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Prehistoric reptiles A loving mother 史前爬行动物 慈母 Family life in plesiosaurs 蛇颈龙的家族生活 THE Mesozoic land was dominated by dinosaurs. 中生代时期，恐龙统治着陆地。 At sea, though, the most abundant reptiles were the ichthyosaurs and plesiosaurs. 但是在海里，最繁盛的爬行动物要属鱼龙和蛇颈龙了。 Roughly speaking, these animals filled the ecological niches now occupied by toothedcetaceans such as dolphins and killer whales. 大致上讲，这些动物填补了由现代齿鲸目动物海豚和虎鲸所占据的生态龛位。 Ichthyosaurs, indeed, looked somewhat like dolphins, though plesiosaurswith their longnecks and diamond-shaped paddleswere unlike anything now alive. 鱼龙看上去的确有点象海豚，但拥有长颈和菱形鳍状前肢的蛇颈龙却与现存的任何动物不相类似。 Ichthyosaurs also resembled cetaceans in another way: unlike most living reptiles, which layeggs, they gave birth to live young. 鱼龙与鲸类动物还有另一点相似之处：大多数现存的爬行动物靠产卵繁殖，而鱼龙是通过怀胎产子的。 For years, palaeontologists have wondered if the same was true of plesiosaurs. | 
