Sentisaurs are a family of ground-dwelling lizards that descend from the Horned Gecko of the Middle Muricene. Their mountain-dwelling ancestors evolved to survive in harsh conditions, weathering both the dry tropical heat of once common on the Gecko Isles and then the bitter cold that preceded the Arthrocene. Surviving on little water and able to take advantage of nearly any food source, this clade entered the current age poised to take over the new landmass. Though they remained small all the way through the Ice Age, some have taken the opportunity to grow larger than any other terrestrial reptile. Others are more modest in size but possess new anatomical adaptations, giving them an edge over other geckos and allowing them to hold their own against avian and mammalian competitors. In particular, Sentisaurs have the most derived integument on the planet, with a wide array of keratinous spikes, plates, and bony osteoderms protecting them from danger.

A basic form of this armor was present in Sentisaurus itself, which had sideways-projecting spines on its head. The skin of its back and legs was also thick, wrinkled, and leathery to help it resist cuts and slashes. The Knifetail Gecko (Persecauda), the most basal member of this family, has a scaled-up version of this strategy. At half a meter long, it rarely needs to worry about being swallowed whole and has thus lost the horizontal facial horns. Instead, it has clusters of spikes on its shoulders and the base of its tail. The latter encourages predators to attack the exposed upper surface of the tail proper, which detaches quite easily. This distraction allows the knifetail to escape, but the still-moving tail still has a trick up its sleeve. Its underside is lined with a row of serrated protrusions that, if the carnivore isn't careful, can easily tear into its flesh as it wriggles. This scenario is common enough that over 90% of individuals end up tailless before their second birthday. Over the course of a few months, the gecko can partially regenerate a replacement, though the new tail generally ends up short, deformed, and far less effective as a weapon than the original. Instead, mature knifetails grow a horn on their nose that becomes their primary defense mechanism once they reach full size. 

One group of Sentisaurs, the Buccinodontinae, has become even more reliant on these keratin-based spines. This subfamily has specialized horns with a bony core, each of which connects to a small muscle embedded in the skin that allows the structure to move, often with surprising power. Such is the case with the fifteen-centimeter Sabergeck (Buccinodon), a genus that has secondarily returned to a tree-dwelling lifestyle and feeds on seeds, eggs, woodlice, and other small hard-shelled items. It has a pair of these mobile spikes that point downward from its upper jaw. Conical and slightly recurved in shape, these function as a set of strong, independently-moveable "teeth". The sabergeck uses its horn-teeth (which give it and its subfamily their name) to crack open its tough food. They grow continuously, offsetting the daily wear and tear of feeding. When facing a rival sabregeck or a hungry larger animal, they also serve as deadly weapons, able to puncture and tear through flesh. They can even break the bones of less heavily-armored lizards, including their main predators, juvenile Varanogekkonines. 

While Buccinodon has muscle-powered horns only on its face, with the rest of its body lined with simple, basal spines, another member of its subfamily is covered head to tail in large, mobile stabbing implements. The Pitfall Lizard (Hastodorsus) lives atop the same mountains where the family first evolved. Here, in a landscape riddled with rocks, pits, and small crevices, the ancestors of this genus first used their dermal spikes to wedge themselves into these hiding spots, rendering themselves nearly impossible to pry from the safety of their dens. Pitfall lizards still live this way, with dozens of long, sharp horns keeping them secure wherever they choose to sleep, but they have also adapted to use this technique in a more aggressive way. A hungry Hastodorsus will find a suitable depression on an otherwise flat stretch of loose soil and dig down until it is mostly concealed, leaving only its eyes, nose, and the tips of its spines aboveground. It can wait like this for weeks, slowing its metabolism so that it rarely needs to eat. If it's chosen a good area to rest, some larger animal will come walking by sooner or later. When the pitfall lizard's victim steps onto what appears to be another unremarkable patch of dirt, it gets a vicious surprise as the gecko inflicts twenty or more stab wounds directly to its foot and leg. This usually trips the bigger creature, leaving a short window of a few seconds when the Hastodorsus can feed freely, taking huge bites from any bit of exposed skin. It rarely does enough damage to kill its prey, though, and usually has to flee immediately after eating to avoid being killed in retailiation.

The other major taxon within Sentisauridae is called the Polyclypeinae, which has opted for thick, flat plates as its primary form of armor. Polyclypeines generally can't cause as much damage as Buccinodontines of a similar size, but they can weather attacks by even the largest predators on Aglirium. However, they still prefer to keep themselves out of harm's way whenever possible. The Bogwedge (Triclypeodorsus), for instance, lives in the lowland swamps found along several regions of the subcontinent's east and west coasts. It eats mostly aquatic vegetation, though it doesn't turn down carrion when the opportunity arises. A slow but efficient swimmer, its wide torso houses massive lungs that let it remain underwater for up to twenty minutes without discomfort. Most of the time, this is enough to keep it safe from carnivores, as it can conceal itself beneath the murky waters and remain undetected. When it's in trouble, three triangles of keratin - one on each shoulder and another covering the hips and base of the tail - keep its vital organs safe from the teeth, claws, and beaks of other animals. 

The largest Sentisaur is the Armorback Gecko (Polyclypeus), a tank-like lizard that lives deep in the island's jungles. Its body is studded with three rows of pentagonal plates, interspersed with smaller lumps of bone embedded deeper in its skin. Four much larger osteoderms form a ridge along its face that it uses in intraspecific combat. Measuring two meters from its snout to the end of its stubby, non-detachable tail, it isn't as long as some species of monitor geckos and thalassaurs, but its heavy armor, robust build, and massive gut make it far heavier, up to 250 kilos in older individuals. It eats a combination of soft vegetation like sweetstalks and rougher twigs, roots, and large seeds. All this plant matter ends up fermenting in its stomach, after which it can extract far more calories than it could otherwise, allowing it to reach its massive size. As Aglirium's largest herbivore, it's a keystone species in the forests it calls home. When it feeds, it clears the ground of debris, which allows new generations of plants to sprout, and its droppings fertilize the young seedlings. Janitor bugs are also happy to eat its waste, and thousands of their fellow Dermestemimids emerge whenever an armorback dies, feasting on its carcass for months.