Explain the purpose for the simile "New class, who gawked at her like she was an old pile of dinosaur bones."

This simile directly relates to Tally's age. She is growing up, and the Uglies she leaves behind are younger.... not ready to become "pretties". Tally is "coming of age".

Tomorrow, when the operation was all over, her parents would be waiting outside the hospital, along with Peris and her other older friends. That was the tradition. But it seemed strange that there was no one to see her off on this end. No one said good-bye except a few uglies passing by. They looked so young to her now, especially the justarrived new class, who gawked at her like she was an old pile of dinosaur bones. She’d always loved being independent, but now Tally felt like the last littlie to be picked up from school, abandoned and alone. September was a crappy month to be born.