アメリカ自然史博物館のインスタグラム(amnh) - 4月5日 07時07分

It's time for #TrilobiteTuesday! Trilobites were clearly not the only creatures inhabiting the early Cambrian seas. In fact, more than half a billion years ago there was a veritable legion of soft-bodied animals that filled those same offshore estuaries, among them a variety of arthropods that apparently outnumbered their trilobite cousins by a significant margin. Despite such lopsided numbers, however, trilobites had a major evolutionary advantage over the likes of the delicate “lace crab” Marella, pictured here, the shrimp-like arthropod Waptia, the bizarre multi-spined creature called Hallucigenia, or the mud-dwelling worm known as Ottoia. Quite simply, trilobites possessed a hard outer shell, while the myriad soft-bodied creatures that often surrounded them on those early seabed floors did not. Thus, where trilobites were better able to fend off attacks by predators like the fast-swimming, razor-jawed giant Anomalocaris, these prolific soft-bodied morsels may have suffered the dire fate of serving as little more than a prime food source for the larger, stronger inhabitants of their domain.

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