小丑，杂技，马和狮子。
刺背鳄蜥的进化速率比起包括洞熊、狮子、公牛和马在内的动物，都要快得多。
The tuatara rate is significantly faster than for animals including the cave bear, lion, ox and horse.
在现代动物身上已经出现了这种现象，比如马和斑马，狮子和老虎。但是这种结合产生的后代总是没有生育能力。
The phenomenon is already seen in modern animals such as horses and zebras, and lions and tigers, but resulting offspring have always been infertile.
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