Final answer:
Plesiadapiforms are more primitive than euprimates and lack characteristics such as a grooming claw, a toothcomb, and adaptations like a larger brain, stereoscopic vision, and an upright posture.
Step-by-step explanation:
Plesiadapiforms differ from euprimates in that they are an earlier, more primitive group and do not possess some of the typical primate characteristics. Plesiadapiforms lack the nail on the second toe known as a grooming claw and the specialized teeth called a toothcomb that are found in strepsirrhines, a suborder of euprimates that includes lemurs and lorises. Additionally, plesiadapiforms do not exhibit the larger brain size, stereoscopic vision, and the trend toward an upright body posture that characterize the euprimates, which encompass groups like monkeys, apes, and humans.