What Is the Three-Eyed Reptile That Survived the Dinosaurs?

The tuatara is the three-eyed reptile that survived the dinosaurs, living for over 250 million years as the sole member of the ancient order Rhynchocephalia. This remarkable New Zealand native literally has a third eye on top of its head with a functional retina and lens.

The Last of Its Kind

While lizards and snakes evolved into thousands of species, the tuatara stands alone as the only surviving member of Rhynchocephalia—an entire order of reptiles that predates the dinosaurs. Every other species in its lineage has vanished from Earth, making the tuatara one of the most significant living fossils on the planet. These ancient reptiles once dominated the world’s ecosystems, but today they exist only on small islands off New Zealand’s coast.

The Mystery of the Third Eye

Perhaps the tuatara’s most fascinating feature is its parietal eye—a literal third eye located on top of its skull. Unlike the simple light-detecting organs found in some reptiles, the tuatara’s third eye contains a genuine retina and lens, connecting directly to the brain through the pineal gland. This photosensitive organ is visible in hatchlings but becomes covered by scales as the animal matures. Scientists believe it helps regulate circadian rhythms and seasonal behaviors, though its exact function remains one of nature’s enduring mysteries.

Extreme Longevity and Slow Living

Tuataras embody the concept of “slow and steady.” These reptiles don’t reach sexual maturity until they’re 10-20 years old and continue growing for 35 years before reaching full adult size. Their eggs require 12-16 months to hatch—the longest incubation period of any reptile on Earth. Perhaps most remarkably, tuataras can live well over 100 years. Henry, a famous captive male at Southland Museum in New Zealand, fathered offspring at the incredible age of 111, proving that these ancient reptiles maintain their reproductive capabilities throughout their extended lifespans.

Climate Change Threatens Ancient Survivors

Despite surviving mass extinctions, ice ages, and countless environmental changes over 250 million years, tuataras now face their greatest threat from human-induced climate change. These reptiles lack sex chromosomes—instead, nest temperature determines gender during incubation. Warmer temperatures produce males, while cooler temperatures produce females. As global temperatures rise, scientists predict that wild tuatara populations could become predominantly or entirely male, potentially driving this ancient lineage to extinction within decades.

Unique Anatomy and Behavior

Beyond their third eye, tuataras possess several other primitive characteristics that distinguish them from modern reptiles. They have a unique jaw structure with overlapping rows of teeth that function like scissors, and they lack external ears. Their metabolic rate is remarkably low—they can hold their breath for over an hour and remain active in temperatures that would immobilize other reptiles. These adaptations helped them survive in New Zealand’s cool climate while their relatives elsewhere succumbed to changing conditions.

The tuatara represents an irreplaceable link to Earth’s ancient past, offering scientists invaluable insights into reptilian evolution and the history of life on our planet. Their survival through multiple mass extinctions makes their current vulnerability to climate change particularly poignant—a reminder that even the most resilient species can face existential threats in our rapidly changing world.