Fig. 60.–The first three cervical vertebrae of Sphenodon. 1, 2, 3, 4, Intercentra; C1-C3, centra; N1-N3 neural arches.
The whole column consists of twenty-five presacral, two sacral, and about thirty caudal vertebrae. Some of the thoracic ribs have cartilaginous uncinate processes. Three or four pairs of ribs join a typical sternum, into the antero-lateral portion of which are let in the coracoids. The sternum is raised into a low median crest which fuses with the posterior branch of the T-shaped interclavicle, while the lateral branches of the latter fuse with the clavicles. The coracoids are broad and entire, still without fenestrae or notches indicative of precoracoids. The parasternum is very elaborate; it extends from the sternum to the pubic bones, and consists of about twenty-four transverse rows, each of which is composed of a median and two lateral splint-bones. They are irregularly shaped, partly with imbricating hooks, and are firmly attached to, in fact still connected with, the deeper portions of the cutaneous scales of the belly. The three pairs of pelvic bones are fused together at the acetabulum. Pubes and ischia each form one symphysis, and these are connected with each other by partly ossified cartilage and ligaments, so that the originally heart-shaped space is divided into a pair of ovals. The lateral processes of the pubes are thick, but very short. The ischia have postero-lateral processes. There is also a mostly cartilaginous, unpaired hypo-ischium.
The fore- and hind-limbs are still primitive in structure; both pentadactyle. The carpus consists of ten, sometimes eleven pieces, according to the single or double nature of the central element. The proximal series is formed by the radiale, intermedian, and ulnare, with a pisiform. The ulna and radius remain separate. The humerus has the usual ectepicondylar in addition to the entepicondylar foramen common to all the Prosauri and Theromorpha. The hind-limbs are typically plantigrade.
The tail is capable of regeneration, as in many lizards.
The development of this reptile has recently been studied and described by Howes,[[123]] who quotes the literature bearing upon the whole subject.
A good account of the occurrence and habits of the "Tuatera" has been given by Newman.[[124]] The Maoris call it "ruatara," "tuatete," or "tuatara," the latter meaning "having spines." Formerly common on the main islands of New Zealand, they are now apparently restricted to some of the islets in the Bay of Plenty, North Island. Bush-fires, wild pigs, dogs and cats, reptile-eating Maori tribes, and the advance of civilisation, have swept them away except on some of the small uninhabited islands, difficult of access, where they dig burrows, into which they retreat at the slightest sign of danger. They sleep during the greater part of the day, are very fond of lying in the water, and they can remain below for hours without breathing. They live strictly upon animals, but these are only taken when alive and moving about. The kind of food seems to vary according to the custom or fancy of the individuals. Sir W. L. Buller observed that some of his captives stubbornly refused to eat until one day, rather accidentally, minnows were offered. Others eat insects and worms; those which live near the seashore not improbably eat also crustaceans. From November to January they lay about ten eggs–white, hard-shelled, long and oval–about 28 mm. long, in holes in the sand, where they can be warmed by the sun. They are as a rule lazy in their movements. The usual pace is a slow crawl, the belly and tail trailing on the ground, but when chasing prey they lift the whole trunk off the ground. After running, or rather "wobbling" three or four yards, they grow weary and stop. They cannot jump the smallest obstacle.
Von Haast[[125]] has carefully examined their habitations on the Chicken Islands. The Tuatara excavates its own hole, and this is shared sociably by various kinds of Petrels. The entrance to the chamber is generally 4 or 5 inches in diameter, and the passage leading into the inner chamber is 2 to 3 feet long, first descending and then ascending again. The chamber itself is one foot and a half long, by one foot wide and 6 inches high, lined with grass and leaves. The petrel lives usually on the left side, the Tuatara on the right side of the inner chamber. Whilst very tolerant of the bird with its egg and young, it does not allow another of its own kind to live in the same hole, which it is ready to defend by lying in such a manner that the head is placed where the passage widens out into the chamber. On putting one's hand or a stick into the burrow the Tuatara bites at them furiously. They can run very fast, and defend themselves with great pluck against dog or man by biting or scratching. As soon as the sun has set they leave their holes to seek food. During the night, and especially during the pairing season, they croak or grunt.
The eggs, having been deposited during the Southern summer, from November to January or February, in holes on a sunny and sandy spot, contain nearly ripe embryos in the following August. They are, however, not hatched until about thirteen months old. In the meantime they seem to undergo a kind of aestivation. The nasal chambers become blocked with proliferating epithelium, which is resorbed shortly before hatching.
I have kept half-a-dozen specimens in a green-house for several years, and have come to the conclusion that they are dull, not companionable creatures, in spite of their imposing, rather noble appearance when, with their heads erect, they calmly look about with their large, quiet eyes. Each dug its own hole in the hard ground underneath and between large stones. At dusk they sat in front of the holes or walked leisurely to the pan with the earthworms which formed their principal food. Meat they did not touch, but they killed and chewed up lizards and blind-worms. Sometimes they soaked themselves for many hours in the shallow, warm water. The skin is shed in flakes. I never found them basking in the sun, and the pineal eye, still so well developed in these strange creatures, caused them no distress when bright light was thrown upon it. They grew tame enough not to run away when found roaming about at night, but they did not like being handled, and they inflicted the most painful bites when taken up carelessly. The biggest, a male, was rather quarrelsome, grunted much, and worried the others.
Sub-Class III.–THEROMORPHA.