Rhynchocephalia ("beak-heads") is an order of lizard-like reptiles that includes only one living species, the tuatara (Sphenodon punctatus) of New Zealand, which is thought to have two subspecies (Sphenodon punctatus punctatus and Sphenodon punctatus guntheri) the latter was recognised as a separate species from 1989 to 2009.
Despite its current lack of diversity, the Rhynchocephalia at one time included a wide array of genera within multiple (now extinct) families, and represents a lineage stretching at least as far back as the Middle Triassic. Most rhynchocephalians belong to the group Sphenodontia ("wedge-teeth"), which are characterized by a hooked beak-like structure at the tip of the snout formed by enlarged premaxillary teeth.
Many of the niches occupied by lizards today were held by sphenodontians during the Triassic and Jurassic, although lizard diversity began to overtake sphenodontian diversity in the Cretaceous. While the modern tuatara is primarily carnivorous, there were also sphenodontians with omnivorous (Opisthias), herbivorous (Eilenodontinae), and durophagous (Oenosaurus) lifestyles. There were even several successful groups of aquatic sphenodontians, such as pleurosaurs and Ankylosphenodon.
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13 июн 2020
