Lineus longissimus
The longest animal in the world is a Nemetrean worm 5 cm in width and 30 m long. One specimen found was 55 m long. Most of other ribbon worms are < 20 cm in length (the phylum median is 7.5 cm). I wonder how the evolution of such an animal can be explained by natural selection. I do not say it can't. I simply have no clue how. Say, what precisely is the adaptive value of being 55 m long?
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