Tuatara: Reptiles that lived 240 million years ago

There is a reptile in New Zealand whose lineage arose at the time of the dinosaurs. Even if its external appearance is comparable to that of a lizard, the tuatara (whose title means “spiny back” from the Maori language) is a creature with many unique characteristics that classify it in an order different from another reptiles. In this entry we’ll explain the main characteristics of the relic in the past, as interesting as endangered.

Origin and Evolution

The tuataras are odd reptiles whose lineage goes back to 240 million decades ago, at the middle Triassic. Tuataras are lepidosaurs, yet they form a different lineage from the squamates, and that is why they are found in their own sequence, the rhynchocephalians (order Rhynchocephalia). Lots of species flourished during the Mesozoic, even though just about all of these were substituted by squamates. At the conclusion of the Mesozoic just one family survived, the Sphenodontidae.

Homoeosaurus fossil

Of all the current sphenodontids, just tuataras have survived to the present day. Traditionally it was considered that tuataras comprised two species: the common tuatara (Sphenodon punctatus) and the Brother’s Island tuatara (Sphenodon guntheri), though recent investigations have popularized the concept that the tuatara is just one species, S. punctatus.

Tuatara Anatomy

As we have already stated, tuataras look externally like a lizard, acquiring a certain similarity to iguanas. Male tuataras are larger than females, measuring up to 61 cm in length and one kilogramme of weight, whereas females just measure 45 cm and weigh half a kilo. Tuataras present a spiny crest in their backs which give them their common name. This crest is larger in males, and can be erected as display.

young male tuatara

What really distinguishes the tuataras is their internal anatomy. The rest of the reptiles have modified greatly their skull arrangement, but tuataras have maintained the initial diapsid configuration without most changes. While crocodiles and turtles have developed a sturdy skull, tuataras preserve wide rectal openings, and while squamates have developed elastic skulls and limbs, tuataras keep a rigid cranium. Additionally, unlike most reptiles, tuataras present no external ears.

tuatara skull

Tuatara

The title Rhynchocephalia signifies “beak head” and it refers to the beak-like structure of the premaxilla. Tuataras are also one of the very few reptiles with acrodont teeth, that can be fused into the maxilla and the jaw, and are not renewed. Furthermore, they present a distinctive saw-like jaw motion, moving it forwards and backwards.

Finally, one of the very incredible anatomic features of tuataras is that they save their parietal or pineal eyecatching. This is a construction reminiscent from the first tetrapods, which joins with the pineal gland and which is included in the thermoregulation and circadian rhythms. Even if a few other animals additionally keep it, the tuataras present a real third eye, even with full lens, cornea and retina, even if it gets coated with scales since they age.

Habitat And Biology

typical humid forest of New Zealand

Also, the previously considered species S. guntheri can be found on Brother’s Island, at the northwest of South Island. All populations live in coastal forests or scrublands, with loose soils easy to dig. Additionally, in most of their distribution region you will find colonies of sea creatures, whose nests are also employed by tuataras.

Compared with many reptiles, tuataras reside in comparatively cold habitats, with annual temperatures oscillating between 5 to 28°C. Tuataras are largely nocturnal, usually coming from their burrows at night, even if occasionally they may be found basking in sunlight throughout the day (particularly in winter).

Tuataras have few all-natural predators. Apart from some creatures that are introduced, only gulls and a few birds of prey represent a threat for these reptiles. By comparison, their diet is rather varied. Being sit-and-wait predators, tuataras feed largely on invertebrates like beetles, crickets and spiders, even if they are in a position to predate on lizards, eggs and bird girls, and even younger tuataras. As their acrodont teeth don’t renew, these have worn down in time, therefore older individuals usually feed on milder prey such as snails and worms.

The gender of the offspring depends on the incubation temperature (males at higher temperatures and females at lower ones). The eggs will hatch after 11-16 weeks (among the longest incubation phases of all reptiles), where young tuataras will be born, who’ll steer clear of the cannibalistic adults becoming active mostly during the daytime.

As we can see according to their lengthy incubation period, tuataras develop slowly. These reptiles do not reach sexual maturity until age 12, and they keep increasing. Additionally, tuataras are incredibly long-lived creatures, living around more than 60 years in the wild. In captivity they can live over 100 years.

Conservation and Threats

Prior to the arrival of guy, the tuataras exist in the main islands of New Zealand and a lot more islets. When the first European settlers came, tuataras were already just found in roughly 32 small islands. It is thought that the extinction of tuataras in the principal islands was a result of habitat destruction and into the introduction of foreign lands such as rats. Other dangers include the reduced genetic diversity brought on by isolation of the various inhabitants and climate change, which may influence the gender of their offspring.

After the first human settlers came from the isles, it’s believed that 80 percent of New Zealand was covered in woods. After the initial Polynesian tribes arrived round the year 1250, they triggered the deforestation of over half of the archipelago. Centuries later, with the advent of Europeans, deforestation intensified even longer, up to the present scenario, with just 23 percent of the first forest still maintained.

This rodent has influenced the inhabitants of the two tuataras and a lot of New Zealand’s endemic bird species. In research on coexisting populations of tuataras and rats, it’s been discovered that rats, aside from preying on eggs and hatchlings, additionally compete with mature tuataras for sources. Having a very slow life cycle, tuataras can not recover from this effect.

This is due to the fantastic efforts of conservation groups which have led to the healing of the species. So as to accomplish that, a titanic attempt was created in several islets where whole populations of tuataras were seized to take part in captive breeding programs, although the rats were removed from such islands. Following their principal threat has been eradicated, all of the captured people and their captive-born dinosaurs were published in their natural habitat in order that they could live with such a ferocious competitor.

Presently, the rampant tuatara population is anticipated to be between 60.000 and 100.000 people. It could be stated that this living fossil, that was on the edge of extinction after countless years of presence, received another chance to maintain inhabiting the amazing islands of New Zealand. We hope that in the long run, we could keep enjoying the occurrence of those reptiles, the sole survivors of a nearly extinct lineage, for a lot more centuries.