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| Tuatara |
The tuatara and its fossil relatives were given the order name Rhynchocephalia, which means "beak headed," by Albert Günter of the British Museum in 1867. Tuatara, which means "peaks on the back" in Maori, is the popular name for this animal. The phrase "living fossil" is used to describe any live species of organisms that resembles a species solely known from fossils and that has no near living relatives. Living fossils include tuatara.
Only two species of the reptilian order Rhynchocephalia remain today; they are found on islands off the coast of New Zealand and in the Karori Wildlife Sanctuary in Wellington, New Zealand. Sphenodon, also known as the hatteria, is the last surviving member of this order. It evolved in the early Mesozoic era, or about 200 million years ago. The nation of New Zealand gave the tuatara strict legal protection in 1895.
the punctate Sphenodon. The Northern Tuatara's hues, which are frequently mottled and always have white spots, range from olive green to grey to dark pink or brick red. Females are 45 cm long and weigh up to 1 kg, while males measure 61 cm.
Gunther's Sphenodon. North Brother Island in Cook Strait is the only place where Brothers Island tuatara can be found; it has a population of about 400. It has a lighter body that can weigh up to 660 grammes with skin that is olive brown with yellowish spots. It can be found on Brothers Island up to 300 metres above sea level, where the environment is cool, where it lives in low woodland, scrub regions, and rock stacks. The petrel and shearwater birds that live on the island also benefit the tuatara greatly.
Habitat. The 32 offshore islands that make up the tuatara's geographic range are typically cliff-bound, regularly exposed to severe winds, and home to a naturally occurring, frequently stunted, salt- and wind-tolerant vegetation. The majority of islands are also home to a variety of sea bird species, whose guano, which is rich in nutrients, supports the island's ecosystem. Typically, tuataras live in the little petrels' nesting burrows. They eat tiny insects for food. More than 60,000 but fewer than 100,000 tuatara of all kinds and subspecies are thought to exist. The survival of tuatara is being threatened by a rodent species known as kiore (Polynesian rat, Rattus exulans), which has lately colonised a number of islands.
Morphology. The olive-colored, yellow-spotted tuatara grows to a maximum length of 2 feet (60 cm). With a spine crest running down its neck and back, it has a rather lizard-like appearance from the outside. A prominent crest runs down the back of the neck and another one runs down the middle of the back on the male tuatara. Its internal structure, scales, and teeth are very distinct from lizards'. It has a rudimentary third eye on top of its head, just like other extinct lizards. Since its teeth are accordant jaw projections, they cannot be replaced. In the lower jaw, they have a single row of teeth, while in the upper jaw, they have two rows of teeth, with the bottom row positioned between the two top rows. The jaws shear up and down in addition to moving backwards and forwards while chewing.
The notochord is still present in the cavities between the centra of the amphicoelous vertebrae. There is a third little median bone in the occipital region of the skull, the proatlas, in addition to the atlas and axis. A few ribs have an uncinate process and are single headed. The front end of the median sternum has the coracoid and interclavicle connected.
A clavicle and an intercalvicle in T shape are present. Eleven carpal bones are present: two centrals, two pisiforms, four in the proximal row, and five in the distal row. The pubic symphysis, which the cartilaginous epipubis sits in front of, connects the pubic bones of the pelvis. The ischia behind has a cartilaginous hypo ischium linked to it.
It has the longest incubation period of any reptile and lays eggs in burrows it shares with seabirds (up to 15 months). The temperature of the soil affects the sex of the offspring: warm soil generates males, whereas cooler soil produces females. Tuatara adults are nocturnal, terrestrial reptiles, yet they frequently sunbathe to warm their bodies and hibernate in the winter.
Because of their endurance for extremely cold weather, they have a very low metabolic rate, which contributes to their extended lifespan. In fact, the tuatara has the lowest body temperature range of any reptile, peaking at 12 to 17 degrees Celsius. This is likely the reason they have long thrived in New Zealand's mild environment. The tuatara grows slowly compared to other reptiles and keeps becoming bigger during the first 35 years of its life. Although they can live to be over 100 years old, the typical lifespan is about 60 years.
Food. Arthropods, earthworms, snails, bird eggs, small birds, frogs, and lizards, as well as a native insect known as a weta, make up the tuatara's diet.
The loss of the tuatara from the mainland is assumed to be due to the arrival of Polynesians about 1000 years ago and of Europeans over the course of several centuries. This is due to the fact that immigrants brought rats and dogs, who preyed on and trampled on tuataras and livestock. Sphenodon's extremely restricted capacity for reproduction has prevented it from adapting to human impact.
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