Skrimïr (Skreem-yeer) or Skrim singular are what became of a variety of arboreal small rodents and mammals, most notably the variety of squirrels all over the Americas at the time of the Pulse and are a pretty common sorta critter that you can find in various spaces throughout the DragonScape.
In basics
Skrimïr are "snakes" (not exactly) that vary in length from 2-5 feet in that weigh between 20-50lbs in . They are herbivores and most notably eat leaves and branches of a variety of tree species across the DragonScape. Their most odd feature is their sphincter like mouths located on the bottom of their head that aid in enveloping and chewing off branches of trees. They move by slithering on the ground But while in trees they utilize a set of six claw like "legs" that grip into the bark and allow them to hang onto the trees theyre feeding in They are faster than anticipated (usually scurrying at 3-15mph but are, at least compared to a lot of critters very very slow. Though they are known to use that mouth in a quick and horrifying manner if threatened, they have been known to latch onto and gnaw off limbs of predators or would be hunters
Variants
Like all other life, a "breed" of skrim depends on where their eggs were laid and there are more or less 4 common breeds that exist in the dragonscape that follow similar naming conventions (though different features sometimes) of drekir and all other life

Fijal or Temperate Skrimïr are the most common in North and South America (though tropical gives SA a stiff equal). They are of a mediumish size and often boast brown or green scales with simple oval patterns along the back. Most Skrimïrfijal feed on pine trees though in South America decidious trees are more on the diet.

Pura or Arid Skrimïr are more known for being the small breed of Skrimïr, feeding more on species of sagebrush, yucca, and other desert plants of a region. They are very waste efficient critters and are great at preserving water and are spiky and spiny to ward off larger wyrms that exist in many deserts.

Juln or Tropical Skrimïr are the largest breed and, while found in the tropical rainforests of the Amazon, are most common in the Swamps, Marshlands, Rivers and Lake regions of tropical parts of the world. As they are more amphibian like (even boasting skin instead of scales) they are capable of water travel and are known for swimming offshores into the open seas for more grazing of aquatic plants.
They are also poisonous in a similar manner to a dart frog which helps with some predators (though not all)

Kal or Arctic Skrimïr are, like their temperate cousins, of a medium size and mostly boast warm blood and a thick coat of fur. Unlike most breeds of skrimïr if the weather gets cold they continue on as they had in the past, mostly grazing on the evergreens found in most arctic regions. They do also see their fur change from white to brown throughout the year. They are also known to climb high up on branches to evade large land predators
Interactions with drekir, humans, and sivilão
Drekir in a ton of regions regularly hunt skrimïr. Most often with either ranged weapons that can knock em out of the trees like slingshots, slings, and throwing sticks. There are also hunting tactics that feature long simple spears to shank them in the tree or to hook them and drag them out of the tree where they can be finished off. Skrimïr are a pretty reliable diet for drekir who know how to not get their arms bitten off (which is easier than one could imagine, a cornered skrim is fast snapping)

Human colonies tend to not interact with them much, but they are also hunted usually to feed the drekified members of an outpost to conserve on limited human approved rations. Though they were often the first subject of major study by biologists in the DragonScape.

The Sivilão tend to also not interact much with life outside of their Õfuthar unless its required for their survival. Though they tend to run into more problems as they hunt them less and are less equipped to deal with them when compared to the tribal drekir who have often hunted them for decades straight. But nothing is really stopping an orm from plucking them out of the tree and quickly slamming them into a rock for a quick and safe kill
I should note that Skrimïr pelts are also pretty thick and are quite valuable for tanning into clothing, bags, pouches, armor or other useful things. a lot of the long pelts you see often come from skrimïr (though to be fair there are a LOT of serpentine critters)