As Spirit climbs to higher ground, the layers of rock and sand thin out and expose the lowest strata. These strata are nearly identical to those in Meridiani Planum, where Opportunity is finding so many geysers and fossils. Gusev has its share of stromatolites and other organisms, but this crinoid is one of the best yet found. Modern crinoids are often called "sea lilies" because they strongly resemble plants or flowers. In fact, crinoids are very ancient and go back about half a billion years on Earth. They are more closely related to sea urchins and starfish, and are technically echinoderms (meaning rough skin). They have a skeleton made of calcium carbonate, the same material that limestone and calcite are made of.The rounded bulb is the "head" of the creature, or the calyx. Its arms are used to filter feed by straining small organisms from the sea water. The arms are very clear also. We can confirm that these features are real and not just some trick of light and shadow. This is clearly a Martian fossil. It is very clear that Mars was a planet covered with oceans that had ancient Aquatic Life almost identical to that found on Earth nearly half a billion years ago.