Bridge lizard

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Bridge lizard
Bridge lizard (Sphenodon punctatus)

Bridge lizard ( Sphenodon punctatus )

Superordinate : Scale lizards (Lepidosauria)
Order : Sphenodontia
Family : Sphenodontidae
Genre : Bridge lizards
Type : Bridge lizard
Scientific name of the  genus
Gray , 1831
Scientific name of the  species
Sphenodon punctatus
( Gray , 1842)

The bridge lizard or tuatara ( Sphenodon punctatus ) is the only recent species in the Sphenodontidae family . These animals, which are only found on New Zealand islands, are often referred to as “ living fossils ” because they are survivors of a relatively diverse group, the Sphenodontia , which flourished more than 150 million years ago. Basic morphological peculiarities compared to other recent representatives of the reptiles , especially the presence of a lower temporal arch , which as a "bridge" has an eponymous meaning and differentiates it from the scaled crawfish (Squamata), which is quite similar in habit , justify the classification in a separate order (the same Sphenodontia, also known as Rhynchocephalia). In contrast to many other cold-blooded reptiles, they are active even at low temperatures and, despite the significantly lower body heat, are able to actively search for prey such as arthropods or bird eggs. In contrast to their morphology, relatively little is known about the way of life of the endangered bridge lizards .


The generic name Sphenodon is composed of the ancient Greek words σφήν sphén , German 'wedge' and ὀδούς odous , German 'tooth' . The species epithet punctatus is Latin and means 'dotted'. The trivial name “Tuatara” comes from the Maori language , means “prickly back” and refers to the prickly back crest of the animals. The German common name "Brückenechse" was introduced in 1868 by Eduard von Martens . It points to the two complete "bone bridges" (temporal arches) in the windowed rear part of the skull of these animals (see →  skeleton ).


Bridge lizard

Bridge lizards are on average 50 to 75 centimeters long and weigh about one kilogram, while males are slightly larger. They are sturdy, clumsy lizards with a dorsal crest made of elongated horn plates. The front skull is slightly elongated like a beak. They have a grayish base color.


The skin of the bridge lizards is similar to that of the scalloped reptiles. The subcutaneous tissue usually has horizontally running connective tissue fibers and lies loosely on the muscles below it. The dermis is very thick and has larger bundles of connective tissue fibers. Most of the large, branched chromatophores lie under the dermis . Their granular, black to brown pigment content can cause a physical change in color through contraction and expansion. Even if smaller there, the chromatophores can be traced into the stratum corneum . Dorsally, the epidermis forms a number of granular scales , which reach their maximum size on the toes. Skin folds arranged along the sides of the body have pointed tubercle scales . The scaling of the ventral side consists of almost square labels. From the occiput over the back of the body there is a ridge that consists of prickly scales and is higher in males. Bridge lizards only molt once or twice a year.


Dorsal and lateral view of the skull of a bridge lizard. Scheme. The upper of the two temple windows can only be seen narrowly in the lateral view.

The diapside skull of bridge lizards differs fundamentally from the skull of the other scaled lizards due to the presence of two fully developed temporal arches . It therefore does not have the "push rod system" that characterizes the relatively strong ( kinetic ) skull of the other scaled lizards. For this reason, among other things, the bridge lizards are also placed in a separate subgroup of the scale lizards in the system , the sphenodontia . In fact, the skull of the bridge lizards is akinetic, which means that the upper jaw and roof of the mouth cannot move against the skull. However, there are still joints between the skull components in embryos , which is why the rigid skull of adult bridge lizards is often interpreted as an adaptation to the burrowing lifestyle and diet. In connection with the way of life there are also two bony, downwardly directed processes at the front end of the premaxillary (part of the upper jaw ), on which functional “ incisors ” sit, which gives the muzzle part of the skull the typical hook-beak-like appearance when viewed from the side. The dentition is acrodontic, which means that the teeth are fused with the upper edge of the jaw. Bridge lizards do not change their teeth , which means that conclusions can be drawn about age from the condition of the teeth. Old bridge lizards only have a chewing bar left. On the outer edges of the palatine bones there is a row of teeth with eleven or twelve teeth parallel to the posterior teeth of the maxillaria. Older males can also have one or two teeth on the ploughshare . At the front end of the dentary (the tooth-bearing part of the lower jaw) there is a kind of canine tooth, which is very different from the serrated pointed row of teeth there. When you bite, the row of teeth in the lower jaw grips precisely into the gap between the row of maxillary and palatal teeth. Since bridge lizards can push their lower jaw forwards and backwards and thus cut up ("saw up") the prey instead of tearing it, it is possible for them to crack the hard chitin shells of large insects and to sever small lizards.

In contrast to the scale creeps, the splenial, the seventh element of the lower jaw, is missing in bridge lizards . Particularly noticeable on the skull of bridge lizards is a large hole in the crown ( foramen parietale ) for the crown eye . The triangular square , designed as a thin bone plate, is perpendicular to the median plane of the skull and is reinforced dorsally by the wing bone and squamosum. Ventrally, the quadratum together with the quadratojugale forms a joint surface for the articulating element ( articular ) of the lower jaw.

The postcranial skeleton (skeleton without skull) of the bridge lizards is characterized by a spine with 27 precaudal (in front of the tail) vertebrae made up of 8 cervical , 17 trunk and two cross vertebrae . A rudiment of the Proatlas is characteristic of the first cervical vertebra ( atlas ) . As with some other scaled crawfish, the tail can be thrown off for self-protection ( autotomy ), whereby the regenerated material is supported by a transparent cartilage rod. From the fourth cervical vertebra, bridge lizards have short cervical ribs . The ribs of the trunk show cartilage-like, wing-like widenings in bridge lizards. These overlap and thus form a kind of armor for the body cavity. The ninth to twelfth ribs are attached to the bottom of the sternum .

Nervous system

The brain of the bridge lizards is much smaller than the volume of the cerebral skull surrounding it and much more primitive than the brain of other scale crawfish. The endbrain continues in very long olfactory tracts that end in thick olfactory bulbs . The roof of the midbrain ( tectum mesencephali ) is much lower than that of scale creeps. The fifth, seventh, eighth, ninth, and tenth cranial nerves are very similar in their location to those of amphibians and fish .

They share a special sense organ, the crown eye, only with a few other reptiles and lampreys . It has a lens-like epithelial layer, which is joined by a basal, retinal- like part. A thin nerve parietal directs the stimuli to the diencephalon . With this sense organ you can only perceive brightness, but that is probably more delicate than "normal" eyes. In addition, the vertex eye could be used to regulate the heat balance.

The large eyes of bridge lizards sit in a corresponding eye socket . In contrast to the scallops, the retractor bulbi muscle has two attachments to the eyeball . There is no lacrimal gland for moistening the outer eyes, but bridge lizards have a functional Harder's gland behind the eyeball , which produces an oily secretion and thus keeps the nictitating skin slippery. Excess moisture is drained away by the tear ducts and the nasal duct , which lead into the nasal cavity . Both eyelids are present, but the lower one is significantly larger and more developed. The transparent nictitating membrane is connected to the so-called bursal muscle by a nictitating skin tendon , which moves the nictitating membrane. The pupil, which is usually slit due to the incidence of light, is not an indication of pure nighttime activity, but rather that it is mainly nocturnal hunting activity. The retina does not contain rods and cones , but two different types of cones , which means that the animals can see very well during the day and at night, but color vision is not or only rudimentary . Behind the retina there is a layer of cells called tapetum lucidum , which acts as a residual light amplifier by reflecting the light penetrating through the retina .

The nose of bridge lizards has a second larger enlargement behind the nasal vestibule ( vestibulum nasi ).

The taste buds of the bridge lizards are mainly on the palatal mucosa. In contrast to many other reptiles, the non-split tongue is not used for licking and therefore for chemosensory orientation (see also Jacobson organ ).

Although bridge lizards have no external ear opening and no superficial eardrum , they hear well. The spacious middle ear is connected to the pharynx via the eustachian tube . The rest of the structure is essentially identical to that of the scallops.

Circulatory system and metabolic system

Consisting of the sinus venosus , a heart chamber ( Ventriculus cordis ) and two atria ( Atria existing) heart of Tuataras is by far its advanced position at the height of the shoulder girdle characterized. Three hollow veins open into the sinus venosus . Seen from above, the atria look like a single sac, but they are completely separated on the inside by a well-developed atrial septum . The heart chamber, separated from the atria by a clear coronary furrow ( sulcus coronarius ), is thick-walled and muscular; inside it shows hardly any septa, a plesiomorphism . Other peculiarities are a well-developed carotid duct and ductus arteriosus on each side and the origin of the right and left carotid arteries from a right aortic arch . The origin of the laryngeal artery from the pulmonary arch is, like the aforementioned special vascular systems, a plesiomorphism.

The breathing apparatus of the bridge lizards is original. The larynx is formed by an unpaired cricoid cartilage and a pair of adjusting cartilage , the trachea is supported by cartilaginous braces. The trachea leads through a short bronchus on both sides into the two lungs , which are only thin-walled sacs. The inner surface of the two lungs is covered by a network of honeycomb-like spaces, which become larger towards the rear. With the help of the larynx cartilage, the otherwise mute animals can make sounds when they exhale to defend themselves against enemies and to communicate with fellow animals.

The simply constructed digestive system of the bridge lizards consists, among other things, of a widely stretchable esophagus which leads into the long, spindle-shaped stomach . The small intestine lies in two to three loops in the right part of the abdominal cavity. The large intestine opens into the feces space ( coprodaeum ) of the cloaca .

The left kidney in bridge lizards is almost twice as large as the right. A short ureter opens into the urinary space ( urodaeum ) of the cloaca. These mouths are common to the sperm ducts in males , but separate from the fallopian tubes in females .

Genital organs

The internal genital organs in particular do not show any particular specialization. Although females have the ability to store sperm, no special organ can be found for this. The males lack a copulatory apparatus, an unpaired penis has been lost secondarily, paired hemipenes such as those in scaly creepers are also not present in the embryonic stages. In both sexes there are sometimes anal glands interpreted as hemipenis homologs, which probably produce sebum.

Way of life

Sphenodon punctatus , slit pupils clearly visible


Bridge lizards are mainly crepuscular or nocturnal, which is not least due to their large eyes with slit-like pupils. They often dig their own burrows in humus-like soil, where they spend most of the day. Contrary to popular belief, they rarely live in seabird burrows, see below for more on this .

Tuataras move very slowly. They walk with protruding legs and lateral wave movements of their tail and trunk, which drag on the ground. For a short time they can sprint with their torso raised, but usually only manage this running style a few meters.

In contrast to almost all other reptiles, which prefer body temperatures between 25 and 40 ° C, bridge lizards live in much cooler conditions. The information on the preferred body temperature deviates significantly from one another in the literature: Robert Mertens specified the preferred temperature as 10.6 ° C, in " Grzimek's animal life " it is 12 ° C, other sources speak of 17 to 20 ° C. Apparently they only become lethargic at 7 ° C. The lower temperature corresponds to a slow metabolism: bridge lizards grow very slowly, they can reach a great age (see below).


Bridge lizards feed primarily on invertebrates , mostly insects (especially beetles and grasshoppers ), spiders and snails as well as earthworms . According to local residents, the Weta species Deinacrida rugosa is the preferred prey of the bridge lizards. They do not actively pursue these, but often wait at the entrance to their cave until a Weta comes by. A rare diet for bridge lizards is seabirds - see below for more information .

Juvenile Sphenodon punctatus in the Southland Museum in Invercargill


Henry, the oldest captive bridge lizard (2009) at 111 years old, in the Southland Museum in Invercargill

Mating occurs during the southern summer from January to March, with males unlike females being ready to mate each year. The 25 square meter territories of the males with a dwelling cave in the center are only defended during the mating season. If a male intrudes into another's territory, it will be attacked. This can lead to injuries, as shown by numerous scars on older males.

The actual courtship of the female begins when one intrudes into the male's territory. The male circles around the female with stiff legs. Since male bridge lizards do not have an elongated genital organ, they press their cloaca against that of the female. Copulation takes about an hour. After about nine months, the female bridge lizards lay a clutch of up to 15 eggs, which are blunt at the ends, parchment-shelled, three centimeters long and four to six grams heavy, in a self-dug burrow. The breeding cave is often hundreds of meters away from the female's dwelling cave; they then spend days or weeks in the brood cavity. After padding the nest with grass and earth and closing the cave with earth, the females, unlike many other reptiles, show a kind of brood care: They keep watch on their nest regularly, sometimes every night, to prevent others Females lay their eggs in the nest. In New Zealand, the approximately ten centimeters long and five grams heavy young animals hatch 13 to 15 months after they have laid their eggs; this longest known breeding season for reptiles shows that the seedlings go through a hibernation period in the colder New Zealand climate. Unlike the adults , the young animals are diurnal in order not to be eaten by large conspecifics. After a year they inhabit the residential colonies of the adults and resemble them in their way of life. Females do not lay eggs every year; Not least because of this, a high individual age is necessary to preserve the species. According to highly controversial information, bridge lizards can reach an age of up to 150 years. In 2009, the oldest captive specimen was 111 years old.

One is well informed about the development of the eggs under human supervision through the protection campaign of the Victoria University in Wellington . Eggs collected in November from " The Brothers " island are artificially incubated at temperatures of 18 to 23 degrees, which significantly increases the hatching rate. Since the young hatch there after only six months in May, it can be concluded that the nests in the wild are exposed to lower temperatures and greater fluctuations.

Apparently the gender distribution in bridge lizards is directly influenced by the breeding temperature. In Sphenodon punctatus only females hatched at a constant incubation temperature of 18 ° C, 91% females at 20 ° C, but only 23% at 22 ° C.

Adult Sphenodon punctatus on rock

Coexistence with sea birds

A notable aspect of the biology and ecology of the bridge lizards is their coexistence with sea birds. One assumption is that they lived there in an almost symbiotic relationship, peacefully and cave-sharing. However, the benefits for the reptile outweigh the above: The bird's droppings and the soil form the food basis for various invertebrates, which serve as food for the bridge lizard. This thesis has recently been increasingly called into question, as there are many indications of a relationship that is only useful for the bridge lizard and harmful for the seabird. Chicks without heads that have been attacked have repeatedly been found in caves where bridge lizards lived. Since no rats or similar animals live in the region of these finds, the bridge lizard is the only animal that is able to kill the chicks. Bridge lizards are also likely to trample on clutches. When observed, the smaller penguin shearwaters ( Pelecanoides urinatrix ) always fled their caves when bridge lizards tried to penetrate them. Petrels of considerable size such as Puffinus griseus drive bridge lizards out of their burrows and are usually successful in doing so. If bridge lizards lived in the caves of sea birds, then the cave had almost always been left by the bird.


The former distribution of the bridge lizards included the New Zealand North Island.

The habitats of the bridge lizards are characterized by a rather harsh climate, strong grass cover and little tree growth.

There are residual stocks on some of the islands off the North Island.
Points: Sphenodon punctatus
squares: "Sphenodon guentheri"

Currently, bridge lizards only live on about 30 small New Zealand islands, which are located in the Cook Strait and between the Bay of Plenty and the Bay of Islands along the north-west coast of the northern main island.

They used to live on the northern main island , a former occurrence on the south island is disputed.

Stock situation

The bridge lizards were severely decimated by humans, especially by goats , cats , dogs , pigs , rats and mice that they introduced . The genus Sphenodon now only inhabits 0.1% of the area originally inhabited by it. The species Sphenodon diversum is only known from bone finds; no specimen of the subspecies S. punctatus reischeki has been seen since 1978. Only 300 specimens of the population formerly listed as S. guentheri are now alive, of S. punctatus around 50,000.


Internal system

For a time, a population on some small islands in the Cook Strait was placed in its own species Sphenodon guentheri . In the meantime, molecular biology studies have shown that the genetic differences, although they exist, are not great enough to justify the separation into two species; therefore Sphenodon guentheri was synonymous with Sphenodon punctatus .

Sphenodon diversum was described by William Colenso in 1885 on the basis of a single, incomplete and not fossilized skeleton that had been recovered from a quarry . Living specimens have not been found since then.

Tribal history

Homoeosaurus maximiliani from the Solnhofen limestone (Upper Jurassic), exhibited in the Museum of Natural History (Berlin) .

Bridge lizards are often referred to as "living fossils". In fact, representatives from the closer relationship of the bridge lizards (Sphenodontia), which presumably looked quite similar to them, have already been identified from the Ladinian (Upper Middle Triassic ) around 240 million years ago.

Sphenodontier were widespread in the Upper Triassic and Jurassic world, however, were from the Early Cretaceous increasingly "modern" reptiles, especially the Schuppenkriechtieren (Squamata), pushed back and could only hold on the isolated islands of New Zealand today. The reason for the initial dominance of the Sphenodontier and the sudden upswing of the Squamats is unclear, because both lines of development are sister groups and therefore of the same age.

The Sphenodontia can be divided into two families : Sphenodontidae and Pleurosauridae. The sphenodontids are terrestrial forms. The recent bridge lizards belong to this family and the oldest known Sphenodontier in the late Middle Triassic should also have belonged to this family. One of the youngest representatives of the heyday of the Sphenodontier is the relatively well-known genus Homoeosaurus (" false bridge lizards ") from the Upper Jurassic , a group that hardly differed from today's bridge lizards. The sphenodontids have been morphologically extremely conservative for at least 150 million years .

The representatives of the pleurosaurids, however, went over to the aquatic way of life. One of these forms is Pleurosaurus goldfussi . Fossils of this up to 1.5 meter long reptile, whose caudal spine is twice as long as the rest of the body, were found, as well as the remains of the Sphenodontid Homoeosaurus maximiliani , in the Upper Jurassic plate limestone of Solnhofen (Franconian Alb) and the plate limestone of Canjuers ( Département Var , France) found. However, the fossil record of the pleurosaurids, in contrast to that of the sphenodontids, is limited to the Jura.


Since the animals enjoy the strictest protection by the New Zealand government, currently (as of March 2011) only about 140 bridge lizards are kept in ten institutions, of which 43 are outside New Zealand. In Germany they are only shown in the aquarium of the Berlin Zoo . Ten specimens live there in a large, cooled terrarium.

In the past, most of the animals were kept too warm in ignorance of the special temperature requirements of bridge lizards. One of the first bridge lizards kept in Europe or worldwide was present in the zoological institute of Uppsala University , where it arrived in autumn 1908. She lived there until the summer of 1931 in a 75 × 40 × 40 cm wooden box under a desk, the entire box was only lined with wood wool and contained a water container. The temperatures fluctuated between 16 and 20 ° C. In 1931 it came in a wooden box measuring 190 × 75 × 30 cm, which was furnished in a structured manner. There she showed greater activity. She was fed a few strips of meat or 15 to 20 earthworms every week.

The animal in fiction

In John Green's novel Sleep Well, Her Nasty Thoughts, a man bequeaths all his fortune to his tuatara in his will.


  • Wolfgang Böhme: Sphenodontida, beak heads, bridge lizards. In: Wilfried Westheide and Reinhard Rieger (eds.): Vertebrate or skull animals. Fischer, Stuttgart 2004, ISBN 3-8274-0900-4 ( Special Zoology. Part 2), pp. 354-357
  • K. Klemmer: The bridge lizard. In: Bernhard Grzimek (Ed.): Kriechtiere. Bechtermünz, Augsburg 2000, ISBN 3-8289-1603-1 ( Grzimeks Tierleben. Volume 6), pp. 148–151 (unchanged reprint of the dtv edition from 1979/80)
  • Manfred Rogner: bridge lizards, beak-headed lizards (order Rynchocephalia). In: Manfred Rogner: Monitor lizards, skinks and other lizards as well as bridge lizards and crocodiles. Ulmer, Stuttgart 1994, ISBN 3-8001-7253-4 ( Echsen. Volume 2), pp. 220-223.
  • Robert L. Carroll: Paleontology and Evolution of the Vertebrates. Thieme, Stuttgart 1993, ISBN 3-13-774401-6 .

Web links

Commons : Bridge Lizard  - collection of images, videos and audio files


  1. Bradford Haami: Ngārara - reptiles. In: Te ara - The encyclopedia of New Zealand. Ministry for Culture & Heritage (New Zealand), September 22, 2012, accessed October 6, 2013 .
  2. a b c According to W. Böhme (2004), p. 354.
  3. The chewing and sawing lizard. In: Deutschlandfunk . Retrieved July 10, 2012 .
  4. ^ Based on a report by Robert Mertens, quoted in Grzimek (2000), p. 150
  5. According to Grzimek (2000), p. 149
  6. According to Rogner (1994), p. 222; and W. Böhme (2004), p. 357
  7. According to W. Böhme (2004), p. 357
  8. ↑ Based on a report by Eugen Schuhmacher, quoted in Grzimek (2000), pp. 150–151
  9. Echse becomes a father at the age of 111. Frankfurter Rundschau, January 26, 2009, accessed on October 6, 2013 .
  10. According to Rogner (1994), p. 221
  11. According to
  12. Buller, WL 1877. Notes on the tuatara lizard ( Sphenodon punctatum ), with a description of a supposed new species. Transactions and Proceedings of the New Zealand Institute 9: 317-325
  13. Hay, Jennifer M .; Stephen D. Sarre, David M. Lambert, Fred W. Allendorf and Charles H. Daugherty. Genetic diversity and taxonomy: a reassessment of species designation in tuatara (Sphenodon: Reptilia). In: Conservation Genetics. 11, No. 3 2010: pp. 1063-1081
  14. W. Colenso: Notes on the Bones of a Species of Sphenodon apparently distinct from the Species already known. In: Transactions and Proceedings of the Royal Society of New Zealand. 18, 1885, pp. 118–128 ( PDF 525 kB)
  15. Marc EH Jones, Cajsa Lisa Anderson, Christy A. Hipsley, Johannes Müller, Susan E. Evans, Rainer R. Schoch: Integration of molecules and new fossils supports a Triassic origin for Lepidosauria (lizards, snakes, and tuatara). BMC Evolutionary Biology. Vol. 13, No. 1, 2013, Item No. 208, doi : 10.1186 / 1471-2148-13-208 (Open Access)
  16. ^ Günter Viohl: The Solnhofener Plattenkalke, upper Jura. In: Dieter Meischner (Ed.): European fossil deposits. Springer, Berlin · Heidelberg 2000, pp. 143-150, doi : 10.1007 / 978-3-642-57198-5_15
  17. Karin Peyer, Sylvain Charbonnier, Ronan Allain, Émilie Läng, Renaud Vacant: A new look at the Late Jurassic Canjuers conservation deposit (Tithonian, Var, France). Comptes Rendus Palevol. Vol. 13, No. 5, 2014, pp. 403-420, doi : 10.1016 / j.crpv.2014.01.007 (alternative full-text access : ResearchGate )
  18. Zoo Berlin website (accessed March 24, 2011)
  19. According to Cyren (1934), cited in Rogner (1994), p. 223