MORRISON MAMMALS: PANTOTHERIA 



6i 



Lengths : 



Pi 



P., 



Measurements of Neotype 



i.o 



Depth of ramus below M^ 



1-3 1-3 

 inside 



Mo 

 1.4 



1-5 



M, 

 1.6 



M., 

 1.6 



M« 

 1.4 



M7 

 1-3 



M, 



4.2 



The molar series is crowded, each pa'' somewhat overlapping the preceding talo- 

 nid, so that the total measurement is less than the sum of the individual teeth and is 

 usually much modified by slight crushing. 



Laolesles Sitnpson 1927 

 1927. Laolestes, Simpson, Atner. Jour. Set. (5) XIH, 411. 



Definition. — Dental formula I4 Ci P4 Ms. Premolars with continuous internal 

 cingulum, without anterior accessory cusp. Metaconid of molars columnar, bifid at 

 apex; paraconid slightly procumbent, lower than mc"; pa"* and talonid cusp distinctly 

 internal relative to me''. External cingula on molars. 



Type. — Laolestes eminens Simpson. 



Distribution. — Morrison formation, Wyoming. 



This is the most common single 

 form in the Morrison mammalian 

 fauna. Although clearly quite dis- 

 tinct, it is close to Dryolestes in size 

 and in general character. The rela- 

 tively few specimens which are 

 really attributable to Dryolestes 

 were not closely studied or entirely 

 cleaned by Marsh, as the better jaws 

 of the present genus seemed to be 

 more satisfactory, and consequently 

 most of our supposed knowledge of Dryolestes was formerly based on Laolestes. Be- 

 sides the more common form, the genotype L. eminens, which varies somewhat, there is 

 a clearly distinct second species, here described as new. 



LADLE5TE5 



Fig. 25. Laolestes. Diagrammatic internal view of right 

 lower jaw. Three times natural size. 



Laolestes eminens Simpson 1927 

 1927. L. eminens, Simpson, Amer. Jour. Set. (5) XIII, 411. 



Type. — Y.P.M. No. 137 19. Left lower jaw in matrix, inner aspect, with I. 14, C, 

 Pi-3, and Mi.g — one of the finest known mammal jaws from the Mesozoic. Fig'd (as 

 Dryolestes friscus). Marsh 1887, PI. IX, fig. 2. 



Principal Referred Specimens. — Y.P.M. No. 10662. Left lower jaw with P* 

 and M1-4. 



