Euarchontoglires is a superorder of placental mammals grouped together by molecular data that shows that they share a common ancestor. They are split into the clades Glires and Euarchonta. Glires are the rabbits and hares, and the rodents, including mice and rats. The Euarchonta contain tree shrews, flying lemurs, and primates, including you!
Tree shrews (Order Scandentia) are small long-nosed arboreal mammals from South-East Asia that look like squirrels. Scandentia is one of the most basal Euarchontoglire clades but its exact phylogenetic position has not been resolved.
Glires are grouped based on molecular data and shared morphological features. They have lost many of their mammalian teeth and possess rootless teeth that grow continually as they are ground down by gnawing. Rabbits, hares and the pika are in the Order Lagomorpha (from the Greek “lagos” meaning hare and “morpha” meaning form). Lagomorphs, unlike rodents, are able to make side to side chewing movements. They have a second peg-like upper incisor behind the primary incisor and lack canine teeth. Rodentia (Order Rodentia) is the largest group of mammals on the planet, both in the number of species (2,021) and in population size. They are characterized by having single pairs of continuously growing incisors covered in enamel at the front of each jaw and no canine teeth. The jaw can move up and down and from front to back but not sideways like the lagomorphs. The upper lip is generally split and in some animals forms labia that can expand into cheek pouches used to transport food.
The colugos, or flying lemurs, (Order Dermoptera) are gliding and climbing mammals the size of a domestic cat. Their limbs, body, neck and tail are connected to a large thick membrane called a patagium which enables them to glide between trees.
Natural selection imposed by the demands of living in the trees has shaped much of the morphology of living primates (Order Primates). Primates have highly flexible shoulder joints, thought to have made it possible to swing from tree to tree, and nails (rather than claws) with dextrous hands allowing them to grip branches and manipulate food. Primate eyes are close together on the front of the face allowing good 3D vision, an obvious advantage when leaping through the forest.
Primates are divided into two suborders. Suborder Strepsirrhines include Madagascan lemurs and lorises that live in tropical Africa and southern Asia. Many of these animals are active at night or in low light and have adaptations such as a reflective layer on their large eyes and a heightened sense of smell. Suborder Haplorhines include tarsiers, monkeys, apes and humans. Most haplorhines are active during the day with the exception of tarsiers and owl monkeys, and accordingly most have eyes specifically adapted to increase visual acuity in a daylight setting. All haplorhines have evolved the ability to move their upper lip independently, allowing social communication via facial expressions. This important behavioural adaptation – complex sociality – is thought to be linked to the evolution of larger brain sizes.