PALEOCENE MAMMALS OF CENTRAL UTAH GAZIN 



49 



Genus IL\PLOCONUS Cope 



HAPLOCONUS INOPlNATUS« Gazin 



Haploconus inopinatus Gazin, 1939b, p. 280. 



A second genus of anisonchine periptycliids is represented in the 

 Dragon fauna by several fragmentary specimens, including a maxil- 

 lary portion with IM^ and most of M', No. 15760, which has been 

 made the type of Haploconus inopinatus (fig. 28). The form appar- 

 ently represents Haploconus as indicated by the prominent lingual 

 position of the hypocone. It is close in size to the 

 Torrejon material referred to Haploconus angus- 

 tus but with the teeth relatively wider transversely 

 and with M^ much wider than M^ A difference 

 in width between M^ and IVP was noted in certain 

 specimens of Haploconus referred to H. angustus, 

 but apparently the difference is not so marked as 

 in H. inopinatus. 



The two upper molars in the type show a slight 

 development of a metaconule, but most noticeable 

 is the distinct protostyle that characterizes teeth 

 in Haploconus comiculatus. H. inopinatus is much 

 smaller than the type of H. corniculatus, and in 

 the latter the upper molars appear to be relatively 

 as well as actually much longer anteroposteriorly 

 than in the Dragon form. 



The anteroposterior diameter of the first upper 

 molar in the type is 4.3 mm. The greatest trans- 

 verse diameters of the first and second upper 

 molars are 6.1 and 7.1 mm., respectively. 



A second maxillary portion, No. 16256, is re- 

 ferred to H. inopinatus / however, the two molars 

 it exhibits are not well preserved and add little to 

 our knowledge of this form. An isolated upper premolar, apparently 

 P*, No. 16254, may well belong to Haploconus, closely resembling this 

 tooth in H. angustiis, but a little smaller and with the lingual portion, 

 though broad, somewhat less inflated anteroposteriorly. 



A lower jaw portion, U.S.N.M. No. 15744, with Mi and Ma poorly 

 preserved, and partially obscured by ironlike matrix, appears to 

 represent Haploconus in the absence of a paraconid and in the blade- 

 like form of the protoconid on Mi. It corresponds closely in size 

 to the type of Haploconus angustus, but with Mi narrower, particu- 

 larly the anterior portion, and Mo possibl}' wider than in the Torrejon 

 form. 



Figure 28. — Haploco- 

 nus inopinatus Gaz- 

 in: Left maxillary 

 portion with IvP and 

 the greater part of 

 M2 (U.S.N.M. No. 

 15760), type speci- 

 men, lateral and oc- 

 clusal views, X 3, 

 Dragon Paleocene, 

 Utah. 



*' Jnopinatus, unexpected. 



