2.3.3.3.1.2.3.1.1. [Invertebrate deuterostomes] (internal skeleton without a spine) © 2003-2026 hegel.net · Kai Froeb 2.3.3.3.1.2.3.1.1. [Invertebrate deuterostomes] [Echinoderms] 2.3.3.3.1.2.3.1.1.1. [Tunicates] (sea squirts, salps: notochord only in the larva) 2.3.3.3.1.2.3.1.1.2. [Lancelets] (notochord throughout life, still no head) 2.3.3.3.1.2.3.1.1.3. One level back to Fishes and their precursors (spawn) One level further to [Echinoderms] (starfish, sea urchins, sea cucumbers, crinoids: five-rayed, headless) One level further to [Tunicates] (sea squirts, salps: notochord only in the larva) One level further to [Lancelets] (notochord throughout life, still no head)