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EXPLORERS 



AGES 814 



FACES explores the lives and cultures of 

 people around the world with exciting 

 articles, tales, legends, puzzles, and 

 activities. 



"... one of 

 the most 

 innovative 

 children's 

 magazines 

 in recent 

 years." 



—PARENTS' 

 CHOICE 

 AWARD 



FACES 



^^BThe Magazine About People 



Please send check or money order payable to 

 FACES, American Museum of Natural His- 

 tory, Central Park West at 79th Street, New 

 York, NY 10024. AMNH Members pay just 

 $18.95 (foreign add $8) for a full year sub- 

 scription of 9 issues. 



Tlie most familiar of all 



sabertooths, Smilodon 



belonged to the family Felidae, 



although it was not in the same 



genus as present-day big cats. 



As recently as 12,000 years 



ago, this predator roamed 



North America, perhaps using 



its long, daggerlike canines to 



slice open it victims ' bellies. 



Illustration by Pat Ortega 



toothed predators also existed in South 

 America, with the extinct borhyaenid car- 

 nivorous marsupials (distantly related to 

 opossums) producing the leopard-sized 

 Thylacosmilus in the Pliocene-Pleis- 

 tocene. (Another interesting case is pre- 

 sented by the thylacoleonids, an Aus- 

 trahan lineage possibly related to koalas 

 and wombats. Descended from an ances- 

 tor that had lost its canines, they developed 

 caninelike incisors. Thylacoleonid 

 anatomy indicates that they, like true 

 saber-toothed ecomorphs, were heavy-set 

 predators.) 



But the real stars in the saber-toothed 

 predator game were the nimravids, an ex- 

 tinct family of placental mammals that be- 

 longed to the extant order Camivora. De- 

 spite their remarkable resemblance to true 

 cats, nimravids were only distantly related 

 to the family Felidae. Sometimes known 

 as "false sabertooths," nimravids were es- 

 pecially diverse in Eurasia and North 

 America during the Oligocene, about 

 thirty-four to twenty-three million years 

 ago. 



Bobcat to jaguar sized, nimravids were 

 in general smaller than the Pleistocene 

 saber-toothed true cats, but like the true 

 cats, they also developed two ecomorpho- 

 logical types within the broader role: a 

 more lightly built, "scimitar-toothed" 

 form with somewhat elongated, bladelike 

 canines; and a more powerful, shorter- 

 legged, "dirk-toothed" form with very 

 long, daggerlike canines, in some cases 

 supported by a corresponding flange on 

 the lower jaw. (The placental creodonts 

 and the South American marsupials 

 mostly resembled the dirk-toothed type.) 

 How these teeth were used to kill prey is a 

 subject of debate. A normal, catlike bite to 

 the top of the neck might snap the flattish 

 blades, so the saberlike teeth were prob- 

 ably used to slice open the victim's belly 

 or the underside of its neck. 



Larry Martin, of the University of 

 Kansas, has traced the iterative evolution 



80 Natural History 4/94 



