amphioxus

/ˌæmfiˈɒksəs/
noun
  1. A small, fish-like marine animal (also called a lancelet) that has a simple body structure and is considered a primitive relative of vertebrates.
    • Scientists discovered that the amphioxus has a notochord, a feature shared with early vertebrate ancestors.
    • The amphioxus is often studied in biology classes to understand the evolution of vertebrates.
    • While snorkeling, the marine biologist spotted an amphioxus buried in the sand.
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