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Ancestor: Spiny Lizard

Size: Varies greatly. Smallest species is around 25cm long, while the largest can grow up to and in rare cases beyond 2m long.

Dietary Needs: As a genus they have a very variable diet. On one end of the spectrum there are those who consume only invertebrates and meat, often scavenged carcasses. In the middle there are omnivorous meat scavengers and foragers of fruit and soft vegetation that occasionally hunt small animals. At the other end of the spectrum there are near-herbivores, usually much larger than the other species, that occasionally eat meat and invertebrates as a supplement to a diet of mainly soft vegetation and fruit, on the coast seaweed also. One small outlier is a nectarivore more closely related to some of the omnivorous species and will occasionally eat fruit and invertebrates to boost their nutrition.

Regardless of the adult diet, nearly all newborn offspring sustain themselves by hunting small invertebrates while they themselves are still small.

Life Cycle: Like their ancestors females are typically larger and heavier, and are selective of males who must impress a female to get the chance to mate. Because of this males tend to have brighter colours and sometimes more wild and cumbersome scale growths. If he can survive and remain energetic in spite of such flashiness, then there's a good chance he may be genetically very fit.

Males compete with each other but usually this is without any physical contact. Sizing up and flashing colour (by dramatically pivoting to change the visibility of the sail) is usually enough to cause one of the males to lose their nerve and concede to the other.  This may vary by species, with some being more physically combative than others.

Small shadowback species also have an interesting sexual-selection based action that is sometimes used as a means of intimidating threats. While they're in their back arc threatened pose, they might bound forward suddenly, hindlegs leaving the ground before the forelegs land. It's similar to the hop of a frog. It's usually only used once as a sudden, unpredictable action to startle a threat when backed into a corner, but during sexual attraction and competition they will chain repeated bounds often until exhausted to demonstrate their stamina, or rivals will bound towards each other until one loses it's nerve.

Young are born live but very small, no bigger than they would be if they hatched from an egg, and reliant on a store of yolk in their stomachs after being born to tide them over until they get into the flow of hunting for food. They benefit from their mother's longer-lasting maternal instinct. They give a faint odour that their mother recognises as her own and she will protect those that have the scent. This way she doesn't accidentally waste energy watching out for offspring that are not hers, and she can also drive out those that are not hers so that they don't benefit from the resources in her territory. Although she doesn't get to know each one, she will defend them for as long as they remain in her territory, or until mature.

Other: Small shadowbacks differ from giant shadowbacks. Giant shadowbacks (between around 1.5 m and 2 m full grown) have a straight spine with poor flexibility. The spine hangs between the more supportive shoulders (which are more developed, the attachment for the humerus to the scapula and coracoid occurs further beneath the body. The sternum is wider and has a more pronounced ridge) and pelvis (the sacral ribs have thickened, are longer such that they push down on the base of the pelvis when weight is supported, and very flush with the pelvis fixed as one unit by strong ligaments, with the only wiggle room being to help cope with physical stresses. Sacral ribs have also fused to the vertebrae and thickened at the point of fusion.). The spine heavily interlocks but is not very well articulated, instead acting as a strong bridge that has very limited flexibility and is surrounded by walls and layers of complex musculature.

Small shadowbacks have a different internal morphology. They have a far more flexible spine. It interlocks differently with differentiation between different sections of the spine, especially either side of the "hinge" where the tightest arcing occurs during an arc display pose. The vertebrae can move slightly more freely from each other than in the stiff-backed giants. Their spine can arc upwards and does not need to be supported. The pelvis is not fused to anything, though the sacral ribs still lock with it. The arch-back action makes the lizard look bigger, but it can also be used to tilt to or from the sun by pushing one side up higher than the other. It is used in sexual selection, both as a mate attractor and as a means of non-violently competing with rivals. It is also used to drive off smaller threats of other species and also to drive out rivals that might compete for the local food. A lot of the smaller shadowback's advantages are only achievable due to being small.

Giant shadowbacks have experienced rapid evolution of a larger size. They have compromised speed and agility for the ability to stand up to predators and become too large to hunt once fully mature. The armour and spines were a logical next step in this arrangement. The spines are modified tough, dense scales and are nutritionally demanding, which is helped by having a very experimental attitude towards food to intake a wide range of nutrients. They will sometimes crave small delicate bones, swallow mineral rocks, raid for bird eggs or eggshells, and select specific plants when they require the supplementary nutrition. Most giant shadowbacks are omnivorous leaning towards herbivorous, but the few carnivorous ones have strong stomach acid to dissolve a considerable volume of hard material such as some scales and bones, very small teeth, and even sometimes claws.

The shadows cast by their scales helps them manage their temperature. Facing the sun results in less temperature change, while becoming perpendicular to the sun creates a well defined shaded and lit side, which they can alternate as needed. Blood flow in the living tissue beneath the scales can be increased or decreased on whichever side necessary. The scales can act as a heatsink in total shade or in windy conditions due to their high surface area and sometimes also greater thermoconductivity than flesh, especially in species that minerally enrich their scales as they grow. When too cold they bask in the sun or wait for warmer conditions to resume activity. Large shadowbacks can retain enough body heat to stay active a small amount of time into the night where nights are cold. Digestion can also offer some warmth by which to stay somewhat active. If the night doesn't get cold they can stay active all night.