36 EXTINCT AND VANISHING MAMMALS 



Family MEGALOCHNIDAE : Ground Sloths 

 SMALLER PUERTO RICAN GROUND SLOTH 



ACRATOCNUS ODONTRIGONUS Anthony 



Acratocnus odontrigonus Anthony, Ann. New York Acad. Sci., vol. 27, p. 195, Aug. 9, 

 1916 ("Cueva de la Ceiba, near Utuado, Porto Rico"). 



FIGS.: Anthony, H. E., 1916, pis. 7-10, pi. 11, fig. 1; 1918, figs. 43-48, 50-54 (except 

 those of A. major'); pi. 69, figs, la-c; pi. 70, figs. 2-6; pi. 71, figs. 1, 3-6; pi. 72, 

 figs. 1, 3, 4; pi. 73, figs. 1-3, 5, 7; pi. 74, figs. 1-4 (skeletal parts). 



LARGER PUERTO RICAN GROUND SLOTH 

 ACRATOCNUS MAJOR Anthony 



Acratocnus major Anthony, Mem. Amer. Mus. Nat. Hist., ser. 2, vol. 2, p. 412, 1918 



("Cave . . . near Utuado, Porto Rico"). 

 FIGS.: Anthony, H. E., 1918, figs. 42, 43, 48, 49, 51, 53 (parts pertaining to No. 17169); 



pi. 69, figs. 2a^c; pi. 70, figs. 1, 7, 8; pi. 71, fig. 2; pi. 72, figs. 2a-b, 5; pi. 73, figs. 



4,6. 



HISPANIOLAN GROUND SLOTH 

 ACRATOCNUS (?) COMES Miller 



Acratocnus (?) comes Miller, Smithsonian Misc. Coll., vol. 81, no. 9, p. 26, Mar. 30, 



1929 ("Large cave near St. Michel, Haiti"). 

 FIGS.: Miller, 1929a, pi. 5, fig. 2; pi. 6, fig. 2; pi. 8, fig. 1; pi. 10, fig. 1 (limb bones and 



atlas). 



Among the most interesting finds of recent years is the dis- 

 covery of bones in the caves of Puerto Rico and Haiti repre- 

 senting a small ground sloth, which was evidently contem- 

 porary with aboriginal culture. It was approximately the 

 size of a two-toed sloth but represented the ground-living 

 group, known from the mainland of North America by the 

 gigantic mylodons of the Pleistocene era. The nearest rela- 

 tives seem to be the small ground sloths of the genus Hapalops 

 from Miocene formations of Patagonia, although there are 

 various differences. Their presence on both Puerto Rico and 

 Hispaniola is additional evidence of the faunal affinities of 

 these two islands, and since the three forms hitherto described 

 seem closely allied, they may be considered under a single head. 



The smaller ground sloth of Puerto Rico was the first 

 described and is the best known, from abundant skeletal 

 remains found in the cave earth during excavations originally 

 undertaken in the course of archeological research. As in the 

 living tree sloths, the premaxillae were toothless, and the 



