仅仅从这些骨骼来看,他就知道棘鱼石螈和鱼石螈或其他的四足动物不同,这一点十分清楚。如果你伸开手臂,就会发现你的桡骨和尺骨展开的长度一样。鱼石螈和我们一样,这种相等的长度对于它们用四条腿在地上行走十分重要。但是棘鱼石螈的前肢对于一只四足动物来讲,却是长短十分不均衡的。它的桡骨长度是尺骨的2倍,但是作为肉鳍,却是十分合适的。 It is clear from these bones that he knows that echinoderms are different from orchids or other four-footed animals. If you extend your arm, you will find that your radius and ulna expand the same length. Like the rest of us, this equal length is very important for them to walk on the ground with four legs. However, the echinoderms forelimbs for a four-legged animal, but the length is very uneven. Its radius is 2 times the length of the ulna, but as fins, but it is very suitable.