The full version of my essay on tuataras+relatives.

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Sphenodontida is an ancient group of lizard-like reptiles that enjoyed great
success during the Mesozoic, at least until the late Cretaceous. The
sphenodonts' kin, rhynchocephalians, or "beak heads", spread across the globe,
both in Laurasia and Gondwana. Fossil rhynchocephalians are poorly-studied, but
it seems they radiated into a number of forms, including the lizard-like types
that are now their only legacy.

Within all sauropsids, sphenodontians are among the most conservative ones,
probably resembling the earliest diapsids or even the last common ancestor
between these and testudines. They resemble lizards in their outward form, but
their inner anatomy is quite strange. Sphenodonts lack the kinetic, flexible
jaws of lizards, building their skulls, instead, out of resilient plates of
bone. Their teeth are not rooted in the jaw as in lizards and mammals, but
actually fused into the mandible. Some features of the skull resemble those of
crocodiles, and historically they have been classified as archosaurs, though
nowdays its usually agreed they represent a linage related to modern squamates;
they also have quite primitive hearts, they lack an eardrum/hole, and males are
the only non-avian tetrapods to lack a penis. Although modern tuataras have
remained fairly conservative since the Mesozoic, they are, ironically, the
sauropsids with the fastest known evolutionary rate, and its possible that most
of their modern relatives have evolved from tuatara-like forms during the
Cenozoic rather than being relics from the Mesozoic.

All modern sphenodontians are restricted to Australasia, but they are by no
means a relic clade as on HE; like monotremates, they are well more diverse than
HE's forms, and occur both on the mainland Australia as well on islands.

*Sphenodontidae*

The classical tuataras, these animals are a common presence on Australia, New
Zealand and Tasmania. They occupy the niches taken by large skinks on HE, and as
a whole they aren't very different from RL tuataras. In this essay, this clade
is used to describe p-Sphenodon; however, genetic studies and the fossil record
show that most modern sphenodontians evolved from tuatara like forms in the
Oligo/Miocene. If so, this clade is only valid if it includes other modern
sphenodontians as well; otherwise, its just p-Sphenodon.

*Blue Tongued Tuatara (p-Sphenodon morrisi)*

[picture by Tim Morris]

Australia is the land of sphenodontians; most of the clade's species are to be
found on Down Under and its daughters, Tasmania and the other coastoal islands.
The continent is covered mostly by scrub and savanna, and lepidosaurs prosper
here. One of the most unique is the blue tongued tuatara, a denizen that took
the niche occupied by blue tongued skinks on HE; its particularly large size
(compared to their HE analogues), as well as very wide distribution (they occur
over most of Australia, from the arid scrub to the forest undergrowth) means
that this single species took over a niche occupied by several on HE, although
it has been suggested that the subspecies (S. morrisi morrisi, S. morrisi
deserti, S. morrisi tasmanicus and S. morrisi minor) of this animal might
represent species of their own. Like all tuataras this is a small generalist,
preying on invertebrates, small lizards and mammals and even young of their own
species.

Uniquely among tuataras (but not among sphenodontians as a whole; see below),
this one isn't nocturnal as an adult, though it isn't fully diurnal either,
being a crepuscular animal. As a result, it is more exposed to predators, and
thus it has a spectacled pattern of green and brown tones on its skin, using
camouflage to hide. Show it fail it uses another strategy: as its name implies,
it shows the bright blue tongue. It may also bite should that fail. The blue
tongue also serves as a disply device by males; they have a brighter tongue than
the females, and use it to attract mates and scare off rivals. Like all
sphenodontians it is oviparous, laying up to 20 eggs which are protected by the
female.

*Coppery Tuatara (p-Sphenodon keratis)*

[image by David Namen]

A typical tuatara from southern Australia and Tasmania, this animal is adapted
to dry conditions, storing fat on its tail. Its name comes from its colouration,
which is in a light brown tone akin to that of copper. Growing as long as a
meter, it is the biggest living tuatara, and lives as much as 100 (not that its
unusual among this long lived clade).

*Fung-Tongue (p-Sphenodon luminosa)*

[information provided in the Waitomo cave essay]

*Rhynchoguanidae*

Australia is fairly poor in terms of land turtles. In both timelines there are
no tortoises and only meiolanids occured, the later taking large, ankylosaurine
niches, not typical tortoise ones. On HE, no group of lepidosaur seems to have
taken a step to occupy a small terrestrial herbivore/omnivore niche on
Australia, but on Spec a linage of sphenodontians, the beakguanas, did. The
earliest beakguanas are known from Riversleigh from the Miocene, which suggests
that they are a post-Oligocene experiment, as the boundary between those two
periods is famous for being a minor mass extinction, which totally redesigned
tetrapod life on Australasia. The surviving meiolanids became ankylosaur like
animals, while the beakguanas evolved to take over the smaller meiolanid niches.

As the name implies, beakguanas can be distinguished from other sphenodontians
by their rostrums, which now lack teeth (if sphenodontian teeth can be called
"teeth" at all) and have their tips covered in keratin and hooked, efficiently
forming a beak. They are obviously quite herbivorous, feeding on any edible
plant matter and even plants that are too toxic for mammals or dinosaurs to
consume. Though they still apreciate insects and carcasses. These animals have
been compared to the long gone rhynchosaurs, a linage of reptiles once believed
to had been related to beakguanas, though now classified as archosauromorphs,
and like them they where slow herbivores with beaks (well, actually long, fused,
keratin covered teeth, but its the same thing). Also like their extinct
counterparts, beakguanas are the most diverse living sphenodontians, with at
least 10 known species.

*Greater Beakguana (Rhynchoguana magnus)*

[pic by Tim Morris]

The biggest living beakguana is an animal that rivals with the terrestrial
island iguana from HE's Galapagos in size. Grey in colour, it occurs in the
australian outback, having crepuscular tendencies. It uses its hooked jaws to
tear off tough plant matter, which is later smashed by the gastrolits in its gut
and digested by a diverse stomachal flora, as in all beakguanas. Its large size
and strength means few cedunosaurs and wolfcrocs dare to attack it, as its jaws
can break a leg of one of those animals, though full grown carnocursorids and
rhynchoraptors might pose a threat, thus they have osteoderms on their skin,
though they serve more to help it in camouflage than to actually be used as an
armour, so loose and small as they are. They breed in the rain seasons, burrying
their eggs on the sand; newborns are fully carnivorous, but they slowly become
herbivores as they grow, eating the adult's faeces to obtain the gut flora.

*Lesser Sailback Beakguana (Neoedaphosaurus spinoptera)*

[picture by Timothy Morris]

Occuring in the same area as greater beakguanas, this one is smaller and has a
bright yellow colouration. To avoid competion with their bigger cousins they are
much pickier eaters, feeding exclusively on the most toxic or fibrous plants,
that few other vertebrates can eat. In order to cope with this extreme diet they
spend hours imobile, trying to digest the meal. This leaves them very vulnerable
to predators, and because their spike like osteoderms aren't enough defense they
developed an unique way to scare off predators: as their name implies, they
developed a dorsal fin, making them resemble slightly the ancient pelycosaurs.

Said fin isn't supported by dorsal bones, but by ossified cartiladge ridges, and
is usually retracted on the back. When threatned, it rises, and because it
contains chromatophores akin to those of chameleons it easily develops a large,
eye like spot, which confuses the predators. The sail also has a
thermoregulating function, as the pelycosaur sails likely had.

A similar species is the greater beakguana (Neoedaphosaurus giganteus), which
rivals the greater beakguana in weight, though not in length.

*Hawkin's Beakguana (Demirostrum atheos)*

[image by Timothy Morris]

A denizen from New Caledonia, this beakguana is notable for the presence of a
small keratinous horn on the snout and for the lack of a beak in the lower jaw.
Indeed *Demirostrum* is the most basal living beakguana genus, reduced to three
living modern species on Pacific islands. A medium sized beakguana, with a
length of one meter, this chubby looking animal avoids competition with the
native terrestrial treeguana rath by being more folivorous, and indeed it has an
unusuallu less extreme diet for a beakguana, not targetting hard or poisonous
plants any more than more edible ones. Its only natural predator are dudus and
predatory birds, and thus they have hardly any osteoderms and only lay four eggs
at a time.

*Borosphenodontidae*

I guess we can use things from Tim's blog:

http://spectim.blogspot.com/2006/05/crackerjack.html

*Neopleurosauridae*

Sphenodontians produced a variety of aquatic forms during the Mesozoic until the
late Cretaceous, when they began declining. Nonetheless, Spec's Australasia has
a few aquatic native sphenodontians, the salalizards (genus *Neopleurosaurus*)
dating from at least the Eocene, these animals seem to have diverged earlier
from than the other modern sphenodontian clades, as recently as the Cretaceous;
some have indeed suggested that, while most modern sphenodontians have diverged
from the tuatara line during the Cenozoic, these aquatic animals might represent
a surviving clade of the older aquatic forms. Because this wasn't supported by
fossil evidence as of yet it can't be confirmed.

Salalizards are quite aquatic animals, spending most of their life on the water
and only return to land to lay their eggs. They are more predominant in the
north, but larger species occur in the south, where the colder climates protect
them from competition with crocodilians.

*Taniwha (Neupleurosaurus novazealandica)*

One of the largest modern salalizards, it reaches the length of one meter and a
half. This grey coloured animal lives on the waterways of Aoteroa, and it looks
like the average salalizard: more adapted to an aquatic listyle, these reptiles
have longer and thinner bodies than terrestrial sphenodontians, as well as
webbed feet (the backlimbs are longer than the front ones) and their nostrils
are positioned in the middle of their snouts their snouts, in a more dorsal
position. Having small, spike like teeth, they prey on aquatic invertebrates and
fish, occasionally taking small mammals and aquatic birds. Swimming like eels,
these animals only come to land in order to bask and to lay their eggs.
Sometimes they occur in salt water, but like most salalizards they are
freshwater animals.