page_title: Rhynchocephalia
section_title: Classification
hierarchical_section_title: Rhynchocephalia / Classification
caption_attribution_description: English: Henry, the world's oldest Tuatara in captivity at Invercargill, New Zealand
context_page_description: Rhynchocephalia is an order of lizard-like reptiles that includes only one living species, the tuatara of New Zealand, which is thought to have two subspecies 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 families, and represents a lineage stretching at least as far back as the Middle Triassic. Most rhynchocephalians belong to the group Sphenodontia, 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, herbivorous, and durophagous lifestyles. There were even several successful groups of aquatic sphenodontians, such as pleurosaurs and Ankylosphenodon.
context_section_description: Sphenodonts, and their sister group Squamata (which includes lizards, snakes and amphisbaenians), belong to the superorder Lepidosauria, the only surviving taxon within Lepidosauromorpha. Squamates and sphenodonts both show caudal autotomy (loss of the tail-tip when threatened), and have transverse cloacal slits. The origin of the sphenodonts probably lies close to the split between the Lepidosauromorpha and the Archosauromorpha. Though they resemble lizards, the similarity is superficial, because the group has several characteristics unique among reptiles. The typical lizard shape is very common for the early amniotes; the oldest known fossil of a reptile, Hylonomus, resembles a modern lizard. R.L. Ditmars, Litt.D, says; "The Tuatara resembles in form stout-bodied modern lizards, which we might call iguanas; this resemblance is further intensified by a row of spines upon the back. It is dark olive, the sides sprinkled with pale dots. The eye has a cat-like pupil. Large specimens are two and a half feet long. While superficial resemblance might tend to group this reptile with lizards, its skeleton and anatomy show it to belong to a different part of a technical classification."
caption: Tuatara, Sphenodon punctatus
exif: {"Image Make": "NIKON CORPORATION", "Image Model": "NIKON D70", "Image Orientation": "Horizontal (normal)", "Image XResolution": "300", "Image YResolution": "300", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS2 Windows", "Image DateTime": "2008:08:07 18:04:45", "Image YCbCrPositioning": "Co-sited", "Image CustomRendered": "Normal", "Image ExposureMode": "Auto Exposure", "Image WhiteBalance": "Auto", "Image DigitalZoomRatio": "1", "Image FocalLengthIn35mmFilm": "142", "Image SceneCaptureType": "Standard", "Image GainControl": "Low gain up", "Image Contrast": "Normal", "Image Saturation": "Normal", "Image Sharpness": "Normal", "Image SubjectDistanceRange": "0", "Image ExifOffset": "368", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "922", "Thumbnail JPEGInterchangeFormatLength": "8879", "EXIF ExposureTime": "1/640", "EXIF FNumber": "28/5", "EXIF ExposureProgram": "Aperture Priority", "EXIF ExifVersion": "0221", "EXIF DateTimeOriginal": "2007:11:22 12:48:25", "EXIF DateTimeDigitized": "2007:11:22 12:48:25", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "4", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "4", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire", "EXIF FocalLength": "95", "EXIF SubSecTime": "10", "EXIF SubSecTimeOriginal": "10", "EXIF SubSecTimeDigitized": "10", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "1500", "EXIF ExifImageLength": "1946", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CVAPattern": "[0, 2, 0, 2, 2, 1, 1, 0]"}