Sphenodon punctatus, better known as the tuatara, is endemic to New Zealand. They are the sole surviving species of order Rhynchocephalia, which during the Mesozoic Era had many diverse lineages. Rhynchocephalia’s origins are dated all the way back to the Triassic period, approximately 250 million years ago.

The most recent common ancestor of the tuatara is that of other squamates (snakes and lizards) where Lepidosauria diversified into the Rhynchocephalians and the Squamates. This makes them a point of interest for research into the evolution of Squamates as well as the evolution of early tetrapod life.

For indigenous Māori people, tuatara are held as Ariki, or God-forms, and seen as messengers of Whiro, the god of death and disasters. This may not sound particularly good, but it is more from a stance of respect. They are also known as taonga (special treasures) and are rooted in cultural significance there. Their name means “spiny back” in Māori.

Tuatara were almost driven to extinction, vanishing from mainland New Zealand but remaining on the smaller offshore islands. It is thought that the main driver of local extinctions was due to mammals such as rats because small mammal presence occurred at the same time as drastically reduced tuatara populations – and so efforts were made to eradicate rat populations to see if tuatara recovery was possible.

At the beginning of the 1990s, tuatara were removed from three islands and maintained in a captive environment while the Polynesian rats were culled in the areas. All of the populations bred successfully while in captive care, and the adults and juveniles were released onto their islands of origin. This appeared successful, and the same methods were applied to other island populations, but some surveys down the line showed disappointing results for the population growth of tuatara on certain islands.

A subspecies of tuatara, S. punctatus guntheri or the Brothers Island tuatara has a small population of approximately 400 individuals. Several have been moved to protected areas and zoos for captive breeding monitoring with some success.

The tuatara’s parietal eye has several structures the same as in a ‘functioning’ eye, including a nerve connection to the brain. It is covered by scales though and does not see. It is thought that the parietal eye in tuatara and also several lizards serves to detect light and UV, regulating basking behaviour and physiological rhythms.

A subspecies of tuatara, S. punctatus guntheri or the Brothers Island tuatara has a small population of approximately 400 individuals. Several have been moved to protected areas and zoos for captive breeding monitoring with some success.

Tuatara, however, have complex conditions necessary for successful reproduction. For starters, they reach sexual maturity at a slow rate (between 10 and 20 years) and have perhaps the slowest growth rates of any reptile – living up to a century in some cases. Females will only lay eggs every four years, so it’s a bit of a waiting game for captive facilities to raise their tuatara and keep them healthy and comfortable until the time is right for breeding.

Tuatara also have temperature-dependent sex determination, meaning incubation temperature decides which sex the developing embryo will become. From a conservation standpoint, it can be useful for manipulating the sex ratios of populations where needed.

It is said that 22 degrees yields primarily males and 18 degrees primarily females. Humidity also plays an important role.

Their genome was found to have between 5 and 6 million base pairs – almost twice that of humans.

Good news came recently from Chester Zoo in the UK, where the first tuatara hatchling has successfully been produced outside of the species’ homeland after 238 days of incubation. Baby Isolde was announced after a delay to be sure she would survive since hatching tuatara is notoriously difficult and breeding/incubation is not often successful.