Classification of Sphenodon (Tuatara)

• Phylum :- Chordata (Dorsal tubular nerve cord, notochord and gill-slits present.)
• Group :- Craniata (Definite head, Cranium with brain present.)
• Sub phylum :- Vertebrata (Vertebral column present.)
• Division :- Gnathostomata (Jaws and paired appendages present.)
• Super Class :- Tetrapoda (Paired limbs, lungs, cornified skin and bony skeleton.)
• Class :- Reptilia (Scaly vertebrates. Right and left aortic arches present. Single condyle. Pulmonary respiration. Embryo with amnion and allantois.)
• Sub Class :- Diapsida (Skull with two temporal openings separated by post-orbital and squamosal.)
• Order :- Rhynchocephalia (Living fossil, lizard-like, Ribs single headed and with uncinate processes. Vertebrae amphicentrous..)
• Family :- Sphenodontidae
• Genus :- Sphenodon

Geographical distribution

Sphenodon is found in New Zealand and specially in the islets of Bay of Plenty. Permian to Eocene and Recent.

Habit and habitat

Sphenodon lives in burrows, leads semiaquatic life. It is nocturnal and eats insects, molluscs or small invertebrates. It also produces frog-like croak. Breeding season November to February.

General Characteristics of Sphenodon (Tuatara)

• Commonly called as tuatara.
• Animal is lizard-like having dull olive-green colour with white and yellow spots and measuring about 75 cm. Body divided into head, neck, trunk and tail. Head contains eye, nostril and mouth.
• It contains scaly skin and long tail.
• Forelimbs and hind limbs adapted for walking having clawed digits.
• Several backwardly directed hook or crest like spines extend all along mid-dorsal line.
• Skull contains two complete fossae, quadrate is fixed, postfrontals are separate (only in Sphenodon) and upper jaw has beaks. Teeth acrodont. Mandibles joined by ligament. Between skull and atlas is proatlas. Sternum present and vertebrae amphicoelous. Caudal vertebrae have chevron bones.
• Eye is photosensitive.
• Anal opening transverse. Male without copulatory organ. About 10 eggs with hard white shell are laid in holes in the ground. Eggs require 13 months to hatch.

Ecological Importance

The Sphenodon, commonly known as the tuatara, is a reptile endemic to New Zealand and the sole surviving member of the order Rhynchocephalia, which thrived during the Mesozoic Era. Despite its ancient lineage and limited geographic range, the tuatara holds significant ecological importance in the ecosystems it inhabits.

1. Predator Role:
   Tuataras are nocturnal predators that feed on a variety of prey, including insects, spiders, lizards, bird eggs, and small invertebrates. By controlling the populations of these organisms, they help maintain the balance of their ecosystem.
2. Prey for Larger Species:
   In their natural habitats, tuataras may serve as prey for larger animals, including birds of prey and, historically, some native predators. This places them as an important link in the food web.
3. Seed Dispersal and Ecosystem Engineering:
   Although primarily carnivorous, tuataras occasionally consume plant material. By doing so, they may contribute to seed dispersal, aiding plant regeneration. Additionally, their burrowing behavior can aerate soil and create microhabitats for smaller organisms.
4. Keystone Species in Island Ecosystems:
   Tuataras often cohabit with burrowing seabirds, such as petrels, which nest in the same burrows. This symbiotic relationship enhances nutrient cycling, as seabird guano enriches the soil, indirectly supporting plant and insect life, which benefits the tuatara and other species.
5. Indicator of Ecosystem Health:
   As a species dependent on stable environments, the presence of tuataras indicates the health and integrity of their habitats. Changes in their populations can signal environmental issues, such as habitat degradation or the introduction of invasive species.
6. Biodiversity Support:
   The tuatara’s role as both predator and prey supports a diverse range of species within its ecosystem. Its activities help regulate populations of other animals and contribute to a balanced ecological network.
7. Scientific Importance:
   As a “living fossil,” the tuatara provides insights into reptilian evolution and the history of Earth’s biodiversity. Studying its unique physiology, such as its third “parietal eye” and long lifespan, aids in understanding evolutionary adaptations, thermoregulation, and aging processes.
8. Conservation Significance:
   Protecting the tuatara benefits the entire ecosystem. Efforts to conserve its habitat, control invasive predators like rats, and establish predator-free sanctuaries help preserve New Zealand’s unique biodiversity.

The tuatara’s ecological importance lies not only in its direct roles within its habitat but also in its contributions to scientific knowledge and conservation awareness. Safeguarding this ancient species ensures the protection of its ecosystem and the continuation of its evolutionary legacy.

Special Features

Sphenodon punctatum is an important living fossil. It has survived from pennian and is fast approaching towards extinction. It is protected by law. The tuatara contains several primitive features, such as two temporal fossae, amphicentrous vertebrae, pineal eye, uncinate processes in the rib, vomerine teeth in young, horny beak on upper jaw and absence of copulatory apparatus in males. Tuatara is close to the type from where all diapsid reptiles might have originated.

Identification

• Since this reptile has rows of spines on the back and above features, hence it is Sphenodon.