June 25, 2013 at 7:51 PM ET
A new fossil relative of the starfish has turned up in 500 million-year-old sediments of the mountains in Morocco.
"It's standing upright like a candle, or large cigar sticking out of the sediment," Andrew Smith, a paleobiologist at London's Natural History Museum and a member of the team that uncovered the fossil, told NBC News.
The starfish relative lived at the bottom of the ocean surrounding the supercontinent of Gondwana about 500 million years ago, anchored by a short stem to the sea bed. The creature is described in the Wednesday issue of the Proceedings of the Royal Society: B.
The oceans in that Cambrian period were exploding with hard-shelled creatures of all shapes and sizes. There were trilobites, sponges and brachiopods — double-shelled creatures that looked like mollusks — and among them, the newly discovered "Helicocystis."
Like today's starfish and sea urchins and brittle stars, the animal was a true member of the ancient phylum "Echinodermata," meaning "spiny skinned," with rows of small plates made of calcium arranged on the outside of its body, which was between 5 and 20 millimeters long. The plates were arranged in a spiral, which would have allowed the animal to stretch and contract, sucking in gulps of ocean and filtering bits of food, Smith explains.
Smith sees Helicocystis as a "bridge species," sort of an evolutionary rough draft for the life forms that would appear after it.
The earliest known relatives of echinoderms were various spirally plated species recovered from early Cambrian sediments in California, but looked nothing like modern animals today — until the Moroccan specimen came along, bearing similarities to both the ancient spiral creatures and echinoderms today.
"It shows that body form diversity of different types was very rapid in this time, much faster than you'd expect today," Smith said.
Like starfish or an ocra fruit, the animal was symmetrical in five directions. But that symmetry was merely skin-deep: If you sliced it open, you'd see a single coiled gut, Smith said, "No nice star fruit I'm afraid."
Andrew Smith and Samuel Zamora are authors of "Cambrian spiral-plated echinoderms from Gondwana reveal the earliest pentaradial body plan" published in the Proceedings of the Royal Society: B.