The appearance of this first predator anticipated the end of the 

 tranquil Garden of Ediacara. The end came with the second major 

 radiation of those times, the "Cambrian explosion of animal life," 

 so well documented in the fossils of the Burgess Shale and other 

 sites such as those at Chengjiang in China. These fossils suggest 

 that within a brief period of geological time, representatives of al- 

 most every known phylum of animal life made their appearance in 

 Middle Cambrian seas. Among these animals were, of course, bur- 

 rowers and grazers, which rapidly destroyed the microbial biomats 

 that had been such a feature of shallow seas for three billion years; 

 with their introduction came what Seilacher (1999) has termed the 

 "agronomic revolution." 



But of particular relevance here was the appearance, with the 

 Cambrian radiation, of the first effective predators that the world 

 had seen. By definition, an animal is a multicellular heterotroph — 

 an organism that feeds on other living things or their remains, while 

 predators form but a subset of these. Even in the earlier Ediacaran 

 days, Kimberella was acting as a true animal, grazing off the algal 

 biomat. But to feed on other true animals will generally requires 

 active pursuit and the overpowering of reluctant prey. For this co- 

 ordinated mobility and the ability to locate evasive prey are required. 

 In other words, what are needed are sense organs. 



Predators obviously rely on a variety of senses, but for the present 

 purpose, let us consider just one, that of sight. The largest and most 

 fearsome of the Cambrian predators was Anomalocaris, growing up 

 to 50 cm long and known now from a variety of localities in dif- 

 ferent parts of the world. The expanded lateral lobes along the length 

 of the body made it an active swimmer, while the two powerful 

 appendages anterior to the mouth must have been effective in the 

 capture of prey, such as trilobites. These appendages had, in fact, 

 been described (Whiteaves, 1892) many years before the entire an- 

 imal was recognized, and each was thought to represent a phyllo- 

 carid crustacean in its own right. Now that the whole animal can be 

 examined in fossil form (Collins, 1996), it is clear that two very 

 large eyes were one of its striking features, each providing infor- 

 mation to a central coordinating nervous system. 



Eyes that are even more remarkable can be seen in fossils of 



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