Phys.org has a story about the origin of crinoids. Tom Guensburg, research associate at the Field Museum in Chicago, is the lead author of a paper in the Journal of Paleontology, that describes Athenacrinus browneri. This new fossil shows evidence that is key to how sea lilies evolved from the earliest known echinoderms, which lived up to 515 million years ago.
You might remember Tom spoke to ESCONI about crinoid origins back in September 2018.
Sea lilies, despite their name, aren't plants. They're animals related to starfish and sea urchins, with long feathery arms resting atop a stalk that keeps them anchored to the ocean floor. Sea lilies have been around for at least 480 million years—they first evolved hundreds of millions of years before the dinosaurs. For nearly two centuries, scientists have thought about how modern sea lilies evolved from their ancient ancestors. In a new study in the Journal of Paleontology, researchers are rewriting the sea lily family tree, aided by newly-discovered fossils that help show how these animals' arms evolved.
"These early fossils provide new key evidence showing that what we had thought about the origin of sea lilies since 1846 is wrong," says Tom Guensburg, the paper's lead author and a research associate at the Field Museum in Chicago. "It's not very often that we're challenging ideas that are almost two hundred years old."
Sea lilies are more formally known as crinoids, but they've earned their nickname—they really do look like flowers growing at the bottom of the ocean. They spend their adult lives stuck in one place, with stem-like stalks that attach them to the sea floor. At the top of these stalks are a cluster of arms, maybe the size of the palm of your hand. These arms trap tiny plankton floating through the water, which the sea lily then eats.
"Some people actually consider sea lilies and their relatives, the feather stars, the most beautiful animals. They come in any color—purple, bright red, green," says Guensburg. "They look plant-like, but when you actually look at their bodies, you find all the usual anatomy of complex animals like a digestive tract and nervous system—they're closer to vertebrates, and us, than almost any other invertebrate animals."
