A quick look at two closely related taxa today.
Hapalodectes (IVPP V5235, Fig. 1; Paleocene. China) nests at the base of the clade of primates (lemurs through humans, Fig. 3). Notice the narrow, transverse premaxilla and large canine.
On the other hand
Ptilocercus (Fig. 2; extant, Thailand, the pen-tailed tree shrew) nests at the base of the clade of rodents and rabbits and kin. Notice the large premaxilla (yellow) and small canine (orange). This represents the genesis of gnawing teeth in this clade.
These mouse-sized arboreal taxa
are late survivors of an earlier Middle Jurassic radiation. Both have a complete circumorbital ring, atypical for most mammals.