Titanothere homs had a vaiiety of shapes 

 and probably served a number of pur- 

 poses: for species recognition, as displays 

 in courtship, and as weapons during com- 

 bat with other titanotheres. 



When titanotheres fought with their 

 horns, they probably did so in one of two 

 different ways. Most titanotheres had 

 homs that were directed to the side, sug- 

 gesting that the combatants might have 

 circled one an'other while delivering lat- 

 eral blows to the unprotected flank of the 

 opponent. In other titanotheres, however, 

 the homs were directed forward, indicat- 



In the late 1920s, artist 

 Charles Knight depicted a 



magnificent bull 



titanothere, of the genus 



Megacerops, intimidating a 



would-be predator the 



carnivore Hyaenodon, at 



the edge of a watering hole. 



The rest of the titanothere 



herd dust-bathes and feeds 



in the background. 



Charles R. Knight: courtesy of the Field 

 Museum of Natural History, Neg No, 121T 



ing that these species probably fought 

 head to head, locking homs with those of 

 their adversaiy. much as deer and cattle do 

 today. Although these head-to-head con- 

 tests were primarily wrestling matches, 

 the focus of the attack probably remained 

 the opponent's flank, which would be 

 rammed with the homs if the opportunity 

 arose. The American Museum's new fos- 

 sil mammal exhibition includes a remark- 

 able titanothere skeleton belonging to the 

 genus Brontops in which one rib had been 

 broken during the life of the animal, prob- 

 ably during a sparring match with another 

 titanothere. 



At the end of the Eocene epoch, ap- 

 proximately thirty-two million years ago, 

 all titanothere species suddenly became 

 extinct. Despite their abmpt disappearance 

 from the fossil record, titanotheres were 

 not casualties of a sudden cataclysmic 

 event. Instead, their disappearance can 

 probably be explained by a simple change 

 in the earth's climate. 



The classical explanation for the extinc- 

 tion of these huge browsers holds that as 

 the Eocene passed into the Oligocene, the 

 environment became cooler and drier, 

 transfomiing the open woodland habitat 

 inhabited by the last titanotheres into rela- 



tively open grassland. Many of the trees 

 and shmbs that had fumished titanotheres 

 with their primary source of food disap- 

 peared over time, leaving only the expand- 

 ing fields of grass to provide sustenance. 

 Other perissodactyls, such as horses and 

 rhinoceroses, developed higher-crowned 

 teeth in response to this ecological chal- 

 lenge, but titanotheres never evolved a 

 tmly high-crowned tooth. With their fee- 

 ble teeth basically unmodified, titano- 

 theres were not able to efficiently utilize 

 the primary source of food, and were 

 doomed to extinction. 



In the grand scheme of things, titano- 

 theres did not survive on this planet for 

 long, but while they were here they were 

 one of the dominant herbivores and 

 thrived in great numbers. The last titano- 

 theres were among the largest land mam- 

 mals of their time and reigned virtually 

 unchallenged for six million years. Like 

 all creatures, however, they were subject 

 to nature's great dictum: Adapt to the 

 changing world or pass into obhvion. Ti- 

 tanotheres could not adapt to the rigors of 

 the new environment and passed from the 

 scene, leaving only their fossil bones to in- 

 trigue Homo sapiens, the dominant crea- 

 ture of the present era. 



62 NATimAL History 4/94 



