Rhynchocephalians are one of the four orders that define the family of animals known as reptiles. Although rhynchocephalians are an ancient order dating back 240 million years, the order suffered mightily and mostly disappeared around 60 million years ago. The only remaining rhynchocephalians are tuataras, all of which live in New Zealand, and of those, they only still exist on islands that have not been invaded by rats.
Although the remaining tuataras have many unusual features due to their isolation on island similar to the unusual evolutionary changes on the Galapagos, the word rhynchocephalia refers to their defining characteristic: their horned beak-like snout. The word rhynchocephalia comes from the Ancient Greek word rhyncho meaning beak and kephalos meaning head.
Image of a modern rhynchocephalian, the tuatara of New Zealand courtesy Sid Mosdell, used with permission under a Creative Commons 3.0 license.