its mate on median line of palate by 

 axial ridge of vomer; simple pterygoids 

 neither spreading laterally over alisphe- 

 noid nor reduplicated along either margin, 

 and not completely covering palatines on 

 ventral aspect of skull; long mandibular 

 symphysis; and numerous teeth in both 

 jaws, but those in the upper jaw lodged 

 solely in the maxillaries. The crowns 

 of the teeth are covered with nodular or 

 reticulate enamel and are antero- 

 posteriorly compressed; the roots are 

 laterally compressed and expanded dis- 

 tally. The teeth of Inia have a large in- 

 ternal protocone shelf covered with rugose 

 enamel, while those of Lipotes have this 

 portion of the tooth very much reduced. 

 The cervical vertebrae are all free. 



ZIPHIIDAE 



In addition to the squalodonts there 

 occurs in the Lower Miocene Patagonian 

 formation a peculiar extinct porpoise 

 Diocboticbus vanbenedeni, which possesses 

 so many anomalous features that its 

 relationships were somewhat of a puzzle 

 for many years. Moreno (1891), the 

 original describer, did not reach any 

 conclusion as to its family position. 

 Lydekker (1894) considered it to be a 

 primitive platanistid, and True (1910) 

 thought that it was a squalodont with 

 simple, single-rooted, conical teeth. 

 Dal Piaz (1916) made a new family, 

 Squalodelphidae, for the reception of this 

 porpoise and an allied cetacean, Squalo- 

 delpbis fabianii, found in the Upper 

 Langhian stage of Belluno, Italy. More 

 recently Winge (1918, 19x1) and Cabrera 

 (192.6) have considered Diocboticbus to be 

 the most primitive known form of the 

 beaked whales (family Ziphiidae). Four 

 more or less complete skulls of this 

 peculiar ziphioid whale have been col- 

 lected in Chubut and Santa Cruz Terri- 

 tories, Argentine Republic. 



The skull of Diocboticbus is characterized 

 as follows : 13 teeth in each maxillary and 

 19 in each mandible; posterior teeth are 

 short, with single main cusp, covered 

 with smooth enamel, and have an anterior 

 and posterior minute tubercle; anterior 

 teeth are conical, long, and curved; all 

 the teeth are single rooted; premaxillary 

 expanded anteriorly and not touching 

 posteriorly upon the frontal; maxillary 

 bent upward behind premaxillaries, with 

 its inner margin on a level with the 

 vertex and in contact posteriorly with 

 crest of supraoccipital; nasal bones large, 

 not overhanging narial passages; large 

 olfactory foramina separated mesially by 

 mesethmoid; low broad supraoccipital; 

 backward extension of posterior margin 

 of temporal fossa; zygomatic processes 

 large, thick, oblong, and very little 

 divergent; elongate sinus on ventral sur- 

 face of maxillary anterior to choana; 

 pterygoid with an inner vertical plate 

 and an outer more or less horizontal plate, 

 which conceals the alisphenoid; mandibu- 

 lar symphysis long; mandible strongly 

 convex posteriorly; and length of skull 

 23 to 25 inches. The facial depression 

 is farther forward than in living ziphioids, 

 but is clearly antecedent to the postros- 

 tral depression seen on skulls of living 

 beaked whales, while the elevation of the 

 vertex is what might be expected in a 

 precursor of the more highly specialized 

 types of the later Miocene. The cervical 

 vertebrae are free, and as True pointed out 

 the characters exhibited by the vertebral 

 column are distinctly ziphioid. 



It shares with Squalodon the following 

 important characters: orbital plates of 

 maxillaries do not completely cover the 

 supraorbital processes of the frontals; vom- 

 erine trough wide; zygomatic processes 

 large, thick, and oblong; long meseth- 

 moid separating the olfactory foramina; 

 and premaxillaries expanded anteriorly 



