Product Code Database
The tuatara ( Sphenodon punctatus) is a species of reptile Endemism to New Zealand. Despite its close resemblance to , it is actually the only extant member of a distinct lineage, the previously highly diverse order Rhynchocephalia. The name tuatara is derived from the Māori language and means "peaks on the back".
The single extant species of tuatara is the only surviving member of its order, which was highly diverse during the Mesozoic era. Rhynchocephalians first appeared in the fossil record during the Triassic, around 240 million years ago, and reached worldwide distribution and peak diversity during the Jurassic, when they represented the world's dominant group of small reptiles. Rhynchocephalians declined during the Cretaceous, with their youngest records outside New Zealand dating to the Paleocene. Their closest living relatives are Squamata (lizards and ). Tuatara are of interest for studying the evolution of reptiles.
Tuatara are greenish brown and grey, and measure up to from head to tail-tip and weigh up to with a spiny crest along the back, especially pronounced in males. They have two rows of teeth in the upper jaw overlapping one row on the lower jaw, which is unique among living species. They are able to hear, although no external ear is present, and have unique features in their skeleton.
Tuatara are sometimes referred to as "". This term is currently Deprecation among paleontologists and evolutionary biologists. Although tuatara have preserved the morphological characteristics of their Mesozoic ancestors (240–230 million years ago), there is no evidence of a continuous fossil record to support the idea that the species has survived unchanged since that time.
The species has between five and six billion of DNA sequence, nearly twice that of humans.
The tuatara has been protected by law since 1895. (1993). 9780478014624, Threatened Species Unit, Department of Conservation, Government of New Zealand. . ISBN 9780478014624 Tuatara, like many of New Zealand's native animals, are threatened by habitat loss and introduced predators, such as the Polynesian rat (Rattus exulans). Tuatara were extinct on the mainland, with the remaining populations confined to 32 offshore islands, until the first North Island release into the heavily fenced and monitored Karori Wildlife Sanctuary (now named "Zealandia") in 2005. During routine maintenance work at Zealandia in late 2008, a tuatara nest was uncovered, with a hatchling found the following autumn. This is thought to be the first case of tuatara successfully breeding in the wild on New Zealand's North Island in over 200 years.
Tuatara, along with other now-extinct members of the order Rhynchocephalia, belong to the superorder Lepidosauria, as do the order Squamata, which includes lizards and snakes. Squamates and tuatara both show caudal autotomy (loss of the tail-tip when threatened), and have transverse slits.
Tuatara were originally classified as lizards in 1831 when the British Museum received a skull. John Edward Gray used the name Sphenodon to describe the skull; this remains the current scientific name for the genus. Sphenodon is derived from the Greek language for "wedge" (σφήν, σφηνός/ sphenos) and "tooth" (ὀδούς, ὀδόντος/ odontos). In 1842, Gray described a member of the species as Hatteria punctata, not realising that it and the skull he received in 1831 were both tuatara.
The genus remained misclassified as a lizard until 1867, when Albert C. L. G. Günther of the British Museum noted features similar to birds, turtles, and crocodiles. He proposed the order Rhynchocephalia (meaning "beak head") for the tuatara and its fossil relatives. Since 1869, Sphenodon punctatus (or the variation Sphenodon punctatum in some earlier sources) has been used as the scientific name for the species.
At one point, many disparate species were incorrectly referred to the Rhynchocephalia, resulting in what taxonomists call a "wastebasket taxon". (1994). 9780521452427, Cambridge University Press. ISBN 9780521452427 Williston in 1925 proposed the Sphenodontia to include only tuatara and their closest fossil relatives. However, Rhynchocephalia is the older name and in widespread use today. Many scholars use Sphenodontia as a subset of Rhynchocephalia, including almost all members of Rhynchocephalia, apart from the most primitive representatives of the group.
The earliest rhynchocephalian, Wirtembergia, is known from the Middle Triassic of Germany, around 240 million years ago. During the Late Triassic, rhynchocephalians greatly diversified, going on to become the world's dominant group of small reptiles during the Jurassic period, when the group was represented by a diversity of forms, including the aquatic Pleurosauridae and the herbivorous Eilenodontinae. The earliest members of Sphenodontinae, the clade which includes the tuatara, are known from the Early Jurassic of North America. The earliest representatives of this group are already very similar to the modern tuatara. Rhynchocephalians declined during the Cretaceous period, possibly due to competition with mammals and lizards, with their youngest record outside of New Zealand being of Kawasphenodon, known from the Paleocene of Patagonia in South America.
A species of sphenodontine is known from the Miocene Saint Bathans fauna from Otago in the South Island of New Zealand. Whether it is referable to Sphenodon proper is not entirely clear, but it is likely to be closely related to tuatara. The ancestors of the tuatara were likely already present in New Zealand prior to its separation from Antarctica around 82–60 million years ago.
Cladogram of the position of the tuatara within Sphenodontia, after Simoes et al., 2022:
An extinct species of Sphenodon was identified in November 1885 by William Colenso, who was sent an incomplete subfossil specimen from a local coal mine. Colenso named the new species S. diversum. Fawcett and Smith (1970) consider it a synonym to the subspecies, based on a lack of distinction.
Their lungs have a single chamber with no bronchi.
The tuatara's greenish brown colour matches its environment, and can change over its lifetime. Tuatara shed their skin at least once per year as adults, and three or four times a year as juveniles. Tuatara sexes differ in more than size. The spiny crest on a tuatara's back, made of triangular, soft folds of skin, is larger in males, and can be stiffened for display. The male abdomen is narrower than the female's.
The tip of the upper jaw is chisel- or beak-like and separated from the remainder of the jaw by a notch, this structure is formed from fused teeth, and is also found in many other advanced rhynchocephalians. The teeth of the tuatara, and almost all other rhynchocephalians, are described as acrodont, as they are attached to the apex of the jaw bone. This contrast with the pleurodont condition found in the vast majority of lizards, where the teeth are attached to the inward-facing surface of the jaw. The teeth of the tuatara are extensively fused to the jawbone, making the boundary between the tooth and jaw difficult to discern, and the teeth lack roots and are not replaced during the lifetime of the animal, unlike those of pleurodont lizards. It is a common misconception that tuatara lack teeth and instead have sharp projections on the jaw bone; histology shows that they have true teeth with enamel and dentine with pulp cavities. As their teeth wear down, older tuatara have to switch to softer prey, such as , , and , and eventually have to chew their food between smooth jaw bones.
The tuatara possesses palatal dentition (teeth growing from the bones of the roof of the mouth), which is ancestrally present in reptiles (and generally). While many of the original palatal teeth present in reptiles have been lost, as in all other known rhynchocephalians, the row of teeth growing from the in the tuatara have been enlarged, and as in other members of Sphenodontinae the palatine teeth are orientated parallel to the teeth in the maxilla; during biting the teeth of the lower jaw slot between the two upper tooth rows. The structure of the jaw joint allows the lower jaw to slide forwards after it has closed between the two upper rows of teeth. This mechanism allows the jaws to shear through chitin and bone.
The brain of Sphenodon fills only half of the volume of its endocranium. (2025). 9780253339072, Indiana University Press. ISBN 9780253339072 This proportion has been used by paleontologists trying to estimate the volume of dinosaur brains based on fossils. However, the proportion of the tuatara endocranium occupied by its brain may not be a very good guide to the same proportion in Mesozoic dinosaurs since modern birds are surviving dinosaurs but have brains which occupy a much greater relative volume in the endocranium.
Of all extant tetrapods, the parietal eye is most pronounced in the tuatara. It is part of the pineal complex, another part of which is the pineal gland, which in tuatara secretes melatonin at night. Some have been shown to use their pineal bodies to perceive polarised light, and thus determine the position of the sun, even under cloud cover, aiding navigation.
The tuatara has gastralium, rib-like bones also called gastric or abdominal ribs, the presumed ancestral trait of diapsids. They are found in some , where they are mostly made of cartilage, as well as crocodiles and the tuatara, and are not attached to the spine or thoracic ribs. The true ribs are small projections, with small, hooked bones, called uncinate processes, found on the rear of each rib. This feature is also present in birds. The tuatara is the only living tetrapod with well-developed gastralia and uncinate processes.
In the early tetrapods, the gastralia and ribs with uncinate processes, together with bony elements such as bony plates in the skin (osteoderms) and (collar bone), would have formed a sort of exoskeleton around the body, protecting the belly and helping to hold in the guts and inner organs. These anatomical details most likely evolved from structures involved in locomotion even before the vertebrates ventured onto land. The gastralia may have been involved in the breathing process in early amphibians and reptiles. The pelvis and shoulder girdles are arranged differently from those of lizards, as is the case with other parts of the internal anatomy and its scales.
Tuataras are parasitised by the tuatara tick ( Archaeocroton sphenodonti), a tick that directly depends on tuataras. These ticks tend to be more prevalent on larger males, as they have larger home ranges than smaller and female tuatara and interact with other tuatara more in territorial displays.
Tuatara eggs have a soft, parchment-like 0.2 mm thick shell that consists of calcite crystals embedded in a matrix of fibrous layers. It takes the females between one and three years to provide eggs with yolk, and up to seven months to form the shell. It then takes between 12 and 15 months from copulation to hatching. This means reproduction occurs at two- to five-year intervals, the slowest in any reptile. Survival of embryos has also been linked to having more success in moist conditions. Wild tuatara are known to be still reproducing at about 60 years of age; "Henry", a male tuatara at Southland Museum in Invercargill, New Zealand, became a father (possibly for the first time) on 23 January 2009, at age 111, with an 80 year-old female.
The sex of a hatchling depends on the temperature of the egg, with warmer eggs tending to produce male tuatara, and cooler eggs producing females. Eggs incubated at have an equal chance of being male or female. However, at , 80% are likely to be males, and at , 80% are likely to be females; at all hatchlings will be females. Some evidence indicates sex determination in tuatara is determined by both genetic and environmental factors.
Tuatara probably have the slowest growth rates of any reptile, continuing to grow larger for the first 35 years of their lives. The average lifespan is about 60 years, but they can live to be well over 100 years old; tuatara could be the reptile with the second longest lifespan after tortoises. Some experts believe that captive tuatara could live as long as 200 years. This may be related to genes that offer protection against reactive oxygen species. The tuatara genome has 26 genes that encode and 4 selenocysteine-specific tRNA genes. In humans, selenoproteins have a function of antioxidation, redox regulation and synthesis of thyroid hormones. It is not fully demonstrated, but these genes may be related to the longevity of this animal or may have emerged as a result of the low levels of selenium and other trace elements in the New Zealand terrestrial systems.
The genes of the major histocompatibility complex (MHC) are known to play roles in disease resistance, mate choice, and kin recognition in various vertebrate species. Among known vertebrate genomes, MHCs are considered one of the most polymorphic. In the tuatara, 56 MHC genes have been identified; some of which are similar to MHCs of amphibians and mammals. Most MHCs that were annotated in the tuatara genome are highly conserved, however there is large genomic rearrangement observed in distant lepidosaur lineages.
Many of the elements that have been analyzed are present in all , most are mammalian interspersed repeats or MIR, specifically the diversity of MIR subfamilies is the highest that has been studied so far in an amniote. 16 families of SINEs that were recently active have also been identified.
The tuatara has 24 unique families of , and at least 30 subfamilies were recently active. This diversity is greater than what has been found in other amniotes and in addition, thousands of identical copies of these transposons have been analyzed, suggesting to researchers that there is recent activity.
The genome is the second largest known to reptiles. Only the Greek tortoise genome is larger. Did Lizards Follow Unique Pathways in Sex Chromosome Evolution? Around 7,500 LTRs have been identified, including 450 endogenous retroviruses (ERVs). Studies in other Sauropsida have recognised a similar number but nevertheless, in the genome of the tuatara it has been found a very old clade of retrovirus known as Spumavirus.
More than 8,000 non-coding RNA-related elements have been identified in the tuatara genome, of which the vast majority, about 6,900, are derived from recently active transposable elements. The rest are related to ribosomal, Spliceosome and signal recognition particle RNA.
The mitochondrial genome of the genus Sphenodon is approximately 18,000 bp in size and consists of 13 protein-coding genes, 2 ribosomal RNA and 22 transfer RNA genes.
DNA methylation is a very common modification in animals and the distribution of within genomes affects this methylation. Specifically, 81% of these CpG sites have been found to be methylated in the tuatara genome. Recent publications propose that this high level of methylation may be due to the amount of repeating elements that exist in the genome of this animal. This pattern is closer to what occurs in organisms such as zebrafish, about 78%, while in humans it is only 70%.
The recent discovery of a tuatara hatchling on the mainland indicates that attempts to re-establish a breeding population on the New Zealand mainland have had some success. The total population of tuatara is estimated to be between 60,000 and 100,000.
In the Hen and Chicken Islands, Polynesian rats were eradicated on Whatupuke in 1993, Lady Alice Island in 1994, and Coppermine Island in 1997. Following this program, juveniles have once again been seen on the latter three islands. In contrast, rats persist on Hen Island of the same group, and no juvenile tuatara have been seen there as of 2001. In the Alderman Islands, Middle Chain Island holds no tuatara, but it is considered possible for rats to swim between Middle Chain and other islands that do hold tuatara, and the rats were eradicated in 1992 to prevent this. Another rodent eradication was carried out on the Rangitoto Islands east of D'Urville Island, to prepare for the release of 432 Cook Strait tuatara juveniles in 2004, which were being raised at Victoria University as of 2001.
In late October 2007, 50 tuatara collected as eggs from North Brother Island and hatched at Victoria University were being released onto Long Island in the outer Marlborough Sounds. The animals had been cared for at Wellington Zoo for the previous five years and had been kept in secret in a specially built enclosure at the zoo, off display.
There is another out of country population of Brothers Island tuatara that was given to the San Diego Zoological Society and is housed off-display at the San Diego Zoo facility in Balboa. No successful reproductive efforts have been reported yet.
A mainland release of S.p. punctatus occurred in 2005 in the heavily fenced and monitored Karori Sanctuary. The second mainland release took place in October 2007, when a further 130 were transferred from Stephens Island to the Karori Sanctuary. In early 2009, the first recorded wild-born offspring were observed.
Several tuatara breeding programmes are active in New Zealand. Southland Museum and Art Gallery in Invercargill was the first institution to have a tuatara breeding programme; starting in 1986 they bred S. punctatus and have focused on S. guntheri more recently.
Hamilton Zoo, Auckland Zoo and Wellington Zoo also breed tuatara for release into the wild. At Auckland Zoo in the 1990s it was discovered that tuatara have temperature-dependent sex determination.
The Victoria University of Wellington maintains a research programme into the captive breeding of tuatara, and the Pūkaha / Mount Bruce National Wildlife Centre keeps a pair and a juvenile.
The WildNZ Trust has a tuatara breeding enclosure at Ruawai. One notable captive breeding success story took place in January 2009, when all 11 eggs belonging to 110 year-old tuatara Henry and 80 year-old tuatara Mildred hatched. This story is especially remarkable as Henry required surgery to remove a cancerous tumour in order to successfully breed.
In January 2016, Chester Zoo, England, announced that they succeeded in breeding the tuatara in captivity for the first time outside its homeland.
The tuatara was featured on one side of the New Zealand five-cent coin, which was phased out in October 2006. Tuatara was also the name of the Journal of the Biological Society of Victoria University College and subsequently Victoria University of Wellington, published from 1947 until 1993. It has now been digitised by the New Zealand Electronic Text Centre, also at Victoria.
Brothers Island tuatara
Sphenodon punctatus guntheri is present naturally on one small island with a population of approximately 400. In 1995, 50 juvenile and 18 adult Brothers Island tuatara were moved to Titi Island in Cook Strait, and their establishment monitored. Two years later, more than half of the animals had been seen again and of those all but one had gained weight. In 1998, 34 juveniles from captive breeding and 20 wild-caught adults were similarly transferred to Matiu/Somes Island, a more publicly accessible location in Wellington Harbour. The captive juveniles were from induced layings from wild females.
Northern tuatara
S. punctatus punctatus naturally occurs on 29 islands, and its population is estimated to be over 60,000 individuals. In 1996, 32 adult northern tuatara were moved from Moutoki Island to Moutohora Island. The carrying capacity of Moutohora is estimated at 8,500 individuals, and the island could allow public viewing of wild tuatara. In 2003, 60 northern tuatara were introduced to Tiritiri Matangi Island from Middle Island in the Mercury Islands. They are occasionally seen sunbathing by visitors to the island.
Captive breeding
The first successful breeding of tuatara in captivity is believed to have achieved by Sir Algernon Thomas at either his University offices or residence in Symonds Street in the late 1880s or his new home, Trewithiel, in Mount Eden in the early 1890s.
Cultural significance
Tuatara feature in a number of indigenous legends, and are held as ariki (God forms). Tuatara are regarded as the messengers of Whiro, the deity of death and disaster, and Māori women are forbidden to eat them. Tuatara also indicate tapu (the borders of what is sacred and restricted), beyond which there is mana, meaning there could be serious consequences if that boundary is crossed. Māori women would sometimes tattoo images of lizards, some of which may represent tuatara, near their genitals. Today, tuatara are regarded as a taonga (special treasure) along with being viewed as the kaitiaki (guardian) of knowledge.
In popular culture
See also
Notes
Further reading
(2025). 9780931625435, Dimi Press. ISBN 9780931625435
(1997). 9780864733030, Victoria University Press. ISBN 9780864733030
(1987). 9780868680989, Dunedin, New Zealand: John McIndoe. ISBN 9780868680989
(2025). 9781869488314, Reed Children's Books. ISBN 9781869488314
External links
|
|
